Geothermal energy is a kind of renewable,sustainable and clean energy resource.Geothermal energy is abundant in carbonate reservoirs.However,low matrix permeability limits its exploitation.The super-critical carbon di...Geothermal energy is a kind of renewable,sustainable and clean energy resource.Geothermal energy is abundant in carbonate reservoirs.However,low matrix permeability limits its exploitation.The super-critical carbon dioxide(SC-CO_(2))jet fracturing is expected to efficiently stimulate the carbonate geothermal reservoirs and achieve the storage of CO_(2) simultaneously.In this paper,we established a transient seepage and fluid-thermo-mechanical coupled model to analyze the impact performance of sc-CO_(2) jet fracturing.The mesh-based parallel code coupling interface was employed to couple the fluid and solid domains by exchanging the data through the mesh interface.The physical properties change of sC-CO_(2) with temperature were considered in the numerical model.Results showed that SC-CO_(2) jet frac-turing is superior to water-jet fracturing with respect to jetting velocity,particle trajectory and pene-trability.Besides,stress distribution on the carbonate rock showed that the tensile and shear failure would more easily occur by SC-CO_(2) jet than that by water jet.Moreover,pressure and temperature control the jet field and seepage field of sC-CO_(2) simultaneously.Increasing the jet temperature can effectively enhance the impingement effect and seepage process by decreasing the viscosity and density of SC-CO_(2).The key findings are expected to provide a theoretical basis and design reference for applying SC-CO_(2) jet fracturing in carbonate geothermal reservoirs.展开更多
A mathematical model for coupled multiphase fluid flow and sedi- mentation deformation is developed based on fluid-solid interaction mechanism.A finite difference-finite element numerical approach is presented.The res...A mathematical model for coupled multiphase fluid flow and sedi- mentation deformation is developed based on fluid-solid interaction mechanism.A finite difference-finite element numerical approach is presented.The results of an example show that the fluid-solid coupled effect has great influence on multiphase fluid flow and reservoir recovery performances,and the coupled model has practical significance for oilfield development.展开更多
A large language model(LLM)is constructed to address the sophisticated demands of data retrieval and analysis,detailed well profiling,computation of key technical indicators,and the solutions to complex problems in re...A large language model(LLM)is constructed to address the sophisticated demands of data retrieval and analysis,detailed well profiling,computation of key technical indicators,and the solutions to complex problems in reservoir performance analysis(RPA).The LLM is constructed for RPA scenarios with incremental pre-training,fine-tuning,and functional subsystems coupling.Functional subsystem and efficient coupling methods are proposed based on named entity recognition(NER),tool invocation,and Text-to-SQL construction,all aimed at resolving pivotal challenges in developing the specific application of LLMs for RDA.This study conducted a detailed accuracy test on feature extraction models,tool classification models,data retrieval models and analysis recommendation models.The results indicate that these models have demonstrated good performance in various key aspects of reservoir dynamic analysis.The research takes some injection and production well groups in the PK3 Block of the Daqing Oilfield as an example for testing.Testing results show that our model has significant potential and practical value in assisting reservoir engineers with RDA.The research results provide a powerful support to the application of LLM in reservoir performance analysis.展开更多
The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichm...The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.展开更多
In view of the problem that a single modeling method cannot predict the distribution of microfacies, a new idea of coupling modeling method to comprehensively predict the distribution of sedimentary microfacies was pr...In view of the problem that a single modeling method cannot predict the distribution of microfacies, a new idea of coupling modeling method to comprehensively predict the distribution of sedimentary microfacies was proposed, breaking the tradition that different sedimentary microfacies used the same modeling method in the past. Because different sedimentary microfacies have different distribution characteristics and geometric shapes, it is more accurate to select different simulation methods for prediction. In this paper, the coupling modeling method was to establish the distribution of sedimentary microfacies with simple geometry through the point indicating process simulation, and then predict the microfacies with complex spatial distribution through the sequential indicator simulation method. Taking the DC block of Bohai basin as an example, a high-precision reservoir sedimentary microfacies model was established by the above coupling modeling method, and the model verification results showed that the sedimentary microfacies model had a high consistency with the underground. The coupling microfacies modeling method had higher accuracy and reliability than the traditional modeling method, which provided a new idea for the prediction of sedimentary microfacies.展开更多
