The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in po...The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in pore structure,permeability,and mechanical strength of cap rocks under cyclic loads may impact the rock sealing integrity during the injection and recovery phases of UGS.In this work,the mechanical deformation and failure tests of rocks,as well as rock damage tests under alternating loads,are conducted to analyze the changes in the strength and permeability of rocks under multiple-cycle intense injection and recovery of UGS.Additionally,this study proposes an evaluation method for the dynamic sealing performance of UGS cap rocks under multi-cycle alternating loads.The findings suggest that the failure strength(70%)can be used as the critical value for rock failure,thus providing theoretical support for determining the upper limit of operating pressure and the number of injection-recovery cycles for the safe operation of a UGS system.展开更多
Despite the absence of regional cap rocks in the Lower Paleozoic for the entire Tazhong Low Rise,several sets of effective local cap rocks are well preserved on the Northern Slope.Of these the best is the Ordovician m...Despite the absence of regional cap rocks in the Lower Paleozoic for the entire Tazhong Low Rise,several sets of effective local cap rocks are well preserved on the Northern Slope.Of these the best is the Ordovician mudstone of the Sangtamu Formation; the second is the Silurian Red Mudstone Member of the Tatairtag Formation and the marl of the Ordovician Lianglitag Formation; and the third is the gray mudstone of the Silurian Kepingtag Formation.The dense limestone of the Ordovician Yingshan Formation and the gypsum of the Middle Cambrian have shown initial sealing capacity.These effective cap rocks are closely related to the distribution of Lower Palaeozoic hydrocarbons in the Tazhong Low Rise.With well-preserved Sangtamu Formation mudstone and its location close to migration pathways,rich Lower Paleozoic hydrocarbon accumulation can be found on the Northem Slope.Vertically,most of the reserves are distributed below the Sangtamu Formation mudstone; areally,hydrocarbons are mainly found in the areas with well-developed Sangtamu Formation mudstone and Lianglitag Formation marl.Burial history and hydrocarbon charging history show that the evolution of Lower Palaeozoic cap rocks controlled the accumulation of hydrocarbon in the Tazhong Low Rise.Take the Red Mudstone Member of the Tatairtag Formation and Sangtamu Formation mudstone for examples：1） In the hydrocarbon charging time of the Late Caledonian-Early Hercynian,with top surfaces at burial depths of over 1,100 m,the cap rocks were able to seal oil and gas; 2） During the intense uplifting of the Devonian,the cap rocks with top surfaces at burial depths of 200-800 m and 500-1,100 m respectively were denuded in local areas,thus hydrocarbons trapped in earlier time were degraded to widespread bitumen; 3） In the hydrocarbon charging time of the Late Hercynian and Himalayan,the top surfaces of the cap rocks were at burial depths of over 2,000 m without intense uplifting and denudation thereafter,so trapped hydrocarbons were preserved.Based on cap rocks,the Ordovician Penglaiba Formation and Lower Cambrian dolomite could be potential targets for exploration on the Tazhong Northern Slope,and combined with hydrocarbon migration,less risk would be involved.展开更多
Cap rocks with high thermal insulation are important for deep geothermal systems at a depth of 3000‒6000 m.Based on the deep geothermal geological conditions in the Fujian-Guangdong-Hainan area of South China,this stu...Cap rocks with high thermal insulation are important for deep geothermal systems at a depth of 3000‒6000 m.Based on the deep geothermal geological conditions in the Fujian-Guangdong-Hainan area of South China,this study established an ideal geological model of reservoir-cap rock assemblages and simulated the geothermal field distribution of cap rocks of different thicknesses and thermal conductivity.The simulation results show that the vertical geothermal temperature distribution in an uplifted area of a depression was present as inverted mirror reflections relative to the elevated area of the basement.Specifically,the isotherms above the elevated area are convex in shape,while those below the elevated area are concave.There is a temperature equilibrium line between the convex and concave isotherms.The heat flow moves from the depressed area to the uplifted area below the temperature equilibrium line and migrates in an opposite direction above the line.On this base,this study conducted the inversion of geothermal temperature fields in typical areas with thin,moderately thick,and thick cap rocks.The results indicate that,at the depth of 3000e6000 m,areas with thin cap rocks(igneous rock zone in the coastal area of Fujian)mainly host moderate-to low-temperature hydrothermal resources;areas with moderately thick cap rocks(Yuezhong Depression)have the geothermal temperature ranging between 100℃and 200℃and may develop moderate-to high-temperature hydrothermal resources and hot dry rocks(HDRs),with the former superimposing on the latter;and areas with thick cap rocks(onshore Beibuwan Basin)have a geothermal temperature of 120‒220℃,and contains mainly moderate-to high-temperature hydrothermal resources and HDRs.Therefore,it is recommended that the evaluation,exploitation,and utilization of deep geothermal resources be carried out according to the burial depth of the temperature equilibrium line and the specific demand for geothermal resources.展开更多
