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Mechanical Modeling and Analysis of Stability Deterioration of Production Well During Marine Hydrate Depressurization Production 被引量:1
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作者 SUN Huan-zhao CHANG Yuan-jiang +4 位作者 SUN Bao-jiang WANG Kang CHEN Guo-ming LI Hao DAI Yong-guo 《China Ocean Engineering》 SCIE EI CSCD 2024年第2期338-351,共14页
Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence d... Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence during depressurization,which will destroy the original force state of the production well.However,existing research on the stability of oil and gas production wells assumes the formation to be stable,and lacks consideration of the force exerted on the hydrate production well by formation subsidence caused by hydrate decomposition during production.To fill this gap,this paper proposes an analytical method for the dynamic evolution of the stability of hydrate production well considering the effects of hydrate decomposition.Based on the mechanical model of the production well,the basis for stability analysis has been proposed.A multi-field coupling model of the force state of the production well considering the effect of hydrate decomposition and formation subsidence is established,and a solver is developed.The analytical approach is verified by its good agreement with the results from the numerical method.A case study found that the decomposition of hydrate will increase the pulling-down force and reduce the supporting force,which is the main reason for the stability deterioration.The higher the initial hydrate saturation,the larger the reservoir thickness,and the lower the production pressure,the worse the stability or even instability.This work can provide a theoretical reference for the stability maintaining of the production well. 展开更多
关键词 natural gas hydrate production well depressurization production formation deformation stability deterioration
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Rate-limiting factors in hydrate decomposition through depressurization across various scales:A mini-review
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作者 Xian Sun Peng Xiao +7 位作者 Qinfeng Shi Lingban Wang Zhenbin Xu Yuhao Bu Xiaohui Wang Yifei Sun Changyu Sun Guangjin Chen 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第3期206-219,共14页
Natural gas hydrate is an energy resource for methane that has a carbon quantity twice more than all traditional fossil fuels combined.However,their practical application in the field has been limited due to the chall... Natural gas hydrate is an energy resource for methane that has a carbon quantity twice more than all traditional fossil fuels combined.However,their practical application in the field has been limited due to the challenges of long-term preparation,high costs and associated risks.Experimental studies,on the other hand,offer a safe and cost-effective means of exploring the mechanisms of hydrate dissociation and optimizing exploitation conditions.Gas hydrate decomposition is a complicated process along with intrinsic kinetics,mass transfer and heat transfer,which are the influencing factors for hydrate decomposition rate.The identification of the rate-limiting factor for hydrate dissociation during depressurization varies with the scale of the reservoir,making it challenging to extrapolate findings from laboratory experiments to the actual exploitation.This review aims to summarize current knowledge of investigations on hydrate decomposition on the subject of the research scale(core scale,middle scale,large scale and field tests)and to analyze determining factors for decomposition rate,considering the various research scales and their associated influencing factors. 展开更多
关键词 Gas hydrate Rate-limiting factors Research scale depressurization DECOMPOSITION
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Enhanced gas production and CO_(2) storage in hydrate-bearing sediments via pre-depressurization and rapid CO_(2) injection
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作者 Hongnan Chen Yifei Sun +5 位作者 Bojian Cao Minglong Wang Ming Wang Jinrong Zhong Changyu Sun Guangjin Chen 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第3期126-134,共9页
Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades.Exploring an efficient CO_(2) storage method can significantly reduce CO_(2) emissions in the short term.In t... Carbon emission reduction and clean energy development are urgent demands for mankind in the coming decades.Exploring an efficient CO_(2) storage method can significantly reduce CO_(2) emissions in the short term.In this study,we attempted to construct sediment samples with different residual CH_(4) hydrate amounts and reservoir conditions,and then investigate the potentials of both CO_(2) storage and enhanced CH_(4) recovery in depleted gas hydrate deposits in the permafrost and ocean zones,respectively.The results demonstrate that CO_(2) hydrate formation rate can be significantly improved due to the presence of residual hydrate seeds;However,excessive residual hydrates in turn lead to the decrease in CO_(2) storage efficiency.Affected by the T-P conditions of the reservoir,the storage amount of liquid CO_(2) can reach 8 times that of gaseous CO_(2),and CO_(2) stored in hydrate form reaches 2-4 times.Additionally,we noticed two other advantages of this method.One is that CO_(2) injection can enhance CH_(4) recovery rate and increases CH_(4) recovery by 10%-20%.The second is that hydrate saturation in the reservoir can be restored to 20%-40%,which means that the solid volume of the reservoir avoids serious shrinkage.Obviously,this is crucial for protecting the goaf stability.In summary,this approach is greatly promising for high-efficient CO_(2) storage and safe exploitation of gas hydrate. 展开更多
关键词 HYDRATE depressurization CO_(2) storage CH_(4) production Reservoir remediation
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Numerical Simulation on Production Trials by Using Depressurization for Typical Marine Hydrate Reservoirs:Well Type and Formation Dip
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作者 QIN Fanfan SUN Jiaxin +4 位作者 GU Yuhang CAO Xinxin MAO Peixiao NING Fulong JIANG Guosheng 《Journal of Ocean University of China》 SCIE CAS CSCD 2024年第3期661-675,共15页
Natural gas hydrate has huge reserves and is widely distributed in marine environment.Its commercial development is of great significance for alleviating the contradiction between energy supply and demand.As an effici... Natural gas hydrate has huge reserves and is widely distributed in marine environment.Its commercial development is of great significance for alleviating the contradiction between energy supply and demand.As an efficient research method,numerical simulation can provide valuable insights for the design and optimization of hydrate development.However,most of the current production models simplify the reservoir as a two-dimensional(2D)horizontal layered model,often ignoring the impact of formation dip angle.To improve the accuracy of production prediction and provide theoretical support for the optimization of production well design,two three-dimensional(3D)geological models with different dip angles based on the geological data from two typical sites are constructed.The vertical well,horizontal well and multilateral wells are deployed in these reservoirs with different permeabilities to perform production trial,and the sensitivity analysis of dip angles is also carried out.The short-term production behaviors in high and low permeability reservoirs with different dip angles are exhibited.The simulation results show that 1)the gas and water production behaviors for different well types in the two typical reservoirs show obviously different variation laws when the short-term depressurization is conducted in the inclined formation;2)the inclined formation will reduce the gas production and increase the water extraction,and the phenomena becomes pronounced as the dip angle increases,particularly in the low-permeability reservoirs;3)and the impact of formation dip on hydrate recovery does not change significantly with the variation of well type. 展开更多
关键词 natural gas hydrate inclined formation depressurization production well type
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Influences of pore fluid on gas production from hydrate-bearing reservoir by depressurization 被引量:1
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作者 Yi-Fei Sun Bo-Jian Cao +6 位作者 Hong-Nan Chen Yin-Long Liu Jin-Rong Zhong Liang-Liang Ren Guang-Jin Chen Chang-Yu Sun Dao-Yi Chen 《Petroleum Science》 SCIE EI CAS CSCD 2023年第2期1238-1246,共9页
In addition to the temperature and pressure conditions,the pore fluid composition and migration behavior are also crucial to control hydrate decomposition in the exploitation process.In this work,to investigate the ef... In addition to the temperature and pressure conditions,the pore fluid composition and migration behavior are also crucial to control hydrate decomposition in the exploitation process.In this work,to investigate the effects of these factors,a series of depressurization experiments were carried out in a visible one-dimensional reactor,using hydrate reservoir samples with water saturations ranging from 20%to 65%.The results showed a linear relationship between gas production rates and gas saturations of the reservoir,suggesting that a larger gas-phase space was conducive to hydrate decomposition and gas outflow.Therefore,the rapid water production in the early stage of hydrate exploitation could release more gas-phase space in the water-rich reservoir,which in turn improved the gas production efficiency.Meanwhile,the spatiotemporal evolution of pore fluids could lead to partial accelerated decomposition or secondary formation of hydrates.In the unsealed reservoir,the peripheral water infiltration kept reservoir at a high water saturation,which hindered the overall production process and caused higher water production.Importantly,depressurization assisted with the N2 sweep could displace the pore water rapidly.According to the results,it is recommended that using the short-term N2 sweep as an auxiliary means in the early stage of depressurization to expand the gas-phase space in order to achieve the highest production efficiency. 展开更多
