A drilling fluid sealing performance tester simulating downhole circulating conditions

Abstract

The present application relates to the technical field of drilling fluid sealing performance testing, and particularly relates to a drilling fluid sealing performance tester simulating downhole circulation conditions. The drilling fluid sealing performance tester comprises a drilling fluid supply bin, a circulating pump, independent test bin bodies and a control system; further comprises a liquid distribution bin and a liquid collection bin, at least two groups of the independent test bin bodies are connected in parallel between the liquid distribution bin and the liquid collection bin, and a closed-loop drilling fluid circulation loop is formed by connecting the circulating pipeline in sequence from the drilling fluid supply bin, the circulating pump, the liquid distribution bin, each group of the independent test bin bodies, the liquid collection bin to the drilling fluid supply bin; each group of the independent test bin bodies is respectively equipped with an ultrasonic detection system for real-time detection of sound wave signals passing through rock samples in the corresponding independent test bin bodies, and the sealing performance of the drilling fluid is judged based on the change of the sound wave signals before and after the drilling fluid seals the rock samples. The present application can simultaneously carry out sealing test comparison experiments on multiple groups of rock samples, effectively improve the test efficiency, and the test results are more accurate.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid plugging performance testing technology, and specifically to a drilling fluid plugging performance tester that simulates downhole circulation conditions. Background Technology

[0002] During coal mining, downhole drilling, and oil and gas well operations, coal and rock formations are prone to fractures and porosity, which can easily lead to drilling fluid loss, wellbore collapse, and other engineering problems, seriously affecting downhole operation safety and construction efficiency. Therefore, accurately evaluating the sealing performance of drilling fluids is extremely important.

[0003] Chinese invention patent CN105445365A discloses a method for evaluating the plugging performance of drilling fluid. This method simulates the plugging effect of drilling fluid on formation rock by immersing core slices in drilling fluid under high temperature and pressure conditions. Then, a CWT-200 sonic velocimeter is used to measure the relative rock strength of the core slices, thus reflecting the plugging performance of the drilling fluid. However, this patent uses a static testing method and cannot simulate the actual dynamic circulation environment of drilling fluid downhole, failing to accurately reflect downhole circulation conditions and resulting in significant deviations between the test data and actual downhole operating conditions.

[0004] Chinese invention patent CN104453867A discloses a drilling fluid dynamic coal seam wellbore plugging tester. This tester simulates a coal seam wellbore by pressing it into the wellbore, then circulating the drilling fluid under simulated high temperature and flow rate conditions within the wellbore. Two windows are opened on the sidewall of this artificial wellbore to measure the volume of the filtrate and observe changes in the wellbore wall. While this patent can simulate the dynamic circulation of downhole drilling fluid and provide a relatively realistic evaluation of its plugging performance on rock samples, it relies on measuring the filtrate volume. This method is susceptible to damage under high temperature and high pressure conditions, especially with poor-quality rock samples, resulting in low discriminative power in the plugging performance evaluation and failing to provide substantial data.

[0005] To address the issue in the aforementioned patent's high-temperature, high-pressure filtration test where poor-quality mud cake is easily destroyed under high temperature and pressure, leading to low discriminative power in the sealing performance evaluation results and a lack of substantial data, Chinese invention patent CN116660459A discloses a drilling fluid sealing performance evaluation device and experimental method. This patent uses a circulating injection system and annular pressure injection system to simulate the ultra-high temperature and high pressure conditions of the wellbore during drilling. Pressure sensors collect pressure data and transmit it to a computer, while temperature sensors collect temperature data and transmit it to a computer. The computer then evaluates the drilling fluid sealing performance based on the pressure and temperature data. This patent can quantitatively evaluate the sealing ability of drilling fluid on the formation under ultra-high temperature and high pressure conditions, providing strong support for oil and gas extraction in ultra-high temperature and high pressure formations. Although this patent claims to solve the problem of poor-quality mud cake being easily destroyed under high temperature and pressure in the high-temperature, high-pressure filtration test, resulting in a lack of substantial data in the sealing performance evaluation, it does not clearly describe how to evaluate the drilling fluid sealing performance based on the measured pressure and temperature data, or how to quantitatively evaluate the sealing ability of drilling fluid on the formation under ultra-high temperature and high pressure conditions. In particular, this patent can only perform a single test on a single set of rock samples, and cannot simultaneously conduct sealing test comparison experiments on multiple sets of rock samples. The testing efficiency is low, parallel experiments require multiple rounds, the operation is cumbersome, and the test results are easily affected by operational errors in the measurement process, resulting in inaccurate test results. Summary of the Invention

[0006] The purpose of this invention is to provide a drilling fluid plugging performance tester that simulates downhole circulation conditions, in order to solve the problems of existing technologies that can only perform single-testing of a single set of rock samples, resulting in low testing efficiency, multiple rounds required for parallel experiments, cumbersome operation, and inaccurate test results.