In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the op...In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the operation safety of gas storages,this paper takes Xinjiang H gas storage whose storage capacity and peak shaving capacity are the highest in China as the research object to establish a 3D fine geological model and a 3D dynamic geomechanical model in the regional scale of H gas storage based on the alternating change characteristics of geostress field during the high-speed cyclic injection and production of gas storage,combined with the geological,seismic,logging and various laboratory core experiment results.Then,the trap dynamic sealing capacity of H gas storage under the action of alternating stress after 14 years of depletion development of its original gas reservoir and long-term high-speed injection and production after its reconstruction from the gas reservoir was evaluated comprehensively.And the following research results were obtained.First,the change of the formation pressure in H gas storage has a significant effect on the regional geostress field.Second,after the development of the original H gas reservoir,the geostress on the two sides of the fault are greatly different,but the cap rock is not deformed and failed and the reservoir controlling fault as the gas bearing boundary doesn't glide,which ensures the safety of reconstructing H gas reservoir into gas storage.Third,due to the high-speed injection and production of H gas storage,the geostress field becomes more uneven,which has a potential negative impact on the integrity of the injection and production wells of the gas storage.Fourth,during the long-term high-speed injection and production operation of H gas reservoir,the cap rock does not undergo shear and tensile failure,but the numerical simulation of geomechanics shows that the long-term high-speed injection and production of the gas storage results in the relative sliding deformation(maximum about 5 cm)on both sides of H fault in the south of the reservoir,so the sealing capacity of H fault is a weak point impacting the integrity of the gas storage.Fifth,it is recommended to deploy monitoring wells at the upper block of H fault in the south of the gas storage to strengthen the injection and production dynamic monitoring.In conclusion,this study performs a qualitative and quantitative evaluation on the trap dynamic sealing capacity of gas storages rebuilt from gas reservoirs under the action of alternating stress,and it plays an important guiding role in ensuring the long-term injection and production safety of H gas storage.展开更多
Objective The Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation is one of the priority interval for shale gas exploration in the Sichuan Basin and its peripheral areas, and commercial shale gas has b...Objective The Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation is one of the priority interval for shale gas exploration in the Sichuan Basin and its peripheral areas, and commercial shale gas has been discovered from this interval in Jiaoshiba, Changning and Weiyuan shale gas fields in Sichuan Province. However, there is no significant discovery in other parts of the basin due to the different quality of black shale and the differences of tectonic evolution. Based on the progress of shale gas geological theory and exploration discoveries, as well as the theory of ＂source rock and cap rock controls on hydrocarbon accumulation＂, of the Upper Ordovician the main controlling factors Wufeng Formation-Lower Silurian Longmaxi Formation shale gas enrichment in the Sichuan Basin and its peripheral areas were analyzed, and the source rock and cap rock controls on the shale gas were also discussed. The results can provide new insights for the next shale gas exploration in this area.展开更多
A laser technique based scanning system was employed to make a comprehensive scanning through borehole forunmapped cavity under open pit bench,then the three-dimensional data will be obtained,and these data were used ...A laser technique based scanning system was employed to make a comprehensive scanning through borehole forunmapped cavity under open pit bench,then the three-dimensional data will be obtained,and these data were used for theoreticalanalysis and numerical simulation to analyze the stability of cap rock.Acoustic emission techniques were also adopted to carry outlong term real time rupture monitoring in cap rock.Therefore,a complete safety evaluation system for the cap rock was establishedto ensure safe operation of subsequent blasting processes.The ideal way of eliminating collapse hazard of such cavity is cap rockcaving through deep-hole blasting,thus,two deep-hole blasting schemes named as vertical deep-hole blasting scheme and one-timeraise driving integrated with deep-hole bench blasting scheme were proposed.The vertical deep-hole blasting scheme has moreexplosive consumption,but the relatively simple blasting net work structure can greatly reduce workloads.However,the one-timeraise driving integrated with deep-hole bench blasting scheme can obviously reduce explosive consumption,but the higher technicalrequirements on drilling,explosive charging and blasting network will increase workloads.展开更多
Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.Th...Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.The study shows that the Central African Rift System mainly develops high-quality lacustrine source rocks in the Lower Cretaceous,and the West African Rift System mainly develops high-quality terrigenous organic matter-rich marine source rocks in the Upper Cretaceous,and the two types of source rocks provide a material basis for the enrichment of oil and gas in the CWARS.Multiple sets of reservoir rocks including fractured basement and three sets of regional cap rocks in the Lower Cretaceous,the Upper Cretaceous,and the Paleogene are developed in the CWARS.Since the Late Mesozoic,due to the geodynamic factors including the dextral strike-slip movement of the Central African Shear Zone,the basins in different directions of the CWARS differ in terms of rifting stages,intervals of regional cap rocks,trap types and accumulation models.The NE-SW trending basins have mainly preserved one stage of rifting in the Early Cretaceous,with regional cap rocks developed in the Lower Cretaceous strata,forming traps of reverse anticlines,flower-shaped structures and basement buried hill,and two types of hydrocarbon accumulation models of"source and reservoir in the same formation,and accumulation inside source rocks"and"up-source and down-reservoir,and accumulation below source rocks".The NW–SE basins are characterized by multiple rifting stages superimposition,with the development of regional cap rocks in the Upper Cretaceous and Paleogene,forming traps of draping anticlines,faulted anticlines,antithetic fault blocks and the accumulation model of"down-source and up-reservoir,and accumulation above source rocks".The combination of reservoir and cap rocks inside source rocks of basins with multiple superimposed rifting stages,as well as the lithologic reservoirs and the shale oil inside source rocks of strong inversion basins are important fields for future exploration in basins of the CWARS.展开更多
It is of great significance to study the controlling effect of sealing systems on CBM enrichment in coalbed methane (CBM) exploration anddevelopment. In this paper, the relationships between CBM enrichment and geologi...It is of great significance to study the controlling effect of sealing systems on CBM enrichment in coalbed methane (CBM) exploration anddevelopment. In this paper, the relationships between CBM enrichment and geological elements were analyzed. The geological elements includesealing layers (e.g. regional cap rock, regional floor, and immediate roof and floor), later structural adjustment and strata production status. It isshown that CBM tends to enrich in the areas where regional mudstone cap rocks and floors are distributed stably, structures are uplifted andinversed slightly after the hydrocarbon accumulation period and the strata is gentle in a balanced state. Then, the concept of sealing system wasput forward based on the worldwide CBM exploration and development practices over the years. A sealing system refers to a geological unitcomposed of a lateral stable zone and cap rock which prevents gas from migrating upward and downward. In a sealing system, CBM can getenriched and coal-measure gas can also be accumulated. Finally, three gas reservoir types (i.e., sandwich-type CBM reservoir, associated CBM-sandstone gas reservoir and coal-derived sandstone gas reservoir) were identified based on the configuration relationships between elements ofthe CBM (or coal-measure gas) sealing system. It is recommended to change the exploration ideas from simple CBM exploration to 3D CBMand coal-measure gas exploration. In addition, an evaluation index system of CBM (or coal-measure gas) geological selection was established. Itis pointed out that good application effects may be realized if the stereoscopic CBM and coal-measure gas exploration is applied in the JunggarBasin and the eastern margin of the Ordos Basin.展开更多
To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.sourc...To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.source rock,reservoir and play)and the distribution laws of the deep-seated old giant marine carbonate oil/gasfields in China's Craton Basins were investigated systematically.Then,the accumulation and enrichment conditions of deep Sinian natural gas in the Sichuan Basin were analyzed.Finally,potential and favorable target zones of natural gas exploration in the Dengying Formation of Upper Sinian were evaluated.And the following research results were obtained.Firstly,the effec-tiveness and scale of source kitchens,reservoirs and reservoirecaprock assemblages and the proximity are the necessary conditions for the formation of deep-seated giant carbonate oil/gasfields,and paleo-uplifts,paleo-slopes and paleo-fault zones are the favorable areas of searching deep-seated giant carbonate oil/gasfields.Secondly,in the Sichuan Basin,three sets of high-quality source rocks are developed in the NeoproterozoiceCambrian System,and their maturity of organic matter is still in the optimal window for cracking gas,so the gas generation scale is large.Thirdly,after the microbial carbonate rocks of Dengying Formation in the Sichuan Basin were reconstructed by constructive diagenesis,effective reservoirs are formed and distributed widely.Fourthly,owing to the integrated source rocks and cap rocks of Dengying Formation,the marginal platform and the intra platform have favorable conditions for proximal hydrocarbon accumulation.In conclusion,the deep Sinian in the Sichuan Basin has good conditions of hydrocarbon accumulation and it is an important replacement area of natural gas exploration.Paleo-uplifts and slopes in the central Sichuan Basin have been the favorable locations of natural gas accumulation for a long period.Large-scale exploration shall focus on four favorable areas,including the marginal platform zone in the fourth member of Dengying Formation,the marginal platform zone in the second member of Dengying Formation,the bioherm shoalbody of Dengying Formation intra platform in the paleo-uplifts and slopes of the central Sichuan Basin,and the bioherm shoalbody of Dengying Formation in the eastern Sichuan Basin.展开更多
