Experimental device and method for simulating fracture-vug type stratum overflow and leakage co-storage well killing process

Abstract

The invention belongs to the technical field of oil and gas well drilling, and particularly relates to an experimental device and method for simulating the overflow and leakage co-storage well killing process of a fractured-vuggy stratum. The device comprises a simulation wellbore system, a simulation drilling fluid circulation system, a simulation fracture-vug type stratum structure system, a simulation gas injection system, a data acquisition system and a data processing system. The wellbore simulation system is used for simulating a drill stem and a wellbore in an experiment; the simulated drilling fluid circulating system is connected with the upper part of the shaft system and is used for simulating injection and return of drilling fluid; the simulated fracture-vug type stratum structure system is connected with the lower part of the shaft system and is used for simulating cracks and karst caves in an experiment; the simulated gas injection system is used for injecting gas into the fracture-cavity type stratum structure system; and the data acquisition system and the data processing system are used for acquiring and processing experimental data in the experimental device. The experimental device and method provided by the invention aim at solving the problem that in the prior art, the overflow and leakage coexistence well killing process of a fracture-vug type stratum cannot be comprehensively simulated.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas well drilling, and in particular relates to an experimental device and a method for simulating a well-killing process of leakage co-existence in fracture-cavity formations. Background Art

[0002] my country's deep fracture-cavity carbonate oil and gas resources are abundant and have huge oil and gas resource potential. They have become an important target for China's oil and gas exploration and development and oil and gas reserve and production increase. Compared with permeable reservoirs, fracture-cavity carbonate reservoirs have good connectivity, strong pressure sensitivity, and a narrow drilling fluid density window. During the drilling process, they are prone to complex conditions such as overflow, leakage, and even coexistence of overflow and leakage. The well control risk is high, which will cause immeasurable losses to personnel safety, reservoirs, and production efficiency during the drilling operation. The current well pressure technology theory used to solve the coexistence of overflow and leakage in fracture-cavity formations is basically the actual field experience obtained by summarizing temporary technical measures after overflow and leakage occur in specific fracture-cavity reservoir blocks. It has great limitations when used in other blocks.

[0003] During the well killing process with leakage, the fluid flow state between the fracture-cavity and the wellbore affects each other. However, there are few experimental methods for well killing technology when leakage occurs in fracture-cavity formations in China. Most experimental equipment studies the flow pressure in the wellbore or the evolution characteristics of the displacement interface in the fracture when gravity displacement occurs. The following is the technical background information related to the present invention:

[0004] The patent "A Wellbore Fracture Simulation Device" (CN102305045A) simulates the drilling loss process by connecting a fracture pipe to the simulated wellbore, without considering the specific conditions in the formation;

[0005] The patent "An experimental device and method for simulating gas invasion into a wellbore of a fracture-cavity reservoir" (CN114737962A) uses several pipes to connect a simulated wellbore and a simulated formation to evaluate the gas flow characteristics during gas invasion of fracture-cavity formations, but it cannot simulate the complex flow in the wellbore during formation pressure control and well pressure suppression with leakage.

[0006] The patent "An experimental method for simulating well killing during overflow" (CN104835405A) uses the invented device to simulate the complex flow during the drilling process, and simulates the three well killing processes of the driller method, engineer method or reverse circulation method under overflow conditions. However, it cannot simulate the complex well killing conditions of overflow coexisting underground, and does not involve data collection and processing.

[0007] Therefore, the current research lacks consideration of the well-killing process after the occurrence of leakage and the control of formation pressure. At the same time, the indoor experimental equipment and methods lack relatively comprehensive consideration of the wellbore and fracture-cavity formation characteristics for the well-killing process after the leakage. Therefore, an experimental device and method for simulating the well-killing process of leakage in fracture-cavity formations is established to study the pressure change characteristics of the wellbore and formation during the well-killing process of leakage in fracture-cavity formations, which is of great significance for the drilling and completion research of fracture-cavity formation oil and gas reservoirs. Summary of the invention

[0008] In order to solve the above-mentioned problem in the prior art, that is, the problem that the prior art cannot fully simulate the process of leakage and well killing in fracture-cavity formations, the present invention provides an experimental device and method for simulating the process of leakage and well killing in fracture-cavity formations;

[0009] In a first aspect of the present invention, an experimental device for simulating the process of well killing in fracture-cavity formation with leakage and coexistence is proposed, comprising: a simulated wellbore system, a simulated drilling fluid circulation system, a simulated fracture-cavity formation structure system, a simulated gas injection system, a data acquisition system and a data processing system;

[0010] The simulated wellbore system includes a simulated wellbore and a simulated drill string;

[0011] The simulated drilling fluid circulation system includes a liquid storage tank, a stirring motor, a drilling fluid centrifugal pump, a liquid injection control valve, a stirring motor, a gas-liquid separation tank and an overflow valve;

[0012] The simulated fracture-cavity type stratum structure system includes a simulated fracture subsystem and a simulated cave subsystem; the simulated fracture subsystem includes a first simulated fracture, a second simulated fracture, a first pneumatic ball valve, and a second pneumatic ball valve; the simulated cave subsystem includes a simulated cave;

