Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the ...Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.展开更多
The pore structure and oil content of shales have an important influence on the oil mobility and enrichment.In this study,the lacustrine shale samples from the Qingshankou Formation(Q1)of Songliao Basin were selected....The pore structure and oil content of shales have an important influence on the oil mobility and enrichment.In this study,the lacustrine shale samples from the Qingshankou Formation(Q1)of Songliao Basin were selected.TOC,pyrolysis,XRD and nitrogen adsorption were performed on the original and extracted shale samples.Then the influence of mineral composition and organic matter(OM)on the development of nano-scale pore,the oil phase states and mobility were analyzed.The Q1 shale samples can be sub-divided into three types according to the isotherm characteristics.Type A samples are characterized by high kerogen content,with oil mainly existing in the free phase state.Type B samples are characterized by medium kerogen content,oil mainly exists in the absorbed phase state.Type C samples are characterized by low kerogen content,with trace oil found in the absorbed phase state.Nano-scale organic pores are well developed in the Q1 Formation.Oil is primarily found in the pore spaces with diameters less than 10 nm,this being the pore size threshold for mobile shale oil.When TOC>2.0 wt%and EOM>1.0 wt%,Q1 Formation shale oil mobility is high,resulting in prospective drilling targets.展开更多
Dimethyl ether （DME） is a widely used industrial compound, and Shell developed a chemical EOR technique called DME- enhanced waterflood （DEW）. DME is applied as a miscible solvent for EOR application to enhance th...Dimethyl ether （DME） is a widely used industrial compound, and Shell developed a chemical EOR technique called DME- enhanced waterflood （DEW）. DME is applied as a miscible solvent for EOR application to enhance the performance of conventional waterflood. When DME is injected into the reservoir and contacts the oil, the first-contact miscibility process occurs, which leads to oil swelling and viscosity reduction. The reduction in oil density and viscosity improves oil mobility and reduces residual oil saturation, enhancing oil production. A numerical study based on compositional simulation has been developed to describe the phase behavior in the DEW model. An accurate compositional model is imperative because DME has a unique advantage of solubility in both oil and water. For DEW, oil recovery increased by 34% and 12% compared to conventional waterflood and CO2 flood, respectively. Compositional modeling and simulation of the DEW process indicated the unique solubility effect of DME on EOR performance.展开更多
Mobility is a crucial metric for assessing sweet spots of continental shale oil.However,due to the complexity of shale oil reservoirs characteristics and the lack of systematic analyses of factors influencing mobility...Mobility is a crucial metric for assessing sweet spots of continental shale oil.However,due to the complexity of shale oil reservoirs characteristics and the lack of systematic analyses of factors influencing mobility,the difference in shale oil mobility under multiple lithofacies control remains unclear,causing significant challenges for mobility evaluation and sweet spot prediction.This study examines continental shales of the Fengcheng Formation in the Mahu Sag,employing scanning electron microscopy(SEM),nitrogen adsorption(NA),nuclear magnetic resonance(NMR),spontaneous imbibition(SI),and contact angle measurements(CAM)to investigate the pore structure,connectivity,and wettability properties of different lithofacies shale.Quantitative analyses of shale movable oil content and saturation were conducted using multistep temperature pyrolysis(MTP)and NMR centrifugation techniques.Furthermore,the influence of reservoir characteristics,geochemical characteristics,and lamination development on shale oil mobility were discussed.Results indicate that larger pore diameter,higher imbibition slopes,and lower fractal dimensions of movable fluid pores(D2)correspond to higher movable oil saturation.Organic matter exerts a dual effect on shale movable oil content.When the TOC is below a threshold,the movable oil content gradually increases with TOC.Laminations exhibit favorable reservoir properties and light oil enrichment,enhancing shale oil mobility.Massive siltstone(MS)develops interconnected intergranular pores with the