[0007] To achieve the above objectives, the technical solution of the drilling fluid plugging performance tester simulating downhole circulation conditions provided by this invention is as follows: A drilling fluid plugging performance tester simulating downhole circulation conditions includes a drilling fluid replenishment tank, a circulation pump, an independent test chamber, and a control system; It also includes a distribution tank and a collection tank. At least two sets of independent test tanks are arranged in parallel between the distribution tank and the collection tank. A closed-loop drilling fluid circulation circuit is formed by connecting the circulation pipeline along the drilling fluid supply tank, circulation pump, distribution tank, each set of independent test tanks, collection tank and drilling fluid supply tank. Each independent test chamber is equipped with an ultrasonic testing system, which includes an ultrasonic transmitter and an ultrasonic receiver positioned opposite each other on both sides of the independent test chamber. The ultrasonic transmitter and receiver are used to detect the acoustic signal passing through the rock sample in the corresponding independent test chamber in real time, and to judge the sealing performance of the drilling fluid based on the change in acoustic signal before and after the drilling fluid seals the rock sample.

[0008] The beneficial effects of the above technical solution: This invention is an improved invention. This invention utilizes a parallel arrangement of a distribution chamber and a collection chamber to set up at least two sets of independent test chambers, which are sequentially connected to the drilling fluid replenishment chamber and the circulation pump via circulation pipelines to construct multiple closed-loop drilling fluid circulation circuits. This not only highly replicates the downhole drilling fluid circulation flow conditions, closely matches the on-site operating environment, and makes laboratory test data more consistent with actual engineering conditions, but also allows for simultaneous comparative experiments on drilling fluid plugging tests of multiple rock samples each time, effectively improving testing efficiency. Furthermore, in conventional multi-channel parallel pipelines, circulation pumping is prone to pressure pulsations. These pulsations directly interfere with the pressure stability of each branch, disrupting the uniformity of comparative experimental conditions. This invention sets up a distribution chamber between the circulation pump and each set of independent test chambers. Utilizing the large cavity effect of the distribution chamber, pump pulsations can be eliminated, providing a stable constant pressure source for each parallel circuit. Meanwhile, compared to existing acoustic testing which involves offline static measurement of soaked core slices, this invention uses ultrasonic transmitters and receivers positioned opposite each other on both sides of an independent testing chamber to detect acoustic signals passing through the rock sample in real time during a dynamic cycle. Changes in the acoustic signals can accurately reflect the sealing density of coal and rock pores and fractures. Furthermore, the acquisition of acoustic signals does not rely on the physical filtration process of fluids and will not cause physical damage to the microstructure of weakly cemented or low-quality rock samples. Compared to testing other physical properties, the acoustic signal test data of this invention will not be affected by abnormal interference caused by rock sample damage due to poor quality. Therefore, it overcomes the problem of test failure caused by the easy destruction of rock samples due to poor quality, and realizes non-destructive in-situ testing without stopping the machine or disassembling the sample. It avoids operational errors introduced by multiple rounds of disassembly and assembly, and improves testing efficiency and data accuracy.

[0009] As a further improvement, the circulating pump is a replenishment pump equipped with a frequency converter, which is controlled by a control system.

[0010] The beneficial effects of the above technical solution are: the variable frequency controller can adjust the delivery power of the replenishment pump according to the test requirements, so that the internal pressure of each chamber can be uniformly maintained within the target downhole simulated pressure range, adapting to different downhole simulated pressures, so as to carry out drilling fluid plugging experiments under different working conditions.

[0011] As a further improvement, a pressure detection and regulation system is installed on the circulation pipeline of each independent test chamber to monitor the drilling fluid delivery pressure of each independent test chamber in real time and feed it back to the control system, which then controls the individual adjustment of the drilling fluid delivery pressure of each independent test chamber.

[0012] The beneficial effects of the above technical solution are as follows: Unlike conventional parallel pipelines, which cannot achieve pressure regulation and flow control of a single channel in the same circulation system and make it difficult to conduct comparative experiments on different chemical conditions, this invention can monitor the drilling fluid delivery pressure of each independent test chamber in real time through various pressure detection and regulation systems and adjust it individually by the control system. This allows for setting different experimental conditions and conducting comparative experiments on multiple rock samples under different experimental conditions simultaneously.

[0013] As a further improvement, the liquid separation chamber is connected to the inlet of each group of independent test chambers through several liquid inlet pipes, and each of the liquid inlet pipes is equipped with a pressure detection and regulation system.

[0014] The beneficial effects of the above technical solution are as follows: The design of the liquid distribution chamber can play a role in diverting the flow, and at the same time, the large cavity effect can eliminate pump body pulses and provide a stable constant pressure source for each circuit.