Using gas and rock samples from major petroliferous basins in the world,the helium content,composition,isotopic compositions and the U and Th contents in rocks are analyzed to clarify the helium enrichment mechanism a...Using gas and rock samples from major petroliferous basins in the world,the helium content,composition,isotopic compositions and the U and Th contents in rocks are analyzed to clarify the helium enrichment mechanism and distribution pattern and the exploration ideas for helium-rich gas reservoirs.It is believed that the formation of helium-rich gas reservoirs depends on the amount of helium supplied to the reservoir and the degree of helium dilution by natural gas,and that the reservoir-forming process can be summarized as"multi-source helium supply,main-source helium enrichment,helium-nitrogen coupling,and homogeneous symbiosis".Helium mainly comes from the radioactive decay of U and Th in rocks.All rocks contain trace amounts of U and Th,so they are effective helium sources.Especially,large-scale ancient basement dominated by granite or metamorphic rocks is the main helium source.The helium generated by the decay of U and Th in the ancient basement in a long geologic history,together with the nitrogen generated by the cracking of the inorganic nitrogenous compounds in the basement rocks,is dissolved in the water and preserved.With the tectonic uplift,the ground water is transported upward along the fracture to the gas reservoirs,with helium and nitrogen released.Thus,the reservoirs are enriched with both helium and nitrogen,which present a clear concomitant and coupling relationship.In tensional basins in eastern China,where tectonic activities are strong,a certain proportion of mantle-derived helium is mixed in the natural gas.The helium-rich gas reservoirs are mostly located in normal or low-pressure zones above ancient basement with fracture communication,which later experience substantial tectonic uplift and present relatively weak seal,low intensity of natural gas charging,and active groundwater.Helium exploration should focus on gas reservoirs with fractures connecting ancient basement,large tectonic uplift,relatively weak sealing capacity,insufficient natural gas charging intensity,and rich ancient formation water,depending on the characteristics of helium enrichment,beyond the traditional idea of searching for natural gas sweetspots and high-yield giant gas fields simultaneously.展开更多
The applicability of early time data in reservoir characterization is not always considered worthy.Early time data is usually controlled by wellbore storage effect.This effect may last for pseudo-radial flow or even b...The applicability of early time data in reservoir characterization is not always considered worthy.Early time data is usually controlled by wellbore storage effect.This effect may last for pseudo-radial flow or even boundary dominated flow.Eliminating this effect is an option for restoring real data.Using the data with this effect is another option that could be used successfully for reservoir characterization.This paper introduces new techniques for restoring disrupted data by wellbore storage at early time production.The proposed techniques are applicable for reservoirs depleted by horizontal wells and hydraulic fractures.Several analytical models describe early time data,controlled by wellbore storage effect,have been generated for both horizontal wells and horizontal wells intersecting multiple hydraulic fractures.The relationships of the peak points(humps)with the pressure,pressure derivative and production time have been mathematically formulated in this study for different wellbore storage coefficients.For horizontal wells,a complete set of type curves has been included for different wellbore lengths,skin factors and wellbore storage coefficients.Another complete set of type curves has been established for fractured formations based on the number of hydraulic fractures,spacing between fractures,and wellbore storage coefficient.The study has shown that early radial flow for short to moderate horizontal wells is the most affected by wellbore storage while for long horizontal wells;early linear flow is the most affected flow regime by wellbore storage effect.The study has also emphasized the applicability of early time data for characterizing the formations even though they could be controlled by wellbore storage effect.As a matter of fact,this paper has found out that wellbore storage dominated flow could have remarkable relationships with the other flow regimes might be developed during the entire production times.These relationships can be used to properly describe the formations and quantify some of their characteristics.展开更多
This paper demonstrates the use of a commercial simulator as a tool with which to optimize the SAGD （steam-assisted gravity drainage） start-up phase process. The factors affecting the start-up phase are the prime ta...This paper demonstrates the use of a commercial simulator as a tool with which to optimize the SAGD （steam-assisted gravity drainage） start-up phase process. The factors affecting the start-up phase are the prime targets. Among the key investigated factors are wellbore geometry effects, reservoir heterogeneity and circulation phase length. Each of the parameters was investigated via steam chamber development observation along the well pair length and the cross sections in the mid, toe and heel areas. In addition, the cumulative recovery in given time, steam-to-oil ratio and CDOR （calendar day oil rate） production data are used to backup the observations produced in the simulated model. Furthermore, an additional component developed during the research is a statistical modification of a layer cake model with which to create a heterogeneous reservoir to represent real reservoir conditions, based on Monte Carlo＇s simulation.展开更多
