Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this s...Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.展开更多
In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in dif...In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in different intervals is unconnected)features of shale oil within the organic-rich shale in the Qingshankou Formation of the Gulong Sag.Our study shows that retained petroleum characteristics in the investigated succession are mainly influenced by three factors:organic richness,intraformational migration and segmented accumulation.Organic matter richness primarily controls the amount of retained petroleum,especially the‘live’component indicated by the S_(2)value rather than the total organic carbon(TOC)figure alone.The negative expulsion efficiencies determined by mass-balance calculations of hydrocarbons reveal that petroleum from adjacent organic-rich intervals migrates into the interval of about 2386-2408 m,which is characterized by high free hydrocarbon(S_(1)),OSI and saturated hydrocarbons content,along with a greater difference inδ^(13)C values between polar compounds(including resins and asphaltenes)and saturated hydrocarbons.The depth-dependent heterogeneity of carbon isotope ratios(δ^(13)C)of mud methane gas,δ^(13)C of extracts gross composition(SARA),δ^(13)C of kerogen and SARA content of extracts suggest that the studied succession can be subdivided into four intervals.The shale oil sealing enrichment character in each interval is further corroborated by the distinctδ^(13)C values of mud methane gas in different intervals.Due to the migration of petroleum into the 2386-2408 m interval,the S_(1),OSI and saturated hydrocarbons content of the interval show higher relative values.The maturity of organic matter in the 2471-2500 m interval is at the highest with the smaller size molecular components of the retained petroleum.Thus,favorable‘sweet spots’may be found in the 2386-2408 m interval and the 2471-2500 m interval,according to the experiment results in this study.展开更多
Assuming a reservoir with a typical salt-lake background in the Qaidam Basin as a testbed,in this study the var-iation law of the rock electrical parameters has been determined through water displacement experiments w...Assuming a reservoir with a typical salt-lake background in the Qaidam Basin as a testbed,in this study the var-iation law of the rock electrical parameters has been determined through water displacement experiments with different salinities.As made evident by the results,the saturation index increases with the degree of water injec-tion.When the salinity of the injected water is lower than 80000 ppm,the resistivity of the rock samplefirst decreases,then it remains almost constant in an intermediate stage,andfinally it grows,thereby giving rise to a‘U’profile behavior.As the salinity decreases,the water saturation corresponding to the inflection point of the resistivity becomes lower,thereby leading to a wider‘U’type range and a higher terminal resistivity.For dif-ferent samples,higher initial resistivity of the sample in the oil-bearing state,and higher resistivity after low-sali-nity water washing are obtained when a thicker lithology is considered.展开更多
CO_(2)huff and puff experiments of different injection parameters,production parameters and soaking time were carried out on large-scale cubic and long columnar outcrop samples to analyze dynamic characteristics and i...CO_(2)huff and puff experiments of different injection parameters,production parameters and soaking time were carried out on large-scale cubic and long columnar outcrop samples to analyze dynamic characteristics and influencing factors of CO_(2)huff and puff and the contribution of sweeping mode to recovery.The experimental results show that the development process of CO_(2)huff and puff can be divided into four stages,namely,CO_(2)backflow,production of gas with some oil,high-speed oil production,and oil production rate decline stages.The production of gas with some oil stage is dominated by free gas displacement,and the high-speed oil production stage is dominated by dissolved gas displacement.CO_(2)injection volume and development speed are the major factors affecting the oil recovery.The larger the injected CO_(2)volume and the lower the development speed,the higher the oil recovery will be.The reasonable CO_(2)injection volume and development speed should be worked out according to oilfield demand and economic evaluation.There is a reasonable soaking time in CO_(2)huff and puff.Longer soaking time than the optimum time makes little contribution to oil recovery.In field applications,the stability of bottom hole pressure is important to judge whether the soaking time is sufficient during the huff period.The oil recovery of CO_(2)huff and puff mainly comes from the contribution of flow sweep and diffusion sweep,and diffusion sweep contributes more to the oil recovery when the soaking time is sufficient.展开更多
The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative character...The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative characterization model, and geological application. It is found that the isotopic fractionation during the complete production of shale gas/coalbed methane shows a four-stage characteristic of “stable-lighter-heavier-lighter again”, which is related to the complex gas migration modes in the pores of shale/coal. The gas migration mechanisms in shale/coal include seepage, diffusion, and adsorption/desorption. Among them, seepage driven by pressure difference does not induce isotopic fractionation, while diffusion and adsorption/desorption lead to significant isotope fractionation. The existing characterization models of isotopic fractionation include diffusion fractionation model, diffusion-adsorption/desorption coupled model, and multi-scale and multi-mechanism coupled model. Results of model calculations show that the isotopic fractionation during natural gas migration is mainly controlled by pore structure, adsorption capacity, and initial/boundary conditions of the reservoir rock. So far, the isotope fractionation model has been successfully used to evaluate critical parameters, such as gas-in-place content and ratio of adsorbed/free gas in shale/coal etc. Furthermore, it has shown promising application potential in production status identification and decline trend prediction of gas well. Future research should focus on:(1) the co-evolution of carbon and hydrogen isotopes of different components during natural gas migration,(2) the characterization of isotopic fractionation during the whole process of gas generation-expulsion-migration-accumulation-dispersion, and(3) quantitative characterization of isotopic fractionation during natural gas migration in complex pore-fracture systems and its application.展开更多