This paper elucidates the relationship between landslides, geologic structures, and hydrothermal alteration zones based primarily on X-ray powder diffraction and uniaxial compressive strength tests on weakly weathered...This paper elucidates the relationship between landslides, geologic structures, and hydrothermal alteration zones based primarily on X-ray powder diffraction and uniaxial compressive strength tests on weakly weathered and hydrothermally altered rocks from the Ohekisawa-Shikerebembetsugawa landslide area in Teshikaga Town, Hokkaido, Japan. The OHS （Ohekisawa slide） occurred on a dip slope of sedimentary rocks from the Upper Miocene Shikerepe Formation within a homocline, and also on weathered and hydrothermally altered rocks within the boundary area between the hydrothermal smectite zone and smectite-bearing mordenite zone. The SHS （Shikerebembetsugawa slide） occurred on a dip slope of sedimentary rocks from the Upper Miocene Hanakushibe Formation within wavy folds and was also controlled by a cap rock of Teshikaga Volcano Somma Lava. The SHS occurred also on weathered and hydrothermally altered rocks within the boundary area between the hydrothermal smectite zone and smectite-bearing laumontite zone. The mechanical properties of smectite, smectite-bearing mordenite, and smectite-bearing laumontite zone weakly weathered rocks indicate that they are very weak, soft rocks. These landslides are regarded as HAZLs （hydrothermal alteration zone landslides）. The hydrothermal alteration yielding smectite is thus closely related to these two ancient landslides, suggesting that the potential for HAZLs within a hydrothermal area can be assessed based on the swelling clay mineral-beating hydrothermal alteration types, dip slope, and cap rock.展开更多
Thermal evolution of source rocks and dynamic sealing evolution of cap rocks are both subjected to tectonic evolution.The marine sequences in South China have experienced superposed structural deformation from multipl...Thermal evolution of source rocks and dynamic sealing evolution of cap rocks are both subjected to tectonic evolution.The marine sequences in South China have experienced superposed structural deformation from multiple tectonic events.To investigate the effectiveness of preservation conditions,it is of great importance to understand the controls of key tectonic events on the dynamic evolution of cap rocks.This paper discusses the controls of Late Jurassic-Early Cretaceous(J3-K1) tectonic event on source and cap rocks in marine sequences in South China based on the relationships between J3-K1 tectonic event and the burial history types of the marine sequences,the hydrocarbon generation processes of marine source rocks,the sealing evolution of cap rocks,the preservation of hydrocarbon accumulations,and the destruction of paleo-oil pools.The study has the following findings.In the continuously subsiding and deeply buried areas during the J3-K1 period,marine source rocks had been generating hydrocarbons for over a long period of time and hydrocarbon generation ended relatively late.At the same time,the sealing capacity of the overburden cap rocks had been constantly strengthened so that hydrocarbons could be preserved.In the areas which suffered compressional deformation,folding and thrusting,uplifting and denudation in J3-K1,the burial history was characterized by an early uplifting and the hydrocarbon generation by marine source rocks ended(or suspended) during the J3-K1 period.The sealing capacity of the cap rocks was weakened or even vanished.Thus the conditions for preserving the hydrocarbon accumulations were destroyed.The continuously subsiding and deeply buried areas during the J3-K1 period are the strategic precincts of the petroleum exploration in marine sequences in South China.展开更多
文摘The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in pore structure,permeability,and mechanical strength of cap rocks under cyclic loads may impact the rock sealing integrity during the injection and recovery phases of UGS.In this work,the mechanical deformation and failure tests of rocks,as well as rock damage tests under alternating loads,are conducted to analyze the changes in the strength and permeability of rocks under multiple-cycle intense injection and recovery of UGS.Additionally,this study proposes an evaluation method for the dynamic sealing performance of UGS cap rocks under multi-cycle alternating loads.The findings suggest that the failure strength(70%)can be used as the critical value for rock failure,thus providing theoretical support for determining the upper limit of operating pressure and the number of injection-recovery cycles for the safe operation of a UGS system.
