Method and device for evaluating low-temperature thickening performance of well drilling working fluid

Abstract

The invention relates to a method and a device for evaluating the low-temperature thickening performance of a drilling fluid, and belongs to the field of thickening of drilling fluid plugging materials. The evaluation method comprises the following steps that a refrigerant is refrigerated through liquid nitrogen, then a refrigerant circulation loop formed by the refrigerated refrigerant is used for refrigerating the drilling working fluid to the thickening temperature, the thickening temperature is lower than 0 DEG C, and low-temperature thickening performance evaluation is conducted at the thickening temperature. The refrigerant is refrigerated by using the extremely low temperature of the liquid nitrogen, so that the temperature of the refrigerant is lower than 0 DEG C, and the refrigerant is used as a medium to exchange heat with the drilling working fluid, so that the temperature of the drilling working fluid is adjusted to a low-temperature thickening temperature lower than 0 DEG C, and the low-temperature thickening performance of the drilling working fluid is measured. According to the method, the thickening performance of the drilling working fluid is measured at low temperature, and the method is relatively simple, relatively low in cost and convenient to implement and operate.

Description

Technical Field

[0001] The present invention relates to a method and device for evaluating the low-temperature thickening performance of a drilling working fluid, and belongs to the field of thickening of drilling fluid plugging materials. Background Art

[0002] Well leakage is one of the most troublesome drilling problems during the drilling process. Since the loss of expensive drilling fluid into the formation will lead to an increase in economic costs and may also cause some well control problems. The worldwide well leakage incidence rate accounts for about 20% - 25% of the total number of wells. Therefore, well leakage has always been a problem that has attracted much attention at home and abroad. In high-altitude areas, there is also a need for thickening and plugging of the plugging slurry after the loss of drilling fluid and cementing with cement slurry. However, the climate in this area is cold and the formation temperature is low. Therefore, it is necessary to use a thickening instrument to conduct thickening evaluation experiments on the drilling fluid loss plugging slurry under low-temperature conditions.

[0003] A thickening instrument is an instrument used for testing curable plugging slurries in oil and gas wells. This instrument can measure the consistency value of the curable plugging slurry and measure its thickening time. The thickening time is an important parameter for evaluating the performance of curable plugging materials. Therefore, how to correctly evaluate the thickening performance of curable plugging materials in indoor research and determine the measurement method of curable plugging materials has important significance for solving well leakage problems and reservoir protection.

[0004] Most of the existing thickening instruments are applicable to normal temperature to high temperature. For example, the Chinese invention patent application with the application number CN113237791A discloses a thickening performance evaluation instrument for drilling plugging materials that can be automatically cleaned, which can realize electric heating and air pressurization to simulate the underground environment. The kettle body can be completely sealed, making the obtained thickening time closer to the actual thickening time, facilitating relevant personnel to understand the actual performance parameters of the thickening object. However, the formation temperature in high-altitude low-temperature areas is generally 0°C to -50°C. This thickening instrument can only be applicable to the environment of normal temperature to high temperature and cannot conduct thickening experiments on the drilling fluid loss plugging slurry at low temperature. In addition, the existing equipment that can refrigerate to -50°C is difficult to cooperate with this thickening instrument, and the -50°C refrigeration equipment has a high cost, a large volume, and is not convenient to carry. Summary of the Invention

[0005] The first object of the present invention is to provide a method for evaluating the low-temperature thickening performance of a drilling working fluid to solve the problem that most of the existing methods for evaluating the thickening performance of drilling working fluids are applicable to normal temperature to high temperature and lack low-temperature performance evaluation.

[0006] The second object of the present invention is to provide a device for evaluating the low-temperature thickening performance of a drilling working fluid to solve the problem that there is a lack of a device for evaluating the thickening performance of drilling working fluids in high-altitude low-temperature areas in the existing technology.

[0007] In order to achieve the above objects, the first technical solution of the present invention is as follows:

[0008] A method for evaluating the low-temperature thickening performance of a drilling fluid, comprising the following steps: cooling a refrigerant by liquid nitrogen, and then using a refrigerant circulation loop formed by the cooled refrigerant to cool the drilling fluid to a thickening temperature, where the thickening temperature is lower than 0 °C, and evaluating the low-temperature thickening performance at the thickening temperature.

[0009] In the present invention, the refrigerant is cooled by using the extremely low temperature of liquid nitrogen to make the temperature of the refrigerant lower than 0 °C. The refrigerant is used as a medium to exchange heat with the drilling fluid, so that the temperature of the drilling fluid is adjusted to a low-temperature thickening temperature lower than 0 °C, and then its thickening performance at low temperature is measured. The method of the present invention realizes the measurement of the thickening performance of the drilling fluid at low temperature, and the method is relatively simple, has low cost, and is convenient for implementation and operation.

