Device and method for testing underground stress of sucker rod

Abstract

The invention belongs to the technical field of sucker rod stress measurement, and particularly discloses an underground stress testing device and method for a sucker rod. Comprising an upper connector, a center rod, an axial force testing short section and a lower connector which are sequentially connected from top to bottom, the upper end of the upper connector is used for being fixedly connected with the upper end of a sucker rod, and the lower end of the lower connector is used for being fixedly connected with the lower end of the sucker rod; the outer side of the center rod is sleeved with a movable block, a plurality of liquid passing holes are formed in the movable block, and four load sensors are evenly arranged on the same plane between the center rod and the movable block. And an axial force sensor and an acceleration sensor are arranged in the axial force testing short section. The test data comprises axial and lateral stress change conditions, the motion trail of the sucker rod and the like at the same time. And meanwhile, the device adopts direct testing, so that the testing result is more accurate compared with the prior art. And more accurate and comprehensive measured data can be provided for stress analysis of the sucker rod string.

Description

Technical Field

[0001] The present invention belongs to the technical field of sucker rod force measurement, and particularly relates to a downhole sucker rod force test device and method. Background Art

[0002] In oil extraction, the rod pump - pumping unit system is currently the most main lifting method. Due to the influence of complex wellbore trajectories and the influence of factors such as the instability deformation of the lower sucker rod string during the downstroke of the pumping unit, the phenomena of eccentric wear and breakage of the rod and tubing are inevitable. This will increase the workload of workover operations, maintenance costs, and development costs. The main prevention and control measures for rod and tubing optimization and anti - eccentric wear are, on the basis of optimizing the rod string combination, adding wear - resistant centralizers in the well sections with large full - angle change rate and complex forces, etc., to delay the eccentric wear of the tubing and rod and improve the service life. Therefore, the force analysis of the rod string is the core of rod string design, centralization, and anti - wear. However, the existing rod string force analysis is currently calculated under assumed conditions and lacks effective field measurement verification, posing challenges to the accuracy of the rod string mechanical model and optimization design. Therefore, it is necessary to conduct field measurement and analysis on the downhole force condition of the rod string.

[0003] Existing sucker rod force measurement devices generally adopt the form of a short tubing joint. This method can only obtain the lateral force contact force between the rod and tubing and cannot measure the change in the axial force of the sucker rod. This device and method can only measure the lateral force at the moment of contact between the sucker rod and the tubing and cannot determine the motion state of the sucker rod.

[0004] Existing technologies also calculate the axial force and lateral force by indirect measurement methods, but there are certain errors in this method, and it is difficult to obtain accurate data. Summary of the Invention

[0005] The purpose of the present invention is to provide a downhole sucker rod force test device and method to solve the technical problems of incomplete and inaccurate sucker rod force measurement.

[0006] To achieve the above - mentioned purpose, the present invention is implemented by adopting the following technical solutions:

[0007] In the first aspect, the present invention provides a downhole sucker rod force test device, including an upper joint, a central rod, an axial force test short joint, and a lower joint connected in sequence from top to bottom. The upper end of the upper joint is used for fixedly connecting with the upper end of the sucker rod, and the lower end of the lower joint is used for fixedly connecting with the lower end of the sucker rod;

[0008] An activity block is sleeved outside the central rod. A plurality of liquid - passing holes are provided on the activity block, and four load sensors are evenly arranged on the same plane between the central rod and the activity block;

[0009] An axial force sensor and an acceleration sensor are arranged inside the axial force test short joint.

[0010] A further improvement of the present invention lies in that: a control circuit and a power supply are provided inside the lower joint, and the battery is used to supply power to the control circuit, the load sensor, the axial force sensor and the acceleration sensor;

[0011] The control circuit is electrically connected to the load sensor, the axial force sensor and the acceleration sensor respectively, and is used to obtain the data of each sensor and calculate the stress condition of the sucker rod.

[0012] A further improvement of the present invention lies in that: the upper joint, the central rod, the axial force test short section and the lower joint are fixedly connected by screw threads between adjacent two of them.

[0013] A further improvement of the present invention lies in that: the inner diameter of the movable block is smaller than the outer diameter of the upper joint, and the inner diameter of the movable block is also smaller than the outer diameter of the axial force test short section.

[0014] A further improvement of the present invention lies in that: chamfers are provided on both the upper end surface and the lower end surface of the movable block.

[0015] A further improvement of the present invention lies in that: a number of liquid passing holes are evenly formed in the movable block.

[0016] A further improvement of the present invention lies in that: the inner diameter of the movable block is larger than the sum of the outer diameter of the central rod and twice the width of the load sensor.

[0017] A further improvement of the present invention lies in that: the control circuit is also used to store data and upload the data to the ground control terminal.

[0018] A further improvement of the present invention lies in that: the chamfer is 45°.