best pore structure and connectivity,the lowest D2 values,and the highest shale oil mobility.Laminated felsic shale(LFS)and laminated calcareous shale(LCS)exhibit moderate mobility,where the development of microfractures enhances fluid flow by connecting isolated pores into pore-fracture networks.In contrast,massive felsic shale(MFS)and bedded felsic shale(BFS)primarily develop intragranular dissolution pores with more complex structures and poorer connectivity,resulting in weaker mobility.A more accurate approach for assessing shale oil mobility has been presented,taking into account both total oil content and movable oil saturation.More importantly,this study establishes a comprehensive conceptual model illustrating the potential relationships among shale lithofacies,reservoir characteristics,and movable oil flow space in the study area.This research not only provides a systematic approach for assessing shale oil mobility but also deepens the understanding of flow mechanisms of continental shale oil,offering theoretical guidance for optimizing sweet spots in the Fengcheng Formation shale oil reservoirs of the Mahu Sag.展开更多
An accurate evaluation of the shale oil mobility is crucial to its cost-effective exploitation.This study presents a method to assess shale oil mobility by integrating the pore structure and oil states distributions.F...An accurate evaluation of the shale oil mobility is crucial to its cost-effective exploitation.This study presents a method to assess shale oil mobility by integrating the pore structure and oil states distributions.First,a set of three discrete organic extracts(EOM-A,B and C)were obtained by sequential extraction.The relationships among the EOMs and the oil states were inferred from the group compositions and fluorescence properties of the produced shale oil(free state).The results showed that EOMs A and B represent free oil in the open and closed pores,respectively,while the EOM-C represents adsorbed oil.Then,NMR T_(1)-T_(2)map is used to determine the T_(2-cutoff)values that indicate the pore size ranges of different oil states.Free oil resides mainly in larger pore space(T_(2)>0.5 ms),while the adsorbed oil in smaller pore space(0.2 ms<T_(2)<0.5 ms).Finally,the ratio of free to adsorbed oil(F/A)>0.5 and T_(2-cutoff)>1.0 ms suggest that the free oil in connected pores has the highest mobility.This work can provide a reference for evaluating the shale oil potential and prospectivity in other regions.展开更多
Shale oil occurs in free state （including condensate state）, adsorption state （adsorbed on kerogen and mineral particles） and dissolved state （dissolved in natural gas, residual water, etc.） in shales and adjace...Shale oil occurs in free state （including condensate state）, adsorption state （adsorbed on kerogen and mineral particles） and dissolved state （dissolved in natural gas, residual water, etc.） in shales and adjacent layers. The characterization of the occurrence of different hydrocarbons in shale oil, especially the quantitative separation of free hydrocarbons （mobile oil）, has been the current focus of shale oil research. Taken the shale oil from the Muli coalfield in Qilian Mountain as an example, this work extracted shale samples with organic solvents of different polarity to obtain different occurrence states of hydrocarbons in the oil-bearing shale and to reveal the compositional differences of the hydrocarbons. The result may provide new geochemical information for the occurrence and mobility of shale oil.展开更多
To reveal the complex crude oil-CO_(2) interaction mechanism and oil mobilization behavior during CO_(2) huff-n-puff in shale-type shale oil reservoirs,CO_(2) huff-n-puff experiments with on-line nuclear magnetic reso...To reveal the complex crude oil-CO_(2) interaction mechanism and oil mobilization behavior during CO_(2) huff-n-puff in shale-type shale oil reservoirs,CO_(2) huff-n-puff experiments with on-line nuclear magnetic resonance monitoring were conducted on Gulong shale cores,combined with the prediction model of CO_(2) dynamic diffusion coefficient,the flow mechanism and factors influencing oil mobilization during CO_(2) huff and puff in Gulong shale oil reservoirs are studied,and the diffusion and mass transfer behavior of CO_(2) in shale is investigated.The results show that at the injection stage,CO_(2) invades into macropores near the injection end,and drives part of the crude oil to micropores in the deep part of the core.At the shut-in stage,the crude oil gradually reflows