关键词 CH4 hydrate Water saturation depressurization Gas-phase space N2 sweep
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Hydraulic modeling and optimization of jet mill bit considering the characteristics of depressurization and cuttings cleaning
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作者 Tong Cao Xu-Yue Chen +1 位作者 Kai-An Yu Lin Tang 《Petroleum Science》 SCIE EI CSCD 2023年第5期3085-3099,共15页
A jet mill bit(JMB)is proposed to increase the drilling efficiency and safety of horizontal wells,which has the hydraulic characteristics of depressurization and cuttings cleaning.This paper fills the gap in the hydra... A jet mill bit(JMB)is proposed to increase the drilling efficiency and safety of horizontal wells,which has the hydraulic characteristics of depressurization and cuttings cleaning.This paper fills the gap in the hydraulic study of the JMB by focusing on the hydraulic modeling and optimization of the JMB and considering these two hydraulic characteristics.First,the hydraulic depressurization model and the hydraulic cuttings cleaning model of the JMB are developed respectively.In the models,the pressure ratio and efficiency are chosen as the evaluation parameters of the depressurization capacity of the JMB,and the jet hydraulic power and jet impact force are chosen as the evaluation parameters of cuttings cleaning capacity of the JMB.Second,based on the hydraulic models,the effects of model parameters[friction loss coefficient,target inclination angle,rate of penetration(ROP),flow ratio,and well depth]on the hydraulic performance of the JMB are investigated.The results show that an increase in the friction loss coefficient and target inclination angle cause a significant reduction in the hydraulic depressurization capacity,and the effect of ROP is negligible.The flow ratio is positively related to the hydraulic cuttings cleaning capacity,and the well depth determines the maximum hydraulic cuttings cleaning capacity.Finally,by combining the hydraulic depressurization model and hydraulic cuttings cleaning model,an optimization method of JMB hydraulics is proposed to simultaneously maximize the jet depressurization capacity and the cuttings cleaning capacity.According to the drilling parameters given,the optimal values of the drilling fluid flow rate,backward nozzle diameter,forward nozzle diameter,and throat diameter can be determined.Moreover,a case study is conducted to verify the effectiveness of the optimization method. 展开更多
关键词 Jet mill bit Hydraulic depressurization model Hydraulic cuttings cleaning model Parametric study Hydraulic optimization
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Dissociation characteristics of methane hydrate using depressurization combined with thermal stimulation 被引量:6
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作者 Mingjun Yang Zhanquan Ma +1 位作者 Yi Gao Lanlan Jiang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2019年第9期2089-2098,共10页
Methane hydrate is considered as a potential energy source in the future due to its abundant reserves and high energy density.To investigate the influence of initial hydrate saturation,production pressure,and the temp... Methane hydrate is considered as a potential energy source in the future due to its abundant reserves and high energy density.To investigate the influence of initial hydrate saturation,production pressure,and the temperature of thermal stimulation on gas production rate and cumulative gas production percentage,we conducted the methane hydrate dissociation experiments using depressurization,thermal stimulation and a combination of two methods in this study.It is found that when the gas production pressures are the same,the higher the hydrate initial saturation,the greater change in hydrate reservoir temperature.Therefore,it is easier to appear the phenomenon of icing and hydrate reformation when the hydrate saturation is higher.For example,the reservoir temperature dropped to below zero in depressurization process when the hydrate saturation was about 37%.However,the same phenomenon didn’t appear as the saturation was about 12%.This may be due to more free gas in the reservoir with hydrate saturated of 37%.We also find that the temperature variation of reservoir can be reduced effectively by combination of depressurization and thermal stimulation method.And the average gas production rate is highest with combined method in the experiments.When the pressure of gas production is 2 MPa,compared with depressurization,the average of gas production can increase 54%when the combined method is used.The efficiency of gas production is very low when thermal stimulation was used alone.When the temperature of thermal stimulation is 11℃,the average rate of gas production in the experiment of thermal stimulation is less than 1/3 of that in the experiment of the combined method. 展开更多
