The Afyon-Akşehir and Sinanpaşa grabens,located in the eastern part of the Akşehir-Simav Fault System,are important sedimentary basins in the western Anatolia,Türkiye.This region,particularly the western of Afyon...The Afyon-Akşehir and Sinanpaşa grabens,located in the eastern part of the Akşehir-Simav Fault System,are important sedimentary basins in the western Anatolia,Türkiye.This region,particularly the western of Afyon-Akşehir Graben,is a significant region known for its geothermal potential.The study focuses on analyzing gravity data to identify structural elements and examine the geological structures in the basins.The edge detection and enhancement techniques such as total horizontal gradient,tilt angle of the total horizontal gradient,enhanced dip angle and curvature analysis were used to investigate the structural lineaments in the area.Furthermore,2D/3D gravity modeling techniques were utilized to investigate the sedimentary depths of the Afyon-Akşehir and Sinanpaşa grabens.Based on the findings from the edge detection studies,three distinct linear features were highlighted in addition to previously identified geological structures.3D gravity inversion modeling reveals sedimentary basin depths of up to 470 m in Sinanpaşa Graben and 720 m in the western Afyon-Akşehir Graben.As a result of the structural mapping and 2D/3D gravity modeling studies,a structural uplift that may be linked to geothermal activity was detected among the local depressions in the Afyon-Akşehir Graben.The obtained features may be of potential interest for geothermal exploration;therefore,further investigations using additional geophysical data are recommended.展开更多
This study integrates gravity and aeromagnetic datasets to delineate basement depth and characterise the subsurface structural framework of the Gerad Graben in the western Sirt Basin,Libya.Techniques including high-pa...This study integrates gravity and aeromagnetic datasets to delineate basement depth and characterise the subsurface structural framework of the Gerad Graben in the western Sirt Basin,Libya.Techniques including high-pass filtering,Centre for Exploration Targeting(CET) edge detection,Source Parameter Imaging(SPI),and Euler Deconvolution(ED) were applied to residual gravity and residual reduced-topole(RTP) magnetic data to enhance fault mapping and basement morphology.Tests of various cutoff wavelengths show that 10 km for gravity and 15 km for magnetic data provide optimal resolution of shallow structures while preserving deeper trends.Forward 2D GM-SYS modelling and Werner Deconvolution further constrained the geometry and depth of intrusive bodies and fault systems.Results reveal a structurally complex graben with NE-SW,NW-SE,ENE-WSW,and N-S trending faults,indicating multiphase tectonic deformation.Graben-bounding faults show displacement values of600-4290 m,and basement depths in the central depocenter reach 4275-4300 m,validated by well NTF-50.Magnetic anomalies indicate intrusive igneous bodies,including NW-SE-trending sills and dikes,associated with the Tibesti and Al Haruj volcanic provinces.These intrusions likely caused localised heating,uplift,and fault reactivation.The integrated interpretation supports a tectonomagmatic evolution involving successive rifting phases from the Paleozoic to Cenozoic,influenced by inherited Precambrian structures.These features,coupled with substantial sediment infill and magmatic activity,enhance the hydrocarbon potential of the Gerad Graben,suggesting the presence of structural and stratigraphic traps within the broader of Sirt Basin petroleum system.展开更多
The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on t...The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.展开更多
Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems ass...Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems association characteristics of distinct depositional systems and spatial disposition are identified in different evolutionary period of the graben.Sequence Stratigraphic framework of the graben is mainly controlled by structural framework,tectonic movement, sources supply, expanding and contracting cycle of lake, position of depositional center. The key factors are structural framework and tectonic movemeat.Through systematic analysis Of regional tectonic settings, it is recognized that Eogene tectonic sequence of Yitong graben was formed under tenso-shear regime. It includes four sequences indicating four tectonic events attributed to tectonic movement of marginal faults.Neogene tectonic sequence was formed under compresso-shear regime, which includes coarse clastic deposits with a thicknessof 0-500m.Pattern of in the Yitong graben indicates the asymmetrical subsisence of marginal faults along two sides and the complicated structural framework.展开更多
The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayla...The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene （ca 15 Ma） to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.展开更多
The Albertine Graben in western Uganda is a Mesozoic-Cenozoic rift basin with petroleum exploration potential. A fundamental evaluation of petroleum potential of the graben is given based on field research, data proce...The Albertine Graben in western Uganda is a Mesozoic-Cenozoic rift basin with petroleum exploration potential. A fundamental evaluation of petroleum potential of the graben is given based on field research, data processing of gravity and magnetism, analysis of graben structure, geochemistry, reservoir and composition research. The basin has a double-layered framework and a large thickness of sediments. Gravity highs shown in a residual anomaly map might indicate central uplift zones. There exist at least two sets of mature or low-maturity source rocks corresponding to a certain source rock in the Cretaceous or Paleogene and Neogene strata. The graben has basement rock with potential reservoirs and Tertiary sandstone reservoirs and thus has petroleum exploration potential.展开更多
The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and...The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.展开更多
Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanx...Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanxi Graben, we measured the crustal thickness and Vp/Vs ratio beneath each station using the H-K stack of receiver functions. The observed crustal thickness shows obvious lateral variation, increasing gradually from east to west in the Shanxi Graben. Beneath the Shanxi Graben the crust is relatively thicker than both sides of the south and the north. In addition, the Vp/Vs ratio in the north of study zone is higher than that in the south. The highest Vp/Vs ratio exists in the crust of the Xinding basin and the Datong basin. Our study also suggests that high velocity ratio might result from the strong activities of the magmation and volcanism.展开更多
? The formation and evolution of the Tertiary transformextensional basins in Northeast China are controlled by extensional and strikeslidding combinational processes because the giant strikeslip fault system, ...? The formation and evolution of the Tertiary transformextensional basins in Northeast China are controlled by extensional and strikeslidding combinational processes because the giant strikeslip fault system, TanchengLujiang fault, cut through the basement or margin. Two kinds of structural styles have been identified in Northeast China: Yitong and Damintun styles. The former shows a clear asymmetry, in which sediments came mainly from two lateral sides and thick filling sediments were adjacent to the main strikeslip fault. The latter shows symmetry filling, in which sediments came from the long axial ends in addition to from two lateral sides. The tectonic evolution of Tertiary transformextensional basins in Northeast China underwent three stages: Eocene extensional, Oligocene transformextensional and Neogene transpressional stages.展开更多
In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Ce...In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.展开更多
The Euphrates Graben is located in eastern Syria.The Upper Triassic Mulussa F Formation sandstones serve as the primary reservoir intervals in the majority of the graben fields.The study’s findings were based on core...The Euphrates Graben is located in eastern Syria.The Upper Triassic Mulussa F Formation sandstones serve as the primary reservoir intervals in the majority of the graben fields.The study’s findings were based on core studies:petrographic examination of thin sections,scanning electron microscope(SEM),imaging of backscatter scanning electron microscope(BSE),X-ray microprobe examinations,and carbon-oxygen stable isotope analysis of microfracture-filling cements.Three of the most common types of microfracture found in the investigated sandstones are intragranular or intracrystalline microfractures,grain boundary or grain-edge microfractures,and transgranular(crossing grains)microfractures.Sandstone microfractures that are open and free of secondary mineralization improve sandstone storage and permeability.However,microfractures that are cemented and filled with secondary mineralization reduce storage and permeability.Common siderite and pyrite cements were identified within the microfractures and the nearby sandstone matrix.Larger anhedral or euhedral siderites are thought to form during shallow burial diagenesis,whereas poikilotopic siderites are thought to form during deep burial diagenesis.Poikilotopic pyrite is believed to be a diagenetic cement,which is attributed to the reduction of iron oxides present in the sediments in the presence of hydrocarbons.Microfractures reflect tectonic,overpressure,and diagenetic origins.Microfractures of tectonic origin are associated with folding and thrust activities over the Euphrates Graben area,and they were formed at the beginning of the Upper Triassic with siderite and pyrite cement equilibration temperatures of approximately 100–105℃,and they continued forming from the middle to the end of the Upper Triassic with cement equilibration temperatures of approximately 90–100℃in conjunction with the first phase of the Euphrates Graben.Microfractures related to diagenetic and overpressure processes are tension microfractures and were formed in compression settings during the Upper Triassic.展开更多
Recently,the researches on structure controls on sandbodies have provided a new method for predicting petroleum reservoirs.The Yitong（伊通） graben is situated in the northern section of the Tan-Lu（郯-庐） fault sys...Recently,the researches on structure controls on sandbodies have provided a new method for predicting petroleum reservoirs.The Yitong（伊通） graben is situated in the northern section of the Tan-Lu（郯-庐） fault system in eastern China.It was characterized by dual properties of strike-slip and extension in Cenozoic.Two types of intrabasinal structures were identified as oblique fault and trans-verse uplift in the graben.The oblique faults arranged en echelon in plain and locally presented nega-tive rosette structures on seismic profile,so they were closely derived from strike-slip movement of the northwestern boundary faults.Moreover,these oblique faults were divided to five zones.The three transverse uplifts,located corresponding to flattened southeast boundary faults,were mainly originated by displacement-gradient folding due to segmental extensional activities of southeast boundary faults.The large-scale sandbodies of subaqueous fan facies and fan delta facies had developed at the two types of intrabasinal structure zone.Based on analyzing the seismic facies,logging facies and seismic attrib-ute extractions,and on discovering many incised valleys at the oblique fault zones,the two types of in-trabasinal structures were revealed to have conducted drainage entering basin and further dispersing,and to have consequently controlled the development and distribution of sandbodies.展开更多
