In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are...In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are not clear,which hinders the progress in natural gas exploration.In view of the sedimentary background of the Sichuan Basin,field outcrop section,drilling data and seismic data were comprehensively analyzed with the favorable reservoir intervals in the framework of sequence stratigraphy as the key research units.Research results about its lithofacies paleogeography were obtained as follows.First,a gentle slope SW high and NE low was presented during the sedimentation of the Qixia Fm in the Middle Permian.In the Maokou Fm of the Middle Permian,however,a series of the N-W trending intra-platform rifts were developed in this setting,and eventually a paleogeographic pattern of NE-dipping alternative uplift and depression was evolved.Second,in the Qixia Fm,the transgressive tract was in an open platform environment and the highstand system tract evolved into a rimmed platform.And the platform margin beach in the area of Jiange-Ya'an is the favorable reservoir facies belt.And third,in the Maokou Fm,the transgressive tract was in the carbonate shelf environment and the highstand system tract evolved into a rimmed platform.And the platform margin reef flat in the area of Jiange-Ya'an and the syneclise margin beach in the area of YantingeGuang'an are favorable reservoir facies belts.It is concluded that the two grain beach facies belts in the areas of Jiange-Ya'an and YantingeGuang'an were the favorable zones for the large-scale development of Middle Permian layered dolomite reservoirs and they are the main target of subsequent natural gas exploration.展开更多
Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope...Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope of Leshan-Longnüsi paleouplift in the Sichuan Basin,to reveal the genetic relationship between stratigraphic filling,paleogeomorphology and large-scale grain shoal.(1)The Xixiangchi Formation in the study area is overlapped and filled gradually to the Leshan-Longnüsi paleouplift,but gets thin sharply due to truncation only near the denudation pinch-out line of the paleouplift.Two overlap slope break belts and one erosion slope break belt are identified,and the Xixiangchi Formation is divided into 4 members from bottom to top.(2)The filling pattern of the overlapping at the base and erosion at the top indicates that the thickness of Xixiangchi Formation can reflect the pre-depositional paleogeomorphology,and reveals that the studied area has a monoclinal geomorphic feature of plunging to southeast and being controlled by multistage slope break belts.(3)The large-scale grain shoals and shoal controlled reservoirs are developed longitudinally in the third and fourth members of the Xixiangchi Formation,and laterally in the vicinity of the multistage overlap slope break belts.(4)Overlap slope break belts are closely related to northwest trending reverse faults.The western margin of the South China Plate converging with the Qiangtang-Himalaya massif in the middle-late Cambrian resulted in the rapid uplift of the northwestern margin of the Yangtze Plate and expanding toward southeast,leaving gradually plunging multistage slope breaks and large-scale northeast grain shoal reservoir belts.Considering oil and gas test results,it is predicted that the favorable exploration zone of the grain shoal controlled reservoirs covers an area of 3340 km^(2).展开更多
The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore...The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.展开更多
Based on the research progress of the geological theory of coal-formed gas,the contributions of coal-formed gas to the natural gas reserves and production in China and to the development of natural gas in major gas-pr...Based on the research progress of the geological theory of coal-formed gas,the contributions of coal-formed gas to the natural gas reserves and production in China and to the development of natural gas in major gas-producing basins are analyzed,and the key favorable exploration zones for coal-formed gas in China are comprehensively evaluated.The following results are obtained.First,coal measures are good gas source rocks,and hydrocarbon generation from coal measure was dominated by gas,followed by oil.Second,a natural gas genetic identification index system based on stable isotopes,light hydrocarbon components,and biomarkers is established.Third,the quantitative and semi-quantitative factors controlling the formation of large gas fields,represented by the indicator of gas generation intensity greater than 20×10^(8) m^(3)/km^(2),are identified to guide the discovery of large gas fields in China.Fourth,coal-formed gas is the major contributor to the current natural gas reserves and production of China,both accounting for over 55%.The high proportion of coal-formed gas has enabled the Tarim,Sichuan and Ordos basins to be the major gas production areas in China.Fifth,coal rock gas is an important field for future exploration of coal-formed gas,and key zones include the Carboniferous Benxi Formation(Fm.)in the Wushenqi-Mizhi area of the Ordos Basin,the Permian Longtan Fm.in central-southern Sichuan Basin,the Jurassic Xishanyao Fm.in the southern margin and Luliang uplift of the Junggar Basin.Sixth,tight gas is the main area for increasing reserves and production,and the favorable exploration zones include the Carboniferous-Permian in southern Ordos Basin and the Bohai Bay Basin,and the Triassic Xujiahe Fm.in the transition zone between central and western Sichuan Basin.Seventh,the Jurassic in the southern margin of the Junggar Basin is a key favorable exploration zone for subsequent investigation of conventional coal-formed gas.These insights have valuable theoretical and practical significance for further developing and improving the theory of coal-formed gas,and guiding the exploration of coal-formed gas fields in China.展开更多