基金supported by the National Natural Science Foundation of China(No.41072102)National Key Basic Research Development Plan("973"Project,No.2005CB422108)National Major Projects(Nos.2008ZX05004-004,2011ZX05005-001)
文摘Despite the absence of regional cap rocks in the Lower Paleozoic for the entire Tazhong Low Rise,several sets of effective local cap rocks are well preserved on the Northern Slope.Of these the best is the Ordovician mudstone of the Sangtamu Formation; the second is the Silurian Red Mudstone Member of the Tatairtag Formation and the marl of the Ordovician Lianglitag Formation; and the third is the gray mudstone of the Silurian Kepingtag Formation.The dense limestone of the Ordovician Yingshan Formation and the gypsum of the Middle Cambrian have shown initial sealing capacity.These effective cap rocks are closely related to the distribution of Lower Palaeozoic hydrocarbons in the Tazhong Low Rise.With well-preserved Sangtamu Formation mudstone and its location close to migration pathways,rich Lower Paleozoic hydrocarbon accumulation can be found on the Northem Slope.Vertically,most of the reserves are distributed below the Sangtamu Formation mudstone; areally,hydrocarbons are mainly found in the areas with well-developed Sangtamu Formation mudstone and Lianglitag Formation marl.Burial history and hydrocarbon charging history show that the evolution of Lower Palaeozoic cap rocks controlled the accumulation of hydrocarbon in the Tazhong Low Rise.Take the Red Mudstone Member of the Tatairtag Formation and Sangtamu Formation mudstone for examples：1） In the hydrocarbon charging time of the Late Caledonian-Early Hercynian,with top surfaces at burial depths of over 1,100 m,the cap rocks were able to seal oil and gas; 2） During the intense uplifting of the Devonian,the cap rocks with top surfaces at burial depths of 200-800 m and 500-1,100 m respectively were denuded in local areas,thus hydrocarbons trapped in earlier time were degraded to widespread bitumen; 3） In the hydrocarbon charging time of the Late Hercynian and Himalayan,the top surfaces of the cap rocks were at burial depths of over 2,000 m without intense uplifting and denudation thereafter,so trapped hydrocarbons were preserved.Based on cap rocks,the Ordovician Penglaiba Formation and Lower Cambrian dolomite could be potential targets for exploration on the Tazhong Northern Slope,and combined with hydrocarbon migration,less risk would be involved.
基金This work was funded by several scientific research programs including Evaluation and Optimal Target Selection of Deep Geothermal Resources in the Igneous Region of South China(No.:2019YFC0604903)Analysis and Geothermal Reservoir Stimulation Methods of Deep High-temperature Geothermal Systems in East China(No.:2021YFA0716004)+1 种基金the National Key Research and Development Program of China,Deep Geological Processes and Resource Effects of Basins(No.:U20B6001)the Joint Fund Program of the National Natural Science Foundation of China and Sinopec,and Siting and Target Evaluation of Deep Geothermal Resources in Key Areas of Southeastern China(No.:P20041-1)of the Sinopec Science and Technology Research Program.
文摘Cap rocks with high thermal insulation are important for deep geothermal systems at a depth of 3000‒6000 m.Based on the deep geothermal geological conditions in the Fujian-Guangdong-Hainan area of South China,this study established an ideal geological model of reservoir-cap rock assemblages and simulated the geothermal field distribution of cap rocks of different thicknesses and thermal conductivity.The simulation results show that the vertical geothermal temperature distribution in an uplifted area of a depression was present as inverted mirror reflections relative to the elevated area of the basement.Specifically,the isotherms above the elevated area are convex in shape,while those below the elevated area are concave.There is a temperature equilibrium line between the convex and concave isotherms.The heat flow moves from the depressed area to the uplifted area below the temperature equilibrium line and migrates in an opposite direction above the line.On this base,this study conducted the inversion of geothermal temperature fields in typical areas with thin,moderately thick,and thick cap rocks.The results indicate that,at the depth of 3000e6000 m,areas with thin cap rocks(igneous rock zone in the coastal area of Fujian)mainly host moderate-to low-temperature hydrothermal resources;areas with moderately thick cap rocks(Yuezhong Depression)have the geothermal temperature ranging between 100℃and 200℃and may develop moderate-to high-temperature hydrothermal resources and hot dry rocks(HDRs),with the former superimposing on the latter;and areas with thick cap rocks(onshore Beibuwan Basin)have a geothermal temperature of 120‒220℃,and contains mainly moderate-to high-temperature hydrothermal resources and HDRs.Therefore,it is recommended that the evaluation,exploitation,and utilization of deep geothermal resources be carried out according to the burial depth of the temperature equilibrium line and the specific demand for geothermal resources.