[0010] To improve the accuracy of evaluating the low-temperature thickening performance, preferably, the thickening temperature is controlled at a constant temperature in the following manner: according to the actual temperature of the drilling fluid and the thickening temperature, determine the heat value that needs to be taken away, denoted as the first heat value; determine the heat value that the refrigerant can take away from the drilling fluid per unit time, denoted as the second heat value;

[0011] When the first heat value is less than the second heat value, heat the refrigerant; when the first heat value is greater than or equal to the second heat value, do not heat the refrigerant.

[0012] Further preferably, by measuring the temperature of the refrigerant per unit time, determine the heat value that the refrigerant can take away from the drilling fluid per unit time.

[0013] Preferably, when the second heat value is less than 0, replace the liquid nitrogen. When the second heat value is less than 0, it indicates that the liquid nitrogen no longer has a refrigeration effect on the refrigerant, and new liquid nitrogen needs to be replaced.

[0014] To avoid the refrigerant temperature being too low and freezing and not flowing, which affects the refrigeration effect of the refrigerant on the drilling fluid, preferably, after the liquid nitrogen cools the refrigerant to be lower than the refrigerant working temperature threshold, update the refrigerant at the liquid nitrogen cooling position and / or heat the refrigerant circulation loop.

[0015] To facilitate the update of the refrigerant at the liquid nitrogen cooling position, preferably, a refrigerant replenishing device is connected between the upstream and downstream of the liquid nitrogen cooling position, and the update is to establish a refrigerant circulation between the liquid nitrogen cooling position and the refrigerant replenishing device.

[0016] To improve the refrigeration efficiency of the drilling fluid, preferably, the thickening of the drilling fluid is carried out in an oil environment, and the refrigerant circulation circuit is used to refrigerate the oil. First, the refrigerant in the refrigerant circulation circuit is used to refrigerate the oil, and then the refrigerated oil exchanges heat with the drilling fluid to refrigerate the drilling fluid to the thickening temperature.

[0017] Preferably, the drilling fluid is a lost circulation plugging slurry for drilling fluid. First, the drilling fluid is added. After the drilling fluid is refrigerated to the thickening temperature in the refrigerant circulation circuit, plugging materials are added to the drilling fluid for thickening performance evaluation. This can avoid shortening the time for the lost circulation plugging slurry of the drilling fluid to cool down to the set thickening temperature and improve the accuracy of the thickening performance evaluation.

[0018] The second technical solution of the present invention is:

[0019] An apparatus for evaluating the low-temperature thickening performance of a drilling fluid includes a thickening kettle and a refrigerant circulation circuit. The refrigerant circulation circuit includes a thickening refrigeration section for refrigerating the thickening kettle and an external section of the kettle connected to the thickening refrigeration section. The external section of the kettle includes a liquid nitrogen refrigeration section. The evaluation apparatus further includes a liquid nitrogen refrigeration chamber having a refrigeration inner cavity for accommodating liquid nitrogen. The liquid nitrogen refrigeration section is disposed in the refrigeration inner cavity, and a circulation pump is further provided on the refrigerant circulation circuit.

[0020] The apparatus of the present invention realizes the refrigeration of the refrigerant by liquid nitrogen by disposing the liquid nitrogen refrigeration section in the refrigeration inner cavity. The circulation pump on the refrigerant circulation circuit can transport the refrigerated refrigerant to other positions. Since the refrigerant circulation circuit includes a thickening refrigeration section for refrigerating the thickening kettle, the refrigerated refrigerant is transported to the position of the thickening kettle, thereby realizing the refrigeration of the thickening kettle. This apparatus can realize the evaluation of the low-temperature thickening performance of the drilling fluid, and is small and portable, occupying a small space.

[0021] To facilitate the constant temperature control of the thickening temperature, preferably, a first temperature sensor for detecting the temperature of the working liquid is provided on the thickening kettle, a second temperature sensor is provided on the liquid nitrogen refrigeration section, and a heater is connected to the refrigerant circulation circuit; the first temperature sensor, the second temperature sensor, and the heater are connected to the main controller;

[0022] According to the actual temperature of the first temperature sensor and the thickening temperature, the heat value to be taken away is determined and denoted as the first heat value; according to the temperature of the second temperature sensor, the heat value that the refrigerant can take away from the drilling fluid per unit time is determined and denoted as the second heat value; the magnitudes of the first heat value and the second heat value are compared and combined with the on / off of the heater to achieve constant temperature control.

[0023] To facilitate the renewal of the refrigerant in the liquid nitrogen refrigeration section, preferably, the low-temperature thickening performance evaluation device further includes a refrigerant storage bin, which has a refrigerant extraction port and a refrigerant return port. The refrigerant extraction port and the refrigerant return port are respectively connected to the upstream and downstream of the liquid nitrogen refrigeration section. A first valve and a second valve are respectively provided on the connecting pipelines of the refrigerant extraction port, the refrigerant return port and the refrigerant circulation circuit. To facilitate the return of the refrigerant, the refrigerant return port is arranged in the upper middle part of the refrigerant storage bin.

