Experimental device and method for simulating convection heat transfer between drilling fluid and natural gas hydrate

Abstract

The present invention discloses a device and method for simulating the convective heat exchange between drilling fluid and natural gas hydrates, which relates to the technical field of natural gas hydrate drilling equipment and methods, and includes: a reactor, a sealing cover, an external guide tube, and a separator tube; when the separator tube is in a first position, the lower end of the separator tube is located in the second separator tube opening, and the reaction chamber is connected to the outside world; when the separator tube is in a second position, the upper end of the separator tube is located in the second separator tube opening, and the lower end of the separator tube passes through the first separator tube opening. The separator tube is sealed from the first separator tube opening and the second separator tube opening, so that the reaction chamber is sealed. The device and method for simulating the convective heat exchange between drilling fluid and natural gas hydrates provided by the present invention can simulate the effect of convective heat exchange between drilling fluid and natural gas hydrate on natural gas hydrates after the generated natural gas hydrates are extracted from the physical separation structure and injected with drilling fluid.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas hydrate drilling equipment and methods, and in particular to a drilling fluid and natural gas hydrate convection heat exchange simulation experimental device and method. Background Art

[0002] Natural gas hydrates are a highly efficient, clean energy source, commonly found in high-pressure, low-temperature environments such as the deep seabed and permafrost zones. During drilling in gas hydrate formations, convective heat transfer between drilling fluid and gas hydrates can disrupt the pressure and temperature conditions that stabilize the hydrates, causing them to decompose. This, in turn, reduces near-wellbore formation stability, leading to drilling failures and compromising drilling safety. Therefore, clarifying the convective heat transfer between drilling fluid and gas hydrate formations and understanding the rate of gas hydrate decomposition are key to ensuring drilling safety, requiring specialized experimental setups for this research. However, currently, there is a lack of experimental setups that solely consider convective heat transfer between drilling fluid and gas hydrate formations. Existing gas hydrate experimental setups first generate gas hydrates in situ by controlling temperature and pressure conditions, and then conduct subsequent experiments on the gas hydrate formations. To preserve drilling fluid flow channels in the simulated formation, the channels must be physically separated from the synthesis area during the gas hydrate synthesis process. After hydrate formation, the physical barrier must be removed to ensure direct contact between the drilling fluid and the gas hydrate-bearing formation before studying the convective heat transfer between the two. To ensure safe drilling in gas hydrate-bearing formations, it is necessary to design an experimental apparatus and method to simulate the convective heat transfer between the drilling fluid and the gas hydrate formation. Summary of the Invention

[0003] The purpose of the present invention is to provide a drilling fluid and natural gas hydrate convective heat exchange simulation experimental device that can simulate the generated natural gas hydrate formation and, after the physical separation structure is extracted and drilling fluid is injected, achieve direct contact between the drilling fluid and the natural gas hydrate formation in the annulus, and study the influence of the convective heat exchange between the drilling fluid and the natural gas hydrate formation on the natural gas hydrate.

[0004] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0005] The present invention provides a drilling fluid and natural gas hydrate convection heat exchange simulation experimental device, comprising a reaction mechanism, a driving mechanism, and a temperature sensing mechanism, wherein the reaction mechanism comprises:

[0006] A reactor, the upper end of which is open, and a first separating pipe opening is formed in the middle of the lower end of the reactor;

[0007] A sealing cover is provided at the upper end of the reactor, a second separation pipe opening is formed in the middle of the sealing cover, the sealing cover and the reactor are surrounded to form a reaction chamber, the reaction chamber is used to contain at least structural sand, methane, and water, and the temperature sensing mechanism is provided in the reaction chamber;

[0008] an outer guide tube extending upward from the upper end of the sealing cover, wherein the driving mechanism is arranged at the upper end of the outer guide tube;

[0009] a separator tube movably disposed in the outer guide tube, wherein the upper end of the separator tube is connected to the driving mechanism, and the driving mechanism is used to drive the separator tube to move between a first position and a second position;

[0010] Among them, when the separation tube is located in the first position, the lower end of the separation tube is located in the second separation tube opening, and the reaction chamber is connected to the outside; when the separation tube is located in the second position, the upper end of the separation tube is located in the second separation tube opening, and the lower end of the separation tube passes through the first separation tube opening, and the separation tube is sealed from the first separation tube opening and the second separation tube opening, so that the reaction chamber is sealed.

[0011] In a preferred embodiment, the reaction mechanism includes:

[0012] An injection structure is formed by extending downward from the lower end of the reactor, and an injection cavity is formed in the injection structure;

[0013] An inner guide tube is formed by extending upward from the middle of the injection structure, and passes through the first separation tube opening and the second separation tube opening. The separation tube can be movably mounted on the inner guide tube. When the separation tube is in the second position, the lower end of the separation tube extends into the injection cavity.

