CN206233918U - Oil/gas Well cement sheath sealing integrity test device - Google Patents

Abstract

The utility model is related to a kind of Oil/gas Well cement sheath sealing integrity test device, simulation wellbore hole including autoclave pressure and inside autoclave pressure, test device also includes control pressurer system, temperature control system, channelling detecting system, strain measurement system and mud cake simulation system；Simulation wellbore hole includes sleeve pipe and the rock core positioned at sleeve pipe periphery, and annular gap is formed between sleeve pipe and rock core, and cement sheath is formed in annular gap；The upper and lower ends of sleeve pipe and rock core are respectively equipped with upper end cover and bottom end cover.The utility model can be realized to cement sheath institute's bearing temperature under the difference working condition of underground and the true simulation from sleeve pipe, complex formation load, processing range covers Oil/gas Well and bores completion phase cementing well, and pressure testing, pilot production in production process, circulation note are adopted and the transformation operating mode such as pressure break.The utility model can be by changing the factors such as cement thickness, mud cake property, curing temperature, to evaluate its affecting laws to cement sheath sealing integrity.

Description

Oil and gas well cement sheath seal integrity test device

technical field

The utility model belongs to the field of oil and gas resource development, and in particular relates to a device capable of simulating complex loads of casings and formations borne by a cement sheath under downhole working conditions, and testing the cement sheath for sealing integrity.

Background technique

Control of fluids in the wellbore and in the formation is a top priority at all stages in the life cycle of an oil and gas well. If fluids flow uncontrolled, the physical and functional integrity of the well is lost, with potentially serious, even catastrophic consequences. As an important part of the wellbore of oil and gas wells, the cement sheath is mainly used to prevent formation fluid channeling during drilling, production and reconstruction, and to effectively fix and support the casing. In recent years, with the deepening of the exploration and development process, most oilfields have entered the middle and late stages of development, and stimulation measures such as fluid injection, acidizing, and fracturing have been widely used, but more and more wells have experienced annular pressure and interlayer pressure. The problem of cement sheath seal integrity failure such as channeling, especially for high-pressure gas wells, the anomaly of annular pressure in the production process is very common, and the sealing performance is a direct measure of the integrity of the cement sheath, how to achieve accurate and quantitative evaluation very important. Therefore, it is of great significance to carry out the evaluation of the integrity of the cement sheath seal to determine the production measures and prolong the life cycle of oil and gas wells.

At present, for the test method of cement sheath seal integrity, logging instruments such as sonic logging (CBL) and variable density (VDL) are mainly used to judge the cementing interface in the oilfield field, and there are also direct use of perforation holes to check the layer. However, this test may fracture or plug the formation, or even cause damage to the cement interface. The test instruments and methods in the laboratory mainly include: shear bond strength evaluation device, hydraulic cementation and permeability evaluation device, cement stone compressive strength measurement method, cementing two-interface isolation ability simulation evaluation device and cementing cement sheath. Mechanical integrity test devices, etc. Most of the above test instruments use the interface shear strength and cement stone compressive strength as evaluation indicators, and very few instruments use the actual sealing and sealing of the cement sheath as evaluation indicators. Even so, due to the limitations of the experimental conditions, the above methods have greatly simplified the actual downhole working conditions, or directly simplified to equivalent physical experiments, resulting in the inability to simulate the actual stress state of the cement sheath in the downhole. Therefore, it is currently difficult to accurately evaluate the integrity of the cement sheath seal under downhole working conditions, whether it is indoor experimental testing or field engineering application.

Chinese patent CN 104153760A oil and gas well cement sheath sealing performance simulation testing device and experimental method discloses a kind of oil and gas well cement sheath sealing performance simulation testing device, including kettle body, upper kettle cover, lower kettle cover, heating jacket, booster pump, drain Pressure pumps, liquid volume and gas volume recorders, and multiple pipelines are connected to control and test confining pressure, pressure relief, and casing pressure. However, according to the actual operation of this research group, the sealing performance of this device is not good enough. , mainly because the connection structure between the pressure plate and the upper kettle cover used with different sizes of casings cannot bear too much pressure difference, so the predetermined goal can only be achieved to a certain extent. Furthermore, this device can only realize the measurement of the influence of cement sheath loading and cement sheath sealing characteristics, and the actual downhole cement sheath needs to bear multiple pressures. Only by loading the cement sheath to measure the characteristics of the cement sheath sealing cannot meet the needs of comprehensive measurement. .

Utility model content

According to the above shortcomings, the purpose of this utility model is to provide a device that can simulate the casing and formation complex loads that the cement sheath bears under the downhole working conditions, and test the sealing integrity of the cement sheath.

