Method of dynamically monitoring the orientation of a curved drilling assembly and apparatus

• US 5,259,468 A
• Filed: 10/03/1991
• Issued: 11/09/1993
• Est. Priority Date: 10/04/1990
• Status: Expired due to Term

• Current Assignee: Amoco Corporation (BP PLC)
• Original Assignee: Amoco Corporation (BP PLC)
• Inventors: Warren, Tommy M., Winters, Warren J.
• Primary Examiner(s): Bagnell, David J.
• Application Number:
  US07/771,587
• Time in Patent Office: 768 Days
• Field of Search: 175/40, 175/45, 175/48, 175/61, 175/73, 175/74, 166/113, 367/83, 367/85
• US Class Current: 175/45
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022
• CPC Class Codes: E21B 47/095 by detecting an acoustic anomalies, e.g. using mud-pressure pulses
• CPC Class Codes: E21B 47/18 through the well fluid , e.g. mud pressure pulse telemetry
• CPC Class Codes: E21B 7/062 the tool shaft rotating inside a non-rotating guide travelling with the shaft E21B7/067 and E21B7/068 take precedence

Abstract

Rotational orientation of a drillstring is monitored a plurality of times during each rotation of a drillstring for monitoring the rotational orientation of a curve drilling assembly on a drillstring. A defined rotational orientation of a downhole location on the drillstring with respect to the curve drilling assembly is established. At least one reference signal generator having a known relationship to the down hole location on the drillstring and that rotates with the drillstring is provided at the surface. A reference signal is generated each time a reference signal generator rotates past a detector. A pressure signal is generated each time the drillstring rotates through the defined rotational orientation with respect to the drill bit steering device. Occurrences of the plurality of surface reference signals and the pressure signal are timed and compared for monitoring the rotational orientation of the drill bit steering device.

Claims

1. A method for dynamically monitoring the rotational orientation of a downhole tool on a rotatable conduit, comprising the steps of:

(a) establishing an initial rotation orientation of a downhole tool with respect to a plurality of reference points on a rotatable conduit;

(b) generating a tool signal when the rotating conduit is in a defined rotational orientation with respect to the downhole tool during drilling; and

(c) monitoring the rotational orientation of the rotating conduit at which said tool signal occurs by

generating at least one reference signal each time said reference points and said conduit complete 360 degrees of rotation,

generating a tool signal each time said rotating conduit is in said defined rotational orientation with respect to said downhole tool, and

determining the angular displacement of said reference points relative to said initial rotational orientation of said downhole tool and rotatable conduit at which said tool signal is generated by measuring the angular displacement between said reference signals and said tool signals.

2. A method of claim 1 in which step (b) comprises:

flowing fluid through the rotating conduit;

changing the size of a fluid flow path through the rotating conduit when the rotating conduit is in the defined rotational orientation with respect to the downhole tool; and

sensing the response of the flowing fluid to the change in size of the fluid flow path to generate the tool signal.

3. A method of claim 1 in which step (b) comprises:

pumping fluid through the conduit;

changing the size of the fluid flow path through the conduit when the conduit is in the defined rotational orientation with respect to the downhole tool in order to create a pressure change in the flowing fluid;

recording a pressure profile of the pumped fluid when the conduit is not rotating;

recording a pressure profile of the pumped fluid when the conduit is rotating; and

comparing the pressure profiles.

4. The method of claim 1, further including the step of:

(d) stopping rotation of the conduit and reorienting the downhole tool when dynamic monitoring indicates that reorientation is necessary.

5. A method of dynamically monitoring the rotational orientation of a curve drilling assembly on a drillstring, comprising the steps:

(a) generating a pressure signal when a drillstring is in a defined rotational orientation relative to a cure drilling assembly during drilling;

(b) generating a plurality of reference signals for monitoring the rotational orientation of the drillstring at which the pressure signal occurs; and

(c) comparing the times of occurrence of the pressure signal and the reference signals for dynamically monitoring the rotational orientation of the curve drilling assembly.

6. A method of claim 5 wherein the pressure signal is generated by:

providing a drillstring orifice through a wall of the drillstring;

providing an assembly orifice through a wall of the curve drilling assembly;

pumping drilling fluid through the drillstring and the drillstring orifice;

aligning the drillstring orifice and assembly orifice when the drillstring is in a defined rotational orientation with respect to the curve drilling assembly for causing a pressure decrease in the drilling fluid; and

detecting the pressure signal.

7. A method of claim 6 utilizing a round drillstring orifice and an elongated slot assembly orifice.

8. A method of claim 6 wherein the pressure signal is generated by:

recording a pressure profile of the pumped drilling fluid when the drillstring is not rotating;

recording a pressure profile of the pumped drilling fluid when the drillstring is rotating; and

comparing the pressure profiles.

9. A method of claim 5 wherein the plurality of reference signals are generated by:

establishing plurality of surface references having an initial orientation with respect to the defined rotational orientation of the drillstring relative to the curve drilling assembly;

providing a stationary detector for detecting the plurality of surface references; and

detecting the plurality of surface references during each rotation of the drillstring.

10. A method of claim 5 including the step of determining torque distributed in the drillstring at about the time the pressure signal is generated.

11. A method of claim 10, wherein said step of determining torque is performed by using a strain gauge load cell.

12. A method of claim 5 wherein the pressure signal and the plurality of reference signals are compared by:

subtracting the signal delay time from the time at which the pressure signal was detected for determining the time at which orifices in the drillstring and curve drilling assembly were aligned;

analyzing the plurality of reference signals for determining the azimuthal orientation of the plurality of surface references at about the time at which orifices in the drillstring and curve drilling assembly were aligned;

using torque distributed in the drillstring for determining twist in the drillstring at about the time at which orifices in the drillstring and curve drilling assembly were aligned.

13. A method of dynamically monitoring the rotational orientation of a curve drilling assembly on a drillstring and reorienting the curve drilling assembly when necessary, the method comprising the steps:

(a) generating a pressure signal when a drillstring is in a defined orientation relative to a curve drilling assembly during drilling;

(b) generating a plurality of reference signals for monitoring the rotational orientation of the drillstring at which the pressure signal occurs;

(c) comparing the pressure signal and the plurality of reference signals for dynamically monitoring the rotational orientation of the curve drilling assembly; and

(d) stopping drilling and reorienting the curve drilling assembly when dynamic monitoring indicates that reorientation is necessary.

14. A method of generating a correction factor accounting for sonic signal delay for use in determining the rotational orientation of a downhole tool on a rotatable conduit, comprising:

(a) rotating the conduit at at least two rotational speeds and generating a signal when the rotating conduit is in a defined rotational orientation with respect to the downhole tool;

(b) monitoring the rotational orientation of the rotating conduit at which each of the signals of step (a) occur; and

(c) generating an indication of sonic signal delay for one or more rotational speeds from a calculation of linear slope of signals obtained from the at least two rotational speeds.

15. The method of claim 14, wherein the signal of step (a) is generated downhole;

and wherein step (b) is performed above the surface of the wellbore.