The control effects of different occurrence faults on oil and gas accumulation and distribution in the outer slope area of oil and gas reservoirs were studied taking the south-central Wen’an slope of the Jizhong depr...The control effects of different occurrence faults on oil and gas accumulation and distribution in the outer slope area of oil and gas reservoirs were studied taking the south-central Wen’an slope of the Jizhong depression in the Bohai Bay Basin as an example.Based on 3D seismic data and the distribution of oil and water,the controlling differences between consequent fault and antithetic fault were analyzed and compared from the formation and evolution rule of faults and the formation mechanism of fault traps,including development positions of the consequent fault traps and antithetic fault traps,oil and gas distribution horizon adjusted by fault and formation period of fault traps.The differences between consequent faults and antithetic faults in controlling reservoirs have three main aspects:(1)Consequent fault traps and antithetic fault traps are in different positions,the consequent fault traps are at the segmented growing point in the hanging wall of"hard-linkage"faults,while the antithetic fault traps are developed in the position with the largest throw in the footwall because of tilting action;(2)The two kinds of faults result in different oil and gas distribution vertically,oil and gas adjusted by consequent faults is distributed in a single layer or multi-layers,while oil and gas adjusted by antithetic faults occur in single layers;(3)The two kinds of fault traps are formed in different periods,the consequent fault traps are formed at the time when the related faults enter the stage of"hard-linkage",while the antithetic fault traps are formed at the beginning of the fault active period.展开更多
1 Introduction△LgR technology was widely used in source rocks (TOC) well logging evaluation as well as the most reliable way in the industry. This technology applies electrical resistivity and interval transit time...1 Introduction△LgR technology was widely used in source rocks (TOC) well logging evaluation as well as the most reliable way in the industry. This technology applies electrical resistivity and interval transit time curve to cauculat TOC.According to the continuous TOC content calculated form logging curries, thickness of source rocks with different abundance levels can be distinguished, therefore,it also provides an effective methods for the study of hydrocarbon contribute of different organic abundance levels.展开更多
1 Introduction The coal, as a special reservoir, has a dual accumulating system of matrix pore and fracture. The pore is the main reservoir space of coalbed methane (CBM) in coal. Generally, pore structure is very c...1 Introduction The coal, as a special reservoir, has a dual accumulating system of matrix pore and fracture. The pore is the main reservoir space of coalbed methane (CBM) in coal. Generally, pore structure is very complicated and irregularly so that it is hard to be described in the traditional geometry. The fractal theory plays an important role in describing the porous media of the seepage system in recent years. The studies by Pfeifer, Katz and Kroch show the pore distribution in such reservoirs as coal, sandstone, shale and carbonatite is according with the fractal theory.展开更多
Aiming at the technology of hydraulic fracturing assisted oil displacement which combines hydraulic fracturing,seepage and oil displacement,an experimental system of energy storage and flowback in fracturing assisted ...Aiming at the technology of hydraulic fracturing assisted oil displacement which combines hydraulic fracturing,seepage and oil displacement,an experimental system of energy storage and flowback in fracturing assisted oil displacement process has been developed and used to simulate the mechanism of percolation,energy storage,oil displacement and flowback of chemical agents in the whole process.The research shows that in hydraulic fracturing assisted oil displacement,the chemical agent could be directly pushed to the deeper area of the low and medium permeability reservoirs,avoiding the viscosity loss and adhesion retention of chemical agents near the pay zone;in addition,this technology could effectively enlarge the swept volume,improve the oil displacement efficiency,replenish formation energy,gather and exploit the scattered residual oil.For the reservoir with higher permeability,this measure takes effect fast,so to lower cost,and the high pressure hydraulic fracturing assisted oil displacement could be adopted directly.For the reservoir with lower permeability which is difficult to absorb water,hydraulic fracturing assisted oil displacement with surfactant should be adopted to reduce flow resistance of the reservoir and improve the water absorption capacity and development effect of the reservoir.The degree of formation energy deficit was the main factor affecting the effective swept range of chemical agents.Moreover,the larger the formation energy deficit was,the further the seepage distance of chemical agents was,accordingly,the larger the effective swept volume was,and the greater the increase of oil recovery was.Formation energy enhancement was the most important contribution to enhanced oil recovery(EOR),which was the key to EOR by the technology of hydraulic fracturing assisted oil displacement.展开更多
Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney (BGS) basin system in Australia. The origin of dawsonite is emphatically contraste...Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney (BGS) basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ13C values ranging from -4.0×10-3 to 4.1×10-3 are remarkably consistent through the BGS basin system. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.3×10-3 to -4.6×10-3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatic activity. In Hailaer Basin, the Dawsonite δ13C values ranging from -4.64×10-3 to 2.12×10-3 are also consistent. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.82×10-3 to -5.11×10-3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source,lying along deep fracture within or adjacent to Yanshanian granite,it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatic process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.展开更多
1 Introduction The importance of reservoir has been widely recognized in the field of unconventional oil and gas r, esource(Zou Caineng et al., 2012). The pore structure is the core problem of coal reservoir. One si...1 Introduction The importance of reservoir has been widely recognized in the field of unconventional oil and gas r, esource(Zou Caineng et al., 2012). The pore structure is the core problem of coal reservoir. One side, the pore structure influenced the adsorption ability of the coal pore structure; The other hand, the pore structure determines the coalbed methane output mode(Zou Caineng et al., 2013). Hou QuanLin(2012) thinked that different deformation mechanisms, such as composition of the pore system and structure of coal are different, mainly in microstructure and pore structure and coal and chemical structure.展开更多
The Huhehu Sag is one of the most important oil and gas depressions in the Hailar Basin. However, the origin of Huhehu oil is still controversial. Previous studies on source rocks have mainly focused on the Nantun For...The Huhehu Sag is one of the most important oil and gas depressions in the Hailar Basin. However, the origin of Huhehu oil is still controversial. Previous studies on source rocks have mainly focused on the Nantun Formation(K1 n); a few studies have investigated the Damoguaihe Formation(K1 d). Based on the Rock–Eval pyrolysis parameters, 172 drill cutting samples from the Huhehu Sag were analyzed to evaluate their geochemical characteristics. Based on the Rock–Eval data, the mudstones from the first member of the Damoguaihe Formation(K1 d1) and the second member of the Nantun Formation(K1 n2) have moderate to high hydrocarbon generation potential, while mudstones from the first member of the Nantun Formation(K1 n1) have poor to good hydrocarbon generation potential.Additionally, both the K1 n1 and K1 n2 coal members have poor to fair hydrocarbon generation potential, but the K1 n2 coal member has a better generative potential. Fifteen Huhehu oils were collected for molecular geochemical analyses to classify the oils into genetic families and to identify the source rock for each oil using chemometric methods. The Huhehu oils were classified into three groups with different maturity levels using hierarchical cluster analysis and principal component analysis. Group A oils(high maturity) are characterized by relatively moderate ratios of Pr/Ph, Pr/n-C17, and Ph/n-C18, as well as an abundance of C29 steranes, mainly derived from the K1 n2 and K1 n1 mudstone members. In comparison, group B oils(moderate maturity) have relatively low Pr/Ph ratios,moderate Pr/n-C17 and Ph/n-C18 ratios, and low concentrations of C29 steranes. Group C oils(low maturity) show relatively high ratios of Pr/Ph, Pr/n-C17, and Ph/n-C18, as well as high concentrations of C29 steranes. Furthermore,group B oils derived from the K1 d1 mudstone member and group C oils derived from the K1 n2 coal member were also identified by principal component analysis score plots.Correlation studies suggest a major contribution from the K1 n mudstone Formation and the K1 d1 mudstone member to the oils of the Huhehu Sag. So, the Nantun Formation and relatively shallow strata of the Damoguaihe Formation(e.g., the K1 d1 member) represent important targets for future oil-reservoir exploration in the Huhehu Sag.展开更多
Objective The Hailar Basin is situated in the northwestern margin of the Jiamusi-Mongolia Block.It was a continent marginal basin to the south of the Mongolia-Okhotsk Ocean during the Jurassic and Cretaceous.The basem...Objective The Hailar Basin is situated in the northwestern margin of the Jiamusi-Mongolia Block.It was a continent marginal basin to the south of the Mongolia-Okhotsk Ocean during the Jurassic and Cretaceous.The basement of the basin is a late Paleozoic marine deposit.The filling of the basin is characterized by terrestrial volcanic rocks。展开更多
There is no clear consensus on the definition of tight oil in literature; however, more that tight reservoirs refer to and more researchers accept those with permeability less than 1.0 mD or 0.1 mD in the subsurface c...There is no clear consensus on the definition of tight oil in literature; however, more that tight reservoirs refer to and more researchers accept those with permeability less than 1.0 mD or 0.1 mD in the subsurface condition (Jia et al., 2012; Zhao et al., 2012; Zhao, 2012; Zou et al., 2014).展开更多
