The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir s...The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir seepage capacity but also influence effective productivity and subsequent fracturing reconstruction.Given the diverse mechanical behaviors,such as migration,penetration,or fracture arrest,traditional assumptions about fracture interaction criteria fail to address this complexity.To resolve these issues,a global cohesive element method is proposed to model random natural fractures.This approach verifies intersection models based on real-time stress conditions rather than pre-set criteria,enabling better characterization of interactions between hydraulic and natural fractures.Research has shown that the elastic modulus,horizontal stress difference,and fracturing fluid pumping rate significantly promote the expansion of hydraulic fractures.The use of low viscosity fracturing fluid can observe a decrease in the width of fractures near the wellbore,which may cause fractures to deflect when interacting with natural fractures.However,simulations under these conditions did not form a“complex network of fractures”.It is worth noting that when the local stress difference is zero,the result is close to the formation of this network.Excessive spacing will reduce the interaction between fractures,resulting in a decrease in the total length of fractures.By comprehensively analyzing these factors,an optimal combination can be identified,increasing the likelihood of achieving a“complex fracture network”.This paper thoroughly investigates hydraulic fracture propagation in naturally fractured reservoirs under various conditions,offering insights for developing efficient fracturing methods.展开更多
The deep coal reservoir in Linxing-Shenfu block of Ordos Basin is an important part of China’s coalbed methane resources.In the process of reservoir reconstruction,the artificial fracture morphology of coal seam with...The deep coal reservoir in Linxing-Shenfu block of Ordos Basin is an important part of China’s coalbed methane resources.In the process of reservoir reconstruction,the artificial fracture morphology of coal seam with gangue interaction is significantly different,which affects the efficient development of coalbed methane resources in this area.In this paper,the surface outcrop of Linxing-Shenfu block is selected,and three kinds of interaction modes between gangue and coal seam are set up,including single-component coal rock sample,coal rock sample with different thicknesses of gangue layer and coal rock sample with different numbers of gangue.Through true triaxial physical simulation and three-dimensional discrete element numerical simulation,the lawof artificial fracture initiation and propagation in multi-gangue interaction coal seam is analyzed in depth,and the hydraulic fracture initiation and propagation mode under different interaction modes of gangue layer in Linxing-Shenfu deep coal reservoir was clarified.The research shows that the initiation of artificial fractures in a single coal seam is affected by geologicalengineering factors.The maximum principal stress dominates the direction of fracture propagation,and the stress difference controls the fracture morphology.When the stress difference is 2 MPa,the fracture morphology is complex,which is easy to connect to the weak surface of coal and rock cleat,and the fracturemorphology of the stress difference is mainly a single main fracture.After the thickness of the gangue layer is increased from 2 to 5 cm,it is difficult for the artificial fracture to penetrate the layer vertically after the fracture initiation,and the effective transformation area of the reservoir is limited.The more the number of gangue layers,the greater the hydraulic energy consumption in the process of fracture propagation,and the more difficult the fracture propagation.展开更多
The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or...The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.展开更多
The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester ro...The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.展开更多
With the rapid development of deepwater drilling operations,more and more complex technical challenges have to be faced due to the rigorous conditions encountered.One of these challenges is that the drilling fluid use...With the rapid development of deepwater drilling operations,more and more complex technical challenges have to be faced due to the rigorous conditions encountered.One of these challenges is that the drilling fluid used must had good rheological properties at low temperatures and high ability to inhibit hydrate formation.Synthetic drilling fluid has been widely applied to deepwater drilling operations due to its high penetration rate,excellent rheological properties,good ability to prevent hydrate formation,and high biodegradability.A synthetic drilling fluid formulation was developed in our laboratory.The rheological properties of this drilling fluid at low temperatures （0-20 °C） were tested with a 6-speed viscometer and its ability to inhibit hydrate formation was evaluated at 20 MPa CH 4 gas and 0 °C by differential scanning calorimetry （DSC）.Several factors influencing the low temperature rheological properties of this synthetic drilling fluid were studied in this paper.These included the viscosity of the base fluid,the amount of CEMU and organic clay,and the water volume fraction.展开更多
The paper overviews the research and application of silicate plugging agent, according to the different mechanisms and application forms, the plugging agent is divided into silicate gel, silicate precipitation, silica...The paper overviews the research and application of silicate plugging agent, according to the different mechanisms and application forms, the plugging agent is divided into silicate gel, silicate precipitation, silicate/polymer, silicate/surfactant, silicate gel/foam and so on. This paper chiefly introduces the conception, mechanism and development tendency of the different systems mentioned above. The development tendency manifests as fully utilize personal properties and cooperate with other plugging agents or technologies, including the study of reaction mechanism, combination of plugging agent, grasping water flood timing, developing deep profile control and water shutoff technology, combining with other measures (chemicals huff and puff), in order to play the role of such blocking agents, further enhance oil recovery.展开更多