In order to clarify the hydrocarbon accumulation significance and exploration prospect of the unconformity caused by the Huaiyuan movement in the Ordos Basin,this paper studies the spatial distribution and structural ...In order to clarify the hydrocarbon accumulation significance and exploration prospect of the unconformity caused by the Huaiyuan movement in the Ordos Basin,this paper studies the spatial distribution and structural plane characteristics of this unconformity and its relationships with hydrocarbon accumulation by observing field outcrops and cores and analyzing logging data,based on the previous research results and the interpretation results of 2D and new 3D seismic data.And the following research results are obtained.First,the unconformity was mainly formed in the Floian Age of Early Ordovician and widely occurs at the bottom of the Jiawang Formation and the top of the Sanshanzi Formation and the related tectonism lasts 30 Myr.Second,basal conglomerate and sandstone less than 1 m in thickness are developed above the unconformity at the edge of the basin,while thin mudstone,argillaceous dolomite(limestone)and marl are developed above the unconformity in the central part of the basin.Third,the unconformity structurally consists of three layers,including a basal conglomerate layer,a paleosoil layer and a fullyesemi weathered carbonate layer from top to bottom,among which,the last one is 20-90 m in thickness with developed dissolution fractures and pores to form a quality reservoir.Fourth,the unconformity results in the development of a series of large valleys landforms,which incise the Lower OrdovicianeUpper Cambrian.Fifth,the unconformity can act as a good channel for hydrocarbon migration,and it connects with the unconformity caused by the Caledonian movement within the paleo-uplift of the Ordos Basin,which is favorable for the the hydrocarbon of different sources in the west side of the basin eastwards to migrate,accumulate and form a gas reservoir.In conclusion,the deep Lower Paleozoic related to the Huaiyuan unconformity is expected to be an important natural gas exploration field in the Ordos Basin.展开更多
Progress of natural gas exploration has recently been made in the Upper Paleozoic marine-facies reservoirs in the NW Sichuan Basin.It has been proved that the Middle Permian Qixia Fm pore-type dolomite reservoirs may ...Progress of natural gas exploration has recently been made in the Upper Paleozoic marine-facies reservoirs in the NW Sichuan Basin.It has been proved that the Middle Permian Qixia Fm pore-type dolomite reservoirs may be distributed continuously in a large area,besides,for thefirst time favorable gas-bearing Devonian dolomite reservoirs in great thickness were discovered in the downhole there.Recent research achievements indicate that:(1)The Lower Cambrian quality source rocks in huge thickness were found in the study sedimentary area with advantageous hydrocarbon source conditions.(2)Influenced by the Caledonian movement,the whole NW Sichuan Basin was lifted up to form a massive box-like NS-trending plunging uplift low steep in the west but high sluggish in the east,laying a robust foundation for the inheritance of Devonian,Carboniferous,and Permian platform margin reef large-scale sedimentation and dolomitization.(3)In the Upper Paleozoic strata,there were multiple planes of unconformity and multi-stage supergene karst occurred,improving the preservation and seeping capacity of reservoirs.(4)Tectonic deformations resulted from the nappe structure in the Longmenshan Mountain provided good hydrocarbon source fractures and sealing conditions for oil and gas reservoirs,which is conductive to the formation of a giant gas pool.It is concluded that the back-thrust anticline belt east to Hidden fault I in this study area has favorable conditions for large-scale structuralestratigraphic and structur-alelithologic combination traps.As suggested in this study,relatively strong dolomitization was found in the Qixia Fm in the Shejianhe RivereZhongba higher palaeogeomorphic deposit area,so the most favorable exploration target of the Qixia Fm will be around the central axis of Caledonian paleo-uplift to the east ridgeline,and the most favorable prospect of the Upper Palaeozoic will be the central axis to the west of Hidden fault I where three gas bearing reservoirs will be possibly explored at the same time.展开更多
Since 2014,great gas discoveries have been achieved in the Upper Paleozoic Shuangyushi zone in the piedmont zone of the Longmenshan mountains,northwestern Sichuan Basin,where multiple gas wells with industrial flows h...Since 2014,great gas discoveries have been achieved in the Upper Paleozoic Shuangyushi zone in the piedmont zone of the Longmenshan mountains,northwestern Sichuan Basin,where multiple gas wells with industrial flows have been drilled and completed successively in the Middle Permian Qixia Fm and Middle Devonian Guanwushan Fm,etc.Along with the steady progress of exploration there,to make a further in-depth study on the characteristics of the frontal–piedmont zones in the Longmenshan thrust–nappe structures will be of great significance to both a better understanding of Upper Paleozoic gas reservoirs in this study area and the expansion of oil and gas exploration field.In view of this,based on the newly deployed 3D seismic surveys,gravity–magnetic–electronic data,and practical drilling information from exploration wells like Well ST 9,the characteristics of the frontal–piedmont zones in the Longmenshan thrust–nappe structures are analyzed as well as the features of the buried structures,gas reservoir forming conditions and exploration prospect there.The following findings were obtained:(1)A huge buried structure belt is developed underlying the Longmenshan front fault belt No.1(LSFFB 1)and marine strata are thus formed below the Lower Triassic Jialingjiang Fm due to the roles of compressive folding,extrusion and deformation;(2)The detachment horizons from LSFFB 1 go from shallower in the south to deeper in the north,turning from Cambrian slipping in the south to basement-involved in the north.The Paleozoic and its overlying strata were overall uplifted with a higher degree northward and so did the strata between the up-thrown and down-thrown sides of the faults with a greater displacement distance and higher folding degree,resulting in that the Paleozoic strata in the north are 1500 higher uplifted than those in the south;(3)In the western Jiange and Guangyuan areas,the eastern LSFFB 1 presents a tectonic pattern of“three steps”as a whole.In conclusion,there are good gas reservoir forming conditions in LSFFB 1,the down-thrown sides of which cover an area of 1800 km2,where the Guanwushan Fm and Qixia Fm provide good accumulation and preservation conditions for gas reservoirs,which will become favorable gas exploration targets in the deep marine strata in NW Sichuan Basin.展开更多
The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the ...The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.展开更多