[0019] In a second aspect, the present invention provides a method for testing the stress of a sucker rod underground, based on the above-mentioned device for testing the stress of a sucker rod underground, including the following steps:

[0020] Fix the top of the upper joint to the upper end of the sucker rod, fix the bottom of the lower joint to the lower end of the sucker rod, and then the sucker rod works underground;

[0021] The liquid in the well drives the movable block to move, thereby squeezing the load sensor to obtain the lateral force received by the sucker rod;

[0022] Obtain the axial force magnitude and acceleration through the axial force sensor and the acceleration sensor in the axial force test short section, and calculate the speed and movement trajectory of the sucker rod according to the axial force magnitude and acceleration to complete the stress test.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The present invention provides a downhole stress testing device and method for sucker rods, which have the following new technical features compared with the prior art:

[0025] 1. The device has a delicate structure and is easy to install. Its shape is similar to that of a conventional sucker rod centralizer, and it can be directly installed in the well section to be tested of the sucker rod string and lowered into the well together with the sucker rod string without the need for other devices.

[0026] 2. The device can simultaneously measure the changes in axial force, lateral force, and the corresponding speed and movement trajectory at the test position of the sucker rod string within one pumping unit movement cycle. Compared with the prior art, the stress conditions of the sucker rod measured by this device are more comprehensive, and the test data includes both axial and lateral stress changes and the movement trajectory of the sucker rod. At the same time, all tests of this device are direct tests, and the test results are more accurate than those of the prior art. It can provide more accurate and comprehensive measured data for the stress analysis of the sucker rod string.

[0027] 3. The present invention is installed in the well section to be tested of the sucker rod string and is lowered into the wellbore together with it. It reciprocates up and down with the sucker rod during the normal operation of the pumping unit. When working downhole, it can simultaneously and continuously test and record the lateral force, axial force, and rod string acceleration of the rod-tube contact in different directions at the well section where the test device is located. By calculation and inversion, the changes in lateral force, axial force, and the axial movement state of the rod string at different times and different azimuths can be obtained, which will provide important measured data for the correction of the rod string mechanical model and the optimization design of the rod string. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments and descriptions thereof of the invention are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] In the drawings:

[0030] Figure 1 is a schematic structural diagram of a downhole stress testing device for sucker rods according to the present invention;

[0031] Figure 2 is a cross-sectional view of a downhole stress testing device for sucker rods according to the present invention;

[0032] Figure 3 is a stress analysis diagram in a downhole stress testing device for sucker rods according to the present invention;

[0033] In the figure: upper joint 1, central rod 2, movable block 3, load sensor 4, liquid passing hole 5, axial force test short joint 6, axial force sensor 7, acceleration sensor 8, lower joint 9, control circuit 10, and power supply 11. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0035] The following detailed descriptions are all exemplary descriptions, aiming to provide further details of the present invention. Unless otherwise specified, all technical terms adopted in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0036] Embodiment 1

[0037] A downhole stress testing device for sucker rods, as Figures 1-2 shown, includes: an upper joint 1, a central rod 2, an axial force testing short section 6, and a lower joint 9 that are connected in sequence from top to bottom;

[0038] The top of the upper joint 1 is connected to the upper end of the sucker rod, and the lower end of the lower joint 9 is connected to the lower end of the sucker rod;

[0039] A movable block 3 is sleeved outside the central rod 2. A plurality of liquid passing holes 5 are formed in the movable block 3. Four load sensors 4 are evenly arranged on the same plane between the central rod 2 and the movable block 3;

[0040] An axial force sensor 7 and an acceleration sensor 8 are arranged inside the axial force testing short section 6;

[0041] A control circuit 10 and a battery 11 are arranged inside the lower joint 9. The battery is used to supply power to the control circuit 10, the load sensors 4, the axial force sensor 7, and the acceleration sensor 8;

[0042] The control circuit 10 is electrically connected to the load sensors 4, the axial force sensor 7, and the acceleration sensor 8 respectively, and is used to obtain the data of each sensor and calculate the stress condition of the sucker rod;

[0043] Specifically, the upper joint 1, the central rod 2, the axial force testing short section 6, and the lower joint 9 are fixedly connected by screw threads between adjacent ones;

[0044] Specifically, the inner diameter of the movable block 3 is smaller than the outer diameter of the upper joint 1, and the inner diameter of the movable block 3 is also smaller than the outer diameter of the axial force testing short section 6, so that the movable block 3 always slides within the length range of the central rod 2, but the movable block 3 can rotate around the central rod 2;

[0045] Specifically, the inner diameter of the movable block 3 is slightly larger than the outer diameter of the central rod 2, so as to leave an installation space for the load sensors 4;

[0046] Specifically, chamfers are provided on both the upper and lower end faces of the movable block 3, and the chamfer angle is preferably 45°, thereby reducing the impact and resistance suffered during the up and down movement of the movable block 3;

[0047] Specifically, a liquid passing hole 5 is provided in the movable block 3 to ensure a certain liquid passing area;

[0048] Specifically, the lateral force of the oil pipe in contact with the sucker rod is transmitted to the load sensor 4 through the movable block 3. For the lateral force in any direction on the plane, the inner wall of the central hole of the movable block contacts 1 to 2 adjacent load sensors 4 on the central rod 2. From the magnitudes of the two-direction loads measured by the load sensor 4, as Figure 3 shown, through the force synthesis rule, the magnitude F of the lateral force in any direction can be calculated all and the direction α. The calculation formula is as follows:

[0049]

[0050] α = arccos(F A / F all ) × 180 / π.

