Formation pressure measuring method and formation pressure measuring tubular column

Abstract

The invention relates to the technical field of in-well pressure measurement, in particular to a formation pressure measuring method and a formation pressure measuring pipe column, the formation pressure measuring pipe column comprises an oil pipe, a pressure measuring element, a packer and a liquid extractor, the packer seals the annulus of the pressure measuring pipe column and a shaft above the formation, the liquid extractor comprises a cylinder body and a piston, the cylinder body is connected with the oil pipe, and the piston is connected with the oil pipe. The piston divides an inner cavity of the pressure measuring pipe column into an upper pipe cavity and a lower pipe cavity, the piston and the cylinder body move relatively to be used for sucking well killing fluid in the lower pipe cavity of the pressure measuring pipe column so that formation fluid can flow into a shaft from a formation, and the pressure of the lower pipe cavity of the pressure measuring pipe column and the pressure of the shaft below the packer are equal to the pressure of the formation. The liquid column pressure of the well killing fluid in the upper pipe cavity and the space above the packer is separated from the pressure of the lower pipe cavity and the space below the packer, the formation pressure can be obtained by measuring the pressure of the lower pipe cavity of the pressure measuring pipe column or the pressure of a shaft below the packer, the influence of the well killing fluid in the shaft is avoided, and the formation pressure measuring accuracy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of measuring well pressure, and in particular to a formation pressure measuring method and a formation pressure measuring pipe string. Background Art

[0002] In the process of oil field development, especially in multi-layer oil fields, there are contradictions between and within layers. It is usually necessary to analyze reservoir characteristics based on the changes in reservoir pressure, so as to provide a strong basis for the next step of development and transformation of the reservoir and the long-term water control and oil production increase of the oil field. Obtaining accurate formation pressure data is an important condition for ensuring the safety of oil well production and increasing oil well production.

[0003] At present, for the measurement of formation pressure, a pressure gauge is usually lowered into the wellbore at the position corresponding to the oil layer for pressure measurement. The oil pipe is used to carry the pressure gauge into the wellbore. The oil pipe and the pressure gauge constitute a pressure measuring string, and the pressure gauge constitutes a pressure measuring element. For the formation pressure measurement after drilling, the wellbore is often filled with well-killing fluid. For the wellbore filled with well-killing fluid, the above conventional pressure measurement method is relatively accurate for the formation measurement data with high permeability and little oil layer pollution by drilling mud. However, when measuring the pressure of the formation with low permeability and great oil layer pollution by drilling mud, due to the well-killing fluid in the wellbore, it is affected by the liquid column pressure of the well-killing fluid, and the formation start-up pressure is much higher than the formation pressure. Therefore, the wellbore pressure will be higher than the formation pressure, which will cause the problem of high pressure measurement data when measuring pressure in the wellbore. Summary of the invention

[0004] The purpose of the present invention is to provide a formation pressure measurement method to solve the problem that the current formation pressure measurement method is easily affected by the well-injected well-injected fluid when performing formation pressure measurement in a wellbore injected with well-injected fluid, resulting in inaccurate pressure measurement data; the purpose of the present invention is also to provide a formation pressure measurement string to solve the above problem.

[0005] The technical solution of the formation pressure measurement method of the present invention is: A formation pressure measurement method comprises the following steps: lowering a pressure measuring pipe string having an upper lumen and a lower lumen into a wellbore filled with a well-killing fluid, isolating the annulus between the pressure measuring pipe string and the wellbore above the formation to be pressure-measured, so that the upper lumen of the pressure measuring pipe string is separated from the lower lumen, and the lower lumen is connected to the formation to be pressure-measured, sucking out the well-killing fluid in the lower lumen of the pressure measuring pipe string, guiding the formation fluid to flow from the formation into the wellbore, and measuring the pressure in the lower lumen of the pressure measuring pipe string or the wellbore pressure below the isolation position to obtain the formation pressure.