Knowing methane desorption characteristics is essential to define the contribution of adsorbed gas to gas well production.To evaluate the synthetic effect of a clay stabilizer solution on methane desorption kinetics a...Knowing methane desorption characteristics is essential to define the contribution of adsorbed gas to gas well production.To evaluate the synthetic effect of a clay stabilizer solution on methane desorption kinetics and isotherms pertaining to Longmaxi shale,an experimental setup was designed based on the volumetric method.The objective was to conduct experiments on methane adsorption and desorption kinetics and isotherms before and after clay stabilizer treatments.The experimental data were a good fit for both the intraparticle diffusion model and the Freundlich isotherm model.We analyzed the effect of the clay stabilizer on desorption kinetics and isotherms.Results show that clay stabilizer can obviously improve the diffusion rate constant and reduce the methane adsorption amount.Moreover,we analyzed the desorption efficiency before and after treatment as well as the adsorbed methane content.The results show that a higher desorption efficiency after treatment can be observed when the pressure is higher than 6.84 MPa.Meanwhile,the adsorbed methane content before and after treatment all increase when the pressure decreases,and clay stabilizer can obviously promote the adsorbed methane to free gas when the pressure is lower than 19 MPa.This can also be applied to the optimization formulation of slickwater and the design of gas well production.展开更多
Based on the three-dimensional seismic interpretation data,this paper analyzed the formation mechanism and the growth process of the oblique anticline AE of the M region of the eastern Niger Delta,as well as the evolu...Based on the three-dimensional seismic interpretation data,this paper analyzed the formation mechanism and the growth process of the oblique anticline AE of the M region of the eastern Niger Delta,as well as the evolution process of the associated fault systems.The study results show that the stratigraphic sedimentary period between reflector H4-H6 of the middle and late Miocene was the initial fold-thrust stage,the anticline AE was a half-graben controlled by oblique extensional faults derived from the oblique extensional transfer structure formed by local initial differential fold-thrusting.At the same time the tear faults developed as a result of the differential sliding.During the stratigraphic sedimentary period between reflector H1-H4 of the late Miocene to Pliocene,the large-scale folding and thrusting occurred,differential contractional deformation resulted in the pre-existing extensional half-graben became AE anticline by oblique tectonic inversion,then the anticline grew continually and the crest of the anticline migrated gradually.The newly formed fault systems consist of a small number of associated tear-normal faults caused by differential thrusting and gravity-driven domino normal faults predominantly induced by the slope inclination of the anticline limb.During the stratigraphic sedimentary period between reflector H0-H1 of the Pleistocene to Holocene,as the growth of the anticline ceased,the area entered post-fold thrusting stage.The formation and distribution of conjugated faults were controlled by the local gravity return collapse,local differential sliding and reactivation of pre-existing positive inversion faults jointly.The research results of genetic mechanism of the oblique inversion anticline and evolution of associated faults are helpful to reveal the key factors controlling the accumulation and distribution of oil and gas.展开更多
The research area is situated in the western part of Tarim basin,which includes Awati depression and Bachu uplifted block. It underwent three times processes of compression in a large scale and a near term extension s...The research area is situated in the western part of Tarim basin,which includes Awati depression and Bachu uplifted block. It underwent three times processes of compression in a large scale and a near term extension since Cambrian. The first compression occurred during Middle Cambrian to Devonian, which formed fault band folds in NW axial direction. They were "under-water uplift"and distributed all over the research area. The second compression occurred in Late Permian and formed fault band folds and a few fault propagation folds in NS axial direction. They are developed near Tumuxiuke fault belt and the northern research area. The western anticline is bigger than the eastern one in extent and size. The third compression occurred during Palaeogene to Quaternary and formed tumuxiuke fault belt and fault propagation folds in NW direction. They are distributed over the south part of the research area. Tumuxiuke fault belt is a big scale dextral reversed strike-slip fault belt; it transformed or destroyed the fold structure of the research area. A short-term extension occurred during Early Permian. Tarim Basin is in the rift forming stage of craton, and there exist widespread basic volcanic rocks, basic intrusive bodies and dikes.展开更多
The study aims to find out the formation period of fault traps near faults in petroliferous basins,based on an analysis of the formation period of fault lateral sealing and related influential factors.A method to calc...The study aims to find out the formation period of fault traps near faults in petroliferous basins,based on an analysis of the formation period of fault lateral sealing and related influential factors.A method to calculate the formation period of fault lateral sealing(i.e.the time when displacement pressure of fault rock is equal to that of reservoir rock in fault wall with hydrocarbon migration)is established by comparing the relationship between displacement pressure and time for fault rock and reservoir rock.This method is then applied to the study on reservoirs in the 1^(st),2^(nd),and 3^(rd) members of Dongying Formation(E_(3)d^(1),E_(3)d^(2) and E_(3)d^(3))in terms of formation period of lateral sealing of F3 fault crossing the three reservoirs in the No.5 structure of Nanpu Sag in Bohai Bay Basin.The results indicate that the formation period of the lateral sealing in the studied reservoirs can date from 7.1 Ma,7.4 Ma and 9.2 Ma respectively,all prior to the hydrocarbon accumulation period(about 2.58 Ma).Hence,it can be concluded that these reservoirs are favorable for the accumulation and preservation of hydrocarbons generated from the underlying source rock E_(3)s^(3),and the method proposed is feasible in calculating the formation period of fault lateral sealing.展开更多
基金financially supported by the National Natural Science Foundation of China(41972156)the Natural Science Foundation of Heilongjiang Province(TD 2021D001).