[0013] The simulated gas injection system includes an air compressor, a gas storage tank, a gas injection control valve, a constant pressure check valve and a drilling fluid recovery tank;

[0014] The data acquisition system includes: a drilling fluid flow meter, a return flow meter, a vertical pressure sensor, a casing pressure sensor, a bottom hole pressure sensor, a first simulated fracture pressure sensor, a second simulated fracture pressure sensor, a simulated cave pressure sensor, a gas flow meter, a gas tank pressure sensor and a high-speed camera;

[0015] The data processing system includes a data processor;

[0016] The simulated gas injection system is connected in sequence to the simulated fracture-cavity formation structure system, the simulated wellbore system, and the simulated drilling fluid circulation system; the data acquisition system respectively collects parameters of the simulated wellbore system, parameters of the simulated drilling fluid circulation system, parameters of the simulated fracture-cavity formation structure system, and parameters of the simulated gas injection system and uploads them to the data processing system.

[0017] In some preferred embodiments, the simulated gas injection system specifically comprises:

[0018] The output end of the air compressor is connected to the input end of the air storage tank through a gas phase flow pipeline;

[0019] The output end of the gas storage tank is connected to the input end of the upper part of the simulated cave through a gas phase flow pipeline via a gas injection control valve; wherein a gas flow meter is arranged on the gas phase flow pipeline between the input end of the simulated cave and the gas injection control valve, and a gas storage tank pressure sensor is arranged in the gas storage tank;

[0020] The lower part of the simulated cave is connected to the drilling fluid recovery tank through a constant pressure one-way valve via a gas phase flow pipeline.

[0021] In some preferred embodiments, the simulated fracture-cavity type stratum structure system specifically comprises:

[0022] The upper part of the simulated cave is connected to the simulated wellbore through the first simulated fracture and the first pneumatic ball valve; a first simulated fracture pressure sensor is arranged between the simulated wellbore and the first pneumatic ball valve;

[0023] The lower part of the simulated cave is connected to the simulated wellbore through the second simulated fracture and the second pneumatic ball valve; a second simulated fracture pressure sensor is arranged between the simulated wellbore and the second pneumatic ball valve.

[0024] In some preferred embodiments, the simulated wellbore system specifically comprises:

[0025] The simulated wellbore is placed vertically, and the simulated drill string is placed vertically in the exact center of the simulated wellbore, with the upper end of the simulated drill string being higher than the simulated wellbore;

[0026] The upper end of the simulated wellbore is connected to the gas-liquid separation tank through the first flow pipeline and the return flowmeter, and an overflow valve is arranged between the return flowmeter and the simulated wellbore; the lower part of the simulated wellbore is connected to the first simulated crack and the second simulated crack respectively, and the connection positions of the first simulated crack and the second simulated crack and the simulated wellbore have a set height difference;

[0027] A casing pressure sensor is connected to the upper part of the simulated wellbore, a bottom hole pressure sensor is set at the bottom of the simulated wellbore, and a vertical pressure sensor is connected to the top of the simulated drill string.

[0028] In some preferred embodiments, the simulated drilling fluid circulation system specifically comprises:

[0029] The upper end of the simulated wellbore passes through a return flow meter and is connected to the first end of the gas-liquid separation tank through a gas-liquid two-phase pipeline;

[0030] The second end of the gas-liquid separation tank extends above the liquid storage tank through a gas-liquid two-phase pipeline;

[0031] A stirring motor is arranged in the liquid storage tank; the liquid storage tank is connected to the drilling fluid centrifugal pump through a pipeline;

[0032] The drilling fluid centrifugal pump is connected to the top of the simulated drill string through a pipeline via a liquid injection control valve; a drilling fluid flow meter is arranged between the liquid injection control valve and the simulated drill string.

[0033] In some preferred embodiments, the wellbore, simulated fractures and simulated caves are made of transparent organic glass with a maximum pressure bearing capacity of 1 MPa.

[0034] Another aspect of the present invention is based on the above-mentioned experimental device for simulating the process of well killing with leakage in fracture-cavity formation, and proposes an experimental method for simulating the process of well killing with leakage in fracture-cavity formation, comprising:

[0035] Step S100, connecting a device for simulating the process of leaking and well killing in fracture-cavity formations, closing the liquid injection control valve, the overflow valve, the first pneumatic ball valve, the second pneumatic ball valve, the gas injection control valve and the constant pressure check valve, and confirming the sealing of the device;

[0036] Step S200, after adding clean water and a weighting agent into the liquid storage tank, the clean water and the weighting agent are mixed evenly by a stirring motor to obtain a simulated drilling fluid, and the density of the first simulated drilling fluid is measured;

[0037] Step S300, using an air compressor to make the air tank reach a set air tank pressure;

[0038] Step S400, opening the gas injection control valve to allow the gas storage tank to inject compressed air into the simulated cave;

[0039] Step S500, opening the injection control valve and the overflow valve, and pumping the simulated drilling fluid in the reservoir into the simulated drill string through the drilling fluid centrifugal pump;

[0040] The simulated drilling fluid in the simulated drill string is returned to the gas-liquid separation tank through the simulated wellbore and the overflow valve;

[0041] The gas-liquid separation tank separates the used simulated drilling fluid into gas and liquid, and injects the separated simulated drilling fluid into the liquid storage tank;

