An efficient data-driven global sensitivity analysis method of shale gas production through convolutional neural network

The shale gas development process is complex in terms of its flow mechanisms and the accuracy of the production forecasting is influenced by geological parameters and engineering parameters.Therefore,to quantitatively evaluate the relative importance of model parameters on the production forecasting performance,sensitivity analysis of parameters is required.The parameters are ranked according to the sensitivity coefficients for the subsequent optimization scheme design.A data-driven global sensitivity analysis(GSA)method using convolutional neural networks(CNN)is proposed to identify the influencing parameters in shale gas production.The CNN is trained on a large dataset,validated against numerical simulations,and utilized as a surrogate model for efficient sensitivity analysis.Our approach integrates CNN with the Sobol'global sensitivity analysis method,presenting three key scenarios for sensitivity analysis:analysis of the production stage as a whole,analysis by fixed time intervals,and analysis by declining rate.The findings underscore the predominant influence of reservoir thickness and well length on shale gas production.Furthermore,the temporal sensitivity analysis reveals the dynamic shifts in parameter importance across the distinct production stages.

Analysis of sensitivity to hydrate blockage risk in natural gas gathering pipeline

During the operational process of natural gas gathering and transmission pipelines,the formation of hydrates is highly probable,leading to uncontrolled movement and aggregation of hydrates.The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines,resulting in production reduction,shutdowns,and pressure build-ups.Consequently,a cascade of risks is prone to occur.To address this issue,this study focuses on the operational process of natural gas gathering and transmission pipelines,where a comprehensive framework is established.This framework includes theoretical models for pipeline temperature distribution,pipeline pressure distribution,multiphase flow within the pipeline,hydrate blockage,and numerical solution methods.By analyzing the influence of inlet temperature,inlet pressure,and terminal pressure on hydrate formation within the pipeline,the sensitivity patterns of hydrate blockage risks are derived.The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate,potentially mitigating pipeline blockage during natural gas transportation.Furthermore,an increase in inlet temperature and terminal pressure,and a decrease in inlet pressure,results in a displacement of the most probable location for hydrate blockage towards the terminal station.However,it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system,contradicting the operational goal of energy efficiency and reduction of energy consumption.Consequently,for high-pressure gathering pipelines,measures such as raising the inlet temperature or employing inhibitors,electrical heat tracing,and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation.Moreover,considering abnormal conditions such as gas well production and pipeline network shutdowns,which could potentially trigger hydrate formation,the installation of methanol injection connectors remains necessary to ensure production safety.

Sensitivity Analysis of P-Waves and S-Waves to Gas Hydrate in the Shenhu Area Using OBS

Compared to towed streamers, ocean-bottom seismometers(OBS) obtain both S-wave data and richer wavefield information. In this paper, the induced polarization method is used to conduct wavefield separation on OBS data obtained from the Shenhu area in the South China Sea. A comparison of the changes in P-and S-waves, and a comprehensive analysis of geological factors within the area, enable analysis and description of the occurrence of natural gas hydrate in the study area. Results show an increase in P-wave velocity when natural gas hydrate exists in the formation, whereas the S-wave velocity remains almost constant, as S-waves can only propagate through the rock skeleton. Therefore, the bottom-simulating reflection(BSR) response of the P-wave is better than that of the S-wave in the frequency analysis profile. In a wide-angle section, the refractive wave of the hydrate layer is evident when using P-wave components but identification is difficult with S-wave components. This velocity model illustrates the sensitivity of Pand S-wave components to gas hydrate. The use of this polarization method and results of analysis provide technical and theoretical support for research on hydrate deposits and other geological features in the Shenhu area.

A First-principles Study on the Gas Sensitivity of Metal-loaded Graphene with an Atomic Vacancy to O_2

In this work, adsorption energies, geometrical and electronic structures for adsorption systems of O_2 at metal-loaded graphene(M-Gra) and metal-loaded defective graphene(M-D-Gra)(M = Ni, Pd, Pt and Al) surfaces are studied using a GGA-PW91 method. Calculated results show that loaded M make the interaction between O_2 and the graphene surface change from physical to chemical adsorptions, band gaps of M-Gra systems after the O_2 adsorption change, and the Ni-loaded Gra has the highest sensitivity to O_2. For O_2-M-D-Gra systems, interactions between O_2 and the M-D-Gra surfaces are chemical, similar to the O_2-M-Gra systems, and loaded Pt and Al have the strongest effect on the sensitivity of D-Gra to O_2. The M loads at the perfect Gra and D-Gra surfaces make the interactions between O_2 and the surfaces have obvious charge transfer. This work would provide a valuable guidance on the gas sensitivity study of graphene to O_2.