[0024] To facilitate the renewal of the refrigerant and the normal operation of the refrigerant circulation circuit during the constant temperature control process, preferably, the first valve, the second valve are connected to the main controller. When the temperature value of the second temperature sensor is lower than the refrigerant working temperature threshold, the first valve and the second valve are opened, and the refrigerant storage bin is used to renew the refrigerant in the liquid nitrogen refrigeration section.

[0025] Preferably, the connecting pipeline of the refrigerant extraction port and the refrigerant circulation circuit forms a first extraction pipeline, and a second extraction pipeline is also connected between the bottom of the refrigerant storage bin and the refrigerant circulation circuit downstream of the liquid nitrogen refrigeration section.

[0026] To improve the regulation efficiency of the thickening temperature, preferably, the low-temperature thickening performance evaluation device further includes an intermediate container, which has an inner cavity for containing oil liquid. The thickening kettle is arranged in the inner cavity, and the thickening refrigeration section is a spiral pipe section spirally wound around the outer periphery of the thickening kettle. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the overall structure of the device for evaluating the low-temperature thickening performance of the drilling fluid of the present invention;

[0028] Figure 2 It is a schematic diagram of a partial structure of the quick-cooling box of the present invention.

[0029] Wherein, 1. Liquid nitrogen storage tank; 2. First pipeline; 3. First valve; 4. Exhaust port; 5. Quick-cooling box; 6. First temperature sensor; 7. First water pump; 8. First three-way valve; 9. Quick-cooling cavity; 10. Second pipeline; 11. Second three-way valve; 12. Third pipeline; 13. Fourth pipeline; 14. Second temperature sensor; 15. Fifth pipeline; 16. Pre-cooling box; 17. Third three-way valve; 18. Second water pump; 19. Sixth pipeline; 20. Magnetic stirrer; 21. Heater; 22. Thickening kettle; 23. Spiral pipe; 24. Third temperature sensor; 25. Thermal insulation layer; 26. Intermediate container; 27. Torque sensor; 28. Second valve; 29. Nitrogen discharge port; 30. Plug; 31. Threaded rod; 32. Bracket; 33. Motor. Detailed Embodiments

[0030] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0031] 1. The device for evaluating the low-temperature thickening performance of the drilling working fluid of the present invention includes a thickening kettle 22 for containing the drilling working fluid, a refrigerant circulation circuit, and a liquid nitrogen refrigeration chamber. The refrigerant circulation circuit includes a thickening refrigeration section for refrigerating the thickening kettle and an external section of the kettle connected to the refrigeration section. The external section of the kettle includes a liquid nitrogen refrigeration section, and the liquid nitrogen refrigeration section is arranged in the inner cavity for containing liquid nitrogen in the liquid nitrogen refrigeration chamber to realize the refrigeration of the refrigerant by liquid nitrogen, and then the refrigerated refrigerant is used to refrigerate the drilling working fluid in the thickening kettle 22. In order to realize the circulation of the refrigerant, a circulation pump is arranged on the refrigerant circulation circuit.

[0032] Furthermore, in order to realize the constant temperature control of the thickening temperature of the drilling working fluid, a first temperature sensor is arranged on the thickening kettle 22 for detecting the real-time temperature of the drilling working fluid, and a second temperature sensor is arranged on the liquid nitrogen refrigeration section for detecting the real-time temperature of the refrigerant after being refrigerated by liquid nitrogen.

[0033] According to the actual temperature of the first temperature sensor and the thickening temperature, the value of the heat to be taken away is determined and denoted as the first heat value; according to the change of the temperature of the second temperature sensor within a unit time, the value of the heat that the refrigerant can take away from the drilling working fluid within a unit time is determined and denoted as the second heat value; when the first heat value is less than the second heat value, it indicates that the refrigeration effect of the refrigerant on the drilling working fluid is stronger than the heat value that the drilling working fluid needs to take away. Therefore, a heater is connected to the refrigerant circulation circuit for heating the refrigerant to make the temperature of the drilling working fluid reach the thickening temperature; when the first heat value is greater than or equal to the second heat value, it indicates that the refrigeration effect of the refrigerant on the drilling working fluid is sufficient to adjust the drilling working fluid to the thickening temperature. Therefore, heating by the heater is not required.

[0034] Furthermore, the device for evaluating the low-temperature thickening performance also includes a refrigerant storage chamber for storing and supplying the refrigerant; the refrigerant storage chamber has a refrigerant extraction port and a refrigerant return port, and the refrigerant extraction port and the refrigerant return port are respectively connected to the upstream and downstream of the liquid nitrogen refrigeration section for extracting the refrigerant in the refrigerant storage chamber and returning the refrigerant in the refrigerant circulation circuit to the refrigerant storage chamber; in order to control the extraction and return of the refrigerant, a first valve and a second valve are respectively arranged on the connecting pipelines of the refrigerant extraction port, the refrigerant return port and the refrigerant circulation circuit.

