Inertial borehole survey system

• US 4,454,756 A
• Filed: 11/18/1982
• Issued: 06/19/1984
• Est. Priority Date: 11/18/1982
• Status: Expired due to Fees

• Current Assignee: Wilson Industries LP (Schlumberger NV)
• Original Assignee: Wilson Industries LP (Schlumberger NV)
• Inventors: Howatt, John R., Spiegel, Leo, Walker, Gary E., Masters, Richard M., Sharp, Harper E., Frey, Elmer J.
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US06/442,849
• Time in Patent Office: 579 Days
• Field of Search: 73/151, 73/1 E, 33/304, 33/312, 33/313, 364/422
• US Class Current: 73/152.54
• CPC Class Codes: E21B 47/022 of the borehole, e.g. using geomagnetism

Abstract

A system and method for surveying, with accuracies better than one foot per thousand feet of depth, very deep boreholes having the attendant small diameters, high temperatures and high pressures with very high accuracy. A downhole probe is used having a small diameter, less than about four inches. Three linear type accelerometers and at least two gyros to provide three sensitive axes are fixedly mounted at points spaced along the axis of an elongated, rigid, thermally conductive support member to form an instrument cluster. Signals from these instruments are then processed and transmitted serially over a conductor of a conventional wireline to the surface unit where a surface computer continuously computes and records the current position of the instrument.

Claims

1. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe having a maximum diameter less than about four inches and adapted to be lowered into a wellbore;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) vacuum sleeve means disposed within the tubular pressure vessel for substantially thermally isolating the interior thereof from the pressure vessel;

(3) an inertial cluster assembly including

(a) an elongated, rigid, thermally conductive support member disposed within the vacuum sleeve;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member in heat exchange relationship therewith;

(c) transducer and circuit means for sensing the temperatures of the inertial sensing means, and producing an electrical signal representative of the temperatures thereof;

(d) isothermal phase change material in at least one cylindrical container rigidly and thermally coupled to the support member to absorb heat generated by the inertial sensing means to maintain the inertial sensing means at a temperature within a predetermined narrow range for a period of time greater than that required to complete the well survey;

(e) cluster circuit means associated with the inertial sensing means mounted on the rotating cluster assembly and thermally coupled to the support member;

(4) upper and lower journal means supported in the vacuum sleeve for rotatably supporting the cluster assembly within the vacuum sleeve for rotation about the longitudinal axes of the vacuum sleeve;

(5) first slip ring means including a rotor member mounted to the upper end of the cluster assembly and a stator assembly supported in the vacuum sleeve for establishing a plurality of electrical paths between the interior of the vacuum sleeve above the cluster and the cluster assembly;

(6) second slip ring means including a rotor member mounted on the lower end of the cluster assembly and a stator member supported within the vacuum sleeve for establishing a plurality of electrical paths between the cluster assembly and the interior of the vacuum sleeve below the cluster assembly;

(7) controllable torque means coupled to rotate the cluster assembly including electric motor means for locking the cluster assembly relative to the vacuum sleeve;

(8) rechargeable battery power supply means disposed within the pressure vessel;

(9) upper circuit means disposed within the vacuum sleeve above the cluster assembly, lower circuit means disposed within the vacuum sleeve below the cluster assembly, the upper and lower circuit means being mounted on and thermally coupled to elongated thermally conductive containers substantially filled with an isothermal phase change material for maintaining the circuits within a predetermined narrow temperature range for a period of time longer than a desired survey run, the upper, lower and cluster circuit means including subcircuit means for

(a) producing a digital signal representative of the temperature sensed by the temperature means;

(b) initiating and terminating operation of the inertial sensing means on command;

(c) producing analog signals representative of the inertial measurements of said inertial sensing means and converting the analog signals to digital signals representative of the inertial measurements of each inertial sensing means;

(d) transmitting the digital signals from the probe over the cable to the computer means; and

(e) in response to command signals received by the probe from the computer system

(i) enabling a servo loop including an inertial measuring signal and the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel and vacuum sleeve,

(ii) rotating the cluster assembly to at least two predetermined positions relative to the vacuum sleeve,

(iii) rotating the cluster assembly to achieve at least four dwell positions, determined by measuring outputs from the inertial sensing means;

(10) the upper and lower circuit means, the cluster assembly, and the battery power supply means being supported within the vacuum sleeve in a manner to permit circulation of cooling fluid through the vacuum sleeve in heat exchange relationship with each container of isothermal phase change material,

(11) the upper and lower ends of the thermal sleeve having upper and lower thermal barrier means forming substantially a thermal barrier between the interior of the thermal sleeve and the pressure vessel,

(12) lower port means extending through the lower thermal barrier means to pass conditioning fluid therethrough and upper port means extending through the upper thermal barrier means to pass thermal conditioning fluid therethrough, the upper and lower port means including means for coupling the port means to a source of conditioning fluid and circulating the conditioning fluid from one end of the vacuum sleeve to the other to cool the isothermal phase change material below the isothermal temperature,

(13) electrical conductor means extending through the upper thermal barrier means for providing at least one electrical data transmission path through the thermal barrier, the conductor means including a disconnectable coupling means,

(14) the pressure vessel including a lower pressure resistant closure means which is removable to permit fluid access to the lower port means and an upper pressure resistant closure means which is removable to permit fluid access to the upper port means,

(15) electrical conductor means extending through the upper thermal barrier of the pressure vessel for connection to the computer means for establishing data transmission therebetween,

(16) an electrical conductor means for recharging the battery power supply extending through one of the thermal barrier means; and

