Comprehensive testing device and method for invasion of drilling fluid into hydrate reservoir under influence of mud cake

Abstract

The invention relates to the technical field of hydrate simulation testing, in particular to a comprehensive testing device and method for invasion of drilling fluid into a hydrate reservoir under the influence of a mud cake. Comprising a reservoir drilling fluid invasion module, a shaft drilling fluid circulation module and a mud cake module. The reservoir drilling fluid invasion module comprises a high-pressure barrel, and hydrate-containing sediments are contained in the high-pressure barrel; the shaft drilling fluid circulation module comprises a circulation kettle body, the reservoir drilling fluid invasion module is located on the outer side of the circulation kettle body, a circulation cavity is formed in the circulation kettle body, a mud cake module is embedded in the side wall of the circulation kettle body, and part of drilling fluid in the circulation cavity permeates into hydrate-containing sediment of the reservoir drilling fluid invasion module through the mud cake module. The simulation of the drilling fluid invasion process of the hydrate reservoir in the mud cake forming process is realized, the temperature-pressure-sound-electricity multi-parameter characterization of the dynamic response behavior of the invasion reservoir is realized, and the test requirement of analyzing the influence of mud cake forming on the process of invasion of the drilling fluid into the hydrate reservoir is met.

Description

Technical Field

[0001] This invention relates to the field of hydrate simulation testing technology, and in particular to a comprehensive testing device and method for drilling fluid intrusion into hydrate reservoirs under the influence of mud cake. Background Technology

[0002] Natural gas hydrates are ice-like, cage-like crystalline compounds formed from natural gas under high pressure and low temperature conditions. As a potential energy resource, they have attracted widespread attention due to their abundance and low environmental pollution. Driven by the needs of geological exploration and hydrate extraction, extensive drilling activities have been conducted globally to explore natural gas hydrate reservoirs. However, drilling into hydrate reservoirs still faces many challenges due to the engineering geological risks posed by drilling fluid invasion and hydrate dissociation. Among these challenges, clarifying the characteristics of drilling invasion and the dynamic response of the reservoir is fundamental and a prerequisite for achieving safe and efficient drilling in natural gas hydrate reservoirs.

[0003] Mud cake, formed by the solid deposition of invading drilling fluid, is crucial for drilling in hydrate reservoirs and for wellbore stability. On one hand, mud cake acts as a well sealant by reducing permeability, inhibiting drilling fluid intrusion and hydrate dissociation. On the other hand, the artificial wellbore formed by solid particles in the drilling fluid provides support resistance, preventing wellbore collapse and expansion caused by stress concentration. Furthermore, thicker filter cakes can lead to wellbore shrinkage and differential pressure adhesion, potentially causing pipe jamming, higher torque, pressure fluctuations, and other operational problems. Therefore, there is an urgent need to develop equipment suitable for addressing drilling fluid intrusion and the effects of mud cake in natural gas hydrate reservoirs, and to conduct research on the characteristics of drilling fluid intrusion in hydrate reservoirs under the influence of mud cake.

[0004] Currently, domestic scholars are simulating the drilling fluid invasion process in natural gas hydrate reservoirs by designing different devices, focusing on analyzing the drilling fluid invasion characteristics and reservoir dynamic response features. Patent CN202410988562.5 discloses a device and method for simulating drilling fluid invasion of hydrate reservoirs, focusing on testing the changes in reservoir mechanical properties before and after drilling fluid invasion; Patent CN202210398312.7 provides a device and method for evaluating the damage to natural gas hydrate reservoirs caused by drilling fluid invasion, which can comprehensively evaluate the damage caused by drilling fluid invasion to natural gas hydrate reservoirs; In addition, CN202310047570.5 and CN201910628749.3 respectively disclose test devices and methods for determining the hydrate decomposition characteristics after drilling fluid invasion of the reservoir, which can help to quickly determine the hydrate decomposition conditions and provide an effective method for analyzing the impact of hydrate decomposition on the drilling fluid invasion process; Patent CN202111602843.5 provides a natural gas hydrate drilling circulation simulation device and method, which can effectively simulate the dynamic process of deep-sea seabed natural gas hydrate drilling circulation. However, the aforementioned devices and methods do not consider the impact of the mud cake formation process on drilling fluid intrusion into natural gas hydrate reservoirs, resulting in a significant difference between the current simulation of drilling fluid intrusion into hydrate reservoirs and actual working conditions, which fails to meet the requirements for drilling risk control. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the existing technology and to propose a comprehensive testing device and method for drilling fluid invasion of hydrate reservoirs under the influence of mud cake. This invention realizes the simulation of the drilling fluid invasion process of hydrate reservoirs during mud cake formation, and achieves multi-parameter characterization of the dynamic response behavior of the invading reservoir using "temperature-pressure-sound-electricity" parameters, thus meeting the testing requirements for analyzing the impact of mud cake formation on the drilling fluid invasion process of hydrate reservoirs.

[0006] The technical solution of the present invention is: a comprehensive testing device for drilling fluid intrusion into hydrate reservoirs under the influence of mud cake, comprising a reservoir drilling fluid intrusion module, a wellbore drilling fluid circulation module, and a mud cake module; The reservoir drilling fluid invasion module includes a high-pressure cylinder containing hydrate-bearing sediments. The wellbore drilling fluid circulation module includes a circulation vessel, a reservoir drilling fluid intrusion module located outside the circulation vessel, a circulation chamber inside the circulation vessel, and a mud cake module embedded in the side wall of the circulation vessel. Part of the drilling fluid in the circulation chamber seeps into the hydrate-bearing sediment of the reservoir drilling fluid intrusion module through the mud cake module.