[0015] As a further improvement, the pressure detection and regulation system includes a control valve, a pressure gauge, and a control switch for controlling the opening and closing of the control valve. The control valve is installed on the corresponding inlet pipe or at the junction of the liquid distribution chamber and the corresponding inlet pipe. The pressure gauge is installed on the valve body of the control valve or the corresponding inlet pipe. The opening degree of the control valve is controlled by the control system and is used to individually adjust the drilling fluid injection pressure of the corresponding inlet pipe. The detection signal of the pressure gauge is fed back to the control system to control the frequency converter to adjust the operating frequency of the replenishment pump, thereby adjusting the operating pressure of the replenishment pump.

[0016] The beneficial effects of the above technical solution are as follows: Through the control switch and control system, the control valve can be opened, closed, or its opening degree adjusted independently, accurately controlling the drilling fluid flow and on / off of the corresponding circulation pipeline; the pressure gauge can monitor the drilling fluid delivery pressure of the corresponding loop in real time, allowing staff to intuitively observe the pressure value and quickly adjust to the target downhole simulated pressure value, maximizing the reproduction of the real downhole working conditions and ensuring that the test results closely match the actual situation on site; at the same time, during the test, the pressure gauge feeds the real-time pressure back to the control system, and the output frequency of the dynamic frequency converter is adjusted through the PID algorithm, thereby adjusting the pump frequency of the replenishment pump, so that the internal pressure of each group of independent test chambers is uniformly maintained within the downhole simulated pressure range, truly reproducing the downhole circulation conditions.

[0017] As a further improvement, a pump is installed on the pipeline between the collection tank and the drilling fluid replenishment tank. The pump is equipped with a frequency converter controlled by the control system. The collection tank is connected to the outlet of each group of independent test tanks through several one-way outlet pipes. A one-way valve is installed in each one-way outlet pipe to control the one-way flow of drilling fluid from the independent test tank to the collection tank.

[0018] The beneficial effects of the above technical solution are as follows: By cooperating with the pumping pump, the pressure balance of the entire circulation system can be maintained, achieving stable circulation of drilling fluid; the above-mentioned collection tank can play a collecting role, collecting the drilling fluid discharged from each independent test chamber through a one-way outlet pipe, and then returning it in a unified manner to achieve drilling fluid return circulation; in conventional multi-channel fluid collection and return, if the outlet pressure of each test chamber is inconsistent, the fluid in the high-pressure channel is very likely to backflow into the low-pressure channel, causing crosstalk between circuits. This invention, through a one-way valve, allows the drilling fluid to flow unidirectionally from the independent test chamber to the collection tank along the one-way outlet pipe, avoiding drilling fluid backflow and ensuring that the one-way outlet pipes do not crossflow with each other.

[0019] As a further improvement, the collection chamber is equipped with a filter screen arranged between its outlet and inlet to filter out coal and rock particles carried in the drilling fluid entering the collection chamber.

[0020] The beneficial effects of the above technical solution are as follows: Since the synchronous flushing of multiple rock samples will generate more coal and rock particles, if they are directly returned to the drilling fluid replenishment tank and enter the circulation system, they will seriously damage the circulation pump. Therefore, the present invention filters the returned drilling fluid through the above-mentioned filter screen to avoid damage to the circulation pump caused by coal and rock particles carried in the drilling fluid.

[0021] As a further improvement, the independent test chamber includes a test chamber with an open top. The top of the test chamber is threadedly connected to a chamber cover. The center of the chamber cover has a liquid inlet hole and is threadedly connected to the outlet end of the corresponding liquid inlet pipe. The inner cavity of the test chamber forms a placement cavity for the rock sample. A drilling fluid guide channel is opened inside the bottom of the test chamber. The inner end of the drilling fluid guide channel is located on the inner bottom surface of the test chamber and communicates with the placement cavity. The outer end of the drilling fluid guide channel is located on the bottom side wall of the test chamber and is threadedly connected to the inlet end of the corresponding one-way liquid outlet pipe.

[0022] The beneficial effects of the above technical solution are as follows: The independent test chamber is composed of a test chamber and a cover. The cover is threadedly fitted to the test chamber, which is tightly sealed and has strong pressure resistance. The center of the cover is threadedly connected to the outlet end of the corresponding inlet pipe, and the bottom of the test chamber is threadedly connected to the inlet end of the corresponding one-way outlet pipe. The connection is tight, leak-proof, and has high assembly and disassembly efficiency.

[0023] As a further improvement, the inlet pipe is a high-pressure flexible hose.

[0024] The beneficial effects of the above technical solution are as follows: the inlet pipe can be freely bent and the angle adjusted to adapt to independent test chambers in different positions.

[0025] As a further improvement, the top of the drilling fluid replenishment tank is provided with a filling port, which is threadedly connected to a sealing cap.