[0042] Step S600, collecting sensor data through a drilling fluid flow meter, a return flow meter, a vertical pressure sensor, a casing pressure sensor, a bottom hole pressure sensor, a first simulated fracture pressure sensor, a second simulated fracture pressure sensor, a simulated cave pressure sensor, a gas flow meter, a gas tank pressure sensor and a high-speed camera, and transmitting the sensor data to a data processor;

[0043] Step S700, when the fluctuation range of the data of the first simulated fracture pressure sensor and the second simulated fracture pressure sensor is less than a preset first stable threshold, based on the pressure difference between the bottom hole pressure of the simulated wellbore and the simulated cave, the first pneumatic ball valve and the second pneumatic ball valve are adjusted to control the coexistence of leakage at the lower part of the simulated fracture cave and overflow at the upper part of the fracture cave;

[0044] Obtain real-time simulated standpipe pressure through the standpipe pressure sensor;

[0045] Obtain real-time simulated wellhead pressure through casing pressure sensor;

[0046] Step S800, when the instantaneous pressure of the simulated wellhead pressure reaches the set judgment value, read the second sensor data of the standpipe pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the simulated cave pressure sensor 20 and the high-speed camera 28, and record the first simulated standpipe pressure, the first simulated wellhead pressure, the first simulated cave pressure and the first gas-liquid two-phase distribution;

[0047] Step S900, closing the drilling fluid centrifugal pump 2 and the overflow valve 30, when the real-time simulated wellhead pressure fluctuates within a preset time period and the range is less than the preset second stable threshold, the simulated riser pressure at this time is recorded as the stable riser pressure, the simulated wellhead pressure at this time is recorded as the stable wellhead pressure, the second simulated drilling fluid density required for drilling is calculated, and the simulated drilling fluid in the reservoir 1 is adjusted to the second simulated drilling fluid density;

[0048] The second simulated drilling fluid density ρ k , which is calculated as:

[0049]

[0050] P p represents the stable standpipe pressure, h l represents the simulated wellbore height, ρ l represents the simulated drilling fluid density in the previous round of experiments; when n = 1, ρ l Represents the first simulated drilling fluid density.

[0051] Step S1000, turning on the drilling fluid centrifugal pump to a set displacement, adjusting the relief valve to a set opening, making the real-time simulated wellhead pressure reach the stable wellhead pressure, simulating the current well killing method process, reading the third sensor data of the standpipe pressure sensor, the casing pressure sensor, the bottom hole pressure sensor, the simulated cave pressure sensor and the high-speed camera, and recording the second simulated standpipe pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution;

[0052] Step S1100, based on the first simulated riser pressure, the first simulated wellhead pressure, the first simulated cave pressure, the first gas-liquid two-phase distribution, the second simulated riser pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution, calculate the simulated wellhead pressure change, the simulated cave pressure change and the gas-liquid flow law, complete the nth round of simulated fracture-cavity formation condition experiment to obtain the nth round of experimental results;

[0053] Step S1200, select one or more of the new simulated drilling fluid density, set displacement, and well killing method, set n=n+1, and return to step S700.

[0054] In some preferred embodiments, after the air injection control valve is opened to allow the gas storage tank to inject compressed air into the simulated cave, the pressure difference between the simulated wellbore and the simulated cave is set, the constant pressure relief valve is opened, the pressure in the simulated cave is maintained at a preset simulated cave pressure, and a simulated well killing process with leakage and overflow occurring under constant formation pressure conditions in fracture-cavity formations is carried out;

[0055] In some preferred embodiments, after the gas injection control valve is opened to allow the gas storage tank to inject compressed air into the simulated cave, the simulated cave pressure is set. When the pressure in the simulated cave reaches the preset simulated cave pressure, the gas injection control valve and the constant pressure relief valve are closed to carry out a simulated well pressure process in which leakage coexists under a constant fracture-cavity volume in the fracture-cavity formation.

[0056] Beneficial effects of the present invention:

[0057] (1) The fracture-cavity formation structure system of the present invention includes two simulated fractures with a set height difference, which can simulate the underground working conditions of overflow and leakage coexisting;

[0058] (2) The method of the present invention controls the drilling fluid circulation system and the gas injection system, and can simulate the coexistence of spills and the complex flow in the wellbore during the well killing process by adjusting various valve devices, thereby realizing an experimental environment under constant formation volume and constant pressure conditions;

[0059] (3) The experimental device of the present invention can realize the collection and processing of gas and liquid flow data in each system by installing various sensors, flow meters and high-speed cameras in the system and combining with the data processing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0061] Figure 1 Schematic diagram of the structure of an experimental device for simulating the process of well killing with leakage in fracture-cavity formation in an embodiment. DETAILED DESCRIPTION

[0062] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0063] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0064] An experimental device for simulating the process of well killing with leakage and coexistence in fracture-cavity formations according to the first embodiment of the present invention is shown in the schematic diagram of the structure. Figure 1 As shown, it includes a simulated wellbore system, a simulated drilling fluid circulation system, a simulated fracture-cavity formation structure system, a simulated gas injection system, a data acquisition system and a data processing system;

[0065] The simulated wellbore system includes a simulated wellbore 11 and a simulated drill string 7;