There are a series of basins in the Fenwei Graben. Field survey found that there took place several paleolake regressions or intensive stream down-incisions in all basins during the Mid-Late Quaternary. The lowest and...There are a series of basins in the Fenwei Graben. Field survey found that there took place several paleolake regressions or intensive stream down-incisions in all basins during the Mid-Late Quaternary. The lowest and oldest paleosol/Ioess units overlying three of the lacustrine terraces or alluvial ones and some paleomagenetism data from the lacustrine sediment indicate that the onset times of three paleolake regressions or intensive stream down-incisions are synchronous with the formation of Lg, L6 and L2 respectively in the Weihe Basin, $8, S~ and $1 respectively in the Linfen-Taiyuan-Xingding Basins, and Ls, Ls and L1 respectively in the Datong Basin. The difference in the onset time of each lake regressions or intensive stream down-incision in different basins reveals that the farther the basin is from the Tibetan Plateau, the later it took place. Taking these field facts and the former research re- sults in terms of the regional tectonic movement into account, it is inferred that the tectonic movement of the Tibetan Plateau most probably controlled such geomorphological- sedimentary evolution in the graben.展开更多
For the purpose of reservoir characterization of oilfields discovered in Albertine Graben, it is necessary to study the regional stratigraphy and sedimentary characteristics. The Semliki outcrops display a complete st...For the purpose of reservoir characterization of oilfields discovered in Albertine Graben, it is necessary to study the regional stratigraphy and sedimentary characteristics. The Semliki outcrops display a complete stratigraphy of Miocene, and the sediments are likely to provide valuable analogues for the reservoirs at Albertine Graben oilfields. The outcrops were observed and described in detail, mainly including lithology, colour, thickness, grain size and sedimentary structure. The sedimentology, depositional environment, climate, reservoir geometries and dimensions were analyzed. The Miocene stratigraphic section of Semliki basin was finally established, with lithology, sedimentary structure, sedimentary cycle, interpretation and climate information on it. It provides an analogy for the reservoir characterization, especially provides a basis for appropriate prediction of reservoir geometries in the field.展开更多
Results of this study are based on core materials description,thin sections,Cathodoluminescence(CL),and Scanning Electron Microscope(SEM)examinations.The Lower Cretaceous over the Euphrates Graben area was characteriz...Results of this study are based on core materials description,thin sections,Cathodoluminescence(CL),and Scanning Electron Microscope(SEM)examinations.The Lower Cretaceous over the Euphrates Graben area was characterized by carbonate sedimentation in shallow marine environments.The low energy lagoonal to inner shelf sediments of the Judea Formation includes micritic mudstone to wackestone texture,dolomitic limestones and dolostones.Two types of dolomites recognized in the carbonates of the Judea Formation,the preserving microcrystalline dolomites which commonly founded in the partially dolomitized micritic limestones,and the destructive coarsely crystalline dolomites which commonly founded in the dolostones and dolomitic limestones.Petrographic examinations indicate that the preserving microcrystalline dolomites represent subtidal cycles developed in a shoal to open marine depositional environments,they probably formed under conditions of the shallow burial diagenesis.The destructive coarsely crystalline dolomites may develop in more basinward,open marine environments under conditions of the deep burial diagenesis that accompanied by rising in temperature,pressure,and burial depth.It is believed that evolution of the diagenetic history of the Judean Formation sediments occurred in two diagenetic stages;the shallow burial diagenesis,and the deep burial diagenesis.Compaction processes,early fracturing,micritization,early calcite,and the early phase of dolomitization were part of the multiple diagenetic alterations during the shallow burial diagenesis.The deep burial diagenesis was marked by dissolution,late stage of dolomitization and replacement,mechanical and chemical compaction,and the late calcite precipitation.It is believed that dolomitization of the Judea Formation carbonates in the Euphrates Graben has contributed to improving the reservoir properties by increasing the porosity and thus the permeability.展开更多
This article presents the results of cementation characteristics and their effect on sandstone reservoir quality of the Upper Triassic Mulussa F, the Lower Cretaceous Lower Rutbah, and the Upper Cretaceous Post Judea ...This article presents the results of cementation characteristics and their effect on sandstone reservoir quality of the Upper Triassic Mulussa F, the Lower Cretaceous Lower Rutbah, and the Upper Cretaceous Post Judea Sandstone formations in selected fields in the Euphrates Graben area, Syria. This study emphasises the role of cementation in the evaluation of the diagenetic history of the sediments, developing effective porosity, as well as evaluation of reservoirs stimulation procedures and potential for formation damage of the sandstone reservoirs. Quartz cement is present as well developed tabular or pyramidal syntaxial overgrowths. Kaolinite cement is present as vermicular aggregates which are most abundant within sandstones of the Mulussa F Formation. Carbonate cements include siderite and dolomite. Four lithofacies were identified within the studied formations;lithofacies-1 and 2 correspond to fluvial depositional environments, lithofacies-3 and 4 correspond to fluvial to estuarine channel environments. The Post Judea Sandstone and the Lower Rutbah reservoir units are typically lithofacies-3 sequences in which quartz overgrowths are the dominant cement. Because the total cement is more extensive in the Post Judea Sandstone Formation than in the Lower Rutbah Formation, resulting in high porosity(up to 26%) and permeability(6 000 mD), the reservoir quality is predicted to be best in the Post Judea Sandstone Formation. The reservoir units in the Mulussa F Formation contain the highest cement volumes comprised of early siderite and kaolinite, which, with the development of compaction-resisting quartz overgrowths and resultant compactional pore volume loss, has resulted in typically lower porosity being preserved than in the Lower Rutbah and Post Judea Sandstone formations.展开更多