Offshore oil and gas production has become an important growth pole to ensure national energy security.However,China's offshore oil and gas production is lack of key core technologies and weak in tool and equipmen...Offshore oil and gas production has become an important growth pole to ensure national energy security.However,China's offshore oil and gas production is lack of key core technologies and weak in tool and equipment foundation and can hardly support the optimized fast development of important fields.To solve these technological difficulties,China National Offshore Oil Corporation(CNOOC)insisted on independent technological innovation and overcame a series of key core technologies through theoretical research and key technology research and test during the 13th Five-Year Plan.And the following research results are obtained.First,several key technologies are broken through,including efficient drilling and completion in the middle and deep layers of the Bohai Sea,offshore large-scale heavy oil thermal recovery,deep-water oil and gas field development,and high temperature and high pressure well drilling and completion in the South China Sea,unconventional oil and gas stimulation,and offshore emergency rescue.Domestic first independently operated ultra deep water giant gas field,namely“Deepsea 1”is successfully put into production,so that the leap from 300 m to 1500 m of water depth and from exploration to development is realized.Second,key tools and equipment are developed,such as logging while drilling and rotary steering drilling system,deep-water drilling surface conductor,underwater emergency killing device,and underwater wellhead Christmas tree,which promote the high-quality development of China's offshore oil industry.Finally,some suggestions are proposed as follows.In the future,CNOOC shall strengthen independent technological innovation,quicken the pace to deepsea oil and gas,and continue to research key core technologies for oil and gas reserves and production increase(e.g.continuous localization of drilling and completion technologies,equipment and materials in complex fields),commingled gas production and test and green energy transformation(e.g.geothermal energy),so as to make greater contributions to ensure national energy security and build a maritime power.展开更多
To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fract...To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.展开更多
1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2...1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.展开更多
Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrat...Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrating outcrop,core,drilling,logging and 3D seismic data,to systematically analyze the characteristics of the source,transport pathway,and sink during the deposition of Lingshui Formation,and reveal the patterns,controlling factors and petroleum geologic significance of the source-to-sink systems.The results are obtained in five aspects.First,during the fault-depression transition,the Qiongdongnan Basin received sediments from the provenances presenting as segments in east-west and zones in north-south,primarily with the Indosinian granites in the Shenhu Uplift in the east and the Yanshanian granites in the west.Overall,the sources are young in the southern and northern parts and old in the interior of the basin.Second,three types of sediment transport pathways are identified:paleo-valleys,fault troughs and trough-valley transitional zones.Third,based on differences in sediment supply modes,the unique source-to-sink systems during the fault-depression transition in marine rift basins are categorized into three types:exogenous,endogenous and composite.Fourth,the characteristics of these source-to-sink systems are primarily controlled by provenance,paleogeomorphology,and sea-level changes.Provenance lithology and scale dictated the composition and volume of sedimentary deposits.Paleogeomorphology influenced erosion intensity in the provenance and the development of paleodrainage systems,thereby affecting the distribution and types of sedimentary systems.Additionally,sea-level changes decided the extent of the provenance,but also regulated the sediment distribution patterns through oceanic processes such as waves and tides.Fifth,the exogenous source-to-sink systems may form large-scale reservoir bodies,the endogenous systems develop secondary pores due to presence of soluble minerals,and the composite systems demonstrate reservoir properties varying from area to area.展开更多
Saline aquifers are considered as highly favored reservoirs for CO_(2)sequestration due to their favorable properties.Understanding the impact of saline aquifer properties on the migration and distribution of CO_(2)pl...Saline aquifers are considered as highly favored reservoirs for CO_(2)sequestration due to their favorable properties.Understanding the impact of saline aquifer properties on the migration and distribution of CO_(2)plume is crucial.This study focuses on four key parameters-permeability,porosity,formation pressure,and temperature-to characterize the reservoir and analyse the petrophysical and elastic response of CO_(2).First,we performed reservoir simulations to simulate CO_(2)saturation,using multiple sets of these four parameters to examine their significance on CO_(2)saturation and the plume migration speed.Subsequently,the effect of these parameters on the elastic properties is tested using rock physics theory.We established a relationship of compressional wave velocity(V_(p))and quality factor(Q_(p))with the four key parameters,and conducted a sensitivity analysis to test their sensitivity to V_(p) and Q_(p).Finally,we utilized visco-acoustic wave equation simulated time-lapse seismic data based on the computed V_(p) and Q_(p) models,and analysed the impact of CO_(2) saturation changes on seismic data.As for the above nu-merical simulations and analysis,we conducted sensitivity analysis using both homogeneous and heterogeneous models.Consistent results are found between homogeneous and heterogeneous models.The permeability is the most sensitive parameter to the CO_(2)saturation,while porosity emerges as the primary factor affecting both Q_(p) and V_(p).Both Q_(p) and V_(p) increase with the porosity,which contradicts the observations in gas reservoirs.The seismic simulations highlight significant variations in the seismic response to different parameters.We provided analysis for these observations,which serves as a valuable reference for comprehensive CO_(2)integrity analysis,time-lapse monitoring,injection planning and site selection.展开更多
Mitigating vortex-induced vibrations(VIV)in flexible risers represents a critical concern in offshore oil and gas production,considering its potential impact on operational safety and efficiency.The accurate predictio...Mitigating vortex-induced vibrations(VIV)in flexible risers represents a critical concern in offshore oil and gas production,considering its potential impact on operational safety and efficiency.The accurate prediction of displacement and position of VIV in flexible risers remains challenging under actual marine conditions.This study presents a data-driven model for riser displacement prediction that corresponds to field conditions.Experimental data analysis reveals that the XGBoost algorithm predicts the maximum displacement and position with superior accuracy compared with Support vector regression(SVR),considering both computational efficiency and precision.Platform displacement in the Y-direction demonstrates a significant positive correlation with both axial depth and maximum displacement magnitude.The fourth point displacement exhibits the highest contribution to model prediction outcomes,showing a positive influence on maximum displacement while negatively affecting the axial depth of maximum displacement.Platform displacement in the X-and Y-directions exhibits competitive effects on both the riser’s maximum displacement and its axial depth.Through the implementation of XGBoost algorithm and SHapley Additive exPlanation(SHAP)analysis,the model effectively estimates the riser’s maximum displacement and its precise location.This data-driven approach achieves predictions using minimal,readily available data points,enhancing its practical field applications and demonstrating clear relevance to academic and professional communities.展开更多