In order to achieve the above object, the technical solution of the present utility model is: an oil and gas well cement sheath seal integrity testing device, including a pressure kettle and a simulated wellbore located inside the pressure kettle, the testing device also includes a pressure control system, a temperature control system, a channeling Flow detection system, strain measurement system and mud cake simulation system;

The simulated wellbore includes a casing and a core located on the periphery of the casing, an annular gap is formed between the casing and the core, and a cement sheath is formed in the annular gap; an upper end cover and a lower end cover are respectively provided at the upper and lower ends of the casing and the core;

The pressure kettle includes a kettle body and a kettle cover matched with the kettle body; the kettle body is provided with a cement sheath pressure port connected with the top of the cement sheath and a channel inspection port connected with the bottom of the cement sheath; The confining pressure port and the pressure relief port communicated with the lower end of the core periphery; the kettle body is provided with a thermocouple port for installing a heating couple; The cover is provided with a communication port for connecting the displacement measuring device or the drilling fluid storage tank;

The pressure control system includes pipeline 1 connected to the confining pressure port, pipeline 2 connected to the cement sheath pressure port, pipeline 4 connected to the casing pressure port and pipeline 5 connected to the pressure relief port;

Pipeline 1 is connected with stop valve 1, pressure sensor 1, pressure regulating valve 1, gas booster pump, pressure control instrument and nitrogen source, and the gas booster pump is connected with compressed air source;

Pipeline 2 is connected with stop valve 2, stop valve 4, pressure sensor 2, pressure regulating valve 2 and stop valve 7;

The pipeline four is connected with a pressure sensor four, a liquid booster pump and a water source, and the liquid booster pump is connected with a compressed air source;

Pipeline five is connected with shut-off valve eight and drain pipe;

The temperature control system includes a thermocouple connected to the thermocouple port and installed inside the kettle body. The thermocouple is also connected to the temperature control instrument. There is a cooling pipe wrapped around the outside of the kettle body, and the cooling pipe is connected to the water source;

The channeling detection system includes a pipeline 3 connected to the channeling inspection port, and the pipeline 3 is connected with a shut-off valve 6, a pressure sensor 3, a shut-off valve 10 and a channeling monitoring device;

The strain measurement system is a displacement measuring device that penetrates into the casing through the communication port on the kettle cover to measure the radial displacement of the inner wall of the casing;

The mud cake simulation system includes a drilling fluid storage tank and a core filter. The upper and lower ends of the drilling fluid storage tank are respectively provided with stop valves 12 and 13. The liquid storage barrel is connected with the lid of the kettle; the core filter is embedded in the outer wall of the core.

Preferably, branch line 6 is connected to line 1 and line 2, stop valve 5 is connected to branch line 6, and the connection point between branch line 6 and line 2 is located at the cement sheath pressure port and stop valve 2 Between, the connection point between the branch line six and the line one is located between the confining pressure port and the stop valve one.

Preferably, the branch pipeline 7 is connected to the pipeline 2 and the branch pipeline 6, and the branch pipeline 7 is provided with a shut-off valve 3 and a dehydration tank, and the connection point between the branch pipeline 7 and the pipeline 2 is located at the shut-off valve 2 and Between pressure regulating valve two, the connection point of branch pipeline seven and branch pipeline six is located between the cement ring pressure port and stop valve two.

Preferably, the third pipeline is connected with the eighth branch pipeline, the eighth branch pipeline is provided with the back pressure valve one and the stop valve eleven, and the end of the eighth branch pipeline is connected with the drain pipe.

It is preferable that the branch pipeline 9 is connected to the pipeline 5, the back pressure valve 2 is arranged on the branch pipeline 9, and the connection point between the branch pipeline 9 and the pipeline 5 is located between the liquid booster pump and the pressure sensor 4, The end of the branch pipeline nine is connected with the drain pipe.

It is preferable that branch pipeline ten is connected to pipeline five, and shut-off valve nine is arranged on branch pipeline ten. The connection point of branch pipeline ten and pipeline five is located between pressure sensor four and casing pressure port, and The end of pipeline ten is connected with drainpipe.

Preferably, the inner bottom surface of the kettle body is provided with a positioning boss.

Preferably, a filter screen is provided at the lower end of the cement sheath.

Preferably, connecting members are provided between the kettle body and the kettle cover, between the communication port of the kettle cover and the displacement measuring device, and between the communication port of the kettle cover and the drilling fluid storage barrel.