[0066] The simulated drilling fluid circulation system comprises a liquid storage tank 1, a stirring motor 5, a drilling fluid centrifugal pump 2, a liquid injection control valve 3, a stirring motor 5, a gas-liquid separation tank 6 and a relief valve 30;

[0067] The simulated fracture-cavity type stratum structure system includes a simulated fracture subsystem and a simulated cave subsystem; the simulated fracture subsystem includes a first simulated fracture 15, a second simulated fracture 18, a first pneumatic ball valve 14, and a second pneumatic ball valve 17; the simulated cave subsystem includes a simulated cave 19;

[0068] The simulated gas injection system includes an air compressor 25, a gas storage tank 24, a gas injection control valve 22, a constant pressure check valve 26 and a drilling fluid recovery tank 27;

[0069] The data acquisition system includes: a drilling fluid flow meter 4, a return flow meter 8, a vertical pressure sensor 9, a casing pressure sensor 10, a bottom hole pressure sensor 12, a first simulated fracture pressure sensor 13, a second simulated fracture pressure sensor 16, a simulated cave pressure sensor 20, a gas flow meter 21, a gas tank pressure sensor 23 and a high-speed camera 28;

[0070] The data processing system includes a data processor 28;

[0071] The simulated gas injection system is connected in sequence to the simulated fracture-cavity formation structure system, the simulated wellbore system, and the simulated drilling fluid circulation system; the data acquisition system respectively collects parameters of the simulated wellbore system, parameters of the simulated drilling fluid circulation system, parameters of the simulated fracture-cavity formation structure system, and parameters of the simulated gas injection system and uploads them to the data processing system.

[0072] In this embodiment, the simulated gas injection system specifically includes:

[0073] The output end of the air compressor 25 is connected to the input end of the air storage tank 24 through a gas phase flow pipeline;

[0074] The output end of the gas storage tank 24 is connected to the input end of the upper part of the simulated cave 19 through the gas injection control valve 22 through the gas phase flow pipeline; wherein a gas flow meter 21 is arranged in the gas phase flow pipeline between the input end of the simulated cave 19 and the gas injection control valve 22, and a gas storage tank pressure sensor 23 is arranged in the gas storage tank 24;

[0075] The lower part of the simulated cave 19 is connected to the drilling fluid recovery tank 27 through a constant pressure one-way valve 26 via a gas phase flow pipeline.

[0076] In this embodiment, the simulated fracture-cavity type stratum structure system specifically includes:

[0077] The upper part of the simulated cave 19 is connected to the simulated wellbore 11 through the first simulated fracture 15 and the first pneumatic ball valve 14; a first simulated fracture pressure sensor 13 is arranged between the simulated wellbore and the first pneumatic ball valve 14;

[0078] The lower part of the simulated cave 19 is connected to the simulated wellbore 11 through the second simulated fracture 18 and the second pneumatic ball valve 17 ; a second simulated fracture pressure sensor 16 is arranged between the simulated wellbore and the second pneumatic ball valve 17 .

[0079] In this embodiment, the simulated wellbore system specifically includes:

[0080] The simulated wellbore 11 is placed vertically, and the simulated drill string 7 is placed vertically in the center of the simulated wellbore 11, and the upper end of the simulated drill string 7 is higher than the simulated wellbore 11;

[0081] The upper end of the simulated wellbore 11 is connected to the gas-liquid separation tank 6 through the first flow pipeline and the return flowmeter 8, and an overflow valve 30 is arranged between the return flowmeter 8 and the simulated wellbore 11; the lower part of the simulated wellbore 11 is connected to the first simulated crack 15 and the second simulated crack 18 respectively, and the connection positions of the first simulated crack 15 and the second simulated crack 18 and the simulated wellbore 11 have a set height difference;

[0082] The upper part of the simulated wellbore 11 is connected to a casing pressure sensor 10 , the bottom of the simulated wellbore 11 is provided with a bottom hole pressure sensor 12 , and the top of the simulated drill string 7 is connected to a vertical pressure sensor 9 .

[0083] In this embodiment, the simulated drilling fluid circulation system specifically includes:

[0084] The upper end of the simulated wellbore 11 passes through the return flow meter 8 and is connected to the first end of the gas-liquid separation tank 6 through a gas-liquid two-phase pipeline;

[0085] The second end of the gas-liquid separation tank 6 extends above the liquid storage tank 1 through a gas-liquid two-phase pipeline;

[0086] A stirring motor 5 is provided in the liquid storage tank 1; the liquid storage tank 1 is connected to the drilling fluid centrifugal pump 2 through a pipeline;

[0087] The drilling fluid centrifugal pump 2 is connected to the top of the simulated drill string 7 through a pipeline via a liquid injection control valve 3 ; a drilling fluid flow meter 4 is provided between the liquid injection control valve 3 and the simulated drill string 7 .

[0088] In this embodiment, the wellbore 11, simulated fractures 15, simulated fractures 18 and simulated caves 19 are made of transparent organic glass with a maximum pressure bearing capacity of 1 MPa.