During drilling operations,the low resolution of seismic data often limits the accurate characterization of small-scale geological bodies near the borehole and ahead of the drill bit.This study investigates high-resol...During drilling operations,the low resolution of seismic data often limits the accurate characterization of small-scale geological bodies near the borehole and ahead of the drill bit.This study investigates high-resolution seismic data processing technologies and methods tailored for drilling scenarios.The high-resolution processing of seismic data is divided into three stages:pre-drilling processing,post-drilling correction,and while-drilling updating.By integrating seismic data from different stages,spatial ranges,and frequencies,together with information from drilled wells and while-drilling data,and applying artificial intelligence modeling techniques,a progressive high-resolution processing technology of seismic data based on multi-source information fusion is developed,which performs simple and efficient seismic information updates during drilling.Case studies show that,with the gradual integration of multi-source information,the resolution and accuracy of seismic data are significantly improved,and thin-bed weak reflections are more clearly imaged.The updated seismic information while-drilling demonstrates high value in predicting geological bodies ahead of the drill bit.Validation using logging,mud logging,and drilling engineering data ensures the fidelity of the processing results of high-resolution seismic data.This provides clearer and more accurate stratigraphic information for drilling operations,enhancing both drilling safety and efficiency.展开更多
Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an...Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.展开更多
The deep layer has become an important replacement field for oil and gas exploration,but the formation mechanism of effective reservoirs is unknown,and the distribution of dessert reservoirs is difficult to predict,wh...The deep layer has become an important replacement field for oil and gas exploration,but the formation mechanism of effective reservoirs is unknown,and the distribution of dessert reservoirs is difficult to predict,which seriously affects the discovery of deep resources.In this paper,the reservoir of the first and second members of the Shahejie Formation in the Caofeidian 6-4S area of the Bozhong Depression is taken as an example.Through the comprehensive means such as well-seismic calibration,denudation recovery,source-sink quantitative coupling,basin simulation,microscopic observation,X-ray diffraction,inclusion and thermodynamic analysis,the reservoir formation mechanism of dissolution pores and the favorable area distribution of thermodynamic prediction of dissolution reaction in the study area are carried out.The results show that the dissolution pores are the dominant type,accounting for more than 80%of the total pores.The dissolution reaction between soluble minerals such as feldspar accumulated in the near source and acidic fluids such as organic acids formed in the adjacent strata is the main mechanism for the development of dissolution pores.The organic matter in the adjacent strata is controlled by temperature and pressure during the burial evolution process to form organic acids,and migrates to the adjacent reservoirs for selective dissolution under the action of pressure and other driving forces.The characteristics of thermodynamic parameters(ΔG,which can determine whether feldspar is dissolved)and kinetic parameters(R,indicating the degree of feldspar dissolution)of feldspar dissolution reaction show that the thermodynamic parameters of feldspar dissolution are positively correlated with temperature,and the kinetic parameters are correlated with the concentration of organic acid discharge.The results of thermodynamic and kinetic parameters are coupled with provenance-sedimentary facies-diagenetic facies,and it is predicted that the plane area of TypeⅠfavorable area is 50 km^(2),and the plane area of TypeⅡfavorable area is 62.4 km2.This method provides theoretical reference and method guidance for the prediction of favorable reservoir distribution of deep clastic rocks,and has a good application prospect.展开更多
Based on the survey of saline lacustrine shales in the Permian Lucaogou Formation and Fengcheng Formation in the Junggar Basin,it is found that the sweet intervals of these shale oil strata are enriched with lithium.I...Based on the survey of saline lacustrine shales in the Permian Lucaogou Formation and Fengcheng Formation in the Junggar Basin,it is found that the sweet intervals of these shale oil strata are enriched with lithium.In certain intervals,lithium contents reach up to 700μg/g,with produced water concentrations estimated to 517.2μg/g—an underexplored resource with considerable potential that has yet to receive adequate attention.The sedimentary environment,depositional process,and geochemical characteristics of these intervals were analyzed,indicating that lithium enrichment in saline lacustrine shale is controlled by multiple factors during deposition and diagenesis.The salinity of lake water during sedimentation plays a key role in lithium accumulation,with lithium primarily concentrated in carbonate-rich intervals,and diagenesis further affects its distribution.To assess the potential for lithium co-production in shale oil development,future research should be based on the enrichment mechanisms of lithium and hydrocarbons in lacustrine shales,predict the distribution patterns of oil and lithium-rich intervals,and evaluate the economic feasibility of an“oil-lithium integrated sweet spot”.Efficient lithium extraction and environmental protection technologies need to be explored to optimize resource development.Saline lacustrine shale oil development not only ensures stable oil and gas supplies but also,if lithium co-production is realized,could enhance China’s lithium security,contributing significantly to the country’s energy transformation.展开更多
Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhyd...Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhydraulic-mechnical(THM)coupled fracture propagation model relying on the phase field method to simulate thermal shock-induced fracturing in the deep shale considering dynamic temperature conditions.The validity of this model is confirmed through comparison of experimental and numerical results concerning the THM-coupled stress field and thermal cracking.Special attention is paid to the interaction of thermal shock-induced fractures in deep shale that contains weak planes.The results indicate that thermal shock-induced stress significantly amplifies the tensile stress range and deteriorates rock strength,resulting in a multi-point failure pattern within a fracture.The thermal shock damage degree is closely related to the fracture cooling efficiency,suggesting that considering downhole temperature conditions in THM-coupled fracture stress field calculations is advisable.Thermal shock can activate pre-existing natural fractures and enhance the penetration ability of hydraulic fractures,thereby leading to a fracture network.展开更多