The utility model also provides a method for evaluating the integrity of the oil and gas well cement sheath seal integrity test device, including the following process:

(1) Cement sheath seal integrity test

a The formation of mud cake on the inner wall of the core

Put the core filter on the periphery of the prepared annular columnar core, put it on the positioning boss on the bottom of the kettle body, press and seal it with the lid of the kettle, configure the drilling fluid according to the experimental requirements, close the stop valve 13 at the lower end of the drilling fluid storage barrel, Open the stop valve 12 at the upper end, and pour the drilling fluid into the drilling fluid storage barrel. The volume of the drilling fluid can be determined according to the needs of the experiment. Close the stop valve 12, and screw the drilling fluid storage barrel into the connecting port of the kettle cover. The air guide pipe from the nitrogen cylinder is connected to the top of the drilling fluid storage barrel, close the stop valve 1, stop valve 5, stop valve 6 and stop valve 9, open the stop valve 8, stop valve 12 and stop valve 13, and adjust the nitrogen bottle The output pressure is 0.5-1.0MPa. Turn on the pressure regulating valve switch of the nitrogen bottle to output nitrogen. The recording time is 15-30 minutes. Stop valve 12 and stop valve 13, remove the drilling fluid storage tank and kettle cover, take out the core, wash off the virtual mud cake on the mud cake with slowly flowing water, and measure the actual mud cake thickness with a special caliper;

b Simulate the maintenance process of downhole cement slurry

b1 Simulation of cement slurry curing under constant pressure conditions in the wellbore

After the mud cake is formed, the core and the casing are embedded on the lower end cap, and cement slurry with different properties is prepared according to the experimental requirements, and the cement slurry is slowly injected into the annular space between the casing and the core, and the upper end cap is used to press the slurry after filling. Tightly seal, put the assembled simulated shaft into the kettle body, ensure a good seal between the lower end cover and the kettle body, then tighten the kettle cover, screw the displacement measuring device into the connection port on the top of the kettle cover, and connect the system data acquisition software , open the stop valve 3 and stop valve 5, after the water in the kettle body is completed, set the temperature of the kettle body to 75-150°C according to the demand, set the pressure values of the casing, the cement annulus and the confining pressure to be equal, and the casing The upper limit of the pipe pressure is 40MPa, the upper limit of the cement sheath and confining pressure is 30MPa, turn on the liquid booster pump and the gas booster pump, and turn on the thermocouple to work, so as to realize the cement slurry curing under the condition of equal pressure in the simulated wellbore ;

b2 Cement slurry curing under simulated casing pressure holding condition

Repeat the operation of b1, and set the pressure values of the casing, cement annulus and confining pressure so that the pressure inside the casing is greater than the pressure values of the cement annulus and confining pressure outside the casing;

c Cement sheath seal integrity test under different working conditions

c1 Test the integrity of the cement sheath seal by adjusting the pressure difference between the top and bottom of the cement sheath

After the curing of the cement slurry is completed, close the stop valve 3, open the stop valve 2, close the stop valve 5, and open the stop valve 9. At this time, the back pressure of the cement sheath at the inspection end will rise to the same pressure as the cement sheath, and then close the stop valve. Valve 9, open stop valve 11, adjust back pressure valve 1, reduce the pressure difference at the bottom of the cement ring and form a pressure difference at the top of the cement ring, close the stop valve 11, fill the water tank with water, and open the stop valve Ten and stop valve six, test the sealing integrity of the cement sheath under the current working conditions; different pressure difference intervals can be selected during the test, such as 2MPa, that is, a channeling test will be performed every time the back pressure of the cement sheath decreases by 2MPa.

c2 Test the integrity of the cement sheath seal by adjusting the pressure inside the casing

Open stop valve 9, open stop valve 11, adjust back pressure valve 1 to form a fixed pressure difference between the top and bottom of the cement ring and after the pressure difference is stable, close stop valve 11; adjust back pressure valve 2 , unload the inner pressure of the casing at fixed intervals until the inner pressure of the casing is zero; conduct a channeling test every time the internal pressure of the casing is unloaded during this period, if no channeling occurs, continue to adjust the back pressure valve 2; adjust the inner pressure of the casing to the original After the pressure, the casing is pressurized at fixed intervals, and the above casing pressure unloading process is repeated after each casing pressurization and the channeling test is performed until the seal integrity of the cement sheath fails;

During the test, the channeling test will be carried out under the condition that the internal pressure of the casing is greater than the external pressure and compared with the original test results to determine whether the sealing failure has occurred at the cementing interface or the second interface; use the monitoring results of the displacement measuring device to judge The size of the cementing-interface micro-annulus;

(2) Channeling experiment of microannulus with different sizes

In the b2 process, after simulating the cement slurry curing under the condition of casing holding pressure, close the stop valve 3, open the stop valve 2, select the channeling mode, close the stop valve 5, open the stop valve 9, and make the top and bottom of the cement ring After a fixed pressure difference is formed and stabilized, close the shut-off valve 11, adjust the back pressure valve 2, and unload the pressure in the casing at fixed intervals until the internal pressure of the casing is zero. Use the monitoring results of the displacement measuring device to judge the size of the cementing-interface micro-annulus;

