66 results about "Hydrate decomposition" patented technology

A method for determining a safe density window of a hydrate formation considering a mud cake under an action of drilling fluids is provided. The method establishes a heat-fluid-solid-chemical multi-field coupling model considering the seepage effect of the mud cake at the well wall and the influence of natural gas hydrate decomposition. The simulation results show the distribution of pore pressure, temperature, and solute concentration in the drilling fluid around the well after the drilling fluid invades. Based on the determination of multi-field coupling model, the determination results, combined with a Cullen-Moore criterion, and manner for calculating a safe density window of a hydrate formation considering the mud cake under the action of the drilling fluid is further established.

This invention relates to a highly efficient co-production system and method for deep-water shallow gas and natural gas hydrates, belonging to the field of deep-water oil and gas and natural gas hydrate development. It employs a one-injection-four-production well network, deploying one central well and four surrounding production wells in the target reservoir area. The central well is initially used for fracturing and fracture creation and participates in production; later, based on production decline or reservoir temperature reduction, it is converted from production to injection, used to inject anhydrous self-generating heat materials into the artificial fracture network. The four surrounding production wells are respectively deployed in the natural gas hydrate reservoir and the shallow gas reservoir, used for depressurization production in the target reservoir, achieving the co-production of shallow gas and hydrate decomposition gas. This invention solves problems existing in the development of deep-water shallow gas and natural gas hydrates, such as low reservoir permeability, difficult gas migration, significant reservoir temperature drop in the later stages of simple depressurization production, rapid gas production decline, easy secondary formation of natural gas hydrates, and difficulty in the co-production and efficient extraction of shallow gas and hydrates.

The present application relates to hydrate depressurization production numerical simulation technical field, specifically relates to hydrate decomposition method and system considering pressure wave time lag and pore structure entropy, the method includes the following steps: calculating pore structure entropy, constructing saturation and structure entropy dependent time memory kernel, combining decomposition rate threshold, pressure drop threshold, forming the decomposition front indicator function with prediction-correction mechanism;The time memory kernel, space-time inseparable causal kernel and threshold response function are subjected to space-time convolution operation, based on the decomposition front indicator function, an integral form of non-local memory hydrate decomposition rate model is established;The Peacley number is calculated by grid Darcy velocity, the scalar characteristic memory time is extended to the second-order symmetric anisotropic memory time tensor, the second-order tensor type memory variable is constructed and the evolution equation is established, the non-local memory hydrate decomposition rate model is coupled to the energy conservation equation and two-phase Darcy seepage pressure equation, and the decomposition result is obtained by iterative solution.

A hydrate decomposition inhibiting composition, a coupling enhanced solid hydrate, and a method for improving the solid hydrate storage and transportation stability relating to the technical field of natural gas safety storage and transportation are provided. The hydrate decomposition inhibiting composition contains a carboxymethyl starch salt and an alkyl glycoside surfactant. The composition improves the interface stability of the hydrate phase boundary and the mechanical stability of the hydrate and enhance the strength of the hydrate crystal interface since the colloidal solution formed by dispersing the sodium carboxymethyl starch and the alkyl glycoside surfactant in water can coat the surface of the hydrate to form a protective layer, thereby improving the structural stability of the hydrate. Therefore, the composition inhibits the decomposition of the hydrate, reduces the decomposition rate of the hydrate, and can further reduce the decomposition amount of the hydrate.

The present application belongs to the technical field of hydrate exploitation and CO2 storage, and discloses a continuous and synchronous method for hydrate exploitation and CO2 storage based on pressure distribution, which measures the related basic parameters of a reservoir, determines the phase equilibrium pressure of natural gas hydrate and CO2 hydrate in the hydrate reservoir, determines the exploitation scheme of the hydrate reservoir, determines the formation method of the CO2 cap layer, determines the dynamic change of the gas phase permeability in the hydrate decomposition reservoir, couples the related parameters such as effective stress and hydrate saturation, combines the control equation, determines the position of the pressure decomposition front in the hydrate reservoir, compares the position of the CO2 cap layer, optimizes and adjusts the position of the cap layer, determines the decomposition degree of the hydrate decomposition reservoir, and completes the high-density storage of CO2 in the abandoned natural gas reservoir. The present application realizes the continuous and synchronous operation of hydrate exploitation and CO2 storage, and greatly improves the efficiency of hydrate exploitation and CO2 storage.