A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for...A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.展开更多
The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the t...The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the transported substance may undergo phase transitions between solid,liquid,or gas states during dissociation and hydration processes.To effectively predict hydrate dissociation performance influenced by multi-field coupling processes,this study proposes a novel bond-based peridynamic coupled finite difference model that accounts for gas-liquid two-phase seepage behavior.The developed peridynamic(PD)model simulates hydrate dissociation reactions accompanied by gas-liquid seepage,mass transfer,and heat transfer phenomena.The formulation demonstrates strong agreement with established analytical solutions for one-dimensional problems and finite element transient solutions for two-dimensional problems in the literature,validating the accuracy and reliability of the newly constructed model.This research presents an innovative approach to simulate heat transport and multiphase flow phenomena associated with hydrate dissociation.展开更多
In order to develop a marine engineering material with excellent mechanical properties and corrosion resistance,a novel non-equiatomic Co_(1.5)CrFeNi_(1.5)Ti_(0.6)high-entropy alloy(HEA)was fabricated through mechanic...In order to develop a marine engineering material with excellent mechanical properties and corrosion resistance,a novel non-equiatomic Co_(1.5)CrFeNi_(1.5)Ti_(0.6)high-entropy alloy(HEA)was fabricated through mechanical alloying and spark plasma sintering.The results revealed that the sintering temperature significantly affected the microstructure and phase composition of the HEA owing to the diffusion rate,homogenization,and sluggish diffusion effect of metal atoms.At sintering temperatures below 1050℃,HEA mainly consisted of face-centered cubic(FCC),Ni_(3)Ti(ε),Ni_(2.67)Ti_(1.33)(R),and Fe-Cr(σ)phases.The microstructure of alloy comprised coarse dendritic crystals,whose content and size gradually decreased with increasing sintering temperature.However,the HEA sintered above 1100℃contained only fine equiaxed crystals.HEA sintered at 1100℃featured only the FCC solid solution,while theε-phase precipitated at temperatures above 1150℃.At a sintering temperature of 1050℃,the alloy microstructure consisted of short rod-like dendrites and fine equiaxed crystals.This alloy achieved the highest yield strength of 1198.71 MPa owing to the effects of precipitation strengthening and grain boundary strengthening.Meanwhile,HEA sintered above 1050℃exhibited significantly improved corrosion resistance.Considering the microstructure,mechanical,and corrosion properties,1050℃was identified as the optimal sintering temperature for Co_(1.5)CrFeNi_(1.5)Ti_(0.6)HEA.展开更多
基金supported by the National Natural Science Foundation of China(52074313).
文摘The migration,accumulation,and high yield of hydrocarbons in tight sandstone reservoirs are closely tied to the natural fracture systems within the reservoirs.Large-scale fracture networks not only enhance reservoir seepage capacity but also influence effective productivity and subsequent fracturing reconstruction.Given the diverse mechanical behaviors,such as migration,penetration,or fracture arrest,traditional assumptions about fracture interaction criteria fail to address this complexity.To resolve these issues,a global cohesive element method is proposed to model random natural fractures.This approach verifies intersection models based on real-time stress conditions rather than pre-set criteria,enabling better characterization of interactions between hydraulic and natural fractures.Research has shown that the elastic modulus,horizontal stress difference,and fracturing fluid pumping rate significantly promote the expansion of hydraulic fractures.The use of low viscosity fracturing fluid can observe a decrease in the width of fractures near the wellbore,which may cause fractures to deflect when interacting with natural fractures.However,simulations under these conditions did not form a“complex network of fractures”.It is worth noting that when the local stress difference is zero,the result is close to the formation of this network.Excessive spacing will reduce the interaction between fractures,resulting in a decrease in the total length of fractures.By comprehensively analyzing these factors,an optimal combination can be identified,increasing the likelihood of achieving a“complex fracture network”.This paper thoroughly investigates hydraulic fracture propagation in naturally fractured reservoirs under various conditions,offering insights for developing efficient fracturing methods.
基金supported by National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum,Beijing(No.PRE/open-2307).
文摘The deep coal reservoir in Linxing-Shenfu block of Ordos Basin is an important part of China’s coalbed methane resources.In the process of reservoir reconstruction,the artificial fracture morphology of coal seam with gangue interaction is significantly different,which affects the efficient development of coalbed methane resources in this area.In this paper,the surface outcrop of Linxing-Shenfu block is selected,and three kinds of interaction modes between gangue and coal seam are set up,including single-component coal rock sample,coal rock sample with different thicknesses of gangue layer and coal rock sample with different numbers of gangue.Through true triaxial physical simulation and three-dimensional discrete element numerical simulation,the lawof artificial fracture initiation and propagation in multi-gangue interaction coal seam is analyzed in depth,and the hydraulic fracture initiation and propagation mode under different interaction modes of gangue layer in Linxing-Shenfu deep coal reservoir was clarified.The research shows that the initiation of artificial fractures in a single coal seam is affected by geologicalengineering factors.The maximum principal stress dominates the direction of fracture propagation,and the stress difference controls the fracture morphology.When the stress difference is 2 MPa,the fracture morphology is complex,which is easy to connect to the weak surface of coal and rock cleat,and the fracturemorphology of the stress difference is mainly a single main fracture.After the thickness of the gangue layer is increased from 2 to 5 cm,it is difficult for the artificial fracture to penetrate the layer vertically after the fracture initiation,and the effective transformation area of the reservoir is limited.The more the number of gangue layers,the greater the hydraulic energy consumption in the process of fracture propagation,and the more difficult the fracture propagation.
基金supported by the National Natural Science Foundation of China(Grant No.42171135)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Project No.2022098).
文摘The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.
基金Supported by the Specialized Research Project for LS17-2 Semi-submersible Production Platform(LSZX-2020-HN-05-0405).