[0035] Further, in order to separately control the extraction and reflux of the refrigerant, the first valve, the second valve and the main controller are connected; when the temperature value of the second temperature sensor is lower than the refrigerant working temperature threshold, at this time, the refrigerant in the liquid nitrogen refrigeration section may freeze due to too low temperature, resulting in the inability of the refrigerant in the refrigerant circulation loop to circulate, and thus unable to refrigerate the drilling fluid. Therefore, it is necessary to open the first valve and the second valve to update and replace the refrigerant in the liquid nitrogen refrigeration section with the refrigerant in the refrigerant storage bin to ensure the normal operation of the refrigeration work.

[0036] Further, the connecting pipe between the refrigerant extraction port and the refrigerant circulation loop forms a first extraction pipe, and a second extraction pipe is also connected between the bottom of the refrigerant storage bin and the refrigerant circulation loop downstream of the liquid nitrogen refrigeration section.

[0037] Further, in order to improve the refrigeration efficiency of the drilling fluid, the low-temperature thickening performance evaluation device for drilling fluid is also provided with an intermediate container 26 for containing oil. The thickening kettle 22 is located in the inner cavity of the intermediate container 26, and the refrigeration section for refrigerating the thickening kettle 22 is a spiral pipe section spirally wound around the outer periphery of the thickening kettle, so as to realize the refrigerant refrigerating the oil, and the oil refrigerating the drilling fluid in the thickening kettle 22. The contact area between the oil and the thickening kettle 22 is large, and the refrigeration effect is good.

[0038] The specific implementation manner of the low-temperature thickening performance evaluation device for drilling fluid is as follows:

[0039] As Figure 1 shown, it includes a liquid nitrogen storage tank 1, a quick-cooling tank 5, a pre-cooling tank 16 and an intermediate container 26; a quick-cooling cavity 9 is provided in the quick-cooling tank 5, and there is a sandwich between the quick-cooling tank 5 and the quick-cooling cavity 9. The liquid nitrogen storage tank 1 is connected to the middle and upper part of the sandwich through a first pipeline 2; a first valve 3 is arranged on the first pipeline 2; an exhaust port 4 communicating with the sandwich is arranged at the top of the quick-cooling tank 5; a first temperature sensor 6 is arranged on the quick-cooling cavity 9, and the upper end of the quick-cooling cavity 9 is connected to the first end of a first three-way valve 8 through a first water pump 7; the lower end of the quick-cooling cavity 9 is connected to the first end of a second three-way valve 11 through a second pipeline 10; the second end of the second three-way valve 11 is connected to the pre-cooling tank 16 through a fourth pipeline 13; the second end of the first three-way valve 8 is connected to the pre-cooling tank 16 through a fifth pipeline 15; a second temperature sensor 14 is arranged on the pre-cooling tank 16; the third end of the second three-way valve 11 is connected to the first end of a third three-way valve 17 through a third pipeline 12; the bottom of the pre-cooling tank 16 is connected to the second end of the third three-way valve 17 through a second water pump 18; the third end of the third three-way valve 17 is connected to the inlet of a heater 21 through a sixth pipeline 19.

[0040] A thickening kettle 22 is arranged inside the intermediate container 26, a heat preservation layer 25 is arranged outside the intermediate container 25, a magnetic stirrer 20 is arranged at the bottom of the thickening kettle 22, a torque sensor 27 is arranged at the top of the thickening kettle 22, and a third temperature sensor 24 is arranged inside the thickening kettle 22; a spiral tube 23 is arranged between the inner wall of the intermediate container 26 and the thickening kettle 22, and the spiral tube 23 spirally surrounds the periphery of the thickening kettle 22; the outlet of the heater 21 is connected to one end of the spiral tube 23, and the other end of the spiral tube 23 is connected to the third end of the first three-way valve 8.

[0041] The first valve 3, the first temperature sensor 6, the first water pump 7, the first three-way valve 8, the second three-way valve 11, the second temperature sensor 14, the third three-way valve 17, the second water pump 18, the drive source of the magnetic stirrer 20, the heater 21, the third temperature sensor 24, and the torque sensor 27 are respectively connected to the main controller.

[0042] A partial schematic diagram of the quick-cooling box 5 is as Figure 2 shown. An exhaust port 4 communicating with the interlayer is arranged at its top and a support 32, a threaded rod 31 is arranged through the support 32, and a plug 30 matching with the exhaust port 4 is arranged at the bottom of the threaded rod 31; a motor 33 for driving the threaded rod 31 to move up and down is arranged on the support 32; the motor 33 is connected to the main controller; a nitrogen discharge port 29 communicating with the interlayer is arranged at the bottom of the quick-cooling box 5, a second valve 28 is arranged at the nitrogen discharge port 29, and the second valve 28 is connected to the main controller.