The invention relates to the technical field of petroleum engineering drilling safety, and discloses a drilling well wall stability prediction method considering a hydrate reservoir creep effect, and the method comprises the following steps: S1, building hydrate reservoir initial heat flow field distribution based on TOUGH + HYDRATE software; s2, establishing an initial mechanical field of the hydrate reservoir by adopting FLAC3D software; s3, the TOUGH + HYDRATE software and the FLAC3D software are subjected to data interface coupling, and a multi-field coupling model is constructed; s4, carrying out a triaxial creep test, obtaining a strain-time curve, carrying out fitting analysis, preferably selecting a creep constitutive model, and carrying out parameter calibration; s5, fitting by utilizing origin software to obtain a function model of the creep parameters changing along with the saturation degree of the hydrate; and S6, well periphery parameter monitoring is conducted in the drilling simulation process. The method is suitable for borehole wall instability risk analysis under the synergistic effect of hydrate decomposition and reservoir creep.

The present application relates to the field of gas separation, in particular to a method for separating gas mixture by using hydrate. The method for separating gas mixture by using hydrate comprises the following steps: loading a specific ice medium into a reactor, controlling the loading amount and the length-diameter ratio of the pipeline in the reactor, then charging the reactor with gas under certain temperature conditions, opening a back pressure valve to discharge gas when the pressure in the reactor reaches the required pressure for separation and hydrate begins to form, controlling the specific exhaust rate to slowly discharge gas, stopping the charging and opening the back pressure valve to accelerate the discharge when the highest temperature in the reactor is reached, closing the back pressure valve and opening another exhaust valve to make the hydrate decompose and release gas when the pressure in the reactor reaches normal pressure, thereby completing the gas separation. The method can improve the separation efficiency of the gas mixture and reduce energy consumption.

A method for dissociating hydrates 7 obstructing a pipeline 4 comprises the step of supplying electromagnetic energy in the form of microwaves 6 to the hydrate, wherein the frequency of the microwaves is varied within a predetermined range rather than being supplied at a single fixed frequency. Thus, the optimum frequency, i.e., that which provides the greatest possible transfer of energy to the water, considering the temperature, pressure and type of hydrate in each particular application, is scanned and the effectiveness and efficiency of the operation is improved. The range preferably encompasses the largest possible number of statistically significant optimum frequencies considering the various operating ranges of the pipeline and various possible types of hydrates. In another aspect, an initial step is provided where an exploratory scan is performed to determine what the specific optimum frequency is for an application. Then the frequency of the microwaves is adjusted and fixed at the determined specific optimum frequency. Also disclosed is a microwave generating device 1 for performing the frequency range scanning.

The present application belongs to the technical field of natural gas hydrate exploitation, and discloses a device and method for real-time nondestructive calculation of equivalent specific heat in hydrate decomposition process. The device comprises a visual flat reaction kettle, a nondestructive high-precision phase state identification system, a gas and liquid inlet and exhaust system, and a computer acquisition system. The principle of the present application is that: through the method of providing uniform heat source by heat conduction outside the reaction kettle, hydrate decomposition is promoted, and internal heat convection can be ignored. Real-time volume fraction of each component is obtained by the nondestructive high-precision phase state identification system, Newton interpolation calculation is used for the volume fraction, latent heat of phase transition of hydrate deposit at adjacent temperature is calculated, and equivalent specific heat of hydrate deposit is obtained. The present application realizes real-time nondestructive calculation of equivalent specific heat field in hydrate decomposition process. The method is environmentally friendly and economical, and the device is clear and visual, which provides technical support for the research on latent heat of phase transition and equivalent specific heat in the process of hydrate exploitation.