文摘The taut mooring system using synthetic fiber ropes has overcome the shortcomings such as the large self-weight of the mooring lines and provides better mooring performance for the floating structures.The polyester rope has attracted much attention among numerous synthetic fiber rope materials due to its lightweight,low price,corrosion resistance,and high strength.Thus,the mooring characteristics of it are worth studying.Polyester mooring lines are flexible in deep water,when a marine structure is moored by them,the geometric nonlinearity such as large displacement,large stretch,and large bending deformation,and the material nonlinearity like viscoelastic of the polyester ropes become complex integrated problems to be studied.Considering the nonlinear phenomenon,the simulation and calculation of a polyester line were carried out by the absolute nodal coordinate formulation(ANCF)in this paper since the ANCF method has advantages in dealing with the significant deformation problems of the flexible structures.In addition,a chain mooring line was also simulated for comparison,and the results show that the polyester ropes reduce the self-weight of the mooring lines and provide sufficient mooring strength at the same time,and the nonlinear phenomenon of the polyester ropes is different from that of the chain mooring lines.
基金the financial support from the National Science and Technology Key Projects(2008ZX05056-002-03-04 and 2008ZX05030-005-07-03)
文摘With the rapid development of deepwater drilling operations,more and more complex technical challenges have to be faced due to the rigorous conditions encountered.One of these challenges is that the drilling fluid used must had good rheological properties at low temperatures and high ability to inhibit hydrate formation.Synthetic drilling fluid has been widely applied to deepwater drilling operations due to its high penetration rate,excellent rheological properties,good ability to prevent hydrate formation,and high biodegradability.A synthetic drilling fluid formulation was developed in our laboratory.The rheological properties of this drilling fluid at low temperatures （0-20 °C） were tested with a 6-speed viscometer and its ability to inhibit hydrate formation was evaluated at 20 MPa CH 4 gas and 0 °C by differential scanning calorimetry （DSC）.Several factors influencing the low temperature rheological properties of this synthetic drilling fluid were studied in this paper.These included the viscosity of the base fluid,the amount of CEMU and organic clay,and the water volume fraction.
文摘The paper overviews the research and application of silicate plugging agent, according to the different mechanisms and application forms, the plugging agent is divided into silicate gel, silicate precipitation, silicate/polymer, silicate/surfactant, silicate gel/foam and so on. This paper chiefly introduces the conception, mechanism and development tendency of the different systems mentioned above. The development tendency manifests as fully utilize personal properties and cooperate with other plugging agents or technologies, including the study of reaction mechanism, combination of plugging agent, grasping water flood timing, developing deep profile control and water shutoff technology, combining with other measures (chemicals huff and puff), in order to play the role of such blocking agents, further enhance oil recovery.
基金Project supported by the Science and Technology Project of CNOOC China Limited "Drilling and Completion Risk Evaluation and Countermeasure Study of Ultra High Temperature and High Pressure Development Wel1"(No.YXKY-ZX 09 2021).
文摘Offshore oil and gas production has become an important growth pole to ensure national energy security.However,China's offshore oil and gas production is lack of key core technologies and weak in tool and equipment foundation and can hardly support the optimized fast development of important fields.To solve these technological difficulties,China National Offshore Oil Corporation(CNOOC)insisted on independent technological innovation and overcame a series of key core technologies through theoretical research and key technology research and test during the 13th Five-Year Plan.And the following research results are obtained.First,several key technologies are broken through,including efficient drilling and completion in the middle and deep layers of the Bohai Sea,offshore large-scale heavy oil thermal recovery,deep-water oil and gas field development,and high temperature and high pressure well drilling and completion in the South China Sea,unconventional oil and gas stimulation,and offshore emergency rescue.Domestic first independently operated ultra deep water giant gas field,namely“Deepsea 1”is successfully put into production,so that the leap from 300 m to 1500 m of water depth and from exploration to development is realized.Second,key tools and equipment are developed,such as logging while drilling and rotary steering drilling system,deep-water drilling surface conductor,underwater emergency killing device,and underwater wellhead Christmas tree,which promote the high-quality development of China's offshore oil industry.Finally,some suggestions are proposed as follows.In the future,CNOOC shall strengthen independent technological innovation,quicken the pace to deepsea oil and gas,and continue to research key core technologies for oil and gas reserves and production increase(e.g.continuous localization of drilling and completion technologies,equipment and materials in complex fields),commingled gas production and test and green energy transformation(e.g.geothermal energy),so as to make greater contributions to ensure national energy security and build a maritime power.
基金funded by the project of the Major Scientific and Technological Projects of CNOOC in the 14th Five-Year Plan(No.KJGG2022-0701)the CNOOC Research Institute(No.2020PFS-03).
文摘To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures,this study considered the combined impact of geological-engineering factors on conductivity.Using reservoir production parameters and the discrete elementmethod,multispherical proppants were constructed.Additionally,a 3D fracture model,based on the specified conditions of the L block,employed coupled(Computational Fluid Dynamics)CFD-DEM(Discrete ElementMethod)for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures.Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport.Moreover,the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants,with a 27.7%decrease in the volume fraction of the fracture surface,subsequently affecting the placement concentration and damaging fracture conductivity.Compared to small-angle fractures,controlling artificial and natural fractures to expand at angles of 45°to 60°increases the effective support length by approximately 20.6%.During hydraulic fracturing of gas wells,ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures.