Crossing conjugate normal faults(CCNFs)are extensively developed in many hydrocarbon-producing basins,generally existing in the form of incomplete CCNFs.Nevertheless,the effect of the non-conjugate zone of the CCNFs o...Crossing conjugate normal faults(CCNFs)are extensively developed in many hydrocarbon-producing basins,generally existing in the form of incomplete CCNFs.Nevertheless,the effect of the non-conjugate zone of the CCNFs on the conjugate relay zone post late tectonic action has not been previously studied.We use 3D elastic-plastic modeling to investigate the influence of incomplete(i.e.,partially intersecting)CCNFs on the pattern of deformation of strata in the intersection region.A series of model simulations were performed to examine the effects of horizontal tectonic extension,fault size,and fault depth on the deformation of conjugate relay zones of incomplete CCNFs.Our analyses yielded the following results.(1)The model of incomplete conjugation predicts a convex-up style of deformation in the conjugate graben region superimposed on overall subsidence under applied horizontal tectonic extension.(2)The degree of convex-up deformation of the conjugate graben depends on the influence of the non-conjugate zone on the conjugate relay zone,which varies with the amount of horizontal tectonic extension,fault size,and fault burial depth.(3)Our results indicate that incomplete CCNFs can form convex-up deformation,similar to that in the Nanpu Sag area and provide a sound understanding of hydrocarbon migration and accumulation.展开更多
A fault accommodation zone is a type of structure that is defined as regulating displacement and strain between faults structure.Increasing numbers of fault accommodation zones are being identified in graben basins,in...A fault accommodation zone is a type of structure that is defined as regulating displacement and strain between faults structure.Increasing numbers of fault accommodation zones are being identified in graben basins,indicating the potential exploration target and petroleum accumulation areas.This study aims to analyze the formation mechanism and development of fault accommodation zones under combined stress by a numerical simulation method considering geomechanical modeling.Using three-dimensional(3-D)seismic interpretation and fractal dimension method,exampled with the Dongxin fault zone,the fault activity and fault combination pattern were conducted to quantitatively characterize the activity difference in fault accommodation zones.Combined with mechanical experiment test,a geomehcanical model was established for fault accommodation zones in a graben basin.Integrating the paleostress numerical simulations and structural physical simulation experiment,the developmental characteristics and genetic mechanism of fault accommodation zones were summarized.Influenced by multi movements and combined stresses,three significant tectonic evolution stages of the Dongxing Fault Zone(DXFZ)were distinguished:During the E_(s)^(3)sedimentary period,the large difference in the stress,strain,and rupture distribution in various faults were significant,and this stage was the key generation period for the prototype of the DXFZ,including the FAZ between large-scale faults.During the E_(s)^(2)sedimentary period,the EW-trending symmetric with opposite dipping normal faults and the NE-SW trending faults with large scale were furtherly developed.The junction area of two secondary normal faults were prone to be ruptured,performing significant period for inheriting and developing characteristics of fault accommodation zones.During the Es1 sedimentary period,the high-order faults in the DXFZ exhibited the obvious fault depressions and strike-slip activity,and the fault accommodation zones were furtherly inherited and developed.This stage was the molded and formative period of the FAZ,the low-order faults,and the depression in the DXFZ.展开更多
Based on the study of ore deposits and orebody structures of two sedimentary-exhalative ore deposits, i.e., Changba and Xitieshan Ore Deposits, it is found that the structural patterns of metallogenic basin of seafloo...Based on the study of ore deposits and orebody structures of two sedimentary-exhalative ore deposits, i.e., Changba and Xitieshan Ore Deposits, it is found that the structural patterns of metallogenic basin of seafloor exhalative sulfide deposits in the ancient graben systems are controlled by relay structures in normal faults. The shapes of metallogenic basins are composed of tilting ramp, fault-tip ramp and relay ramp, which dominate migration of gravity current of ore-hosted fluid and shape of orebody sedimentary fan in the ramp. By measuring and comparing the difference of length-to-thickness ratios of orebody sedimentary fan, the result shows that the occurrence of the ramp has a remarkable impact on the shape of orebody.展开更多
文摘The Afyon-Akşehir and Sinanpaşa grabens,located in the eastern part of the Akşehir-Simav Fault System,are important sedimentary basins in the western Anatolia,Türkiye.This region,particularly the western of Afyon-Akşehir Graben,is a significant region known for its geothermal potential.The study focuses on analyzing gravity data to identify structural elements and examine the geological structures in the basins.The edge detection and enhancement techniques such as total horizontal gradient,tilt angle of the total horizontal gradient,enhanced dip angle and curvature analysis were used to investigate the structural lineaments in the area.Furthermore,2D/3D gravity modeling techniques were utilized to investigate the sedimentary depths of the Afyon-Akşehir and Sinanpaşa grabens.Based on the findings from the edge detection studies,three distinct linear features were highlighted in addition to previously identified geological structures.3D gravity inversion modeling reveals sedimentary basin depths of up to 470 m in Sinanpaşa Graben and 720 m in the western Afyon-Akşehir Graben.As a result of the structural mapping and 2D/3D gravity modeling studies,a structural uplift that may be linked to geothermal activity was detected among the local depressions in the Afyon-Akşehir Graben.The obtained features may be of potential interest for geothermal exploration;therefore,further investigations using additional geophysical data are recommended.