Prediction of immiscible gas flooding performance:a modified capacitance-resistance model and sensitivity analysis

Reservoir performance prediction is one of the main steps during a field development plan.Due to the complexity and time-consuming aspects of numerical simulators,it is helpful to develop analytical tools for a rapid primary analysis.The capacitance-resistance model(CRM)is a simple technique for reservoir management and optimization.This method is an advanced time-dependent material balance equation which is combined with a productivity equation.CRM uses production/injection data and bottom-hole pressure as inputs to build a reliable model,which is then combined with the oil-cut model and converted to a predictive tool.CRM has been studied thoroughly for water flooding projects.In this study,a modified model for gas flooding systems based on gas density and average reservoir pressure is developed.A detailed procedure is described in a synthetic reservoir model using a genetic algorithm.Then,a streamline simulation is implemented for validation of the results.The results show that the proposed model is able to calculate interwell connectivity parameters and oil production rates.Moreover,a sensitivity analysis is carried out to investigate effects of drawdown pressure and gas PVT properties on the new model.Finally,acceptable ranges of input data and limitations of the model are comprehensively discussed.

Stress sensitivity of formation during multi-cycle gas injection and production in an underground gas storage rebuilt from gas reservoirs

Permeability sensitivity to stress experiments were conducted on standard core samples taken from Wen 23 Gas Storage at multi-cycle injection and production conditions of the gas storage to study the change pattern of stress sensitivity of permeability.A method for calculating permeability under overburden pressure in the multi-cycle injection and production process was proposed,and the effect of stress sensitivity of reservoir permeability on gas well injectivity and productivity in UGS was analyzed.Retention rate of permeability decreased sharply first and then slowly with the increase of the UGS cycles.The stress sensitivity index of permeability decreased with the increase of cycle number of net stress variations in the increase process of net stress.The stress sensitivity index of permeability hardly changed with the increase of cycle number of net stress variations in the decrease process of net stress.With the increase of cycle number of net stress variation,the stress sensitivity index of permeability in the increase process of net stress approached that in the decrease process of net stress.The lower the reservoir permeability,the greater the irreversible permeability loss rate,the stronger the cyclic stress sensitivity,and the higher the stress sensitivity index of the reservoir,the stronger the reservoir stress sensitivity.The gas zones with permeability lower than 0.3’10-3 mm2 are not suitable as gas storage regions.Stress sensitivity of reservoir permeability has strong impact on gas well injectivity and productivity and mainly in the first few cycles.

Improvement in Sensitivity and Recovery of Single-Walled Carbon Nanotube-Based Gas Sensors

In this paper,an improvement in sensitivity and recovery of the single-walled carbon nanotube (SWNT)-based gas sensors was reported.The sensors were fabricated from SWNT powder by a screen-printing method,followed by annealing for 2 h in open-air at various temperatures.The Raman spectra of the SWNT bundles and the response to ammonia (NH_3) exposure of the sensors indicated that the annealing at a relevant temperature improved the sensor sensitivity.The sensor annealed at 200℃exhibited a high sensitivity in NH_3 detection.After 20 min of exposure to NH_3 at room temperature,the resistance of the sensor increased up to 12% in comparison with its initial value.By evacuating combined with maintaining the flux of carrier gas at 300 sccm,the sensor recovery was significantly speeded.The sensor resistance retrieved to its initial value after only 25 min degassing. These results would be considered in the development of the SWNT-based gas sensors.

The Study on the Gas Sensitivity of the One-Dimensional ZnO

One-dimensional (1D) ZnO was prepared through hydrothermal synthesis by cetyltrimethylammonium bromide (CTAB) controling its morphology.The products were characterized by X-ray diffraction (XRD),transmission electron microscopy (TEM) and scanning electron microscopy (SEM).The sintered gas sensor was prepared using ZnO nanorods and its gas sensitivity was measured in static gas atmosphere.The result showed that the ZnO nanorods had lower working temperature than granulated ZnO and had very good sensitivity to 10μg/g trimethylamine (TMA),methanol,ammonia, acetone and ethanol at the working temperature of 170℃.SEM picture revealed that there were many multi-pores in the surface of the sensors.These multi-pores might help to absorb gases and improve the gas sensitivity.