基金Project supported by PetroChina’s Major Science and Technology Project“Study and Application of the Key Technologies of UGS Geology and Reservoir Engineering”(No.2015E-4002).
文摘In order to provide effective guidance for optimizing and adjusting the maximum operation pressure and dynamic monitoring well pattern of underground gas storages(hereinafter referred as gas storages)and ensure the operation safety of gas storages,this paper takes Xinjiang H gas storage whose storage capacity and peak shaving capacity are the highest in China as the research object to establish a 3D fine geological model and a 3D dynamic geomechanical model in the regional scale of H gas storage based on the alternating change characteristics of geostress field during the high-speed cyclic injection and production of gas storage,combined with the geological,seismic,logging and various laboratory core experiment results.Then,the trap dynamic sealing capacity of H gas storage under the action of alternating stress after 14 years of depletion development of its original gas reservoir and long-term high-speed injection and production after its reconstruction from the gas reservoir was evaluated comprehensively.And the following research results were obtained.First,the change of the formation pressure in H gas storage has a significant effect on the regional geostress field.Second,after the development of the original H gas reservoir,the geostress on the two sides of the fault are greatly different,but the cap rock is not deformed and failed and the reservoir controlling fault as the gas bearing boundary doesn't glide,which ensures the safety of reconstructing H gas reservoir into gas storage.Third,due to the high-speed injection and production of H gas storage,the geostress field becomes more uneven,which has a potential negative impact on the integrity of the injection and production wells of the gas storage.Fourth,during the long-term high-speed injection and production operation of H gas reservoir,the cap rock does not undergo shear and tensile failure,but the numerical simulation of geomechanics shows that the long-term high-speed injection and production of the gas storage results in the relative sliding deformation(maximum about 5 cm)on both sides of H fault in the south of the reservoir,so the sealing capacity of H fault is a weak point impacting the integrity of the gas storage.Fifth,it is recommended to deploy monitoring wells at the upper block of H fault in the south of the gas storage to strengthen the injection and production dynamic monitoring.In conclusion,this study performs a qualitative and quantitative evaluation on the trap dynamic sealing capacity of gas storages rebuilt from gas reservoirs under the action of alternating stress,and it plays an important guiding role in ensuring the long-term injection and production safety of H gas storage.
基金supported by the National Natural Science Foundation of China(grant No.41202103)
文摘Objective The Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation is one of the priority interval for shale gas exploration in the Sichuan Basin and its peripheral areas, and commercial shale gas has been discovered from this interval in Jiaoshiba, Changning and Weiyuan shale gas fields in Sichuan Province. However, there is no significant discovery in other parts of the basin due to the different quality of black shale and the differences of tectonic evolution. Based on the progress of shale gas geological theory and exploration discoveries, as well as the theory of ＂source rock and cap rock controls on hydrocarbon accumulation＂, of the Upper Ordovician the main controlling factors Wufeng Formation-Lower Silurian Longmaxi Formation shale gas enrichment in the Sichuan Basin and its peripheral areas were analyzed, and the source rock and cap rock controls on the shale gas were also discussed. The results can provide new insights for the next shale gas exploration in this area.
基金Projects(51204206,41272304,41372278) supported by the National Natural Science Foundation of China
文摘A laser technique based scanning system was employed to make a comprehensive scanning through borehole forunmapped cavity under open pit bench,then the three-dimensional data will be obtained,and these data were used for theoreticalanalysis and numerical simulation to analyze the stability of cap rock.Acoustic emission techniques were also adopted to carry outlong term real time rupture monitoring in cap rock.Therefore,a complete safety evaluation system for the cap rock was establishedto ensure safe operation of subsequent blasting processes.The ideal way of eliminating collapse hazard of such cavity is cap rockcaving through deep-hole blasting,thus,two deep-hole blasting schemes named as vertical deep-hole blasting scheme and one-timeraise driving integrated with deep-hole bench blasting scheme were proposed.The vertical deep-hole blasting scheme has moreexplosive consumption,but the relatively simple blasting net work structure can greatly reduce workloads.However,the one-timeraise driving integrated with deep-hole bench blasting scheme can obviously reduce explosive consumption,but the higher technicalrequirements on drilling,explosive charging and blasting network will increase workloads.
