A multi-mechanism jointing complex formation drilling experimental device and experimental method

Abstract

The present application relates to a kind of multi-mechanism fracture formation drilling complex condition experimental device and experimental method, multi-mechanism fracture formation drilling complex condition experimental device includes simulation wellbore, fracture bin, drill string simulation cylinder, formation fluid plunger pump and drilling fluid plunger pump, drill string simulation cylinder is sleeved in simulation wellbore, interval is reserved between the bottom of simulation wellbore and the lower end of drill string simulation cylinder, the upper end of drill string simulation cylinder is stretched from simulation wellbore upper end, drilling fluid plunger pump is communicated with the upper end of drill string simulation cylinder by first pipeline, and the upper end of simulation wellbore is connected with second pipeline;Fracture bin side is respectively communicated with the lower end of simulation wellbore by third pipeline and fourth pipeline, and formation fluid plunger pump is communicated with fracture bin by fifth pipeline;First back pressure valve and first flow meter are arranged on first pipeline, second back pressure valve and second flow meter are arranged on second pipeline, third back pressure valve and third flow meter are arranged on third pipeline, and fourth back pressure valve and fourth flow meter are arranged on fourth pipeline.

Description

Technical Field

[0001] This invention relates to the field of petroleum engineering technology, specifically to an experimental apparatus and method for drilling complex conditions in multi-mechanism fractured and cavernous formations. Background Technology

[0002] As oil and gas drilling advances towards deep wells, ultra-deep wells, and complex formations, the industry is becoming increasingly challenging. One key concern is successfully drilling within a narrow safety density window. During drilling, the drilling fluid density needs to be controlled between the formation's pore pressure / collapse pressure and fracture pressure / loss pressure. Especially when encountering naturally fractured and vulcanized formations, preventing and controlling drilling fluid loss and complex downhole conditions presents a significant challenge. Currently, downhole complications related to drilling fluid encountered when drilling through fractured and vulcanized formations can be categorized into three types: severe formation loss, fractured formation breathing effect, and formation gravity displacement effect.

[0003] The main principles underlying these three phenomena are as follows:

[0004] (1) Severe Formation Loss: To ensure the safety and reliability of the drilling process, the drilling fluid density is generally higher than the formation pressure equivalent density, and the wellbore pressure is mostly higher than the formation pressure. When drilling encounters fractured and cavitary formations, the wellbore intersects with a large number of formation fractures or karst caves. Under the influence of the pressure difference, the drilling fluid enters the formation through the peri-well fractures, resulting in loss. In severe cases, even loss of return may occur (loss of return: the phenomenon that no drilling fluid flows out of the wellhead).

[0005] (2) Fractured Formation Breathing Effect: During drilling or circulation, the pressure inside the wellbore exceeds the initiation pressure of the surrounding fractures, causing drilling fluid to continuously flow into the formation fractures during circulation. When circulation stops, the pressure inside the wellbore drops rapidly and falls below the initiation pressure, causing the fractures to close and forcing the fluid that previously entered the fractures to flow back into the wellbore. If this occurs in a well section of a formation with well-developed microfractures or during the pumping phase of tubing hoisting, a large amount of fluid outflow is very likely to be detected at the wellhead within a short period of time.

[0006] (3) Formation Gravity Displacement Effect: The formation gravity displacement effect refers to the phenomenon where, when drilling into a formation with fractures and the drilling fluid density is higher than that of the formation fluid (natural gas, water, or oil, etc.), the drilling fluid undergoes gravity displacement with the formation fluid due to the density difference. This phenomenon is more likely to occur when drilling into formations with large fractures or caverns. When the gravity displacement effect occurs, both overflow and leakage may occur simultaneously in the wellbore.

[0007] These three types of downhole complexities are influenced by different factors such as formation, fluids, and wellbore, and the corresponding relationships between these factors and the different types of downhole complexes remain unclear. When encountering these complexities, errors in judgment due to a lack of understanding can lead to various subsequent problems. Therefore, a clear understanding of the dynamic response characteristics of these three types of downhole complexes and the influence of different factors on them is a necessary condition for solving this problem. Summary of the Invention

[0008] In order to solve one or more technical problems existing in the prior art, the present invention provides an experimental device and method for drilling complex conditions in fractured and cavernous formations using multiple mechanisms.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A multi-mechanism experimental device for drilling complex conditions in fractured and cavernous formations, comprising a simulated wellbore, a fracture chamber, a drill string simulation cylinder, a formation fluid plunger pump, and a drilling fluid plunger pump. The drill string simulation cylinder is sleeved inside the simulated wellbore, with a gap reserved between the lower end of the drill string simulation cylinder and the bottom of the simulated wellbore. The upper end of the drill string simulation cylinder extends from the upper end of the simulated wellbore. The drilling fluid plunger pump is connected to the upper end of the drill string simulation cylinder through a first pipeline, and a second pipeline is connected to the upper end of the simulated wellbore.