Based on comprehensive analysis of cores,thin sections,logging and seismic data,the sequence stratigraphy and sedimentary evolution of the third and fourth members of Sinian Dengying Formation(Deng 3 and Deng 4 member...Based on comprehensive analysis of cores,thin sections,logging and seismic data,the sequence stratigraphy and sedimentary evolution of the third and fourth members of Sinian Dengying Formation(Deng 3 and Deng 4 members for short)in the Gaomo area of Sichuan Basin were investigated,and the favorable zones for reservoir development in the Deng 3 Member and Deng 4 Member were predicted.(1)Two Type I and one Type II sequence boundaries are identified in the Deng 3 and Deng 4 members.Based on the identified sequence boundaries,the Deng 3 and Deng 4 members can be divided into two third order sequences SQ3 and SQ4,which are well-developed,isochronal and traceable in this area;the SQ3 thins from west to the east,and the SQ4 thins from northwest to southeast.(2)The sedimentary environment from the depositional period of SQ3 to SQ4 has experienced the evolution from mixed platform to rimmed platform,and the platform rimmed system on the west side is characterized by the development of platform margin microbial mound and grain shoal assemblages.The intraplatform area is a restricted platform facies composed of a variety of dolomites,and there are local micro-geomorphic highlands of different scales and scattered intraplatform mounds and shoals.(3)The Deng 4 Member reservoirs,with obvious facies-controlled characteristic,are mainly distributed in the upper part of high-frequency upward shallow cycle and the high-stand systems tract of the third-order sequence vertically,and are more developed in the platform margin belt than in the intraplatform belt,and more developed in the Gaoshiti platform margin belt than in the west Suining platform margin belt on the plane.(4)Three types of favorable reservoir zones of Deng 4 Member have been finely delineated with 3D seismic data;among them,the mound and shoal facies zones developed in the ancient highlands of the intraplatform are the first choice for the next exploration and development of the Deng 4 Member.展开更多
Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the...Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the most potential gas exploration target in the deep strata of this basin.Apart from the above-mentioned one,the other huge paleo-uplifts are all considered to be the ones formed in the post-Caledonian period,the impact of which,however,has rarely ever been discussed on the SinianeLower Paleozoic oil and gas reservoir formation.In view of this,based on outcrops,drilling and geophysical data,we analyzed the SinianeLower Paleozoic tectonic setting and sedimentary background in the East Sichuan Basin,studied the distribution rules of reservoirs and source rocks under the control of paleo-uplifts,andfinally discussed,on the basis of structural evolution analysis,the conditions for the formation of SinianeLower Paleozoic gas reservoirs in this study area.The followingfindings were achieved.(1)The DazhoueKaijiang inherited uplift in NE Sichuan Basin which was developed before the Middle Cambrian controlled a large area of Sinian and Cambrian beach-facies development.(2)Beach-facies reservoirs were developed in the upper part of the paleo-uplift,while in the peripheral depression belts thick source rocks were developed like the Upper Sinian Doushantuo Fm and Lower Cambrian Qiongzhusi Fm,so there is a good sourceereservoir assemblage.(3)Since the Permian epoch,the DazhoueKaijiang paleo-uplift had gradually become elevated from the slope zone,where the Permian oil generation peak occurred in the slope or lower and gentle uplift belts,while the Triassic gas generation peak occurred in the higher uplift belts,both with a favorable condition for hydrocarbon accumulation.(4)The lower structural layers,including the Lower Cambrian and its underlying strata,in the East Sichuan Basin,are now equipped with a large-scale uplift with a simple structural configuration,above which a complete local structural trap was well developed with a good preserving condition.In conclusion,there are good forming conditions for hydrocarbon reservoirs in the SinianeLower Paleozoic strata in the DazhoueKaijiang paleo-uplift,East Sichuan Basin,in the higher parts of which the well-developed beach-facies reservoirs occupy an area of 8000 km2 and will be the next important gas exploration target in this basin.展开更多
There developed thick gypsum-salt strata in the Lower Paleozoic Ordovician in the Ordos Basin,particularly gypsum-salt in the 6th segment of the 5th member of Majiagou Fm(O_(1)m_(5)^(6))in a wide distribution,serving ...There developed thick gypsum-salt strata in the Lower Paleozoic Ordovician in the Ordos Basin,particularly gypsum-salt in the 6th segment of the 5th member of Majiagou Fm(O_(1)m_(5)^(6))in a wide distribution,serving as a good regional cap.Recent drilling and relevant studies have proven that the hydrocarbon-generating capacity of the marine-facies hydrocarbon source rocks under the Ordovician salt layers in the eastern Basin is poor on the whole,making it difficult to form“self-generating and self-preserving type”commercial gas reservoirs under the salt layer in Mizhi salt subsag.However,further research on reservoir-forming conditions under the gypsolyte on the west side of the salt subsag indicates that the O_(1)m_(5)^(7)-O_(1)m_(5)^(10)strata near the east side of the palaeo-uplift contact directly with the Upper Paleozoic coal measure source rocks,forming a“hydrocarbon supply window”;the Yanshan Movement caused the tectonic inversion of the basin main body,resulting in the tectonic framework“high in the east and low in the west”,which is conductive to the further migration of natural gas generated by the Upper Paleozoic coal measures to the updip high position of the east side along the O_(1)m_(5)^(7)-O_(1)m_(5)^(10)carrier beds after entering the dolomite reservoir under the gypsolyte through the“hydrocarbon-supply window”.In addition,the facies changes in the dolomite rocks under the gypsum-salt provide favorable barrier condition for the regional gathering of natural gas.Therefore,it is concluded through comprehensive analysis that reservoirs may form beneath the Ordovician gypsolith in the central region of the basin on the west side of the salt subsag with hydrocarbon supplied from the Upper Paleozoic source rocks of coal measures,which is expected to open up a new situation of natural gas exploration under the Ordovician gypsum-salt layer in the Ordos Basin.展开更多