关键词 METHANE HYDRATE depressurization Thermal STIMULATION DISSOCIATION characteristics
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Decomposition behaviors of methane hydrate in porous media below the ice melting point by depressurization 被引量:3
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作者 Yu Zhang Tian Wang +3 位作者 Xiaosen Li Kefeng Yan Yi Wang Zhaoyang Chen 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2019年第9期2207-2212,共6页
The decomposition behaviors of methane hydrate below the ice melting point in porous media with different particle size and different pore size were studied.The silica gels with the particle size of 105–150μm,150–... The decomposition behaviors of methane hydrate below the ice melting point in porous media with different particle size and different pore size were studied.The silica gels with the particle size of 105–150μm,150–200μm and 300–450μm,and the mean pore diameters of 12.95 nm,17.96 nm and 33.20 nm were used in the experiments.Methane recovery and temperature change curves were determined for each experiment.The hydrate decomposition process in the experiments can be divided into the depressurization period and the isobaric period.The temperature in the system decreases quickly in the depressurization process with the hydrate decomposition and reaches the lowest point in the isobaric period.The hydrate decomposition in porous media below ice-melting point is very fast and no self-perseveration effect is observed.The hydrate decomposition is influenced both by the driving force and the initial hydrate saturation.In the experiments with the high hydrate saturation,the hydrate decomposition will stop when the pressure reaches the equilibrium dissociation pressure.The stable pressure in the experiment with high hydrate saturation exceeds the equilibrium dissociation pressure of bulk hydrate and increases with the decrease of the pore size. 展开更多
关键词 METHANE HYDRATE depressurization POROUS media Decomposition ICE-MELTING point
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The simulation of gas production from oceanic gas hydrate reservoir by the combination of ocean surface warm water flooding with depressurization 被引量:4
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作者 Hao Yang Yu-Hu Bai Qing-Ping Li 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2012年第5期1287-1295,共9页
A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal, salt ... A new method is proposed to produce gas from oceanic gas hydrate reservoir by combining the ocean surface warm water flooding with depressurization which can efficiently utilize the synthetic effects of thermal, salt and depressurization on gas hydrate dissociation. The method has the advantage of high efficiency, low cost and enhanced safety. Based on the proposed conceptual method, the physical and mathematical models are established, in which the effects of the flow of multiphase fluid, the kinetic process of hydrate dissociation, the endothermic process of hydrate dissociation, ice-water phase equilibrium, salt inhibition, dispersion, convection and conduction on the hydrate disso- ciation and gas and water production are considered. The gas and water rates, formation pressure for the combination method are compared with that of the single depressurization, which is referred to the method in which only depres- surization is used. The results show that the combination method can remedy the deficiency of individual producing methods. It has the advantage of longer stable period of high gas rate than the single depressurization. It can also reduce the geologic hazard caused by the formation defor- mation due to the maintaining of the formation pressure by injected ocean warm water. 展开更多
关键词 Gas hydrate reservoir Ocean surface warmwater flooding depressurization Numerical simulation Combination exploitation
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Numerical studies of hydrate dissociation and gas production behavior in porous media during depressurization process 被引量:4
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作者 Xuke Ruan Mingjun Yang +2 位作者 Yongchen Song Haifeng Liang Yanghui Li 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2012年第4期381-392,共12页