[0026] The beneficial effects of the above technical solution are as follows: drilling fluid can be replenished at any time, maintaining a stable liquid level inside the drilling fluid replenishment tank and ensuring balanced circulating pressure. Attached Figure Description

[0027] Figure 1 A schematic diagram of the overall structure of a drilling fluid plugging performance tester simulating downhole circulation conditions provided by the present invention. Figure 1 A cutaway diagram of one of the independent test chambers; Figure 2 A schematic diagram of the overall structure of a drilling fluid plugging performance tester simulating downhole circulation conditions provided by the present invention. Figure 2 The diagram shows a cross-section of the drilling fluid replenishment tank, the distribution tank, and an independent testing tank. Figure 3 This is a partial enlarged schematic diagram of a drilling fluid plugging performance tester simulating downhole circulation conditions provided by the present invention, wherein the drilling fluid supply tank, the distribution tank, and an independent test tank are shown in cross-section. Figure 4 This is a schematic diagram of the control valve of a drilling fluid plugging performance tester that simulates downhole circulation conditions, as proposed in this invention, in which the drilling fluid supply chamber and the distribution chamber are shown in cross-section. Figure 5 This is a schematic diagram of the independent test chamber of a drilling fluid plugging performance tester that simulates downhole circulation conditions, as proposed in this invention. The independent test chamber is shown in cross-section.

[0028] In the diagram: 1. Test base; 2. Locking block; 3. Independent test chamber; 31. Detection chamber; 32. Chamber cover; 33. Inlet threaded connector; 34. Outlet threaded connector; 35. Placement chamber; 36. Drilling fluid guide channel; 4. Fixed bracket; 5. Drilling fluid circulation mechanism; 51. Drilling fluid replenishment chamber; 52. Replenishment pump; 53. Separation chamber; 54. Control valve; 55. Inlet pipe; 56. Inlet threaded connector; 57. Drainage device; 571. Drainage pump; 572. Curved pipe; 573. Collection chamber; 574. One-way outlet pipe; 575. Outlet threaded connector; 58. Filling port; 59. Connecting rod; 510. Control switch; 511. Pressure gauge; 6. Signal transmitting base; 7. Ultrasonic transmitter; 8. Signal receiving base; 9. Ultrasonic receiver. Detailed Implementation

[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0030] The main concept of this invention is to address the limitations of existing drilling fluid plugging testing devices, which can only perform a single test on a single set of rock samples each time, resulting in low testing efficiency, the need for multiple rounds of parallel experiments, cumbersome operation, and inaccurate test results due to operational errors during the measurement process. This invention proposes to construct multiple drilling fluid plugging test loops using multiple sets of test containers, thereby enabling simultaneous comparative plugging tests on multiple sets of rock samples, effectively improving testing efficiency. At the same time, it utilizes acoustic detection to achieve non-destructive testing and improve testing accuracy.

[0031] Based on this, the present invention improves upon the existing technology and provides a drilling fluid plugging performance tester that simulates downhole circulation conditions to solve the problems existing in the prior art.

[0032] A basic embodiment of the drilling fluid plugging performance tester simulating downhole circulation conditions provided by this invention is as follows: like Figure 1 and Figure 2 As shown, a drilling fluid plugging performance tester simulating downhole circulation conditions includes: Test base 1, with a fixed connection of a locking block 2 on the test base 1, and an independent test chamber 3 locked onto the locking block 2. Both the locking block 2 and the independent test chamber 3 are set to four groups, with one-to-one correspondence, so that four groups of rock samples can be tested independently at the same time. The number of groups can also be adjusted according to the testing needs. In this way, multiple groups of rock samples can be used for sealing test comparison experiments at the same time, which effectively improves the testing efficiency. The fixed support 4 is fixedly connected to the test base 1 at its bottom. The fixed support 4 is equipped with a drilling fluid circulation mechanism 5. The drilling fluid circulation mechanism 5 is stably installed on the fixed support 4 and is connected to each group of independent test chambers 3 through circulation pipelines to form a closed loop, thereby realizing the closed-loop delivery of drilling fluid and accurately replicating the pressure, flow rate and seepage state of the drilling fluid circulation flow downhole. Each independent test chamber 3 is equipped with a pressure detection and adjustment system on its circulation pipeline. The pressure detection and adjustment system monitors the drilling fluid delivery pressure of each independent test chamber 3 in real time, enabling the staff to adjust the drilling fluid circulation mechanism 5 according to the pressure and quickly adjust the drilling fluid delivery pressure of each independent test chamber 3 to the target downhole simulated pressure value, so as to maximize the restoration of the real downhole working conditions and ensure that the test results are consistent with the actual situation on site. The bottom of the signal transmitting base 6 is fixedly connected to the test base 1. An ultrasonic transmitter 7 is fixedly connected to the signal transmitting base 6. The ultrasonic transmitter 7 is set to four groups, which are paired with four independent test chambers 3. Each ultrasonic transmitter 7 is facing the side wall of an independent test chamber 3 to ensure that the sound wave signal can stably penetrate the chamber and the sample. A signal receiving base 8 is fixedly connected to the test base 1 at its bottom. An ultrasonic receiver 9 is fixedly connected to the signal receiving base 8 and is symmetrically distributed on the other side of the independent test chamber 3 with the signal transmitting base 6. The ultrasonic receiver 9 is also set in four groups, corresponding one-to-one with the ultrasonic transmitter 7. Each group of ultrasonic transmitter 7 and ultrasonic receiver 9 is set coaxially and facing each other, respectively corresponding to the detection of a rock sample inside an independent test chamber 3. The sound wave signal after penetrating the sample is received in real time. By measuring the changes in sound wave signal parameters such as sound wave attenuation amplitude and propagation speed, the degree of sealing of coal and rock pores and fissures is accurately determined, realizing non-destructive testing. Compared with testing other physical property parameters, the acquisition of sound wave signals in this invention does not rely on the physical filtration process of fluids during the testing process, nor does it cause physical damage to the microstructure of weakly cemented or low-quality rock samples. Therefore, the test data will not be affected by abnormal interference caused by the damage of rock samples due to poor quality, thus ensuring the accuracy of the test results.

