METHODS AND APPARATUS FOR TESTING EARTH FORMATIONS

• US 3,859,850 A
• Filed: 03/20/1973
• Issued: 01/14/1975
• Est. Priority Date: 03/20/1973
• Status: Expired due to Term

• Current Assignee: FoodCraft Equipment Company Incorporated
• Original Assignee: Frank R. Whitten, Joachim A. Hoppe
• Inventors: Hoppe, Joachim A., Whitten, Frank R.
• Primary Examiner(s): Myracle, Jerry W.
• Application Number:
  US05/343,081
• Time in Patent Office: 665 Days
• Field of Search: 73/151,152,155 166/264,100
• US Class Current: 73/152.24
• CPC Class Codes: E21B 49/10 using side-wall fluid samplers or testers

Abstract

In the representative embodiments of the new and improved methods and apparatus for testing earth formations disclosed herein, fluid-admitting means are placed into sealing engagement with a potentially producible earth formation. Selectively operable valve means are opened to place the fluid-admitting means into communication with sample-collecting means comprised of an initially empty first collection chamber that is tandemly coupled to a vacant accessible portion of a second samplecollection chamber that is itself divided by a piston member movably disposed therein and normally biased toward the entrance to the second chamber by a charge of compressed gas confined in an enclosed portion of the second chamber. In this manner, as connate fluids enter the sample-collecting means, the first sample chamber will initially be filled before sufficient presure is built up in the first chamber to begin moving the piston member so as to allow connate fluids to begin filling the second chamber. By observing the time required for filling the first chamber, the flow rate of entering connate fluids can be at least estimated. Once the first chamber is filled and the pressure of connate fluids therein equals the pressure of the compressed gas, movement of the piston into the gas-filled portion of the second chamber will further compress the gas charge so as to impose a proportionally increasing back pressure on the connate fluids which may be measured to obtain a second measurement that is representative of the rate at which connate fluids, if any, are entering the second sample chamber.

Claims

1. A method for investigating earth formations traversed by a well bore and comprising the steps of:

isolating a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids from well bore fluids;

communicating a first empty sample chamber with said isolated wall surface for inducting a preliminary sample of connate fluids from said earth formation into said first sample chamber;

blocking the discharge of said preliminary connate fluid sample into a second empty sample chamber until said first sample chamber is filled with said preliminary connate fluid sample and the pressure thereof has increased to a predetermined pressure level;

monitoring the pressure of said preliminary connate fluid sample for obtaining a first pressure measurement indicative of said predetermined pressure level to determine when said first sample chamber is filled; and

once said first sample chamber is filled with said preliminary connate fluid sample, opening communication between said sample chambers for collecting said preliminary connate fluid sample as well as an additional sample of said connate fluids.

2. The method of claim 1 further including the additional step of:

correlating said first pressure measurement as a function of time for determining the rate at which said preliminary connate fluid sample entered said first sample chamber.

3. The method of claim 1 further including the additional steps of:

regulating the flow of said connate fluid samples as they are admitted into said second sample chamber by imposing a progressively-increasing restraining force on said connate fluid samples for correspondingly increasing the pressure of said connate fluid samples as they continue to enter said second sample chamber; and

monitoring the pressure of said connate fluid samples for obtaining at least a second pressure measurement indicative of the admission of said connate fluid samples into said second sample chamber.

4. The method of claim 3 further including the additional step of:

obtaining at least a third measurement of the pressure of said connate fluid samples at a later time for determining from said second and third pressure measurements a function representative of the average flow rate at which said connate fluid samples are entering said second sample chamber.

5. The method of claim 3 wherein said restraining force has a predetermined initial magnitude selected for increasing the pressure of said preliminary connate fluid sample to its said predetermined pressure level before said preliminary connate fluid sample first begins to enter said second chamber so that when said first pressure measurement attains said predetermined pressure level it will indicate the initial entrance of said preliminary connate fluid sample into said second sample chamber.

6. The method of claim 5 further including the additional step of:

obtaining at least two successive additional measurements of the pressure of said connate fluid samples at different times following the initial entrance of said preliminary connate fluid sample into said second sample chamber for determining a function representative of the average flow rate at which said connate fluid samples are entering said second sample chamber.

7. The method of claim 1 wherein said restraining force has a predetermined initial magnitude selected for increasing the pressure of said preliminary connate fluid sample to its said predetermined pressure level before said preliminary connate fluid sample first begins to enter said second sample chamber so that subsequent increases in the pressure of said connate fluid samples will be at progressively-greater pressure levels than said predetermined pressure level as said connate fluid samples continue to enter said second sample chamber and further including the additional step of:

re-monitoring the pressure of said connate fluid samples for subsequently obtaining at least a second pressure measurement greater than said predetermined pressure level indicative of the continuing entrance of said connate fluid samples into said second sample chamber.