Lower Paleozoic dark shale is developed in the western Middle Yangtze Block,which lays a material foundation for the enrichment and accumulation of marine shale gas.In order to ascertain the control action of geologic...Lower Paleozoic dark shale is developed in the western Middle Yangtze Block,which lays a material foundation for the enrichment and accumulation of marine shale gas.In order to ascertain the control action of geological structures on the differential preservation of shale gas and reveal the key factors in shale gas preservation,this paperfirstly analyzed the structure characteristics of this area,carried out structure pattern recognition and structural belt division,and studied structural deformation mode and intensity.Based on this,the relationships between different structure styles and shale gas preservation conditions were analyzed.Finally,combined with the structural deformation and the lithofacies paleogeographic characteristics of marine shale,the favorable exploration zones of shale gas were proposed.And the following research results were obtained.First,the western Middle Yangtze Block can be divided into four structural deformation belts,and three types of piggyback structural patterns have been identified,including restricted type,weakly reformed type and strongly reformed type.Second,the restricted type is located in the northwestern part of Hunan and Hubei Provinces.In this pattern,piggyback structure is incomplete and thrust belt and Compressive fold belt are developed.Third,the weakly and strongly reformed types are located in the western parts of Hunan and Hubei,and Wulingshan area,respectively.They both have complete piggyback structures,but the former has lower deformation intensity and has never undergone the late superimposed reformation.Fourth,there are three structural transfer belts in the western Middle Yangtze Block,i.e.the structural transfer belt between the East Sichuan faultefold belt and West HunaneHubei faultefold belt,the structural transfer belt between West HunaneHubei faultefold belt and Wulingshan faultefold belt,and the structural transfer belt between the outcrop and the hinterland of Middle Yangtze Block.Thefirst one is structurally transformed at the Qiyueshan fault.The East Sichuan faultefold belt on the west is an ejective fold with low fault density and formation denudation intensity,where shale gas is enriched in anticlines and slopes;while the West HunaneHubei faultefold belt on the east is a trough-like fold with strong faulting and high formation denudation intensity,where shale gas is enriched in residual synclines.In conclusion,shale gas preservation conditions of Upper Ordovician Wufeng FormationeLower Silurian Longmaxi Formation in this area are the best in Zigui syncline,thrustedetachment zone and western margin of Qiyueshan fault.The favorable exploration areas of shale gas of Lower Cambrian Niutitang Formation are distributed in the westernflank of Yichang Slope,Kaixian thrust zone,compressive fold zone and thrustedetachment zone.展开更多
The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7....The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7.8 earthquake happened. This earthquake occurred at a margin characterized by moderately big to giant earthquakes such as the 1906 （Mw 8.8）. A heavily sedimented trench explains the abnormal lengths of the rupture zones in this system as inhibits the role of natural barriers on the propagation of rupture zones. High amount of sediment thickness is associated with tropical climates, high erosion rates and eastward Pacific dominant winds that provoke orographic rainfalls over the Pacific slope of the Ecuatorian Andes. Offshore sediment dispersion off the oceanic trench is controlled by a close arrangement of two aseismic ridges that hit the Costa Rico and South Ecuador margin respectively and a mid ocean ridge that separates the Cocos and Nazca plate trapping sediments. Gravity field and Ocean Circulation Explorer （GOCE） satellite data are used in this work to test the possible relationship between gravity signal and earthquake rupture structure as well as registered aftershock seismic activity. Reduced vertical gravity gradient shows a good correlation with rupture structure for certain degrees of the harmonic expansion and related depth of the causative mass; indicating, such as in other analyzed cases along the subduction margin, that fore-arc structure derived from density heterogeneities explains at a certain extent propagation of the rupture zones. In this analysis the rupture zone of the April 2016 Ecuador earthquake developed through a relatively low density zone of the fore-arc sliver. Finally, aftershock sequence nucleated around the area of maximum slips in the rupture zone, suggesting that heterogeneous density structure of the fore-arc determined from gravity data could be used in forecasting potential damaged zones associated with big ruptures along the subduction border.展开更多
基金Project supported by the National Major S&T Project(No.2011ZX05004-002)the CNPC Major S&T Project(No.2014E-32).
文摘In the Sichuan Basin,the Middle Permian marine carbonate rocks are important natural gas pay zones with immense exploration potential,but the facies belts and distribution situations of layered dolomite reservoirs are not clear,which hinders the progress in natural gas exploration.In view of the sedimentary background of the Sichuan Basin,field outcrop section,drilling data and seismic data were comprehensively analyzed with the favorable reservoir intervals in the framework of sequence stratigraphy as the key research units.Research results about its lithofacies paleogeography were obtained as follows.First,a gentle slope SW high and NE low was presented during the sedimentation of the Qixia Fm in the Middle Permian.In the Maokou Fm of the Middle Permian,however,a series of the N-W trending intra-platform rifts were developed in this setting,and eventually a paleogeographic pattern of NE-dipping alternative uplift and depression was evolved.Second,in the Qixia Fm,the transgressive tract was in an open platform environment and the highstand system tract evolved into a rimmed platform.And the platform margin beach in the area of Jiange-Ya'an is the favorable reservoir facies belt.And third,in the Maokou Fm,the transgressive tract was in the carbonate shelf environment and the highstand system tract evolved into a rimmed platform.And the platform margin reef flat in the area of Jiange-Ya'an and the syneclise margin beach in the area of YantingeGuang'an are favorable reservoir facies belts.It is concluded that the two grain beach facies belts in the areas of Jiange-Ya'an and YantingeGuang'an were the favorable zones for the large-scale development of Middle Permian layered dolomite reservoirs and they are the main target of subsequent natural gas exploration.