文摘This study integrates gravity and aeromagnetic datasets to delineate basement depth and characterise the subsurface structural framework of the Gerad Graben in the western Sirt Basin,Libya.Techniques including high-pass filtering,Centre for Exploration Targeting(CET) edge detection,Source Parameter Imaging(SPI),and Euler Deconvolution(ED) were applied to residual gravity and residual reduced-topole(RTP) magnetic data to enhance fault mapping and basement morphology.Tests of various cutoff wavelengths show that 10 km for gravity and 15 km for magnetic data provide optimal resolution of shallow structures while preserving deeper trends.Forward 2D GM-SYS modelling and Werner Deconvolution further constrained the geometry and depth of intrusive bodies and fault systems.Results reveal a structurally complex graben with NE-SW,NW-SE,ENE-WSW,and N-S trending faults,indicating multiphase tectonic deformation.Graben-bounding faults show displacement values of600-4290 m,and basement depths in the central depocenter reach 4275-4300 m,validated by well NTF-50.Magnetic anomalies indicate intrusive igneous bodies,including NW-SE-trending sills and dikes,associated with the Tibesti and Al Haruj volcanic provinces.These intrusions likely caused localised heating,uplift,and fault reactivation.The integrated interpretation supports a tectonomagmatic evolution involving successive rifting phases from the Paleozoic to Cenozoic,influenced by inherited Precambrian structures.These features,coupled with substantial sediment infill and magmatic activity,enhance the hydrocarbon potential of the Gerad Graben,suggesting the presence of structural and stratigraphic traps within the broader of Sirt Basin petroleum system.
文摘The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.
文摘Yitong graben belongs to the north segment of the Tanlu fault belt .It was infilled with Eogene, Neogene and Quaternary clastic deposits, each Of them represents a distinct tectonic sequence.Six types of systems association characteristics of distinct depositional systems and spatial disposition are identified in different evolutionary period of the graben.Sequence Stratigraphic framework of the graben is mainly controlled by structural framework,tectonic movement, sources supply, expanding and contracting cycle of lake, position of depositional center. The key factors are structural framework and tectonic movemeat.Through systematic analysis Of regional tectonic settings, it is recognized that Eogene tectonic sequence of Yitong graben was formed under tenso-shear regime. It includes four sequences indicating four tectonic events attributed to tectonic movement of marginal faults.Neogene tectonic sequence was formed under compresso-shear regime, which includes coarse clastic deposits with a thicknessof 0-500m.Pattern of in the Yitong graben indicates the asymmetrical subsisence of marginal faults along two sides and the complicated structural framework.
文摘The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene （ca 15 Ma） to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.
文摘The Albertine Graben in western Uganda is a Mesozoic-Cenozoic rift basin with petroleum exploration potential. A fundamental evaluation of petroleum potential of the graben is given based on field research, data processing of gravity and magnetism, analysis of graben structure, geochemistry, reservoir and composition research. The basin has a double-layered framework and a large thickness of sediments. Gravity highs shown in a residual anomaly map might indicate central uplift zones. There exist at least two sets of mature or low-maturity source rocks corresponding to a certain source rock in the Cretaceous or Paleogene and Neogene strata. The graben has basement rock with potential reservoirs and Tertiary sandstone reservoirs and thus has petroleum exploration potential.
基金granted by the Geological Investigation Project of China Geological Survey (Grant Nos.1212011120102 and 12120115003501)
文摘The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.