Neck-controlled sensitivity study on nano-grain SnO_2 gas sensors

The electrical potential inside a cylinder with a space charge layer is used to express the neck potential barrier of nano-SnO2 gas elements, and the neck-controlled sensitivity and the grain size effect are studied. It is shown that the sensing properties are influenced by the microstructural features, such as the grain size, the geometry and connectivity between grains, and that the neck controlled sensitivity alone is higher than the neck-grain controlled sensitivity and the difference between the neck controlled sensitivity and the neck-grain controlled sensitivity is large in the high sensitivity range for nano-SnO2 gas elements, which suggests a possible approach to the improvement of the sensitivity of a sensor by decreasing the number of necks of a nano-grain SnO2 gas element.

Gas Sensitivity of Poly (3, 4-ethylene dioxythiophene) Prepared by a Modified LB Film Method

An arachidic acid/poly （3, 4-ethylene dioxythiophene） （AA/PEDOT） multilayer Langmuir-Blodgett （LB） film was prepared by a modified LB film method. The theories were utilized to explain the effects between HCl molecule and LB film. The gas sensitivity mechanism of poly （3, 4-ethylene dioxythiophene） （PEDOT） multilayer film can be explained by the charge transfer between p system of PEDOT and oxidization HCl system. The gas sensitivity of PEDOT LB film deposited interdigital electrode to HCl was tested. The results showed that film thickness, treating temperature, deposition speed had different influence on film gas sensitivity. The AA/PEDOT film deposited device exhibited nonlinear behavior to HCl gas at lower concentration （20-60 ppm） and linear response behavior at higher gas concentration was observed. The time of the compound LB film of the AA/PEDOT responding to the 30 ppm HCl gas is about 20 seconds, which is far quicker than the time of the film to the PEDOTPRESS film（about 80 seconds）. It is not higher film press to better film. When the film press attains 45 mNs/m, the sensitivity of the AA/PEDOT film on the contrary descends.

GAS6-AS1调节miR-370-3p/SPATA2轴对卵巢癌细胞增殖、迁移、侵袭、凋亡和EMT的影响

目的:探讨长链非编码RNA GAS6反义RNA1(long non-coding RNA GAS6 antisense RNA1, lncRNA GAS6-AS1)调节miR-370-3p/精子发生相关蛋白2 (spermatogenesis-associated protein 2, SPATA2)轴对卵巢癌细胞增殖、迁移、侵袭、凋亡和上皮间质转化(epithelial mesenchymal transformation, EMT)的影响。方法:qRT-PCR、Western blot分别检测癌旁组织、卵巢癌组织、人正常卵巢上皮细胞IOSE80及卵巢癌细胞系HO-8910、SKOV3、A2780中GAS6-AS1、miR-370-3p及SPATA2蛋白表达。将SKOV3细胞分为:对照组(NC组)、 si-NC组、si-GAS6-AS1组、mimic NC组、miR-370-3p mimic组、si-GAS6-AS1+inhibitor NC组、si-GAS6-AS1+miR-370-3p inhibitor组,qRT-PCR检测细胞中GAS6-AS1、miR-370-3p表达;CCK-8法检测细胞增殖;流式细胞术检测细胞凋亡;划痕愈合实验检测细胞迁移;Transwell实验检测细胞侵袭;Western blot检测SPATA2、细胞周期素D1(CyclinD1)、Bcl-2相关X蛋白(Bcl-2-associated X,Bax)、E-钙黏蛋白(E-cadherin)、波形蛋白(Vimentin)、神经钙黏蛋白(N-cadherin)表达;双荧光素酶报告基因实验检测GAS6-AS1与miR-370-3p、 miR-370-3p与SPATA2的关系。结果:在卵巢癌组织和细胞中GAS6-AS1、SPATA2蛋白高表达,miR-370-3p低表达,且在SKOV3细胞中GAS6-AS1、SPATA2蛋白表达量最高,miR-370-3p表达水平最低,因此,选择SKOV3细胞为后续研究对象。与NC组、si-NC组比较,si-GAS6-AS1组GAS6-AS1、OD450值(24 h、48 h、72 h)、划痕愈合率、侵袭细胞数、SPATA2、CyclinD1、Vimentin、N-cadherin蛋白表达降低,miR-370-3p表达、细胞凋亡率、Bax、E-cadherin蛋白表达升高(P<0.05);与NC组、mimic NC组比较,miR-370-3p mimic组OD450值(24 h、48 h、72 h)、划痕愈合率、侵袭细胞数、SPATA2、CyclinD1、Vimentin、N-cadherin蛋白表达降低,miR-370-3p表达、细胞凋亡率、Bax、E-cadherin蛋白表达升高(P<0.05);miR-370-3p inhibitor减弱了沉默GAS6-AS1对SKOV3细胞增殖、迁移、侵袭及EMT的抑制及对细胞凋亡的促进作用。GAS6-AS1与miR-370-3p、miR-370-3p与SPATA2存在靶向调控关系。结论:沉默GAS6-AS1通过上调miR-370-3p来抑制SPATA2表达,从而抑制SKOV3细胞增殖、迁移、侵袭及EMT,并促进细胞凋亡。