[0014] In a preferred embodiment, a first fluid guide portion is formed on the inner wall of the outer guide tube, and a second fluid guide portion is formed on the outer wall of the inner guide tube. The first fluid guide portion and the second fluid guide portion have the same height and are located above the sealing cover.

[0015] A first fluid outlet is formed on a side wall of the outer guide tube, wherein the height of the first fluid outlet is lower than the height of the first fluid guide portion and higher than the height of the sealing cover;

[0016] A second fluid outlet is formed on the separator tube. When the separator tube is located at the first position, the height of the second fluid outlet is lower than the height of the first fluid guide portion and higher than the height of the sealing cover. The reaction chamber is connected to the outside through the gap between the separator tube and the inner guide tube, the second fluid outlet, and the first fluid outlet to discharge the drilling fluid.

[0017] In a preferred embodiment, a first sealing portion is formed on the inner wall of the outer guide tube, and the height of the first sealing portion is higher than that of the first fluid guiding portion;

[0018] The reaction mechanism includes multiple Gly rings, which are respectively arranged on the first sealing part, between the sealing cover and the reactor, on the radial inner wall of the sealing cover at the second partition pipe opening, and on the radial inner wall of the reactor at the first partition pipe opening to ensure the sealing of the reaction chamber.

[0019] In a preferred embodiment, the temperature sensing mechanism includes a plurality of temperature sensing units, each of which includes a plurality of temperature sensors, and the plurality of temperature sensors on the same temperature sensing unit are evenly distributed axially in the reaction chamber; half of the temperature sensing units are evenly distributed along a first radial direction, and the other half of the temperature sensing units are evenly distributed along a second radial direction, and the angle between the first radial direction and the second radial direction is 90 degrees.

[0020] In a preferred embodiment, a transmission portion is formed on the upper end of the separation tube, and a clamping portion is formed on the upper end of the transmission portion, and the clamping portion is used for a lifting tool to clamp the separation tube;

[0021] The driving mechanism comprises:

[0022] A fixed shell is arranged at the upper end of the outer guide tube;

[0023] A driver, disposed on the fixed housing;

[0024] The transmission disc is rotatably arranged in the fixed housing. The transmission disc and the transmission part are connected to each other through threads. The driver is used to drive the transmission disc to drive the telescopic rod to move.

[0025] In a preferred embodiment, the sealing cover is formed with an air inlet, a sand filling port, a circuit port, and a pressure detection port, and the sand filling port is used to add structural sand into the reaction chamber;

[0026] The drilling fluid and natural gas hydrate convection heat exchange simulation experimental device comprises:

[0027] a methane pressure regulating injection device, used for injecting methane into the reaction chamber through the gas inlet;

[0028] An aviation plug, sealed and disposed on the circuit port;

[0029] a data acquisition device, electrically connected to the aviation plug, for collecting temperature information of the temperature sensing mechanism;

[0030] A pressure sensor is sealed and arranged on the pressure detection port to detect the pressure in the reaction chamber.

[0031] In a preferred embodiment, a water circulation cavity is formed inside the side wall of the reactor, a water circulation port is formed on the side wall of the reactor, a water injection port is formed at the bottom of the reactor, and a drilling fluid injection port and a nitrogen injection port are formed at the bottom of the injection structure;

[0032] The drilling fluid and natural gas hydrate convection heat exchange simulation experimental device comprises:

[0033] a water injection device, configured to inject at least part of the water into the reaction chamber through the water injection port;

[0034] A water bath circulating thermostat, wherein the water injection device is used to heat the remaining water through the water bath circulating thermostat and inject it into the water circulation chamber through the water circulation port to maintain the temperature in the reaction chamber;

[0035] a drilling fluid temperature and pressure regulating injection device, which is used to inject drilling fluid into the injection cavity through the drilling fluid injection port and allow the drilling fluid to flow through the reaction cavity when the separation tube is located at the first position;

[0036] A nitrogen pressure-regulating injection device is used to inject nitrogen into the injection cavity through the nitrogen injection port and flow through the reaction cavity when the separation tube is located at the first position.

[0037] In a preferred embodiment, the drilling fluid and natural gas hydrate convective heat exchange simulation experimental device further includes:

[0038] a communicating pipeline connected to the first fluid outlet;

[0039] a waste gas and waste liquid collection device, connected to the first fluid outlet through the connecting pipe, so as to collect the drilling fluid and nitrogen flowing out of the reaction chamber;

[0040] a sand removal device, provided on the connecting pipeline, for removing structural sand in the drilling fluid flowing out of the reaction chamber;

[0041] a gas-liquid separator, provided on the connecting pipeline and located behind the desander, to separate the drilling fluid and the nitrogen;

[0042] a gas flow meter, disposed on the connecting pipeline, for calculating the volume of the nitrogen gas flowing out of the reaction chamber;

[0043] A liquid flow meter is provided on the communicating pipeline and is used to calculate the volume of the drilling fluid flowing out of the reaction chamber.

