Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inve...Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.展开更多
In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovi...In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.展开更多
The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems m...The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems may have a significant impact on reservoir performance.This article focuses on the core-and laboratory-based characterization of fractures.Through the developmental degrees,extended scale,output state and filling characteristics of various types of fractures,the results show that there are three distinct fracture types:1)nearly vertical fractures,2)oblique fractures,and 3)horizontal fractures.Based on a systematic study of the characterization of reservoir space,the main geologic setting of natural gas accumulation and the regional tectonic background,type 1 is mainly driven by the tectonic formation mechanism,and type 3 and parts of low-angle fractures in type 2 are induced by the diagenetic formation mechanism.While recovered paleopressure for methane-rich aqueous inclusions trapped in fracture-filling cement indicates that the fracture opening and growth are consistent with gas maturation and charge and such high-angle fractures in type 2 are caused by the compound formation mechanism.The fractures to hydrocarbon accumulation may play a more significant role in improving the quality of reservoir porosity.Furthermore,connected fractures,dissolved pores and cavities together constitute the three-dimensional pore-cave-fracture network pathway systems,with faults serving as the dominant charge pathways of highly pressurized gas in the study area.Our results demonstrate that protracted growth of a pervasive fracture system is not only the consequence of various formation mechanisms but also intrinsic to quasi-continuous accumulation reservoirs.展开更多
Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ord...Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ordovician faunas of J(a|¨)mtland have developed against a background of intense and rapid global climate change.The faunas are present approximately in the middle of the Kyrk(?)s Quartzite in the east and occur in the uppermost Kogsta Siltstone in the west. Changes in faunas and depositional environments provide regional evidence of these global cooling and regressive events.The faunas occur in shale and siltstone facies and are used to effect展开更多
Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is ...Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is point out that the development of hercynian fracture-vuggy and filling succession of fracture-cave mineral was under the background of the mingling of low-temperature magma hydrotherm and the brine of upper strata. There are overlap or associate relations between generate of fluorite and buried dissolution or oil-gas migration. It was volume decreased 26.4% after calcite metasomatic by fluorite, this reaction made fluorite engender plentiful intergranular space. It’s created appreciable reservoir space. At same time, hydrotherm carried by fluorite generating could erode adjacent rock though fracture or fissure, forming irregular fracture-cave system, and also accompanied with hydrocarbon migration. The time of hydrocarbon migration and accumulation happened in late hercynian-indosinian is inosculates with the sedimentation time such as fluorite and several hydrothermal mineral.展开更多
Based on the analysis of the morphology, order, cathodoluminescence and microelement of the calcite crystals in the pores of Upper Ordovician limestone in Tazhong oilfield of Tarim Basin, this paper suggest that the c...Based on the analysis of the morphology, order, cathodoluminescence and microelement of the calcite crystals in the pores of Upper Ordovician limestone in Tazhong oilfield of Tarim Basin, this paper suggest that the calcite crystals can divided 11 kinds of cements into three stages, and confirms their cementation sequence characteristics and formation environment. First stage of the cementation occurred on the bottom of the diagenetic environment, the product of which mainly are microcrystalline, fine shape, radiation fibrous, fasciculation, radiation axis shape calcites and a ball-like aragonite, whose filling pore is 0%–30%; the second one occurred in the atmospheric fresh water environment, with main cement types of crescent or pendulous shape, vadose silt, hyperplasia of coaxial, the filling pore of which is 5%–100%; the third one occurred in a burial environment, the crystals of which are bright and thick, mainly coarse sparry and poikilitic calcite, with filling pore of 5%–5%. In this paper, influence from each stage of cementation on porosity is analyzed, and pore evolution is established.展开更多