(17) means for disconnectably coupling the pressure vessel to the flexible cable for suspending the probe therefrom;

said computer means and data processing and recording means including;

(1) means for receiving digital signals transmitted from the probe via a data path and for transmitting control data to the probe via a data path,

(2) means for displaying information based on data received from the probe,

(3) means for inputting command signals to the probe in response to operator actuated input signals,

the computer means and circuit means carried by said probe including means for, in response to at least one command signal,

(a) initiating operation of the inertial sensing means,

(b) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west when the probe is oriented generally horizontally with the longitudinal axis generally north-south, for predetermined sample periods while reading and storing the outputs of the inertial sensing means,

(c) computing calibration data for selected inertial instruments from the sampled data and comparing the computed calibration to predetermined norms to permit a decision to abandon the survey run with the probe,

(d) rotating the cluster assembly to at least two sample positions while the probe is oriented with the longitudinal axis vertical, in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means,

2. (e) completing calculation of current calibrations for selected inertial sensing means,

(f) initiating a survey mode wherein outputs from the inertial sensing means and temperature sensing means are continuously read and stored and certain computations made for the duration of a survey trip while,

(i) initiating a decoupling mode where the inertial cluster assembly is decoupled from rotational movement of the pressure vessel by the inertially referenced servo loop while the probe is moving longitudinally of the wellbore,

(ii) periodically, while the probe is stationary within the wellbore, stopping rotation of the cluster assembly relative to the pressure vessel for a selected time interval,

(iii) periodically, while the probe is stationary within the wellbore, rotating the inertial cluster assembly to at least two data sample positions at selected relative positions for selected time intervals, and

(g) computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated and corrected by calibration computations made from the output readings obtained during selected survey procedures.

3. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) an inertial cluster assembly including

(a) an elongated, rigid support member disposed within the pressure vessel;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member;

(3) upper and lower journal means for rotatably supporting the cluster assembly within the pressure vessel for rotation about the longitudinal axes of the pressure vessel;

(4) slip ring means including a rotor member mounted to the cluster assembly and a stator assembly supported in the pressure vessel for establishing a plurality of electrical paths between the interior of the pressure vessel and the cluster assembly;

(5) controllable torque means coupled to rotate the cluster assembly including electric motor means;

(6) circuit means disposed within the pressure vessel;

(a) initiating and terminating operation of the inertial sensing means on command;

(b) producing digital data signals representative of the inertial measurements of each inertial sensing means;

(c) transmitting the digital data signals from the probe over the cable to the computer means; and

(d) in response to command signals received by the probe from the computer system

(i) enabling a servo loop including an inertial measuring signal and the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel,

(ii) rotating the cluster assembly to at least two predetermined positions relative to the pressure vessel,

(iii) rotating the cluster assembly on command to achieve at least four dwell positions determined by measuring outputs from the inertial sensing means;

said computer means and data processing and recording means including;

(1) means for receiving digital data transmitted from the probe via a data path and for transmitting control data to the probe via a data path,

(2) means for displaying information based on data received from the probe,

(3) means for inputting command signals to the probe in response to operator actuated input signals,

the computer means and circuit means carried by said probe including means for, in response to at least one command signal,

(a) initiating operation of the inertial sensing means,

(b) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west when the probe is oriented generally horizontally with the longitudinal axis generally north-south, for predetermined sample periods while reading and storing the outputs of the inertial sensing means,

(c) computing calibration data for selected inertial instruments from the sampled data and comparing the computed calibration to predetermined norms to permit a decision to abandon the survey run with the probe,

(d) rotating the cluster assembly to at least two sample positions while the probe is oriented with the longitudinal axis vertical, in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means,

(e) completing calculation of current calibrations for selected inertial sensing means,

(f) initiating a survey mode wherein outputs from the inertial sensing means and temperature sensing means are continuously read and stored and certain computations made for the duration of a survey trip while,

(i) initiating a decoupling mode where the inertial cluster assembly is decoupled from rotational movement of the pressure vessel by the inertially referenced servo loop while the probe is moving longitudinally of the wellbore,

(ii) periodically, while the probe is stationary within the wellbore, stopping rotation of the cluster assembly relative to the pressure vessel for a selected time interval,

(iii) periodically, while the probe is stationary within the wellbore, rotating the inertial cluster assembly to at least two data sample positions at selected relative positions for selected time intervals, and

(g) computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated and corrected by claibration computations made from the output readings obtained during selected survey procedures.

4. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and/or retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) an inertial cluster assembly including

(a) an elongated, rigid support member disposed within the pressure vessel;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member;

(3) upper and lower journal means for rotatably supporting the cluster assembly within the pressure vessel for rotation about the longitudinal axes of the pressure vessel;

(4) slip ring means including a rotor member mounted to the cluster assembly and a stator assembly supported in the pressure vessel for establishing a plurality of electrical paths between the interior of the pressure vessel and the cluster assembly;

(5) controllable torque means coupled to rotate the cluster assembly including electric motor means;

(6) circuit means disposed within the pressure vessel;

(a) producing digital data signals representative of the inertial measurements of each inertial sensing means;

(b) transmitting the digital data signals from the probe over the cable to the computer means;

said computer means and data processing and recording means including;

(1) means for receiving digital data transmitted from the probe via a data path,

(2) means for visually presenting information based on data received from the probe,

(3) means for computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means.

5. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) an inertial cluster assembly including

(a) an elongated, rigid support member disposed within the pressure vessel;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member;

(3) upper and lower journal means supported in the pressure vessel for rotatably supporting the cluster assembly within the pressure vessel for rotation about the longitudinal axes of the pressure vessel;

(4) slip ring means including a rotor member mounted to the upper end of the cluster assembly and a stator member supported in the pressure vessel for establishing a plurality of electrical paths between the interior of the pressure vessel and the cluster assembly;

(5) controllable torque means coupled to rotate the cluster assembly including electric motor means;

(6) rechargeable battery power supply means disposed within the pressure vessel;

(7) circuit means disposed within the pressure vessel including subcircuit means for

(a) producing digital signals representative of the inertial measurements of each inertial sensing means;

(b) transmitting the digital data from the probe over the cable to the computer means; and

(c) in response to command signals received by the probe from the computer system

(i) enabling a servo loop including an inertial measuring signal and the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel,

(ii) rotating the cluster assembly to at least two predetermined positions relative to the pressure vessel,

(iii) rotating the cluster assembly to achieve at least four dwell positions, determined by measuring outputs from the inertial sensing means;

said computer means and data processing and recording means including;

(1) means for receiving digital data transmitted from the probe via a data path and for transmitting control data to the probe via a data path,

(2) means for displaying information based on data received from the probe,

(3) means for inputting command signals to the probe in response to operator actuated input signals,

the computer means and circuit means carried by said probe including means for, in response to at least one command signal,

(a) initiating operation of the inertial sensing means,

(b) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west when the probe is oriented generally horizontally with the longitudinal axis generally north-south, for predetermined sample periods while reading and storing the outputs of the inertial sensing means,

(c) computing calibration data for selected inertial instruments from the sampled data and comparing the computed calibration to predetermined norms to permit a decision to abandon the survey run with the probe,

(d) rotating the cluster assembly to at least two sample positions while the probe is oriented with the longitudinal axis vertical, in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means,

(e) completing calculation of current calibrations for selected inertial sensing means,

(f) initiating a survey mode wherein outputs from the inertial sensing means and temperature sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) initiating a decoupling mode where the inertial cluster assembly is decoupled from rotational movement of the pressure vessel by the inertially referenced servo loop while the probe is moving longitudinally of the wellbore,

(ii) periodically, while the probe is stationary within the wellbore, stopping rotation of the cluster assembly relative to the pressure vessel for a selected time interval,

(iii) periodically, while the probe is stationary within the wellbore, rotating the inertial cluster assembly to at least two data sample positions at selected relative positions for selected time intervals, and

(g) computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated and corrected by calibration computations made from the output readings obtained during selected survey procedures.

6. In a survey system for determining the location of relatively deep boreholes with great accuracy including:

a tubular probe having a maximum diameter less than about four inches and adapted to be lowered into a wellbore;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the pressure vessel into and retrieve the pressure vessel from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the improved probe comprising;

(1) a tubular pressure vessel;

(2) thermal isolation means including a vacuum sleeve disposed within the tubular pressure vessel for substantially thermally isolating the interior thereof from the pressure vessel;

(3) an inertial cluster assembly including

(a) an elongated, rigid, thermally conductive support member disposed within the thermal isolation means;

(b) inertial sensing means for sensing acceleration of the cluster assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member in heat exchange relationship therewith;

(c) transducer and circuit means for sensing the temperatures of the inertial sensing means, and producing an electrical signal representative of the temperatures thereof;

(d) isothermal phase change material in at least one cylindrical container rigidly and thermally coupled to the support member to absorb heat generated by the inertial sensing means to maintain the inertial sensing means at a temperature within a predetermined narrow range for a period of time greater than that required to complete the well survey;

(4) upper and lower journal means for rotatably supporting the cluster assembly within the thermal isolation means for rotation about the longitudinal axes of the thermal isolation means;

(5) at least one slip ring means including a rotor member mounted to one end of the cluster assembly and a stator member supported in the vacuum sleeve for establishing a plurality of electrical paths between the interior of the thermal isolation means and the cluster assembly;

(6) torque means coupled to rotate the cluster assembly including electric motor means for locking the cluster assembly relative to the thermal isolation means when the motor means is inoperative;

(7) circuit means disposed within the thermal isolation means and mounted on and thermally coupled to elongated thermally conductive containers substantially filled with an isothermal phase change material for maintaining the circuits within a predetermined narrow temperature range for a period of time longer than a desired survey run, the circuit means including subcircuit means for

(a) sensing the temperature of the inertial instruments and producing a digital signal representative of the temperature;

(b) initiating and terminating operation of the inertial instruments on command;

(c) producing digital signals representative of the inertial measurements of each inertial instrument;

(d) transmitting the digital data from the probe over the cable to the computer means; and

(e) in response to command signals received by the probe from the computer system

(i) enabling a servo loop from a gyro input signal to the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel and vacuum sleeve,

(ii) rotating the cluster assembly to at least two predetermined positions relative to the vacuum sleeve,

(iii) rotating the cluster assembly to achieve a plurality of sample positions, the positions being determined by measuring outputs from the inertial instruments;

(8) the contents of the thermal isolation means being disposed to permit circulation of conditioning fluid through the vacuum sleeve in heat exchange relationship with each container of isothermal phase change material,

(9) the upper and lower ends of the vacuum sleeve having upper and lower thermal barrier means forming substantially a thermal barrier between the interior of the vacuum sleeve and the pressure vessel,

(10) lower port means extending through the lower thermal barrier means to pass conditioning fluid therethrough and upper port means extending through the upper thermal barrier means to pass thermal conditioning fluid therethrough, the upper and lower port means including means for coupling the port means to a source of conditioning fluid and circulating the conditioning fluid from one end of the vacuum sleeve to the other to cool the isothermal phase change material below the isothermal temperature,

(11) electrical conductor means extending through the upper thermal barrier means for providing at least one electrical data transmission path through the thermal barrier, the conductor means including a disconnectable coupling means,

(12) the pressure vessel including a lower pressure resistant closure means which is removable to permit fluid access to the lower port means and an upper pressure resistant closure means which is removable to permit fluid access to the upper port means,

(13) electrical conductor means extending through the upper thermal barrier of the pressure vessel for connection to the computer means for establishing data transmission therebetween,

(17) means for disconnectably coupling the pressure vessel to the flexible cable for suspending the probe therefrom.