[0010] The side of the fracture chamber is also connected to the lower end of the simulated wellbore through the third and fourth pipelines respectively, and the formation fluid plunger pump is connected to the fracture chamber through the fifth pipeline;

[0011] The first pipeline is equipped with a first back pressure valve and a first flow meter, the second pipeline is equipped with a second back pressure valve and a second flow meter, the third pipeline is equipped with a third back pressure valve and a third flow meter, and the fourth pipeline is equipped with a fourth back pressure valve and a fourth flow meter.

[0012] The beneficial effects of this invention are: the multi-mechanism fractured formation drilling complex working condition experimental device of this invention can simulate the formation malignant leakage, fractured formation breathing effect and formation gravity replacement effect that occur under different conditions, and monitor the pressure changes inside the fracture in real time, so as to understand the dynamic response characteristics of these three complex working conditions under different formation conditions, as well as the influence of different types of factors on them, and provide theoretical guidance for drilling and completion operations.

[0013] Based on the above technical solution, the present invention can be further improved as follows.

[0014] Furthermore, both the third and fourth pipelines are equipped with swivel couplings.

[0015] The beneficial effect of adopting the above-mentioned further solution is that the rotating coupling makes it convenient to rotate the third and fourth pipelines when the crack chamber is tilted.

[0016] Furthermore, the simulated wellbore is provided with a first liquid outlet at the bottom, the fracture chamber is provided with a second liquid outlet at the bottom, and the fracture chamber is provided with a third liquid outlet at the top.

[0017] Furthermore, the fissure chamber includes a chamber body, a cover plate, and a pneumatic-hydraulic assembly. The cover plate covers the top open end of the chamber body and is detachably connected to the drive end of the pneumatic-hydraulic assembly. Pressure sensors are provided on the bottom of the chamber body and / or the inner surface of the cover plate.

[0018] The advantages of adopting the above-mentioned further solution are: the pressure of the cover plate can be adjusted using a pneumatic-hydraulic assembly; and different specifications of cover plates can be used to meet different experimental needs.

[0019] Furthermore, a fixed width adjustment block is provided on the bottom wall inside the hopper, and the fixed width adjustment block is threadedly connected to the bottom wall inside the hopper.

[0020] The beneficial effect of adopting the above-mentioned further solution is that the setting of the fixed width adjustment block can limit the minimum width of the crack chamber.

[0021] Furthermore, it also includes an expansion chamber, which is equipped with a piston. The piston is slidably connected to the inner wall of the expansion chamber. The piston divides the expansion chamber into a first chamber and a second chamber. The crack chamber is connected to the first chamber of the expansion chamber through a sixth pipeline. The sixth pipeline is equipped with a fifth back pressure valve and a fifth flow meter.

[0022] The beneficial effect of adopting the above-mentioned further scheme is that the setting of the expansion chamber facilitates the simulation of expansion experiments.

[0023] An experimental method for the above-mentioned multi-mechanism fractured-vuggy formation drilling complex working condition experimental device includes:

[0024] Wellbore environment simulation: Turn on the drilling fluid plunger pump and inject drilling fluid into the simulated wellbore using the first pipeline and drill string simulation cylinder. When the drilling fluid used in the experiment is stably discharged from the second pipeline, it can be determined that the drilling fluid has filled the simulated wellbore, thus completing the simulation of the drilling fluid circulation experiment in the simulated wellbore during the drilling process.

[0025] Formation environment simulation: Open the cover plate of the fracture chamber, replace the corresponding cover plate according to the experimental simulation conditions, disconnect the third and fourth pipelines and connect the fifth pipeline according to the experimental simulation conditions, turn on the formation fluid plunger pump, and use the formation fluid plunger pump to inject formation fluid into the fracture chamber from the bottom; when the formation fluid is stably discharged from the top of the fracture chamber, it can be determined that the formation fluid has filled the fracture chamber, turn off the formation fluid plunger pump, and the formation environment simulation is completed.