The buried hill in the Jizhong depression contains abundant petroleum reserves and are important production areas.The Ordovician buried hill has restricted the discovery of new oil and gas exploration targets because ...The buried hill in the Jizhong depression contains abundant petroleum reserves and are important production areas.The Ordovician buried hill has restricted the discovery of new oil and gas exploration targets because of its strong reservoir heterogeneity and complex reservoir-controlling factors.Based on a large volume of core,thin section,logging,seismic,and geochemical data and numerous geological analyses,the reservoir-forming conditions and modes were systematically analyzed to guide the exploration and achieve important breakthroughs in the Yangshuiwu and Wen an slope buried hills.The study revealed that three sets of source rocks of the third and fourth members of the Shahejie Formation from the Paleogene and Carboniferous-Permian were developed in the Jizhong depression,providing sufficient material basis for the formation of buried hill oil and gas reservoirs.The reservoir control mechanism involving the three major factors of“cloud-karst-fault”was clarified,and karst cave,fracture fissure-pore,and cloud pore type reservoir models were established,thereby expanding the exploration potential.Controlled by the superposition of multi-stage tectonic processes during the Indosinian,Yanshanian,and Himalayan,two genetic buried hill trap types of uplift-depression and depression-uplift were formed.Based on the analysis of reservoir-forming factors of the Ordovician buried hill,three buried hill oil and gas reservoir-forming models were identified:low-level tectonic-lithologic composite quasi-layered buried hill,medium-level paleo-storage paleo-block buried hill,and high-level paleo-storage new-block buried hill.Comprehensive evaluations indicate that the reservoir-forming conditions of the low-level tectonic-lithologic composite quasi-layered buried hill in the northern portion of the Jizhong depression are the most favorable and that the Sicundian and Xinzhen buried hills are favorable areas for future exploration.展开更多
文摘Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG.
基金Project(2008ZX05004-004)supported by the State Key Scientific Research Programs,ChinaProject(SZD0414)supported by the Sichuan Province Key Discipline Construction Project,ChinaProject(KZCX2-YW-Q05-01)supported by the Chinese Academy of Sciences Innovation Engineering Directional Project
文摘In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.
基金Project (2011ZX05007-004) supported by the National Sciences and Technologies,ChinaProject (41502132) supported by the National Natural Science Foundation of China
文摘The lower Ordovician mid-assemblage Formations in the central Ordos Basin of China host prolific gas resources,and most hydrocarbon reserves are stored in naturally-fractured reservoirs.Thus,fracture pathway systems may have a significant impact on reservoir performance.This article focuses on the core-and laboratory-based characterization of fractures.Through the developmental degrees,extended scale,output state and filling characteristics of various types of fractures,the results show that there are three distinct fracture types:1)nearly vertical fractures,2)oblique fractures,and 3)horizontal fractures.Based on a systematic study of the characterization of reservoir space,the main geologic setting of natural gas accumulation and the regional tectonic background,type 1 is mainly driven by the tectonic formation mechanism,and type 3 and parts of low-angle fractures in type 2 are induced by the diagenetic formation mechanism.While recovered paleopressure for methane-rich aqueous inclusions trapped in fracture-filling cement indicates that the fracture opening and growth are consistent with gas maturation and charge and such high-angle fractures in type 2 are caused by the compound formation mechanism.The fractures to hydrocarbon accumulation may play a more significant role in improving the quality of reservoir porosity.Furthermore,connected fractures,dissolved pores and cavities together constitute the three-dimensional pore-cave-fracture network pathway systems,with faults serving as the dominant charge pathways of highly pressurized gas in the study area.Our results demonstrate that protracted growth of a pervasive fracture system is not only the consequence of various formation mechanisms but also intrinsic to quasi-continuous accumulation reservoirs.