文摘Organic matter(OM)hosted pores are crucial for the storage and migration of petroleum in shale reservoirs.Thermal maturity and macerals type are important factors controlling the development of pores therein.In this study,six lacustrine shale samples with different thermal maturities from the first member of the Qingshankou Formation in the Songliao Basin,of which vitrinite reflectance(R_(o))ranging from 0.58% to 1.43%,were selected for a comparative analysis.Scanning electron microscopy(SEM)and reflected light microscopy were combined to investigate the development of organic pores in different macerals during thermal maturation.The results show that alginite and liptodetrinite are the dominant primary macerals,followed by bituminite.Only a few primary organic pores developed in the alginite at the lowest maturity(R_(o)=0.58%).As a result of petroleum generation,oil-prone macerals began to transform to initial-oil solid bitumen at the early oil window(R_(o)=0.73%)and shrinkage cracks were observed.Initial-oil solid bitumen cracked to oil,gas and post-oil bitumen by primary cracking(R_(o)=0.98%).Moreover,solid bitumen(SB)was found to be the dominant OM when R_(o)>0.98%,which indicates that SB is the product of oil-prone macerals transformation.Many secondary bubble pores were observed on SB,which formed by gas release,while devolatilization cracks developed on migrated SB.Additionally,at the late oil window(Ro?1.16%),migrated SB filled the interparticle pore spaces.With further increase in temperature,the liquid oil underwent secondary cracking into pyrobitumen and gas,and spongy pores developed on the pyrobitumen at higher levels of maturity(Ro=1.43%),which formed when pyrobitumen cracked into gas.Vitrinite and inertinite are stable without any visible pores over the range of maturities,verifying their low petroleum generation potential.In addition,it was concluded that clay minerals could have a catalytic effect on the petroleum generation,which may explain why organicclay mixtures had more abundant pores than single OM particles.However,after R_(o)>0.98%,authigenic minerals occupied the organic pore spaces on the organic-clay mixtures,resulting in fewer pores compared to those observed in samples at the early to peak oil window.
基金the support from the Scientific Research Project from RIPED(2021ycq01)the Scientific Research and Technological Development Project of CNPC(2021DJ0107)the Basic Research and Strategic Reserve Technology Research Project of CNPC(2020D-5008-01)。
文摘In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in different intervals is unconnected)features of shale oil within the organic-rich shale in the Qingshankou Formation of the Gulong Sag.Our study shows that retained petroleum characteristics in the investigated succession are mainly influenced by three factors:organic richness,intraformational migration and segmented accumulation.Organic matter richness primarily controls the amount of retained petroleum,especially the‘live’component indicated by the S_(2)value rather than the total organic carbon(TOC)figure alone.The negative expulsion efficiencies determined by mass-balance calculations of hydrocarbons reveal that petroleum from adjacent organic-rich intervals migrates into the interval of about 2386-2408 m,which is characterized by high free hydrocarbon(S_(1)),OSI and saturated hydrocarbons content,along with a greater difference inδ^(13)C values between polar compounds(including resins and asphaltenes)and saturated hydrocarbons.The depth-dependent heterogeneity of carbon isotope ratios(δ^(13)C)of mud methane gas,δ^(13)C of extracts gross composition(SARA),δ^(13)C of kerogen and SARA content of extracts suggest that the studied succession can be subdivided into four intervals.The shale oil sealing enrichment character in each interval is further corroborated by the distinctδ^(13)C values of mud methane gas in different intervals.Due to the migration of petroleum into the 2386-2408 m interval,the S_(1),OSI and saturated hydrocarbons content of the interval show higher relative values.The maturity of organic matter in the 2471-2500 m interval is at the highest with the smaller size molecular components of the retained petroleum.Thus,favorable‘sweet spots’may be found in the 2386-2408 m interval and the 2471-2500 m interval,according to the experiment results in this study.
基金The authors would like to acknowledge the financial support from the Jiangsu Key Laboratory of Oil-Gas Storage and Transportation Technology(Grant No.CDYQCY202201)funded by the Key Laboratory of Shallow Geothermal Energy,Ministry of Natural Resources of the People’s Republic of China.The authors thank the anonymous reviewers for their constructive and valuable opinions gratefully.
文摘Assuming a reservoir with a typical salt-lake background in the Qaidam Basin as a testbed,in this study the var-iation law of the rock electrical parameters has been determined through water displacement experiments with different salinities.As made evident by the results,the saturation index increases with the degree of water injec-tion.When the salinity of the injected water is lower than 80000 ppm,the resistivity of the rock samplefirst decreases,then it remains almost constant in an intermediate stage,andfinally it grows,thereby giving rise to a‘U’profile behavior.As the salinity decreases,the water saturation corresponding to the inflection point of the resistivity becomes lower,thereby leading to a wider‘U’type range and a higher terminal resistivity.For dif-ferent samples,higher initial resistivity of the sample in the oil-bearing state,and higher resistivity after low-sali-nity water washing are obtained when a thicker lithology is considered.
文摘CO_(2)huff and puff experiments of different injection parameters,production parameters and soaking time were carried out on large-scale cubic and long columnar outcrop samples to analyze dynamic characteristics and influencing factors of CO_(2)huff and puff and the contribution of sweeping mode to recovery.The experimental results show that the development process of CO_(2)huff and puff can be divided into four stages,namely,CO_(2)backflow,production of gas with some oil,high-speed oil production,and oil production rate decline stages.The production of gas with some oil stage is dominated by free gas displacement,and the high-speed oil production stage is dominated by dissolved gas displacement.CO_(2)injection volume and development speed are the major factors affecting the oil recovery.The larger the injected CO_(2)volume and the lower the development speed,the higher the oil recovery will be.The reasonable CO_(2)injection volume and development speed should be worked out according to oilfield demand and economic evaluation.There is a reasonable soaking time in CO_(2)huff and puff.Longer soaking time than the optimum time makes little contribution to oil recovery.In field applications,the stability of bottom hole pressure is important to judge whether the soaking time is sufficient during the huff period.The oil recovery of CO_(2)huff and puff mainly comes from the contribution of flow sweep and diffusion sweep,and diffusion sweep contributes more to the oil recovery when the soaking time is sufficient.