文摘1.Introduction As China’s first floating production platform in ultra-deepwater,the“Deep Sea No.1”energy station is a milestone in China’s deepwater resource utilization.The energy station is located in the LS17-2 gas field,150 km off the southeast coast of Hainan Island,China.It is a semi-submersible platform(Fig.1)with a displacement of 101 thousand tonnes and an operational draft of 35 to 40 m.The platform is permanently moored in 1422 m water by 16 chain-polyester-chain mooring lines in a 4×4 pattern,and six steel catenary risers(SCRs)are attached to the platform.It is the world’s first and only semi-submersible platform with the function of condensate storage,so it can be regarded as a floating production storage and offloading(FPSO)unit.With the ability to produce 3 billion m3 of natural gas each year(enough for over 10 million families),the Deep Sea No.1 energy station is a key step toward China’s energy independence.The LS17-2 gas field,where the Deep Sea No.1 energy station is located,was discovered in 2014.Plans for its development were made in 2015,followed by research and a preliminary design.Deep Sea No.1 went into operation on June 25,2021,and will operate onsite continuously without dry-docking for 30 years.
基金Supported by National Natural Science Foundation of China Enterprise Joint Fund Project(U24B200849)National Natural Science Foundation of China(91528303).
文摘Guided by the analysis of source-to-sink system,this study investigates the Paleogene Oligocene Lingshui Formation in the Qiongdongnan Basin by comparing the geological characterizes in land and sea areas and integrating outcrop,core,drilling,logging and 3D seismic data,to systematically analyze the characteristics of the source,transport pathway,and sink during the deposition of Lingshui Formation,and reveal the patterns,controlling factors and petroleum geologic significance of the source-to-sink systems.The results are obtained in five aspects.First,during the fault-depression transition,the Qiongdongnan Basin received sediments from the provenances presenting as segments in east-west and zones in north-south,primarily with the Indosinian granites in the Shenhu Uplift in the east and the Yanshanian granites in the west.Overall,the sources are young in the southern and northern parts and old in the interior of the basin.Second,three types of sediment transport pathways are identified:paleo-valleys,fault troughs and trough-valley transitional zones.Third,based on differences in sediment supply modes,the unique source-to-sink systems during the fault-depression transition in marine rift basins are categorized into three types:exogenous,endogenous and composite.Fourth,the characteristics of these source-to-sink systems are primarily controlled by provenance,paleogeomorphology,and sea-level changes.Provenance lithology and scale dictated the composition and volume of sedimentary deposits.Paleogeomorphology influenced erosion intensity in the provenance and the development of paleodrainage systems,thereby affecting the distribution and types of sedimentary systems.Additionally,sea-level changes decided the extent of the provenance,but also regulated the sediment distribution patterns through oceanic processes such as waves and tides.Fifth,the exogenous source-to-sink systems may form large-scale reservoir bodies,the endogenous systems develop secondary pores due to presence of soluble minerals,and the composite systems demonstrate reservoir properties varying from area to area.
基金supported by the State Key Laboratory of Offshore Oil and Gas Exploitation, Open Fund Project (No. CCL2023RCPS0162RQN)the primary funding, National Natural Science Foundation of China (No. ZX20230400)
文摘Saline aquifers are considered as highly favored reservoirs for CO_(2)sequestration due to their favorable properties.Understanding the impact of saline aquifer properties on the migration and distribution of CO_(2)plume is crucial.This study focuses on four key parameters-permeability,porosity,formation pressure,and temperature-to characterize the reservoir and analyse the petrophysical and elastic response of CO_(2).First,we performed reservoir simulations to simulate CO_(2)saturation,using multiple sets of these four parameters to examine their significance on CO_(2)saturation and the plume migration speed.Subsequently,the effect of these parameters on the elastic properties is tested using rock physics theory.We established a relationship of compressional wave velocity(V_(p))and quality factor(Q_(p))with the four key parameters,and conducted a sensitivity analysis to test their sensitivity to V_(p) and Q_(p).Finally,we utilized visco-acoustic wave equation simulated time-lapse seismic data based on the computed V_(p) and Q_(p) models,and analysed the impact of CO_(2) saturation changes on seismic data.As for the above nu-merical simulations and analysis,we conducted sensitivity analysis using both homogeneous and heterogeneous models.Consistent results are found between homogeneous and heterogeneous models.The permeability is the most sensitive parameter to the CO_(2)saturation,while porosity emerges as the primary factor affecting both Q_(p) and V_(p).Both Q_(p) and V_(p) increase with the porosity,which contradicts the observations in gas reservoirs.The seismic simulations highlight significant variations in the seismic response to different parameters.We provided analysis for these observations,which serves as a valuable reference for comprehensive CO_(2)integrity analysis,time-lapse monitoring,injection planning and site selection.
基金The research work was financially supported by the National Natural Science Foundation of China(Grant Nos.51979238 and 52301338)the Sichuan Science and Technology Program(Grant Nos.2023NSFSC1953 and 2023ZYD0140).
文摘Mitigating vortex-induced vibrations(VIV)in flexible risers represents a critical concern in offshore oil and gas production,considering its potential impact on operational safety and efficiency.The accurate prediction of displacement and position of VIV in flexible risers remains challenging under actual marine conditions.This study presents a data-driven model for riser displacement prediction that corresponds to field conditions.Experimental data analysis reveals that the XGBoost algorithm predicts the maximum displacement and position with superior accuracy compared with Support vector regression(SVR),considering both computational efficiency and precision.Platform displacement in the Y-direction demonstrates a significant positive correlation with both axial depth and maximum displacement magnitude.The fourth point displacement exhibits the highest contribution to model prediction outcomes,showing a positive influence on maximum displacement while negatively affecting the axial depth of maximum displacement.Platform displacement in the X-and Y-directions exhibits competitive effects on both the riser’s maximum displacement and its axial depth.Through the implementation of XGBoost algorithm and SHapley Additive exPlanation(SHAP)analysis,the model effectively estimates the riser’s maximum displacement and its precise location.This data-driven approach achieves predictions using minimal,readily available data points,enhancing its practical field applications and demonstrating clear relevance to academic and professional communities.