The application relates to a hydrate decomposition microcosmic gas-liquid migration identification test system, which comprises a lamellar hydrate preparation module, a collection module and a quantitative analysis module. The lamellar hydrate preparation module comprises a transparent experimental soil tank, a lamellar hydrate sample arranged on the transparent experimental soil tank and a transparent soil tank cover plate covered on the lamellar hydrate sample. The lamellar hydrate sample is in the shape of a round cake, and an annular water permeable stone is arranged on the outer side of the lamellar hydrate sample. The collection module collects images and parameters of the lamellar hydrate sample in the process of gas-liquid migration in real time, inputs the images and parameters into the quantitative analysis module for processing, and obtains effective seepage porosity of the lamellar hydrate sample. Compared with the prior art, the application can solve the problems of real-time observation difficulty, low key information extraction efficiency and quantitative analysis difficulty of microcosmic gas-liquid migration in the hydrate decomposition process.

The invention relates to the field of gas separation, in particular to a method for separating a gas mixture by using hydrate. According to the method for separating the gas mixture by utilizing the hydrate, a specific ice medium is filled into a reaction kettle, the filling amount of the ice medium and the length-diameter ratio of a pipeline in the reaction kettle are controlled, then the reaction kettle is inflated under a certain temperature condition, and when the pressure in the reaction kettle reaches the pressure required by separation and the hydrate starts to be generated, the gas mixture is separated. Opening the back pressure valve to exhaust outwards, firstly controlling a specific exhaust rate to slowly exhaust, immediately stopping inflating and opening the back pressure valve to accelerate exhaust along with the generation of the hydrate when the highest temperature is reached in the reaction kettle, and closing the back pressure valve and opening the exhaust valve on the other side after the normal pressure is reached in the reaction kettle, so that the hydrate is decomposed to release gas. Therefore, gas separation is completed. According to the method, the separation efficiency of the gas mixture can be improved, and meanwhile energy consumption is reduced.

The invention discloses a drilling fluid invasion depth determination method and device considering hydrate decomposition. According to the technical scheme, a bidirectional feedback mechanism of hydrate decomposition and drilling fluid invasion is established, and the hydrate saturation, porosity, permeability and drilling fluid concentration of each reservoir position in each time step are dynamically calculated; the target drilling fluid concentration field on the hydrate reservoir prediction area is determined until the current time step is the preset invasion time, so that the drilling fluid invasion depth is determined according to the target drilling fluid concentration field and the preset concentration threshold value, the defect that a traditional model ignores reservoir physical property dynamic change is overcome, and the prediction accuracy is improved. And the accuracy and the reliability of the drilling fluid invasion depth are improved.

This invention relates to the field of natural gas hydrate extraction technology, specifically to a method and system for analyzing near-wellbore reservoir stress state during depressurization extraction of hydrate reservoirs. The method includes: constructing a reservoir heterogeneity index field and a spatiotemporal evolution mode; constructing a cementation weakening coefficient field by combining the spatiotemporal evolution mode and hydrate decomposition kinetic data; determining a constitutive model correction factor based on the cementation weakening coefficient field and reservoir core mechanics test data; solving for the disturbance stress amplification coefficient field; determining the equivalent stiffness of the wellbore-reservoir interface using wellbore structure data and dynamic pressure data; extracting a multi-field coupled response characteristic parameter set using the reservoir heterogeneity index field, spatiotemporal evolution mode, and equivalent stiffness of the wellbore-reservoir interface; identifying core mechanical control features by combining the cementation weakening coefficient field and the constitutive model correction factor; and completing stress state analysis based on the disturbance stress amplification coefficient field, the multi-field coupled response characteristic parameter set, and the core mechanical control features.