[0006] Advantages of the formation pressure measurement method of the present invention: The present invention pioneeringly provides a method suitable for measuring the formation pressure in a wellbore filled with kill fluid. By sealing the annulus between the pressure measurement string and the wellbore and separating the upper and lower cavities of the pressure measurement string, the lower cavity communicates with the space below the sealing position and the formation, while the upper cavity and the space above the sealing position are isolated from the formation. Thus, when sucking the kill fluid in the lower cavity of the pressure measurement string, formation fluid can flow into the wellbore under the action of the suction force. The pressure in the lower cavity of the pressure measurement string and the wellbore below the sealing position is equal to the formation pressure, and the hydrostatic pressure of the kill fluid in the upper cavity and the space above the sealing position is separated from the pressure in the lower cavity and the space below the sealing position. Measuring the pressure in the lower cavity of the pressure measurement string or the pressure in the wellbore below the sealing position can obtain the formation pressure, avoiding the influence of the kill fluid in the wellbore and improving the accuracy of formation pressure measurement.

[0007] The technical solution of the formation pressure measurement string of the present invention is as follows: A formation pressure measurement string, which includes a tubing string and a pressure measurement element, and also includes a packer and a liquid extractor. The packer is used to seal the annulus between the pressure measurement string and the wellbore above the formation to be measured. The liquid extractor includes a cylinder body and a piston disposed in the cylinder body. The cylinder body is connected to the tubing string. The piston divides the inner cavity of the pressure measurement string into an upper cavity and a lower cavity. The piston can move upward relative to the cylinder body or the cylinder body can move downward relative to the piston to suck the kill fluid in the lower cavity of the pressure measurement string, so that formation fluid flows from the formation into the wellbore. The pressure measurement element is disposed in the part of the pressure measurement string forming the lower cavity.

[0008] Further, the liquid extractor includes an outer cylinder and an inner tube. The outer cylinder forms the cylinder body. The piston is disposed at the upper end of the inner tube. The lower end of the outer cylinder is provided with an inner ring platform. The inner tube passes through the central hole of the inner ring platform. The piston is located above the inner ring platform and has an end face facing the inner ring platform to form a negative pressure suction cavity between the piston and the inner ring platform when the piston and the cylinder body move relative to each other. The inner tube is provided with a communication hole below the piston for communicating with the negative pressure suction cavity. The upper cavity includes the space in the outer cylinder above the piston, and the lower cavity includes the space in the inner tube below the piston.

[0009] Further, the inner tube is provided with an upward abutting surface below the inner ring platform. A spring is sleeved outside the inner tube. The upper end of the spring abuts against the lower end face of the inner ring platform, and the lower end abuts against the upward abutting surface.

[0010] Further, the inner tube includes a main body. The piston is disposed at the upper end of the main body. The lower end of the main body is provided with a lower joint. The upward abutting surface is disposed on the lower joint.

[0011] Further, the outer cylinder includes a main cylinder body. A sealing ring is connected to the inner wall of the lower end of the main cylinder body. The sealing ring forms the inner ring platform.

[0012] Further, the piston includes a piston body that slidably cooperates with the cylinder block. The piston body has a central hole that can communicate the upper and lower cavities. A blocking body is movably provided on the piston body to block the central hole and separate the upper and lower cavities.

[0013] Further, the blocking body is a sphere, and the piston body is provided with a sealing surface that seals and cooperates with the sphere.

[0014] Further, the oil pipe includes a lower connecting pipe connected to the lower end of the liquid extractor, and a check valve structure for allowing liquid to flow upward is provided in the lower connecting pipe.

[0015] Further, the oil pipe includes a lower connecting pipe connected to the lower end of the liquid extractor. The lower cavity includes the inner cavity of the lower connecting pipe. A plug is provided on the lower side of the lower connecting pipe, and the pressure measuring element is supported on the plug.