[0089] An experimental method for simulating a well-killing process with leakage coexisting in a fracture-cavity formation according to a second embodiment of the present invention uses an experimental device for simulating a well-killing process with leakage coexisting in a fracture-cavity formation according to the first embodiment to carry out a simulated well-killing process with leakage coexisting in a fracture-cavity formation under constant formation pressure conditions, including steps S100 to S1200, each of which is described in detail as follows:

[0090] Step S100, connect the device for simulating the process of leakage and well killing in fracture-cavity formation, close the injection control valve 3, the relief valve 30, the first pneumatic ball valve 14, the second pneumatic ball valve 17, the gas injection control valve 22 and the constant pressure check valve 26, and confirm the sealing of the device;

[0091] Step S200, after adding clean water and a weighting agent into the liquid storage tank 1, the clean water and the weighting agent are mixed evenly by the stirring motor 5 to obtain a simulated drilling fluid, and the density of the first simulated drilling fluid is measured;

[0092] Step S300, using the air compressor 25 to make the air storage tank 24 reach a set air storage tank pressure;

[0093] Step S400, opening the air injection control valve 22, allowing the air storage tank 24 to inject compressed air into the simulated cave 19, setting the pressure difference between the simulated wellbore 11 and the simulated cave 19, opening the constant pressure relief valve 26, and maintaining the pressure in the simulated cave 19 at a preset simulated cave pressure;

[0094] Step S500, opening the injection control valve 3 and the overflow valve 30, and pumping the simulated drilling fluid in the reservoir 1 into the simulated drill string 7 through the drilling fluid centrifugal pump 2;

[0095] The simulated drilling fluid in the simulated drill string 7 is returned to the gas-liquid separation tank 6 through the simulated wellbore 11 and the overflow valve 30;

[0096] The gas-liquid separation tank 6 separates the used simulated drilling fluid into gas and liquid, and injects the separated simulated drilling fluid into the liquid storage tank;

[0097] Step S600, collecting sensor data through the drilling fluid flowmeter 4, the return flowmeter 8, the vertical pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the first simulated fracture pressure sensor 13, the second simulated fracture pressure sensor 16, the simulated cave pressure sensor 20, the gas flowmeter 21, the gas tank pressure sensor 23 and the high-speed camera 28, and transmitting the sensor data to the data processor 28;

[0098] Step S700, when the data fluctuation range of the first simulated fracture pressure sensor 13 and the second simulated fracture pressure sensor 16 is less than the preset first stable threshold, based on the pressure difference between the bottom hole pressure of the simulated wellbore 11 and the simulated cave 19, the first pneumatic ball valve 14 and the second pneumatic ball valve 17 are adjusted to control the coexistence of leakage at the lower part of the simulated fracture cave and overflow at the upper part of the fracture cave;

[0099] Acquire real-time simulated standpipe pressure through standpipe pressure sensor 9;

[0100] Acquire real-time simulated wellhead pressure through casing pressure sensor 10;

[0101] Step S800, when the instantaneous pressure of the simulated wellhead pressure reaches the set judgment value, read the second sensor data of the vertical pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the simulated cave pressure sensor 20 and the high-speed camera 28, and record the first simulated wellhead pressure, the first simulated wellhead pressure, the first simulated cave pressure and the first gas-liquid two-phase distribution;

[0102] Step S900, closing the drilling fluid centrifugal pump 2 and the overflow valve 30, when the real-time simulated wellhead pressure fluctuates within a preset time period and the range is less than the preset second stable threshold, the simulated riser pressure at this time is recorded as the stable riser pressure, the simulated wellhead pressure at this time is recorded as the stable wellhead pressure, the second simulated drilling fluid density required for drilling is calculated, and the simulated drilling fluid in the reservoir 1 is adjusted to the second simulated drilling fluid density;

[0103] The second simulated drilling fluid density ρ k ,kg / cm 3 , which is calculated as:

[0104]

[0105] P p represents the stable standpipe pressure, h l represents the simulated wellbore height, ρ l represents the simulated drilling fluid density in the previous round of experiments; when n = 1, ρ l Represents the first simulated drilling fluid density.

[0106] Step S1000, open the drilling fluid centrifugal pump 2 to the set displacement, adjust the relief valve 30 to the set opening, make the real-time simulated wellhead pressure reach the stable wellhead pressure, simulate the current well killing method process, read the third sensor data of the standpipe pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the simulated cave pressure sensor 20 and the high-speed camera 28, and record the second simulated standpipe pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution;

[0107] Step S1100, based on the first simulated riser pressure, the first simulated wellhead pressure, the first simulated cave pressure, the first gas-liquid two-phase distribution, the second simulated riser pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution, calculate the simulated wellhead pressure change, the simulated cave pressure change and the gas-liquid flow law, complete the nth round of simulated fracture-cavity formation condition experiment to obtain the nth round of experimental results;

[0108] Step S1200, select one or more of the new simulated drilling fluid density, set displacement, and well killing method, set n=n+1, and return to step S700.