In this study, a numerical model is developed to investigate the hydrate dissociation and gas production in porous media by depressurization. A series of simulation runs are conducted to study the impacts of permeabil... In this study, a numerical model is developed to investigate the hydrate dissociation and gas production in porous media by depressurization. A series of simulation runs are conducted to study the impacts of permeability characteristics, including permeability reduction exponent, absolute permeability, hydrate accumulation habits and hydrate saturation, sand average grain size and irreducible water saturation. The effects of the distribution of hydrate in porous media are examined by adapting conceptual models of hydrate accumulation habits into simulations to govern the evolution of permeability with hydrate decomposition, which is also compared with the conventional reservoir permeability model, i.e. Corey model. The simulations show that the hydrate dissociation rate increases with the decrease of permeability reduction exponent, hydrate saturation and the sand average grain size. Compared with the conceptual models of hydrate accumulation habits, our simulations indicate that Corey model overpredicts the gas production and the performance of hydrate coating models is superior to that of hydrate filling models in gas production, which behavior does follow by the order of capillary coating〉pore coating〉pore filling〉capillary filling. From the analysis of tl/2, some interesting results are suggested as follows: (1) there is a "switch" value (the "switch" absolute permeability) for laboratory-scale hydrate dissociation in porous media, the absolute permeability has almost no influence on the gas production behavior when the permeability exceeds the "switch" value. In this study, the "switch" value of absolute permeability can be estimated to be between 10 and 50 md. (2) An optimum value of initial effective water saturation Sw,e exists where hydrate dissociation rate reaches the maximum and the optimum value largely coincides with the value of irreducible water saturation Swr,e. For the case of Sw,e〈,Swr,e, or Sw,e〉Swr,e, there are different control mechanisms dominating the process of hydrate dissociation and gas production. 展开更多
关键词 gas hydrate numerical simulation PERMEABILITY DISSOCIATION gas production depressurization
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2-D Numerical Simulation of Natural Gas Hydrate Decomposition Through Depressurization by Fully Implicit Method 被引量:4
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作者 宋永臣 梁海峰 《China Ocean Engineering》 SCIE EI 2009年第3期529-542,共14页
Natural gas hydrate, as a potential energy resource, deposits in permafrost and marine sediment with large quantities. The current exploitation methods include depressurization, thermal stimulation, and inhibitor inje... Natural gas hydrate, as a potential energy resource, deposits in permafrost and marine sediment with large quantities. The current exploitation methods include depressurization, thermal stimulation, and inhibitor injection. However, many issues have to be resolved before the commercial production. In the present study, a 2-D axisymmetric simulator for gas production from hydrate reservoirs is developed. The simulator includes equations of conductive and convective heat transfer, kinetic of hydrate decomposition, and multiphase flow. These equations are discretized based on the finite difference method and are solved with the fully implicit simultaneous solution method. The process of laboratory-scale hydrate decomposition by depressurization is simulated. For different surrounding temperatures and outlet pressures, time evolutions of gas and water generations during hydrate dissociation are evaluated, and variations of temperature, pressure, and multiphase fluid flow conditions are analyzed. The results suggest that the rate of heat transfer plays an important role in the process. Furthermore, high surrounding temperature and low outlet valve pressure may increase the rate of hydrate dissociation with insignificant impact on final cumulative gas volume. 展开更多
关键词 natural gas hydrate depressurization fully implicit simuhaneoas solution method impact parameters analysis
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Numerical Study of Gas Production from a Methane Hydrate Reservoir Using Depressurization with Multi-wells 被引量:2
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作者 SHANG Shilong GU Lijuan LU Hailong 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2021年第3期928-936,共9页
With the implementation of the production tests in permafrost and offshore regions in Canada,US,Japan,and China,the study of natural gas hydrate has progressed into the stage of technology development for industrial e... With the implementation of the production tests in permafrost and offshore regions in Canada,US,Japan,and China,the study of natural gas hydrate has progressed into the stage of technology development for industrial exploitation.The depressurization method is considered as a better strategy to produce gas from hydrate reservoirs based on production tests and laboratory experiments.Multi-well production is proposed to improve gas production efficiency,to meet the requirement for industrial production.For evaluating the applicability of multi-well production to hydrate exploitation,a 2D model is established,with numerical simulations of the performance of the multi-well pattern carried out.To understand the dissociation behavior of gas hydrate,the pressure and temperature distributions in the hydrate reservoir are specified,and the change in permeability of reservoir sediments is investigated.The results obtained indicate that multi-well production can improve the well connectivity,accelerate hydrate dissociation,enhance gas production rate and reduce water production as compared with single-well production. 展开更多