基金Supported by the Cooperation Project of China National Natural Science Foundation and Petro China(U23B20154)Science and Technology Cooperation Project of Petro China and Southwest Petroleum University(2020CX010000)。
文摘Based on 2D and 3D seismic data and well logging data,this paper studies the distribution of well-seismic stratigraphic filling and shoal controlled reservoirs of Upper Cambrian Xixiangchi Formation in the south slope of Leshan-Longnüsi paleouplift in the Sichuan Basin,to reveal the genetic relationship between stratigraphic filling,paleogeomorphology and large-scale grain shoal.(1)The Xixiangchi Formation in the study area is overlapped and filled gradually to the Leshan-Longnüsi paleouplift,but gets thin sharply due to truncation only near the denudation pinch-out line of the paleouplift.Two overlap slope break belts and one erosion slope break belt are identified,and the Xixiangchi Formation is divided into 4 members from bottom to top.(2)The filling pattern of the overlapping at the base and erosion at the top indicates that the thickness of Xixiangchi Formation can reflect the pre-depositional paleogeomorphology,and reveals that the studied area has a monoclinal geomorphic feature of plunging to southeast and being controlled by multistage slope break belts.(3)The large-scale grain shoals and shoal controlled reservoirs are developed longitudinally in the third and fourth members of the Xixiangchi Formation,and laterally in the vicinity of the multistage overlap slope break belts.(4)Overlap slope break belts are closely related to northwest trending reverse faults.The western margin of the South China Plate converging with the Qiangtang-Himalaya massif in the middle-late Cambrian resulted in the rapid uplift of the northwestern margin of the Yangtze Plate and expanding toward southeast,leaving gradually plunging multistage slope breaks and large-scale northeast grain shoal reservoir belts.Considering oil and gas test results,it is predicted that the favorable exploration zone of the grain shoal controlled reservoirs covers an area of 3340 km^(2).
基金Major Project of National Science and Technology(No.2011ZX05004-005)Major Project of Exploration of PetroChina“Hydrocarbon Evaluation of Leshan-Longnüsi Palaeohigh in Sichuan Basin and Research on Exploration Support Technologies”(No.2012ZD01-03-01)。
文摘The Longwangmiao Fm gas pool was found in 2012 in Moxi area in Leshan-Longnüsi Paleouplift,central Sichuan Basin.Previous geological studies showed that the Lower Cambrian Longwangmiao Fm reservoir is mainly pore type reservoir of grain shoal facies,locally superimposed by the vuggy reservoir formed by Caledonian karstification,and the distribution of the reservoir has a critical control effect on the gas pool there.Therefore,the reservoir prediction in this area follows the approach of“looking for the overlap of shoal facies,karst,bright spots,and traps”.First,the favorable facies boundary and karstification effect range are defined based on sedimentary facies;on the basis of precise correlation of the top and bottom horizons of the reservoir,the favorable development area of the reservoir was then predicted according to the seismic response characteristics of“bright spots”of the Longwangmiao Fm reservoir;finally,favorable exploration areas were selected according to the effective configuration of reservoir and trap.Due to the horizontal change in reservoir and lithology,Longwangmiao Fm top has no uniform interface features on the seismic profile,making it difficult to trace.In the actual interpretation process,the underlying reference horizon is sought out first,then the bottom boundary of Longwangmiao Fm is correlated,and finally its top boundary is correlated.The prediction results indicated that the Longwangmiao reservoir distributes in band shape in a wide range around the Paleouplift;and the exploration prospects mainly involve three domains:lithologic-stratigraphic traps near the pinchout line of Longwangmiao Fm;lithologic traps formed by isolated shoal body;and structural and lithologic traps at the north flank of the Paleouplift.
基金Supported by the Petro China Science and Technology Project(2023YQX10101)National Natural Science Foundation of China(42372165)。
文摘Based on the research progress of the geological theory of coal-formed gas,the contributions of coal-formed gas to the natural gas reserves and production in China and to the development of natural gas in major gas-producing basins are analyzed,and the key favorable exploration zones for coal-formed gas in China are comprehensively evaluated.The following results are obtained.First,coal measures are good gas source rocks,and hydrocarbon generation from coal measure was dominated by gas,followed by oil.Second,a natural gas genetic identification index system based on stable isotopes,light hydrocarbon components,and biomarkers is established.Third,the quantitative and semi-quantitative factors controlling the formation of large gas fields,represented by the indicator of gas generation intensity greater than 20×10^(8) m^(3)/km^(2),are identified to guide the discovery of large gas fields in China.Fourth,coal-formed gas is the major contributor to the current natural gas reserves and production of China,both accounting for over 55%.The high proportion of coal-formed gas has enabled the Tarim,Sichuan and Ordos basins to be the major gas production areas in China.Fifth,coal rock gas is an important field for future exploration of coal-formed gas,and key zones include the Carboniferous Benxi Formation(Fm.)in the Wushenqi-Mizhi area of the Ordos Basin,the Permian Longtan Fm.in central-southern Sichuan Basin,the Jurassic Xishanyao Fm.in the southern margin and Luliang uplift of the Junggar Basin.Sixth,tight gas is the main area for increasing reserves and production,and the favorable exploration zones include the Carboniferous-Permian in southern Ordos Basin and the Bohai Bay Basin,and the Triassic Xujiahe Fm.in the transition zone between central and western Sichuan Basin.Seventh,the Jurassic in the southern margin of the Junggar Basin is a key favorable exploration zone for subsequent investigation of conventional coal-formed gas.These insights have valuable theoretical and practical significance for further developing and improving the theory of coal-formed gas,and guiding the exploration of coal-formed gas fields in China.