基金supported by the National Natural Science Foundation of China(No.41230210)the Projects of International Cooperation and Exchanges from the Ministry of Science and Technology of China(Grant No.2010DFB20190)the Fundamental Research Funds for the Institute of Earthquake Science,China Earthquake Administration
文摘Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanxi Graben, we measured the crustal thickness and Vp/Vs ratio beneath each station using the H-K stack of receiver functions. The observed crustal thickness shows obvious lateral variation, increasing gradually from east to west in the Shanxi Graben. Beneath the Shanxi Graben the crust is relatively thicker than both sides of the south and the north. In addition, the Vp/Vs ratio in the north of study zone is higher than that in the south. The highest Vp/Vs ratio exists in the crust of the Xinding basin and the Datong basin. Our study also suggests that high velocity ratio might result from the strong activities of the magmation and volcanism.
文摘? The formation and evolution of the Tertiary transformextensional basins in Northeast China are controlled by extensional and strikeslidding combinational processes because the giant strikeslip fault system, TanchengLujiang fault, cut through the basement or margin. Two kinds of structural styles have been identified in Northeast China: Yitong and Damintun styles. The former shows a clear asymmetry, in which sediments came mainly from two lateral sides and thick filling sediments were adjacent to the main strikeslip fault. The latter shows symmetry filling, in which sediments came from the long axial ends in addition to from two lateral sides. The tectonic evolution of Tertiary transformextensional basins in Northeast China underwent three stages: Eocene extensional, Oligocene transformextensional and Neogene transpressional stages.
基金supported by the National Natural Science Foundation of China (No. 41502203)the Scientific Research Foundation for Returned Overseas Scholars of China (awarded to G. Rao)+1 种基金the Natural Science Foundation of Zhejiang Province (No. LY15D02001)a Science Project (No. 23253002)from the Ministry of Education, Culture, Sports, Science and Technology of Japan
文摘In this paper, we focus on the characteristics of the landslides developed in the epicentral area of AD 1556 M^8.5 Huaxian Earthquake, and discuss their relations to the active normal faults in the SE Weihe Graben, Central China. The results from analyzing high-resolution remote-sensing imagery and digital elevation models（DEMs）, in combination with field survey, demonstrate that：（i） the landslides observed in the study area range from small-scale debris/rock falls to large-scale rock avalanches;（ii） the landslides are mostly developed upon steep slopes of ≥30°; and（iii） the step-like normal-fault scarps along the range-fronts of the Huashan Mountains as well as the thick loess sediments in the Weinan area may facilitate the occurrence of large landslides. The results presented in this study would be helpful to assess the potential landslide hazards in densely-populated areas affected by active normal faulting.
基金supported by the Ministry of Science and Higher Education of the Russian Federation under the agreement within the framework of the development program for a world-class research center“Efficient Development of the Global Liquid Hydrocarbon Reserves”(No.075-15-2020-931)。
文摘The Euphrates Graben is located in eastern Syria.The Upper Triassic Mulussa F Formation sandstones serve as the primary reservoir intervals in the majority of the graben fields.The study’s findings were based on core studies:petrographic examination of thin sections,scanning electron microscope(SEM),imaging of backscatter scanning electron microscope(BSE),X-ray microprobe examinations,and carbon-oxygen stable isotope analysis of microfracture-filling cements.Three of the most common types of microfracture found in the investigated sandstones are intragranular or intracrystalline microfractures,grain boundary or grain-edge microfractures,and transgranular(crossing grains)microfractures.Sandstone microfractures that are open and free of secondary mineralization improve sandstone storage and permeability.However,microfractures that are cemented and filled with secondary mineralization reduce storage and permeability.Common siderite and pyrite cements were identified within the microfractures and the nearby sandstone matrix.Larger anhedral or euhedral siderites are thought to form during shallow burial diagenesis,whereas poikilotopic siderites are thought to form during deep burial diagenesis.Poikilotopic pyrite is believed to be a diagenetic cement,which is attributed to the reduction of iron oxides present in the sediments in the presence of hydrocarbons.Microfractures reflect tectonic,overpressure,and diagenetic origins.Microfractures of tectonic origin are associated with folding and thrust activities over the Euphrates Graben area,and they were formed at the beginning of the Upper Triassic with siderite and pyrite cement equilibration temperatures of approximately 100–105℃,and they continued forming from the middle to the end of the Upper Triassic with cement equilibration temperatures of approximately 90–100℃in conjunction with the first phase of the Euphrates Graben.Microfractures related to diagenetic and overpressure processes are tension microfractures and were formed in compression settings during the Upper Triassic.
基金supported by the National Natural Science Foundation of China(No.40872077)
文摘Recently,the researches on structure controls on sandbodies have provided a new method for predicting petroleum reservoirs.The Yitong（伊通） graben is situated in the northern section of the Tan-Lu（郯-庐） fault system in eastern China.It was characterized by dual properties of strike-slip and extension in Cenozoic.Two types of intrabasinal structures were identified as oblique fault and trans-verse uplift in the graben.The oblique faults arranged en echelon in plain and locally presented nega-tive rosette structures on seismic profile,so they were closely derived from strike-slip movement of the northwestern boundary faults.Moreover,these oblique faults were divided to five zones.The three transverse uplifts,located corresponding to flattened southeast boundary faults,were mainly originated by displacement-gradient folding due to segmental extensional activities of southeast boundary faults.The large-scale sandbodies of subaqueous fan facies and fan delta facies had developed at the two types of intrabasinal structure zone.Based on analyzing the seismic facies,logging facies and seismic attrib-ute extractions,and on discovering many incised valleys at the oblique fault zones,the two types of in-trabasinal structures were revealed to have conducted drainage entering basin and further dispersing,and to have consequently controlled the development and distribution of sandbodies.