[0026] The beneficial effects of this invention are: the experimental method of this invention can simulate the wellbore environment and the formation environment.

[0027] Furthermore, it also includes experimental simulations of leaky structures with gaps:

[0028] (1) Simulated wellbore pressure environment loading: After the wellbore environment simulation is completed, while ensuring that the drilling fluid plunger pump is turned on, the pressure value of the third back pressure valve is set to the preset leakage pressure value. When the fluid pressure value in the simulated wellbore is greater than the preset leakage pressure value, the drilling fluid in the simulated wellbore enters the fracture chamber through the third pipeline.

[0029] (2) Pressure environment loading of fracture chamber: Set the minimum width of the fracture in the fracture chamber and set different fracture chamber pressures to make the width of the fracture chamber adjustable. Disconnect the third and fourth pipelines and connect the fifth pipeline. Turn on the formation fluid plunger pump and use the formation fluid plunger pump to inject formation fluid into the fracture chamber from the bottom. The formation fluid flows out from the third outlet on the cover plate of the fracture chamber. The fracture chamber is filled with formation fluid to simulate different fracture chamber pressure environments.

[0030] (3) Simulation of fracture chamber expansion: After the simulated wellbore pressure environment is loaded, the fracture chamber and the expansion chamber are connected through the sixth pipeline. The expansion set pressure value of the fifth back pressure valve on the sixth pipeline is greater than the preset leakage pressure value of the third back pressure valve. When the fluid pressure value in the fracture chamber is greater than the expansion set pressure value, the formation fluid enters the expansion chamber. When the expansion set pressure value of the fifth back pressure valve is 0, the simulation of infinite fracture leakage is realized. The increment of fluid in the expansion chamber during the experiment is the increment of drilling fluid leakage into the fracture chamber.

[0031] (4) Simulation of fracture chamber angle adjustment: After loading the simulated wellbore pressure environment, the tilt angle of the fracture chamber is adjusted by rotation according to experimental needs to simulate different angles of the fracture chamber.

[0032] The beneficial effect of adopting the above-mentioned further solution is that the present invention can also realize the experimental simulation of leakage due to cracks under different working conditions.

[0033] Furthermore, it also includes an experimental simulation of the formation breathing effect in fractured formations: after completing the formation environment simulation, the formation fluid plunger pump is turned off and the drilling fluid plunger pump is turned on, making the fracture chamber width adjustable. The pressure value of the first back pressure valve on the first pipeline is set to be greater than the pressure value of the third back pressure valve on the third pipeline. At this time, the drilling fluid enters the fracture chamber through the third pipeline. The pressure value of the first back pressure valve on the first pipeline is set to be less than the pressure value of the third back pressure valve on the third pipeline. At this time, the drilling fluid flows back from the fracture chamber into the simulated wellbore through the third pipeline.

[0034] The beneficial effect of adopting the above-mentioned further scheme is that it can effectively simulate the breathing effect of fractured formations.

[0035] Furthermore, it also includes an experimental simulation of the formation gravity replacement effect: under this simulation condition, the density of the formation fluid in the fracture chamber is less than the density of the drilling fluid; after the formation environment simulation is completed, the formation fluid plunger pump is turned off and the drilling fluid plunger pump is turned on, making the width of the fracture chamber adjustable, and rotating the fracture chamber by a certain angle so that the third and fourth pipelines are located at the lower end of the entire fracture chamber. The third and fourth pipelines are connected, allowing the drilling fluid to enter the fracture chamber through the third pipeline, and pushing the formation fluid in the fracture chamber into the simulated wellbore through the fourth pipeline.

[0036] The beneficial effect of adopting the above-mentioned further scheme is that it can effectively simulate the formation gravity replacement effect. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the simulated wellbore structure of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of the fissure chamber and the expansion chamber of the present invention;

[0039] Figure 3 This is a schematic diagram of the experimental apparatus for drilling complex conditions in fractured and cavernous formations according to the present invention.

