阅读说明：本技术 一种天然裂缝地层呼吸效应的模拟装置和方法 (Simulation device and method for natural fracture stratum respiration effect ) 是由 李�昊 李秉轩 孙宝江 殷志明 王志远 高永海 施程振 于 2020-12-17 设计创作，主要内容包括：本发明公开一种天然裂缝地层呼吸效应的模拟装置和方法,涉及石油天然气工业钻完井技术领域室内实验技术领域,包括试件和供液系统,所述试件内设置有人造裂缝,所述人造裂缝从所述试件的第一端面开始向所述试件内部延伸,但不贯穿所述试件,所述供液系统用于向所述人造裂缝中提供液体；所述试件设置于真三轴试验机上,由真三轴试验机提供压力。本实验装置和实施方式在还原真实地层条件的情况下对天然裂缝地层呼吸效益进行实验研究和定量分析,能为深水钻井钻遇天然裂缝地层提供技术参考,加强对呼吸效应的认识,减少因对呼吸效应的误判而造成的井涌、井漏等井下复杂状况的发生,节约钻井成本,提高钻井效率,降低钻井风险。(The invention discloses a simulation device and a simulation method for a natural fracture stratum respiration effect, which relate to the technical field of indoor experiments in the technical field of drilling and completion in the petroleum and gas industry, and comprise a test piece and a liquid supply system, wherein an artificial fracture is arranged in the test piece, the artificial fracture extends from a first end face of the test piece to the interior of the test piece but does not penetrate through the test piece, and the liquid supply system is used for supplying liquid to the artificial fracture; the test piece is arranged on the true triaxial testing machine, and pressure is provided by the true triaxial testing machine. The experimental device and the implementation mode carry out experimental research and quantitative analysis on the respiratory benefit of the natural fracture stratum under the condition of reducing the real stratum condition, can provide technical reference for the deepwater drilling to meet the natural fracture stratum, strengthen the cognition on the respiratory effect, reduce the occurrence of underground complex conditions such as well kick, well leakage and the like caused by misjudgment on the respiratory effect, save the drilling cost, improve the drilling efficiency and reduce the drilling risk.)

1. The simulation device for the natural fracture stratum respiration effect is characterized by comprising a test piece and a liquid supply system, wherein an artificial fracture is arranged in the test piece, the artificial fracture extends from a first end face of the test piece to the interior of the test piece but does not penetrate through the test piece, and the liquid supply system is used for supplying liquid into the artificial fracture; the test piece is arranged on the true triaxial testing machine, and pressure is provided by the true triaxial testing machine.

2. The simulation device of natural fracture formation respiration effect of claim 1, wherein the test piece comprises a core and a gland, and the core is arranged in the gland; the artificial crack extends from the first end face of the core to the interior of the core but does not penetrate through the core, a prefabricated through hole is formed in one side, corresponding to the first end face, of the sealing sleeve, and the prefabricated through hole is communicated with the liquid supply system.

3. The simulation apparatus of natural fracture formation breathing effect of claim 2, wherein the gland is a cement gland.

4. The simulation apparatus of natural fracture formation respiration effect of claim 2, wherein a through hole is formed on the loading block corresponding to the first end surface on the true triaxial tester.

5. The apparatus for simulating a natural fracture formation breathing effect of claim 4, wherein the diameter of the through hole is equal to the diameter of the preformed through hole.

6. The apparatus of claim 1, wherein the fluid supply system comprises a first fluid reservoir, a second fluid reservoir, a hydraulic pump, a first valve, a second valve, and a backpressure valve; the first valve and the hydraulic pump are sequentially arranged between the first liquid storage tank and the prefabricated through hole; the back pressure valve and the second valve are sequentially arranged between the second liquid storage tank and the prefabricated through hole.

7. The simulation device of natural fracture formation respiration effect of claim 6, wherein the prefabricated through hole is communicated with one end of a main pipeline, and the other end of the main pipeline is communicated with the first liquid storage tank and the second liquid storage tank through a liquid inlet branch and a liquid outlet branch respectively; the first valve and the hydraulic pump are arranged on the liquid inlet branch, and the back pressure valve and the second valve are arranged on the liquid outlet branch; and a flowmeter and a pressure gauge are arranged on the main pipeline.