[0044] Another object of the present invention is to provide a method for simulating the convective heat exchange between drilling fluid and natural gas hydrate formations, which can simulate the generated natural gas hydrate formation, after the physical separation structure is extracted and drilling fluid is injected, to achieve direct contact between the drilling fluid and the natural gas hydrate formation in the annulus, and study the influence of the convective heat exchange between the drilling fluid and the natural gas hydrate formation on the natural gas hydrate.

[0045] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0046] The present invention provides a method for simulating convective heat exchange between drilling fluid and natural gas hydrate formations. The method can test the convective heat exchange law between drilling fluid and natural gas hydrate formations and the decomposition state of natural gas hydrates using the above-mentioned convective heat exchange simulation experimental device for drilling fluid and natural gas hydrates. The method comprises the following steps:

[0047] When the separation tube is in the second position, all connecting valves are closed and dry sand is added into the reaction chamber through the sand filling port;

[0048] By opening and closing the fifth valve, the seventh valve, and the third valve, the methane gas in the reaction chamber is purged three times to ensure that the gas in the reaction chamber is pure methane;

[0049] closing the seventh valve and the third valve, injecting methane into the reaction chamber through the fifth valve until the fourth pressure sensor reaches a first predetermined pressure to ensure that a preset amount of methane is injected into the reaction chamber, and then closing the fifth valve;

[0050] injecting water into the water circulation chamber through a water bath circulating thermostat to increase the temperature in the reaction chamber and ensure that the reaction chamber is outside the stable zone of natural gas hydrates;

[0051] After the pressure in the reaction chamber stabilizes, opening the fourth valve, injecting water into the reaction chamber until the fourth pressure sensor reaches a second predetermined pressure, and then closing the fourth valve;

[0052] Lowering the temperature in the reaction chamber to the natural gas hydrate stable zone by the water bath circulating thermostat to start generating natural gas hydrate, and determining the generation status of the natural gas hydrate by the fourth pressure sensor and the temperature sensing mechanism;

[0053] After the natural gas hydrate in the reaction chamber is completely generated, the second valve is opened, nitrogen is injected until the pressure of the first pressure sensor is the same as the pressure of the fourth pressure sensor, and the pressure is maintained so that the pressure inside the separation tube is the same as the pressure in the reaction chamber;

[0054] Starting the driving mechanism to drive the separation tube to the first position, thereby creating a direct contact condition between the drilling fluid and the natural gas hydrate, so that the convective heat exchange experiment between the drilling fluid and the natural gas hydrate is ready;

[0055] opening the first valve, the sixth valve, and the third valve, injecting drilling fluid of a preset temperature and a third preset pressure at a constant flow rate through the drilling fluid temperature and pressure regulating injection device, obtaining the pressure of the drilling fluid when it flows into the reaction chamber through the first pressure sensor, obtaining the temperature of the drilling fluid when it flows into the reaction chamber through the first temperature sensor, obtaining the pressure of the drilling fluid when it flows out of the reaction chamber through the third pressure sensor, and obtaining the temperature of the drilling fluid when it flows out of the reaction chamber through the second temperature sensor, and transmitting the collected sensor signals to the data acquisition system;

[0056] Under the circulation of the drilling fluid, the natural gas hydrate decomposes and flows out from the first fluid outlet together with the sand particles;

[0057] Collect temperature changes measured by temperature sensing mechanisms, determine the decomposition boundary of natural gas hydrates, and monitor the decomposition of natural gas hydrates;

[0058] The drilling fluid, water, and methane flowing out of the reaction chamber are processed by a desander and a gas-liquid separator, the liquid flow is measured by a liquid flow meter, and the gas flow is measured by a gas flow meter;

[0059] After the experiment is completed, the methane, water, drilling fluid, and natural gas hydrate in the reaction chamber are treated, and cleaning water is injected by opening the fourth valve to clean the reaction chamber. The gas and liquid in the reaction chamber are collected by opening the seventh valve, the eighth valve, the third valve, and the ninth valve.