[0007] In this application, the circulating vessel body is cylindrical; The two symmetrical outer sides of the circulating vessel are respectively provided with reservoir drilling fluid intrusion modules. The reservoir drilling fluid intrusion modules are arranged in a long strip shape and extend outward along the radial direction of the circulating vessel. Correspondingly, mud cake modules are provided on the symmetrical two side walls where the circulating vessel comes into contact with the hydrate-containing sediment.

[0008] The multi-layered nested mud cake module includes a porous sintered plate, a mud cake layer, a seepage plate, and a flow guide plate arranged sequentially from the inside out. The mud cake layer includes several layers of mud cake arranged in a vertical direction, and a filling medium located between two adjacent layers of mud cake; A loading block is provided above the porous sintering plate, the seepage plate and the guide plate respectively, and a hydraulic body is provided above the mud cake layer. A rubber sleeve is provided between the hydraulic body and the loading block and the mud cake layer. Loading blocks are provided below the porous sintering plate, the seepage plate and the guide plate respectively, a pressing block is provided below the mud cake layer, a hydraulic body is provided below the pressing block, and a rubber sleeve is provided between the hydraulic body and the loading block and the pressing block.

[0009] The wellbore drilling fluid circulation module also includes: The vessel body pressing blocks are located above and below the mud cake module, respectively. Each vessel body pressing block is equipped with a hydraulic channel, through which the confining pressure fluid is injected into the hydraulic body. The upper end cover is located above the vessel body pressing block above the mud cake module; The lower end cover is located below the vessel body pressing block below the mud cake module; The low-temperature water bath is connected to the drilling fluid flow channel of the upper end cover, and the drilling fluid flow channel of the lower end cover is connected to the low-temperature water bath. The drilling fluid forms a circulation flow in the circulation chamber and the low-temperature water bath.

[0010] A high-pressure pump, a first thermometer, a first pressure gauge, a first valve, and a first flow meter are sequentially installed on the connecting pipe between the low-temperature water bath and the upper cover; The connecting pipe between the lower end cover and the low-temperature water bath is equipped with a first back pressure valve, a second flow meter, and a second thermometer in sequence.

[0011] The high-pressure cylinder of the reservoir drilling fluid intrusion module is cylindrical, with one end connected to the circulation vessel and the other end equipped with a plug. The annular outer surface of the high-pressure cylinder is covered with a low-temperature coating layer, which is connected to the temperature control module. A fluid outlet is provided at the blockage plate, and the fluid outlet is connected to the separation and collection module; The high-pressure cylinder is equipped with a gas interface, which is connected to the gas supply module. Several integrated temperature and pressure probes are equidistantly spaced along the axial direction on the high-pressure cylinder. The high-pressure cylinder is equipped with pairs of ultrasonic transmitting probes and ultrasonic receiving probes. Several ultrasonic transmitting probes are located on the side wall of the high-pressure cylinder, and ultrasonic receiving probes are located on the side wall of the high-pressure cylinder opposite to the ultrasonic transmitting probes. Several complex resistance probes are also spaced apart on the side wall of the high-pressure cylinder; The temperature and pressure integrated probe, ultrasonic transmitting probe, ultrasonic receiving probe, and complex resistance probe are electrically connected to the data processing module.

[0012] This application also discloses a method for testing drilling fluid intrusion into hydrate reservoirs under the influence of the aforementioned mud cake using a comprehensive testing device, comprising the following steps: S1. Connection and airtightness test of the device; S2, Sediment Loading: S3. Synthesis and monitoring of hydrates: Methane gas is injected into the high-pressure cylinder to cool it to the target temperature and keep it constant. Hydrates are generated in the high-pressure cylinder through a reaction. During the hydrate formation process, the physical properties of the hydrate deposits are monitored in real time. S4. Simulation of drilling fluid invasion process in hydrate reservoirs: The drilling fluid is delivered to the circulation chamber. Under the action of pressure difference, part of the drilling fluid entering the circulation chamber seeps into the hydrate-containing sediment through the mud cake module. The remaining drilling fluid is circulated to the low-temperature water bath under the action of injection pressure. S5. Analysis of the impact of mud cake on drilling fluid intrusion.

[0013] In step S3, during the formation of hydrates, temperature, pressure, acoustic wave and resistance data of hydrate-containing sediments are obtained by using a temperature and pressure integrated probe, an ultrasonic transmitting probe, an ultrasonic receiving probe and a complex resistance probe, respectively. The physical properties of the hydrate-containing sediments are monitored in real time to determine the hydrate synthesis status.

[0014] In step S4, during the process of drilling fluid intrusion into hydrate-bearing deposits, the temperature and pressure characteristics of the hydrate-bearing deposits during the drilling fluid intrusion process are obtained by using a temperature and pressure integrated probe, the acoustic characteristics of the hydrate-bearing deposits during the drilling fluid intrusion process are obtained by using an ultrasonic transmitting probe, and the electrical characteristics of the hydrate-bearing deposits during the drilling fluid intrusion process are obtained by using a complex resistance probe, thereby determining the degree of drilling fluid intrusion and hydrate decomposition characteristics.

[0015] In step S5, the solid particles of the mud cake are changed to simulate the effect of different mud cakes on the drilling fluid invasion process. By applying confining pressure to the mud cake layer using briquettes and rubber sleeves, different confining pressure fluids are injected into the hydraulic body through hydraulic channels. By controlling the confining pressure fluid, the loading confining pressure of the mud cake layer is changed, simulating the effect of mud cakes with different compaction degrees on the drilling fluid invasion process. By changing the type of filling medium, the influence of different filling layers on the drilling fluid invasion process can be simulated.