基金National Postdoctoral Innovative Talent Support Program(BX20220062)National Natural Science Foundation of China(41672130 and 41972123)SINOPEC Corp.(P17027-3)。
文摘The research progress of isotopic fractionation in the process of shale gas/coalbed methane migration has been reviewed from three aspects: characteristics and influencing factors, mechanism and quantitative characterization model, and geological application. It is found that the isotopic fractionation during the complete production of shale gas/coalbed methane shows a four-stage characteristic of “stable-lighter-heavier-lighter again”, which is related to the complex gas migration modes in the pores of shale/coal. The gas migration mechanisms in shale/coal include seepage, diffusion, and adsorption/desorption. Among them, seepage driven by pressure difference does not induce isotopic fractionation, while diffusion and adsorption/desorption lead to significant isotope fractionation. The existing characterization models of isotopic fractionation include diffusion fractionation model, diffusion-adsorption/desorption coupled model, and multi-scale and multi-mechanism coupled model. Results of model calculations show that the isotopic fractionation during natural gas migration is mainly controlled by pore structure, adsorption capacity, and initial/boundary conditions of the reservoir rock. So far, the isotope fractionation model has been successfully used to evaluate critical parameters, such as gas-in-place content and ratio of adsorbed/free gas in shale/coal etc. Furthermore, it has shown promising application potential in production status identification and decline trend prediction of gas well. Future research should focus on:(1) the co-evolution of carbon and hydrogen isotopes of different components during natural gas migration,(2) the characterization of isotopic fractionation during the whole process of gas generation-expulsion-migration-accumulation-dispersion, and(3) quantitative characterization of isotopic fractionation during natural gas migration in complex pore-fracture systems and its application.
基金Supported by the National Natural Science Foundation of China(41602129,41602164)China National Science and Technology Major Project(2016ZX05007003,2016ZX05006-005)
文摘The control effects of different occurrence faults on oil and gas accumulation and distribution in the outer slope area of oil and gas reservoirs were studied taking the south-central Wen’an slope of the Jizhong depression in the Bohai Bay Basin as an example.Based on 3D seismic data and the distribution of oil and water,the controlling differences between consequent fault and antithetic fault were analyzed and compared from the formation and evolution rule of faults and the formation mechanism of fault traps,including development positions of the consequent fault traps and antithetic fault traps,oil and gas distribution horizon adjusted by fault and formation period of fault traps.The differences between consequent faults and antithetic faults in controlling reservoirs have three main aspects:(1)Consequent fault traps and antithetic fault traps are in different positions,the consequent fault traps are at the segmented growing point in the hanging wall of"hard-linkage"faults,while the antithetic fault traps are developed in the position with the largest throw in the footwall because of tilting action;(2)The two kinds of faults result in different oil and gas distribution vertically,oil and gas adjusted by consequent faults is distributed in a single layer or multi-layers,while oil and gas adjusted by antithetic faults occur in single layers;(3)The two kinds of fault traps are formed in different periods,the consequent fault traps are formed at the time when the related faults enter the stage of"hard-linkage",while the antithetic fault traps are formed at the beginning of the fault active period.
文摘1 Introduction△LgR technology was widely used in source rocks (TOC) well logging evaluation as well as the most reliable way in the industry. This technology applies electrical resistivity and interval transit time curve to cauculat TOC.According to the continuous TOC content calculated form logging curries, thickness of source rocks with different abundance levels can be distinguished, therefore,it also provides an effective methods for the study of hydrocarbon contribute of different organic abundance levels.
文摘1 Introduction The coal, as a special reservoir, has a dual accumulating system of matrix pore and fracture. The pore is the main reservoir space of coalbed methane (CBM) in coal. Generally, pore structure is very complicated and irregularly so that it is hard to be described in the traditional geometry. The fractal theory plays an important role in describing the porous media of the seepage system in recent years. The studies by Pfeifer, Katz and Kroch show the pore distribution in such reservoirs as coal, sandstone, shale and carbonatite is according with the fractal theory.
基金Supported by the National Natural Science Foundation of China(52074087,51804076)Postdoctoral Natural Science Foundation of China(2021M690528).
文摘Aiming at the technology of hydraulic fracturing assisted oil displacement which combines hydraulic fracturing,seepage and oil displacement,an experimental system of energy storage and flowback in fracturing assisted oil displacement process has been developed and used to simulate the mechanism of percolation,energy storage,oil displacement and flowback of chemical agents in the whole process.The research shows that in hydraulic fracturing assisted oil displacement,the chemical agent could be directly pushed to the deeper area of the low and medium permeability reservoirs,avoiding the viscosity loss and adhesion retention of chemical agents near the pay zone;in addition,this technology could effectively enlarge the swept volume,improve the oil displacement efficiency,replenish formation energy,gather and exploit the scattered residual oil.For the reservoir with higher permeability,this measure takes effect fast,so to lower cost,and the high pressure hydraulic fracturing assisted oil displacement could be adopted directly.For the reservoir with lower permeability which is difficult to absorb water,hydraulic fracturing assisted oil displacement with surfactant should be adopted to reduce flow resistance of the reservoir and improve the water absorption capacity and development effect of the reservoir.The degree of formation energy deficit was the main factor affecting the effective swept range of chemical agents.Moreover,the larger the formation energy deficit was,the further the seepage distance of chemical agents was,accordingly,the larger the effective swept volume was,and the greater the increase of oil recovery was.Formation energy enhancement was the most important contribution to enhanced oil recovery(EOR),which was the key to EOR by the technology of hydraulic fracturing assisted oil displacement.