[0043] The operation process of the device for evaluating the low-temperature thickening performance of the drilling fluid of the present invention is as follows:

[0044] (1) Set the thickening temperature, load the drilling fluid into the thickening kettle 22, and fill the intermediate container 26 with oil fluid so that the height of the oil fluid is lower than the upper port of the thickening kettle 22;

[0045] (2) Open the first valve 3 to allow liquid nitrogen to flow into the interlayer of the quick-cooling box 5, add a refrigerant to the precooling box 16, and fill the refrigerant into the loop where the quick-cooling chamber 9, the second pipeline 10, the third pipeline 12, the sixth pipeline 19, the heater 21, the spiral tube 23, and the first water pump 7 are located;

[0046] (3) Obtain the temperature of the refrigerant in the quick-cooling chamber 9 through the first temperature sensor 6, denoted as the first temperature; obtain the temperature of the refrigerant in the precooling box 16 through the second temperature sensor 14, denoted as the second temperature; obtain the temperature inside the thickening kettle 22 through the third temperature sensor 24, denoted as the third temperature;

[0047] (4) A circuit is formed between the rapid cooling chamber 9 and the pre-cooling box 16 through the second three-way valve 11 and the first three-way valve 8. Then, the first water pump 7 is started to drive the refrigerant in the rapid cooling chamber 9, so that the refrigerant in the spiral tube 23 exchanges heat with the oil in the intermediate container 26, and then the oil exchanges heat with the drilling fluid in the thickening kettle 22;

[0048] (5) Carry out constant temperature control on the lost circulation plugging slurry for drilling fluid:

[0049] According to the difference between the third temperature obtained in step (3) and the thickening temperature set in step (1), determine the heat value that needs to be taken away when the current drilling fluid reaches the set thickening temperature, denoted as the first heat value; According to the first temperature obtained in step (3) and the flow rate of the refrigerant per unit time, determine the heat value that the refrigerant flowing out of the heater 21 can take away from the drilling fluid per unit time, denoted as the second heat value;

[0050] When the first heat value is greater than or equal to the second heat value, it means that the temperature in the thickening kettle 22 is still higher than the set thickening temperature, so the heat of the drilling fluid or the lost circulation plugging slurry for drilling fluid needs to be continuously taken away. At this time, the heater 21 is not used to heat the refrigerant;

[0051] When the first heat value is less than the second heat value, it means that the temperature of the drilling fluid or the lost circulation plugging slurry for drilling fluid has been lower than or will be lower than the set thickening temperature after heat exchange per unit time. Then, the refrigerant needs to be heated to prevent the temperature of the drilling fluid or the lost circulation plugging slurry for drilling fluid from being too low. At this time, the heater 21 is used to heat the refrigerant until the second heat value is equal to the first heat value;

[0052] When the second heat value is less than 0, it means that both the first temperature and the second temperature are higher than the temperature of the drilling fluid or the lost circulation plugging slurry for drilling fluid. At this time, the liquid nitrogen no longer has a cooling effect, and the liquid nitrogen in the interlayer of the rapid cooling box 5 needs to be replaced;

[0053] When the first temperature is lower than the threshold value of the refrigerant working temperature, by opening the second three-way valve 11, the outlet of the rapid cooling chamber 9 is communicated with the pre-cooling box 16, and by opening the third three-way valve 17, the pre-cooling box 16 and the heater 21 are communicated. All three ports of the first three-way valve 8 are communicated, the first water pump 7 is started to convey the refrigerant into the rapid cooling chamber 9, and at the same time, the second water pump 18 is started to convey the refrigerant to the heater 21, and the flow rate of the first water pump 7 is maintained to be greater than that of the second water pump 18; By adopting the way that the flow rate of the first water pump 7 is greater than that of the second water pump 18, the refrigerant coming out of the spiral tube 23 can be discharged into the rapid cooling chamber 9, and at the same time, the refrigerant in the pre-cooling box 16 is filled into the rapid cooling chamber 9 through the fifth pipeline 15, that is, the refrigerant in the pre-cooling box 16 is used to exchange heat with liquid nitrogen, so as to avoid the refrigerant losing the function of exchanging heat with the drilling fluid or the plugging slurry for drilling fluid leakage; The purpose of this way is also to avoid the refrigerant temperature being too low and freezing and not flowing, ensuring the sustainable operation of the thickening instrument; At the same time, in order to avoid the temperature of the refrigerant filled into the heater 21 by the second water pump 18 having too large a difference from the second temperature, the second water pump 18 and the second temperature sensor 14 are arranged adjacent to each other and preferably located at the bottom of the pre-cooling box 16, the end of the fifth pipeline 15 is also preferably arranged at the top of the pre-cooling box 16, and the fourth pipeline 13 is preferably arranged at the middle and upper part of the pre-cooling box 16;

[0054] When the second temperature is lower than the refrigerant working temperature threshold, it indicates that the refrigeration effect of liquid nitrogen on the refrigerant is too strong, and most of the refrigerant in the instrument will be lower than its normal working temperature. Therefore, the first valve 3 needs to be closed and the liquid nitrogen in the rapid cooling box 5 needs to be drained to ensure the normal operation of the refrigerant.