[0016] Beneficial effects of the formation pressure measuring string of the present invention: The present invention is improved on the basis of the formation pressure measuring string in the prior art. The annular space between the pressure measuring string and the wellbore is sealed by a packer, and the piston of the liquid extractor is used to separate the upper and lower cavities of the pressure measuring string, so that the lower cavity communicates with the space below the packer and the formation, while the upper cavity and the space above the packer are isolated from the formation. By the relative movement of the piston and the cylinder block, the volume of the lower cavity of the pressure measuring string is increased, thereby sucking the kill fluid in the lower cavity of the pressure measuring string. Furthermore, the formation fluid can flow into the wellbore under the action of the suction force. The pressure in the lower cavity of the pressure measuring string and the wellbore below the packer is equal to the formation pressure, while the hydrostatic pressure of the kill fluid in the upper cavity and the space above the packer is separated from the pressure in the lower cavity and the space below the packer. Measuring the pressure in the lower cavity of the pressure measuring string or the pressure in the wellbore below the packer can obtain the formation pressure, avoiding the influence of the kill fluid in the wellbore and improving the accuracy of formation pressure measurement. It is suitable for formation pressure measurement in a wellbore filled with kill fluid. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of an embodiment of the formation pressure measuring string of the present invention; Figure 2 is Figure 1 the schematic structural diagram of the liquid extractor in Figure 3 is Figure 2 the partial structural schematic diagram at the piston in

[0018] In the figure: 101, upper connecting pipe; 102, liquid extractor; 103, packer; 104, second valve ball; 105, pressure measuring element; 106, screen pipe; 107, plug; 108, lower connecting pipe; 200, casing; 300, upper oil-casing annulus; 400, upper formation; 500, lower formation; 600, lower oil-casing annulus; 1, upper joint; 2, first sealing ring; 3, main cylinder body; 4, first valve ball; 5, piston main body; 6, second sealing ring; 7, communication hole; 8, sealing ring; 9, third sealing ring; 10, main pipe body; 11, spring; 12, lower joint. Detailed implementation mode

[0019] The formation pressure measuring string of the present invention seals the annulus between the pressure measuring string and the wellbore through a packer, and uses the piston of the liquid extractor to separate the upper pipe cavity and the lower pipe cavity of the pressure measuring string, so that the lower pipe cavity communicates with the space below the packer and the formation, while the upper pipe cavity and the space above the packer are isolated from the formation. By the relative movement of the piston and the cylinder body, the volume of the lower pipe cavity of the pressure measuring string is increased, so as to suck the kill fluid in the lower pipe cavity of the pressure measuring string. Furthermore, the formation fluid can flow into the wellbore under the action of the suction force. The pressure in the lower pipe cavity of the pressure measuring string and the wellbore below the packer is equal to the formation pressure, while the hydrostatic pressure of the kill fluid in the upper pipe cavity and the space above the packer is separated from the pressure in the lower pipe cavity and the space below the packer. Measuring the pressure in the lower pipe cavity of the pressure measuring string or the pressure in the wellbore below the packer can obtain the formation pressure, avoiding the influence of the kill fluid in the wellbore and improving the accuracy of formation pressure measurement. It is suitable for formation pressure measurement in a wellbore filled with kill fluid.

[0020] An embodiment of the formation pressure measuring string of the present invention: Such as Figure 1 、 Figure 2 And Figure 3 As shown in the figure, the formation pressure measuring string is used to be lowered into the wellbore to measure the pressure of the formation to be measured. The formation has an upper formation 400 and a lower formation 500. The formation to be measured in this embodiment is the lower formation 500. There is a casing 200 in the wellbore, and an oil-casing annulus is formed between the casing 200 and the formation pressure measuring string.

[0021] The formation pressure measuring string includes a tubing string, a pressure measuring element 105, a packer 103 and a liquid extractor 102. The tubing string includes an upper connecting pipe 101 and a lower connecting pipe 108. The liquid extractor 102 is above the packer 103. The lower end of the upper connecting pipe 101 is connected to the liquid extractor 102. The upper end of the lower connecting pipe 108 is connected to the liquid extractor 102, and the lower end is connected to a screen pipe 106. A plug 107 is connected to the lower end of the screen pipe 106. The screen pipe 106 is used to face the middle of the lower formation 500 for the formation fluid to flow in. The pressure measuring element 105 is located in the screen pipe 106 and supported on the plug 107 to measure the formation fluid pressure.