[0016] The beneficial effects of this invention are: (1) This application realizes the process of drilling fluid infiltrating into hydrate-bearing sediments by setting up a multi-layer nested mud cake module, and sets hydraulic bodies on the upper and lower sides of the mud cake layer to compact the mud cake. It proposes a comprehensive testing device for the influence of mud cake under different compaction states on the drilling fluid intrusion characteristics of hydrate reservoirs, which makes up for the shortcomings of existing equipment that ignores the influence of mud cake formation, and specifically solves the problem of inaccurate characterization of the drilling fluid intrusion process of hydrate reservoirs under the influence of mud cake. (2) By setting up a reservoir drilling fluid invasion module and a wellbore drilling fluid circulation module, this application combines the wellbore drilling fluid circulation process and the reservoir drilling fluid invasion process, realizing the analysis of the wellbore-reservoir coupling mechanism of the drilling fluid invasion process, overcoming the shortcomings of existing devices that only consider the drilling fluid invasion characteristics of hydrate reservoirs, and improving the accuracy of indoor simulation experiments. (3) This application uses temperature-pressure detection, ultrasonic testing and complex resistance testing of hydrate-bearing sediments to form a multi-parameter integrated characterization method for drilling fluid invasion characteristics of hydrate reservoirs. It can realize the fine characterization of drilling fluid invasion process of hydrate reservoirs, especially the identification and characterization of drilling fluid invasion area and hydrate decomposition area. It can also conduct in-depth research on the influence mechanism of hydrate phase change and drilling fluid invasion on hydrate reservoirs.

[0017] In summary, this application realizes the simulation of drilling fluid invasion into hydrate reservoirs during mud cake formation, and achieves multi-parameter characterization of the dynamic response behavior of the invading reservoir using temperature, pressure, acoustics, and electricity. This meets the testing requirements for analyzing the impact of mud cake formation on the drilling fluid invasion process into hydrate reservoirs, and provides an experimental basis for the control of engineering geological risks caused by drilling in marine hydrate reservoirs and for safe and efficient drilling. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main structure of the testing device described in this invention; Figure 2 This is a top view of the testing device described in this invention; Figure 3 This is a structural diagram of the mud cake module; Figure 4 A schematic diagram of the data processing module.

[0019] In the diagram: 11 High-pressure cylinder; 12 Low-temperature coating layer; 13 Hydrate-containing sediment; 14 Gas interface; 15 Outlet filter plate; 16 Blocking plate; 17 Fluid outlet; 18 Integrated temperature and pressure probe; 19 Ultrasonic transmitting probe; 110 Ultrasonic receiving probe; 111 Complex resistance probe; 21 Circulating vessel; 22 Circulating chamber; 23 Vessel pressure block; 24 Upper end cover; 25 Lower end cover; 26 Drilling fluid flow channel; 27 Low-temperature water bath; 28 High-pressure pump; 29 First thermometer; 210 First pressure gauge; 211 First valve; 212 First flow meter; 213 Injection interface; 214 Pipeline interface; 215 First back pressure valve; 216 Second flow meter; 217 Second thermometer. 31 Porous sintered plate; 32 Mud cake; 33 Permeation plate; 34 Guide plate; 35 Filling medium; 36 Press block; 37 Rubber sleeve; 38 Hydraulic body; 39 Hydraulic channel; 310 Loading block; 41 Gas cylinder; 42 Second valve; 43 Third flow meter; 44 Fourth pressure gauge; 45 Third valve; 51 Refrigeration circulator; 52 Fourth valve; 53 Third thermometer; 54 Fourth pressure gauge; 55 Refrigerant inlet; 56 Refrigerant outlet; 61 Collection tank; 62 Second back pressure valve; 63 Filter; 64 Fifth valve; 71 Computer; 72 Data processor; 73 Complex impedance analyzer; 74 Temperature data processing terminal; 75 Pressure data processing terminal; 76 Ultrasonic data processing terminal. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] like Figure 1 As shown, the comprehensive testing device for drilling fluid invasion of hydrate reservoirs under the influence of mud cake according to the present invention includes a reservoir drilling fluid invasion module, a wellbore drilling fluid circulation module, a mud cake module, an air supply module, a temperature control module, a separation and collection module, and a data processing module. The reservoir drilling fluid invasion module is located outside the wellbore drilling fluid circulation module, and the mud cake module is located inside the wellbore drilling fluid circulation module at the intersection of the wellbore drilling fluid circulation module and the reservoir drilling fluid invasion module. The air supply module, temperature control module, and separation and collection module are respectively connected to the reservoir drilling fluid invasion module. The data processing module is connected to the reservoir drilling fluid invasion module, the wellbore drilling fluid circulation module, the mud cake module, the air supply module, the temperature control module, and the separation and collection module.

[0023] In-situ synthesis of hydrate-bearing sediments was performed within the reservoir drilling fluid invasion module. The mud cake module was able to simulate the characteristics of drilling fluid invasion in hydrate sediments under the influence of mud cake, obtain drilling fluid invasion parameters and reservoir physical properties such as temperature, pressure, acoustic waves, and electrical resistance, and compare the influence of mud cake state on the drilling fluid invasion process, supporting the study of the drilling fluid invasion mechanism in hydrate reservoirs during mud cake formation.

[0024] The wellbore drilling fluid circulation module includes a cylindrical circulation vessel 21, within which a vertically oriented cylindrical circulation chamber 22 is provided. A reservoir drilling fluid intrusion module is located on the outer side of the circulation vessel 21. Mud cake modules are embedded in the side walls of the circulation vessel 21, enabling communication between the circulation chamber 22 and the outer reservoir drilling fluid intrusion module. In this embodiment, mud cake modules are embedded in the two symmetrically arranged side walls of the circulation vessel 21, allowing the drilling fluid in the circulation chamber 22 to infiltrate into the reservoir drilling fluid intrusion module through the two symmetrically arranged mud cake modules.