关键词 oil and gas upstream unconventional resources natural gas hydrate numerical simulation depressurization
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Sediment permeability change on natural gas hydrate dissociation induced by depressurization 被引量:4
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作者 Lei Wang Li-juan Gu Hai-long Lu 《China Geology》 2020年第2期221-229,共9页
The permeability of a natural gas hydrate reservoir is a critical parameter associated with gas hydrate production.Upon producing gas from a hydrate reservoir via depressurization,the permeability of sediments changes... The permeability of a natural gas hydrate reservoir is a critical parameter associated with gas hydrate production.Upon producing gas from a hydrate reservoir via depressurization,the permeability of sediments changes in two ways with hydrate dissociation,increasing with more pore space released from hydrate and decreasing due to pore compression by stronger effective stress related to depressurization.In order to study the evolution of sediment permeability during the production process with the depressurization method,an improved pore network model(PNM)method is developed to establish the permeability change model.In this model,permeability change induced by hydrate dissociation is investigated under hydrate occurrence morphology of pore filling and grain coating.The results obtained show that hydrate occurrence in sediment pore is with significant influence on permeability change.Within a reasonable degree of pore compression in field trial,the effect of pore space release on the reservoir permeability is greater than that of pore compression.The permeability of hydrate containing sediments keeps increasing in the course of gas production,no matter with what hydrate occurrence in sediment pore. 展开更多
关键词 Natural gas hydrate Reservoir sediment PERMEABILITY Pore network model depressurization Oil gas exploration engineering South China Sea China
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Investigation of the methane hydrate surface area during depressurization-induced dissociation in hydrate-bearing porous media 被引量:1
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作者 Xuke Ruan Xiao-Sen Li 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2021年第4期324-334,共11页
The surface area of hydrate during dissociation in porous media is essentially important for the kinetics of hydrate dissociation.In this study,the methane hydrate surface area was investigated by the comparison resul... The surface area of hydrate during dissociation in porous media is essentially important for the kinetics of hydrate dissociation.In this study,the methane hydrate surface area was investigated by the comparison results of experiments and numerical simulations during hydrate decomposition in porous media.The experiments of methane hydrate depressurizationinduced dissociation were performed in a 1D high pressure cell filled with glass beads,an improved and valid 1D corescale numerical model was developed to simulate gas production.Two conceptual models for hydrate dissociation surface area were proposed based on the morphology of hydrate in porous media,which formed the functional form of the hydrate dissociation surface area with porosity,hydrate saturation and the average radius of sand sediment particles.With the establishment of numerical model for depressurizationinduced hydrate dissociation in porous media,the cumulative gas productions were modeling and compared with the experimental data at the different hydrate saturations.The results indicated that the proposed prediction equations are valid for the hydrate dissociation surface area,and the graincoating surface area model performs well at lower hydrate saturation for hydrate dissociation simulation,whereas at higher hydrate saturation,the hydrate dissociation simulation from the porefilling surface area model is more reasonable.Finally,the sensitivity analysis showed that the hydrate dissociation surface area has a significant impact on the cumulative gas production. 展开更多
关键词 Surface area Methane hydrate Hydrate dissociation Hydrate morphology depressurization
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Numerical and experimental investigation on the depressurization capacity of a new type of depressure-dominated jet mill bit 被引量:1
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作者 Xu-Yue Chen Tong Cao +3 位作者 Kai-An Yu De-Li Gao Jin Yang Hong-Shu Wei 《Petroleum Science》 SCIE CAS CSCD 2020年第6期1602-1615,共14页