[0060] The characteristics and advantages of the present invention are:

[0061] The present invention provides an experimental device and method for simulating the convective heat exchange between drilling fluid and natural gas hydrates. When the separator tube is in the second position, structural sand is placed in the reaction chamber, and methane and water are injected. The temperature and pressure in the reaction chamber are adjusted to the point where natural gas hydrates are formed, thereby effectively simulating natural gas hydrate formations. By driving the separator tube upward through a driving structure, the annulus in actual drilling can be effectively simulated. By injecting drilling fluid, the convective heat exchange laws between drilling fluid and natural gas hydrates and the decomposition laws of natural gas hydrates can be effectively explored, providing guidance for actual drilling. The decomposition and shape of natural gas hydrates are monitored by a temperature sensing mechanism, and the mass or flow rate of water and methane decomposed from natural gas hydrates is measured by a liquid flowmeter and a gas flowmeter, thereby quantitatively evaluating the convective heat exchange effect between drilling fluid and natural gas hydrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0063] Figure 1 Shown is a schematic diagram of the overall structure of the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device of the present invention, where the separator tube is in the first position.

[0064] Figure 2 Shown is a schematic diagram of the overall structure of the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device of the present invention, where the separator tube is in the second position.

[0065] Figure 3 The figure shows the temperature sensing unit structure of the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device of the present invention. Figure 1 AA perspective diagram. DETAILED DESCRIPTION

[0066] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without inventive effort are within the scope of protection of the present invention. It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there can be an intermediate element. The terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to mechanical or electrical connections, internal communication between two elements, direct connection, or indirect connection through an intermediary. Those of ordinary skill in the art will understand the specific meanings of these terms based on the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0067] See also Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a drilling fluid and natural gas hydrate convection heat exchange simulation experimental device, including a reaction mechanism 1, a driving mechanism 2, and a temperature sensing mechanism 3. The reaction mechanism 1 includes: a reactor 11, the upper end of which is open, and a first separation pipe opening 111 is formed in the middle of the lower end of the reactor 11; a sealing cover 12, the sealing cover 12 is provided at the upper end of the reactor 11, and a second separation pipe opening 121 is formed in the middle of the sealing cover 12. The sealing cover 12 and the reactor 11 are surrounded by a reaction chamber 112, and the reaction chamber 112 is used to contain at least structural sand, methane, and water. The temperature sensing mechanism 3 is provided in the reaction chamber 112; an outer guide pipe 13 is extended upward from the upper end of the sealing cover 12 to form a driving mechanism 2, and a temperature sensing mechanism 3 is provided in the reaction chamber 112; The mechanism 2 is arranged at the upper end of the outer guide tube 13; the separator tube 14 is movably arranged in the outer guide tube 13, and the upper end of the separator tube 14 is connected to the driving mechanism 2, and the driving mechanism 2 is used to drive the separator tube 14 to move between the first position and the second position; wherein, when the separator tube 14 is in the first position, the lower end of the separator tube 14 is located in the second separator tube opening 121, and the reaction chamber 112 is connected to the outside world; when the separator tube 14 is in the second position, the upper end of the separator tube 14 is located in the second separator tube opening 121, and the lower end of the separator tube 14 passes through the first separator tube opening 111, and the separator tube 14 and the first separator tube opening 111 and the second separator tube opening 121 are all sealed to make the reaction chamber 112 airtight.

[0068] The experimental device for simulating convective heat transfer between drilling fluid and natural gas hydrates provided in an embodiment of the present invention effectively simulates natural gas hydrate formation by placing structural sand in the reaction chamber 112, injecting methane and water, and adjusting the temperature and pressure in the reaction chamber 112 to the point where natural gas hydrates form. The upward movement of the separator tube 14 by the drive structure effectively simulates the annular space in actual drilling. The injection of drilling fluid effectively explores the convective heat transfer between the drilling fluid and natural gas hydrates, as well as the decomposition of natural gas hydrates, providing guidance for actual drilling. The decomposition and shape of natural gas hydrates are monitored by the temperature sensing mechanism 3, and the mass or flow rate of water and methane produced by the decomposition of natural gas hydrates is measured by a liquid flowmeter and a gas flowmeter, allowing for quantitative evaluation of the convective heat transfer between the drilling fluid and natural gas hydrates.

[0069] To further illustrate the specific structure of the drilling fluid and natural gas hydrate convective heat exchange simulation experimental device according to the embodiment of the present invention, the specific components and connection relationships thereof are further described below, wherein:

[0070] In a preferred embodiment, the reaction mechanism 1 includes: an injection structure 15, which extends downward from the lower end of the reactor 11, and an injection cavity 151 is formed in the injection structure; an inner guide tube 16, which extends upward from the middle of the injection structure 15, and the inner guide tube 16 passes through the first separation tube opening 111 and the second separation tube opening 121. The separation tube 14 can be movably mounted on the inner guide tube 16. When the separation tube 14 is in the second position, the lower end of the separation tube 14 extends into the injection cavity 151.