[0025] The circulating vessel body 21 also includes vessel pressing blocks 23 located above and below the mud cake module, respectively. Each pressing block 23 has a through hole at its center. The through hole in the center of the pressing block 23, the inner wall of the circulating vessel body 21, and the inner wall of the mud cake module together form a circulating cavity 22. An upper end cover 24 is provided on the top of the circulating vessel body 21, positioned above the pressing block above the mud cake module. A lower end cover 25 is provided on the bottom of the circulating vessel body 21, positioned below the pressing block below the mud cake module. The upper and lower end covers 24 and 25 enable sealing of the circulating vessel body and fixation of the mud cake module. A through drilling fluid flow channel 26 is provided at the center of each of the upper and lower end covers 24 and 25, communicating with the circulating cavity 22. A connection interface 213 is provided on the outside of the drilling fluid flow channel 26, enabling connection to a high-pressure pipeline.

[0026] The wellbore drilling fluid circulation module also includes a low-temperature water bath 27, which is connected to the drilling fluid flow channel 26 on the upper end cover 24 and injects the fluid into the circulation chamber 22 of the circulation vessel 21. A first high-pressure pump 28, a first thermometer 29, a first pressure gauge 210, a first valve 211, and a first flow meter 212 are sequentially installed on the connecting pipe between the low-temperature water bath 27 and the drilling fluid flow channel on the upper end cover. The first high-pressure pump 28 pressurizes the drilling fluid, while the first thermometer 29, first pressure gauge 210, and first flow meter 212 respectively monitor the temperature, pressure, and flow rate of the drilling fluid injected into the circulation chamber 22 in real time. Based on the temperature changes obtained by the first thermometer 29, the temperature of the drilling fluid in the circulation chamber 22 can be controlled by changing the set temperature of the low-temperature water bath 27.

[0027] After the drilling fluid flows into the circulation chamber 22, some of the drilling fluid enters the reservoir drilling fluid invasion module under the action of pressure difference, while the rest of the drilling fluid flows out from the drilling flow channel 26 of the lower end cap under the action of injection pressure.

[0028] The drilling fluid flow channel 26 of the lower end cap is connected to the low-temperature water bath 27, allowing the drilling fluid to flow back into the low-temperature water bath 27, thus realizing the circulation of drilling fluid between the circulation chamber 22 and the low-temperature water bath 27. The connecting pipe between the connection interface 213 at the drilling fluid flow channel of the lower end cap and the low-temperature water bath 27 is sequentially equipped with a pipeline interface 214, a first back pressure valve 215, a second flow meter 216, and a second thermometer 217. Through the second flow meter 216 and the second thermometer 217, real-time detection of the flow rate and temperature of the drilling fluid flowing back into the low-temperature water bath 27 is achieved.

[0029] The contact surfaces of the upper end cover 24 and the upper end face of the circulating vessel 21, and the contact surfaces of the lower end cover 25 and the lower end face of the circulating vessel 21, all require certain treatment and the addition of sealing rings or gaskets to ensure the sealing of the circulating chamber 22. A suitable amount of lubricant can be applied during installation. Sealing rings and gas pressure head accessories can be added as needed at the connection points 213 on the outer sides of the upper end cover 24 and the lower end cover 25 where they connect to the high-pressure pipeline.

[0030] The drilling fluid used in this application can be formulated with reference to the drilling fluid used in actual hydrate reservoir drilling, or a fluid containing a certain amount of solid particles can be used instead.

[0031] In this application, the mud cake module is embedded in the side wall of the circulating vessel 21. Through the mud cake module, the drilling fluid in the circulating chamber 22 can penetrate into the external reservoir drilling fluid, which then enters the module. Figure 2 As shown, the mud cake module, from the inside out (from the circulation chamber 22 to the hydrate-bearing sediment 13), includes a porous sintered plate 31, a mud cake layer, a permeation plate 33, and a flow guide plate 34. The structure of this mud cake module simulates the process of drilling fluid infiltrating the hydrate reservoir through the mud cake. The porous sintered plate 31 serves to guide and stabilize the flow, allowing the drilling fluid to flow into the hydrate-bearing sediment 13 in a stable permeation manner. The permeation plate 33 evenly distributes the flow rate of the liquid flowing out of the mud cake layer, ensuring a uniform vertical distribution of the drilling fluid. The flow guide plate 34 has evenly distributed perforations, which, while further ensuring a stable outflow of drilling fluid, also separate the permeation plate 33 from the hydrate-bearing sediment 13, preventing backflow of the liquid within the hydrate-bearing sediment 13.

[0032] The mud cake layer comprises several layers of mud cakes 32 arranged vertically in sequence, and a filling medium layer 35 located between adjacent mud cake layers. Through the structural design of this mud cake layer, the effects of the presence and absence of mud cakes on the drilling fluid invasion process can be compared, as well as the effects of different filling media on the drilling fluid invasion process can be compared. In this embodiment, the filling medium layer 35 can be made of materials such as coated sand, quartz sand, or ceramsite, and its particle size can be determined based on the target reservoir characteristics and filling technology.