Efficient cuttings transport and improving rate of penetration(ROP)are two major challenges in horizontal drilling and extended reach drilling.A type of jet mill bit(JMB)may provide an opportunity to catch the two bir... Efficient cuttings transport and improving rate of penetration(ROP)are two major challenges in horizontal drilling and extended reach drilling.A type of jet mill bit(JMB)may provide an opportunity to catch the two birds with one stone:not only enhancing cuttings transport efficiency but also improving ROP by depressuring at the bottom hole.In this paper,the JMB is further improved and a new type of depressure-dominated JMB is presented;meanwhile,the depressurization capacity of the depressure-dominated JMB is investigated by numerical simulation and experiment.The numerical study shows that low flow-rate ratio helps to enhance the depressurization capacity of the depressure-dominated JMB;for both depressurization and bottom hole cleaning concern,the flow-rate ratio is suggested to be set at approximately 1:1.With all other parameter values being constant,lower dimensionless nozzle-to-throat-area ratio may result in higher depressurization capacity and better bottom hole cleaning,and the optimal dimensionless nozzle-to-throat-area ratio is at approximately0.15.Experiments also indicate that reducing the dimensionless flow-rate ratio may help to increase the depressurization capacity of the depressure-dominated JMB.This work provides drilling engineers with a promising tool to improve ROP. 展开更多
关键词 Horizontal drilling Jet mill bit Bottom hole depressurization Bottom hole flow field Rate of penetration
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Stability analysis of seabed strata and casing structure during the natural gas hydrates exploitation by depressurization in horizontal wells in South China Sea 被引量:1
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作者 Peng-fei Xie Lin Yang +7 位作者 Qian-yong Liang Xu-hui Zhang Liang-hua Zhang Bin Zhang Xiao-bing Lu Hui-ce He Xue-min Wu Yi-fei Dong 《China Geology》 2022年第2期300-309,共10页
Natural gas hydrates(NGHs)are a new type of clean energy with great development potential.However,it is urgent to achieve safe and economical NGHs development and utilization.This study established a physical model of... Natural gas hydrates(NGHs)are a new type of clean energy with great development potential.However,it is urgent to achieve safe and economical NGHs development and utilization.This study established a physical model of the study area using the FLAC^(3D) software based on the key parameters of the NGHs production test area in the South China Sea,including the depressurization method,and mechanical parameters of strata,NGHs occurrence characteristics,and the technological characteristics of horizontal wells.Moreover,this study explored the law of influences of the NGHs dissociation range on the stability of the overburden strata and the casing structure of a horizontal well.The results are as follows.With the dissociation of NGHs,the overburden strata of the NGHs dissociation zone subsided and formed funnelshaped zones and then gradually stabilized.However,the upper interface of the NGHs dissociation zone showed significant redistribution and discontinuity of stress.Specifically,distinct stress concentration and corresponding large deformation occurred in the build-up section of the horizontal well,which was thus prone to suffering shear failure.Moreover,apparent end effects occurred at the end of the horizontal well section and might cause the deformation and failure of the casing structure.Therefore,it is necessary to take measures in the build-up section and at the end of the horizontal section of the horizontal well to prevent damage and ensure the wellbore safety in the long-term NGHs exploitation. 展开更多
关键词 Natural gas hydrates(NGHs) Exploitation by depressurization Horizontal well Stratum subsidence Shear failure NGHs exploration trial engineering Oil and gas exploration engineering Shenhu Area South China Sea
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Gas Production from Offshore Methane Hydrate Layer and Seabed Subsidence by Depressurization Method 被引量:1
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作者 Hiroki Matsuda Takafumi Yamakawa +1 位作者 Yuichi Sugai Kyuro Sasaki 《Engineering(科研)》 2016年第6期353-364,共12页