[0071] In a preferred embodiment, a first fluid guide portion 131 is formed on the inner wall of the outer guide tube 13, and a second fluid guide portion 161 is formed on the outer wall of the inner guide tube 16. The height of the first fluid guide portion 131 is the same as that of the second fluid guide portion 161, and is located above the sealing cover 12; a first fluid outlet 132 is formed on the side wall of the outer guide tube 13, and the height of the first fluid outlet 132 is lower than the height of the first fluid guide portion 131 and higher than the height of the sealing cover 12; a second fluid outlet 141 is formed on the separator tube 14, and when the separator tube 14 is in the first position, the height of the second fluid outlet 141 is lower than the height of the first fluid guide portion 131 and higher than the height of the sealing cover 12. The reaction chamber 112 is connected to the outside through the gap between the separator tube 14 and the inner guide tube 16, the second fluid outlet 141, and the first fluid outlet 132 to discharge the drilling fluid.

[0072] In a preferred embodiment, a first sealing portion 133 is formed on the inner wall of the outer guide tube 13, and the height of the first sealing portion 133 is higher than the first fluid guide portion 131; the reaction mechanism 1 includes a plurality of Gly rings 17, and the plurality of Gly rings 17 are respectively arranged on the first sealing portion 133, between the sealing cover 12 and the reactor 11, on the radial inner wall of the sealing cover 12 at the second partition pipe opening 121, and on the radial inner wall of the reactor 11 at the first partition pipe opening 111, to ensure the sealing of the reaction chamber 112.

[0073] Please also refer to Figure 3 As shown, in a preferred embodiment, the temperature sensing mechanism 3 includes a plurality of temperature sensing units 31, each temperature sensing unit 31 includes a plurality of temperature sensors 311, and the plurality of temperature sensors 311 on the same temperature sensing unit 31 are evenly distributed along the axial direction in the reaction chamber 112; half of the temperature sensing units 31 are evenly distributed along the first radial direction, and the other half of the temperature sensing units 31 are evenly distributed along the second radial direction, and the angle between the first radial direction and the second radial direction is 90 degrees.

[0074] In a preferred embodiment, a transmission portion 142 is formed at the upper end of the separator tube 14, and a clamping portion 143 is formed at the upper end of the transmission portion 142, and the clamping portion 143 is used for the lifting tool to clamp the separator tube 14; the driving mechanism 2 includes: a fixed shell 21, which is arranged at the upper end of the outer guide tube; a driver 22, which is arranged on the fixed shell 21; a transmission disk 23, which is rotatably arranged in the fixed shell 21, and the transmission disk 23 and the transmission portion 142 are connected by a threaded transmission. The driver 22 is used to drive the transmission disk 23 to drive the telescopic rod to move.

[0075] In a preferred embodiment, the sealing cover 12 is formed with an air inlet 125, a sand filling port 122, a circuit port 123, and a pressure detection port 124. The sand filling port 122 is used to add structural sand into the reaction chamber 112; the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device includes: a methane pressure regulating injection device, used to inject methane into the reaction chamber 112 through the air inlet 125; an aviation plug, sealed and set on the circuit port 123; a data acquisition device, electrically connected to the aviation plug, used to collect temperature information of the temperature sensing mechanism 3; a pressure sensor, sealed and set on the pressure detection port 124, to detect the pressure in the reaction chamber 112.

[0076] In a preferred embodiment, a water circulation chamber 113 is formed inside the side wall of the reactor 11, a water circulation port 114 is formed on the side wall of the reactor 11, a water injection port 115 is formed at the bottom of the reactor 11, and a drilling fluid injection port 152 and a nitrogen injection port 153 are formed at the bottom of the injection structure 15; the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device includes: a water injection device for injecting at least part of the water into the reaction chamber 112 through the water injection port 115; a water bath circulation constant temperature device, and a water injection device for allowing the remaining water to pass through the water bath. The water bath circulating constant temperature device heats and injects the water into the water circulation chamber 113 through the water circulation port 114 to maintain the temperature in the reaction chamber 112; the drilling fluid temperature and pressure regulating injection device, when the separation tube 14 is in the first position, the drilling fluid temperature and pressure regulating injection device is used to inject the drilling fluid into the injection chamber 151 through the drilling fluid injection port 152 and flow through the reaction chamber 112; the nitrogen pressure regulating injection device, when the separation tube 14 is in the first position, the nitrogen pressure regulating injection device is used to inject the drilling fluid into the injection chamber 151 through the nitrogen injection port 153 and flow through the reaction chamber 112.

[0077] In a preferred embodiment, the drilling fluid and natural gas hydrate convection heat exchange simulation experimental device also includes: a connecting pipe 4, connected to the first fluid outlet 132; a waste gas and waste liquid collection device, connected to the first fluid outlet 132 through the connecting pipe 4, to collect the drilling fluid and nitrogen flowing out of the reaction chamber 112; a sand removal device, arranged on the connecting pipe 4, to remove the structural sand in the drilling fluid flowing out of the reaction chamber 112; a gas-liquid separator, arranged on the connecting pipe 4, and located behind the sand removal device, to separate the drilling fluid and nitrogen; a gas flow meter, arranged on the connecting pipe 4, for calculating the volume of nitrogen flowing out of the reaction chamber 112; a liquid flow meter, arranged on the connecting pipe 4, for calculating the volume of the drilling fluid flowing out of the reaction chamber 112.