基金Supported by the National Natural Science Foundation Project(92255302)National Science and Technology Major Project(2016ZX05029005)Scientific Research and Technological Development Project of PetroChina(2021DJ31).
文摘Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.The study shows that the Central African Rift System mainly develops high-quality lacustrine source rocks in the Lower Cretaceous,and the West African Rift System mainly develops high-quality terrigenous organic matter-rich marine source rocks in the Upper Cretaceous,and the two types of source rocks provide a material basis for the enrichment of oil and gas in the CWARS.Multiple sets of reservoir rocks including fractured basement and three sets of regional cap rocks in the Lower Cretaceous,the Upper Cretaceous,and the Paleogene are developed in the CWARS.Since the Late Mesozoic,due to the geodynamic factors including the dextral strike-slip movement of the Central African Shear Zone,the basins in different directions of the CWARS differ in terms of rifting stages,intervals of regional cap rocks,trap types and accumulation models.The NE-SW trending basins have mainly preserved one stage of rifting in the Early Cretaceous,with regional cap rocks developed in the Lower Cretaceous strata,forming traps of reverse anticlines,flower-shaped structures and basement buried hill,and two types of hydrocarbon accumulation models of"source and reservoir in the same formation,and accumulation inside source rocks"and"up-source and down-reservoir,and accumulation below source rocks".The NW–SE basins are characterized by multiple rifting stages superimposition,with the development of regional cap rocks in the Upper Cretaceous and Paleogene,forming traps of draping anticlines,faulted anticlines,antithetic fault blocks and the accumulation model of"down-source and up-reservoir,and accumulation above source rocks".The combination of reservoir and cap rocks inside source rocks of basins with multiple superimposed rifting stages,as well as the lithologic reservoirs and the shale oil inside source rocks of strong inversion basins are important fields for future exploration in basins of the CWARS.
文摘It is of great significance to study the controlling effect of sealing systems on CBM enrichment in coalbed methane (CBM) exploration anddevelopment. In this paper, the relationships between CBM enrichment and geological elements were analyzed. The geological elements includesealing layers (e.g. regional cap rock, regional floor, and immediate roof and floor), later structural adjustment and strata production status. It isshown that CBM tends to enrich in the areas where regional mudstone cap rocks and floors are distributed stably, structures are uplifted andinversed slightly after the hydrocarbon accumulation period and the strata is gentle in a balanced state. Then, the concept of sealing system wasput forward based on the worldwide CBM exploration and development practices over the years. A sealing system refers to a geological unitcomposed of a lateral stable zone and cap rock which prevents gas from migrating upward and downward. In a sealing system, CBM can getenriched and coal-measure gas can also be accumulated. Finally, three gas reservoir types (i.e., sandwich-type CBM reservoir, associated CBM-sandstone gas reservoir and coal-derived sandstone gas reservoir) were identified based on the configuration relationships between elements ofthe CBM (or coal-measure gas) sealing system. It is recommended to change the exploration ideas from simple CBM exploration to 3D CBMand coal-measure gas exploration. In addition, an evaluation index system of CBM (or coal-measure gas) geological selection was established. Itis pointed out that good application effects may be realized if the stereoscopic CBM and coal-measure gas exploration is applied in the JunggarBasin and the eastern margin of the Ordos Basin.
基金supported by the National Major Science and Technology Project"Hydrocarbon accumulation,key techniques and target evaluation of carbon-ate rocks in Lower Paleozoic-Pre-Cambrian"(No.2016ZX05004).