8. The simulation apparatus of natural fracture formation respiration effect of claim 7, wherein a pressure regulating valve is arranged on the liquid inlet pipeline and is positioned between the hydraulic pump and the main pipeline.

9. Use of a device for simulating the breathing effect of a natural fracture formation according to any of claims 1 to 8, characterized in that it comprises the following steps:

the method comprises the following steps that firstly, based on the simulated natural fracture stratum parameters, the initial pressures of a pressure regulating valve and a back pressure valve are matched with the pressure of a shaft near the simulated stratum;

step two, starting the true triaxial testing machine to pressurize the test piece at sigma₁Load applied in direction, matched to natural fracture cracking pressure, at σ₂Applying load in direction, matched with the confining pressure of the simulated formation, at σ₃Applying load in the direction to match the simulated formation pore pressure;

starting hydraulic pump injection until the reading of the pressure gauge is not obviously changed, adjusting the pressure regulating valve, gradually increasing the hydraulic pressure in the main pipeline until the simulated wellbore pressure exceeds the simulated formation natural crack starting pressure, stopping pressure regulation at the moment, and recording the reading change of the flowmeter in real time until the reading of the flowmeter is not obviously changed;

and step four, closing the hydraulic pump, opening the liquid outlet branch, and recording the real-time change of the reading of the flowmeter until the reading of the flowmeter is not obviously changed.

Technical Field

The invention relates to the technical field of indoor experiments in the technical field of drilling and completion in the petroleum and gas industry, in particular to a device and a method for simulating a natural fracture stratum respiration effect.

Background

With the development of the oil and gas industry, the oil and gas demand is continuously increased, the conventional land oil and gas development cannot meet the demand, the exploration and development of oil and gas are developed towards the deep complex stratum and deep water of the land, in the areas, the complex stratum environment can bring a series of drilling technical problems, the stratum respiration effect caused by the narrow operation window is one of the common underground complex conditions, and the safety drilling problem caused by the respiration effect is more and more prominent.

In the fields of deep ground strata and deep water, the pressure of overlying strata of the strata is low due to complex geological conditions, so that the fracture pressure gradient of the strata is low, the range between pore pressure and stratum fracture pressure is narrow, and a narrow operation window is formed.

When drilling operation is carried out at a narrow window, the Equivalent Circulating Density (ECD) of drilling fluid is easy to exceed the fracture pressure of a stratum, the drilling fluid is lost, and after the pump is stopped, the ECD is reduced, the fluid lost to the stratum is spit back into a shaft, and the process is called a breathing effect.

Misjudgment of formation breathing effects and kicks can cause a series of problems: if the breathing effect is misjudged as a kick, the usual treatment is to increase the drilling fluid density, which means that the bottom hole pressure will exceed the formation fracture pressure further and cause more severe loss. Therefore, the stratum respiration effect is correctly and timely identified, and appropriate treatment measures are taken, so that the non-operation time in the drilling process can be greatly reduced, the operation cost is saved, and the safety factor is improved.

According to the research of foreign scholars, the forming mechanism of the respiratory effect mainly comprises: the method comprises the following steps of (1) a breathing effect caused by deformation of a shaft, a breathing effect caused by thermal expansion of drilling fluid and a breathing effect caused by dynamic opening and closing of a natural fracture stratum, wherein the dynamic opening and closing of limited fractures in the stratum is a main mechanism for causing the breathing effect.

In the prior art, the experimental study aiming at the stratum respiration effect mainly studies the characteristics of a core such as a crack in a coring mode, and the experimental process has no characteristic of simulating dynamic opening and closing of the crack respiration effect, so that the reference significance of the experimental result on the respiration effect under the actual drilling condition is limited.

Therefore, a method for simulating the natural fracture stratum respiration effect is provided by combining a true triaxial rigid servo testing machine, and the natural fracture stratum respiration effect is researched, so that reference is provided when the actual drilling well meets the natural fracture stratum, the drilling operation is guided, and the drilling risk is effectively reduced.