The present invention discloses a method for inversely calculating the hydrate saturation in sediments by using the thermal conductivity, which includes fabricating a sediment sample containing hydrates, determining the heating time and the temperature rise of the sediment during the heating process through a temperature-measuring and heating probe, multiple groups of temperature-pressure sensor probes, and a constant-current and constant-voltage output device, then calculating to obtain the hydrate state in the sediment, and finally calculating the in-situ hydrate saturation in the sediment by using the hydrate saturation inversion formula. The present invention takes into account the influence of the latent heat of hydrate decomposition phase change when calculating the hydrate thermal conductivity, introduces the hydrate saturation in the sediment into the thermal conductivity calculation, and inversely obtains the in-situ hydrate saturation distribution in the sediment by using the principle that the thermal conductivity obtained by the mixture theory is equivalent to the thermal conductivity measured by the hot wire method. This method realizes the inverse calculation of the saturation distribution in hydrate-containing sediments with phase change based on the thermal principle, providing convenience for the calculation of the hydrate saturation in sediments.

The present invention relates to the technical field of natural gas hydrate mining and submarine carbon dioxide storage, and in particular to a device and method suitable for macroscopic and microscopic research on residual cage structures of hydrates. Its technical solution is: including a gas-liquid injection system, a fluid separation-blocking-unblocking core system, a fluid additional injection core system, a horizontal supercooling flow module, a vertical supercooling flow module and a cage structure microscopic research module. The present invention can efficiently manufacture residual cage structures of hydrates in hydrate decomposition water under high-pressure flow conditions, and then study the mechanism of the effect of residual cage structures on the secondary generation and rapid blockage of hydrates and the effective elimination method of residual cage structures; at the same time, it provides key experimental conditions for molecular-scale microscopic optical research on residual cage structures under high-pressure and low-temperature conditions; in addition, the present invention can also effectively simulate and systematically study hydrate-based submarine carbon dioxide storage technology, providing theoretical support for its engineering application.

The invention discloses a gas-liquid-solid three-phase flow experimental device and method for simulating hydrate decomposition, and belongs to the technical field of natural gas hydrate exploitation. The device comprises a sample preparation system, a hydrate decomposition pipeline, a temperature control system, a fluid injection system, a measuring system and a data collecting and recording system, a pressure gauge is arranged at the hydrate decomposition pipeline outlet; a hydrate sample prepared by the sample preparation system is fed into the hydrate decomposition pipeline; the temperature control system comprises a plurality of layers of heating and cooling coils and a plurality of temperature sensors; the fluid injection system is connected to the bottom of the hydrate decomposition pipeline; the measuring system comprises a plurality of high-speed cameras, an electrical resistance tomography system and an electromagnetic flowmeter; the data collecting and recording system is connected with the temperature control system, the fluid injection system and the measuring system. The multiphase flow process containing hydrate decomposition can be comprehensively and accurately simulated and studied, and the development requirement of a hydrate efficient exploitation technology is met.

This invention belongs to the technical field of natural gas hydrate reservoir exploitation, and relates to a method for determining the control mechanism of hydrate decomposition. This invention utilizes the temperature-pressure driving ratio to determine the control mechanism of hydrate decomposition. The steps are as follows: establishing a hydrate reservoir exploitation model; selecting the temperature and pressure at the point of complete decomposition during the hydrate reservoir exploitation process; calculating the temperature difference driving force and pressure difference driving force of hydrate decomposition based on the temperature and pressure; calculating the temperature difference driving coefficient and pressure difference driving coefficient during hydrate decomposition; and calculating the change in the temperature-pressure driving ratio during hydrate decomposition to determine the control mechanism of hydrate decomposition. This invention selects the point of complete hydrate decomposition for study and uses the temperature-pressure driving ratio to determine the control mechanism of hydrate decomposition. The method is simple and easy to implement, better reflects the control mechanism of hydrate decomposition, and can consider the dynamic changes of the control mechanism during hydrate decomposition at different times, which is the foundation for efficient development of hydrate reservoirs.