to macropores near the injection end and is redistributed in the core.At the production stage,the oil mobilization zone is gradually expanded from the production end(injection end)to the deep part of the core.The contribution ratio of produced oil from macropores and micropores is about 8︰3 after production.The diffusion coefficient of CO_(2) in shale porous media gradually decreases with the advance of diffusion front at shut-in stage.The better the porosity and permeability of core samples,the higher the CO_(2) concentration at diffusion front,the greater the CO_(2) diffusion coefficient,and the slower the diffusion decline rate is.Increasing the huff and puff cycles could effectively enhance oil displacement efficiency,though its impact on the crude oil mobilization zone remains insignificant.The crude oil in small pores of the small layer with undeveloped laminae is difficult to be produced during CO_(2) huff and puff,and the oil recovery is only 12.72%.The crude oil in macropores and micropores of the small layer with developed laminae can be effectively mobilized during CO_(2) huff and puff,and the oil recovery can reach 39.11%.展开更多
Comparative analyses of petroleum generation potential,reservoir volume,frackability,and oil mobility were conducted on 102 shale cores from the Dongpu Depression.Results show the shale has high organic matter content...Comparative analyses of petroleum generation potential,reservoir volume,frackability,and oil mobility were conducted on 102 shale cores from the Dongpu Depression.Results show the shale has high organic matter contents composed of oil-prone type I and type II kerogens within the oil window.Various types of pores and fractures exist in the shale,with a porosity of up to 14.9%.The shale has high brittle mineral contents,extensive fractures,and high potential for oil mobility due to high seepage capacity and overpressure.Although the petroleum generation potential of the shale at Well PS18-8 is relatively greater than that at Well PS18-1,oil content of the latter is greater due to the greater TOC.The porosity and fracture density observed in Well PS18-1 are greater and more conducive to shale oil enrichment.Although the shales in Wells PS18-1 and PS18-8 have similar brittle mineral contents,the former is more favorable for anthropogenic fracturing due to a higher preexisting fracture density.Besides,the shale at Well PS18-1 has a higher seepage capacity and overpressure and therefore a higher oil mobility.The fracture density and overpressure play key roles in shale oil enrichment.展开更多
A series of spontaneous imbibition(SI)tests of tight oil were performed,together with oil distribution scans by computed tomography(CT)and nuclear magnetic resonance(NMR).Thus,the best surfactants to optimize the SI e...A series of spontaneous imbibition(SI)tests of tight oil were performed,together with oil distribution scans by computed tomography(CT)and nuclear magnetic resonance(NMR).Thus,the best surfactants to optimize the SI effect were obtained,the basic requirements to surfactants for efficient SI were determined,and the oil mobilization by SI revealed.The results show that anionic surfactants significantly outperform non-ionic,cationic,and zwitterionic ones in SI process.Excellent systems can be further obtained by mixing anionic surfactants with others(e.g.1:1 mixtures of AES:EHSB).The requirements to interfacial properties of surfactants for achieving efficient SI at permeabilities of 0.05,0.5,and 5.0 mD are as follows:10~0 mN/m,<40°;10-1-10~0 mN/m,<55°;and 10-1-10~0 mN/m,<70°,respectively.Although a high oil recovery of 38.5%by SI was achieved in small cylindrical cores(φ2.5 cm×3.0 cm),the joint SI and CT tests in larger,cube-shaped cores(5.0 cm×5.0 cm×5.0 cm)showed that the SI process could only remove the oil from the outermost few millimeters of the cores with permeabilities of 0.05 and 0.1 mD,indicating the great difficulty encountered for their development.The NMR showed that the SI treatment preferentially removed oil from smaller pores rather than medium or large pores.展开更多