文摘Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ordovician faunas of J(a|¨)mtland have developed against a background of intense and rapid global climate change.The faunas are present approximately in the middle of the Kyrk(?)s Quartzite in the east and occur in the uppermost Kogsta Siltstone in the west. Changes in faunas and depositional environments provide regional evidence of these global cooling and regressive events.The faunas occur in shale and siltstone facies and are used to effect
文摘Based on analysisof karst fracture-vuggy filling mineralogy and geochemical fluorite in hercynian, this paper make further research about formation and significance of fluorite in central uplift of Tarim Basin. It is point out that the development of hercynian fracture-vuggy and filling succession of fracture-cave mineral was under the background of the mingling of low-temperature magma hydrotherm and the brine of upper strata. There are overlap or associate relations between generate of fluorite and buried dissolution or oil-gas migration. It was volume decreased 26.4% after calcite metasomatic by fluorite, this reaction made fluorite engender plentiful intergranular space. It’s created appreciable reservoir space. At same time, hydrotherm carried by fluorite generating could erode adjacent rock though fracture or fissure, forming irregular fracture-cave system, and also accompanied with hydrocarbon migration. The time of hydrocarbon migration and accumulation happened in late hercynian-indosinian is inosculates with the sedimentation time such as fluorite and several hydrothermal mineral.
基金Supported by Twelfth Five-Year Major National Science and Technology Projects of China (No.011ZX05004-004)
文摘Based on the analysis of the morphology, order, cathodoluminescence and microelement of the calcite crystals in the pores of Upper Ordovician limestone in Tazhong oilfield of Tarim Basin, this paper suggest that the calcite crystals can divided 11 kinds of cements into three stages, and confirms their cementation sequence characteristics and formation environment. First stage of the cementation occurred on the bottom of the diagenetic environment, the product of which mainly are microcrystalline, fine shape, radiation fibrous, fasciculation, radiation axis shape calcites and a ball-like aragonite, whose filling pore is 0%–30%; the second one occurred in the atmospheric fresh water environment, with main cement types of crescent or pendulous shape, vadose silt, hyperplasia of coaxial, the filling pore of which is 5%–100%; the third one occurred in a burial environment, the crystals of which are bright and thick, mainly coarse sparry and poikilitic calcite, with filling pore of 5%–5%. In this paper, influence from each stage of cementation on porosity is analyzed, and pore evolution is established.
基金major science and technology project of PetroChina“Research and application of key technologies for sustainable,effective and stable production exploration and development of North China Oilfield(2017e-15)”。
文摘The buried hill in the Jizhong depression contains abundant petroleum reserves and are important production areas.The Ordovician buried hill has restricted the discovery of new oil and gas exploration targets because of its strong reservoir heterogeneity and complex reservoir-controlling factors.Based on a large volume of core,thin section,logging,seismic,and geochemical data and numerous geological analyses,the reservoir-forming conditions and modes were systematically analyzed to guide the exploration and achieve important breakthroughs in the Yangshuiwu and Wen an slope buried hills.The study revealed that three sets of source rocks of the third and fourth members of the Shahejie Formation from the Paleogene and Carboniferous-Permian were developed in the Jizhong depression,providing sufficient material basis for the formation of buried hill oil and gas reservoirs.The reservoir control mechanism involving the three major factors of“cloud-karst-fault”was clarified,and karst cave,fracture fissure-pore,and cloud pore type reservoir models were established,thereby expanding the exploration potential.Controlled by the superposition of multi-stage tectonic processes during the Indosinian,Yanshanian,and Himalayan,two genetic buried hill trap types of uplift-depression and depression-uplift were formed.Based on the analysis of reservoir-forming factors of the Ordovician buried hill,three buried hill oil and gas reservoir-forming models were identified:low-level tectonic-lithologic composite quasi-layered buried hill,medium-level paleo-storage paleo-block buried hill,and high-level paleo-storage new-block buried hill.Comprehensive evaluations indicate that the reservoir-forming conditions of the low-level tectonic-lithologic composite quasi-layered buried hill in the northern portion of the Jizhong depression are the most favorable and that the Sicundian and Xinzhen buried hills are favorable areas for future exploration.