(3) Pressure bearing and sealing capacity test of cement slurry with different characteristics

According to the test needs, configure cement slurry systems with different properties for maintenance. After the maintenance is completed, close the stop valve 3, open the stop valve 2, and select the channeling mode; close the stop valve 5. Open stop valve 9, at this time, the back pressure of the cement sheath at the inspection end will rise to the same pressure as the cement sheath, then close the stop valve 9, open the stop valve 11, adjust the back pressure valve 1, and put the cement sheath at the bottom of the cement sheath for inspection. After the pressure drops and the pressure difference is formed at the top of the cement sheath, close the shut-off valve 11, fill the channel inspection water tank with water, open the shut-off valve 10 and the shut-off valve 6 for testing, and gradually increase the pressure difference at the top and bottom of the cement sheath during the test, if If the back pressure at the bottom of the cement sheath increases during the test, the current pressure difference is regarded as the ultimate sealing pressure of the cement slurry;

(4) Analysis of the influence of different factors on the integrity of the cement sheath seal

a Mud cake properties: different mud cake thickness can be obtained by changing the gas source pressure and time; different mud cake properties can be obtained by changing the core lithology and drilling fluid formula;

b Cement sheath thickness: comparative experiments are carried out by selecting casings of different sizes and upper and lower end caps of different internal structural sizes;

c Curing temperature and pressure: through the temperature control instrument and the pressure control instrument, respectively carry out programming temperature control and pressure control, and set the temperature and pressure changes during the cement slurry curing process.

The utility model has the following beneficial technical effects:

(1) The utility model can realize the real simulation of the temperature of the cement sheath under different working conditions in the well and the complex loads from the casing and the formation. Pressure test, production test, cycle injection and production, fracturing and other reconstruction conditions.

(2) The main function of the cement sheath is to seal and seal the outer annulus of the casing to prevent formation fluid channeling in the process of drilling, production and reconstruction. This device and evaluation method are evaluated based on the equivalent permeability of the cement annulus The index realizes the effective evaluation of the sealing integrity of the cement sheath and the sealing ability of the cement sheath.

(3) Realized the simulation of the formation of mud cakes with different thicknesses and properties of the inner wall of the core under wellbore conditions, more realistically simulated the actual conditions of the wellbore, and further restored the conditions of the cement sheath in the downhole.

(4) Realized the simulation of the cement slurry curing process under the condition of heating and pressurization, especially realized the simulation of the cement slurry curing process under the condition of casing holding pressure, and then simulated the micro-annulus caused by holding pressure and waiting for coagulation . And by selecting the casing material and controlling the pressure difference between the inside and outside of the casing, the formation of micro-annulus of different sizes is simulated.

(5) The strain measurement system is used to realize the real-time measurement of the radial deformation of the casing under different pressure load conditions during the whole test process, so the monitoring and size measurement of the cementing-interface micro-annulus can be further realized.

(6) The utility model can evaluate the rule of influence on the sealing integrity of the cement sheath by changing the thickness of the cement sheath, the properties of the mud cake, the curing temperature and other factors. It can also test the pressure bearing and sealing capacity of cement slurry with different characteristics by changing the cement slurry formula, providing a basis for the selection of oil and gas well cement slurry design, thin interlayer fracturing technology and horizontal well staged fracturing technology.

Description of drawings

Fig. 1 is a structural representation one of the utility model;

Fig. 2 is the structural representation two of the utility model;

Fig. 3 is a structural schematic diagram of the pressure vessel and the simulated shaft of the utility model.

In the figure, 1-displacement measuring device; 2-connecting member; 3-kettle cover; 4-upper end cover; 5-containing pressure port; 6-casing; 7-core; - Check port; 11- Lower end cover; 12- Casing pressure port; 13- Seal; 14- Pressure relief port; 15- Thermocouple port; 16- Cooling pipe; 17- Cement ring pressure port; 18- Communication port ;19-positioning boss; 20-core filter; 21-stop valve two; 22-stop valve four; 23-stop valve three; 24-pressure sensor two; 25-pressure regulating valve two; 26-stop valve five; 27-stop valve one; 28-pressure sensor one; 29-pressure regulating valve one; 30-gas booster pump; 31-stop valve seven; 32-pressure control instrument; 33-compressed air source; 34-nitrogen source; 35 -stop valve six; 36-pressure sensor three; 37-stop valve ten; 38-water tank; 39-liquid flow meter; 40-back pressure valve one; 41-stop valve eleven; Four; 44-stop valve nine; 45-back pressure valve two; 46-liquid booster pump; 47-water source; 48-stop valve eight; 49-temperature control instrument; Connecting member; 53-stop valve 13; 54-drilling fluid storage barrel; 55-stop valve 12; 56-nitrogen cylinder.

detailed description

Below in conjunction with specific embodiment the utility model is described further.