CO_(2) flooding has emerged as a valuable method for enhancing oil recovery(EOR)in fossil fuel reservoirs.However,the impact of micro-heterogeneity,particularly variations in pore sizes,on CO_(2) flooding following wa...CO_(2) flooding has emerged as a valuable method for enhancing oil recovery(EOR)in fossil fuel reservoirs.However,the impact of micro-heterogeneity,particularly variations in pore sizes,on CO_(2) flooding following water flooding in conglomerate reservoirs remains insufficiently understood.This study introduces an advanced visual model integrating outcrop and nuclear magnetic resonance(NMR)analyses to overcome the limitations of traditional micromodels.Simulating reservoir conditions,the model evaluates oil displacement and sweep efficiency through a fractal-based pore classification system,categorizing pores into four types:small pores(P1),medium pores(P2 and P3),and large pores(P4).This classification provides a comprehensive analysis of residual oil patterns during water and CO_(2) flooding.Results show that water flooding primarily displaces oil from larger pores(P3 and P4),leaving residual oil trapped in smaller pores(P1 and P2).After 0.4 PV injection,oil begins migrating from smaller to larger pores(P4),reaching an oil recovery efficiency of 28.91%at 0.8 PV.In contrast,CO_(2) flooding significantly expands the sweep area and improves displacement efficiency despite minor gas channeling.NMR analysis indicates that CO_(2) flooding rapidly mobilizes oil in large pores(P4),while its effect on smaller pores(P1 and P2)remains limited.The cumulative signal amplitude decreases from 2914 to 2498,resulting in a displacement efficiency of 10.15%and a total recovery factor of 39.06%.This study provides valuable insights into optimizing CO_(2) immiscible flooding strategies and improving oil recovery efficiency in tight conglomerate reservoirs.展开更多
The present research is to experimentally study the joint effects of external pressure and vibratory excitations of low frequency on oil slug mobilization and flow in a capillary model.During and after the oil slug mo...The present research is to experimentally study the joint effects of external pressure and vibratory excitations of low frequency on oil slug mobilization and flow in a capillary model.During and after the oil slug mobilization,the flow phenomena and pressure drop variation across the model are investigated.The distance travelled by the oil slug subjected to various external pressure and vibratory excitations are also studied.The experimental results obtained indicate that the external vibratory excitation acting on the model has positive effect on the flow and mobilization of the oil slug in the model.It is found in the research,with the application of the excitation,the contact angle between the oil slug and tube-wall is changed;the maximum pressure required to mobilize the oil slug is reduced accordingly;and the oil slug travel distance is increased in comparing with that without external excitations.This research contributes to the comprehension of improved liquid mobilization in porous media under the application of external excitations.The finding of the research is significant for studying the two-phase liquid flow in porous media subjected to external excitations and provides insights for Enhanced Oil Recovery with waterflooding and vibratory stimulations.展开更多
This research studies the motion of immiscible two-phase liquid flow in a capillary tube through a numerical approach employing the volume of fluid method,for simulating the core-annular flow and water flooding in oil...This research studies the motion of immiscible two-phase liquid flow in a capillary tube through a numerical approach employing the volume of fluid method,for simulating the core-annular flow and water flooding in oil reservoirs of porous media.More specifically,the simulations are a representation of water flooding at a pore scale.A capillary tube model is established with ANSYS Fluent and verified.The numerical results matches well with the existing data available in the literature.Penetration of a less viscous liquid in a liquid of higher viscosity and the development of a residual wetting film of the higher viscosity liquid are thoroughly investigated.The effects of Capillary number,Reynolds Number and Viscosity ratio on the residual wetting film are studied in detail,as the thickness is directly related to the residual oil left in the porous media after water flooding.It should be noticed that the liquids considered in this research can be any liquids of different viscosity not necessarily oil and water.The results of this study can be used as guidance in the field of water flooding.展开更多
基金Supported by Leading Talent Program of Autonomous Region(2022TSYCLJ0070)PetroChina Prospective and Basic Technological Project(2021DJ0108)Natural Science Foundation for Outstanding Young People in Shandong Province(ZR2022YQ30).