[0109] An experimental method for simulating the well-killing process of leaking and coexisting in a fracture-cavity formation according to a third embodiment of the present invention uses an experimental device for simulating the well-killing process of leaking and coexisting in a fracture-cavity formation according to the first embodiment to carry out a simulated well-killing process of leaking and coexisting in a fracture-cavity formation under the condition of a constant fracture-cavity volume, including steps S100 to S1200, each of which is described in detail as follows:

[0110] Step S100, connect the device for simulating the process of leakage and well killing in fracture-cavity formation, close the injection control valve 3, the relief valve 30, the first pneumatic ball valve 14, the second pneumatic ball valve 17, the gas injection control valve 22 and the constant pressure check valve 26, and confirm the sealing of the device;

[0111] Step S200, after adding clean water and a weighting agent into the liquid storage tank 1, the clean water and the weighting agent are mixed evenly by the stirring motor 5 to obtain a simulated drilling fluid, and the density of the first simulated drilling fluid is measured;

[0112] Step S300, using the air compressor 25 to make the air storage tank 24 reach a set air storage tank pressure;

[0113] Step S400, opening the gas injection control valve 22, allowing the gas storage tank 24 to inject compressed air into the simulated cave 19; setting the simulated cave pressure, when the pressure in the simulated cave 19 reaches the preset simulated cave pressure, closing the gas injection control valve 22 and the constant pressure relief valve 26;

[0114] Step S500, opening the injection control valve 3 and the overflow valve 30, and pumping the simulated drilling fluid in the reservoir 1 into the simulated drill string 7 through the drilling fluid centrifugal pump 2;

[0115] The simulated drilling fluid in the simulated drill string 7 is returned to the gas-liquid separation tank 6 through the simulated wellbore 11 and the overflow valve 30;

[0116] The gas-liquid separation tank 6 separates the used simulated drilling fluid into gas and liquid, and injects the separated simulated drilling fluid into the liquid storage tank;

[0117] Step S600, collecting sensor data through the drilling fluid flowmeter 4, the return flowmeter 8, the vertical pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the first simulated fracture pressure sensor 13, the second simulated fracture pressure sensor 16, the simulated cave pressure sensor 20, the gas flowmeter 21, the gas tank pressure sensor 23 and the high-speed camera 28, and transmitting the sensor data to the data processor 28;

[0118] Step S700, when the data fluctuation range of the first simulated fracture pressure sensor 13 and the second simulated fracture pressure sensor 16 is less than the preset first stable threshold, based on the pressure difference between the bottom hole pressure of the simulated wellbore 11 and the simulated cave 19, the first pneumatic ball valve 14 and the second pneumatic ball valve 17 are adjusted to control the coexistence of leakage at the lower part of the simulated fracture cave and overflow at the upper part of the fracture cave;

[0119] Acquire real-time simulated standpipe pressure through standpipe pressure sensor 9;

[0120] Acquire real-time simulated wellhead pressure through casing pressure sensor 10;

[0121] Step S800, when the instantaneous pressure of the simulated wellhead pressure reaches the set judgment value, read the second sensor data of the vertical pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the simulated cave pressure sensor 20 and the high-speed camera 28, and record the first simulated wellhead pressure, the first simulated wellhead pressure, the first simulated cave pressure and the first gas-liquid two-phase distribution;

[0122] Step S900, closing the drilling fluid centrifugal pump 2 and the overflow valve 30, when the real-time simulated wellhead pressure fluctuates within a preset time period and the range is less than the preset second stable threshold, the simulated riser pressure at this time is recorded as the stable riser pressure, the simulated wellhead pressure at this time is recorded as the stable wellhead pressure, the second simulated drilling fluid density required for drilling is calculated, and the simulated drilling fluid in the reservoir 1 is adjusted to the second simulated drilling fluid density;

[0123] The second simulated drilling fluid density ρ k , which is calculated as:

[0124]

[0125] P p represents the stable standpipe pressure, h l represents the simulated wellbore height, ρ l represents the simulated drilling fluid density in the previous round of experiments; when n = 1, ρ l Represents the first simulated drilling fluid density.

[0126] Step S1000, open the drilling fluid centrifugal pump 2 to the set displacement, adjust the relief valve 30 to the set opening, make the real-time simulated wellhead pressure reach the stable wellhead pressure, simulate the current well killing method process, read the third sensor data of the standpipe pressure sensor 9, the casing pressure sensor 10, the bottom hole pressure sensor 12, the simulated cave pressure sensor 20 and the high-speed camera 28, and record the second simulated standpipe pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution;

[0127] Step S1100, based on the first simulated riser pressure, the first simulated wellhead pressure, the first simulated cave pressure, the first gas-liquid two-phase distribution, the second simulated riser pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution, calculate the simulated wellhead pressure change, the simulated cave pressure change and the gas-liquid flow law, complete the nth round of simulated fracture-cavity formation condition experiment to obtain the nth round of experimental results;

[0128] Step S1200, select one or more of the new simulated drilling fluid density, set displacement, and well killing method, set n=n+1, and return to step S700.

[0129] Although the various steps in the above embodiment are described in the above-mentioned order, those skilled in the art can understand that in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the scope of protection of the present invention.