7. In a survey system for determining the location of relatively deep boreholes with great accuracy including

a tubular probe having a maximum diameter less than about four inches and adapted to be lowered into a wellbore;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the pressure vessel into and retrieve the pressure vessel from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the improved probe comprising;

(1) a tubular pressure vessel;

(2) vacuum sleeve means disposed within the tubular pressure vessel for substantially thermally isolating the interior thereof from the pressure vessel;

(3) an inertial cluster assembly including

(a) an elongated, rigid, thermally conductive support member disposed within the vacuum sleeve;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points of the support member in heat exchange relationship therewith;

(c) isothermal phase change material in at least one cylindrical container rigidly and thermally coupled to the support member to absorb heat generated by the inertial sensing means to maintain the inertial sensing means at a temperature within a predetermined narrow range for a period of time greater than that required to complete the well survey;

(4) upper and lower journal means supported in the vacuum sleeve for rotatably supporting the cluster assembly within the vacuum sleeve for rotation about the longitudinal axes of the vacuum sleeve;

(5) slip ring means including a rotor member mounted to the cluster assembly and a stator assembly supported in the vacuum sleeve for establishing a plurality of electrical paths between the interior of the vacuum sleeve and the cluster assembly; and

(6) means coupled to rotate the cluster assembly including electric motor means;

(7) circuit means including subcircuit means for

(a) producing a digital signal representative of the temperature sensed by the temperature transducer means;

(b) initiating and terminating operation of the inertial sensing means on command;

(c) producing digital signals representative of the inertial measurements of each inertial sensing means;

(d) transmitting the digital data from the probe over the cable to the computer means; and

(e) in response to command signals received by the probe from the computer system

(i) enabling a servo loop including an inertial measuring signal and the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel and vacuum sleeve,

(ii) rotating the cluster assembly to selectable positions relative to the vacuum sleeve;

(8) the circuit means and the cluster assembly being supported within the vacuum sleeve in a manner to permit circulation of cooling fluid through the vacuum sleeve in heat exchange relationship with each container of isothermal phase change material; and

(9) closable port means in the pressure vessel for circulating a conditioning fluid into and out of the pressure vessel to remove heat from the isothermal phase change material in preparation for a survey run.

8. In a survey system for determining the location of relatively deep boreholes with great accuracy including

a tubular probe;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically connectable by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the improved probe comprising;

(1) a tubular pressure vessel;

(2) an inertial cluster assembly including

(a) an elongated, rigid support member disposed within the pressure vessel;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member;

(3) upper and lower journal means supported in the pressure vessel for rotatably supporting the cluster assembly within the pressure vessel for rotation about the longitudinal axes of the pressure vessel;

(5) first slip ring means including a rotor member mounted to the upper end of the cluster assembly and a stator assembly supported in the pressure vessel for establishing a plurality of electrical paths between the interior of the pressure vessel and the cluster assembly;

(6) controllable torque means coupled to rotate the cluster assembly including electric motor means;

(7) circuit means disposed within the pressure vessel including subcircuit means for

(a) producing digital signals representative of the inertial measurements of each inertial sensing means;

(b) transmitting the digital data from the probe over the cable to the computer means; and

(e) in response to command signals

(i) enabling a servo loop including an inertial measuring signal and the torque means to approximately decouple the rotation of the cluster assembly from rotation of the pressure vessel,

(ii) rotating the cluster assembly to at least two predetermined positions relative to the pressure vessel

(iii) rotating the cluster assembly to achieve at least four dwell positions, determined by measuring outputs from the inertial sensing means.

10. The survey system of claim 8 wherein:

said circuit means disposed within the vacuum sleeve includes means for periodically stopping rotation of the cluster assembly relative to the pressure vessel for a selected period of time in response to the lapse of a selected period of time.

11. The survey system of claim 8 wherein:

said circuit means disposed within the vacuum sleeve includes means for periodically stopping rotation of the cluster assembly relative to the pressure vessel for a selected period of time in response to a selected output of said inertial sensing means indicative of a minimum amount of acceleration being sensed over a selected period of time.

12. The survey system of claim 8 wherein:

said circuit means disposed within the vacuum sleeve includes means for periodically rotating the cluster assembly to at least two predetermined data sample positions for selected time intervals in response to the lapse of a selected period of time.

13. The survey system of claim 8 wherein:

said circuit means disposed within the vacuum sleeve includes means for periodically rotating the cluster assembly to at least two predetermined data sample positions for selected time intervals in response to a selected output of said inertial sensing means indicative of a minimum amount of acceleration being sensed over a selected period of time.

15. The well survey system of claim 13 wherein:

said means for selectively rotating said plurality of inertial measurement sensors includes means for rotating said plurality of inertial measurement sensors in both clockwise and counterclockwise directions.