[0078] To cooperate with the above-mentioned drilling fluid and natural gas hydrate convective heat transfer simulation experimental device and further ensure that the experimental process can simulate actual process conditions, an embodiment of the present invention also provides a drilling fluid and natural gas hydrate convective heat transfer simulation experimental method to study the convective heat transfer law between drilling fluid and natural gas hydrate and the decomposition state of natural gas hydrate. The method comprises the following steps:

[0079] S100: When the separation tube 14 is in the second position, all connecting valves are closed, and dry sand is added into the reaction chamber 112 through the sand filling port 122;

[0080] S200: Performing three methane gas purification operations in the reaction chamber 112 by opening and closing the fifth valve V5, the seventh valve V7, and the third valve V3 to ensure that the gas in the reaction chamber 112 is pure methane;

[0081] S300: Close the seventh valve V7 and the third valve V3, inject methane into the reaction chamber 112 through the fifth valve V5 until the fourth pressure sensor P4 reaches a predetermined pressure to ensure that a preset amount of methane is injected into the reaction chamber 112, and then close the fifth valve V5.

[0082] S400: injecting water into the water circulation chamber 113 through the water bath circulating thermostat to increase the temperature in the reaction chamber 112 and ensure that the reaction chamber 112 is outside the stable zone of natural gas hydrates;

[0083] S500: After the pressure in the reaction chamber 112 stabilizes, the fourth valve V4 is opened, and water is injected into the reaction chamber 112 until the pressure measured by the fourth pressure sensor P4 reaches a predetermined pressure, and the fourth valve V4 is closed.

[0084] S600: Lowering the temperature in the reaction chamber 112 to the natural gas hydrate stable zone through the water bath circulating thermostat to start generating natural gas hydrates, and determining the generation status of natural gas hydrates through the fourth pressure sensor P4 and the temperature sensing mechanism 3;

[0085] S700: After the natural gas hydrate is completely generated in the reaction chamber 112, the second valve V2 is opened, and nitrogen is injected until the pressure of the first pressure sensor P1 and the pressure of the fourth pressure sensor P4 are the same. The pressure is then maintained so that the pressure inside the separation tube 14 is the same as the pressure inside the reaction chamber 112.

[0086] S800: Starting the driving mechanism 2 to drive the separation tube 14 to the first position, thereby creating a direct contact condition between the drilling fluid and the natural gas hydrate, so that the convective heat exchange experiment between the drilling fluid and the natural gas hydrate is ready.

[0087] S900: Open the first valve V1, the sixth valve V6, and the third valve V3, and inject drilling fluid of a preset temperature and pressure at a constant flow rate through the drilling fluid temperature and pressure regulating injection device. The pressure of the drilling fluid as it flows into the reaction chamber 112 is obtained through the first pressure sensor P1, the temperature of the drilling fluid as it flows into the reaction chamber 112 is obtained through the first temperature sensor T1, the pressure of the drilling fluid as it flows out of the reaction chamber 112 is obtained through the third pressure sensor P3, and the temperature of the drilling fluid as it flows out of the reaction chamber 112 is obtained through the second temperature sensor T2. The collected sensor signals are transmitted to the data acquisition system.

[0088] S1000: Under the circulation of the drilling fluid, the natural gas hydrate decomposes and flows out from the first fluid outlet 132 along with the sand particles;

[0089] S1100: collecting temperature changes measured by the temperature sensing mechanism 3, determining the decomposition boundary of the natural gas hydrate, and monitoring the decomposition of the natural gas hydrate;

[0090] S1200: The drilling fluid, water, and methane flowing out of the reaction chamber 112 are processed by a desander and a gas-liquid separator. The liquid flow rate is measured by a liquid flow meter, and the gas flow rate is measured by a gas flow meter.

[0091] S1300: After the experiment is completed, the methane, water, drilling fluid, and natural gas hydrate in the reaction chamber 112 are processed. Cleaning water is injected by opening the fourth valve V4 to clean the reaction chamber 112. The gas and liquid in the reaction chamber 112 are collected by opening the seventh valve V7, the eighth valve V8, the third valve V3, and the ninth valve V9.

