The numerical simulation of polymer flooding is a complex task as this process involves complex physical and chemical reactions,and multiple sets of characteristic parameters are required to properly set the simulatio...The numerical simulation of polymer flooding is a complex task as this process involves complex physical and chemical reactions,and multiple sets of characteristic parameters are required to properly set the simulation.At present,such characteristic parameters are mainly obtained by empirical methods,which typically result in relatively large errors.By analyzing experimentally polymer adsorption,permeability decline,inaccessible pore volume,viscosity-concentration relationship,and rheology,in this study,a conversion equation is provided to convert the experimental data into the parameters needed for the numerical simulation.Some examples are provided to demonstrate the reliability of the proposed approach.展开更多
Shales in the Carboniferous–Permian Fengcheng(FC) and Lucaogou(LCG) formations in Junggar Basin are important organic rich rocks containing significant oil resources.To evaluate the difference in sedimentary environm...Shales in the Carboniferous–Permian Fengcheng(FC) and Lucaogou(LCG) formations in Junggar Basin are important organic rich rocks containing significant oil resources.To evaluate the difference in sedimentary environment conditions and hydrocarbon-generating potential between the FC and LCG formations.Total organic carbon(TOC),Rock-Eval pyrolysis,solvent extraction,column fractionation,stable carbon isotope,gas chromatography-mass spectrometry(GC-MS) of saturated hydrocarbons and organic petrology from the source rocks of FC and LCG formations.were analyzed.The biomarker composition indicates that during the deposition of FC,LCG-1 to LCG-2,the sedimentary environment for the source rock formations changed with gradual decrease of salinity,from anoxic to dyoxic/suboxic in redox conditions,and from strong stratification to weakened stratification of water.The FC Formation source rock,with main telalginite(planktonic green algae),archaebacteria and minor terrestrial organic matter,deposited in the environment characterized by high salinity and strongly reducing condition.Its TOC content is relatively low with a high original hydrocarbongenerating potential of unit organic material.The LCG Formation source rock deposited in the environment with low salinity and large variations,the organic matter is mainly sourced from telalginite(planktonic green algae),lamalginite,bacteria and higher plants,resulting in strong heterogeneity of the source rock.The abundance of TOC is high,but the original hydrocarbon generation potential of unit organic matter is lower than that of FC Formation.The results provide a geochemical basis for further study of saline-brackish water sedimentary environment shales in the Junggar Basin.展开更多
The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Fo...The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Formation in Jimusaer Sag,57 core samples from two boreholes were analyzed herein by performing total organic carbon(TOC)analysis,RockeEval pyrolysis,and gas chromatographicemass spectrometry experiments on saturated hydrocarbons.The kinetics of oil generation were studied using two samples comprising typical maceral components.The results showed that the hydrocarbons produced by telalginite are relatively rich in pristane(Pr),phytane(Ph),b-carotane,high-carbon normal alkanes,and C29 regular steranes.Hydrocarbons produced by lamalginite contain a significantly higher content of C20 tricyclic terpanes(TT),C21TT,C24 tetracyclic terpanes(TeT),C29 norhopane,and C28 regular sterane.Based on the pyrolysis and biomarker compound parameters,telalginite has a higher conversion rate for hydrocarbons than lamalginite in the low-mature to mature stage,which is consistent with their kinetic analysis.Lamalginite source rock displays a much narrower distribution of activation energies than telalginite source rocks.Such narrower activation energy distribution effectively narrows the main stage of hydrocarbon generation.In addition,the activation energy distribution of lamalginite concentrated in the high-value interval,indicating the characteristics of the relatively lagging hydrocarbon generation of lamalginite.展开更多
Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation n...Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation near wellbores is of great significance to understanding the water production mechanisms of gas wells.In this paper,a set of physical simulation experiment procedures of identifying the change of water saturation near wellbores was designed according to the principle of radial well seepage of gas wells,and the production performance after vertical well fracturing in gas reservoirs was simulated by connecting tight cores with a diameter of 10.5 cm,3.8 cm and 2.5 cm in series in a descending order of distance.According to the depressurizing production mode of gas wells,tubes with small diameters of 20,30,40 and 50 mm were used to simulate gas well tubing to control the gas production rate.And the change of water saturation near wellbore in the process of depletion production and its influencing factors were investigated.Finally,combined with actual data of production wells,the water saturation and water production of gas wells near wellbores and in different zones were calculated at the above four different small diameters of tubes and the changes thereof were also analyzed.The following results were obtained.First,each gas production rate corresponds to a critical water saturation.When the initial water saturation is lower than the critical value,the formation water flowing near the wellbore and in the middle zone can be carried out along with the production of gas and no liquid loading is formed.Second,when the initial water saturation is higher than the critical value,a large amount of formation water migrating from the far-wellbore zones accumulates near the wellbore,and thus liquid loading occurs at the bottom hole.Third,when the initial water saturation is equal to the critical value,the higher the gas production rate is,the more easily liquid loading tends to form near the wellbore.Fourth,for the same water saturation,water production increases and recovery factor decreases with the increase of gas production rate.In conclusion,the cumulative water production chart of a gas well generated by the physical simulation experiment method proposed in this paper agrees well with the water production behavior of the corresponding gas well.The research results are conducive to the effective prediction of gas well water production and can be used as guidance for the reasonable gas well water control.展开更多
Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie ...Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie Formation(Es3)on the gentle southern slope of the Gubei Sag,Bohai Bay Basin and draw some conclusions that,for complex sand bodies,with the increase in water level the distributary channels bifurcate frequently,from a simple branching shape to a network shape along with the increase in the development of crevasse splays,mouth bars and sheet sands.For single sand bodies,with an increase in water level in the slope zone of the lake basin close to the source area,the superimposition style transitioned from vertical cutting-stacking and lateral isolation to vertical stitching,isolation and lateral stitching.However,in the central zone of the lake basin far from the source area,the superimposition style transitioned from vertical stitching and lateral stitching to vertical isolation and lateral isolation.When water level stays stable,the greater the distance from the source area the greater the disaggregation ratio of a single sand body.At the same distance from the source area,higher water level tends to result in greater disaggregation ratio of a single sand body.展开更多
The condensate blockage causes a substantial decrease in well productivity for gas condensate reservoirs.Based on the previous studies,a novel experimental method was designed to evaluate condensate blockage and the m...The condensate blockage causes a substantial decrease in well productivity for gas condensate reservoirs.Based on the previous studies,a novel experimental method was designed to evaluate condensate blockage and the mitigating effect of gas injection.The method considers the stacking effect in the near wellbore region and the gas flow in the far wellbore region.There is an intermediate vessel containing condensate gas at the entrance of core holder in the experimental apparatus.In the process of pressure depletion experiment in a long core model,the vessel is connected to the core and the pressure of the vessel remains above the dew point pressure.The seriousness of condensate blockage is investigated by this research.When pressure drops to maximum retrograde condensation pressure,the gas permeability decreases by 80%compared with the initial gas permeability.Contrastive experiments were conducted to study the removal effect of different injection fluids and different injection volumes.The results show that CO2 injection is more effective than methanol in mitigating condensate blockage and the optimal CO2 injection volume is around 0.15 HCPV。展开更多
基金supported by Hubei Provincial Natural Science Foundation of China(Grant No.2020CFB377)the National Natural Science Foundation of China(Grant No.52104020).
文摘The numerical simulation of polymer flooding is a complex task as this process involves complex physical and chemical reactions,and multiple sets of characteristic parameters are required to properly set the simulation.At present,such characteristic parameters are mainly obtained by empirical methods,which typically result in relatively large errors.By analyzing experimentally polymer adsorption,permeability decline,inaccessible pore volume,viscosity-concentration relationship,and rheology,in this study,a conversion equation is provided to convert the experimental data into the parameters needed for the numerical simulation.Some examples are provided to demonstrate the reliability of the proposed approach.
文摘Shales in the Carboniferous–Permian Fengcheng(FC) and Lucaogou(LCG) formations in Junggar Basin are important organic rich rocks containing significant oil resources.To evaluate the difference in sedimentary environment conditions and hydrocarbon-generating potential between the FC and LCG formations.Total organic carbon(TOC),Rock-Eval pyrolysis,solvent extraction,column fractionation,stable carbon isotope,gas chromatography-mass spectrometry(GC-MS) of saturated hydrocarbons and organic petrology from the source rocks of FC and LCG formations.were analyzed.The biomarker composition indicates that during the deposition of FC,LCG-1 to LCG-2,the sedimentary environment for the source rock formations changed with gradual decrease of salinity,from anoxic to dyoxic/suboxic in redox conditions,and from strong stratification to weakened stratification of water.The FC Formation source rock,with main telalginite(planktonic green algae),archaebacteria and minor terrestrial organic matter,deposited in the environment characterized by high salinity and strongly reducing condition.Its TOC content is relatively low with a high original hydrocarbongenerating potential of unit organic material.The LCG Formation source rock deposited in the environment with low salinity and large variations,the organic matter is mainly sourced from telalginite(planktonic green algae),lamalginite,bacteria and higher plants,resulting in strong heterogeneity of the source rock.The abundance of TOC is high,but the original hydrocarbon generation potential of unit organic matter is lower than that of FC Formation.The results provide a geochemical basis for further study of saline-brackish water sedimentary environment shales in the Junggar Basin.
文摘The Middle Permian Lucaogou Formation in Northwestern China mainly contains typical saline lacustrine oil shale.To study the differences in geochemistry and hydrocarbon generation of source-rock samples in Lucaogou Formation in Jimusaer Sag,57 core samples from two boreholes were analyzed herein by performing total organic carbon(TOC)analysis,RockeEval pyrolysis,and gas chromatographicemass spectrometry experiments on saturated hydrocarbons.The kinetics of oil generation were studied using two samples comprising typical maceral components.The results showed that the hydrocarbons produced by telalginite are relatively rich in pristane(Pr),phytane(Ph),b-carotane,high-carbon normal alkanes,and C29 regular steranes.Hydrocarbons produced by lamalginite contain a significantly higher content of C20 tricyclic terpanes(TT),C21TT,C24 tetracyclic terpanes(TeT),C29 norhopane,and C28 regular sterane.Based on the pyrolysis and biomarker compound parameters,telalginite has a higher conversion rate for hydrocarbons than lamalginite in the low-mature to mature stage,which is consistent with their kinetic analysis.Lamalginite source rock displays a much narrower distribution of activation energies than telalginite source rocks.Such narrower activation energy distribution effectively narrows the main stage of hydrocarbon generation.In addition,the activation energy distribution of lamalginite concentrated in the high-value interval,indicating the characteristics of the relatively lagging hydrocarbon generation of lamalginite.