[0033] The ultrasonic transmitter 7 and ultrasonic receiver 9 constitute the ultrasonic detection system. Since each independent test chamber 3 of this invention is independently equipped with an ultrasonic detection system, throughout the entire sealing test cycle, without disassembling the rock sample, the ultrasonic transmitter 7 and ultrasonic receiver 9, which are set in situ, can directly monitor in real time the changes in acoustic signals before and after sealing the rock sample within the corresponding independent test chamber 3. Online monitoring under situ sealed conditions completely avoids human error caused by repeated disassembly and installation of rock samples and multiple measurements, thereby significantly improving the accuracy and reliability of experimental data.

[0034] This testing instrument also includes a control system, which is connected to the drilling fluid circulation mechanism 5, the pressure detection and regulation system, and the ultrasonic detection system.

[0035] In a specific embodiment, such as Figure 2 and Figure 3 As shown, the drilling fluid circulation mechanism 5 includes a drilling fluid replenishment tank 51 and a replenishment pump 52. The surface of the drilling fluid replenishment tank 51 is fixedly connected to the fixed support 4. The replenishment pump 52 is located at the bottom of the drilling fluid replenishment tank 51, and the input end of the replenishment pump 52 is connected to the bottom outlet of the drilling fluid replenishment tank 51.

[0036] The replenishment pump 52 is equipped with a frequency converter to form a high-pressure frequency converter pump body, which has a pressure adjustment range of 0 to 5 MPa. The frequency converter is controlled by the control system according to the pressure detection signal of the pressure detection and adjustment system. It can adjust the delivery power according to the test requirements and adapt to different downhole simulated pressures so as to carry out plugging experiments under different working conditions.

[0037] The output end of the replenishment pump 52 is fixedly connected to a distribution chamber 53, which plays the role of diverting and stabilizing pressure. Specifically, the large cavity effect of the distribution chamber 53 can eliminate pump body pulses, provide a stable constant pressure source for the four circuits, and evenly distribute the drilling fluid delivered by the pump to each circulation pipeline.

[0038] The bottom of the liquid separation chamber 53 is fixedly connected to a control valve 54. There are four control valves 54, corresponding to the number of four independent test chambers 3. Each control valve 54 is independent of each other and can be opened, closed or adjusted individually to precisely control the drilling fluid flow and on / off of the corresponding circulation pipeline. In this way, different experimental conditions can be set, and comparative experiments of multiple rock samples under different experimental conditions can be carried out simultaneously.

[0039] The bottom end of the control valve 54 is fixedly connected to an inlet pipe 55. There are four inlet pipes 55. The inlet pipes 55 are high-pressure flexible hoses. The inlet pipes 55 can be made of polytetrafluoroethylene, nitrile rubber, or fluororubber. The body is wear-resistant and corrosion-resistant. It can be freely bent to adjust the angle and adapt to the independent test chambers 3 in different positions.

[0040] In other embodiments, the control valve 54 may be mounted on the inlet pipe 55, the top end of which is mounted on the bottom end of the dispensing chamber 53 via a threaded connector.

[0041] Each inlet pipe 55 is rotatably connected to an inlet threaded connector 56 at its bottom end, enabling independent inlet control for each compartment. The inlet threaded connector 56 adopts a rotary quick-connect structure, which can be flexibly rotated and connected, and is easy to disassemble and assemble.

[0042] The top of the drilling fluid replenishment tank 51 is equipped with a filling port 58 for adding drilling fluid. The filling port 58 is equipped with a threaded sealing cap. After adding drilling fluid, the cap can be tightened to prevent liquid from overflowing or impurities from entering the tank during the test. This facilitates the replenishment of drilling fluid at any time, maintains a stable liquid level inside the drilling fluid replenishment tank 51, and ensures balanced circulation pressure.

[0043] A connecting rod 59 is fixedly connected between the bottom of the drilling fluid replenishment tank 51 and the distribution tank 53. Multiple connecting rods 59 are symmetrically arranged to further improve the installation stability of the distribution tank 53, prevent the distribution tank 53 from shaking, shifting or even breaking during the high-pressure drilling fluid transportation process, and ensure the long-term stable operation of the equipment.