Numerical simulations on consolidation effects have been carried out for gas production from offshore methane hydrates (MH) layers and subsidence at seafloor. MH dissociation is affected by not only MH equilibrium lin... Numerical simulations on consolidation effects have been carried out for gas production from offshore methane hydrates (MH) layers and subsidence at seafloor. MH dissociation is affected by not only MH equilibrium line but also consolidation (mechanical compaction) depended on depressurization in the MH reservoir. Firstly, to confirm present model on consolidation with effective stress, the history matching on gas production and consolidation has been done to the experimental results using with synthetic sand MH core presented by Sakamoto et al. (2009). In addition, the comparisons of numerical simulation results of present and Kurihara et al. (2009) were carried out to check applicability of present models for gas production from MH reservoir in field scale by depressurization method. The delays of pressure propagation in the MH reservoir and elapsed time at peak gas production rate were predicted by considering consolidation effects by depressurization method. Finally, seabed subsidence during gas production from MH reservoirs was numerically simulated. The maximum seabed subsidence has been predicted to be roughly 0.5 to 2 m after 50 days of gas production from MH reservoirs that elastic modulus is 400 to 100 MPa at MH saturation = 0. 展开更多
关键词 Methane Hydrate Offshore Gas Production CONSOLIDATION SUBSIDENCE depressurization
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RELAP5 Code Study of ROSA/LSTF Experiments on PWR Safety System Using Steam Generator Secondary-Side Depressurization 被引量:1
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作者 Takeshi Takeda Akira Ohnuki Hiroaki Nishi 《Journal of Energy and Power Engineering》 2015年第5期426-442,共17页
RELAP5 (reactor excursion and leak analysis program, version 5) code analyses were performed on two ROSA/LSTF (rig of safety assessment/large scale test facility) experiments on PWR (pressurized water reactor) s... RELAP5 (reactor excursion and leak analysis program, version 5) code analyses were performed on two ROSA/LSTF (rig of safety assessment/large scale test facility) experiments on PWR (pressurized water reactor) safety system that simulated cold leg small-break loss-of-coolant accidents with 8-in. or 4-in. diameter break using SG (steam generator) secondary-side depressurization. The SG depressurization was initiated by fully opening the depressurization valves in both SGs immediately after a safety injection signal. In the 8-in. break test, loop seal clearing occurred and then core uncovery and heatup took place by core boil-off. Core collapsed liquid level recovered after the initiation of accumulator coolant injection, and long-term core cooling was ensured by the actuation of low-pressure injection system. In the 4-in. break test, on the other hand, there was no core uncovery and heatup due to smaller break flow rate than in the 8-in. break test. Adjustment of Cd (break discharge coefficient) for two-phase discharge flow predicted the break flow rate reasonably well. The code well predicted the overall trend of the major thermal-hydraulic response observed in the two LSTF tests by the Cd adjustment. The code, however, overpredicted the peak cladding temperature because of underprediction of the core collapsed liquid level due to inadequate prediction of the accumulator flow rate in the 8-in. break case. 展开更多
关键词 PWR safety system ROSAILSTF small-break loss-of-coolant accident SG depressurization RELAP5 code.
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HYDRODYNAMIC CHARACTERISTICS OF THE PROCESS OF DEPRESSURIZATION OF SATURATED WATER
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作者 王立新 欧阳藩 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 1994年第4期28-35,共8页
Experiments were carried out to find the effects of dissolved gas pressure,liquid flow rateand nozzle geometry on the bubble generation when saturated water was depressurized through anozzle.A new method,high speed ca... Experiments were carried out to find the effects of dissolved gas pressure,liquid flow rateand nozzle geometry on the bubble generation when saturated water was depressurized through anozzle.A new method,high speed camera system was developed to measure the generated microbubblesdynamically.On the basis of the laws of ideal gas and solution,theoretical generated gas flow ratewas deduced,while the Smoluchowski′s equation was applied to describe the kinetics of bubblenucleation.It was found that the size distribution of nucleated bubbles was of skewed distribution.An explanation to this phenomenon was made and the Gamma function distribution was employedfor mathematical simulation.The results show good agreement between the experimental data and thepredictions by proposed model. 展开更多
关键词 BUBBLE GENERATION BUBBLE SIZE DISTRIBUTION depressurization of saturated WATER
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Influence of depressurization rate on gas production capacity of high-rank coal in the south of Qinshui Basin, China
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作者 SU Xuefeng LIU Yan +3 位作者 CUI Zhouqi ZHANG Jianguo YU Li WANG Kai 《Petroleum Exploration and Development》 2019年第3期642-650,共9页
A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of D... A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher. 展开更多
关键词 Qinshui Basin Fanzhuang BLOCK Zhengzhuang BLOCK high-rank COAL depressurization RATE gas production RATE simulation experiment gas production capacity
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