An oil and gas well cement sheath seal integrity test device as shown in Figure 1-3, including a pressure kettle and a simulated wellbore inside the pressure kettle, the test device also includes a pressure control system, a temperature control system, and channeling detection system, a strain measurement system and a mud cake simulation system; wherein, the simulated wellbore includes a casing 6 and a core 7 located on the periphery of the casing 6, an annular gap is formed between the casing 6 and the core 7, and a cement sheath 8 is formed in the annular gap; The upper and lower ends of the pipe 6 and the rock core 7 are respectively provided with an upper end cover 4 and a lower end cover 11; the autoclave includes a kettle body 9 and a kettle lid 3 matched with the kettle body 9; The cement sheath pressure port 17 and the channel inspection port 10 communicating with the bottom of the cement sheath 8; the kettle body 9 is provided with a confining pressure port 5 communicating with the upper end of the outer periphery of the rock core 7 and a pressure relief port 14 communicating with the outer peripheral lower end of the rock core 7; the kettle body 9 A thermocouple port 15 for installing a heating couple is provided; the kettle body 9 is provided with a casing pressure port 12 communicated with the casing 6 and arranged at the lower end of the kettle body 9; the kettle cover 3 is provided with a displacement measuring device 1 or The communication port 18 of the drilling fluid storage tank 54; the pressure control system includes the first pipeline connected to the confining pressure port 5, the second pipeline connected to the cement sheath pressure port 17, the fourth pipeline connected to the casing pressure port 12 and The pipeline five connected with the pressure relief port 14; the pipeline one is connected with a shut-off valve one 27, a pressure sensor one 28, a pressure regulating valve one 29, a gas booster pump 30, a pressure control instrument 32 and a nitrogen source 34, and the gas booster The pressure pump 30 is connected to the compressed air source 33; the second pipeline is connected with the second shut-off valve 21, the fourth shut-off valve 22, the second pressure sensor 24, the second pressure regulating valve 25 and the seventh shut-off valve 31; the fourth pipeline is connected with the pressure sensor Four 43, liquid booster pump 46 and water source 47, liquid booster pump 46 links to each other with compressed air source 33; Pipeline five is connected with stop valve eight 48 and drainpipe 42; The thermocouple arranged inside the kettle body 9 is also connected to the temperature control instrument 49, the outside of the kettle body 9 is wound with a cooling pipe 16, and the cooling pipe 16 is connected to the water source 47; The pipeline three is connected with the stop valve six 35, the pressure sensor three 36, the stop valve ten 37 and the channeling monitoring device; the strain measurement system penetrates into the casing 6 through the communication port 18 on the kettle cover 3 for measurement The displacement measuring device 1 for the radial displacement of the inner wall of the casing 6; the mud cake simulation system includes a drilling fluid storage barrel 54 and a core filter 20, and the upper and lower ends of the drilling fluid storage barrel 54 are respectively provided with a stop valve 12 55 and a stop valve 10 Three 53, the upper end of the drilling fluid storage barrel 54 is connected to the nitrogen cylinder 56 through the air duct, and the drilling fluid storage barrel 54 is connected to the kettle cover 3; the core filter 20 is nested on the outer wall of the rock core 7.

Further, pipeline 1 and pipeline 2 are connected with branch pipeline 6, and branch pipeline 6 is connected with stop valve 5 26, and the connection point between branch pipeline 6 and pipeline 2 is located at cement sheath pressure port 17 and the stop valve Between the two 21, the connection point between the branch pipeline six and the pipeline one is located between the confining pressure port 5 and the stop valve one 27.

Further, branch pipeline 7 is connected to pipeline 2 and branch pipeline 6, and shut-off valve 3 23 and water loss bucket 50 are arranged on branch pipeline 7, and the connection point between branch pipeline 7 and pipeline 2 is located at shut-off valve 2 21 and pressure regulating valve 2 25, the connection point of branch pipeline 7 and branch pipeline 6 is located between cement sheath pressure port 17 and stop valve 2 21.

Further, the third pipeline is connected with the eighth branch pipeline, and the eighth branch pipeline is provided with a back pressure valve 1 40 and a shut-off valve 11 41 , and the end of the eighth branch pipeline is connected with the drain pipe 42 .

Further, branch line nine is connected to line five, and back pressure valve two 45 is arranged on branch line nine, and the connection point between branch line nine and line five is located between liquid booster pump 46 and pressure sensor four 43 Between, the end of the branch pipeline nine is connected with the drain pipe 42.

Further, pipeline five is connected with branch pipeline ten, and branch pipeline ten is provided with shut-off valve nine 44, and the connection point between branch pipeline ten and pipeline five is located between pressure sensor four 43 and casing pressure port 12 , the end of the branch pipeline ten is connected with the drain pipe 42.