基金Project supported by the Science and Technology Project of PetroChina Company Limited“Hydrocarbon Accumulation Conditions in the Lower Paleozoic within the Ordos Basin and Target Evaluation”(No.:kt2018-04-03).
文摘In order to clarify the hydrocarbon accumulation significance and exploration prospect of the unconformity caused by the Huaiyuan movement in the Ordos Basin,this paper studies the spatial distribution and structural plane characteristics of this unconformity and its relationships with hydrocarbon accumulation by observing field outcrops and cores and analyzing logging data,based on the previous research results and the interpretation results of 2D and new 3D seismic data.And the following research results are obtained.First,the unconformity was mainly formed in the Floian Age of Early Ordovician and widely occurs at the bottom of the Jiawang Formation and the top of the Sanshanzi Formation and the related tectonism lasts 30 Myr.Second,basal conglomerate and sandstone less than 1 m in thickness are developed above the unconformity at the edge of the basin,while thin mudstone,argillaceous dolomite(limestone)and marl are developed above the unconformity in the central part of the basin.Third,the unconformity structurally consists of three layers,including a basal conglomerate layer,a paleosoil layer and a fullyesemi weathered carbonate layer from top to bottom,among which,the last one is 20-90 m in thickness with developed dissolution fractures and pores to form a quality reservoir.Fourth,the unconformity results in the development of a series of large valleys landforms,which incise the Lower OrdovicianeUpper Cambrian.Fifth,the unconformity can act as a good channel for hydrocarbon migration,and it connects with the unconformity caused by the Caledonian movement within the paleo-uplift of the Ordos Basin,which is favorable for the the hydrocarbon of different sources in the west side of the basin eastwards to migrate,accumulate and form a gas reservoir.In conclusion,the deep Lower Paleozoic related to the Huaiyuan unconformity is expected to be an important natural gas exploration field in the Ordos Basin.
基金Supported by the National Science and TechnologyMajor Project"Permian-Middle Triassic natural gas accumulations and evaluation in the Sichuan Basin"(No.:2016ZX05007-004)PetroChina Science and Tech-nology Major Project"Deep marine carbonate exploration&development field experiments in the Sichuan Basin"(No.:2014E-3208(GF)).
文摘Progress of natural gas exploration has recently been made in the Upper Paleozoic marine-facies reservoirs in the NW Sichuan Basin.It has been proved that the Middle Permian Qixia Fm pore-type dolomite reservoirs may be distributed continuously in a large area,besides,for thefirst time favorable gas-bearing Devonian dolomite reservoirs in great thickness were discovered in the downhole there.Recent research achievements indicate that:(1)The Lower Cambrian quality source rocks in huge thickness were found in the study sedimentary area with advantageous hydrocarbon source conditions.(2)Influenced by the Caledonian movement,the whole NW Sichuan Basin was lifted up to form a massive box-like NS-trending plunging uplift low steep in the west but high sluggish in the east,laying a robust foundation for the inheritance of Devonian,Carboniferous,and Permian platform margin reef large-scale sedimentation and dolomitization.(3)In the Upper Paleozoic strata,there were multiple planes of unconformity and multi-stage supergene karst occurred,improving the preservation and seeping capacity of reservoirs.(4)Tectonic deformations resulted from the nappe structure in the Longmenshan Mountain provided good hydrocarbon source fractures and sealing conditions for oil and gas reservoirs,which is conductive to the formation of a giant gas pool.It is concluded that the back-thrust anticline belt east to Hidden fault I in this study area has favorable conditions for large-scale structuralestratigraphic and structur-alelithologic combination traps.As suggested in this study,relatively strong dolomitization was found in the Qixia Fm in the Shejianhe RivereZhongba higher palaeogeomorphic deposit area,so the most favorable exploration target of the Qixia Fm will be around the central axis of Caledonian paleo-uplift to the east ridgeline,and the most favorable prospect of the Upper Palaeozoic will be the central axis to the west of Hidden fault I where three gas bearing reservoirs will be possibly explored at the same time.
基金supported by the National Major Science and Technology Project“Enrichment law and target evaluation of large gas fields in Permian-Middle Triassic in Sichuan Basin”(No.:2016ZX05007004)the CNPC Major Science and Technology Project“Study and application of key techniques for 30 billion m^(3)gas production in PetroChina Southwest Oil&Gas Field Company”(No.:2016E-06).
文摘Since 2014,great gas discoveries have been achieved in the Upper Paleozoic Shuangyushi zone in the piedmont zone of the Longmenshan mountains,northwestern Sichuan Basin,where multiple gas wells with industrial flows have been drilled and completed successively in the Middle Permian Qixia Fm and Middle Devonian Guanwushan Fm,etc.Along with the steady progress of exploration there,to make a further in-depth study on the characteristics of the frontal–piedmont zones in the Longmenshan thrust–nappe structures will be of great significance to both a better understanding of Upper Paleozoic gas reservoirs in this study area and the expansion of oil and gas exploration field.In view of this,based on the newly deployed 3D seismic surveys,gravity–magnetic–electronic data,and practical drilling information from exploration wells like Well ST 9,the characteristics of the frontal–piedmont zones in the Longmenshan thrust–nappe structures are analyzed as well as the features of the buried structures,gas reservoir forming conditions and exploration prospect there.The following findings were obtained:(1)A huge buried structure belt is developed underlying the Longmenshan front fault belt No.1(LSFFB 1)and marine strata are thus formed below the Lower Triassic Jialingjiang Fm due to the roles of compressive folding,extrusion and deformation;(2)The detachment horizons from LSFFB 1 go from shallower in the south to deeper in the north,turning from Cambrian slipping in the south to basement-involved in the north.The Paleozoic and its overlying strata were overall uplifted with a higher degree northward and so did the strata between the up-thrown and down-thrown sides of the faults with a greater displacement distance and higher folding degree,resulting in that the Paleozoic strata in the north are 1500 higher uplifted than those in the south;(3)In the western Jiange and Guangyuan areas,the eastern LSFFB 1 presents a tectonic pattern of“three steps”as a whole.In conclusion,there are good gas reservoir forming conditions in LSFFB 1,the down-thrown sides of which cover an area of 1800 km2,where the Guanwushan Fm and Qixia Fm provide good accumulation and preservation conditions for gas reservoirs,which will become favorable gas exploration targets in the deep marine strata in NW Sichuan Basin.