16. The well survey system of claim 13 wherein:

said first means for generating said control signal in response to the output of a selected one of said plurality of inertial measurement sensors comprises a servo loop from said selected one of said plurality of inertial measurement sensors and said output comprises a signal representative of the rotation about the longitudinal axis of said tubular probe whereby said plurality of inertial measurement sensors is decoupled from said rotation.

18. The well survey system of claim 16 wherein:

said well survey system further includes computer means adapted to be electrically coupled to said tubular probe for receiving data therefrom and for transmitting control signals thereto, and wherein said communications means includes digital communications circuitry for transmitting digital signals representative of the outputs of said plurality of inertial measurement sensors to said computer means.

20. The well survey system of claim 16 wherein:

said rotator means is responsive to the output of a selected one of said plurality of inertial measurement sensors for selectively rotating said plurality of inertial measurement sensors within said tubular probe.

22. The well survey system of claim 20 wherein:

said well survey system further includes computer means adapted to be electrically coupled to said tubular probe for receiving data therefrom and for transmitting control signals thereto, and wherein said communications means includes digital communications circuitry for transmitting digital signals representative of the outputs of said plurality of inertial measurement sensors to said computer means.

23. The well survey system of claim 20 wherein:

said plurality of inertial measurement sensors include at least one gyroscope and wherein said multiphase power generation means includes means for generating alternating current power at two different frequencies for said at least one gyroscope.

24. The well survey system of claim 20 further including:

rotator means for selectively rotating said plurality of inertial measurement sensors, said rotator means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and said second end of said tubular probe whereby any electromagnetic interference generated by said rotator means is isolated from said communications means.

26. The well survey system of claim 24 wherein:

said multiplex means includes means for receiving control signals coupled to said at least one electrical conductor.

27. The well survey system of claim 24 wherein:

said conversion means is axially displaced from said pluraltiy of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and said at least one electrical conductor and wherein said system further includes multiphase power generation means for supplying multiphase electrical power to said plurality of inertial measurement sensors, said multiphase power generation means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and a second end of said tubular probe whereby any electromagnetic interference generated by said multiphase power generation means is isolated from said conversion means.

29. The well survey system of claim 27 wherein:

said digital counter means includes an upcount mode and a downcount mode and wherein said switching means is coupled to said digital counter means and is effective for selectively altering the mode of operation of said digital counter means.

31. The well survey system of claim 29 further including:

computer means adapted to be electrically coupled to said tubular probe for generating said control signal.

32. The well survey instrument of claim 29 wherein:

said at least two predetermined positions comprise two predetermined positions separated by substantially one hundred and eighty degrees of arc, whereby the outputs of said plurality of inertial measurement sensors at said two predetermined positions may be utilized to determine true north.

34. The well survey system of claim 32 wherein:

said operating parameter sensors are temperature sensing devices whereby the operating temperatures of various components within said tubular probe may be monitored.

35. The well survey system of claim 32 wherein:

said operating parameter sensors are voltage sensing devices, whereby the operating voltages within various components within said tubular probe may be monitored.

9. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe having a maximum diameter less than about four inches and adapted to be lowered into a wellbore;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically coupled by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) vacuum sleeve means disposed within the tubular pressure vessel for substantially thermally isolating the interior thereof from the pressure vessel;

(3) an inertial cluster assembly including

(a) an elongated, rigid, thermally conductive support member disposed within the vacuum sleeve;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member in heat exchange relationship therewith;

(4) controllable torque means coupled to rotate the support member including electric motor means and mechanical means for locking the inertial cluster assembly relative to the vacuum sleeve;

(5) circuit means disposed within the vacuum sleeve for;

(a) initiating and terminating operation of the inertial sensing means on command;

(b) producing analog signals representative of the inertial measurements of said inertial sensing means and converting the analog signals to digital signals representative of the inertial measurements of said inertial sensing means;

(c) transmitting the digital signals from the probe over the cable to the computer means; and

(d) responding to control signals received by the probe from the computer system, the lapse of selected periods of time and selected inertial measurements of said inertial sensing means;

said computer means including;

(1) means for receiving digital signals transmitted from the probe via a data path and for transmitting control signals to the probe via a data path,

(2) means for displaying data received from the probe;

(3) means for inputting control signals to the probe in response to operator actuated input signals,

said computer means and circuit means carried by said probe including means for, in response to at least one control signal,

(a) initiating operation of the inertial sensing means,

(b) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at each of four different positions for predetermined sample periods while reading and storing the outputs of the inertial sensing means,

(c) computing calibration data for said inertial sensing means from the sampled data and comparing the computed calibration to predetermined norms,

(d) rotating the cluster assembly to at least two predetermined sample positions while reading and storing the outputs from the inertial sensing means,

(e) initiating a survey mode wherein outputs from the inertial sensing means and temperature sensing means are continuously read and position computations made for the duration of a survey trip while

(i) initiating a decoupling mode where the inertial cluster assembly is decoupled from rotational movement of the pressure vessel by the inertially referenced servo loop while the probe is rotating longitudinally in the wellbore.

(ii) periodically, while the probe is stationary within the wellbore, stopping rotation of the cluster assembly relative to the pressure vessel for a selected time interval,

(iii) periodically, while the probe is stationary within the wellbore, rotating the cluster assembly to at least two predetermined data sample positions for selected time intervals, and

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated and corrected by computations made from the output readings obtained during a selected survey procedure.

14. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

computer means adapted to be electrically coupled to said tubular probe for receiving data therefrom and for transmitting control signals thereto;

at least one electrical conductor forming an electrical data transmission path between said computer means and said tubular probe;

a plurality of inertial measurement sensors rotatably mounted in fixed relationship within said tubular probe for sensing acceleration and/or rotation of said tubular probe;

means for selectively coupling each of the outputs of said plurality of inertial measurement sensors to said at least one electrical conductor;

means of selectively rotating said plurality of inertial measurement sensors about the axis of said tubular probe in response to a control signal;

first means for generating said control signal in response to the output of a selected one of said plurality of inertial measurement sensors; and

second means for generating said control signal in response to an electrical signal coupled to said at least one electrical conductor from said computer means.

17. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors rotatably mounted in fixed relationship within said tubular probe;

communications means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and said at least one electrical conductor for selectively coupling each of the outputs of said plurality of inertial measurement sensors to said at least one electrical conductor; and

rotator means for selectively rotating said plurality of inertial measurement sensors, said rotator means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and a second end of said tubular probe whereby any electromagnetic interference generated by said rotator means is isolated from said communications means.

19. The well survey system of claim 17 wherein:

said rotator means is responsive to a selected control signal coupled to said at least one electrical conductor from said computer means for selectively rotating said plurality of inertial measurement sensors within said tubular probe.

21. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors mounted in fixed relationship within said tubular probe;

communications means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and said at least one electrical conductor for selectively coupling each of the outputs of said plurality of inertial measurement sensors to said at least one electrical conductor; and

multiphase power generation means for supplying multiphase electrical power to said plurality of inertial measurement sensors, said multiphase power generation means axially displaced from said plurality of inertial measurement sensors and disposed between said plurality of inertial measurement sensors and a second end of said tubular probe whereby any electromagnetic interference generated by said multiphase power generation means is isolated from said communications means.

25. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors mounted in fixed relationship within said tubular probe, each of said plurality of inertial measurement sensors having at least one analog output indicative of the state of at least one inertial parameter;

conversion means for converting said at least one analog output of each of said plurality of inertial measurement sensors into a plurality of digital signals representative thereof; and

multiplex means for selectively coupling said plurality of digital signals to said at least one electrical conductor.

28. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors mounted in fixed relationship within said tubular probe, each of said plurality of inertial measurement sensors having at least one analog output indicative of the state of at least one inertial parameter;

conversion means for converting said at least one analog output of each of said plurality of inertial measurement sensors into a digital output signal representative thereof, said conversion means comprising;

switching means for selectively reversing the polarity of said at least one analog output;

summing means for summing the output of said switching means and a selected reference voltage;

digital frequency generation means for generating a selected frequency in response to each particular output of said summing means;

digital counter means coupled to the output of said digital frequency generation means for generating a digital output signal in response thereto; and

means for selectively coupling said digital output signal to said at least one electrical conductor.

30. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors rotatably mounted in fixed relationship within said tubular probe;

means for selectively coupling each of the outputs of said plurality of inertial measurement sensors to said at least one electrical conductor;

means for rotating said plurality of inertial measurement sensors about the axis of said tubular probe to each of at least two predetermined positions in response to a control signal.

33. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors mounted in fixed relationship within said tubular probe;

a plurality of operating parameter sensors disposed at selected locations within said tubular probe; and

means for selectively coupling each of the outputs of said plurality of inertial measurement sensors and each of the outputs of said plurality of operating parameter sensors to said at least one electrical conductor.

36. A well survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe adapted to be passed through a wellbore;

at least one electrical conductor disposed at a first end of said tubular probe for forming an electrical data transmission path from said tubular probe;

a plurality of inertial measurement sensors mounted in fixed relationship within said tubular probe;

timing means having an output indicative of the elapsed time from a selected point in time; and

means for periodically coupled each of the outputs of said plurality of inertial measurement sensors and said output of said timing means to said at least one electrical conductor.

38. The method of claim 36 wherein, at least prior to performing computations to determine the statiscally most likely coordinates of the path of the borehole,

initial restraint factors, mass unbalance factors are determined prior to the start of the run for the X axis gyro, the Y axis gyro, and the restraint, mass unbalance and the scale factor of the Z axis gyro, and

the bias factors and scale factors for the X axis accelerometer and the Y axis accelerometer.

39. The method of claim 36 further characterized by:

stopping the probe at said known point in the top of the wellbore and rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

removing the probe from the wellbore and positioning the probe generally horizontal and in a generally north-south direction; and

rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means.

37. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel having an inertial cluster assembly including an elongated, rigid support member within the vessel and inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates or rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member, the steps comprising;

(a) positioning the longitudinal axis of the probe generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(d) computing current calibration data for selected inertial instruments from the sampled data and comparing the computed calibration data to predetermined norms to permit a preliminary decision to abandon the survey run with the probe;

(e) positioning the probe with the longitudinal axis in the vertical position at a known point in the top of the wellbore and rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

(f) completing computations of current calibrations for selected inertial sensing means and the position of true north and horizontal;

(g) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) substantially preventing rotation of the inertial cluster assembly while the probe is moving longitudinally of the wellbore;

(ii) periodically substantially stopping movement of the inertial cluster within the wellbore while continuing to read and store data for a selected time interval;

(iii) periodically, while the probe is stationary within the wellbore, rotating the inertial cluster assembly to at least two data sample positions at selected relative rotational positions for selected time intervals; and

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated from corrections made.

40. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel having an inertial cluster including an elongated, rigid support member within the vessel and inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member, the steps comprising;

(a) positioning the longitudinal axis of the probe generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(e) positioning the probe with the longitudinal axis in the vertical position at a known point in the top of the wellbore;

(f) rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

(g) computing current calibrations for selected inertial sensing means and the position of true north and horizontal;

(h) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) substantially preventing rotation of the inertial cluster assembly while the probe is moving longitudinally of the wellbore;

(ii) periodically substantially stopping movement of the inertial cluster within the wellbore while continuing to read and store data for a selected time interval;

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated during the current survey procedure.

41. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel;

an elongated, rigid support member within the vessel; and

inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member to form a cluster assembly, the steps comprising;

(a) positioning the longitudinal axis of the cluster assembly generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position at least one of the sense axes at at least one predetermined position while reading and storing the data outputs of the inertial sensing means for a sample period;

(d) computing current calibration data for selected inertial instruments from the data outputs and comparing the computed calibration data to predetermined norms to permit a preliminary decision to abandon the survey run with the probe.

42. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel;

an elongated, rigid support member within the vessel; and

inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member, the steps comprising;

(a) positioning the longitudinal axis of the probe generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(d) computing current calibration data for selected inertial instruments from the sampled data and comparing the computed calibration data to predetermined norms to permit a preliminary decision to abandon the survey run with the probe;

(e) positioning the probe with the longitudinal axis in the vertical position at a known point in the top of the wellbore;

(f) rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

(g) completing computations of current calibrations for selected inertial sensing means and the position of true north and horizontal;

(h) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) substantially preventing rotation of the inertial cluster assembly while the probe is moving longitudinally of the wellbore;

(ii) periodically substantially stopping movement of the inertial cluster within the wellbore while continuing to read and store data for a selected time interval;

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated from corrections made.

43. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel;

an elongated, rigid support member within the vessel; and

inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member, the steps comprising;

(a) positioning the probe with the longitudinal axis in the vertical position at a known point in the top of the wellbore;

(b) rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

(c) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) substantially preventing rotation of the inertial cluster assembly while the probe is moving longitudinally of the wellbore;

(ii) periodically substantially stopping movement of the inertial cluster within the wellbore while continuing to read and store data for a selected time interval;

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means.

45. The survey system of claim 43 wherein:

said stored data representative of selected fixed calibration data for said probe is stored in a tape cassette unit associated with said probe.

46. The survey system of claim 43 wherein:

said stored data representative of selected fixed calibration data for said probe is stored in a solid state memory device mounted within said probe.

44. The survey system for determining the location of relatively deep boreholes with great accuracy comprising:

a tubular probe having a maximum diameter less than about four inches and adapted to be lowered into a wellbore;

a flexible cable attached to the upper end of the probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole;

reel means for controllably paying out and retrieving the flexible cable to lower the probe into and retrieve the probe from the wellbore;

computer means including keyboard input means, data processing means, data readout means and data recording means electrically coupled by the flexible cable to the probe to receive data from and give commands to circuit means therein;

the probe comprising;

(1) a tubular pressure vessel;

(2) vacuum sleeve means disposed within the tubular pressure vessel for substantially thermally isolating the interior thereof from the pressure vessel;

(3) an inertial cluster assembly including

(a) an elongated, rigid, thermally conductive support member disposed within the vacuum sleeve;

(b) inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member in heat exchange relationship therewith;

(4) controllable torque means coupled to rotate the support member including electric motor means and mechanical means for locking the inertial cluster assembly relative to the vacuum sleeve;

(5) circuit means disposed within the vacuum sleeve for;

(a) initiating and terminating operation of the inertial sensing means on command;

(b) producing analog signals representative of the inertial measurements of said inertial sensing means and converting the analog signals to digital signals representative of the inertial measurements of said inertial sensing means;

(c) transmitting the digital signals from the probe over the cable to the computer means; and

(d) responding to control signals received by the probe from the computer system, the lapse of selected periods of time and selected inertial measurements of said inertial sensing means;

said computer means including;

(1) means for receiving digital signals transmitted from the probe via a data path and for transmitting control signals to the probe via a data path,

(2) means for displaying data received from the probe;

(3) means for inputting control signals to the probe in response to operator actuated input signals,

said computer means and circuit means carried by said probe including means for, in response to at least one control signal,

(4) means for accessing stored data representative of selected fixed calibration data for said probe,

(a) initiating operation of the inertial sensing means,

(b) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at each of four different positions for predetermined sample periods while reading and storing the outputs of the inertial sensing means,

(c) computing calibration data for said inertial sensing means from the sampled data and said selected fixed calibration data and comparing the computed calibration to predetermined norms,

(d) rotating the cluster assembly to at least two predetermined sample positions while reading and storing the outputs from the inertial sensing means,

(e) initiating a survey mode wherein outputs from the inertial sensing means and temperature sensing means are continuously read and position computations made for the duration of a survey trip while

(i) initiating a decoupling mode where the inertial cluster assembly is decoupled from rotational movement of the pressure vessel by the inertially referenced servo loop while the probe is rotating longitudinally in the wellbore,

(ii) periodically, while the probe is stationary within the wellbore, stopping rotation of the cluster assembly relative to the pressure vessel for a selected time interval.

(iii) periodically, while the probe is stationary within the wellbore, rotating the cluster assembly to at least two predetermined data sample positions for selected time intervals, and

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated and corrected by computations made from the output readings obtained during a selected survey procedure.