This invention belongs to the field of research on the landward distribution boundaries of natural gas hydrates. It discloses a method and system for studying the fate of methane at the landward distribution boundaries of marine natural gas hydrates, including: seismic interpretation and attribute analysis of present-day BSRs; seismic interpretation and attribute extraction of ancient BSRs to calculate their development depths; calculation of the hydrostatic pressure at the time of the ancient BSRs; simulation and prediction of the ancient BSR positions to determine the location of the landward distribution boundaries of the ancient hydrates; demarcation of the main areas of the study area; identification of whether submarine seepage features are present near the landward distribution boundaries of the hydrates, and interpretation of possible vertical and lateral fluid migration pathways and free gas accumulation; determination of the fate of methane at the boundaries and analysis of the main controlling factors; and calculation of the hydrate decomposition zone volume at the landward distribution boundaries of the hydrates based on the positions of the ancient and present BSRs. This invention identifies multiple types of methane fates at the landward distribution boundaries of marine natural gas hydrates, enabling a correct understanding of the environmental impacts of different methane fates and their effects on hydrate reservoirs.

The application discloses a kind of natural gas hydrate core decomposition and transport property prediction method, comprising: constructing core geometric model and carrying out grid division;Chemical kinetics model and transport multiphase percolation model of natural gas hydrate decomposition are constructed;Decomposition chemical kinetics model and transport multiphase percolation model are compiled respectively using C language, and embedded in Fluent software in the form of mass and energy source term;The initial distribution of natural gas hydrate, water, gas three phases in core is inverted, and the initial distribution law of natural gas hydrate is obtained;Based on the initial distribution law of natural gas hydrate, the decomposition and transport property of natural gas hydrate core under different exploitation conditions is predicted using Fluent software.The prediction method fills the blank of existing core natural gas hydrate core decomposition and transport prediction method.

The invention relates to a hydrate granulation purification system and method for removing radionuclides in nuclear wastewater. The system comprises a feeding subsystem, a granulation system and a detection subsystem, the granulation system is provided with a hydration reactor, the feeding subsystem and the granulation system are coupled at the hydration reactor, and the detection subsystem is arranged below the hydration reactor. The feeding subsystem is used for conveying gas raw materials and nuclear wastewater to the hydration reactor through a first gas pipeline and a first liquid pipeline respectively; the granulation system controls the temperature through a first refrigeration pipeline and outputs hydrate granules through a drain valve and a discharge pipeline; the detection subsystem is used for pushing the granules into a hydrate decomposition container for decomposition to obtain decomposed water, and an ion concentration tester is used for detecting the ion concentration so as to characterize the removal effect. The system realizes integrated operation of feeding, granulation and decomposition detection, has functions of fresh water recovery and nuclide removal, has high stability and is convenient for engineering amplification.

The application relates to a natural gas hydrate decomposition process full-coupling numerical simulation method and device, wherein the method comprises the following steps: establishing a mass conservation model, an energy conservation model, a mechanical equilibrium model and a hydrate decomposition model of soil particles, hydrates, gas and water of natural gas hydrates in a decomposition process, constructing a heat-flow-force-chemistry full-coupling model of natural gas hydrates in the decomposition process, taking gas pressure, water pressure, temperature and displacement in different directions as basic unknown quantities of the model, and establishing a finite element weak integral form of the heat-flow-force-chemistry full-coupling model; performing numerical solution on the finite element weak integral form, and assembling a DEHydrate simulator based on a solution result to simulate an evolution trend of reservoir mechanical behavior of natural gas hydrates in the decomposition process. Therefore, the problems that existing hydrate decomposition simulators cannot realize complete coupling among seepage, hydrate phase change, heat transfer and geomechanics are solved.