[0040] The attached diagram lists the components represented by each number as follows:

[0041] 1. Simulated wellbore; 11. First pipeline; 12. Second pipeline; 13. First back pressure valve; 14. First flow meter; 15. Second back pressure valve; 16. Second flow meter; 17. First outlet;

[0042] 2. Cracked compartment; 20. Rotary coupling; 21. Third pipeline; 22. Fourth pipeline; 23. Third back pressure valve; 24. Third flow meter; 25. Fourth back pressure valve; 26. Fourth flow meter; 27. Cover plate; 271. Compartment body; 272. Pressure sensor; 28. Second outlet; 29. ​​Third outlet;

[0043] 3. Drill string simulation tube; 4. Formation fluid plunger pump; 41. Fifth pipeline; 5. Drilling fluid plunger pump;

[0044] 6. Expansion chamber; 61. Piston; 62. Fifth flow meter; 63. Fifth back pressure valve; 64. Sixth pipeline;

[0045] 7. Controller; 8. High-pressure gas cylinder; 9. Waste liquid tank. Detailed Implementation

[0046] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0047] like Figures 1-3 As shown in the figure, this embodiment of a multi-mechanism fractured formation drilling complex working condition experimental device includes a simulated wellbore 1, a fracture chamber 2, a drill string simulation cylinder 3, a formation fluid plunger pump 4, and a drilling fluid plunger pump 5. The drill string simulation cylinder 3 is sleeved inside the simulated wellbore 1, and a gap is reserved between the lower end of the drill string simulation cylinder 3 and the bottom of the simulated wellbore 1. The upper end of the drill string simulation cylinder 3 extends from the upper end of the simulated wellbore 1. The drilling fluid plunger pump 5 is connected to the upper end of the drill string simulation cylinder 3 through a first pipeline 11. The upper end of the simulated wellbore 1 is connected to a second pipeline 12.

[0048] The side of the fracture chamber 2 is also connected to the lower end of the simulated wellbore 1 through the third pipeline 21 and the fourth pipeline 22 respectively, and the formation fluid plunger pump 4 is connected to the fracture chamber 2 through the fifth pipeline 41.

[0049] The first pipeline 11 is equipped with a first back pressure valve 13 and a first flow meter 14, the second pipeline 12 is equipped with a second back pressure valve 15 and a second flow meter 16, the third pipeline 21 is equipped with a third back pressure valve 23 and a third flow meter 24, and the fourth pipeline 22 is equipped with a fourth back pressure valve 25 and a fourth flow meter 26.

[0050] like Figure 1 As shown, both the third pipeline 21 and the fourth pipeline 22 in this embodiment are equipped with rotating couplings 20. The rotating couplings facilitate the rotation of the third and fourth pipelines when the fracture chamber is tilted.

[0051] like Figures 1-3 As shown, the simulated wellbore 1 in this embodiment is provided with a first liquid outlet 17 at the bottom, the fracture chamber 2 is provided with a second liquid outlet 28 at the bottom, and the fracture chamber 2 is provided with a third liquid outlet 29 at the top.

[0052] like Figure 2 As shown, the fissure chamber 2 in this embodiment includes a chamber body 271, a cover plate 27, and a pneumatic-hydraulic assembly. The cover plate 27 covers the open top end of the chamber body 271 and is detachably connected to the drive end of the pneumatic-hydraulic assembly. A pressure sensor 272 is provided on the bottom of the chamber body 271 and / or the inner surface of the cover plate 27. Specifically, the cover plate 27 has a third liquid outlet 29, and the bottom of the chamber body 271 has a second liquid outlet 28. The pressure of the cover plate can be adjusted by the pneumatic-hydraulic assembly. Different specifications of cover plates can be replaced according to different experimental needs.

[0053] A further embodiment of this solution includes a fixed width adjustment block on the bottom wall of the inner side of the chamber 271, the fixed width adjustment block being threadedly connected to the bottom wall of the inner side of the chamber 271. The fixed width adjustment block limits the minimum width of the crack chamber. When the width needs to be reduced, the fixed width adjustment block can be rotated forward towards the bottom wall of the chamber; when the width needs to be increased, the fixed width adjustment block can be rotated backward away from the bottom wall of the chamber.

[0054] like Figure 2 and Figure 3 As shown, the experimental apparatus in this embodiment also includes an expansion chamber 6, within which a piston 61 is installed. The piston 61 is slidably and sealingly connected to the inner wall of the expansion chamber 6, dividing the expansion chamber 6 into a first chamber and a second chamber. The crack chamber 2 is connected to the first chamber of the expansion chamber 6 via a sixth pipeline 64, on which a fifth back pressure valve 63 and a fifth flow meter 62 are installed. The expansion chamber facilitates the simulation of expansion experiments. The expansion chamber also has a scale for recording the internal fluid volume.