基金sponsored by Active Faults Seismic Hazard Assessment in Key Earthquake Monitoring and Defensive Region of China
文摘The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.
基金Petro China-Southwest Petroleum University Innovation Consortium Science and Technology Cooperation Project(2020CX010000)。
文摘Based on comprehensive analysis of cores,thin sections,logging and seismic data,the sequence stratigraphy and sedimentary evolution of the third and fourth members of Sinian Dengying Formation(Deng 3 and Deng 4 members for short)in the Gaomo area of Sichuan Basin were investigated,and the favorable zones for reservoir development in the Deng 3 Member and Deng 4 Member were predicted.(1)Two Type I and one Type II sequence boundaries are identified in the Deng 3 and Deng 4 members.Based on the identified sequence boundaries,the Deng 3 and Deng 4 members can be divided into two third order sequences SQ3 and SQ4,which are well-developed,isochronal and traceable in this area;the SQ3 thins from west to the east,and the SQ4 thins from northwest to southeast.(2)The sedimentary environment from the depositional period of SQ3 to SQ4 has experienced the evolution from mixed platform to rimmed platform,and the platform rimmed system on the west side is characterized by the development of platform margin microbial mound and grain shoal assemblages.The intraplatform area is a restricted platform facies composed of a variety of dolomites,and there are local micro-geomorphic highlands of different scales and scattered intraplatform mounds and shoals.(3)The Deng 4 Member reservoirs,with obvious facies-controlled characteristic,are mainly distributed in the upper part of high-frequency upward shallow cycle and the high-stand systems tract of the third-order sequence vertically,and are more developed in the platform margin belt than in the intraplatform belt,and more developed in the Gaoshiti platform margin belt than in the west Suining platform margin belt on the plane.(4)Three types of favorable reservoir zones of Deng 4 Member have been finely delineated with 3D seismic data;among them,the mound and shoal facies zones developed in the ancient highlands of the intraplatform are the first choice for the next exploration and development of the Deng 4 Member.
基金supported by the PetroChina Major S&T Project"Field Test of Exploration and Development Technologies for Decp Marine Carbonate Reservoirs in Sichuan Basin"(No.:2014E-3208(GF))。
文摘Great breakthrough recently achieved in the SinianeLower Paleozoic gas exploration in the LeshaneLongnu¨si paleo-uplift,Sichuan Basin,has also made a common view reached,i.e.,large-scale paleo-uplifts will be the most potential gas exploration target in the deep strata of this basin.Apart from the above-mentioned one,the other huge paleo-uplifts are all considered to be the ones formed in the post-Caledonian period,the impact of which,however,has rarely ever been discussed on the SinianeLower Paleozoic oil and gas reservoir formation.In view of this,based on outcrops,drilling and geophysical data,we analyzed the SinianeLower Paleozoic tectonic setting and sedimentary background in the East Sichuan Basin,studied the distribution rules of reservoirs and source rocks under the control of paleo-uplifts,andfinally discussed,on the basis of structural evolution analysis,the conditions for the formation of SinianeLower Paleozoic gas reservoirs in this study area.The followingfindings were achieved.(1)The DazhoueKaijiang inherited uplift in NE Sichuan Basin which was developed before the Middle Cambrian controlled a large area of Sinian and Cambrian beach-facies development.(2)Beach-facies reservoirs were developed in the upper part of the paleo-uplift,while in the peripheral depression belts thick source rocks were developed like the Upper Sinian Doushantuo Fm and Lower Cambrian Qiongzhusi Fm,so there is a good sourceereservoir assemblage.(3)Since the Permian epoch,the DazhoueKaijiang paleo-uplift had gradually become elevated from the slope zone,where the Permian oil generation peak occurred in the slope or lower and gentle uplift belts,while the Triassic gas generation peak occurred in the higher uplift belts,both with a favorable condition for hydrocarbon accumulation.(4)The lower structural layers,including the Lower Cambrian and its underlying strata,in the East Sichuan Basin,are now equipped with a large-scale uplift with a simple structural configuration,above which a complete local structural trap was well developed with a good preserving condition.In conclusion,there are good forming conditions for hydrocarbon reservoirs in the SinianeLower Paleozoic strata in the DazhoueKaijiang paleo-uplift,East Sichuan Basin,in the higher parts of which the well-developed beach-facies reservoirs occupy an area of 8000 km2 and will be the next important gas exploration target in this basin.
基金Special and Significant Project of National Science and Technology of the“12th Five-Year-Plan”:“Development of Large Oil/gas Fields and Coalbed Methane”(No.2011ZX05004-006).