Understanding the hydrological effects of the Three Gorges Dam operation in the entire reservoir area is significant to achieving optimal dam regulation. In this paper, a large-scale coupled hydrological-hydrodynamic-...Understanding the hydrological effects of the Three Gorges Dam operation in the entire reservoir area is significant to achieving optimal dam regulation. In this paper, a large-scale coupled hydrological-hydrodynamic-dam operation model is developed to comprehensively evaluate the hydrological effects of the river-type Three Gorges Reservoir. The results show that the coupled model is effective for hydrological, hydrodynamic regime and hydropower simulations in the reservoir area. Dam operation could have a notable positive effect on flood control and could reduce the maximum daily flood peak by up to 26.2%. It also contributes a large amount of hydropower, approximately 94.27 TWh/year, and a water supply increase for the downstream area of up to 22% during the dry season. In the flood season, the water level at Cuntan would increase under the condition that the water level of the dam is higher than approximately 158 m due to dam operation. In the dry season, attention should be paid to the low flow velocity near the dam in the reservoir area.展开更多
Through a case study of the high-efficiency gas reservoir in Feixianguan Formation in the northeast Sichuan Basin, quantitative and semi-quantitative analyses of key elements such as hydrocarbon generation, migration ...Through a case study of the high-efficiency gas reservoir in Feixianguan Formation in the northeast Sichuan Basin, quantitative and semi-quantitative analyses of key elements such as hydrocarbon generation, migration and accumulation, and reservoir evolution as well as their interplay in the critical moment of reservoir formation controlled by the energy field were carried out, by means of numerical modeling of the energy field. It was found that the climax time for Permian hydrocarbon generation was Late Triassic-Early Jurassic and accumulation of oil and gas has resulted in large-scale paleoreservoirs in paleostructural traps in Feixianguan Formation, a process facilitated by fractures connecting the sources. The paleoreservoirs have been turned into high-efficiency gas kitchens due to pyrolysis, which resulted from deep burial at a temperature of 170―210 ℃ as induced by tremendously thick sedimentation in the foreland basin of Daba Mountain in Late Jurassic-Cretaceous period. Meanwhile, abundant acid gas like H2S produced from thermo-chemical sulfate reduction (TSR) at high temperatures leads to extensive dissolution of dolostone in the paleoreservoirs, which may in turn result in modification of the reservoirs and preservation of the reservoir rock porosity. The present distribution of gas reservoirs was ultimately determined in the processes of adjustment, cooling and decompression of the paleoreservoirs resulting from intense deformation in the front of Daba Mountain during the Himalayan orogeny.展开更多
基金the National Key R&D Program of China(No.2019YFB1504102).
文摘Geothermal energy is a kind of renewable,sustainable and clean energy resource.Geothermal energy is abundant in carbonate reservoirs.However,low matrix permeability limits its exploitation.The super-critical carbon dioxide(SC-CO_(2))jet fracturing is expected to efficiently stimulate the carbonate geothermal reservoirs and achieve the storage of CO_(2) simultaneously.In this paper,we established a transient seepage and fluid-thermo-mechanical coupled model to analyze the impact performance of sc-CO_(2) jet fracturing.The mesh-based parallel code coupling interface was employed to couple the fluid and solid domains by exchanging the data through the mesh interface.The physical properties change of sC-CO_(2) with temperature were considered in the numerical model.Results showed that SC-CO_(2) jet frac-turing is superior to water-jet fracturing with respect to jetting velocity,particle trajectory and pene-trability.Besides,stress distribution on the carbonate rock showed that the tensile and shear failure would more easily occur by SC-CO_(2) jet than that by water jet.Moreover,pressure and temperature control the jet field and seepage field of sC-CO_(2) simultaneously.Increasing the jet temperature can effectively enhance the impingement effect and seepage process by decreasing the viscosity and density of SC-CO_(2).The key findings are expected to provide a theoretical basis and design reference for applying SC-CO_(2) jet fracturing in carbonate geothermal reservoirs.
文摘A mathematical model for coupled multiphase fluid flow and sedi- mentation deformation is developed based on fluid-solid interaction mechanism.A finite difference-finite element numerical approach is presented.The results of an example show that the fluid-solid coupled effect has great influence on multiphase fluid flow and reservoir recovery performances,and the coupled model has practical significance for oilfield development.