[0055] Among them, such as Figure 3 As shown, the experimental apparatus for complex drilling conditions in fractured and cavernous formations in this embodiment also includes a controller 7, a high-pressure gas supply cylinder 8, and a waste liquid pool 9. The waste liquid pool 9 can be connected to a second pipeline and collects drilling fluid from the simulated wellbore. The controller 7 is connected to the high-pressure gas supply cylinder 8 and each back pressure valve, and is used to regulate the pipeline pressure.

[0056] The multi-mechanism fractured formation drilling complex working condition experimental device of this embodiment can simulate the formation malignant leakage, fractured formation breathing effect and formation gravity replacement effect under different conditions, and monitor the pressure change inside the fracture in real time. It can also understand the dynamic response characteristics of these three complex working conditions under different formation conditions, as well as the influence of different types of factors on them, and provide theoretical guidance for drilling and completion operations.

[0057] An experimental method for the above-mentioned multi-mechanism fractured-vuggy formation drilling complex working condition experimental device in this embodiment includes:

[0058] Wellbore environment simulation: Turn on the drilling fluid plunger pump 5, and inject drilling fluid into the simulated wellbore 1 through the first pipeline 11 and the drill string simulation cylinder 3. When the drilling fluid used in the experiment is stably discharged from the second pipeline 12, it can be determined that the drilling fluid has filled the simulated wellbore 1, thus completing the simulation of the drilling fluid circulation experiment in the simulated wellbore during the drilling process.

[0059] Formation environment simulation: Open the cover plate 27 of fracture chamber 2, replace the corresponding cover plate 27 according to the experimental simulation conditions, disconnect the third pipeline 21 and the fourth pipeline 22 according to the experimental simulation conditions, connect the fifth pipeline 41, turn on the formation fluid plunger pump 4, and use the formation fluid plunger pump 4 to inject formation fluid into fracture chamber 2 from the bottom; when the formation fluid is stably discharged from the top of fracture chamber 2, it can be determined that the formation fluid has filled fracture chamber 2, turn off the formation fluid plunger pump 4, and the formation environment simulation is completed.

[0060] Furthermore, the experimental method in this embodiment also includes simulation of leaky pores:

[0061] (1) Simulated wellbore pressure environment loading: After the wellbore environment simulation is completed, while ensuring that the drilling fluid plunger pump 5 is turned on, the pressure value of the third back pressure valve 23 is set to the preset leakage pressure value. When the fluid pressure value in the simulated wellbore 1 is greater than the preset leakage pressure value, the drilling fluid in the simulated wellbore 1 enters the fracture chamber 2 through the third pipeline 21.

[0062] (2) Loading the pressure environment of the fracture chamber: Set the minimum width of the fracture in the fracture chamber 2 and set different fracture chamber pressures to make the width of the fracture chamber 2 adjustable. Disconnect the third pipeline 21 and the fourth pipeline 22, connect the fifth pipeline 41, turn on the formation fluid plunger pump 4, and use the formation fluid plunger pump 4 to inject formation fluid into the fracture chamber 2 from the bottom to simulate different fracture chamber pressure environments.

[0063] (3) Simulation of fracture chamber 2 expansion: After the pressure environment of the simulated wellbore 1 is loaded, fracture chamber 2 and expansion chamber 6 are connected through the sixth pipeline 64. The expansion set pressure value of the fifth back pressure valve 63 on the sixth pipeline 64 is greater than the preset leakage pressure value of the third back pressure valve 23. When the fluid pressure value in fracture chamber 2 is greater than the expansion set pressure value, the formation fluid enters the expansion chamber 6. When the expansion set pressure value of the fifth back pressure valve 63 is 0, the simulation of infinite fracture leakage is realized. The increment of fluid in expansion chamber 6 during the experiment is the increment of drilling fluid leakage into fracture chamber 2.

[0064] (4) Simulation of fracture chamber 2 angle adjustment: After the pressure environment of the simulated wellbore 1 is loaded, the tilt angle of fracture chamber 2 is adjusted by rotation according to the experimental requirements to simulate different angles of fracture chamber 2.