文摘There developed thick gypsum-salt strata in the Lower Paleozoic Ordovician in the Ordos Basin,particularly gypsum-salt in the 6th segment of the 5th member of Majiagou Fm(O_(1)m_(5)^(6))in a wide distribution,serving as a good regional cap.Recent drilling and relevant studies have proven that the hydrocarbon-generating capacity of the marine-facies hydrocarbon source rocks under the Ordovician salt layers in the eastern Basin is poor on the whole,making it difficult to form“self-generating and self-preserving type”commercial gas reservoirs under the salt layer in Mizhi salt subsag.However,further research on reservoir-forming conditions under the gypsolyte on the west side of the salt subsag indicates that the O_(1)m_(5)^(7)-O_(1)m_(5)^(10)strata near the east side of the palaeo-uplift contact directly with the Upper Paleozoic coal measure source rocks,forming a“hydrocarbon supply window”;the Yanshan Movement caused the tectonic inversion of the basin main body,resulting in the tectonic framework“high in the east and low in the west”,which is conductive to the further migration of natural gas generated by the Upper Paleozoic coal measures to the updip high position of the east side along the O_(1)m_(5)^(7)-O_(1)m_(5)^(10)carrier beds after entering the dolomite reservoir under the gypsolyte through the“hydrocarbon-supply window”.In addition,the facies changes in the dolomite rocks under the gypsum-salt provide favorable barrier condition for the regional gathering of natural gas.Therefore,it is concluded through comprehensive analysis that reservoirs may form beneath the Ordovician gypsolith in the central region of the basin on the west side of the salt subsag with hydrocarbon supplied from the Upper Paleozoic source rocks of coal measures,which is expected to open up a new situation of natural gas exploration under the Ordovician gypsum-salt layer in the Ordos Basin.
基金Project supported by the National Science and Technology Major Special Project“Large Oil and Gas Fields and CBM Development”(No.2016ZX05002)China Petroleum&Chemical Corporation Science and Technology Department Pilot Project“Evolution and Breakthrough Direction of Hydrocarbon Accumulation in the Lower Assemblage of Western Middle Yangtze Block”(No.p16042).
文摘Lower Paleozoic dark shale is developed in the western Middle Yangtze Block,which lays a material foundation for the enrichment and accumulation of marine shale gas.In order to ascertain the control action of geological structures on the differential preservation of shale gas and reveal the key factors in shale gas preservation,this paperfirstly analyzed the structure characteristics of this area,carried out structure pattern recognition and structural belt division,and studied structural deformation mode and intensity.Based on this,the relationships between different structure styles and shale gas preservation conditions were analyzed.Finally,combined with the structural deformation and the lithofacies paleogeographic characteristics of marine shale,the favorable exploration zones of shale gas were proposed.And the following research results were obtained.First,the western Middle Yangtze Block can be divided into four structural deformation belts,and three types of piggyback structural patterns have been identified,including restricted type,weakly reformed type and strongly reformed type.Second,the restricted type is located in the northwestern part of Hunan and Hubei Provinces.In this pattern,piggyback structure is incomplete and thrust belt and Compressive fold belt are developed.Third,the weakly and strongly reformed types are located in the western parts of Hunan and Hubei,and Wulingshan area,respectively.They both have complete piggyback structures,but the former has lower deformation intensity and has never undergone the late superimposed reformation.Fourth,there are three structural transfer belts in the western Middle Yangtze Block,i.e.the structural transfer belt between the East Sichuan faultefold belt and West HunaneHubei faultefold belt,the structural transfer belt between West HunaneHubei faultefold belt and Wulingshan faultefold belt,and the structural transfer belt between the outcrop and the hinterland of Middle Yangtze Block.Thefirst one is structurally transformed at the Qiyueshan fault.The East Sichuan faultefold belt on the west is an ejective fold with low fault density and formation denudation intensity,where shale gas is enriched in anticlines and slopes;while the West HunaneHubei faultefold belt on the east is a trough-like fold with strong faulting and high formation denudation intensity,where shale gas is enriched in residual synclines.In conclusion,shale gas preservation conditions of Upper Ordovician Wufeng FormationeLower Silurian Longmaxi Formation in this area are the best in Zigui syncline,thrustedetachment zone and western margin of Qiyueshan fault.The favorable exploration areas of shale gas of Lower Cambrian Niutitang Formation are distributed in the westernflank of Yichang Slope,Kaixian thrust zone,compressive fold zone and thrustedetachment zone.
文摘The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7.8 earthquake happened. This earthquake occurred at a margin characterized by moderately big to giant earthquakes such as the 1906 （Mw 8.8）. A heavily sedimented trench explains the abnormal lengths of the rupture zones in this system as inhibits the role of natural barriers on the propagation of rupture zones. High amount of sediment thickness is associated with tropical climates, high erosion rates and eastward Pacific dominant winds that provoke orographic rainfalls over the Pacific slope of the Ecuatorian Andes. Offshore sediment dispersion off the oceanic trench is controlled by a close arrangement of two aseismic ridges that hit the Costa Rico and South Ecuador margin respectively and a mid ocean ridge that separates the Cocos and Nazca plate trapping sediments. Gravity field and Ocean Circulation Explorer （GOCE） satellite data are used in this work to test the possible relationship between gravity signal and earthquake rupture structure as well as registered aftershock seismic activity. Reduced vertical gravity gradient shows a good correlation with rupture structure for certain degrees of the harmonic expansion and related depth of the causative mass; indicating, such as in other analyzed cases along the subduction margin, that fore-arc structure derived from density heterogeneities explains at a certain extent propagation of the rupture zones. In this analysis the rupture zone of the April 2016 Ecuador earthquake developed through a relatively low density zone of the fore-arc sliver. Finally, aftershock sequence nucleated around the area of maximum slips in the rupture zone, suggesting that heterogeneous density structure of the fore-arc determined from gravity data could be used in forecasting potential damaged zones associated with big ruptures along the subduction border.