[0051] Specifically, the control circuit is also used to implement functions such as working system execution, test data signal processing, recording, storage, and communication. Through processing such as data amplification, filtering, and digital-to-analog conversion, the force conditions of the sucker rod in the test well section at different times and in different directions can be obtained.

[0052] During operation, it is installed in the well section of the sucker rod string to be tested and is lowered into the wellbore together with the sucker rod. It reciprocates up and down together with the sucker rod as the pumping unit operates normally.

[0053] Specifically, inside the axial force test sub-section 6, there is an axial force sensor 7 and an acceleration sensor 8, which can simultaneously measure the axial force and acceleration at the location. Through calculation, the velocity v and the motion trajectory S of the sucker rod in this well section within the time period from t1 to t2 can be obtained.

[0054]

[0055] Embodiment 2

[0056] A method for testing the downhole force of a sucker rod, based on a downhole force testing device for a sucker rod in Embodiment 1, includes the following steps:

[0057] Fix the top of the upper joint 1 to the upper end of the sucker rod, fix the bottom of the lower joint 9 to the lower end of the sucker rod, and then lower the sucker rod into the well for operation;

[0058] The liquid in the well drives the movable block 3 to move, thereby squeezing the load sensor 4 to obtain the lateral force received by the sucker rod;

[0059] The axial force magnitude and acceleration are obtained by means of the axial force sensor 7 and the acceleration sensor 8 within the short joint 6 through axial force testing. The speed and motion trajectory of the sucker rod are calculated based on the axial force magnitude and acceleration, thereby completing the force testing.

[0060] As is known by common technical knowledge, the present invention can be implemented by other embodiments that do not depart from its spiritual essence or essential features. Therefore, the above-disclosed embodiments are illustrative in all aspects and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific implementation manners of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A downhole stress testing device for sucker rods, characterized in that, It includes an upper joint (1), a central rod (2), an axial force test sub - section (6), and a lower joint (9) that are connected in sequence from top to bottom. The upper end of the upper joint (1) is used for fixedly connecting with the upper end of the sucker rod, and the lower end of the lower joint (9) is used for fixedly connecting with the lower end of the sucker rod. An active block (3) is sleeved outside the central rod (2). A number of liquid - passing holes (5) are opened on the active block (3). Four load sensors (4) are evenly arranged on the same plane between the central rod (2) and the active block (3). An axial force sensor (7) and an acceleration sensor (8) are arranged inside the axial force test sub - section (6).

2. The downhole stress testing device for sucker rods according to claim 1, characterized in that, A control circuit (10) and a power source (1) are arranged inside the lower joint (9). The battery is used to supply power to the control circuit (10), the load sensors (4), the axial force sensor (7), and the acceleration sensor (8). The control circuit (10) is electrically connected to the load sensors (4), the axial force sensor (7), and the acceleration sensor (8) respectively, and is used to obtain the data of each sensor and calculate the force condition of the sucker rod.

3. The downhole stress testing device for sucker rods according to claim 1, characterized in that, The upper joint (1), the central rod (2), the axial force test sub - section (6), and the lower joint (9) are fixedly connected by screw threads between adjacent two of them.

4. The downhole stress testing device for sucker rods according to claim 1, wherein The inner diameter of the active block (3) is smaller than the outer diameter of the upper joint (1), and the inner diameter of the active block (3) is also smaller than the outer diameter of the axial force test sub - section (6).

5. The downhole stress testing device for sucker rods according to claim 1, characterized in that, Chamfers are provided on both the upper end face and the lower end face of the active block (3).

6. The downhole stress testing device for sucker rods according to claim 1, characterized in that A number of liquid - passing holes (5) are evenly opened on the active block (3).

7. The downhole stress testing device for sucker rods according to claim 1, characterized in that, The inner diameter of the active block (3) is larger than the sum of the outer diameter of the central rod (2) and twice the width of the load sensors (4).

8. The downhole stress testing device for sucker rods according to claim 2, characterized in that, The control circuit (10) is also used to store data and upload the data to the ground control terminal.

9. The downhole stress testing device for sucker rods according to claim 5, wherein, The chamfer is 45°.

10. A method for testing the downhole force of a sucker rod, based on the downhole force testing device for a sucker rod according to any one of claims 1 to 9, characterized in that, It includes the following steps: Fix the top of the upper joint (1) to the upper end of the sucker rod, fix the bottom of the lower joint (9) to the lower end of the sucker rod, and then the sucker rod works in the well. The liquid in the well drives the active block (3) to move, thereby squeezing the load sensors (4) to obtain the lateral force received by the sucker rod. Obtain the axial force magnitude and acceleration through the axial force sensor (7) and the acceleration sensor (8) inside the axial force test sub - section (6), and calculate the speed and movement trajectory of the sucker rod according to the axial force magnitude and acceleration to complete the force test.

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