Disclosure of Invention

In order to solve the technical problems, the invention provides a device and a method for simulating the respiratory effect of a natural fracture stratum, which can simulate wellbore pressure, stratum confining pressure, pore pressure and natural fracture opening pressure; the influence of different pressures on the stratum respiration effect is researched by adjusting the magnitude of the pressure value, dynamic opening and closing of the fracture can be simulated through the pressure difference between the wellbore pressure and the fracture opening pressure, and the leakage and return flow of the drilling fluid are characterized by the flowmeter, so that dynamic simulation and quantitative characterization of the natural fracture stratum respiration effect are realized.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a simulation device for a natural fracture stratum respiration effect, which comprises a test piece and a liquid supply system, wherein an artificial fracture is arranged in the test piece, the artificial fracture extends from a first end face of the test piece to the interior of the test piece but does not penetrate through the test piece, and the liquid supply system is used for supplying liquid to the artificial fracture; the test piece is arranged on the true triaxial testing machine, and pressure is provided by the true triaxial testing machine.

Optionally, the test piece comprises a core and a seal sleeve, and the core is arranged in the seal sleeve; the artificial crack extends from the first end face of the core to the interior of the core but does not penetrate through the core, a prefabricated through hole is formed in one side, corresponding to the first end face, of the sealing sleeve, and the prefabricated through hole is communicated with the liquid supply system.

Optionally, the sealing sleeve is a cement sealing sleeve.

Optionally, a through hole is formed in the loading block, corresponding to the first end face, of the true triaxial testing machine.

Optionally, the diameter of the through hole is equal to the diameter of the preformed through hole.

Optionally, the liquid supply system includes a first liquid storage tank, a second liquid storage tank, a hydraulic pump, a first valve, a second valve and a back pressure valve; the first valve and the hydraulic pump are sequentially arranged between the first liquid storage tank and the prefabricated through hole; the back pressure valve and the second valve are sequentially arranged between the second liquid storage tank and the prefabricated through hole.

Optionally, the prefabricated through hole is communicated with one end of a main pipeline, and the other end of the main pipeline is communicated with the first liquid storage tank and the second liquid storage tank through a liquid inlet branch and a liquid outlet branch respectively; the first valve and the hydraulic pump are arranged on the liquid inlet branch, and the back pressure valve and the second valve are arranged on the liquid outlet branch; and a flowmeter and a pressure gauge are arranged on the main pipeline.

Optionally, a pressure regulating valve is arranged on the liquid inlet pipeline, and the pressure regulating valve is located between the hydraulic pump and the main pipeline.

The invention also discloses a use method of the simulation device for the natural fracture formation respiration effect, which comprises the following steps:

the method comprises the following steps that firstly, based on the simulated natural fracture stratum parameters, the initial pressures of a pressure regulating valve and a back pressure valve are matched with the pressure of a shaft near the simulated stratum;

step two, starting the true triaxial testing machine to pressurize the test piece at sigma₁Load applied in direction, matched to natural fracture cracking pressure, at σ₂Applying load in direction, matched with the confining pressure of the simulated formation, at σ₃Directionally applying a load and simulating formation poresThe gap pressure is matched;

starting hydraulic pump injection until the reading of the pressure gauge is not obviously changed, adjusting the pressure regulating valve, gradually increasing the hydraulic pressure in the main pipeline until the simulated wellbore pressure exceeds the simulated formation natural crack starting pressure, stopping pressure regulation at the moment, and recording the reading change of the flowmeter in real time until the reading of the flowmeter is not obviously changed;

and step four, closing the hydraulic pump, opening the liquid outlet branch, and recording the real-time change of the reading of the flowmeter until the reading of the flowmeter is not obviously changed.

Compared with the prior art, the invention has the following technical effects:

the respiration effect is researched by combining a true triaxial test device, the true triaxial test device can be loaded in three main stress directions of the rock core respectively to simulate formation confining pressure, pore pressure and fracture formation opening pressure under the condition of a real formation, and the condition of the real formation is restored; the traditional experimental mode of studying the respiration effect adopts natural fracture rock core more, and the fracture opening pressure that takes place the respiration effect is very high, and is very high to experimental facilities's pressure-bearing and pressure supply requirement, has also improved the experiment risk. The artificial cracks are adopted, the opening pressure of the natural cracks can be set independently, the requirements on experimental equipment are reduced, the experimental difficulty is reduced, and the experimental safety is enhanced; the method can record the stratum respiration effect process in real time, quantitatively reflect the time-varying rule of key parameters such as the leakage rate and the accumulated leakage quantity of the wellbore fluid, and realize the quantitative analysis of the natural fracture stratum respiration effect; the breathing effect caused by opening and closing of the natural fracture stratum can be simulated, and the dynamic representation of the breathing effect of the natural fracture stratum is realized; the experimental device and the implementation mode carry out experimental research and quantitative analysis on the respiratory benefit of the natural fracture stratum under the condition of reducing the real stratum condition, can provide technical reference for the deepwater drilling to meet the natural fracture stratum, strengthen the cognition on the respiratory effect, reduce the occurrence of underground complex conditions such as well kick, well leakage and the like caused by misjudgment on the respiratory effect, save the drilling cost, improve the drilling efficiency and reduce the drilling risk.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a simulation apparatus for natural fracture formation respiration effect according to the present invention;