[0055] (6) Judge whether the third temperature reaches the set thickening temperature. If so, go to step (7); Otherwise, return to step (5);

[0056] (7) Add plugging material to the drilling fluid in the thickening kettle 22, and stir the drilling fluid with the plugging material added to form a plugging slurry for drilling fluid leakage;

[0057] (8) Place a torque sensor 27 into the plugging slurry for drilling fluid leakage, and seal the intermediate container 26;

[0058] (9) By filling the intermediate container 26 with oil, start the magnetic stirrer 20 to start thickening, and adopt the same method as in step (5) to control the temperature of the plugging slurry for drilling fluid leakage to be constant until the value of the torque sensor 27 reaches the thickening end value, close the first water pump 7, the second water pump 18 and the first valve 3, and drain the liquid nitrogen in the rapid cooling box 5 to obtain the thickening time.

[0059] If liquid nitrogen needs to be replenished into the interlayer during the thickening process, when the height of the liquid nitrogen in the interlayer remains unchanged, start the second motor 33 to make the threaded rod 31 drive the plug 30 to move towards the exhaust port 4 and seal the exhaust port 4, and close the first valve 3.

[0060] When the second heat value is less than 0, keep the first valve 3 closed, start the second motor 33 to move the plug 30 away from the exhaust port 4 to make the exhaust port 4 unobstructed, start the second valve 28 to let the liquid nitrogen in the interlayer flow away from the nitrogen discharge port 29, and after the liquid nitrogen in the interlayer has flowed away, close the second valve 28.

[0061] In the specific implementation process, in order to ensure that each port of the three-way valve can be automatically opened and closed, each three-way valve can adopt the method of separately setting an electric control valve at each port, which can not only realize the opening and closing of any two ports, but also realize the simultaneous opening and closing of all ports.

[0062] The thickening measurement part in the present invention can adopt existing solutions, that is, the magnetic stirrer 20, the thickening kettle 22, the intermediate container 26 and the torque sensor 27 can all adopt existing solutions. The magnetic stirrer 20 can be driven by a driving motor located below the intermediate container 26 to drive the thickening kettle 22 to rotate. The torque sensor 27 includes a rubber ring located on the upper surface of the drilling fluid loss plugging slurry (to prevent the drilling fluid loss plugging slurry from escaping from the thickening kettle 22), and also includes a blade that passes through the rubber ring and penetrates into the drilling fluid loss plugging slurry. When the thickening kettle 22 rotates, the thickening kettle 22 drives the drilling fluid loss plugging slurry to rotate, and the drilling fluid loss plugging slurry applies a driving force to the blade. As the drilling fluid loss plugging slurry thickens, the driving force on the blade will also increase. When the value obtained by the torque sensor 27 reaches the set value, it means that the drilling fluid loss plugging slurry has reached the set thickening state, that is, the thickening test is over, and recording the time at this time can obtain the corresponding thickening data.

[0063] II. The method for evaluating the low-temperature thickening performance of the drilling fluid of the present invention.

[0064] The above device essentially realizes the thickening test of the working fluid according to the following method, including the following steps: First, use liquid nitrogen to cool the refrigerant, then use the refrigerant circulation loop formed by the cooled refrigerant to exchange heat with the drilling working fluid to adjust the temperature of the drilling working fluid to the low-temperature thickening temperature below 0°C, and finally measure the low-temperature thickening performance of the drilling working fluid at this temperature.

[0065] Furthermore, in order to improve the accuracy of evaluating the low-temperature thickening performance, the thickening temperature is controlled at a constant temperature in the following manner: According to the actual temperature of the drilling working fluid and the preset thickening temperature, determine the heat value that needs to be taken away, denoted as the first heat value; Determine the heat value that the refrigerant can take away from the drilling working fluid per unit time according to the temperature change of the refrigerant per unit time, denoted as the second heat value;

[0066] When the first heat value is less than the second heat value, heat the refrigerant until the second heat value is equal to the first heat value; When the first heat value is greater than or equal to the second heat value, do not heat the refrigerant.

[0067] Further, when the second heat value is less than 0, it indicates that both the actual temperature of the drilling fluid and the temperature of the refrigerant are higher than the thickening temperature. At this time, liquid nitrogen no longer has a cooling effect, and new liquid nitrogen needs to be replaced.

[0068] Further, after the liquid nitrogen cools the refrigerant and the temperature of the refrigerant is lower than the refrigerant working temperature threshold, the refrigerant will freeze and not flow due to the too low temperature, affecting the cooling of the drilling fluid. Therefore, it is necessary to update the refrigerant at the liquid nitrogen cooling position and / or heat the refrigerant circulation loop to raise the temperature of the refrigerant above the working temperature threshold.