文摘Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.
基金financially supported by the National Natural Science Foundation of China(No.41972156)the Science and Technology Project of Heilongjiang Province(No.2020ZX05A01)
文摘The pore structure and oil content of shales have an important influence on the oil mobility and enrichment.In this study,the lacustrine shale samples from the Qingshankou Formation(Q1)of Songliao Basin were selected.TOC,pyrolysis,XRD and nitrogen adsorption were performed on the original and extracted shale samples.Then the influence of mineral composition and organic matter(OM)on the development of nano-scale pore,the oil phase states and mobility were analyzed.The Q1 shale samples can be sub-divided into three types according to the isotherm characteristics.Type A samples are characterized by high kerogen content,with oil mainly existing in the free phase state.Type B samples are characterized by medium kerogen content,oil mainly exists in the absorbed phase state.Type C samples are characterized by low kerogen content,with trace oil found in the absorbed phase state.Nano-scale organic pores are well developed in the Q1 Formation.Oil is primarily found in the pore spaces with diameters less than 10 nm,this being the pore size threshold for mobile shale oil.When TOC>2.0 wt%and EOM>1.0 wt%,Q1 Formation shale oil mobility is high,resulting in prospective drilling targets.
基金supported by the Energy Efficiency & Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) of the Ministry of Trade, Industry, & Energy, Republic of Korea (No. 20152520100760)
文摘Dimethyl ether （DME） is a widely used industrial compound, and Shell developed a chemical EOR technique called DME- enhanced waterflood （DEW）. DME is applied as a miscible solvent for EOR application to enhance the performance of conventional waterflood. When DME is injected into the reservoir and contacts the oil, the first-contact miscibility process occurs, which leads to oil swelling and viscosity reduction. The reduction in oil density and viscosity improves oil mobility and reduces residual oil saturation, enhancing oil production. A numerical study based on compositional simulation has been developed to describe the phase behavior in the DEW model. An accurate compositional model is imperative because DME has a unique advantage of solubility in both oil and water. For DEW, oil recovery increased by 34% and 12% compared to conventional waterflood and CO2 flood, respectively. Compositional modeling and simulation of the DEW process indicated the unique solubility effect of DME on EOR performance.
基金supported by National Natural Science Foundation of China(42272137 and U24A20592)the Strategic Cooperation Technology Projecti of CNPC and CUPB(ZLZX2020-01-05)AAPG Foundation Grants-in-Aid.
文摘Mobility is a crucial metric for assessing sweet spots of continental shale oil.However,due to the complexity of shale oil reservoirs characteristics and the lack of systematic analyses of factors influencing mobility,the difference in shale oil mobility under multiple lithofacies control remains unclear,causing significant challenges for mobility evaluation and sweet spot prediction.This study examines continental shales of the Fengcheng Formation in the Mahu Sag,employing scanning electron microscopy(SEM),nitrogen adsorption(NA),nuclear magnetic resonance(NMR),spontaneous imbibition(SI),and contact angle measurements(CAM)to investigate the pore structure,connectivity,and wettability properties of different lithofacies shale.Quantitative analyses of shale movable oil content and saturation were conducted using multistep temperature pyrolysis(MTP)and NMR centrifugation techniques.Furthermore,the influence of reservoir characteristics,geochemical characteristics,and lamination development on shale oil mobility were discussed.Results indicate that larger pore diameter,higher imbibition slopes,and lower fractal dimensions of movable fluid pores(D2)correspond to higher movable oil saturation.Organic matter exerts a dual effect on shale movable oil content.When the TOC is below a threshold,the movable oil content gradually increases with TOC.Laminations exhibit favorable reservoir properties and light oil enrichment,enhancing shale oil mobility.Massive siltstone(MS)develops interconnected intergranular pores with the best pore structure and connectivity,the lowest D2 values,and the highest shale oil mobility.Laminated felsic shale(LFS)and laminated calcareous shale(LCS)exhibit moderate mobility,where the development of microfractures enhances fluid flow by connecting isolated pores into pore-fracture networks.In contrast,massive felsic shale(MFS)and bedded felsic shale(BFS)primarily develop intragranular dissolution pores with more complex structures and poorer connectivity,resulting in weaker mobility.A more accurate approach for assessing shale oil mobility has been presented,taking into account both total oil content and movable oil saturation.More importantly,this study establishes a comprehensive conceptual model illustrating the potential relationships among shale lithofacies,reservoir characteristics,and movable oil flow space in the study area.This research not only provides a systematic approach for assessing shale oil mobility but also deepens the understanding of flow mechanisms of continental shale oil,offering theoretical guidance for optimizing sweet spots in the Fengcheng Formation shale oil reservoirs of the Mahu Sag.