FIG. 2 is a schematic top view of a loading portion of the simulation apparatus for natural fracture formation respiration effect according to the present invention;

FIG. 3 is a flow chart of steps of a natural fracture formation respiration effect simulator in the method for using the natural fracture formation respiration effect simulator according to the present invention;

fig. 4 is a schematic diagram of the crack deformation law in the respiration effect process.

Description of reference numerals: 1. a second liquid storage tank; 2. a back pressure valve; 3. a second valve; 4. a pressure gauge; 5. a pressure regulating valve; 6. a hydraulic pump; 7. a first valve; 8. a first liquid storage tank; 9. a high-precision flow meter; 10. a true triaxial tester; 11. a cement seal sleeve; 12. an artificial fracture core.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As used herein, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used in a descriptive sense only and not for purposes of limitation, with reference to the examples provided.

Unless defined otherwise, scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Where not illustrated, all valves, liquid pumps, etc. herein default to a closed state.

The "breathing effect" of the formation refers to the phenomenon that the window of adjustable ECD (circulating equivalent drilling fluid density) is small due to the narrow operation window of the formation, namely the narrow windows of the pore pressure and the fracture pressure of the formation, when the ECD exceeds the fracture pressure gradient of the formation, the ECD can cause leakage, and the decrease of the ECD after the leakage can cause the backflow of the leaked fluid.

The respiration effect is particularly prominent in the field of deepwater drilling, and the deepwater drilling has the defects that the stratum rupture pressure is lower, the operation window is narrower and the respiration effect is relatively easier to occur due to the fact that the pressure of an overlying sea water layer is lower than that of an overlying rock layer of a land drilling.

The main mechanism of formation of the respiratory effect can be divided into three parts: the respiratory effect caused by the deformation of a shaft, the respiratory effect caused by the thermal expansion of drilling fluid and the respiratory effect caused by the dynamic opening and closing of a natural fracture stratum; among them, dynamic opening and closing of finite volume natural fractures is the main mechanism causing the respiratory effect of deep water drilling.

The invention provides a simulation method and a device for the respiratory effect of a natural fracture stratum, which can simulate the pressure of a shaft, the confining pressure of the stratum and the opening pressure of the natural fracture, can quantitatively simulate the respiratory effect of the natural fracture stratum by regulating the pressure and representing the respiratory phenomenon through a flowmeter, and can simulate and realize the dynamic opening and closing characteristics of the fracture under the actual working condition through the combined action of a loading block and the confining pressure, so that the simulation result is closer to the actual drilling working condition, thereby providing technical support for drilling, particularly deepwater drilling, providing reference for the deepwater drilling to meet the natural fracture stratum, improving the drilling efficiency and effectively reducing the risk of the deepwater natural fracture stratum.

The simulation device for the natural fracture formation breathing effect provided by the invention is described in detail below by combining specific embodiments.

The first embodiment is as follows:

referring to fig. 1 and 2, the embodiment provides a simulation apparatus for a natural fracture formation respiration effect, which includes a test piece and a liquid supply system, wherein an artificial fracture is disposed in the test piece, the artificial fracture extends from a first end face of the test piece to the inside of the test piece, but does not penetrate through the test piece, and the liquid supply system is used for supplying liquid into the artificial fracture; the test piece is arranged on the true triaxial testing machine, and pressure is provided by the true triaxial testing machine.

The test piece comprises a core and a seal sleeve 11, wherein the core is arranged in the seal sleeve 11; the rock core is a cube, an artificial crack is arranged in the cube, and the artificial crack extends from one end face of the rock core to the interior of the rock core but does not penetrate through the rock core.