Further, the inner bottom surface of the kettle body 9 is provided with a positioning boss 19 .

Further, a filter screen 51 is provided at the lower end of the cement sheath 8 .

Further, connecting members 2 are provided between the kettle body 9 and the kettle cover 3 , between the communication port 18 of the kettle cover and the displacement measuring device 1 , and between the communication port 18 of the kettle cover and the drilling fluid storage barrel 54 .

Further, seals 13 are provided between the kettle body 9 and the kettle cover 3 , between the sleeve pipe 6 , the rock core 7 and the upper end cover 4 , and between the lower end cover 11 and the kettle body 9 .

The method of testing and evaluating the sealing integrity of the cement sheath of oil and gas wells using this device is described in detail as follows in conjunction with Figure 1-2:

1. Cement sheath seal integrity test

a The formation of mud cake on the inner wall of the core

As shown in Figure 2, at first the core filter screen 20 is set on the outer periphery of the made annular columnar rock core 7, then the rock core 7 is put into the kettle body 9, and placed on the positioning boss 19 on the bottom surface of the kettle body 9, and the Cover 3 is compressed and sealed. Configure the drilling fluid according to the experimental requirements, close the lower stop valve 13 53 of the drilling fluid storage barrel 54, and open the upper stop valve 12 52, place a funnel at the top nozzle to guide the flow, pour the drilling fluid into the drilling fluid storage barrel 54, and drill The volume of the liquid can be determined according to the needs of the experiment, generally 2-3 times the inner volume of the core. Close the stop valve 12 52, screw the drilling fluid storage barrel 54 into the still cover communication port 18, and connect the air guide pipe drawn from the nitrogen cylinder 56 to the top of the drilling fluid storage barrel 54. Close stop valve one 27, stop valve five 26, stop valve six 35 and stop valve nine 44, open stop valve eight 48, open stop valve twelve 55 and stop valve thirteen 53. Adjust the nitrogen bottle 56 output pressure to 0.5-1.0MPa, open the nitrogen bottle 56 pressure regulating valve switch to output nitrogen, record the time, the time is generally 15-30 minutes, after reaching the time required for the experiment, close the nitrogen bottle 56 switch. Close stop valve 12 55 and stop valve 13 53, disassemble the drilling fluid storage tank 54 and kettle cover 3, take out the core 7, wash off the virtual mud cake on the mud cake with slowly flowing water, and measure the actual mud cake with a special caliper. Mudcake thickness. In the above formation methods, different mud cake thicknesses can be obtained by changing the gas source pressure and time; different mud cake properties can be obtained by changing the core lithology and drilling fluid formula.

b Simulate the maintenance process of downhole cement slurry

b1 Simulation of cement slurry curing under constant pressure conditions in the wellbore

After the mud cake is formed, the core 7 and the casing 6 are embedded on the lower end cover 11, and cement slurry with different properties is configured according to the experimental requirements, and the cement slurry is slowly injected into the annular space between the casing 6 and the core 7 to fill it up. Finally use the upper end cover 4 to compress and seal. Put the assembled simulated shaft into the kettle body 9 to ensure a good seal between the lower end cover 11 and the kettle body 9, and then tighten the kettle cover 3 tightly. Screw the displacement measuring device 1 into the communication port 18 on the top of the kettle cover 3, and connect to the system data acquisition software. Open stop valve 3 23 and stop valve 5 26. After the water inflow to the kettle body 9 is completed, set the temperature value of the kettle body 9 according to the demand, usually 75-150°C, and set the casing 6, cement annulus and confining pressure (the upper limit of the casing pressure is 40MPa, the upper limit of the cement sheath and confining pressure is 30MPa), turn on the liquid booster pump 46 and the gas booster pump 30, and turn on the thermocouple to work, so as to realize the simulated wellbore etc. Cement slurry curing under pressure conditions.

b2 Cement slurry curing under simulated casing pressure holding condition

The difference between this method and the above-mentioned cement slurry curing process under equal pressure conditions in the wellbore is that the initial casing internal pressure value is set higher than the pressure value of the cement annulus outside the casing and the pressure value of the confining pressure. Confining pressure 20MPa, other steps are the same as the above method.

c Cement sheath seal integrity test under different working conditions

c1 Test the integrity of the cement sheath seal by adjusting the pressure difference between the top and bottom of the cement sheath

Gas or water can be selected as the medium to test the integrity of the cement sheath seal. Take gas channeling as an example to illustrate:

After the cement slurry is cured, close the stop valve three 23, open the stop valve two 21, and select the gas channeling mode. Close the stop valve five 26. Open shut-off valve nine 44, this moment, the cement sheath back pressure at the inspection end will rise to be identical with the cement sheath pressure, then close shut-off valve nine 44. Open the stop valve 11 37, adjust the back pressure valve 1 40, and after reducing the pressure at the bottom of the cement sheath and forming a pressure difference at the top of the cement sheath, close the stop valve 11 37. The water tank 38 for channeling inspection is filled with water, the stop valve ten 37 and the stop valve six 35 are opened, and the cement sheath seal integrity under the current working condition is tested. Different pressure difference intervals can be selected during the test, such as 2MPa, that is, a channeling test will be performed every time the back pressure of the cement sheath decreases by 2MPa.

c2 Test the integrity of the cement sheath seal by adjusting the pressure inside the casing

If the failure of the cement sheath seal integrity does not occur in the above-mentioned whole test, the cement sheath seal integrity test under the condition of alternating casing internal pressure can be continued.

Open stop valve 9 44, open stop valve 11 41, adjust back pressure valve 1 40, after making the top and bottom of the cement ring form a fixed pressure difference and stabilize, close the stop valve 11 41. Adjust the back pressure valve 2 45 to unload the inner pressure of the casing at regular intervals until the inner pressure of the casing 6 is zero. During this period, the internal pressure of the casing 6 is unloaded once, and a channeling test is performed. If channeling does not occur, continue to adjust the back pressure valve 2 45 to adjust the internal pressure of the casing 6 to the original pressure, and then add pressure to the casing at regular intervals. For example, add 5MPa each time, and repeat the above-mentioned casing pressure unloading process after each casing pressurization and conduct a channeling test until the seal integrity of the cement sheath fails.

During the test, the channeling test will be carried out under the condition that the internal pressure of the casing is greater than the external pressure and compared with the original test results to determine whether the seal failure problem occurs at the first cementing interface or the second interface. In addition, the monitoring results of the displacement measuring device are used to judge the size of the cementing-interface micro-annulus.

2. Gas channeling experiments in micro-annulus with different sizes

In the method b2, after simulating the cement slurry curing under the condition of casing holding pressure, the stop valve three 23 is closed, the stop valve two 21 is opened, and the air channeling mode is selected. Close the stop valve five 26. Open stop valve nine 44, after making the top and bottom of the cement sheath form a fixed size pressure difference and stabilize, close stop valve eleven 41. Adjust the back pressure valve 2 45 to unload the pressure inside the casing at fixed intervals until the internal pressure of the casing is zero. During this period, conduct a channeling test every time the internal pressure of the casing is unloaded. The size of the cementing-interface micro-annulus is judged by the monitoring results of the displacement measuring device.

3. Pressure bearing and sealing capacity test of cement slurry with different characteristics

According to the test needs, configure cement slurry systems with different properties for maintenance. After the maintenance is completed, close the stop valve three 23, open the stop valve two 21, and select the gas channeling mode. Close the stop valve five 26. Open shut-off valve nine 44, this moment, the cement sheath back pressure at the inspection end will rise to be identical with the cement sheath pressure, then close shut-off valve nine 44. Open the stop valve 11 41, adjust the back pressure valve 1 45, and after reducing the channeling pressure at the bottom of the cement sheath and forming a pressure difference at the top of the cement sheath, close the stop valve 11 41. The water tank 38 for channeling inspection is filled with water, the stop valve ten 37 and the stop valve six 35 are opened for testing, and the pressure difference at the top and bottom of the cement sheath is gradually increased in the test. If the back pressure at the bottom of the cement sheath increases during the test, the current pressure difference is regarded as the ultimate sealing pressure of the cement slurry.

4. Analysis of the influence of different factors on the integrity of the cement sheath seal

a Mud cake properties: different mud cake thickness can be obtained by changing the gas source pressure and time; different mud cake properties can be obtained by changing the core lithology and drilling fluid formula;

b Cement sheath thickness: comparative experiments were carried out by selecting casings of different sizes and upper and lower end caps of different internal structure sizes.

c Curing temperature and pressure: through the temperature control instrument and pressure control instrument to program temperature and pressure control, respectively, to set the temperature and pressure changes in the cement slurry curing process.