[0069] Further, in order to facilitate the update of the refrigerant at the liquid nitrogen cooling position, a refrigerant replenishment device is connected between the upstream and downstream of the liquid nitrogen cooling position, and the update is to establish a refrigerant circulation between the liquid nitrogen cooling position and the refrigerant replenishment device.

[0070] Further, in order to improve the cooling efficiency of the drilling fluid, the thickening of the drilling fluid is carried out in an oil environment to increase the contact area between the drilling fluid and the cooling environment, and then the oil is cooled through the refrigerant circulation loop.

[0071] Further, the drilling fluid is a lost circulation plugging slurry for drilling. First, the drilling fluid is cooled to the thickening temperature by the refrigerant circulation loop, and then the plugging material is added to the cooled drilling fluid for thickening performance evaluation. This can avoid shortening the time for the lost circulation plugging slurry for drilling to cool down to the set thickening temperature and improve the accuracy of the thickening performance evaluation.

[0072] Specifically, the implementation manner of the low-temperature thickening performance evaluation method for the drilling fluid is as follows:

[0073] Specifically, the following steps are adopted:

[0074] (1) Set the thickening temperature to -10 °C, the thickening pressure to 20 MPa, and the thickening end value to 100 Bc; fill 450 mL of polysulfonate drilling fluid into the thickening kettle 22, and fill the oil in the intermediate container 26 so that the height of the oil is lower than the upper port of the thickening kettle 22;

[0075] (2) Open the first valve 3 to allow liquid nitrogen to flow into the interlayer of the quick-cooling box 5; add refrigerant to the pre-cooling box 16, and fill the refrigerant into the loop where the quick-cooling chamber 9, the second pipeline 10, the third pipeline 12, the sixth pipeline 19, the heater 21, the spiral pipe 23, and the first water pump 7 are located;

[0076] (3) Start the first water pump 7 to displace the refrigerant in the rapid cooling chamber 9, form a loop between the rapid cooling chamber 9 and the pre-cooling box 16 through the second three-way valve 11 and the first three-way valve 8. At the same time, make the refrigerant in the spiral tube 23 exchange heat with the oil in the intermediate container 26, and then exchange heat between the oil and the drilling fluid in the thickening kettle 22;

[0077] (4) When the third temperature reaches -10 °C, add plugging material to the drilling fluid in the thickening kettle 22, and stir the drilling fluid with the added plugging material to form a drilling fluid loss plugging slurry; put a torque sensor 27 into the drilling fluid loss plugging slurry and seal the intermediate container 26;

[0078] (5) Fill the intermediate container 26 with oil, start the magnetic stirrer 20 to start thickening, and perform constant temperature control on the drilling fluid loss plugging slurry until the value of the torque sensor 27 reaches 100 Bc. Then turn off the first water pump 7, turn off the second water pump 18, turn off the first valve 3, and drain the liquid nitrogen in the rapid cooling box 5 to obtain a thickening time of 204 min.

[0079] The low-temperature drilling fluid loss plugging slurry used in the test is composed of the following components by mass percentage: 72% polysulfonate drilling fluid, 28% plugging material; among which the plugging material is composed of the following components by mass percentage: 80% low-temperature-resistant G-class oil well cement, 2% polyvinyl alcohol, 2.5% calcium chloride, 4% sodium chloride, 2.5% ethylene glycol, 1.5% triethanolamine, 1% calcium formate, 3% tartaric acid, 1.6% lignosulfonate, 1.5% glass microspheres (density 0.35 g / cm 3 ), 0.4% polyether-modified polysiloxane.

[0080] In other implementation cases, when the heat value that the refrigerant can take away from the drilling working fluid per unit time is greater than the difference between the actual temperature of the drilling working fluid and the preset thickening temperature, the third temperature can be made to reach the thickening temperature by heating the refrigerant; when the heat value that the refrigerant can take away from the drilling working fluid per unit time is less than or equal to the difference between the actual temperature of the drilling working fluid and the preset thickening temperature, there is no need to heat the refrigerant, and the refrigerant circulation is carried out normally.

[0081] In other implementation cases, when the heat value that the refrigerant can take away from the drilling working fluid per unit time is less than 0, the liquid nitrogen can be replaced.

[0082] In other implementation cases, when the temperature of the refrigerant in the rapid cooling chamber 9 is lower than the refrigerant working temperature threshold, the normal circulation of the refrigerant can be realized by updating the refrigerant in the rapid cooling chamber 9; the normal circulation of the refrigerant can also be realized by heating the refrigerant in the refrigerant circuit; the normal circulation of the refrigerant can also be realized by synchronously updating and heating the refrigerant.

Claims

1. A method for evaluating the low-temperature thickening performance of a drilling fluid, characterized in that, it includes the following steps: Cool the refrigerant through liquid nitrogen, and then use the refrigerant circulation loop formed by the cooled refrigerant to cool the drilling fluid to the thickening temperature, where the thickening temperature is lower than 0 °C, and evaluate the low-temperature thickening performance at the thickening temperature.