The cement sealing sleeve 11 is arranged outside the core and used for sealing the end face of the core, the cement sealing sleeve 11 completely wraps the core, and a prefabricated hole is reserved in the center of the end face in contact with a core crack.

The test piece is externally provided with a true triaxial rigid servo testing machine for applying pressure to the test piece to simulate a stratum environment, the three stress directions are all rigid loads, and the loading blocks are respectively in close contact with the end face of the simulated stratum, specifically, the stress direction is sigma₁Directional pressurization simulates natural fracture opening pressure at σ₂Directional pressurization simulates formation confining pressure at σ₃Directional pressurization simulates formation pore pressure.

Sigma of true triaxial rigid servo testing machine₂The loading block in the direction is provided with a through hole, the aperture size of the loading block is consistent with the size of the prefabricated hole of the cement sealing sleeve 11, and the size of the loading block is matched with the size of the main pipeline, so that one end of the main pipeline is in direct contact with the prefabricated hole and the artificial crack core 12 through the through hole.

The two ends of the main pipeline are connected with a first liquid storage tank 8 and a second liquid storage tank 1 which are respectively used for providing simulated drilling fluid and recovering the simulated drilling fluid.

A hydraulic pump 6 is arranged on the liquid inlet branch to provide hydraulic pressure to simulate the flow of fluid in a shaft.

And a high-precision flowmeter 9 and a pressure gauge 4 are arranged on the main pipeline and are respectively used for measuring flow change and main pipeline pressure change.

Example two:

as shown in fig. 3, the present application provides a simulation method of natural fracture formation respiration effect, which mainly comprises the following steps:

step one, matching the initial pressure of a pressure regulating valve 5 and a backpressure valve 2 with the pressure of a shaft near a simulated stratum based on the parameters of the simulated natural fracture stratum;

step two, starting the true triaxial testing machine to pressurize the test piece at sigma₁Load applied in direction, matched to natural fracture cracking pressure, at σ₂Applying load in direction, matched with the confining pressure of the simulated formation, at σ₃Applying load in the direction to match the simulated formation pore pressure;

starting a hydraulic pump 6 to inject liquid until the readings of a pressure gauge 4 are not obviously changed, adjusting a pressure regulating valve 5, gradually increasing the hydraulic pressure in a main pipeline until the simulated wellbore pressure exceeds the simulated formation natural crack starting pressure, stopping pressure regulation at the moment, and recording the readings of a flowmeter 9 in real time until the readings of the flowmeter 9 are not obviously changed;

and step four, closing the hydraulic pump 6, opening a liquid outlet branch, and recording the real-time change of the readings of the flowmeter 9 until the readings of the flowmeter 9 are not obviously changed.

It should be noted that: in the third step, the hydraulic pressure is adjusted to exceed the opening pressure of the natural fracture of the simulated formation, the artificial fracture in the artificial fracture core 12 is propped open under the action of differential pressure, namely the width of the artificial fracture is increased, the simulated formation fluid in the corresponding main pipeline can leak into the fracture, and the simulation process corresponds to the opening process of the dynamic opening and closing process of the natural fracture formation and is also a drilling fluid leakage stage in the respiratory effect generation process; in the fourth step, as the backpressure valve 2 is matched with the pressure of the initial shaft, the pressure value of the liquid outlet branch is lower than the opening pressure of the natural crack, the originally propped crack is closed under the action of pressure difference, the lost simulated formation fluid can be regurgitated back into the liquid main pipeline, the simulation process corresponds to the closing process in the dynamic opening and closing process of the natural crack formation, and is a drilling fluid regurgitation stage in the respiratory effect generation process; the four steps are a complete respiratory effect simulation process.

In particular, the dynamic changes of the crack during the occurrence of the respiratory effect can be combined with the above-described figure 4.

In the simulation process of the respiratory effect, the change curve of the key parameters of the respiratory effect along with time can be obtained by recording the real-time change of the readings of the flowmeter 9: leak-off/regurgitation rate, cumulative leak-off.