文摘Dawsonite, NaAlCO3(OH)2, is widespread as a cement, replacement and cavity filling in Hailaer Basin in China and Bowen-Gunnedah-Sydney (BGS) basin system in Australia. The origin of dawsonite is emphatically contrasted and analyzed through stable isotopic composition. Dawsonite δ13C values ranging from -4.0×10-3 to 4.1×10-3 are remarkably consistent through the BGS basin system. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.3×10-3 to -4.6×10-3. These values indicate carbon of dawsonite came from inorganic CO2 gas accompanied by magmatic activity. In Hailaer Basin, the Dawsonite δ13C values ranging from -4.64×10-3 to 2.12×10-3 are also consistent. The calculated δ13C values of CO2 gas in isotopic equilibrium with dawsonite range from -11.82×10-3 to -5.11×10-3. According to the coincidence of dawsonite-bearing well and CO2 gas well with mantle source,lying along deep fracture within or adjacent to Yanshanian granite,it is concluded that CO2 gas forming dawsonite is derived from mantle related to magmatic process during the Yanshanian. A little biologic origin carbon owing to petroleum charging intervened when dawsonite formed.
文摘1 Introduction The importance of reservoir has been widely recognized in the field of unconventional oil and gas r, esource(Zou Caineng et al., 2012). The pore structure is the core problem of coal reservoir. One side, the pore structure influenced the adsorption ability of the coal pore structure; The other hand, the pore structure determines the coalbed methane output mode(Zou Caineng et al., 2013). Hou QuanLin(2012) thinked that different deformation mechanisms, such as composition of the pore system and structure of coal are different, mainly in microstructure and pore structure and coal and chemical structure.
基金funded by the Natural Science Funding Council of China (Grant Nos. 41273059)GIGCAS 135 project (Grant No. Y234021001)Earmarked Fund of the State Key Laboratory of Organic Geochemistry (Grant No. sklog2016A01)
文摘The Huhehu Sag is one of the most important oil and gas depressions in the Hailar Basin. However, the origin of Huhehu oil is still controversial. Previous studies on source rocks have mainly focused on the Nantun Formation(K1 n); a few studies have investigated the Damoguaihe Formation(K1 d). Based on the Rock–Eval pyrolysis parameters, 172 drill cutting samples from the Huhehu Sag were analyzed to evaluate their geochemical characteristics. Based on the Rock–Eval data, the mudstones from the first member of the Damoguaihe Formation(K1 d1) and the second member of the Nantun Formation(K1 n2) have moderate to high hydrocarbon generation potential, while mudstones from the first member of the Nantun Formation(K1 n1) have poor to good hydrocarbon generation potential.Additionally, both the K1 n1 and K1 n2 coal members have poor to fair hydrocarbon generation potential, but the K1 n2 coal member has a better generative potential. Fifteen Huhehu oils were collected for molecular geochemical analyses to classify the oils into genetic families and to identify the source rock for each oil using chemometric methods. The Huhehu oils were classified into three groups with different maturity levels using hierarchical cluster analysis and principal component analysis. Group A oils(high maturity) are characterized by relatively moderate ratios of Pr/Ph, Pr/n-C17, and Ph/n-C18, as well as an abundance of C29 steranes, mainly derived from the K1 n2 and K1 n1 mudstone members. In comparison, group B oils(moderate maturity) have relatively low Pr/Ph ratios,moderate Pr/n-C17 and Ph/n-C18 ratios, and low concentrations of C29 steranes. Group C oils(low maturity) show relatively high ratios of Pr/Ph, Pr/n-C17, and Ph/n-C18, as well as high concentrations of C29 steranes. Furthermore,group B oils derived from the K1 d1 mudstone member and group C oils derived from the K1 n2 coal member were also identified by principal component analysis score plots.Correlation studies suggest a major contribution from the K1 n mudstone Formation and the K1 d1 mudstone member to the oils of the Huhehu Sag. So, the Nantun Formation and relatively shallow strata of the Damoguaihe Formation(e.g., the K1 d1 member) represent important targets for future oil-reservoir exploration in the Huhehu Sag.
基金supported by the National Natural Science Foundation of China(grant Nos.31670215,31270277)。
文摘Objective The Hailar Basin is situated in the northwestern margin of the Jiamusi-Mongolia Block.It was a continent marginal basin to the south of the Mongolia-Okhotsk Ocean during the Jurassic and Cretaceous.The basement of the basin is a late Paleozoic marine deposit.The filling of the basin is characterized by terrestrial volcanic rocks。
文摘There is no clear consensus on the definition of tight oil in literature; however, more that tight reservoirs refer to and more researchers accept those with permeability less than 1.0 mD or 0.1 mD in the subsurface condition (Jia et al., 2012; Zhao et al., 2012; Zhao, 2012; Zou et al., 2014).