47. A method of operating a borehole survey system which includes a tubular probe adapted to be lowered into a wellbore having a plurality of inertial measurement sensors disposed therein, a flexible cable attached to the upper end of said probe including at least one electrical data transmission path and having sufficient length to lower the probe into the borehole and a computer means electrically coupled by means of the flexible cable to the probe for receiving data therefrom and for transmitting control signals thereto, comprising:

identifying fixed calibration data intrinsic to said probe as a result of manufacture;

storing said fixed calibration data in a substantially permanent media associated with said probe;

operating said plurality of inertial measurement sensors for a selected period of time over a selected range of movement to obtain current calibration data prior to each operation of said system;

coupling said current calibration data to said computer means;

coupling said fixed calibration data to said computer means;

lowering said tubular probe into a wellbore while measuring and storing the outputs of said plurality of inertial measurement sensors;

utilizing said computer to calibrate said outputs of said plurality of inertial measurement sensors in response to said fixed calibration data and said current calibration data; and

computing the path of said probe utilizing the calibrated outputs of said plurality of inertial measurement sensors.

49. The method of claim 47 wherein the vertical position of said sense axis is determined by nulling the outputs from the inertial sensing means for the other two orthogonally disposed axes.

48. The method of surveying a borehole to determine its location using a probe having an elongated, rigid support member and inertial sensing means rigidly mounted on the support member to form a cluster assembly, the inertial sensing means including means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axis of the probe, and for sensing rates of rotation about the same three axes, which comprises:

calibrating the inertial sensing means for measuring acceleration along the axes aligned with the longitudinal axis of the probe by successively positioning the probe with said sense axis disposed vertically upwardly and vertically downwardly for sample periods while reading the outputs from said sensing means, and

computing the bias factor and scale factor from the sampled outputs.

50. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel;

an elongated, rigid support member within the vessel; and

inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes X, Y and Z, With the Z axis being aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being ridigly mounted at spaced points on the support member, the steps comprising;

(a) positioning the longitudinal axis of the probe generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(d) positioning the positive Z axis vertically up for a sample period and vertically down for a sample period while reading and storing the outputs of the inertial sensing means;

(e) computing current calibration data for selected inertial instruments from the sampled data and comparing the computed calibration data to predetermined norms to permit a preliminary decision to abandon the survey run with the probe;

(f) holding the probe essentially stationary for a predetermined period while continuing to read and store data, making survey calculations to detect any drift error in the system during the sample period and comparing the calculated drift error to an established norm to permit a preliminary decision to abandon the survey run with the probe;

(g) positioning the probe with the longitudinal axis in the vertical position at a known point in the top of the wellbore;

(h) rotating the cluster assembly to at least two sample positions in predetermined relationship one to the other while reading and storing the outputs from the inertial sensing means;

(i) completing computations of current calibrations for selected inertial sensing means and the position of true north and horizontal;

(j) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip while

(i) substantially preventing rotation of the inertial cluster assembly while the probe is moving longitudinally of the wellbore;

(ii) periodically substantially stopping movement of the inertial cluster within the wellbore while continuing to read and store data for a selected time interval;

computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means as calibrated from corrections made.

51. The method of surveying a relatively deep borehole to determine its location using:

a probe comprising a tubular pressure vessel;

an elongated, rigid support member within the vessel; and

inertial sensing means for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, one of which is aligned with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the inertial sensing means being rigidly mounted at spaced points on the support member to form a cluster assembly, the steps comprising;

(a) positioning the longitudinal axis of the probe generally horizontal and in a generally north-south direction;

(b) initiating operation of the inertial sensing means;

(c) rotating the cluster assembly while monitoring outputs of the inertial sensing means to position one of the sense axes at four positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(d) positioning the positive Z axis vertically up for a sample period and vertically down for a sample period while reading and storing the outputs of the inertial sensing means;

(e) computing current calibration data for selected inertial instruments from the sampled data and comparing the computed calibration data to predetermined norms to permit a preliminary decision to abandon the survey run with the probe.

52. In a method of surveying a relatively deep borehole to determine its location using a probe comprising a tubular pressure vessel having an inertial cluster assembly including an elongated, rigid support member with inertial sensing means rigidly mounted thereon for sensing acceleration of the inertial assembly along three substantially orthogonally disposed sense axes, X, Y and Z with the Z axis aligned generally with the longitudinal axes of the probe, and for sensing rates of rotation about the same three orthogonally disposed axes, the steps comprising:

(a) initiating operation of the inertial sensing means;

(b) positioning the Z axis generally horizontal and in a generally north-south direction and rotating the cluster assembly while monitoring outputs of the inertial sensing means to position the positive X axis at four sample positions, vertically up and down and horizontally east and west, for predetermined sample periods while reading and storing the outputs of the inertial sensing means;

(c) rotating the probe from one sample position where the positive Z axis is in one vertical position to another sample position where the positive Z axis is in the opposite vertical direction with the X axis disposed horizontally while the probe is rotated;

(d) rotating the probe from one sample position where the positive Z axis is in one vertical position to another sample position where the positive Z axis is in the opposite vertical direction with the Y axis disposed horizontally while the probe is rotated;

(e) computing the current calibration data for the inertial instruments including the restraint factors, mass unbalance factors and scale factors of at least selected gyros and the bias factors and scale factors of at least selected accelerometers;

(f) initiating a survey mode wherein the probe traverses the wellbore while the outputs from the inertial sensing means are continuously read and stored and certain computations made for the duration of a survey trip; and

(g) computing the path of the probe relative to a three dimensional coordinate system using the inertial measurements produced by the inertial sensing means using the current calibrations.