基金Supported by the National Talent Fund of the Ministry of Science and Technology of China(20230240011)China University of Geosciences(Wuhan)Research Fund(162301192687)。
文摘A large language model(LLM)is constructed to address the sophisticated demands of data retrieval and analysis,detailed well profiling,computation of key technical indicators,and the solutions to complex problems in reservoir performance analysis(RPA).The LLM is constructed for RPA scenarios with incremental pre-training,fine-tuning,and functional subsystems coupling.Functional subsystem and efficient coupling methods are proposed based on named entity recognition(NER),tool invocation,and Text-to-SQL construction,all aimed at resolving pivotal challenges in developing the specific application of LLMs for RDA.This study conducted a detailed accuracy test on feature extraction models,tool classification models,data retrieval models and analysis recommendation models.The results indicate that these models have demonstrated good performance in various key aspects of reservoir dynamic analysis.The research takes some injection and production well groups in the PK3 Block of the Daqing Oilfield as an example for testing.Testing results show that our model has significant potential and practical value in assisting reservoir engineers with RDA.The research results provide a powerful support to the application of LLM in reservoir performance analysis.
文摘The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.
文摘In view of the problem that a single modeling method cannot predict the distribution of microfacies, a new idea of coupling modeling method to comprehensively predict the distribution of sedimentary microfacies was proposed, breaking the tradition that different sedimentary microfacies used the same modeling method in the past. Because different sedimentary microfacies have different distribution characteristics and geometric shapes, it is more accurate to select different simulation methods for prediction. In this paper, the coupling modeling method was to establish the distribution of sedimentary microfacies with simple geometry through the point indicating process simulation, and then predict the microfacies with complex spatial distribution through the sequential indicator simulation method. Taking the DC block of Bohai basin as an example, a high-precision reservoir sedimentary microfacies model was established by the above coupling modeling method, and the model verification results showed that the sedimentary microfacies model had a high consistency with the underground. The coupling microfacies modeling method had higher accuracy and reliability than the traditional modeling method, which provided a new idea for the prediction of sedimentary microfacies.
基金Supported by the National Natural Science Foundation of China(42141022,42272189)Project of Ministry of Natural Resources of China(QGYQZYPJ2022-1)CNPC Core Project(2021ZG12)。
文摘Using gas and rock samples from major petroliferous basins in the world,the helium content,composition,isotopic compositions and the U and Th contents in rocks are analyzed to clarify the helium enrichment mechanism and distribution pattern and the exploration ideas for helium-rich gas reservoirs.It is believed that the formation of helium-rich gas reservoirs depends on the amount of helium supplied to the reservoir and the degree of helium dilution by natural gas,and that the reservoir-forming process can be summarized as"multi-source helium supply,main-source helium enrichment,helium-nitrogen coupling,and homogeneous symbiosis".Helium mainly comes from the radioactive decay of U and Th in rocks.All rocks contain trace amounts of U and Th,so they are effective helium sources.Especially,large-scale ancient basement dominated by granite or metamorphic rocks is the main helium source.The helium generated by the decay of U and Th in the ancient basement in a long geologic history,together with the nitrogen generated by the cracking of the inorganic nitrogenous compounds in the basement rocks,is dissolved in the water and preserved.With the tectonic uplift,the ground water is transported upward along the fracture to the gas reservoirs,with helium and nitrogen released.Thus,the reservoirs are enriched with both helium and nitrogen,which present a clear concomitant and coupling relationship.In tensional basins in eastern China,where tectonic activities are strong,a certain proportion of mantle-derived helium is mixed in the natural gas.The helium-rich gas reservoirs are mostly located in normal or low-pressure zones above ancient basement with fracture communication,which later experience substantial tectonic uplift and present relatively weak seal,low intensity of natural gas charging,and active groundwater.Helium exploration should focus on gas reservoirs with fractures connecting ancient basement,large tectonic uplift,relatively weak sealing capacity,insufficient natural gas charging intensity,and rich ancient formation water,depending on the characteristics of helium enrichment,beyond the traditional idea of searching for natural gas sweetspots and high-yield giant gas fields simultaneously.