Claims (9)

1. a kind of Oil/gas Well cement sheath sealing integrity test device, it is characterised in that：Including autoclave pressure and in autoclave pressure The simulation wellbore hole in portion, described test device also includes control pressurer system, temperature control system, channelling detecting system, strain Measuring system and mud cake simulation system；

Described simulation wellbore hole includes sleeve pipe (6) and the rock core (7) positioned at sleeve pipe (6) periphery, described sleeve pipe (6) and rock core (7) annular gap is formed between, cement sheath (8) is formed in described annular gap；Described sleeve pipe (6) and rock core (7) it is upper and lower It is respectively arranged at two ends with upper end cover (4) and bottom end cover (11)；

Described autoclave pressure includes kettle (9) and the kettle cover (3) being engaged with kettle (9)；Described kettle (9) is provided with and cement Ring (8) top together with cement sheath pressure port (17) and testing of connecting with cement sheath (8) bottom alter mouth (10)；Described kettle (9) confined pressure mouthful (5) connected with rock core (7) periphery upper end and the pressure relief opening (14) connected with rock core (7) periphery lower end are provided with；Institute The kettle (9) stated is provided with the thermocouple port (15) for installing heating galvanic couple；Described kettle (9) is provided with internal with sleeve pipe (6) The casing pressure for being arranged on kettle (9) lower end mouthful (12) of connection；Described kettle cover (3) is provided with for connecting displacement measuring device (1) or drill-in fluid storage barrel (54) connected entrance (18)；

Described control pressurer system includes the pipe that the pipeline one being connected with confined pressure mouthful (5) is connected with cement sheath pressure port (17) Pipeline four that road two and casing pressure mouthful (12) are connected and the pipeline five being connected with pressure relief opening (14)；

Stop valve one (27), pressure sensor one (28), pressure regulator valve one (29), gas boosting pump are connected with described pipeline one (30), Stress control instrument (32) and source nitrogen (34), described gas boosting pump (30) are connected with compressed air source (33)；

Stop valve two (21), stop valve four (22), pressure sensor two (24), pressure regulator valve two are connected with described pipeline two And stop valve seven (31) (25)；

Pressure sensor four (43), liquid booster pump (46) and water source (47), described liquid are connected with described pipeline four Booster pump (46) is connected with compressed air source (33)；

Stop valve eight (48) and drainpipe (42) are connected with described pipeline five；

Described temperature control system includes that what is be connected with thermocouple port (15) is arranged on the thermocouple of kettle (9) inside, described Thermocouple be also connected with temperature control instrument (49), described kettle (9) outside is wound with cooling tube (16), described cooling Pipe (16) is connected with water source (47)；

Described channelling detecting system includes altering the pipeline three that mouth (10) is connected with testing, and stop valve is connected with described pipeline three Six (35), pressure sensor three (36), stop valve ten (37) and channelling monitoring device；

Described strain measurement system is goed deep into inside sleeve pipe (6) for measuring sleeve pipe (6) by the connected entrance (18) on kettle cover (3) The displacement measuring device (1) of inwall radial displacement；

Described mud cake simulation system includes drilling fluid storage barrel (54) and rock core filter screen (20), the drilling fluid storage barrel (54) Upper and lower ends be respectively equipped with stop valve ten two (55) and stop valve ten three (53), the upper end of the drilling fluid storage barrel (54) leads to Cross wireway to be connected with nitrogen cylinder (56), the drilling fluid storage barrel (54) is connected with kettle cover (3)；Described rock core filter screen (20) It is nested in the outer wall of rock core (7).

2. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：The pipeline one With branch line six is connected with pipeline two, stop valve five (26), described branched pipe are connected with described branch line six The tie point of Lu Liuyu pipelines two be located between cement sheath pressure port (17) and stop valve two (21), the branch line six with manage The tie point on road one is located between confined pressure mouthful (5) and stop valve one (27).

3. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：The pipeline two With branch line seven is connected with branch line six, be provided with described branch line seven stop valve three (23) and dehydration bucket (50), described branch line seven and the tie point of pipeline two are located between stop valve two (21) and pressure regulator valve two (25), described Branch line seven and branch line six tie point be located between cement sheath pressure port (17) and stop valve two (21).

4. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：Described pipeline Branch line eight is connected with three, counterbalance valve one (40) and stop valve ten one (41), institute are provided with described branch line eight The end for stating branch line eight is connected with drainpipe (42).

5. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：Described pipeline Branch line nine is connected with five, counterbalance valve two (45), the branch line nine and pipe are provided with described branch line nine The tie point on road five is located between liquid booster pump (46) and pressure sensor four (43), end and the row of the branch line nine Water pipe (42) is connected.

6. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：Described pipeline Branch line ten is connected with five, stop valve nine (44), the branch line ten and pipe are provided with described branch line ten The tie point on road five is located between pressure sensor four (43) and casing pressure mouthful (12), end and the row of the branch line ten Water pipe (42) is connected.

7. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：The kettle (9) inner bottom surface is provided with positioning boss (19).

8. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：The cement sheath (8) lower end is provided with filter screen (51).

9. Oil/gas Well cement sheath sealing integrity test device according to claim 1, it is characterised in that：The kettle (9) and kettle cover (3) between, between the connected entrance (18) and displacement measuring device (1) of kettle cover and kettle cover connected entrance (18) with bore Connecting elements (2) is provided between feed liquor storage barrel (54).