[0022] The liquid extractor 102 includes an outer cylinder and an inner tube. The outer cylinder includes a main cylinder body 3. An upper joint 1 is provided at the upper end of the main cylinder body 3, and a sealing ring 8 is provided at the lower end. The inner tube includes a main tube body 10. A piston is provided at the upper end of the main tube body 10, and a lower joint 12 is provided at the lower end. The piston includes a piston main body 5 and a first valve ball 4. The upper joint 1 is connected to the upper connecting pipe 101, and the lower joint 12 is connected to the lower connecting pipe 108. The lower connecting pipe 108 is connected to a packer 103. The packer 103 is a hydraulic setting bi-directional slip packer. The packer 103 is used to seal the annulus between the pressure measuring string and the wellbore above the formation to be pressure measured. The distance between the packer 103 and the formation to be pressure measured is not greater than 10 m. The annulus above the packer 103 is the upper casing-tubing annulus 300, and the annulus below the packer 103 is the lower casing-tubing annulus 600. The outer cylinder forms a cylinder body. The piston is located in the main cylinder body 3 of the outer cylinder. The inner cavity of the pressure measuring string includes the inner cavity of the liquid extractor 102 and the inner cavity of the tubing. The piston divides the inner cavity of the pressure measuring string into an upper cavity and a lower cavity. The lower cavity communicates with the space below the packer 103 and the formation. The cylinder body can move downward relative to the piston to suck the kill fluid in the lower cavity of the pressure measuring string so that the formation fluid flows from the formation into the wellbore. A pressure measuring element 105 is arranged in the lower cavity to facilitate measuring the pressure in the lower cavity and thus obtaining the formation pressure.

[0023] The upper joint 1 has a central hole that penetrates up and down. An internal thread is provided at the upper end of the upper joint 1 for connection with the upper connecting pipe 101. An external thread and a sealing ring mounting groove are provided at the lower end of the upper joint 1. An internal thread is provided at the upper end of the main cylinder body 3 for threaded connection with the lower end of the upper joint 1. A first sealing ring 2 is arranged in the sealing ring mounting groove at the lower end of the upper joint 1 to make the upper joint 1 and the main cylinder body 3 in sealed connection. The upper joint 1 that is in sealed threaded connection with the main cylinder body 3 facilitates the adapter connection with the upper connecting pipe 101 of the tubing.

[0024] The inner wall of the main cylinder body 3 is smooth. An internal thread is provided at the lower end of the main cylinder body 3. An external thread is provided on the sealing ring 8. The sealing ring 8 is threadedly connected to the lower end of the main cylinder body 3 and is located inside the main cylinder body 3. The sealing ring 8 is sealed with the main cylinder body 3. The sealing ring 8 forms an inner annular platform of the outer cylinder opposite to the piston. Two sealing ring mounting grooves are provided on the inner peripheral surface of the sealing ring 8, and third sealing rings 9 are installed in the sealing ring mounting grooves at this place for sealing the outer peripheral surface of the main tube body 10.

[0025] The upper end of the main pipe body 10 is provided with an external thread. The piston main body 5 has a central hole that penetrates up and down. The central hole of the piston main body 5 includes an upper tapered hole section and a lower connecting hole section. The lower connecting hole section is provided with an internal thread to connect the piston main body 5 to the upper end of the main pipe body 10. The tapered surface of the upper tapered hole section constitutes a valve seat. When the first valve ball 4 lands on the valve seat, it can block the central hole of the piston main body 5. The central hole of the piston main body 5 constitutes a through hole that can communicate the upper pipe cavity and the lower pipe cavity of the test string. The outer diameter of the piston main body 5 is adapted to the inner diameter of the main cylinder body 3 to facilitate the relative sliding of the piston and the main cylinder body 3. Two seal ring installation grooves are provided on the outer peripheral surface of the piston main body 5, and a second seal ring 6 is installed in the seal ring installation grooves at this place, so as to form a seal between the outer peripheral surface of the piston main body 5 and the inner peripheral surface of the main cylinder body 3.