Numerical Study on Dissociation of Gas Hydrate and Its Sensitivity to Physical Parameters

The natural gas hydrate resource is tremendous. How to utilize the gas from hydrates safely is researchers＇ concern. In this paper, a one-dimensional model is developed to simulate the hydrate dissociation by depressurization in hydratebearing porous medinm. This model can De used to explain the effects of the flow of multiphase fluids, the endothermie process of hydrate dissociation, the variation of permeability, the convection and conduction on the hydrate dissociation. Numerical results show that the hydrate dissociation can be divided into three stages： a rapid dissociation stage mainly governed by hydrate dissociation kinetics after an initially slow dissociation stage governed mainly by flow, and finally a slow dissociation stage. Moreover, a numerical approach of sensitivity analysis of physical parameters is proposed, with which the quantitative effect of all the parameters on hydrate dissociation can be evaluated conveniently.

lncRNA GAS5调控miR-452-5p/Mcl-1通路对急性肺损伤大鼠肺组织细胞焦亡的影响

目的探讨长链非编码RNA生长抑制特异因子5(lncRNA GAS5)调控miR-452-5p/髓样细胞白血病序列-1(Mcl-1)通路对急性肺损伤(ALI)大鼠肺组织细胞焦亡的影响。方法取SD大鼠随机分成6组(每组10只):对照组、模型组、pUC57-lncRNA GAS5组、miR-452-5p抑制剂组、pUC57-NC+miR-452-5p-NC组、pUC57-lncRNA GAS5+miR-452-5p激活剂组。模型组和各干预组大鼠以腹腔注射脂多糖的方法构建ALI模型,对照组大鼠腹腔注射等量生理盐水,造模同时进行分组干预。然后检测大鼠肺功能,比较各组用力肺活量(FVC)、0.3秒用力呼气容积(FEV0.3)/FVC、潮气量(VT);HE染色观察大鼠肺组织病理损伤,并以Holfbauer评分评估其损伤程度;酶联免疫吸附法(ELISA)测定大鼠肺泡灌洗液(BALF)和血清炎症因子白细胞介素(IL)-18、IL-1β水平;免疫印迹法检测大鼠肺组织焦亡相关指标[消皮素D(GSDMD)、核苷酸结合寡聚化结构域样受体蛋白3(NLRP3)、天冬氨酸特异性半胱氨酸蛋白酶(Caspase)-1、Caspase-11]及Mcl-1蛋白表达;实时荧光定量PCR检测大鼠肺组织lncRNA GAS5、miR-452-5p及Mcl-1表达;双荧光素酶报告基因实验验证大鼠肺泡上皮细胞L2中lncRNA GAS5对miR-452-5p的靶向调节。结果与对照组比较,模型组大鼠FVC、FEV0.3/FVC、lncRNA GAS5表达、Mcl-1蛋白及mRNA表达降低(均P<0.05),VT、Holfbauer评分、IL-18及IL-1β水平、GSDMD、NLRP3、Caspase-1及Caspase-11蛋白表达、miR-452-5p表达升高(均P<0.05)。与模型组比较,pUC57-lncRNA GAS5组、miR-452-5p抑制剂组大鼠FVC、FEV0.3/FVC、Mcl-1蛋白及mRNA表达均升高(均P<0.05),VT、Holfbauer评分、IL-18及IL-1β水平、GSDMD、NLRP3、Caspase-1及Caspase-11蛋白表达、miR-452-5p表达均降低(均P<0.05);pUC57-NC+miR-452-5p-NC组大鼠各指标无显著差异(均P>0.05)。与pUC57-lncRNA GAS5组比较,pUC57-lncRNA GAS5+miR-452-5p激活剂组大鼠FVC、FEV0.3/FVC、Mcl-1蛋白及mRNA表达降低(均P<0.05),VT、Holfbauer评分、IL-18及IL-1β水平、GSDMD、NLRP3、Caspase-1及Caspase-11蛋白表达、miR-452-5p表达升高(均P<0.05)。结论lncRNA GAS5可通过靶向下调miR-452-5p而促进Mcl-1表达,进而抑制ALI大鼠炎症反应及肺组织细胞焦亡,最终减轻大鼠肺损伤并改善其肺功能。