文摘The applicability of early time data in reservoir characterization is not always considered worthy.Early time data is usually controlled by wellbore storage effect.This effect may last for pseudo-radial flow or even boundary dominated flow.Eliminating this effect is an option for restoring real data.Using the data with this effect is another option that could be used successfully for reservoir characterization.This paper introduces new techniques for restoring disrupted data by wellbore storage at early time production.The proposed techniques are applicable for reservoirs depleted by horizontal wells and hydraulic fractures.Several analytical models describe early time data,controlled by wellbore storage effect,have been generated for both horizontal wells and horizontal wells intersecting multiple hydraulic fractures.The relationships of the peak points(humps)with the pressure,pressure derivative and production time have been mathematically formulated in this study for different wellbore storage coefficients.For horizontal wells,a complete set of type curves has been included for different wellbore lengths,skin factors and wellbore storage coefficients.Another complete set of type curves has been established for fractured formations based on the number of hydraulic fractures,spacing between fractures,and wellbore storage coefficient.The study has shown that early radial flow for short to moderate horizontal wells is the most affected by wellbore storage while for long horizontal wells;early linear flow is the most affected flow regime by wellbore storage effect.The study has also emphasized the applicability of early time data for characterizing the formations even though they could be controlled by wellbore storage effect.As a matter of fact,this paper has found out that wellbore storage dominated flow could have remarkable relationships with the other flow regimes might be developed during the entire production times.These relationships can be used to properly describe the formations and quantify some of their characteristics.
文摘This paper demonstrates the use of a commercial simulator as a tool with which to optimize the SAGD （steam-assisted gravity drainage） start-up phase process. The factors affecting the start-up phase are the prime targets. Among the key investigated factors are wellbore geometry effects, reservoir heterogeneity and circulation phase length. Each of the parameters was investigated via steam chamber development observation along the well pair length and the cross sections in the mid, toe and heel areas. In addition, the cumulative recovery in given time, steam-to-oil ratio and CDOR （calendar day oil rate） production data are used to backup the observations produced in the simulated model. Furthermore, an additional component developed during the research is a statistical modification of a layer cake model with which to create a heterogeneous reservoir to represent real reservoir conditions, based on Monte Carlo＇s simulation.
基金Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA23040500Youth Innovation Promotion Association,CAS,No.2021385Central Guidance on Local Science and Technology Development Fund of Chongqing City,No.2021000069。
文摘Understanding the hydrological effects of the Three Gorges Dam operation in the entire reservoir area is significant to achieving optimal dam regulation. In this paper, a large-scale coupled hydrological-hydrodynamic-dam operation model is developed to comprehensively evaluate the hydrological effects of the river-type Three Gorges Reservoir. The results show that the coupled model is effective for hydrological, hydrodynamic regime and hydropower simulations in the reservoir area. Dam operation could have a notable positive effect on flood control and could reduce the maximum daily flood peak by up to 26.2%. It also contributes a large amount of hydropower, approximately 94.27 TWh/year, and a water supply increase for the downstream area of up to 22% during the dry season. In the flood season, the water level at Cuntan would increase under the condition that the water level of the dam is higher than approximately 158 m due to dam operation. In the dry season, attention should be paid to the low flow velocity near the dam in the reservoir area.
基金the National Key Basic Research and Development Program of China (Grant No. 2001CB209100)
文摘Through a case study of the high-efficiency gas reservoir in Feixianguan Formation in the northeast Sichuan Basin, quantitative and semi-quantitative analyses of key elements such as hydrocarbon generation, migration and accumulation, and reservoir evolution as well as their interplay in the critical moment of reservoir formation controlled by the energy field were carried out, by means of numerical modeling of the energy field. It was found that the climax time for Permian hydrocarbon generation was Late Triassic-Early Jurassic and accumulation of oil and gas has resulted in large-scale paleoreservoirs in paleostructural traps in Feixianguan Formation, a process facilitated by fractures connecting the sources. The paleoreservoirs have been turned into high-efficiency gas kitchens due to pyrolysis, which resulted from deep burial at a temperature of 170―210 ℃ as induced by tremendously thick sedimentation in the foreland basin of Daba Mountain in Late Jurassic-Cretaceous period. Meanwhile, abundant acid gas like H2S produced from thermo-chemical sulfate reduction (TSR) at high temperatures leads to extensive dissolution of dolostone in the paleoreservoirs, which may in turn result in modification of the reservoirs and preservation of the reservoir rock porosity. The present distribution of gas reservoirs was ultimately determined in the processes of adjustment, cooling and decompression of the paleoreservoirs resulting from intense deformation in the front of Daba Mountain during the Himalayan orogeny.