[0033] A pressure block 36 is provided below the mud cake layer, and the pressure block 36 is in direct contact with the bottom of the mud cake layer. Loading blocks 310 are provided below the porous sintering plate 31, the permeation plate 33, and the guide plate 34, respectively. Rubber sleeves 37 are provided below the pressure block 36 and the loading blocks 310. A gap is formed between the loading blocks below the porous sintering plate and the loading blocks below the permeation plate and the guide plate. A hydraulic body 38 is provided below the pressure block 36, and the pressure block 36 and the hydraulic body 38 are located within this gap. The hydraulic body 38 is separated from the pressure block 36 and the loading blocks by the rubber sleeve 37. The confining fluid in the hydraulic body 38 will not directly contact the mud cake layer, the porous sintering plate 31, the permeation plate 33, and the guide plate 34; therefore, the rubber sleeve 37 provides a sealing function.

[0034] The hydraulic body 38 is connected to the hydraulic channel 39 inside the pressure block of the vessel body below the cake module. The external confining fluid enters the hydraulic body 38 through the hydraulic channel 39, and the pressure of the confining fluid is transmitted to the cake layer in sequence through the rubber sleeve 37 and the pressure block 36.

[0035] A loading block is provided above the porous sintering plate 31, the permeation plate 33 and the flow guide plate 34. A gap is formed between the loading block above the porous sintering plate and the loading blocks above the permeation plate and the flow guide plate. The hydraulic body above the mud cake layer is located in the gap, and a rubber sleeve is provided between the hydraulic body and the loading block and the mud cake layer.

[0036] Hydraulic bodies 38 located above and below the mud cake layer can apply a certain confining pressure to the mud cake 32 and the filling medium 35, thereby compacting the mud cake layer. Furthermore, by changing the pressure value of the confining fluid, the degree of compaction of the mud cake layer can be changed, thus reflecting the compaction characteristics of the mud cake and the filling medium under different stress states.

[0037] The reservoir drilling fluid invasion module includes a high-pressure cylinder 11. In this embodiment, the high-pressure cylinder 11 is symmetrically arranged on both outer sides of the circulation vessel 21. The high-pressure cylinder 11 is elongated and extends radially along the circulation vessel 21. The high-pressure cylinder 11 is cylindrical, with one axial end connected to the outer wall of the circulation vessel 21, and the other axial end provided with a blocking plate 16, thereby forming a closed cavity inside the high-pressure cylinder 11. The cavity of the high-pressure cylinder 11 contains hydrate-bearing deposits, enabling comparative analysis of drilling fluid invasion characteristics under different conditions.

[0038] A cryogenic coating layer 12 is applied to the annular outer surface of the high-pressure cylinder 11 and is connected to a temperature control module. The cryogenic coating layer 12 provides the necessary temperature conditions for the preparation of hydrate-containing deposits within the high-pressure cylinder 11. A sealing connection is established between the plug plate 16 and the inner wall of the high-pressure cylinder 11. A fluid outlet 17 is provided on the plug plate 16 and is connected to a separation and collection module. An outlet filter plate 15 is installed between the inner surface of the plug plate 16 and the hydrate-containing deposits within the high-pressure cylinder 11. The outlet filter plate 15 filters the liquid flowing out of the high-pressure cylinder 11, preventing the liquid from carrying solid substances out.

[0039] In this embodiment, several integrated temperature and pressure probes 18 are equidistantly arranged along the axial direction on the outer surface of the high-pressure cylinder 11. These probes acquire real-time changes in pore pressure and temperature at specific points in the hydrate-bearing deposit during the experiment. Data obtained from the integrated temperature and pressure probes 18 allows for the determination of the drilling fluid invasion location and rate, which is then adjusted by the high-pressure pump 28. Several ultrasonic transmitting probes 19 and ultrasonic receiving probes 110 are also spaced apart on the outer surface of the high-pressure cylinder 11. These probes are positioned opposite each other, with the ultrasonic transmitting probe 19 located on one side of the high-pressure cylinder 11 and the ultrasonic receiving probe 110 on the opposite side. The ultrasonic transmitting probes 19 and 110 enable acoustic characteristic testing of the hydrate-bearing deposit during drilling fluid invasion. Several complex resistance probes 111 are also spaced apart on the side of the high-pressure cylinder 11. These probes are used to test the electrical characteristics of the hydrate-bearing deposit during drilling fluid invasion.

[0040] Protective sleeves are provided at the connection points of the ultrasonic transmitting probe 19 and the high-pressure cylinder 11, and at the connection points of the ultrasonic receiving probe 110 and the high-pressure cylinder 11, respectively, to fix the probes and assist in testing. A bushing is provided at the connection point of the integrated temperature and pressure probe 18 and the high-pressure cylinder 11 to fix the integrated temperature and pressure probe.

[0041] The high-pressure cylinder 11 is also equipped with a gas interface 14, which is connected to the gas supply module.

[0042] In this application, the framework material for generating hydrates can be sediments such as quartz sand and clay, the gas used for preparation can be gases such as methane, ethane, and carbon dioxide, and promoters such as sodium dodecyl sulfate (SDS) can be reasonably selected to accelerate the synthesis of hydrates.

[0043] The temperature control module is connected to the cryogenic coating layer 12 and provides the temperature conditions required for hydrate synthesis and drilling fluid invasion experiments. The temperature control module includes a refrigeration circulator 51. The cryogenic coating layer 12 has a refrigerant inlet 55 and a refrigerant outlet 56. A fourth valve 52, a third thermometer 53, and a fourth pressure gauge 64 are sequentially installed on the connecting pipe between the refrigeration circulator 51 and the refrigerant inlet 55. After the refrigerant in the refrigeration circulator 51 flows into the cryogenic coating layer 12, it provides the necessary low-temperature conditions for the high-pressure cylinder 11. After being cooled within the cryogenic coating layer 12, the refrigerant flows back to the refrigeration circulator 51 through the refrigerant outlet 56, achieving a continuous circulation of the refrigerant between the cryogenic coating layer 12 and the refrigeration circulator 51, providing continuous cooling for the reservoir drilling fluid invasion module. Under the control of the module, the reservoir drilling fluid invasion module is maintained at a constant low temperature, which is beneficial for hydrate formation and drilling fluid invasion experiments.