[0026] The main pipe body 10 passes through the central hole of the seal ring 8. When the outer cylinder slides downward relative to the inner pipe, the seal between the seal ring 8 and the main pipe body 10 can be maintained through the third seal ring 9, and the seal between the piston main body 5 and the main cylinder body 3 can be maintained through the second seal ring 6. The lower end of the main pipe body 10 is provided with an external thread. The lower joint 12 has a central hole that penetrates up and down. The upper end of the lower joint 12 is provided with an internal thread to be threadedly connected to the lower end of the main pipe body 10. The lower end of the lower joint 12 is provided with an external thread for connecting to the lower connecting pipe 108 of the oil pipe. A spring 11 is sleeved outside the main pipe body 10. The spring 11 is a compression spring. The spring 11 is located between the seal ring 8 and the lower joint 12. The upper end of the spring 11 abuts against the lower end surface of the seal ring 8, and the lower end abuts against the upper end surface of the lower joint 12. The upper end surface of the lower joint 12 constitutes an upward abutting surface, which is convenient for installing the spring 11. Under the action of the elastic force of the spring 11, the lower end surface of the piston main body 5 can be tightly abutted against the upper end surface of the seal ring 8 without moving the outer cylinder downward, avoiding the relative movement of the inner pipe and the outer cylinder during the process of lowering the test string into the wellbore.

[0027] The lower end face of the piston body 5 faces the sealing ring 8. When the piston body 5 and the main cylinder 3 move relative to each other, the piston body 5 and the sealing ring 8 are separated from each other to form a negative pressure suction cavity therebetween. The negative pressure suction cavity is an annular cavity surrounded by the piston body 5, the sealing ring 8, the main cylinder 3, and the main pipe body 10. A communication hole 7 for communicating with the negative pressure suction cavity is provided on the main pipe body 10 at a position below the piston body 5 and adjacent to the piston body 5. The communication hole 7 is used to communicate the inner cavity of the main pipe body 10 with the negative pressure suction cavity. The inner cavity of the main pipe body 10 has a space located below the piston. The upper pipe cavity of the test string includes the space above the piston in the outer cylinder and the inner cavity of the upper connecting pipe 101 of the tubing. The lower pipe cavity includes the space below the piston in the inner pipe and the inner cavity of the lower connecting pipe 108 of the tubing. When the first valve ball 4 does not fall onto the valve seat, the central hole of the piston body 5 can communicate the upper pipe cavity and the lower pipe cavity, facilitating the lowering of the test string into the wellbore. The first valve ball 4 constitutes a plugging body for plugging the central hole of the piston body 5 to separate the upper pipe cavity and the lower pipe cavity. The plugging body is a sphere, and the upper tapered hole section of the piston body 5 constitutes a sealing surface for sealingly cooperating with the sphere, which can separate the liquid column in the upper pipe cavity of the test string from the lower space, avoiding the influence of the upper liquid column pressure on the formation pressure measurement.

[0028] During use, the first valve ball 4 does not go down the well together with the pressure measurement string first. After the pressure measurement string is lowered into the wellbore to a set position and the packer 103 is set above the formation, the first valve ball 4 is dropped. After the first valve ball 4 falls onto the valve seat, the string is continued to be lowered. The upper tubing of the liquid extractor 102 drives the outer cylinder to move downward. Under the fixing action of the packer 103, the inner pipe does not move. The sealing ring 8 compresses the spring 11 downward and separates from the piston. The annular volume between the outer cylinder and the inner pipe between the sealing ring 8 and the piston increases, forming a negative pressure suction cavity. And the communication hole 7 communicates the negative pressure suction cavity with the lower pipe cavity below the piston, and can extract the fluid in the formation below the packer 103. After the formation fluid flows into the wellbore from the formation, the well is shut in. In this way, the pressure in the wellbore below the packer 103 is equal to the formation pressure. And because the first valve ball 4 and the valve seat at the piston of the liquid extractor 102 form a check valve structure, the liquid column pressure in the upper pipe cavity is cut off from the pressure in its lower pipe cavity. The pressure measurement element 105 is arranged in the lower connecting pipe 108 and can measure the pressure in the lower pipe cavity. The lower pipe cavity communicates with the formation, so as to obtain the formation pressure, avoid the influence of the kill fluid in the wellbore on the formation pressure, and improve the accuracy of formation pressure measurement.