基金supported by the China Scholarship Council(No.201908505143)the Chongqing Research Program of Basic Research and Frontier Technology(No.cstc2017jcyj AX0290/No.cstc2018jcyj AX0563)。
文摘Knowing methane desorption characteristics is essential to define the contribution of adsorbed gas to gas well production.To evaluate the synthetic effect of a clay stabilizer solution on methane desorption kinetics and isotherms pertaining to Longmaxi shale,an experimental setup was designed based on the volumetric method.The objective was to conduct experiments on methane adsorption and desorption kinetics and isotherms before and after clay stabilizer treatments.The experimental data were a good fit for both the intraparticle diffusion model and the Freundlich isotherm model.We analyzed the effect of the clay stabilizer on desorption kinetics and isotherms.Results show that clay stabilizer can obviously improve the diffusion rate constant and reduce the methane adsorption amount.Moreover,we analyzed the desorption efficiency before and after treatment as well as the adsorbed methane content.The results show that a higher desorption efficiency after treatment can be observed when the pressure is higher than 6.84 MPa.Meanwhile,the adsorbed methane content before and after treatment all increase when the pressure decreases,and clay stabilizer can obviously promote the adsorbed methane to free gas when the pressure is lower than 19 MPa.This can also be applied to the optimization formulation of slickwater and the design of gas well production.
基金Supported by the National Natural Science Foundation of China(41572127,U1562214)China National Science and Technology Major Project(2016ZX05006-005,2016ZX05054-009)
文摘Based on the three-dimensional seismic interpretation data,this paper analyzed the formation mechanism and the growth process of the oblique anticline AE of the M region of the eastern Niger Delta,as well as the evolution process of the associated fault systems.The study results show that the stratigraphic sedimentary period between reflector H4-H6 of the middle and late Miocene was the initial fold-thrust stage,the anticline AE was a half-graben controlled by oblique extensional faults derived from the oblique extensional transfer structure formed by local initial differential fold-thrusting.At the same time the tear faults developed as a result of the differential sliding.During the stratigraphic sedimentary period between reflector H1-H4 of the late Miocene to Pliocene,the large-scale folding and thrusting occurred,differential contractional deformation resulted in the pre-existing extensional half-graben became AE anticline by oblique tectonic inversion,then the anticline grew continually and the crest of the anticline migrated gradually.The newly formed fault systems consist of a small number of associated tear-normal faults caused by differential thrusting and gravity-driven domino normal faults predominantly induced by the slope inclination of the anticline limb.During the stratigraphic sedimentary period between reflector H0-H1 of the Pleistocene to Holocene,as the growth of the anticline ceased,the area entered post-fold thrusting stage.The formation and distribution of conjugated faults were controlled by the local gravity return collapse,local differential sliding and reactivation of pre-existing positive inversion faults jointly.The research results of genetic mechanism of the oblique inversion anticline and evolution of associated faults are helpful to reveal the key factors controlling the accumulation and distribution of oil and gas.
文摘The research area is situated in the western part of Tarim basin,which includes Awati depression and Bachu uplifted block. It underwent three times processes of compression in a large scale and a near term extension since Cambrian. The first compression occurred during Middle Cambrian to Devonian, which formed fault band folds in NW axial direction. They were "under-water uplift"and distributed all over the research area. The second compression occurred in Late Permian and formed fault band folds and a few fault propagation folds in NS axial direction. They are developed near Tumuxiuke fault belt and the northern research area. The western anticline is bigger than the eastern one in extent and size. The third compression occurred during Palaeogene to Quaternary and formed tumuxiuke fault belt and fault propagation folds in NW direction. They are distributed over the south part of the research area. Tumuxiuke fault belt is a big scale dextral reversed strike-slip fault belt; it transformed or destroyed the fold structure of the research area. A short-term extension occurred during Early Permian. Tarim Basin is in the rift forming stage of craton, and there exist widespread basic volcanic rocks, basic intrusive bodies and dikes.
文摘The study aims to find out the formation period of fault traps near faults in petroliferous basins,based on an analysis of the formation period of fault lateral sealing and related influential factors.A method to calculate the formation period of fault lateral sealing(i.e.the time when displacement pressure of fault rock is equal to that of reservoir rock in fault wall with hydrocarbon migration)is established by comparing the relationship between displacement pressure and time for fault rock and reservoir rock.This method is then applied to the study on reservoirs in the 1^(st),2^(nd),and 3^(rd) members of Dongying Formation(E_(3)d^(1),E_(3)d^(2) and E_(3)d^(3))in terms of formation period of lateral sealing of F3 fault crossing the three reservoirs in the No.5 structure of Nanpu Sag in Bohai Bay Basin.The results indicate that the formation period of the lateral sealing in the studied reservoirs can date from 7.1 Ma,7.4 Ma and 9.2 Ma respectively,all prior to the hydrocarbon accumulation period(about 2.58 Ma).Hence,it can be concluded that these reservoirs are favorable for the accumulation and preservation of hydrocarbons generated from the underlying source rock E_(3)s^(3),and the method proposed is feasible in calculating the formation period of fault lateral sealing.