[0044] More specifically, such as Figure 3 As shown, a control switch 510 is fixedly connected to the liquid separation chamber 53. The number of control switches 510 is set to four, which control the opening and closing of the corresponding control valves 54 respectively.

[0045] A pressure gauge 511 is installed on the valve body of control valve 54. The pressure gauge 511 uses a high-precision digital display or pointer dial to monitor the drilling fluid delivery pressure of the corresponding circuit in real time. The operator can intuitively observe the pressure value and quickly adjust it to the target downhole simulated pressure value to maximize the reproduction of the real downhole working conditions and ensure that the test results are close to the actual field conditions. At the same time, during the test, the pressure gauge 511 feeds the real-time pressure back to the control system, and adjusts the pumping frequency of the replenishment pump 52 through a PID algorithm to keep the internal pressure of each group of independent test chambers 3 uniformly maintained within the downhole simulated pressure range, thus truly reproducing the downhole circulation conditions. In other embodiments, the pressure gauge 511 is directly installed on the inlet pipe 55.

[0046] The corresponding control valve 54, control switch 510 and pressure gauge 511 constitute a pressure detection and regulation system.

[0047] like Figure 3 and Figure 4 As shown, the drilling fluid circulation mechanism 5 also includes a drainage device 57, which consists of a drainage pump 571. The drainage pump 571 uses a pressure-resistant pump body of the same specification as the replenishment pump 52 and operates in conjunction with the replenishment pump 52. It is also equipped with a frequency converter. During the actual test, as the micro-fractures of the rock sample in the independent test chamber 3 are gradually blocked by the drilling fluid, the flow resistance of the entire circulation loop shows a dynamic increasing trend. Under the regulation of its frequency converter, the replenishment pump 52 actively reduces its operating frequency to reduce the output flow, thereby maintaining the set pressure. The whole device constitutes the circulation pump of the entire circulation system to maintain the pressure balance of the entire circulation system. The pump 571 is fixedly connected to the drilling fluid supply tank 51. The input end of the pump 571 is fixedly connected to the curved pipe 572. The bottom end of the curved pipe 572 is fixedly connected to the collection tank 573. The collection tank 573 plays a role in collecting and collecting the drilling fluid discharged from each independent test tank 3, and then returning it in a unified manner.

[0048] One-way outlet pipes 574 are fixedly connected to the collection tank 573. There are four one-way outlet pipes 574, corresponding to the number of independent test chambers 3, which collect drilling fluid in four separate ways without cross-flow. Each set of one-way outlet pipes 574 is equipped with a one-way valve to control the unidirectional flow of drilling fluid from the independent test chamber 3 to the collection tank 573 along the one-way outlet pipe 574, thus avoiding backflow of drilling fluid. Each set of one-way outlet pipes 574 is rotatably connected to the inlet end with an outlet screw. The threaded connector 575 is threaded to the outlet of the corresponding group of independent test chambers 3, realizing the independent discharge and return of drilling fluid inside each group of independent test chambers 3. Together with the corresponding inlet pipeline, it forms a complete closed-loop circulation system to avoid drilling fluid leakage and waste. The output end of the discharge pump 571 is connected to the inlet of the drilling fluid replenishment chamber 51 to realize the return circulation of drilling fluid. The bottom end of the collection chamber 573 is fixedly connected to the test base 1 to ensure structural stability.

[0049] In one embodiment, a filter screen may be installed inside the collection tank 573. The filter screen is arranged between the outlet and the inlet of the collection tank 573 to filter out coal and rock particles carried in the drilling fluid entering the collection tank 573, thereby preventing damage to the circulating pump caused by coal and rock particles carried in the drilling fluid.

[0050] In one embodiment, Figure 4 and Figure 5As shown, the independent test chamber 3 includes a test chamber 31. The bottom of the test chamber 31 is snapped into the locking block 2, making it easy to assemble and disassemble. The snap-fit ​​structure adopts a quick-release design, which is convenient to assemble and disassemble without the need for tools, facilitating quick replacement of rock samples and cleaning of residual impurities and sealing waste inside the chamber. The top of the test chamber 31 is threadedly connected to a chamber cover 32, which is tightly sealed and has strong pressure resistance. The center of the chamber cover 32 has a liquid inlet hole and is fixedly connected to a liquid inlet threaded connection seat 33. The inner cavity of the test chamber 31 forms a placement cavity 35 for... A standard hollow rock sample for simulating a wellbore is placed. The standard hollow rock sample is made by uniformly mixing coal powder and sandstone particles of a specific mesh size with epoxy resin or cement in a set ratio, adding an appropriate amount of gypsum and water, and loading the mixture into a cylindrical mold with a central positioning steel mandrel. The outer diameter of the mandrel is the inner diameter of the standard hollow rock sample. A hydraulic press is used to apply a preset pressure to the mold to make it dense and molded. After curing, the central steel mandrel is removed to obtain a hollow cylindrical rock sample with a high degree of geometric standardization. By adding soluble salts to the ingredients or by embedding metal sheets, and then dissolving in water or extracting the solidified material, a uniform and controllable network of pores and fractures can be formed inside the hollow rock sample. The bottom of the testing chamber 31 is provided with a drilling fluid guide channel 36. The inner end of the drilling fluid guide channel 36 is connected to the placement cavity 35. The outer end of the drilling fluid guide channel 36 is set on the bottom side wall of the testing chamber 31 and is equipped with a liquid outlet threaded connector 34 to guide the drilling fluid through the rock sample at a uniform speed, simulating the downhole seepage process. The liquid inlet threaded connector 33 is threadedly connected to the liquid inlet threaded connector 56, and the liquid outlet threaded connector 34 is threadedly connected to the liquid outlet threaded connector 575. The connection is tight, leak-proof, and has high disassembly and assembly efficiency.