[0044] By monitoring the changes in temperature and pressure of the integrated temperature and pressure probe 18 and the third thermometer 53, the set temperature of the refrigeration cycler 51 can be adjusted, thereby changing the temperature of the low-temperature coating layer 12 and providing suitable low-temperature conditions for the hydrate-containing deposit 13. The refrigerant used in this application can be made from ethylene glycol or similar substances in a specific ratio, as long as it meets the requirements for long-cycle refrigeration.

[0045] The separation and collection module is connected to the fluid outlet 17 and can collect and treat the discharged drilling fluid. The separation and collection module includes a collection tank 61. A filter 63, a back pressure valve 62, and a fifth valve 64 are sequentially installed on the connecting pipeline between the fluid outlet 17 and the collection tank 61. The fluid discharged from the hydrate-bearing sediment 13 is filtered by the filter 63, and then, under the control of the back pressure valve 62, the drilling fluid in the fluid flows into the collection tank 61 driven by the pressure difference. Gas in the fluid is discharged through the fifth valve 64, thus achieving the separation and collection of the fluid discharged from the hydrate-bearing sediment.

[0046] The gas supply module is connected to the gas interface 14 and is mainly used to provide the gas source required for hydrate synthesis. The gas supply module includes a gas cylinder 41. A second valve 42, a third flow meter 43, and a third pressure gauge 44 are sequentially installed on the connecting pipeline between the gas cylinder 41 and the gas interface 14. High-pressure gas from the gas cylinder 41 is injected into the high-pressure cylinder 11 through the connecting pipeline. A third valve 45 is also installed at the gas interface 14, which controls the discharge of excess gas.

[0047] The data processing module includes a computer 71, a data processor 72, and a complex impedance analyzer 73. The data processor 72 and the complex impedance analyzer 73 are connected to the computer 71. The data processor 72 is sequentially connected to a temperature data processing terminal 74, a pressure data processing terminal 75, and an ultrasonic data processing terminal 76. The temperature data processing terminal 74 and the pressure data processing terminal 75 are electrically connected to an integrated temperature and pressure probe 18. The ultrasonic data processing terminal 76 is connected to an ultrasonic transmitting probe 19 and an ultrasonic receiving probe 110, enabling real-time monitoring and recording of the temperature, pressure, and acoustic parameters of the hydrate-bearing sediment during the experiment. The complex impedance analyzer 73 is electrically connected to a complex resistance probe 111, enabling real-time monitoring of the changes in the complex impedance of the hydrate-bearing sediment 13 during drilling fluid intrusion.

[0048] The high-pressure cylinder 11 and the circulating vessel 21 are made of titanium alloy or aluminum alloy. The outer surface of the high-pressure cylinder 11 is treated to ensure a tight fit with the low-temperature coating layer 13 and improve heat transfer efficiency.

[0049] This application also discloses a method for testing drilling fluid intrusion into hydrate reservoirs under the influence of the aforementioned mud cake using a comprehensive testing device, comprising the following steps.

[0050] The first step is to connect and test the device.

[0051] The porous sintering plate 31, mud cake 32, filling medium 35, permeation plate 33, and guide plate 34 are embedded into the circulating vessel body 21 and pressed and fixed with the vessel body pressure block 23.

[0052] Connect the entire device, perform an airtightness check, and analyze and determine the sealing performance of the wellbore drilling fluid circulation module and the reservoir drilling fluid intrusion module.

[0053] The second step is sediment loading.

[0054] The sediment is thoroughly mixed with a certain amount of deionized water, placed inside the high-pressure cylinder 11, and fully compacted. The amount of deionized water used is calculated based on the target hydrate saturation and sediment porosity. An outlet filter plate 15 is installed at the end of the high-pressure cylinder 11, and a plug plate 16 is added to complete the sediment filling.

[0055] The third step is the synthesis and monitoring of hydrates.

[0056] Methane gas is injected into the high-pressure cylinder 11 through the gas supply module until the target pressure is reached inside the high-pressure cylinder. The initial temperature of the refrigeration circulator 51 is set and refrigerant is injected into the low-temperature wrapping layer 12 so that the refrigerant reaches the target temperature and remains constant. Hydrates are generated inside the high-pressure cylinder 11, forming hydrate-containing deposits 13.

[0057] During the formation of hydrates, temperature, pressure, sound wave and resistance data of hydrate-containing sediments are obtained by a temperature and pressure integrated probe 18, an ultrasonic transmitting probe 19, an ultrasonic receiving probe 110 and a complex resistance probe 111, respectively. The physical properties of hydrate-containing sediments 13 are monitored in real time to determine the hydrate synthesis status.

[0058] The fourth step is to simulate the drilling fluid invasion process in hydrate reservoirs.

[0059] The initial temperature of the low-temperature water bath 27 is set, and the pump pressure and flow rate of the high-pressure pump 28 are adjusted to deliver drilling fluid into the circulation chamber 22. Part of the drilling fluid entering the circulation chamber 22, under the action of pressure difference, seeps into the hydrate-bearing sediment through the mud cake module; the remaining drilling fluid, driven by the injection pressure, flows back into the low-temperature water bath 27 through the drilling fluid flow channel of the lower end cap.