[0092] The above are merely embodiments of the present invention. Those skilled in the art may make various changes or modifications to the embodiments of the present invention based on the contents disclosed in the application documents without departing from the spirit and scope of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A drilling fluid and natural gas hydrate convection heat transfer simulation experimental device, characterized in that: It includes a reaction mechanism, a driving mechanism, and a temperature sensing mechanism. The reaction mechanism includes: A reactor, the upper end of which is open, and a first separating pipe opening is formed in the middle of the lower end of the reactor; A sealing cover is provided at the upper end of the reactor, a second separation pipe opening is formed in the middle of the sealing cover, the sealing cover and the reactor are surrounded to form a reaction chamber, the reaction chamber is used to contain at least structural sand, methane, and water, and the temperature sensing mechanism is provided in the reaction chamber; an outer guide tube extending upward from the upper end of the sealing cover, wherein the driving mechanism is arranged at the upper end of the outer guide tube; a separator tube movably disposed in the outer guide tube, wherein the upper end of the separator tube is connected to the driving mechanism, and the driving mechanism is used to drive the separator tube to move between a first position and a second position; Among them, when the separation tube is located in the first position, the lower end of the separation tube is located in the second separation tube opening, and the reaction chamber is connected to the outside; when the separation tube is located in the second position, the upper end of the separation tube is located in the second separation tube opening, and the lower end of the separation tube passes through the first separation tube opening, and the separation tube is sealed from the first separation tube opening and the second separation tube opening, so that the reaction chamber is sealed.

2. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 1, characterized in that: The reaction mechanism comprises: An injection structure extending downward from the lower end of the reactor, wherein an injection cavity is formed in the injection structure; An inner guide tube is formed by extending upward from the middle of the injection structure, and passes through the first separation tube opening and the second separation tube opening. The separation tube can be movably mounted on the inner guide tube. When the separation tube is in the second position, the lower end of the separation tube extends into the injection cavity.

3. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 2, characterized in that: A first fluid guide portion is formed on the inner wall of the outer guide tube, and a second fluid guide portion is formed on the outer wall of the inner guide tube. The first fluid guide portion and the second fluid guide portion have the same height and are located above the sealing cover. A first fluid outlet is formed on a side wall of the outer guide tube, wherein the height of the first fluid outlet is lower than the height of the first fluid guide portion and higher than the height of the sealing cover; A second fluid outlet is formed on the separator tube. When the separator tube is located at the first position, the height of the second fluid outlet is lower than the height of the first fluid guide portion and higher than the height of the sealing cover. The reaction chamber is connected to the outside through the gap between the separator tube and the inner guide tube, the second fluid outlet, and the first fluid outlet to discharge the drilling fluid.

4. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 3, characterized in that: A first sealing portion is formed on the inner wall of the outer guide tube, and the height of the first sealing portion is higher than the first fluid guiding portion; The reaction mechanism includes multiple Gly rings, which are respectively arranged on the first sealing part, between the sealing cover and the reactor, on the radial inner wall of the sealing cover at the second partition pipe opening, and on the radial inner wall of the reactor at the first partition pipe opening to ensure the sealing of the reaction chamber.

5. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 1, characterized in that: The temperature sensing mechanism includes multiple temperature sensing units, each of which includes multiple temperature sensors. The multiple temperature sensors on the same temperature sensing unit are evenly distributed axially in the reaction chamber; half of the temperature sensing units are evenly distributed along a first radial direction, and the other half of the temperature sensing units are evenly distributed along a second radial direction, and the angle between the first radial direction and the second radial direction is 90 degrees.

6. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 1, characterized in that: A transmission portion is formed at the upper end of the separation tube, and a clamping portion is formed at the upper end of the transmission portion, and the clamping portion is used for a lifting tool to clamp the separation tube; The driving mechanism comprises: A fixed shell is arranged at the upper end of the outer guide tube; A driver, disposed on the fixed housing; The transmission disc is rotatably arranged in the fixed housing. The transmission disc and the transmission part are connected to each other through threads. The driver is used to drive the transmission disc to drive the telescopic rod to move.

7. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 1, characterized in that: The sealing cover is formed with an air inlet, a sand filling port, a circuit port, and a pressure detection port, wherein the sand filling port is used to add structural sand into the reaction chamber; The drilling fluid and natural gas hydrate convection heat exchange simulation experimental device comprises: a methane pressure regulating injection device, used for injecting methane into the reaction chamber through the gas inlet; An aviation plug, sealed and disposed on the circuit port; a data acquisition device, electrically connected to the aviation plug, for collecting temperature information of the temperature sensing mechanism; A pressure sensor is sealed and arranged on the pressure detection port to detect the pressure in the reaction chamber.

8. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 2, characterized in that: A water circulation cavity is formed inside the side wall of the reactor, a water circulation port is formed on the side wall of the reactor, a water injection port is formed at the bottom of the reactor, and a drilling fluid injection port and a nitrogen injection port are formed at the bottom of the injection structure; The drilling fluid and natural gas hydrate convection heat exchange simulation experimental device comprises: a water injection device, configured to inject at least part of the water into the reaction chamber through the water injection port; A water bath circulating thermostat, wherein the water injection device is used to heat the remaining water through the water bath circulating thermostat and inject it into the water circulation chamber through the water circulation port to maintain the temperature in the reaction chamber; a drilling fluid temperature and pressure regulating injection device, which is used to inject drilling fluid into the injection cavity through the drilling fluid injection port and allow the drilling fluid to flow through the reaction cavity when the separation tube is located at the first position; A nitrogen pressure-regulating injection device is used to inject nitrogen into the injection cavity through the nitrogen injection port and flow through the reaction cavity when the separation tube is located at the first position.

9. The drilling fluid and natural gas hydrate convection heat transfer simulation experimental device according to claim 3, characterized in that: The drilling fluid and natural gas hydrate convection heat exchange simulation experimental device also includes: a communicating pipeline connected to the first fluid outlet; a waste gas and waste liquid collection device, connected to the first fluid outlet through the communication pipeline, so as to collect drilling fluid, water, and methane flowing out of the reaction chamber; a sand removal device, provided on the connecting pipeline, for removing structural sand in the drilling fluid flowing out of the reaction chamber; a gas-liquid separator, provided on the connecting pipeline and located behind the desander, to separate the drilling fluid and the methane; a gas flow meter, disposed on the communicating pipeline, for calculating the volume of the methane flowing out of the reaction chamber; A liquid flow meter is provided on the communicating pipeline and is used for calculating the volume of the drilling fluid and water flowing out of the reaction chamber.

10. A method for simulating heat transfer between drilling fluid and natural gas hydrate, which can test the convective heat transfer law between drilling fluid and natural gas hydrate by using the simulating heat transfer experiment device for drilling fluid and natural gas hydrate according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: When the separation tube is in the second position, all connecting valves are closed and dry sand is added into the reaction chamber through the sand filling port; By opening and closing the fifth valve, the seventh valve, and the third valve, the methane gas in the reaction chamber is purged three times to ensure that the gas in the reaction chamber is pure methane; closing the seventh valve and the third valve, injecting methane into the reaction chamber through the fifth valve until the fourth pressure sensor reaches a first predetermined pressure to ensure that a preset amount of methane is injected into the reaction chamber, and then closing the fifth valve; injecting water into the water circulation chamber through a water bath circulating thermostat to increase the temperature in the reaction chamber and ensure that the reaction chamber is outside the stable zone of natural gas hydrates; After the pressure in the reaction chamber stabilizes, opening the fourth valve, injecting water into the reaction chamber until the fourth pressure sensor reaches a second predetermined pressure, and then closing the fourth valve; Lowering the temperature in the reaction chamber to the natural gas hydrate stable zone by the water bath circulating thermostat to start generating natural gas hydrate, and determining the generation status of the natural gas hydrate by the fourth pressure sensor and the temperature sensing mechanism; After the natural gas hydrate in the reaction chamber is completely generated, the second valve is opened, nitrogen is injected until the pressure of the first pressure sensor is the same as the pressure of the fourth pressure sensor, and the pressure is maintained so that the pressure inside the separation tube is the same as the pressure in the reaction chamber; Starting the driving mechanism to drive the separation tube to the first position, thereby creating a direct contact condition between the drilling fluid and the natural gas hydrate, so that the convective heat exchange experiment between the drilling fluid and the natural gas hydrate is ready; opening the first valve, the sixth valve, and the third valve, injecting drilling fluid of a preset temperature and a third preset pressure at a constant flow rate through the drilling fluid temperature and pressure regulating injection device, obtaining the pressure of the drilling fluid when it flows into the reaction chamber through the first pressure sensor, obtaining the temperature of the drilling fluid when it flows into the reaction chamber through the first temperature sensor, obtaining the pressure of the drilling fluid when it flows out of the reaction chamber through the third pressure sensor, and obtaining the temperature of the drilling fluid when it flows out of the reaction chamber through the second temperature sensor, and transmitting the collected sensor signals to the data acquisition system; Under the circulation of the drilling fluid, the natural gas hydrate decomposes and flows out from the first fluid outlet together with the sand particles; Collect temperature changes measured by temperature sensing mechanisms, determine the decomposition boundary of natural gas hydrates, and monitor the decomposition of natural gas hydrates; The drilling fluid, water, and methane flowing out of the reaction chamber are processed by a desander and a gas-liquid separator, the liquid flow is measured by a liquid flow meter, and the gas flow is measured by a gas flow meter; After the experiment is completed, the methane, water, drilling fluid, and natural gas hydrate in the reaction chamber are treated, and cleaning water is injected by opening the fourth valve to clean the reaction chamber. The gas and liquid in the reaction chamber are collected by opening the seventh valve, the eighth valve, the third valve, and the ninth valve.

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