[0029] A check valve structure for upward liquid flow is also provided inside the lower connecting pipe 108. The check valve structure includes a ball seat fixed on the inner wall of the lower connecting pipe 108 and a second valve ball 104. The ball seat is below the packer 103 and above the screen pipe 106. By using the check valve structure in the liquid extractor 102 in cooperation with the check valve structure in the lower connecting pipe 108, the pipe string can be lifted and lowered multiple times for liquid extraction. After the first lowering of the pipe string to lower the outer cylinder of the liquid extractor 102 for liquid extraction, the pipe string can be lifted again to raise the outer cylinder of the liquid extractor 102 (the lifting distance is less than the original lowering distance). When lifting, the piston remains stationary and the sealing ring 8 moves upward. The annular space volume between the outer cylinder and the inner pipe between the sealing ring 8 and the piston decreases. Due to the existence of the check valve structure in the lower connecting pipe 108, the liquid pressure in the annular space between the outer cylinder and the inner pipe between the sealing ring 8 and the piston increases, and through the communication hole 7, it pushes open the first valve ball 4 and is discharged into the upper tubing of the liquid extractor 102. Lowering the pipe string again can extract liquid again, which is beneficial to ensuring the entry of formation fluid into the wellbore.

[0030] The formation pressure measuring pipe string in this embodiment is used for measuring the pressure of the lower formation. In other embodiments, it can also be used for the combined measurement of the whole well, and the packer is set above the upper formation.

[0031] In other embodiments, the cylinder body of the liquid extractor can also be fixedly connected to the lower connecting pipe, and a pumping rod is connected above the piston. The pumping rod is used to drive the piston to move upward relative to the cylinder body to suck the kill fluid in the lower pipe cavity below the piston.

[0032] In other embodiments, a plugging cover can also be hinged on the piston body. The plugging cover can be turned upward to open the central hole of the piston body, and when covering the piston body, it plugs its central hole. The plugging cover constitutes a plugging body.

[0033] In other embodiments, the spring can also be omitted, and the sealing ring is pre-fixed to the main pipe body by shear pins. When the outer cylinder is lowered, the shear pins are cut off and the outer cylinder moves downward relative to the piston.

[0034] In other embodiments, an annular platform is integrally provided on the outer peripheral surface of the main pipe body, and an upward abutting surface is provided on the annular platform.

[0035] In other embodiments, the main cylinder body and the sealing ring can also be integrally provided.

[0036] In other embodiments, the upper joint can also be omitted, and the main cylinder body is directly threadedly connected to the upper connecting pipe.

[0037] In other embodiments, the pressure measuring element can also be provided on the outer wall of the lower connecting pipe to measure the wellbore pressure below the packer, that is, the pressure in the lower oil casing annulus.

[0038] In other embodiments, the check valve structure in the lower connecting pipe can also be cancelled, and this is applicable to the case of only one liquid extraction.

[0039] Embodiment of the formation pressure measurement method of the present invention: The formation pressure measurement method can adopt the formation pressure measurement string of the above embodiment. Lower the pressure measurement string with an upper lumen and a lower lumen into the wellbore filled with kill fluid. Seal the annulus between the pressure measurement string and the wellbore above the formation to be pressure measured. Use the piston of the extractor of the formation pressure measurement string to separate the upper lumen and the lower lumen of the pressure measurement string. The lower lumen is connected to the formation to be pressure measured. The piston of the extractor moves relative to the cylinder body to suck the kill fluid in the lower lumen of the pressure measurement string, guide the formation fluid to flow from the formation into the wellbore, and measure the pressure in the lower lumen of the pressure measurement string to obtain the formation pressure. In other embodiments, the formation pressure can also be obtained by measuring the wellbore pressure below the sealing position. This method is suitable for formation pressure measurement in a wellbore filled with kill fluid. By sealing the annulus between the pressure measurement string and the wellbore and separating the upper lumen and the lower lumen of the pressure measurement string, the lower lumen is connected to the space below the sealing position and the formation, while the upper lumen and the space above the sealing position are isolated from the formation. Thus, when sucking the kill fluid in the lower lumen of the pressure measurement string, the formation fluid can flow into the wellbore under the action of the suction force. The pressure in the lower lumen of the pressure measurement string and the wellbore pressure below the sealing position are equal to the formation pressure, while the hydrostatic pressure of the kill fluid in the upper lumen and the space above the sealing position is separated from the pressure in the lower lumen and the space below the sealing position. Measuring the pressure in the lower lumen of the pressure measurement string or the wellbore pressure below the sealing position can obtain the formation pressure, avoiding the influence of the kill fluid in the wellbore and improving the accuracy of formation pressure measurement.