基金Supported by the National Natural Science Foundation of China(U24B2031)National Key Research and Development Project(2018YFA0702504)"14th Five-Year Plan"Science and Technology Project of CNOOC(KJGG2022-0201)。
文摘During drilling operations,the low resolution of seismic data often limits the accurate characterization of small-scale geological bodies near the borehole and ahead of the drill bit.This study investigates high-resolution seismic data processing technologies and methods tailored for drilling scenarios.The high-resolution processing of seismic data is divided into three stages:pre-drilling processing,post-drilling correction,and while-drilling updating.By integrating seismic data from different stages,spatial ranges,and frequencies,together with information from drilled wells and while-drilling data,and applying artificial intelligence modeling techniques,a progressive high-resolution processing technology of seismic data based on multi-source information fusion is developed,which performs simple and efficient seismic information updates during drilling.Case studies show that,with the gradual integration of multi-source information,the resolution and accuracy of seismic data are significantly improved,and thin-bed weak reflections are more clearly imaged.The updated seismic information while-drilling demonstrates high value in predicting geological bodies ahead of the drill bit.Validation using logging,mud logging,and drilling engineering data ensures the fidelity of the processing results of high-resolution seismic data.This provides clearer and more accurate stratigraphic information for drilling operations,enhancing both drilling safety and efficiency.
基金Supported by the National Natural Science Foundation of China (Grant Nos.52088102 and 51879287)National Key Research and Development Program of China (Grant No.2022YFB2602301)。
文摘Long-term responses of floating structures pose a great concern in their design phase. Existing approaches for addressing long-term extreme responses are extremely cumbersome for adoption. This work aims to develop an approach for the long-term extreme-response analysis of floating structures. A modified gradient-based retrieval algorithm in conjunction with the inverse first-order reliability method(IFORM) is proposed to enable the use of convolution models in long-term extreme analysis of structures with an analytical formula of response amplitude operator(RAO). The proposed algorithm ensures convergence stability and iteration accuracy and exhibits a higher computational efficiency than the traditional backtracking method. However, when the RAO of general offshore structures cannot be analytically expressed, the convolutional integration method fails to function properly. A numerical discretization approach is further proposed for offshore structures in the case when the analytical expression of the RAO is not feasible. Through iterative discretization of environmental contours(ECs) and RAOs, a detailed procedure is proposed to calculate the long-term response extremes of offshore structures. The validity and accuracy of the proposed approach are tested using a floating offshore wind turbine as a numerical example. The long-term extreme heave responses of various return periods are calculated via the IFORM in conjunction with a numerical discretization approach. The environmental data corresponding to N-year structural responses are located inside the ECs, which indicates that the selection of design points directly along the ECs yields conservative design results.
基金The National Natural Science Foundation of China under contract Nos U24B2016 and 42202157the National Basic Research Program of China under contract No. KJGG2022-0101+1 种基金the Key Laboratory of Tectonics and Petroleum Resources under contract No. TPR-2023-04CNOOC Technology Project under contract No. KJZH-2023-2105
文摘The deep layer has become an important replacement field for oil and gas exploration,but the formation mechanism of effective reservoirs is unknown,and the distribution of dessert reservoirs is difficult to predict,which seriously affects the discovery of deep resources.In this paper,the reservoir of the first and second members of the Shahejie Formation in the Caofeidian 6-4S area of the Bozhong Depression is taken as an example.Through the comprehensive means such as well-seismic calibration,denudation recovery,source-sink quantitative coupling,basin simulation,microscopic observation,X-ray diffraction,inclusion and thermodynamic analysis,the reservoir formation mechanism of dissolution pores and the favorable area distribution of thermodynamic prediction of dissolution reaction in the study area are carried out.The results show that the dissolution pores are the dominant type,accounting for more than 80%of the total pores.The dissolution reaction between soluble minerals such as feldspar accumulated in the near source and acidic fluids such as organic acids formed in the adjacent strata is the main mechanism for the development of dissolution pores.The organic matter in the adjacent strata is controlled by temperature and pressure during the burial evolution process to form organic acids,and migrates to the adjacent reservoirs for selective dissolution under the action of pressure and other driving forces.The characteristics of thermodynamic parameters(ΔG,which can determine whether feldspar is dissolved)and kinetic parameters(R,indicating the degree of feldspar dissolution)of feldspar dissolution reaction show that the thermodynamic parameters of feldspar dissolution are positively correlated with temperature,and the kinetic parameters are correlated with the concentration of organic acid discharge.The results of thermodynamic and kinetic parameters are coupled with provenance-sedimentary facies-diagenetic facies,and it is predicted that the plane area of TypeⅠfavorable area is 50 km^(2),and the plane area of TypeⅡfavorable area is 62.4 km2.This method provides theoretical reference and method guidance for the prediction of favorable reservoir distribution of deep clastic rocks,and has a good application prospect.
基金upported by the National Natural Science Foundation of China(42090021).
文摘Based on the survey of saline lacustrine shales in the Permian Lucaogou Formation and Fengcheng Formation in the Junggar Basin,it is found that the sweet intervals of these shale oil strata are enriched with lithium.In certain intervals,lithium contents reach up to 700μg/g,with produced water concentrations estimated to 517.2μg/g—an underexplored resource with considerable potential that has yet to receive adequate attention.The sedimentary environment,depositional process,and geochemical characteristics of these intervals were analyzed,indicating that lithium enrichment in saline lacustrine shale is controlled by multiple factors during deposition and diagenesis.The salinity of lake water during sedimentation plays a key role in lithium accumulation,with lithium primarily concentrated in carbonate-rich intervals,and diagenesis further affects its distribution.To assess the potential for lithium co-production in shale oil development,future research should be based on the enrichment mechanisms of lithium and hydrocarbons in lacustrine shales,predict the distribution patterns of oil and lithium-rich intervals,and evaluate the economic feasibility of an“oil-lithium integrated sweet spot”.Efficient lithium extraction and environmental protection technologies need to be explored to optimize resource development.Saline lacustrine shale oil development not only ensures stable oil and gas supplies but also,if lithium co-production is realized,could enhance China’s lithium security,contributing significantly to the country’s energy transformation.