[0130] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0131] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0132] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. An experimental device for simulating the well-killing process of leakage and co-existence in fracture-cavity formations, characterized in that: The device comprises: a simulated wellbore system, a simulated drilling fluid circulation system, a simulated fracture-cavity formation structure system, a simulated gas injection system, a data acquisition system and a data processing system; The simulated wellbore system comprises a simulated wellbore (11) and a simulated drill string (7); The simulated drilling fluid circulation system comprises a liquid storage tank (1), a stirring motor (5), a drilling fluid centrifugal pump (2), a liquid injection control valve (3), a stirring motor (5), a gas-liquid separation tank (6) and a relief valve (30); The simulated fracture-cavity type stratum structure system comprises a simulated fracture subsystem and a simulated cave subsystem; the simulated fracture subsystem comprises a first simulated fracture (15), a second simulated fracture (18), a first pneumatic ball valve (14), and a second pneumatic ball valve (17); the simulated cave subsystem comprises a simulated cave (19); The simulated gas injection system comprises an air compressor (25), a gas storage tank (24), a gas injection control valve (22), a constant pressure check valve (26) and a drilling fluid recovery tank (27); The data acquisition system comprises: a drilling fluid flow meter (4), a return flow meter (8), a vertical pressure sensor (9), a casing pressure sensor (10), a bottom hole pressure sensor (12), a first simulated fracture pressure sensor (13), a second simulated fracture pressure sensor (16), a simulated cave pressure sensor (20), a gas flow meter (21), a gas tank pressure sensor (23) and a high-speed camera (28); The data processing system comprises a data processor (29); The simulated gas injection system is connected in sequence to the simulated fracture-cavity formation structure system, the simulated wellbore system, and the simulated drilling fluid circulation system; the data acquisition system respectively collects parameters of the simulated wellbore system, parameters of the simulated drilling fluid circulation system, parameters of the simulated fracture-cavity formation structure system, and parameters of the simulated gas injection system and uploads them to the data processing system.

2. The experimental device for simulating the process of well killing with leakage in fracture-cavity formation according to claim 1, characterized in that: The simulated gas injection system specifically comprises: The output end of the air compressor (25) is connected to the input end of the air storage tank (24) through a gas phase flow pipeline; The output end of the gas storage tank (24) is connected to the input end of the upper part of the simulated cave (19) through a gas injection control valve (22) and a gas phase flow pipeline; wherein a gas flow meter (21) is arranged in the gas phase flow pipeline between the input end of the simulated cave (19) and the gas injection control valve (22), and a gas storage tank pressure sensor (23) is arranged in the gas storage tank (24); The lower part of the simulated cave (19) is connected to the drilling fluid recovery tank (27) through a constant pressure one-way valve (26) via a gas phase flow pipeline.

3. The experimental device for simulating the process of well killing with leakage in fracture-cavity formation according to claim 1, characterized in that: The simulated fracture-cavity type stratum structure system specifically comprises: The upper part of the simulated cave (19) is connected to the simulated wellbore (11) through a first simulated fracture (15) and a first pneumatic ball valve (14); a first simulated fracture pressure sensor (13) is arranged between the simulated wellbore and the first pneumatic ball valve (14); The lower part of the simulated cave (19) is connected to the simulated wellbore (11) through a second simulated fracture (18) and a second pneumatic ball valve (17); a second simulated fracture pressure sensor (16) is arranged between the simulated wellbore and the second pneumatic ball valve (17).

4. The experimental device for simulating the process of well killing with leakage and co-existence in fracture-cavity formation according to claim 1, characterized in that: The simulated wellbore system specifically comprises: The simulated wellbore (11) is placed vertically, and the simulated drill string (7) is placed vertically at the exact center of the simulated wellbore (11), with the upper end of the simulated drill string (7) being higher than the simulated wellbore (11); The upper end of the simulated wellbore (11) is connected to the gas-liquid separation tank (6) through a first flow pipe and a return flow meter (8), and an overflow valve (30) is arranged between the return flow meter (8) and the simulated wellbore (11); the lower part of the simulated wellbore (11) is connected to the first simulated crack (15) and the second simulated crack (18), respectively, and the connection positions of the first simulated crack (15) and the second simulated crack (18) and the simulated wellbore (11) have a set height difference; The upper part of the simulated wellbore (11) is connected to a casing pressure sensor (10), the bottom of the simulated wellbore (11) is provided with a bottom hole pressure sensor (12), and the top of the simulated drill string (7) is connected to a vertical pressure sensor (9).

5. The experimental device for simulating the process of well killing with leakage in fracture-cavity formation according to claim 1, characterized in that: The simulated drilling fluid circulation system specifically comprises: The upper end of the simulated wellbore (11) passes through a return flow meter (8) and is connected to the first end of the gas-liquid separation tank (6) through a gas-liquid two-phase pipeline; The second end of the gas-liquid separation tank (6) extends above the liquid storage tank (1) through a gas-liquid two-phase pipeline; A stirring motor (5) is arranged in the liquid storage tank (1); the liquid storage tank (1) is connected to a drilling fluid centrifugal pump (2) through a pipeline; The drilling fluid centrifugal pump (2) is connected to the top of the simulated drill string (7) through a pipeline via a liquid injection control valve (3); a drilling fluid flow meter (4) is provided between the liquid injection control valve (3) and the simulated drill string (7).