Enhancing recovery and sensitivity studies in an unconventional tight gas condensate reservoir

The recovery factor from tight gas reservoirs is typically less than 15%, even with multistage hydrauhc tractunng stimulation. Such low recovery is exacerbated in tight gas condensate reservoirs, where the depletion of gas leaves the valuable condensate behind. In this paper, three enhanced gas recovery （EGR） methods including produced gas injection, CO2 injection and water injection are investigated to increase the well productivity for a tight gas condensate reservoir in the Montney Formation, Canada. The production performance of the three EGR methods is compared and their economic feasibility is evaluated. Sensitivity analysis of the key factors such as primary production duration, bottom-hole pressures, and fracture conductivity is conducted and their effects on the well production performance are analyzed. Results show that, compared with the simple depletion method, both the cumulative gas and condensate production increase with fluids injected. Produced gas injection leads to both a higher gas and condensate production compared with those of the CO2 injection, while waterflooding suffers from injection difficulty and the corresponding low sweep efficiency. Meanwhile, the injection cost is lower for the produced gas injection due to the on-site available gas source and minimal transport costs, gaining more economic benefits than the other EGR methods.

Multi-factor sensitivity analysis on the stability of submarine hydrate-bearing slope

There are many factors affecting the instability of the submarine hydrate-bearing slope (SHBS),and the interaction with hydrate is very complicated.In this paper,the mechanical mechanism of the static liquefaction and instability of submarine slope caused by the dissociation of natural gas hydrate (NGH) resulting in the rapid increase of pore pressure of gas hydrate-bearing sediments (GHBS) and the decrease of effective stress are analyzed based on the time series and type of SHBS.Then,taking the typical submarine slope in the northern South China Sea as an example,four important factors affecting the stability of SHBS are selected,such as the degree of hydrate dissociation,the depth of hydrate burial,the thickness of hydrate,and the depth of seawater.According to the principle of orthogonal method,25 orthogonal test schemes with 4 factors and 5 levels are designed and the safety factors of submarine slope stability of each scheme are calculated by using the strength reduction finite element method.By means of the orthogonal design range analysis and the variance analysis,sensitivity of influential factors on stability of SHBS are obtained.The results show that the degree of hydrate dissociation is the most sensitive,followed by hydrate burial depth,the thickness of hydrate and the depth of seawater.Finally,the concept of gas hydrate critical burial depth is put forward according to the influence law of gas hydrate burial depth,and the numerical simulation for specific submarine slope is carried out,which indicates the existence of critical burial depth.

Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations

Emulsifier-free poly（methyl methacrylate-styrene） [P（MMA-St）] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcoholwater medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive mono- mer N-isopropylacrylamide （NIPAm） and hydrophilic monomer acrylic acid （AA） onto the surface of P（MMA- St） nanospheres at 80 ℃, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures （LCST）, were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD- SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability

LncRNA GAS5通过miR-182-5p/FOXF2轴对口腔鳞状细胞癌细胞增殖、凋亡、迁移及侵袭的影响

目的探讨长链非编码RNA生长停滞特异性转录本5(LncRNA GAS5)调节微小RNA-182-5p(miR-182-5p)/叉头盒蛋白F2(FOXF2)对口腔鳞状细胞癌(OSCC)细胞增殖、迁移、侵袭及凋亡的影响。方法收集45例确诊为OSCC的癌组织以及癌旁组织,体外培养人口腔上皮细胞系HOEC及人OSCC细胞系CAL-27、HSC-3、SCC-25,qRT-PCR检测组织、细胞中LncRNA GAS5、miR-182-5p、FOXF2的表达;择细胞株CAL-27分为ctrl组、pcDNA组、pcDNA-GAS5组、pcDNA-GAS5+miR-NC组及pcDNA-GAS5+miR-182-5p mimics组,采用CCK-8试剂盒检测细胞增殖活性,Transwell实验检测细胞迁移和侵袭能力,流式细胞术检测细胞凋亡水平,Western Blot检测癌细胞中FOXF2、bax、Bcl-2、cleaved caspase-3及E-cadherin蛋白表达,双萤光素酶报告实验验证miR-182-5p与LncRNA GAS5、FOXF2的关系。结果与癌旁组织相比,OSCC组织中LncRNA GAS5、FOXF2 mRNA表达降低,miR-182-5p表达升高(P<0.05);CAL-27、HSC-3、SCC-25细胞与HOEC相比,LncRNA GAS5、miR-182-5p、FOXF2表达趋势与OSCC组织内一致,且在CAL-27表达最明显,选择其作为后续实验的细胞株;与ctrl组、pcDNA组比较,pcDNA-GAS5组CAL-27细胞中GAS5、FOXF2 mRNA、细胞凋亡率及BAX、E-cadherin蛋白表达升高(P<0.05),miR-182-5p表达、细胞增殖、迁移和侵袭数及Bcl-2蛋白表达降低(P<0.05);上调miR-182-5p可减弱过表达LncRNA GAS5对CAL-27细胞增殖、迁移和侵袭的抑制作用,也可抑制癌细胞凋亡;LncRNA GAS5靶向负调控miR-182-5p表达,miR-182-5p靶向负调控FOXF2表达。结论上调GAS5可能通过抑制miR-182-5p来增加FOXF2表达,进而抑制CAL-27细胞增殖、迁移及侵袭,促进CAL-27细胞的凋亡。

PREPARATION OF CAPACITIVE-TYPE CO_2 GASSENSITIVE ELEMENT USING NANOMETER POWDERS

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Sensitivity Analysis of Multi-phase Seepage Parameters Affecting the Clayey Silt Hydrate Reservoir Productivity in the Shenhu Area,South China Sea

Natural gas hydrate(NGH)is an important future resource for the 21st century and a strategic resource with potential for commercial development in the third energy transition.It is of great significance to accurately predict the productivity of hydrate-bearing sediments(HBS).The multi-phase seepage parameters of HBS include permeability,porosity,which is closely related to permeability,and hydrate saturation,which has a direct impact on hydrate content.Existing research has shown that these multi-phase seepage parameters have a great impact on HBS productivity.Permeability directly affects the transmission of pressure-drop and discharge of methane gas,porosity and initial hydrate saturation affect the amount of hydrate decomposition and transmission process of pressure-drop,and also indirectly affect temperature variation of the reservoir.Considering the spatial heterogeneity of multi-phase seepage parameters,a depressurization production model with layered heterogeneity is established based on the clayey silt hydrate reservoir at W11 station in the Shenhu Sea area of the South China Sea.Tough+Hydrate software was used to calculate the production model;the process of gas production and seepage parameter evolution under different multi-phase seepage conditions were obtained.A sensitivity analysis of the parameters affecting the reservoir productivity was conducted so that:(a)a HBS model with layered heterogeneity can better describe the transmission process of pressure and thermal compensation mechanism of hydrate reservoir;(b)considering the multi-phase seepage parameter heterogeneity,the influence degrees of the parameters on HBS productivity were permeability,porosity and initial hydrate saturation,in order from large to small,and the influence of permeability was significantly greater than that of other parameters;(c)the production potential of the clayey silt reservoir should not only be determined by hydrate content or seepage capacity,but also by the comprehensive effect of the two;and(d)time scales need to be considered when studying the effects of changes in multi-phase seepage parameters on HBS productivity.

Rate transient analysis methods for water-producing gas wells in tight reservoirs with mobile water

Tight gas reservoirs with mobile water exhibit multi-phase flow and high stress sensitivity.Accurately analyzing the reservoir and well parameters using conventional single-phase rate transient analysis methods proves challenging.This study introduces novel rate transient analysis methods incorporating evaluation processes based on the conventional flowing material balance method and the Blasingame type-curve method to examine fractured gas wells producing water.By positing a gas-water two-phase equivalent homogenous phase that considers characteristics of mobile water,gas,and high stress sensitivity,the conventional single-phase rate transient analysis methods can be applied by integrating the phase's characteristics and defining the phase's normalized parameters and material balance pseudotime.The rate transient analysis methods based on the equivalent homogenous phase can be used to quantitatively assess the parameters of wells and gas reservoirs,such as original gas-in-place,fracture half-length,reservoir permeability,and well drainage radius.This facilitates the analysis of production dynamics of fractured wells and well-controlled areas,subsequently aiding in locating residual gas and guiding the configuration of well patterns.The specific evaluation processes are detailed.Additionally,a numerical simulation mechanism model was constructed to verify the reliability of the developed methods.The methods introduced have been successfully implemented in field water-producing gas wells within tight gas reservoirs containing mobile water.