[0040] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still make modifications to the technical solutions recorded in the foregoing embodiments without creative efforts, or make equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A formation pressure measurement method, characterized in that: A pressure measuring string having an upper lumen and a lower lumen is lowered into a wellbore filled with a well-killing fluid, and the annulus between the pressure measuring string and the wellbore is isolated above the formation to be pressure-tested, so that the upper lumen of the pressure measuring string is separated from the lower lumen, and the lower lumen is connected to the formation to be pressure-tested. The well-killing fluid in the lower lumen of the pressure measuring string is sucked out to guide the formation fluid to flow from the formation into the wellbore, and the formation pressure can be obtained by measuring the pressure in the lower lumen of the pressure measuring string or the wellbore pressure below the isolation position.

2. A formation pressure measuring string, comprising an oil pipe and a pressure measuring element, characterized in that: It also includes a packer and a pump. The packer is used to seal the annulus between the pressure measuring pipe string and the wellbore above the formation to be pressure-measured. The pump includes a cylinder body and a piston arranged in the cylinder body. The cylinder body is connected to the oil pipe. The piston separates the inner cavity of the pressure measuring pipe string into an upper cavity and a lower cavity. The piston can move upward relative to the cylinder body or the cylinder body can move downward relative to the piston to suck the well-pressure fluid in the lower cavity of the pressure measuring pipe string to allow the formation fluid to flow from the formation into the wellbore. The pressure measuring element is arranged on the part of the pressure measuring pipe string that forms the lower cavity.

3. The formation pressure measuring string according to claim 2, characterized in that: The liquid pump includes an outer tube and an inner tube, the outer tube constitutes a cylinder body, the piston is arranged at the upper end of the inner tube, the lower end of the outer tube is provided with an inner ring platform, the inner tube passes through the central hole of the inner ring platform, the piston is located above the inner ring platform and has an end face facing the inner ring platform to form a negative pressure suction chamber between the piston and the inner ring platform when the piston and the cylinder body move relative to each other, and a connecting hole for communicating with the negative pressure suction chamber is provided on the inner tube below the piston, the upper tube cavity includes the space in the outer tube above the piston, and the lower tube cavity includes the space in the inner tube below the piston.

4. The formation pressure measuring string according to claim 3, characterized in that: An upward abutting surface is arranged on the inner tube below the inner ring stage, and a spring is sleeved outside the inner tube, the upper end of the spring abuts against the lower end surface of the inner ring stage, and the lower end abuts against the upward abutting surface.

5. The formation pressure measuring string according to claim 4, characterized in that: The inner tube comprises a main tube body, a piston is arranged at the upper end of the main tube body, a lower joint is arranged at the lower end of the main tube body, and the upward abutting surface is arranged on the lower joint.

6. The formation pressure measuring string according to claim 3, 4 or 5, characterized in that: The outer cylinder comprises a main cylinder body, and a sealing ring is connected to the inner wall of the lower end of the main cylinder body, and the sealing ring constitutes the inner ring platform.

7. The formation pressure measuring string according to any one of claims 2 to 5, characterized in that: The piston comprises a piston body which is slidably matched with the cylinder body, the piston body has a through hole which can connect the upper tube cavity with the lower tube cavity, and a blocking body which is movably provided on the piston body for blocking the through hole to separate the upper tube cavity from the lower tube cavity.

8. The formation pressure measuring string according to claim 7, characterized in that: The blocking body is a sphere, and a sealing surface which cooperates with the sphere in a sealing manner is arranged on the piston body.

9. The formation pressure measuring string according to claim 7, characterized in that: The oil pipe comprises a lower connecting pipe connected to the lower end of the liquid extractor, and a check valve structure for allowing liquid to flow upward is arranged in the lower connecting pipe.

10. The formation pressure measuring string according to any one of claims 2 to 5, characterized in that: The oil pipe comprises a lower connecting pipe connected to the lower end of the pump, the lower pipe cavity comprises an inner cavity of the lower connecting pipe, a thread plug is arranged on the lower side of the lower connecting pipe, and a pressure measuring element is supported on the thread plug.

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