Further, the above operation steps are repeated for researching the influence rule of different parameters on the respiratory effect, and the parameters are changed, so that a plurality of groups of experimental results are obtained, and the method comprises the following steps: further increasing the simulated wellbore pressure, and increasing the pressure difference between the simulated wellbore pressure and the natural fracture opening pressure in the fracture opening process so as to research the influence of the pressure difference on the fracture opening, the drilling fluid leakage and the return; changing sigma₁Directional loading to study the effect of different crack opening pressures on the breathing effect; changing sigma₂Sum of directions σ₃The load in the direction researches the influence of different pore pressures and formation confining pressure on the respiration effect; selecting rock cores of different materials to study the influence of different rock types on the respiration effect; and changing the properties of the simulated wellbore fluid to research the influence of the drilling fluid property on the breathing effect and the like.

The simulation device and the simulation method for the natural fracture formation respiration effect provided by the application are described in detail in a specific experimental scenario.

At the start of the test, the parts were mounted according to the connection relationship shown in fig. 1.

And debugging each part, and matching the initial pressure of the pressure regulating valve 5 and the backpressure valve 2 with the pressure of the shaft according to the shaft to be simulated and the condition of the natural fracture stratum after testing the normal functions of each part.

After the initial pressure is adjusted, starting a true triaxial testing machine to start loading a test piece, wherein a cement seal sleeve 11 is wrapped outside an artificial crack core 12, and a prefabricated hole is reserved in the center of the end face, in contact with the crack opening of the test piece, of the cement seal sleeve 11; true triaxial testing machine at sigma₁Load applied in direction, matched to natural fracture cracking pressure, at σ₂Directionally applying loads, matching formation confining pressureAt σ₃The load is applied in a direction matched with the formation pore pressure.

The first valve 7 is opened, the hydraulic pump 6 is started, and the simulated shaft fluid in the first liquid storage tank 8 passes through the true triaxial testing machine sigma through the main pipeline₁The through hole at the center of the loading block in the direction and the prefabricated hole on the cement sealing sleeve 11 are injected into the artificial crack of the artificial crack core 12.

And after the display result of the pressure gauge 4 is stable, adjusting the pressure regulating valve 5, gradually increasing the pressure in the main pipeline until the pressure in the main pipeline exceeds the opening pressure of the natural fractured formation, and recording the reading change of the high-precision flowmeter 9 until the reading of the high-precision flowmeter is not obviously changed, wherein the reading is the leakage stage simulation of the respiratory effect.

And (3) closing the hydraulic pump 6, opening the second valve 3, returning the drilling fluid to the fluid outlet branch under the action of pressure difference, and recording the indication change of the high-precision flowmeter 9 until the indication change is not obvious, wherein the phase is the simulation of the return phase of the respiratory effect.

The change rule of key parameters of the respiration effect, such as the drilling fluid leakage/return velocity, the drilling fluid accumulated leakage quantity and the like, along with time can be obtained through the recorded index change, and the above is a complete simulation of the respiration effect process of the natural fracture stratum.

And repeating the above steps for researching the influence rule of different parameters on the respiratory effect by changing the parameters to obtain a plurality of groups of experimental results, wherein the method comprises the following steps: further increasing the simulated wellbore pressure, and increasing the pressure difference between the simulated wellbore pressure and the natural fracture opening pressure in the fracture opening process so as to research the influence of the pressure difference on the fracture opening, the drilling fluid leakage and the return; changing sigma₁Directional loading to study the effect of different crack opening pressures on the breathing effect; changing sigma₂Sum of directions σ₃The load in the direction researches the influence of different pore pressures and formation confining pressure on the respiration effect; selecting rock cores of different materials to study the influence of different rock types on the respiration effect; and changing the properties of the simulated wellbore fluid to research the influence of the drilling fluid property on the breathing effect and the like.

The natural fracture stratum respiration effect simulation device is adopted and combined with the provided simulation method to simulate the natural fracture stratum respiration effect, the effects of stratum confining pressure, wellbore pressure, fracture opening pressure and the like can be considered, the process of the natural fracture stratum respiration effect is simulated and quantitatively represented, and the simulation of dynamic opening and closing of the natural fracture stratum can be realized, so that the simulation result is closer to the actual working condition, technical reference can be provided for a deepwater drilling tool to meet the natural fracture stratum, the generation of underground complex conditions such as kick and leakage is reduced, the drilling efficiency is effectively improved, the drilling cost is saved, and the drilling risk is reduced.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, and any reference signs in the claims are not intended to be construed as limiting the claim concerned.

The principle and the implementation mode of the present invention are explained by applying specific examples in the present specification, and the above descriptions of the examples are only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.