[0051] The working principle of this invention is as follows: During use, the standard hollow rock sample to be tested is placed into the placement cavity 35 of each group of independent test chambers 3, and the chamber cover 32 is tightened to complete the seal. The bottom of the test chamber 31 is then inserted into the locking block 2 on the test base 1 to fix the chamber. Subsequently, the inlet threaded connector 56 is tightened to the inlet threaded connector 33, and the outlet threaded connector 575 is tightened to the outlet threaded connector 34 to complete the connection of the circulation pipeline. Sufficient drilling fluid is added to the drilling fluid replenishment chamber 51 through the filling port 58. The replenishment pump 52 and the discharge pump 571 are then turned on. After startup, the output frequency of the replenishment pump 52 is slowly increased by the frequency converter. The system pressure is generated by utilizing the throttling and pressure regulating effect of each group of control valves 54, combined with the flow resistance of the rock sample itself within the independent test chamber 3 and the resistance of the circulation pipeline. Pressure gauge 511 feeds back the real-time detected test pressure signal to the control system. Based on the preset target pressure value, the control system uses a PID algorithm to dynamically adjust the output frequency of the frequency converter, thereby controlling the output pressure of the replenishment pump 52. This ensures that the pressure inside each independent test chamber 3 is stably maintained within the set downhole simulated pressure range, and that the pressure inside the four test chambers 31 is uniformly maintained at the benchmark pressure of 3.5 MPa for exceeding the standard sample test, simulating downhole pressure and restoring downhole circulation conditions.If different pressure tests are required for a single group, independent pressure drop control can be achieved by fine-tuning the opening of the control valve 54 of the corresponding loop; the drilling fluid is delivered to the distribution chamber 53 by the replenishment pump 52, enters the corresponding test chamber 31 through each inlet pipe 55, passes through the rock sample, and flows into the collection chamber 573 through the drilling fluid guide channel 36 and the one-way outlet pipe 574, and then flows back to the drilling fluid replenishment chamber 51 by the discharge pump 571, forming a closed loop circulation. During the circulation, the internal gaps of the hollow coal rock sample are filled by the drilling fluid; the ultrasonic pump is activated. The ultrasonic transmitter 7 and ultrasonic receiver 9 collect acoustic signals passing through the rock sample in real time. The sealing effect of the drilling fluid is judged by the changes in acoustic attenuation and propagation speed before and after the drilling fluid seals the rock sample. The higher the residual content of the drilling fluid after filling the gaps in the coal and rock sample, the better the sealing performance; the lower the residual content, the worse the sealing performance. Specifically, the equivalent propagation speed of the acoustic wave on the radial path of the hollow rock sample cylinder wall is determined by the total radial geometric thickness of the rock sample and the actual propagation time of the acoustic wave. This invention defines the rate of change of acoustic wave propagation speed as... The evaluation index is equal to the percentage obtained by dividing the difference between the real-time equivalent sound velocity after sealing and the initial equivalent sound velocity before sealing by the initial equivalent sound velocity. Since the propagation distance of sound waves in rock samples is constant, in specific data processing, this rate of change is equivalent to the percentage obtained by dividing the difference between the initial propagation time before sealing and the real-time propagation time after sealing by the real-time propagation time. The larger the value of this propagation velocity change rate, the more fully the internal gaps of the rock sample are filled by the solid phase, and the higher the content of residual sealing material. This invention defines the sound amplitude change rate as an evaluation index, which is equal to the percentage obtained by dividing the difference between the maximum amplitude of the first wave of the ultrasonic signal received in real time after sealing and the maximum amplitude of the initial first wave before sealing by the initial maximum amplitude of the first wave. The larger the value of this rate of change, the smaller the sound energy dissipation caused by acoustic impedance mismatch, and the better the structural bonding degree and compactness of the sealing layer. After the test is completed, the equipment is turned off, the threaded joint is disassembled, the independent test chamber 3 is removed, and the sample is replaced to carry out the next round of testing. The operation is convenient and can realize continuous and efficient testing of multiple sets of samples.