[0065] Furthermore, the experimental method of this embodiment also includes a simulation of the formation breathing effect: after completing the formation environment simulation, the formation fluid plunger pump 4 is turned off and the drilling fluid plunger pump 5 is turned on, making the width of the fracture chamber 2 adjustable. The pressure value of the first back pressure valve 13 on the first pipeline 11 is set to be greater than the pressure value of the third back pressure valve 23 on the third pipeline 21. At this time, the drilling fluid enters the fracture chamber 2 through the third pipeline 21. The pressure value of the first back pressure valve 13 on the first pipeline 11 is set to be less than the pressure value of the third back pressure valve 23 on the third pipeline 21. At this time, the drilling fluid flows back from the fracture chamber 2 into the simulated wellbore 1 through the third pipeline 21.

[0066] Furthermore, the experimental method in this embodiment also includes a formation gravity displacement effect simulation: under this simulation condition, the density of the formation fluid in the fracture chamber 2 is less than the density of the drilling fluid; after the formation environment simulation is completed, the formation fluid plunger pump 4 is turned off and the drilling fluid plunger pump 5 is turned on, making the width of the fracture chamber 2 adjustable, and the fracture chamber 2 is rotated at a certain angle so that the third pipeline 21 and the fourth pipeline 22 are located at the lower end of the entire fracture chamber 2. The third pipeline 21 and the fourth pipeline 22 are connected, so that the drilling fluid enters the fracture chamber 2 through the third pipeline 21, and the formation fluid in the fracture chamber 2 is pushed into the simulated wellbore through the fourth pipeline 22.

[0067] In this embodiment, the drilling fluid and the formation fluid can be the same fluid or different fluids. When conducting formation gravity displacement effect simulation experiments, fluids of different densities are used.

[0068] The experimental method in this embodiment can simulate both the wellbore and formation environments, and can also simulate formation leakage, fractured formation breathing effects, and formation gravity replacement effects individually. This experimental device can also simulate complex downhole conditions where formation leakage, fractured formation breathing effects, and formation gravity replacement effects occur simultaneously, such as when fractured formation breathing effects and drilling fluid leakage occur simultaneously, or when formation gravity replacement effects and formation breathing effects occur simultaneously. This experimental device can simulate three complex conditions under different fracture surface conditions, can monitor internal pressure changes within fractures in real time, and can arbitrarily adjust the angle of the fracture surface to achieve a more realistic simulation of rock formation conditions. For complex conditions such as fractured leakage and fractured formation breathing effects, this experimental device can simulate the propagation of infinite and finite fractures. This embodiment provides, for the first time, a specific method for simulating complex downhole conditions where formation leakage, fractured formation breathing effects, and formation gravity replacement effects occur simultaneously.