基金paper is funded by the CNOOC Science and Technology Project(KJGG2022-0701)the National Natural Science Foundation of China(51904258,51874250).
文摘Thermal shock damage in deep shale hydraulic fracturing can impact fracture propagation behaviors,potentially leading to the formation of complex fractures and enhancing gas recovery.This study introduces a thermalhydraulic-mechnical(THM)coupled fracture propagation model relying on the phase field method to simulate thermal shock-induced fracturing in the deep shale considering dynamic temperature conditions.The validity of this model is confirmed through comparison of experimental and numerical results concerning the THM-coupled stress field and thermal cracking.Special attention is paid to the interaction of thermal shock-induced fractures in deep shale that contains weak planes.The results indicate that thermal shock-induced stress significantly amplifies the tensile stress range and deteriorates rock strength,resulting in a multi-point failure pattern within a fracture.The thermal shock damage degree is closely related to the fracture cooling efficiency,suggesting that considering downhole temperature conditions in THM-coupled fracture stress field calculations is advisable.Thermal shock can activate pre-existing natural fractures and enhance the penetration ability of hydraulic fractures,thereby leading to a fracture network.
基金the National Natural Science Foundation of China(Grant Nos.52371289 and 51979192).
文摘A three-dimensional numerical model of sand wave dynamics,incorporating the interaction of currents and waves at various angles,has been developed using the Regional Ocean Modeling System(ROMS).This model accounts for both bedload and suspended load sediment transport under combined waves and current conditions.The investigation examines the influence of several key parameters,including the rotation angle of sand waves relative to the main current,tidal current velocity amplitude,residual current,water depth,wave height,wave period,and wave direction,on sand wave evolution.The growth rate and migration rate of sand waves decrease as their rotation angle increases.For rotation angles smaller than 15°,sand wave evolution can be effectively simulated by a vertical 2D model with an error within 10%.The numerical results demonstrate that variations in tidal current velocity amplitude or residual current affect both vertical growth and horizontal migration of sand waves.As tidal current velocity amplitude and residual current increase,the growth rate initially rises to a maximum before decreasing.The migration rate shows a consistent increase with increasing tidal current amplitude and residual current.Under combined waves and current,both growth and migration rates decrease as water depth increases.With increasing wave height and period,the growth rate and migration rate initially rise to maximum values before declining,while showing a consistent increase with wave height and period.The change rate of sand waves reaches its maximum when wave propagation aligns parallel to tidal currents,and reaches its minimum when wave propagation is perpendicular to the currents.This phenomenon can be explained by the fluctuation of total bed shear stress relative to the angle of interaction between waves and current.
基金financially supported by the National Natural Science Foundation of China(General Program,Grant No.52374011)the Research and Innovation Fund for Graduate Students of Southwest Petroleum University(Grant No.2021CXYB04)the Sichuan Province Science and Technology Support Program(Grant No.2023NSFSC1980)。
文摘The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the transported substance may undergo phase transitions between solid,liquid,or gas states during dissociation and hydration processes.To effectively predict hydrate dissociation performance influenced by multi-field coupling processes,this study proposes a novel bond-based peridynamic coupled finite difference model that accounts for gas-liquid two-phase seepage behavior.The developed peridynamic(PD)model simulates hydrate dissociation reactions accompanied by gas-liquid seepage,mass transfer,and heat transfer phenomena.The formulation demonstrates strong agreement with established analytical solutions for one-dimensional problems and finite element transient solutions for two-dimensional problems in the literature,validating the accuracy and reliability of the newly constructed model.This research presents an innovative approach to simulate heat transport and multiphase flow phenomena associated with hydrate dissociation.
基金supported by Special Fund for the Development of 1500-Meter Subsea Christmas Trees and Control Systems.
文摘In order to develop a marine engineering material with excellent mechanical properties and corrosion resistance,a novel non-equiatomic Co_(1.5)CrFeNi_(1.5)Ti_(0.6)high-entropy alloy(HEA)was fabricated through mechanical alloying and spark plasma sintering.The results revealed that the sintering temperature significantly affected the microstructure and phase composition of the HEA owing to the diffusion rate,homogenization,and sluggish diffusion effect of metal atoms.At sintering temperatures below 1050℃,HEA mainly consisted of face-centered cubic(FCC),Ni_(3)Ti(ε),Ni_(2.67)Ti_(1.33)(R),and Fe-Cr(σ)phases.The microstructure of alloy comprised coarse dendritic crystals,whose content and size gradually decreased with increasing sintering temperature.However,the HEA sintered above 1100℃contained only fine equiaxed crystals.HEA sintered at 1100℃featured only the FCC solid solution,while theε-phase precipitated at temperatures above 1150℃.At a sintering temperature of 1050℃,the alloy microstructure consisted of short rod-like dendrites and fine equiaxed crystals.This alloy achieved the highest yield strength of 1198.71 MPa owing to the effects of precipitation strengthening and grain boundary strengthening.Meanwhile,HEA sintered above 1050℃exhibited significantly improved corrosion resistance.Considering the microstructure,mechanical,and corrosion properties,1050℃was identified as the optimal sintering temperature for Co_(1.5)CrFeNi_(1.5)Ti_(0.6)HEA.