[0052] This invention not only allows for testing the plugging performance of the same drilling fluid on rock samples from different geological formations under the same circulation conditions, to study which geological conditions the drilling fluid is suitable for drilling operations, but also enables the study of the plugging effect of the same drilling fluid on the same rock sample under different circulation conditions (drilling pressure), in order to determine the appropriate drilling pressure.

[0053] If multiple single testing devices are used, it is difficult to ensure the synchronization of pressure and liquid level in each device because each device has an independent replenishment tank and pump. This invention provides the circulating medium through a single drilling fluid replenishment tank and maintains a stable liquid level within the replenishment tank, thus ensuring balanced circulating pressure from the source.

[0054] Furthermore, individual manufacturing differences exist in the pumps, valves, and sensors of multiple individual testing devices, which can introduce uncontrollable equipment system errors into comparative experiments. This application addresses this by using a unified liquid distribution system within a closed-loop system, combined with a centralized control system, to minimize the interference of individual equipment differences on experimental accuracy.

[0055] Parallel operation of multiple single testing devices results in a large number of devices, high costs, large footprint, and cumbersome operation, lacking the engineering practicality of a parallel integrated system.

[0056] It should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0057] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A drilling fluid plugging performance tester simulating downhole circulation conditions, comprising a drilling fluid replenishment tank, a circulation pump, an independent test chamber, and a control system, characterized in that: It also includes a distribution tank and a collection tank. At least two sets of independent test tanks are arranged in parallel between the distribution tank and the collection tank. A closed-loop drilling fluid circulation circuit is formed by connecting the circulation pipeline along the drilling fluid supply tank, circulation pump, distribution tank, each set of independent test tanks, collection tank and drilling fluid supply tank. Each independent test chamber is equipped with an ultrasonic testing system, which includes an ultrasonic transmitter and an ultrasonic receiver positioned opposite each other on both sides of the independent test chamber. The ultrasonic transmitter and receiver are used to detect the acoustic signal passing through the rock sample in the corresponding independent test chamber in real time, and to judge the sealing performance of the drilling fluid based on the change in acoustic signal before and after the drilling fluid seals the rock sample.

2. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 1, characterized in that: The circulating pump is a replenishment pump equipped with a frequency converter, which is controlled by a control system.

3. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 1 or 2, characterized in that: Each independent test chamber is equipped with a pressure detection and regulation system on its circulation pipeline. This system monitors the drilling fluid delivery pressure of each independent test chamber in real time and feeds it back to the control system, which then adjusts the drilling fluid delivery pressure of each independent test chamber individually.

4. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 3, characterized in that: The liquid separation chamber is connected to the inlet of each group of independent test chambers through several liquid inlet pipes, and each liquid inlet pipe is equipped with a pressure detection and regulation system.

5. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 4, characterized in that: The pressure detection and regulation system includes a control valve, a pressure gauge, and a control switch for controlling the opening and closing of the control valve. The control valve is installed on the corresponding inlet pipe or at the junction of the liquid distribution chamber and the corresponding inlet pipe. The pressure gauge is installed on the valve body of the control valve or the corresponding inlet pipe. The opening degree of the control valve is controlled by the control system and is used to individually adjust the drilling fluid injection pressure of the corresponding inlet pipe. The detection signal of the pressure gauge is fed back to the control system to control the frequency converter to adjust the working frequency of the replenishment pump, thereby adjusting the working pressure of the replenishment pump.

6. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 5, characterized in that: A pump is installed on the pipeline between the collection tank and the drilling fluid replenishment tank. The pump is equipped with a frequency converter controlled by the control system. The collection tank is connected to the outlet of each group of independent test tanks through several one-way outlet pipes. A one-way valve is installed in each one-way outlet pipe to control the one-way flow of drilling fluid from the independent test tank to the collection tank.

7. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 6, characterized in that: The collection chamber is equipped with a filter screen arranged between its outlet and inlet to filter out coal and rock particles carried in the drilling fluid entering the collection chamber.

8. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 7, characterized in that: The independent test chamber includes a test chamber with an open top. The top of the test chamber is threadedly connected to a chamber cover. The center of the chamber cover has a liquid inlet hole and is threadedly connected to the outlet end of the corresponding liquid inlet pipe. The inner cavity of the test chamber forms a rock sample placement cavity. A drilling fluid guide channel is opened inside the bottom of the test chamber. The inner end of the drilling fluid guide channel is located on the inner bottom surface of the test chamber and communicates with the placement cavity. The outer end of the drilling fluid guide channel is located on the bottom side wall of the test chamber and is threadedly connected to the inlet end of the corresponding one-way liquid outlet pipe.

9. The drilling fluid plugging performance tester simulating downhole circulation conditions according to claim 7, characterized in that: The inlet pipe is a high-pressure flexible hose.

10. The drilling fluid plugging performance tester for simulating downhole circulation conditions according to claim 8 or 9, characterized in that: The drilling fluid replenishment tank is equipped with a filling port at the top, and the filling port is threadedly connected to a sealing cap.

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