The invention discloses a hydrate decomposition kinetic model establishment method which comprises the following steps: step 1, experimental design and data acquisition, calculation of a corresponding relation between the amount of undecomposed methane substances and time, and provision of a data basis for model establishment, step 2, establishment of a basic model, step 3, decomposition promotion correction, establishment of a correction model, and step 4, establishment of a hydrate decomposition kinetic model. The enhancement effect of the accelerant on the decomposition rate is quantified; 4, model verification is carried out; based on a Kim-Bishnoi model and a single-stage depressurization decomposition experiment of the methane hydrate, a decomposition kinetic model of the methane hydrate is deduced, the optimal value of the hydrate particle size D0 is determined by optimizing the methane hydrate depressurization decomposition model, fitting correction is conducted on the established model according to the decomposition experiment result, and the methane hydrate particle size D0 is obtained. And determining an optimal value of a parameter B related to the type and the mass concentration of the injection kinetic accelerator.

The application relates to a method for predicting hydrate decomposition rate in a water-in-oil emulsion system. By measuring parameters such as temperature and pressure in the hydrate decomposition stage and bringing them into formula (1) to formula (3), the hydrate decomposition rate in the water-in-oil emulsion system can be effectively predicted. The method has important significance for the research and industrial popularization and application of hydrate solid storage, hydrate solid storage natural gas technology, refrigeration, chemical separation and hydrate freezing blockage risk control in oil and gas pipeline.

The present invention discloses a method for enhancing hydrate production and carbon dioxide storage through dual-horizontal well injection-production coupling, comprising: measuring and confirming target reservoir characteristic data, laying production wells and injection wells at different reservoir depths or in different saturation areas; reducing the reservoir pressure to a set bottom hole pressure through the production well to carry out production; alternately injecting flue gas and a kinetic promoter solution, and controlling the injection rate to maintain the temperature and pressure near the injection well below the methane hydrate phase equilibrium line, displacing natural gas in the pores and stimulating hydrate decomposition; producing to the lower limit of the hydrate saturation for reservoir mechanical safety, and shutting down the production well; if the lower limit is not reached, monitoring the output composition, and shutting down the production well and stopping the alternating injection when a serious CO2 breakthrough occurs or the methane content in the produced gas is lower than a preset lower limit; injecting CO2-rich flue gas or liquid CO2 through the injection well to restore the reservoir pressure to the pre-production pressure, generating a mixed hydrate to solid-state seal CO2, and repairing the reservoir sediment skeleton.

The present application relates to a kind of sea natural gas hydrate wellbore flow security and reservoir protection drilling fluid system and its preparation method and application, belong to deepwater shallow natural gas hydrate exploitation technical field.The drilling fluid system includes the following components: natural seawater, NaCl, KCl, plugging agent, clay hydration inhibitor, filtrate reducer, flow pattern regulator, density control agent, hydrate double-effect inhibitor, hydrate formation inhibitor and hydrate decomposition inhibitor.The drilling fluid system provided by the present application has good rheological filtration performance at room temperature, and the rheological ability meets the production needs at low temperature, while having good clay hydration inhibition performance, which can effectively inhibit reservoir hydrate decomposition and prevent wellbore hydrate secondary generation, prevent well leakage, reduce well control risk and improve work efficiency.

The application relates to the technical field of natural gas safe storage and transportation, and discloses a hydrate decomposition inhibitor, application thereof and a gas storage and transportation method. The hydrate decomposition inhibitor contains an A component and a B component; the A component contains polydimethylsiloxane and a stabilizer; and the B component contains an amino acid promoter and a non-ionic surfactant. Under the premise of guaranteeing the generation rate and gas storage capacity in the hydrate generation stage, the hydrate decomposition inhibitor can significantly reduce the decomposition rate of hydrates under the storage and transportation conditions, improve the stability of the hydrates, and improve the safety of the hydrate storage and transportation technology. The hydrate decomposition inhibitor can also effectively inhibit the gas bubbles generated in the hydrate generation and decomposition process, improve the stability of the hydrates, and improve the hydrate decomposition recovery rate. The hydrate decomposition inhibitor has the characteristics of stable performance, economy and environmental protection, and has a good application prospect in the solid hydrate storage and transportation of natural gas.