基金Foundation： National Natural Science Foundation of China, No.41371021
文摘There are a series of basins in the Fenwei Graben. Field survey found that there took place several paleolake regressions or intensive stream down-incisions in all basins during the Mid-Late Quaternary. The lowest and oldest paleosol/Ioess units overlying three of the lacustrine terraces or alluvial ones and some paleomagenetism data from the lacustrine sediment indicate that the onset times of three paleolake regressions or intensive stream down-incisions are synchronous with the formation of Lg, L6 and L2 respectively in the Weihe Basin, $8, S~ and $1 respectively in the Linfen-Taiyuan-Xingding Basins, and Ls, Ls and L1 respectively in the Datong Basin. The difference in the onset time of each lake regressions or intensive stream down-incision in different basins reveals that the farther the basin is from the Tibetan Plateau, the later it took place. Taking these field facts and the former research re- sults in terms of the regional tectonic movement into account, it is inferred that the tectonic movement of the Tibetan Plateau most probably controlled such geomorphological- sedimentary evolution in the graben.
文摘For the purpose of reservoir characterization of oilfields discovered in Albertine Graben, it is necessary to study the regional stratigraphy and sedimentary characteristics. The Semliki outcrops display a complete stratigraphy of Miocene, and the sediments are likely to provide valuable analogues for the reservoirs at Albertine Graben oilfields. The outcrops were observed and described in detail, mainly including lithology, colour, thickness, grain size and sedimentary structure. The sedimentology, depositional environment, climate, reservoir geometries and dimensions were analyzed. The Miocene stratigraphic section of Semliki basin was finally established, with lithology, sedimentary structure, sedimentary cycle, interpretation and climate information on it. It provides an analogy for the reservoir characterization, especially provides a basis for appropriate prediction of reservoir geometries in the field.
基金supported by the Ministry of Science and Higher Education of the Russian Federation under agreement No.075-15-2020-931 within the framework of the development program for a world-class Research Center"Efficient development of the global liquid hydrocarbon reserves"。
文摘Results of this study are based on core materials description,thin sections,Cathodoluminescence(CL),and Scanning Electron Microscope(SEM)examinations.The Lower Cretaceous over the Euphrates Graben area was characterized by carbonate sedimentation in shallow marine environments.The low energy lagoonal to inner shelf sediments of the Judea Formation includes micritic mudstone to wackestone texture,dolomitic limestones and dolostones.Two types of dolomites recognized in the carbonates of the Judea Formation,the preserving microcrystalline dolomites which commonly founded in the partially dolomitized micritic limestones,and the destructive coarsely crystalline dolomites which commonly founded in the dolostones and dolomitic limestones.Petrographic examinations indicate that the preserving microcrystalline dolomites represent subtidal cycles developed in a shoal to open marine depositional environments,they probably formed under conditions of the shallow burial diagenesis.The destructive coarsely crystalline dolomites may develop in more basinward,open marine environments under conditions of the deep burial diagenesis that accompanied by rising in temperature,pressure,and burial depth.It is believed that evolution of the diagenetic history of the Judean Formation sediments occurred in two diagenetic stages;the shallow burial diagenesis,and the deep burial diagenesis.Compaction processes,early fracturing,micritization,early calcite,and the early phase of dolomitization were part of the multiple diagenetic alterations during the shallow burial diagenesis.The deep burial diagenesis was marked by dissolution,late stage of dolomitization and replacement,mechanical and chemical compaction,and the late calcite precipitation.It is believed that dolomitization of the Judea Formation carbonates in the Euphrates Graben has contributed to improving the reservoir properties by increasing the porosity and thus the permeability.