8. The method of claim 7 further including the additional step of:

correlating said first and second pressure measurements as a function of time for determining the average flow rate at which said connate fluid samples are then entering said second sample chamber.

9. A method for investigating earth formations traversed by a well bore and comprising the steps of:

isolating a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids from well bore fluids;

communicating said isolated wall surface with a first empty sample chamber having a selected fixed capacity for inducting a first sample of connate fluids from said earth formation into said first sample chamber;

imposing a restraining back pressure of a selected initial magnitude within said first sample chamber for preventing the release of said first sample of connate fluids from said first chamber into an expandable second empty sample chamber adapted to be expanded from an initial limited capacity to a selected maximum capacity until said first sample of connate fluids has filled said first sample chamber and is at a selected pressure sufficient to overcome said initial restraining back pressure;

monitoRing the pressure of said first sample of connate fluids for determining when said first sample of connate fluids reaches said selected pressure to provide a first indication at the surface that said first sample of connate fluids has been released into said second sample chamber and a second sample of connate fluids is beginning to enter said first sample chamber;

progressively increasing said restraining back pressure after said first sample of connate fluids has been released into said second sample chamber for correspondingly increasing the pressure of said connate fluid samples as said second sample chamber is expanded from its said initial capacity toward its said maximum capacity; and

re-monitoring the pressure of said connate fluid samples for determining when said connate fluid samples exceed said selected pressure to provide a second indication at the surface that said connate fluid samples are continuing to enter said first and second sample chambers.

10. The method of claim 9 wherein said initial capacity of said second sample chamber is negligible in relation to its said maximum capacity.

11. The method of claim 9 wherein said fixed capacity of said first sample chamber is less than said maximum capacity of said second sample chamber and said initial capacity of said second sample chamber is negligible in relation to its said maximum capacity.

12. The method of claim 9 further including the additional steps of:

after said connate fluid sample reaches said selected pressure, obtaining at least two successive measurements of the pressure of said connate fluid samples at spaced time intervals; and

correlating said successive pressure measurements for determining a function representative of the average flow rate at which said connate fluid samples are then entering said first and second sample chambers.

13. The method of claim 9 wherein said restraining back pressure is imposed within said first sample chamber by disposing a movable piston member in said second sample chamber for dividing said second sample chamber into an accessible sample-receiving portion adapted to be expanded from said initial capacity to said maximum capacity upon movement of said piston member into said sample chamber as well as an enclosed portion adapted to be contracted upon movement of said piston member into said sample chamber, and filling said enclosed chamber portion with a pressured compressible gas for imposing said restraining back pressure against said piston member.

14. The method of claim 13 wherein said compressible gas has a predetermined initial pressure which will increase in accordance with the general gas laws as said first sample of connate fluids first begins to enter said enclosed chamber portion so that the continued entrance therein of said samples of connate fluids will progressively increase the pressure of said samples of connate fluids as said compressible gas is further compressed above said restraining back pressure by movement of said piston member into said second sample chamber.

15. Formation-testing apparatus adapted for suspension in a well bore traversing earth formations and comprising:

a body having a first fluid passage adapted to receive connate fluids;

fluid-admitting means on said body and adapted to be selectively engaged with a well bore wall for isolating a portion thereof from well bore fluids;

means on said body and selectively operable for positioning said fluid-admitting means against a well bore wall to establish communication with connate fluids in earth formations therebeyond;

sample-collecting means on said body and including a first sample chamber, means selectively operable for coupling said fluid passage to said first sample chamber to receive connate fluids entering said fluid-admitting means, a second sample chamber, and a second fluid passage adapted for communicating said first sample chamber with said second sample chamber;

pressure-measuring means including a Pressure transducer on said body adapted for providing indications at the surface representative of the pressure of connate fluids entering said sample chambers; and

flow-regulating means cooperatively associated with said sample chambers and adapted for initially blocking passage of connate fluids from said first sample chamber through said second fluid passage into said second sample chamber until connate fluids in said first sample chamber attain an initial predetermined back pressure and thereafter imposing a progressively increasing back pressure on such connate fluids being released from said first sample chamber into said second sample chamber which is proportional to the volume of connate fluids contained in said second sample chamber.

16. The formation-testing apparatus of claim 15 wherein said flow-regulating means are comprised of:

a piston member movably disposed within said second sample chamber for dividing said second sample chamber into a first sample-receiving portion adapted to be expanded from an initial minimum capacity to a maximum capacity upon movement of said piston member into said second sample chamber as well as a second enclosed portion adapted to be contracted upon movement of said piston chamber; and

a pressured compressible gas in said second chamber portion imposing an initial selected restraining pressure against said piston member for restraining movement thereof until connate fluids in said first sample chamber attain said initial back pressure and thereafter imposing a progressively increasing restraining pressure against said piston member in keeping with the general gas laws as connate fluids enter said first chamber portion of said second sample chamber.