基金supported by the National Natural Science Foundation of China(Grant No.41972156)the Science and Technology Project of Heilongjiang Province(Grant No.2020ZX05A01).
文摘An accurate evaluation of the shale oil mobility is crucial to its cost-effective exploitation.This study presents a method to assess shale oil mobility by integrating the pore structure and oil states distributions.First,a set of three discrete organic extracts(EOM-A,B and C)were obtained by sequential extraction.The relationships among the EOMs and the oil states were inferred from the group compositions and fluorescence properties of the produced shale oil(free state).The results showed that EOMs A and B represent free oil in the open and closed pores,respectively,while the EOM-C represents adsorbed oil.Then,NMR T_(1)-T_(2)map is used to determine the T_(2-cutoff)values that indicate the pore size ranges of different oil states.Free oil resides mainly in larger pore space(T_(2)>0.5 ms),while the adsorbed oil in smaller pore space(0.2 ms<T_(2)<0.5 ms).Finally,the ratio of free to adsorbed oil(F/A)>0.5 and T_(2-cutoff)>1.0 ms suggest that the free oil in connected pores has the highest mobility.This work can provide a reference for evaluating the shale oil potential and prospectivity in other regions.
基金funded by the Science and Technology Innovation Fund of Petro China(grant No.2014D-5006-0105)the National Natural Science Foundation of China(grant No.41273066)
文摘Shale oil occurs in free state （including condensate state）, adsorption state （adsorbed on kerogen and mineral particles） and dissolved state （dissolved in natural gas, residual water, etc.） in shales and adjacent layers. The characterization of the occurrence of different hydrocarbons in shale oil, especially the quantitative separation of free hydrocarbons （mobile oil）, has been the current focus of shale oil research. Taken the shale oil from the Muli coalfield in Qilian Mountain as an example, this work extracted shale samples with organic solvents of different polarity to obtain different occurrence states of hydrocarbons in the oil-bearing shale and to reveal the compositional differences of the hydrocarbons. The result may provide new geochemical information for the occurrence and mobility of shale oil.
基金Supported by the National Natural Science Foundation of China(520743198)Scientific and Technological Problems Tackling Project of Heilongjiang Province(DQYT-2022-JS-761).