[0060] During the process of partial drilling fluid infiltrating into the hydrate-bearing sediment, it sequentially passes through the porous sintered plate 31, mud cake 32, filling medium 35, permeation plate 33, and guide plate 34 into the interior of the hydrate-bearing sediment 13. The pressure of the first backpressure valve 215 is set to simulate the process of drilling fluid infiltrating the hydrate reservoir at different pressures during drilling. Based on the difference between the first flow meter 212 and the second flow meter 216, the intrusion volume and velocity of the drilling fluid can be determined. The temperature of the drilling fluid in the low-temperature water bath 27 can be continuously adjusted by the reading of the first thermometer 29.

[0061] Drilling fluid seeps from the center of the wellbore drilling fluid circulation module into the hydrate-bearing sediment 13 of the module, and continuously diffuses within the hydrate-bearing sediment 13 before finally flowing into the separation and collection module. The separation and collection module achieves the separation and collection of gas and liquid.

[0062] The pressure value of the second back pressure valve 62 is set. When the drilling fluid that has invaded the hydrate-bearing sediment 13 flows and diffuses to the side of the high-pressure cylinder 11, it flows into the separation and collection module through the outlet filter plate 15, the plug 16, and the fluid outlet 17. The liquid and gas are separated by the filter 63 and the second back pressure valve 62 of the separation and collection module. The liquid obtained after separation enters the collection tank 61, and the gas after separation is discharged through the fifth valve 64.

[0063] The process of drilling fluid invading hydrate-bearing deposits is analyzed by using a thermo-barometric probe 18 to obtain the thermo-barometric characteristics of the hydrate-bearing deposits during the drilling fluid invading process, an ultrasonic transmitting probe 19 to obtain the acoustic characteristics of the hydrate-bearing deposits during the drilling fluid invading process, and a complex resistance probe 111 to obtain the electrical characteristics of the hydrate-bearing deposits during the drilling fluid invading process. This allows for the determination of the degree of drilling fluid invading and the characteristics of hydrate decomposition.

[0064] Ultrasonic longitudinal wave velocity The calculation formula is: , Where L represents the distance between the ultrasonic transmitting probe and the ultrasonic receiving probe; Indicates the reception time of the longitudinal wave of the ultrasonic wave; This indicates the inherent propagation time of the longitudinal wave of an ultrasonic wave.

[0065] Ultrasonic longitudinal wave velocity The calculation formula is: , in, Indicates the reception time of the ultrasonic transverse wave; This indicates the inherent propagation time of the ultrasonic transverse wave.

[0066] Complex resistivity The calculation formula is: , Where Z represents the complex impedance; L represents the distance between two adjacent complex impedance probes; and S represents the area of ​​the complex impedance probe.

[0067] Step 5: Analysis of the impact of mud cake on drilling fluid intrusion.

[0068] By changing the solid particles of mud cake 32, the influence of different mud cakes on the drilling fluid invasion process was simulated.

[0069] The mud cake layer is subjected to confining pressure by the pressure block 36 and the rubber sleeve 37. Different confining pressure fluids are injected into the hydraulic body 38 through the hydraulic channel 39. By controlling the confining pressure fluid, the loading confining pressure of the mud cake layer is changed, simulating the effect of mud cakes with different compaction degrees on the drilling fluid invasion process.

[0070] By changing the type of filling medium 35, the influence of different filling layers on the drilling fluid invasion process was simulated.

[0071] In this application, a multi-layer nested mud cake module consisting of a porous sintered plate 31, a mud cake 32, a filling medium 35, a permeation plate 33, and a flow guide plate 34 is used to characterize the intrusion characteristics of drilling fluid on hydrate-bearing sediments 13 under different conditions, and to compare the changes in the acoustic, electrical, and thermo-baric properties of the hydrate-bearing sediments.

[0072] In this application, the characteristics of the porous sintered plate 31 can also be changed to study the influence of initial permeability and mud cake formation on drilling fluid invasion characteristics.

[0073] Step 6: End the experiment and clean up the equipment.

[0074] Shut down the gas supply module and temperature control module, drain the drilling fluid from the circulation chamber 22 and the fluid inside the hydrate-containing sediment 13, disassemble the entire device and organize the relevant components.

[0075] The above provides a detailed description of the comprehensive testing device and method for drilling fluid intrusion into hydrate reservoirs under the influence of mud cake, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A comprehensive testing device for drilling fluid invasion into a hydrate reservoir under the influence of mud cake, characterized in that, The reservoir drilling fluid invasion module, the wellbore drilling fluid circulation module, and the mud cake module are included. The reservoir drilling fluid invasion module includes a high-pressure cylinder, and the high-pressure cylinder contains hydrate deposits. The wellbore drilling fluid circulation module includes a circulation kettle, the reservoir drilling fluid invasion module is located outside the circulation kettle, a circulation cavity is arranged in the circulation kettle, a mud cake module is embedded in the side wall of the circulation kettle, and part of the drilling fluid in the circulation cavity penetrates into the hydrate deposits of the reservoir drilling fluid invasion module through the mud cake module.

2. The mud cake effect on drilling fluid invasion into hydrate reservoirs integrated testing device according to claim 1, characterized in that, The circulation kettle is in a cylindrical shape. Symmetrical reservoir drilling fluid invasion modules are arranged on the two outer sides of the circulation kettle, and the reservoir drilling fluid invasion modules are arranged in a strip shape and extend outward along the radial direction of the circulation kettle. Correspondingly, mud cake modules are arranged on the symmetrical side walls of the circulation kettle in contact with the hydrate deposits.