基金supported by the National Major Science and Technology Project“Experimental Evaluation of Spatial Characteristics and Seepage Law of FracturedPorous Reservoir”(No.:2016ZX05052-002-001)National Major Science and Technology Project“Invasion Mechanism of Fractured-Porous(Cave)and Bottom Water Gas Reservoir and Its Impact on Gas Reservoir Stability and Recovery”(No.:2017ZX05030-003-003-001)China National Petroleum Corporation Scientific Research and Technology Development Project(No.2016B-1501).
文摘Tight sandstone gas reservoirs commonly contain water,so liquid loading often appears near wellbores,leading to production decline and even shutdown of gas wells.Therefore,the study on the change of water saturation near wellbores is of great significance to understanding the water production mechanisms of gas wells.In this paper,a set of physical simulation experiment procedures of identifying the change of water saturation near wellbores was designed according to the principle of radial well seepage of gas wells,and the production performance after vertical well fracturing in gas reservoirs was simulated by connecting tight cores with a diameter of 10.5 cm,3.8 cm and 2.5 cm in series in a descending order of distance.According to the depressurizing production mode of gas wells,tubes with small diameters of 20,30,40 and 50 mm were used to simulate gas well tubing to control the gas production rate.And the change of water saturation near wellbore in the process of depletion production and its influencing factors were investigated.Finally,combined with actual data of production wells,the water saturation and water production of gas wells near wellbores and in different zones were calculated at the above four different small diameters of tubes and the changes thereof were also analyzed.The following results were obtained.First,each gas production rate corresponds to a critical water saturation.When the initial water saturation is lower than the critical value,the formation water flowing near the wellbore and in the middle zone can be carried out along with the production of gas and no liquid loading is formed.Second,when the initial water saturation is higher than the critical value,a large amount of formation water migrating from the far-wellbore zones accumulates near the wellbore,and thus liquid loading occurs at the bottom hole.Third,when the initial water saturation is equal to the critical value,the higher the gas production rate is,the more easily liquid loading tends to form near the wellbore.Fourth,for the same water saturation,water production increases and recovery factor decreases with the increase of gas production rate.In conclusion,the cumulative water production chart of a gas well generated by the physical simulation experiment method proposed in this paper agrees well with the water production behavior of the corresponding gas well.The research results are conducive to the effective prediction of gas well water production and can be used as guidance for the reasonable gas well water control.
基金supported by Research Foundation of China University of Petroleum-Beijing at Karamay(No.XQZX20210004)。
文摘Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie Formation(Es3)on the gentle southern slope of the Gubei Sag,Bohai Bay Basin and draw some conclusions that,for complex sand bodies,with the increase in water level the distributary channels bifurcate frequently,from a simple branching shape to a network shape along with the increase in the development of crevasse splays,mouth bars and sheet sands.For single sand bodies,with an increase in water level in the slope zone of the lake basin close to the source area,the superimposition style transitioned from vertical cutting-stacking and lateral isolation to vertical stitching,isolation and lateral stitching.However,in the central zone of the lake basin far from the source area,the superimposition style transitioned from vertical stitching and lateral stitching to vertical isolation and lateral isolation.When water level stays stable,the greater the distance from the source area the greater the disaggregation ratio of a single sand body.At the same distance from the source area,higher water level tends to result in greater disaggregation ratio of a single sand body.
基金Supported by Research Fund for the Doctoral Program of Higher Education of China:Theoretical model study of non-equilibrium phase state for high temperature and high pressure muticomposition condensate gas(20115121110002).
文摘The condensate blockage causes a substantial decrease in well productivity for gas condensate reservoirs.Based on the previous studies,a novel experimental method was designed to evaluate condensate blockage and the mitigating effect of gas injection.The method considers the stacking effect in the near wellbore region and the gas flow in the far wellbore region.There is an intermediate vessel containing condensate gas at the entrance of core holder in the experimental apparatus.In the process of pressure depletion experiment in a long core model,the vessel is connected to the core and the pressure of the vessel remains above the dew point pressure.The seriousness of condensate blockage is investigated by this research.When pressure drops to maximum retrograde condensation pressure,the gas permeability decreases by 80%compared with the initial gas permeability.Contrastive experiments were conducted to study the removal effect of different injection fluids and different injection volumes.The results show that CO2 injection is more effective than methanol in mitigating condensate blockage and the optimal CO2 injection volume is around 0.15 HCPV。