基金supported by the Ministry of Science and Higher Education of the Russian Federation under the agreement within the framework of the development program for a world-class research center “Efficient Development of the Global Liquid Hydrocarbon Reserves”(No. 075-15-2020-931)。
文摘This article presents the results of cementation characteristics and their effect on sandstone reservoir quality of the Upper Triassic Mulussa F, the Lower Cretaceous Lower Rutbah, and the Upper Cretaceous Post Judea Sandstone formations in selected fields in the Euphrates Graben area, Syria. This study emphasises the role of cementation in the evaluation of the diagenetic history of the sediments, developing effective porosity, as well as evaluation of reservoirs stimulation procedures and potential for formation damage of the sandstone reservoirs. Quartz cement is present as well developed tabular or pyramidal syntaxial overgrowths. Kaolinite cement is present as vermicular aggregates which are most abundant within sandstones of the Mulussa F Formation. Carbonate cements include siderite and dolomite. Four lithofacies were identified within the studied formations;lithofacies-1 and 2 correspond to fluvial depositional environments, lithofacies-3 and 4 correspond to fluvial to estuarine channel environments. The Post Judea Sandstone and the Lower Rutbah reservoir units are typically lithofacies-3 sequences in which quartz overgrowths are the dominant cement. Because the total cement is more extensive in the Post Judea Sandstone Formation than in the Lower Rutbah Formation, resulting in high porosity(up to 26%) and permeability(6 000 mD), the reservoir quality is predicted to be best in the Post Judea Sandstone Formation. The reservoir units in the Mulussa F Formation contain the highest cement volumes comprised of early siderite and kaolinite, which, with the development of compaction-resisting quartz overgrowths and resultant compactional pore volume loss, has resulted in typically lower porosity being preserved than in the Lower Rutbah and Post Judea Sandstone formations.
基金supported by the National Key Research and Development Program of China(No.2022YFF0800703)the National Natural Science Foundation of China(No.42230309).
文摘Crossing conjugate normal faults(CCNFs)are extensively developed in many hydrocarbon-producing basins,generally existing in the form of incomplete CCNFs.Nevertheless,the effect of the non-conjugate zone of the CCNFs on the conjugate relay zone post late tectonic action has not been previously studied.We use 3D elastic-plastic modeling to investigate the influence of incomplete(i.e.,partially intersecting)CCNFs on the pattern of deformation of strata in the intersection region.A series of model simulations were performed to examine the effects of horizontal tectonic extension,fault size,and fault depth on the deformation of conjugate relay zones of incomplete CCNFs.Our analyses yielded the following results.(1)The model of incomplete conjugation predicts a convex-up style of deformation in the conjugate graben region superimposed on overall subsidence under applied horizontal tectonic extension.(2)The degree of convex-up deformation of the conjugate graben depends on the influence of the non-conjugate zone on the conjugate relay zone,which varies with the amount of horizontal tectonic extension,fault size,and fault burial depth.(3)Our results indicate that incomplete CCNFs can form convex-up deformation,similar to that in the Nanpu Sag area and provide a sound understanding of hydrocarbon migration and accumulation.
基金This research was supported by the Major Scientific and Technological Projects of CNPC under grant ZD2019-183-006the National Natural Science Foundation of China(42072234).The authors would like to appreciate all the people,who supported the data,testing,and analyses.Many thanks to the anonymous reviewers,whose comments improve the quality of our manuscript.
文摘A fault accommodation zone is a type of structure that is defined as regulating displacement and strain between faults structure.Increasing numbers of fault accommodation zones are being identified in graben basins,indicating the potential exploration target and petroleum accumulation areas.This study aims to analyze the formation mechanism and development of fault accommodation zones under combined stress by a numerical simulation method considering geomechanical modeling.Using three-dimensional(3-D)seismic interpretation and fractal dimension method,exampled with the Dongxin fault zone,the fault activity and fault combination pattern were conducted to quantitatively characterize the activity difference in fault accommodation zones.Combined with mechanical experiment test,a geomehcanical model was established for fault accommodation zones in a graben basin.Integrating the paleostress numerical simulations and structural physical simulation experiment,the developmental characteristics and genetic mechanism of fault accommodation zones were summarized.Influenced by multi movements and combined stresses,three significant tectonic evolution stages of the Dongxing Fault Zone(DXFZ)were distinguished:During the E_(s)^(3)sedimentary period,the large difference in the stress,strain,and rupture distribution in various faults were significant,and this stage was the key generation period for the prototype of the DXFZ,including the FAZ between large-scale faults.During the E_(s)^(2)sedimentary period,the EW-trending symmetric with opposite dipping normal faults and the NE-SW trending faults with large scale were furtherly developed.The junction area of two secondary normal faults were prone to be ruptured,performing significant period for inheriting and developing characteristics of fault accommodation zones.During the Es1 sedimentary period,the high-order faults in the DXFZ exhibited the obvious fault depressions and strike-slip activity,and the fault accommodation zones were furtherly inherited and developed.This stage was the molded and formative period of the FAZ,the low-order faults,and the depression in the DXFZ.
文摘Based on the study of ore deposits and orebody structures of two sedimentary-exhalative ore deposits, i.e., Changba and Xitieshan Ore Deposits, it is found that the structural patterns of metallogenic basin of seafloor exhalative sulfide deposits in the ancient graben systems are controlled by relay structures in normal faults. The shapes of metallogenic basins are composed of tilting ramp, fault-tip ramp and relay ramp, which dominate migration of gravity current of ore-hosted fluid and shape of orebody sedimentary fan in the ramp. By measuring and comparing the difference of length-to-thickness ratios of orebody sedimentary fan, the result shows that the occurrence of the ramp has a remarkable impact on the shape of orebody.