[0069] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0070] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0071] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0072] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations, characterized in that, A multi-mechanism experimental setup for drilling complex conditions in fractured and vulcanized formations was employed. This setup includes a simulated wellbore, a fracture chamber, a drill string simulation cylinder, a formation fluid plunger pump, and a drilling fluid plunger pump. The drill string simulation cylinder is housed within the simulated wellbore, with a pre-existing gap between its lower end and the bottom of the simulated wellbore. Its upper end extends from the upper end of the simulated wellbore. The drilling fluid plunger pump is connected to the upper end of the drill string simulation cylinder via a first pipeline, and a second pipeline connects to the upper end of the simulated wellbore. The fracture chamber is further connected to the lower end of the simulated wellbore via third and fourth pipelines, respectively. The formation fluid plunger pump is connected to the fracture chamber via a fifth pipeline. The first pipeline is equipped with a first back pressure valve and a first flow meter; the second pipeline is equipped with a second back pressure valve and a second flow meter; the third pipeline is equipped with a third back pressure valve and a third flow meter; and the fourth pipeline is equipped with a fourth back pressure valve and a fourth flow meter. The experimental methods include: Wellbore environment simulation: Turn on the drilling fluid plunger pump and inject drilling fluid into the simulated wellbore using the first pipeline and drill string simulation cylinder. When the drilling fluid used in the experiment is stably discharged from the second pipeline, it can be determined that the drilling fluid has filled the simulated wellbore, thus completing the simulation of the drilling fluid circulation experiment in the simulated wellbore during the drilling process. Formation environment simulation: Open the cover plate of the fracture chamber, replace the cover plate with the corresponding one according to the experimental simulation conditions, disconnect the third and fourth pipelines and connect the fifth pipeline according to the experimental simulation conditions, turn on the formation fluid plunger pump and use the formation fluid plunger pump to inject formation fluid into the fracture chamber from the bottom; when the formation fluid is stably discharged from the top of the fracture chamber, it can be determined that the formation fluid has filled the fracture chamber, turn off the formation fluid plunger pump, and the formation environment simulation is completed. Simulation of leaky seams: (1) Simulated wellbore pressure environment loading: After the wellbore environment simulation is completed, while ensuring that the drilling fluid plunger pump is turned on, the pressure value of the third back pressure valve is set to the preset leakage pressure value. When the fluid pressure value in the simulated wellbore is greater than the preset leakage pressure value, the drilling fluid in the simulated wellbore enters the fracture chamber through the third pipeline. (2) Pressure environment loading of fracture chamber: Set the minimum width of the fracture in the fracture chamber and set different fracture chamber pressures to make the width of the fracture chamber adjustable. Disconnect the third and fourth pipelines and connect the fifth pipeline. Turn on the formation fluid plunger pump and use the formation fluid plunger pump to inject formation fluid into the fracture chamber from the bottom. The formation fluid flows out from the third outlet on the cover plate of the fracture chamber. The fracture chamber is filled with formation fluid to simulate different fracture chamber pressure environments. (3) Simulation of fracture chamber expansion: After loading the simulated wellbore pressure environment, the fracture chamber and the expansion chamber are connected through the sixth pipeline. The expansion set pressure value of the fifth back pressure valve on the sixth pipeline is greater than the preset leakage pressure value of the third back pressure valve. When the fluid pressure value in the fracture chamber is greater than the expansion set pressure value, the formation fluid enters the expansion chamber. When the expansion set pressure value of the fifth back pressure valve is 0, the simulation of infinite fracture leakage is realized. The increment of fluid in the expansion chamber during the experiment is the increment of drilling fluid leakage into the fracture chamber. (4) Simulation of fracture chamber angle adjustment: After loading the simulated wellbore pressure environment, the tilt angle of the fracture chamber is adjusted by rotation according to the experimental requirements to simulate different angles of the fracture chamber.

2. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, Both the third and fourth pipelines are equipped with swivel couplings.

3. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, The simulated wellbore has a first outlet at the bottom, the fracture chamber has a second outlet at the bottom, and the fracture chamber has a third outlet at the top.

4. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, The fissure chamber includes a chamber body, a cover plate, and a pneumatic-hydraulic assembly. The cover plate covers the open top end of the chamber body and is detachably connected to the drive end of the pneumatic-hydraulic assembly. Pressure sensors are provided on the bottom of the chamber body and / or the inner surface of the cover plate.

5. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 4, characterized in that, A fixed width adjustment block is also provided on the bottom wall inside the hopper, and the fixed width adjustment block is threadedly connected to the bottom wall inside the hopper.

6. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, The experimental apparatus also includes an expansion chamber, which contains a piston that is slidably and sealed to the inner wall of the expansion chamber. The piston divides the expansion chamber into a first chamber and a second chamber. The crack chamber is connected to the first chamber of the expansion chamber via a sixth pipeline, which is equipped with a fifth back pressure valve and a fifth flow meter.

7. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, The experimental method also includes a simulation of the formation breathing effect: after completing the formation environment simulation, the formation fluid plunger pump is turned off and the drilling fluid plunger pump is turned on, making the fracture chamber width adjustable. The pressure value of the first back pressure valve on the first pipeline is set to be greater than the pressure value of the third back pressure valve on the third pipeline. At this time, the drilling fluid enters the fracture chamber through the third pipeline. The pressure value of the first back pressure valve on the first pipeline is set to be less than the pressure value of the third back pressure valve on the third pipeline. At this time, the drilling fluid flows back from the fracture chamber into the simulated wellbore through the third pipeline.

8. The experimental method for drilling complex conditions in multi-mechanism fractured-vuggy formations according to claim 1, characterized in that, The experimental method also includes a formation gravity displacement effect simulation: under this simulation condition, the density of the formation fluid in the fracture chamber is less than the density of the drilling fluid; after the formation environment simulation is completed, the formation fluid plunger pump is turned off and the drilling fluid plunger pump is turned on, making the width of the fracture chamber adjustable, and the fracture chamber is rotated at a certain angle so that the third and fourth pipelines are located at the lower end of the entire fracture chamber. The third and fourth pipelines are connected, allowing the drilling fluid to enter the fracture chamber through the third pipeline, and pushing the formation fluid in the fracture chamber into the simulated wellbore through the fourth pipeline.

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