文摘To construct a giant Sichuan gas province,it is in an urgent need of exploring new replacement areas with abundant natural gas resources and great exploration potential.In this paper,the formation conditions(e.g.source rock,reservoir and play)and the distribution laws of the deep-seated old giant marine carbonate oil/gasfields in China's Craton Basins were investigated systematically.Then,the accumulation and enrichment conditions of deep Sinian natural gas in the Sichuan Basin were analyzed.Finally,potential and favorable target zones of natural gas exploration in the Dengying Formation of Upper Sinian were evaluated.And the following research results were obtained.Firstly,the effec-tiveness and scale of source kitchens,reservoirs and reservoirecaprock assemblages and the proximity are the necessary conditions for the formation of deep-seated giant carbonate oil/gasfields,and paleo-uplifts,paleo-slopes and paleo-fault zones are the favorable areas of searching deep-seated giant carbonate oil/gasfields.Secondly,in the Sichuan Basin,three sets of high-quality source rocks are developed in the NeoproterozoiceCambrian System,and their maturity of organic matter is still in the optimal window for cracking gas,so the gas generation scale is large.Thirdly,after the microbial carbonate rocks of Dengying Formation in the Sichuan Basin were reconstructed by constructive diagenesis,effective reservoirs are formed and distributed widely.Fourthly,owing to the integrated source rocks and cap rocks of Dengying Formation,the marginal platform and the intra platform have favorable conditions for proximal hydrocarbon accumulation.In conclusion,the deep Sinian in the Sichuan Basin has good conditions of hydrocarbon accumulation and it is an important replacement area of natural gas exploration.Paleo-uplifts and slopes in the central Sichuan Basin have been the favorable locations of natural gas accumulation for a long period.Large-scale exploration shall focus on four favorable areas,including the marginal platform zone in the fourth member of Dengying Formation,the marginal platform zone in the second member of Dengying Formation,the bioherm shoalbody of Dengying Formation intra platform in the paleo-uplifts and slopes of the central Sichuan Basin,and the bioherm shoalbody of Dengying Formation in the eastern Sichuan Basin.
文摘This paper elucidates the relationship between landslides, geologic structures, and hydrothermal alteration zones based primarily on X-ray powder diffraction and uniaxial compressive strength tests on weakly weathered and hydrothermally altered rocks from the Ohekisawa-Shikerebembetsugawa landslide area in Teshikaga Town, Hokkaido, Japan. The OHS （Ohekisawa slide） occurred on a dip slope of sedimentary rocks from the Upper Miocene Shikerepe Formation within a homocline, and also on weathered and hydrothermally altered rocks within the boundary area between the hydrothermal smectite zone and smectite-bearing mordenite zone. The SHS （Shikerebembetsugawa slide） occurred on a dip slope of sedimentary rocks from the Upper Miocene Hanakushibe Formation within wavy folds and was also controlled by a cap rock of Teshikaga Volcano Somma Lava. The SHS occurred also on weathered and hydrothermally altered rocks within the boundary area between the hydrothermal smectite zone and smectite-bearing laumontite zone. The mechanical properties of smectite, smectite-bearing mordenite, and smectite-bearing laumontite zone weakly weathered rocks indicate that they are very weak, soft rocks. These landslides are regarded as HAZLs （hydrothermal alteration zone landslides）. The hydrothermal alteration yielding smectite is thus closely related to these two ancient landslides, suggesting that the potential for HAZLs within a hydrothermal area can be assessed based on the swelling clay mineral-beating hydrothermal alteration types, dip slope, and cap rock.
基金supported by NationalNatural Science Foundation of China (Grant No. 40974048)National Basic Research Program of China (Grant No. 2005CB422108)National Science & Technology Special Project (Grant No. 2008ZX05005)
文摘Thermal evolution of source rocks and dynamic sealing evolution of cap rocks are both subjected to tectonic evolution.The marine sequences in South China have experienced superposed structural deformation from multiple tectonic events.To investigate the effectiveness of preservation conditions,it is of great importance to understand the controls of key tectonic events on the dynamic evolution of cap rocks.This paper discusses the controls of Late Jurassic-Early Cretaceous(J3-K1) tectonic event on source and cap rocks in marine sequences in South China based on the relationships between J3-K1 tectonic event and the burial history types of the marine sequences,the hydrocarbon generation processes of marine source rocks,the sealing evolution of cap rocks,the preservation of hydrocarbon accumulations,and the destruction of paleo-oil pools.The study has the following findings.In the continuously subsiding and deeply buried areas during the J3-K1 period,marine source rocks had been generating hydrocarbons for over a long period of time and hydrocarbon generation ended relatively late.At the same time,the sealing capacity of the overburden cap rocks had been constantly strengthened so that hydrocarbons could be preserved.In the areas which suffered compressional deformation,folding and thrusting,uplifting and denudation in J3-K1,the burial history was characterized by an early uplifting and the hydrocarbon generation by marine source rocks ended(or suspended) during the J3-K1 period.The sealing capacity of the cap rocks was weakened or even vanished.Thus the conditions for preserving the hydrocarbon accumulations were destroyed.The continuously subsiding and deeply buried areas during the J3-K1 period are the strategic precincts of the petroleum exploration in marine sequences in South China.