3. The mud cake effect on drilling fluid invasion into hydrate reservoirs integrated testing device of claim 1, wherein, The multi-layer nested mud cake module includes a porous sintered plate, a mud cake layer, a seepage plate, and a flow guide plate arranged from inside to outside. The mud cake layer includes a plurality of mud cakes arranged in a vertical direction and a filling medium arranged between adjacent two mud cakes. Loading blocks are arranged above the porous sintered plate, the seepage plate, and the flow guide plate, a hydraulic body is arranged above the mud cake layer, and a rubber sleeve is arranged between the loading blocks, the mud cake layer, and the hydraulic body. Loading blocks are arranged below the porous sintered plate, the seepage plate, and the flow guide plate, a pressing block is arranged below the mud cake layer, a hydraulic body is arranged below the pressing block, and a rubber sleeve is arranged between the loading blocks, the pressing block, and the hydraulic body.

4. The mud cake effect on drilling fluid invasion into hydrate reservoirs integrated test device of claim 1, wherein, The wellbore drilling fluid circulation module further includes: Kettle pressing blocks arranged above and below the mud cake module, hydraulic channels are arranged in the kettle pressing blocks, and confining fluid is injected into the hydraulic body through the hydraulic channels; An upper end cover arranged above the circulation kettle and above the kettle pressing block above the mud cake module; A lower end cover arranged below the circulation kettle and below the kettle pressing block below the mud cake module; A low-temperature water bath connected to the drilling fluid flow channel of the upper end cover and connected to the drilling fluid flow channel of the lower end cover, and the drilling fluid forms a circulating flow in the circulation cavity and the low-temperature water bath.

5. The mud cake-affected drilling fluid invasion hydrate reservoir comprehensive testing device according to claim 4, wherein A high-pressure pump, a first thermometer, a first pressure gauge, a first valve, and a first flow meter are sequentially arranged on the connecting pipeline between the low-temperature water bath and the upper end cover; A first back pressure valve, a second flow meter, and a second thermometer are sequentially arranged on the connecting pipeline between the lower end cover and the low-temperature water bath.

6. The mud cake effect on drilling fluid invasion into hydrate reservoirs integrated test device of claim 1, wherein, The high-pressure cylinder of the reservoir drilling fluid invasion module is in a cylindrical shape, one end of the high-pressure cylinder is connected to the circulation kettle, and the other end of the high-pressure cylinder is provided with a blanking plate; An annular outer surface of the high-pressure cylinder is wrapped with a low-temperature wrapping layer, and the low-temperature wrapping layer is connected to a temperature control module; A fluid outlet is arranged at the blanking plate, and the fluid outlet is connected to a separation and collection module; A gas interface is arranged at the high-pressure cylinder, and the gas interface is connected to a gas supply module; A plurality of temperature and pressure integrated probes are arranged at the high-pressure cylinder at equal intervals along the axial direction. The high-pressure cylinder is provided with a pair of ultrasonic wave transmitting probes and ultrasonic wave receiving probes, the ultrasonic wave transmitting probe is arranged at the side wall of the high-pressure cylinder, and the ultrasonic wave receiving probe is arranged at the side wall of the high-pressure cylinder opposite to the ultrasonic wave transmitting probe; A plurality of complex resistance probes are also arranged at the side wall of the high-pressure cylinder in intervals; The temperature-pressure integrated probe, the ultrasonic wave transmitting probe, the ultrasonic wave receiving probe and the complex resistance probe are electrically connected with the data processing module.

7. A method of testing using the comprehensive testing device for effect of mud cake on drilling fluid invasion into gas hydrate reservoirs according to any one of claims 1-6, characterized in that, The method comprises the following steps: S1, connection of the device and detection of air tightness; S2, sediment loading; S3, synthesis and monitoring of hydrate: Methane gas is injected into the high-pressure cylinder, the high-pressure cylinder is cooled to a target temperature and kept unchanged, hydrate is generated in the high-pressure cylinder, and the physical property parameters of the hydrate deposit are monitored in real time during the generation of the hydrate; S4, simulation of the invasion process of the drilling fluid into the hydrate reservoir: The drilling fluid is delivered into the circulating cavity, part of the drilling fluid in the circulating cavity penetrates into the hydrate-containing sediment through the mud cake module under the action of the pressure difference, and the remaining drilling fluid is driven by the injection pressure and flows into the low-temperature water bath tank; S5, analysis of the influence of the mud cake on the invasion of the drilling fluid.

8. The test method of claim 7, wherein, In step S3, the temperature, pressure, acoustic wave and resistance data of the hydrate-containing sediment are obtained by the temperature-pressure integrated probe, the ultrasonic wave transmitting probe, the ultrasonic wave receiving probe and the complex resistance probe during the generation of the hydrate, the physical property parameters of the hydrate-containing sediment are monitored in real time, and the synthesis of the hydrate is determined.

9. The test method of claim 7, wherein, In step S4, the temperature-pressure characteristics of the hydrate-containing sediment during the invasion of the drilling fluid are obtained by the temperature-pressure integrated probe, the acoustic characteristics of the hydrate-containing sediment during the invasion of the drilling fluid are obtained by the ultrasonic wave transmitting probe, and the electrical characteristics of the hydrate-containing sediment during the invasion of the drilling fluid are obtained by the complex resistance probe, so as to determine the invasion degree of the drilling fluid and the decomposition characteristics of the hydrate.

10. The test method of claim 7, wherein, In step S5, the solid particles of the mud cake are changed to simulate the influence of different mud cakes on the invasion process of the drilling fluid; The confining pressure of the mud cake layer is loaded by the briquetting and rubber sleeve, different confining pressure liquids are injected into the hydraulic body through the hydraulic channel, the confining pressure of the mud cake layer is changed by controlling the confining pressure liquid, and the influence of mud cakes with different compaction degrees on the invasion process of the drilling fluid is simulated; The medium type of the filling medium is changed to simulate the influence of different filling layers on the invasion process of the drilling fluid.

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