2. The method for evaluating the low-temperature thickening performance of a drilling fluid according to claim 1, characterized in that, The thickening temperature is controlled at a constant temperature in the following manner: According to the actual temperature of the drilling fluid and the thickening temperature, determine the heat value to be removed, denoted as the first heat value; determine the heat value that the refrigerant can remove from the drilling fluid per unit time, denoted as the second heat value; When the first heat value is less than the second heat value, heat the refrigerant; when the first heat value is greater than or equal to the second heat value, do not heat the refrigerant.

3. The method for evaluating the low-temperature thickening performance of a drilling fluid according to claim 2, characterized in that, When the second heat value is less than 0, replace the liquid nitrogen.

4. The method for evaluating the low-temperature thickening performance of a drilling fluid according to claim 1, characterized in that, After the liquid nitrogen cools the refrigerant below the refrigerant working temperature threshold, update the refrigerant at the liquid nitrogen cooling position and / or heat the refrigerant circulation loop.

5. The method for evaluating the low-temperature thickening performance of a drilling fluid according to claim 4, characterized in that, Connect a refrigerant replenishing device between the upstream and downstream of the liquid nitrogen cooling position, and the update is to establish a refrigerant circulation between the liquid nitrogen cooling position and the refrigerant replenishing device.

6. The method for evaluating the low-temperature thickening performance of a drilling fluid according to claim 1, characterized in that, The thickening of the drilling fluid is carried out in an oil environment, and the refrigerant circulation loop is used to cool the oil.

7. The method for evaluating the low-temperature thickening performance of a drilling fluid according to any one of claims 1-6, characterized in that, The drilling fluid is a lost circulation plugging slurry for drilling fluid. First, add the drilling fluid, and after the refrigerant circulation loop cools the drilling fluid to the thickening temperature, then add the plugging material to the drilling fluid for thickening performance evaluation.

8. A device for evaluating the low-temperature thickening performance of a drilling fluid, characterized in that, It includes a thickening kettle and a refrigerant circulation loop. The refrigerant circulation loop includes a thickening refrigeration section for cooling the thickening kettle and an external section connected to the thickening refrigeration section. The external section includes a liquid nitrogen refrigeration section. The evaluation device also includes a liquid nitrogen refrigeration bin, and the liquid nitrogen refrigeration bin has a refrigeration inner cavity for accommodating liquid nitrogen. The liquid nitrogen refrigeration section is arranged in the refrigeration inner cavity, and a circulation pump is also arranged on the refrigerant circulation loop.

9. The device for evaluating the low-temperature thickening performance of a drilling fluid according to claim 8, characterized in that, A first temperature sensor for detecting the temperature of the working liquid is arranged on the thickening kettle, a second temperature sensor is arranged on the liquid nitrogen refrigeration section, and a heater is connected to the refrigerant circulation loop; the first temperature sensor, the second temperature sensor, and the heater are connected to the main controller; According to the actual temperature of the first temperature sensor and the thickening temperature, determine the heat value to be removed, denoted as the first heat value; Determine the heat value that the refrigerant can take away from the drilling fluid per unit time according to the temperature of the second temperature sensor, denoted as the second heat value; compare the magnitudes of the first heat value and the second heat value, and combine with the on / off of the heater to achieve constant temperature control.

10. The device for evaluating the low-temperature thickening performance of the drilling fluid according to claim 9, characterized in that, the device for evaluating the low-temperature thickening performance further includes a refrigerant storage bin, the refrigerant storage bin has a refrigerant extraction port and a refrigerant return port, the refrigerant extraction port and the refrigerant return port are respectively connected to the upstream and downstream of the liquid nitrogen refrigeration section, and a first valve and a second valve are respectively arranged on the connecting pipelines of the refrigerant extraction port, the refrigerant return port and the refrigerant circulation circuit.

11. The device for evaluating the low-temperature thickening performance of the drilling fluid according to claim 10, characterized in that, the first valve, the second valve are connected to the main controller, when the temperature value of the second temperature sensor is lower than the refrigerant working temperature threshold, the first valve and the second valve are opened, and the refrigerant storage bin is used to update the refrigerant in the liquid nitrogen refrigeration section.

12. The device for evaluating the low-temperature thickening performance of the drilling fluid according to claim 10, characterized in that, the connecting pipeline of the refrigerant extraction port and the refrigerant circulation circuit forms a first extraction pipeline, and a second extraction pipeline is further connected between the bottom of the refrigerant storage bin and the refrigerant circulation circuit downstream of the liquid nitrogen refrigeration section.

13. The device for evaluating the low-temperature thickening performance of the drilling fluid according to any one of claims 8-12, characterized in that, the device for evaluating the low-temperature thickening performance further includes an intermediate container, the intermediate container has an inner cavity for accommodating oil, the thickening kettle is arranged in the inner cavity, and the thickening refrigeration section is a spiral pipe section spirally wound around the outer periphery of the thickening kettle.

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