文摘To reveal the complex crude oil-CO_(2) interaction mechanism and oil mobilization behavior during CO_(2) huff-n-puff in shale-type shale oil reservoirs,CO_(2) huff-n-puff experiments with on-line nuclear magnetic resonance monitoring were conducted on Gulong shale cores,combined with the prediction model of CO_(2) dynamic diffusion coefficient,the flow mechanism and factors influencing oil mobilization during CO_(2) huff and puff in Gulong shale oil reservoirs are studied,and the diffusion and mass transfer behavior of CO_(2) in shale is investigated.The results show that at the injection stage,CO_(2) invades into macropores near the injection end,and drives part of the crude oil to micropores in the deep part of the core.At the shut-in stage,the crude oil gradually reflows to macropores near the injection end and is redistributed in the core.At the production stage,the oil mobilization zone is gradually expanded from the production end(injection end)to the deep part of the core.The contribution ratio of produced oil from macropores and micropores is about 8︰3 after production.The diffusion coefficient of CO_(2) in shale porous media gradually decreases with the advance of diffusion front at shut-in stage.The better the porosity and permeability of core samples,the higher the CO_(2) concentration at diffusion front,the greater the CO_(2) diffusion coefficient,and the slower the diffusion decline rate is.Increasing the huff and puff cycles could effectively enhance oil displacement efficiency,though its impact on the crude oil mobilization zone remains insignificant.The crude oil in small pores of the small layer with undeveloped laminae is difficult to be produced during CO_(2) huff and puff,and the oil recovery is only 12.72%.The crude oil in macropores and micropores of the small layer with developed laminae can be effectively mobilized during CO_(2) huff and puff,and the oil recovery can reach 39.11%.
基金This study was fnancially supported by the China Postdoctoral Science Foundation(2019M660054)Science Foundation of China University of Petroleum(Beijing)(2462019BJRC005)+3 种基金Strategic Cooperation Technology Projects of CNPC and CUPB(ZLZX2020-01-05)Natural Science Foundation of China(41872148,41872128)NSFC Basic Research Program on Deep Petroleum Resource Accumulation and Key Engineering Technologies(U19B6003-02)the Science Projects of the Sinopec Zhongyuan Oilfeld Company(P15022).
文摘Comparative analyses of petroleum generation potential,reservoir volume,frackability,and oil mobility were conducted on 102 shale cores from the Dongpu Depression.Results show the shale has high organic matter contents composed of oil-prone type I and type II kerogens within the oil window.Various types of pores and fractures exist in the shale,with a porosity of up to 14.9%.The shale has high brittle mineral contents,extensive fractures,and high potential for oil mobility due to high seepage capacity and overpressure.Although the petroleum generation potential of the shale at Well PS18-8 is relatively greater than that at Well PS18-1,oil content of the latter is greater due to the greater TOC.The porosity and fracture density observed in Well PS18-1 are greater and more conducive to shale oil enrichment.Although the shales in Wells PS18-1 and PS18-8 have similar brittle mineral contents,the former is more favorable for anthropogenic fracturing due to a higher preexisting fracture density.Besides,the shale at Well PS18-1 has a higher seepage capacity and overpressure and therefore a higher oil mobility.The fracture density and overpressure play key roles in shale oil enrichment.
基金the National Natural Science Foundation of China(Grant No.52474071)for their financial support。
文摘A series of spontaneous imbibition(SI)tests of tight oil were performed,together with oil distribution scans by computed tomography(CT)and nuclear magnetic resonance(NMR).Thus,the best surfactants to optimize the SI effect were obtained,the basic requirements to surfactants for efficient SI were determined,and the oil mobilization by SI revealed.The results show that anionic surfactants significantly outperform non-ionic,cationic,and zwitterionic ones in SI process.Excellent systems can be further obtained by mixing anionic surfactants with others(e.g.1:1 mixtures of AES:EHSB).The requirements to interfacial properties of surfactants for achieving efficient SI at permeabilities of 0.05,0.5,and 5.0 mD are as follows:10~0 mN/m,<40°;10-1-10~0 mN/m,<55°;and 10-1-10~0 mN/m,<70°,respectively.Although a high oil recovery of 38.5%by SI was achieved in small cylindrical cores(φ2.5 cm×3.0 cm),the joint SI and CT tests in larger,cube-shaped cores(5.0 cm×5.0 cm×5.0 cm)showed that the SI process could only remove the oil from the outermost few millimeters of the cores with permeabilities of 0.05 and 0.1 mD,indicating the great difficulty encountered for their development.The NMR showed that the SI treatment preferentially removed oil from smaller pores rather than medium or large pores.