The invention relates to a sea area natural gas hydrate wellbore flow guarantee and reservoir protection drilling fluid system and a preparation method and application thereof, and belongs to the technical field of deepwater shallow natural gas hydrate exploitation. The drilling fluid system comprises the following components: natural seawater, NaCl, KCl, a blocking agent, a clay hydration inhibitor, a filtrate reducer, a flow pattern regulator, a density control agent, a hydrate double-effect inhibitor, a hydrate generation inhibitor and a hydrate decomposition inhibitor. The drilling fluid system provided by the invention has good rheological filtration performance at room temperature, the rheological capacity meets production requirements at low temperature, and meanwhile, the drilling fluid system has good clay hydration inhibition performance, can effectively inhibit reservoir hydrate decomposition and prevent secondary generation of wellbore hydrate, can prevent well leakage, reduces well control risks, and has good application prospects. The working efficiency is improved.

The present application relates to natural gas safe storage and transportation technical field, specifically relates to a kind of hydrate promoting composition and its application and gas storage and transportation method.The composition contains neutralizing agent and hydrate formation promoter;Wherein, the neutralizing agent contains component A;The component A is selected from one or more than two of methylcyclohexane, methyl tert-butyl ether, oxidized cyclopentene and tetrahydrofuran-3-ketone.The hydrate promoting composition can still improve the generation rate of hydrate, gas storage capacity and recovery rate in hydrate decomposition recovery stage under the adverse conditions that alcohol and / or salt exist in water source.

The invention provides a discrete element-based simulation method, device and medium for mechanical degradation of hydrate-containing sediment induced by hydrate decomposition, and the simulation method comprises the following steps: carrying out numerical triaxial or biaxial compression test on a hydrate-containing sediment sample, and calibrating mesoscopic parameters associated with a related contact model by combining a trial-and-error method; constructing a mechanical degradation model of the hydrate-containing sediment in the hydrate decomposition process based on discrete elements; in the mechanical degradation model, part of hydrate particles are randomly removed according to a set hydrate decomposition rate to simulate hydrate phase volume reduction, and hydrate cementation damage caused by decomposition is simulated by reducing a parallel cementation radius multiplier. The hydrate phase volume reduction and cementation damage effect are comprehensively considered in the hydrate decomposition process, the mechanical degradation behavior of the hydrate-containing sediment is accurately represented, and the method can be suitable for analyzing the mechanical characteristics of the hydrate-containing sediment with coexisting multiple occurrence forms and can be used for evaluating geological disasters and engineering risks in the hydrate exploitation process.

This invention discloses a gradient-based simulation system and method for methane leakage from natural gas hydrate decomposition, relating to the technical field of marine engineering. The system includes: a hydrate reservoir simulation subsystem to simulate the formation and decomposition of natural gas hydrates in the marine environment; an overlying sedimentary layer simulation subsystem to simulate the migration and transformation of leaked methane within the sedimentary layer; an overlying seawater layer simulation subsystem to simulate the migration and transformation of leaked methane in seawater layers at different depths; a pressure control subsystem to simulate the pressure of the vertical migration process of leaked methane; and a temperature control subsystem to simulate the temperature of the vertical migration process of leaked methane. This invention achieves vertical gradient simulation of temperature and pressure between the various simulation subsystems, ensuring that the simulation processes of each subsystem do not interfere with each other. This solves the problem that existing indoor methane leakage process simulation technologies cannot accurately reproduce the distortion of research results caused by vertical pressure and temperature changes in the in-situ marine environment.