6. An experimental method for simulating the well-killing process of leakage coexistence in fracture-cavity formations, characterized in that: The method is implemented based on an experimental device for simulating a process of well killing with leakage and co-existence in fracture-cavity formations as described in any one of claims 1 to 5, and the method comprises: Step S100, connecting a device for simulating the process of leaking and well-killing in a fracture-cavity formation, closing the liquid injection control valve (3), the overflow valve (30), the first pneumatic ball valve (14), the second pneumatic ball valve (17), the gas injection control valve (22) and the constant pressure check valve (26), and confirming the sealing performance of the device; Step S200, after adding clean water and a weighting agent into the liquid storage tank (1), the clean water and the weighting agent are mixed evenly by a stirring motor (5) to obtain a simulated drilling fluid, and the density of the first simulated drilling fluid is measured; Step S300, using the air compressor (25) to make the air storage tank (24) reach a set air storage tank pressure; Step S400, opening the gas injection control valve (22) to allow the gas storage tank (24) to inject compressed air into the simulated cave (19); Step S500, opening the injection control valve (3) and the overflow valve (30), and pumping the simulated drilling fluid in the reservoir (1) into the simulated drill string (7) through the drilling fluid centrifugal pump (2); The simulated drilling fluid in the simulated drill string (7) is returned to the gas-liquid separation tank (6) through the simulated wellbore (11) and the overflow valve (30); The gas-liquid separation tank (6) separates the used simulated drilling fluid into gas and liquid, and injects the separated simulated drilling fluid into the liquid storage tank; Step S600, collecting sensor data through the drilling fluid flow meter (4), the return flow meter (8), the vertical pressure sensor (9), the casing pressure sensor (10), the bottom hole pressure sensor (12), the first simulated fracture pressure sensor (13), the second simulated fracture pressure sensor (16), the simulated cave pressure sensor (20), the gas flow meter (21), the gas tank pressure sensor (23) and the high-speed camera (28), and transmitting the sensor data to the data processor (29); Step S700, when the fluctuation range of the data of the first simulated fracture pressure sensor (13) and the second simulated fracture pressure sensor (16) is less than a preset first stable threshold, based on the pressure difference between the bottom hole pressure of the simulated wellbore (11) and the simulated cave (19), the first pneumatic ball valve (14) and the second pneumatic ball valve (17) are adjusted to control the coexistence of leakage at the lower part of the simulated fracture cave and overflow at the upper part of the fracture cave; Acquiring real-time simulated standpipe pressure through a standpipe pressure sensor (9); Acquiring real-time simulated wellhead pressure through a casing pressure sensor (10); Step S800, when the instantaneous pressure of the simulated wellhead pressure reaches the set judgment value, read the second sensor data of the standpipe pressure sensor (9), the casing pressure sensor (10), the bottom hole pressure sensor (12), the simulated cave pressure sensor (20) and the high-speed camera (28), and record the first simulated standpipe pressure, the first simulated wellhead pressure, the first simulated cave pressure and the first gas-liquid two-phase distribution; Step S900, closing the drilling fluid centrifugal pump (2) and the overflow valve (30), when the real-time simulated wellhead pressure fluctuates within a preset time period and the range is less than a preset second stable threshold, the simulated riser pressure at this time is recorded as the stable riser pressure, the simulated wellhead pressure at this time is recorded as the stable wellhead pressure, the second simulated drilling fluid density required for drilling is calculated, and the simulated drilling fluid in the liquid storage tank (1) is adjusted to the second simulated drilling fluid density; Step S1000, turning on the drilling fluid centrifugal pump (2) to a set displacement, adjusting the relief valve (30) to a set opening, making the real-time simulated wellhead pressure reach the stable wellhead pressure, simulating the current well killing method process, reading the third sensor data of the standpipe pressure sensor (9), the casing pressure sensor (10), the bottom hole pressure sensor (12), the simulated cave pressure sensor (20) and the high-speed camera (28), and recording the second simulated standpipe pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution; Step S1100, based on the first simulated riser pressure, the first simulated wellhead pressure, the first simulated cave pressure, the first gas-liquid two-phase distribution, the second simulated riser pressure, the second simulated wellhead pressure, the second simulated cave pressure and the second gas-liquid two-phase distribution, calculate the simulated wellhead pressure change, the simulated cave pressure change and the gas-liquid flow law, complete the nth round of simulated fracture-cavity formation condition experiment to obtain the nth round of experimental results; Step S1200, select one or more of the new simulated drilling fluid density, set displacement, and well killing method, set n=n+1, and return to step S700.

7. The experimental method for simulating the process of well killing with leakage in fracture-cavity formation according to claim 6, characterized in that: After the air injection control valve (22) is opened to allow the air storage tank (24) to inject compressed air into the simulated cave (19), the method further includes setting the pressure in the simulated cave (19), which specifically includes: The pressure difference between the simulated wellbore (11) and the simulated cave (19) is set, and the constant pressure relief valve (26) is opened to keep the pressure in the simulated cave (19) at a preset simulated cave pressure.

8. The experimental method for simulating the process of well killing with leakage in fracture-cavity formation according to claim 6, characterized in that: After the gas injection control valve (22) is opened to allow the gas storage tank (24) to inject compressed air into the simulated cave (19), the method further includes the step of setting the gas volume in the simulated cave (19), which specifically includes: The simulated cave pressure is set, and when the pressure in the simulated cave (19) reaches the preset simulated cave pressure, the gas injection control valve (22) and the constant pressure relief valve (26) are closed.

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