基金supported by the National Science and Technology Major Project for New Oil and Gas Exploration and Development,including the project titled Exploration and Development Technology and Integrated Demonstration of Paleogene Continental Shale Oil in Jiyang Depression,Bohai Bay Basin,3D Development Optimization Control and Enhanced Oil Recovery Technology(2024ZD1405103)the project titled CO_(2)Flooding for Improved Recovery and Long-Term Storage Technology,Research on Key Engineering Technology and Equipment of the Whole Process of CO_(2)Flooding and Storage(2024ZD1406603)supported by the National Natural Science Foundation of China(52174035).
文摘CO_(2) flooding has emerged as a valuable method for enhancing oil recovery(EOR)in fossil fuel reservoirs.However,the impact of micro-heterogeneity,particularly variations in pore sizes,on CO_(2) flooding following water flooding in conglomerate reservoirs remains insufficiently understood.This study introduces an advanced visual model integrating outcrop and nuclear magnetic resonance(NMR)analyses to overcome the limitations of traditional micromodels.Simulating reservoir conditions,the model evaluates oil displacement and sweep efficiency through a fractal-based pore classification system,categorizing pores into four types:small pores(P1),medium pores(P2 and P3),and large pores(P4).This classification provides a comprehensive analysis of residual oil patterns during water and CO_(2) flooding.Results show that water flooding primarily displaces oil from larger pores(P3 and P4),leaving residual oil trapped in smaller pores(P1 and P2).After 0.4 PV injection,oil begins migrating from smaller to larger pores(P4),reaching an oil recovery efficiency of 28.91%at 0.8 PV.In contrast,CO_(2) flooding significantly expands the sweep area and improves displacement efficiency despite minor gas channeling.NMR analysis indicates that CO_(2) flooding rapidly mobilizes oil in large pores(P4),while its effect on smaller pores(P1 and P2)remains limited.The cumulative signal amplitude decreases from 2914 to 2498,resulting in a displacement efficiency of 10.15%and a total recovery factor of 39.06%.This study provides valuable insights into optimizing CO_(2) immiscible flooding strategies and improving oil recovery efficiency in tight conglomerate reservoirs.
文摘The present research is to experimentally study the joint effects of external pressure and vibratory excitations of low frequency on oil slug mobilization and flow in a capillary model.During and after the oil slug mobilization,the flow phenomena and pressure drop variation across the model are investigated.The distance travelled by the oil slug subjected to various external pressure and vibratory excitations are also studied.The experimental results obtained indicate that the external vibratory excitation acting on the model has positive effect on the flow and mobilization of the oil slug in the model.It is found in the research,with the application of the excitation,the contact angle between the oil slug and tube-wall is changed;the maximum pressure required to mobilize the oil slug is reduced accordingly;and the oil slug travel distance is increased in comparing with that without external excitations.This research contributes to the comprehension of improved liquid mobilization in porous media under the application of external excitations.The finding of the research is significant for studying the two-phase liquid flow in porous media subjected to external excitations and provides insights for Enhanced Oil Recovery with waterflooding and vibratory stimulations.
文摘This research studies the motion of immiscible two-phase liquid flow in a capillary tube through a numerical approach employing the volume of fluid method,for simulating the core-annular flow and water flooding in oil reservoirs of porous media.More specifically,the simulations are a representation of water flooding at a pore scale.A capillary tube model is established with ANSYS Fluent and verified.The numerical results matches well with the existing data available in the literature.Penetration of a less viscous liquid in a liquid of higher viscosity and the development of a residual wetting film of the higher viscosity liquid are thoroughly investigated.The effects of Capillary number,Reynolds Number and Viscosity ratio on the residual wetting film are studied in detail,as the thickness is directly related to the residual oil left in the porous media after water flooding.It should be noticed that the liquids considered in this research can be any liquids of different viscosity not necessarily oil and water.The results of this study can be used as guidance in the field of water flooding.
