Based on the latest drilling core, thin section, 3D seismic, well logging data as well as exploration results, the sequence stratigraphy and sedimentary microfacies of the Middle-Lower Ordovician carbonates in Gucheng...Based on the latest drilling core, thin section, 3D seismic, well logging data as well as exploration results, the sequence stratigraphy and sedimentary microfacies of the Middle-Lower Ordovician carbonates in Gucheng area, and their controlling effects on the development of reservoir were examined by the theories and methods of fine carbonate sedimentology.The results show that the Middle-Lower Ordovician in Gucheng area is a set of typical carbonate ramp deposits, which can be divided into 10 microfacies in 4 subfacies as follows: back ramp, inner shallow ramp, outer shallow ramp, and deep ramp. The back ramp subfacies consists of muddy-dolomitic flat and dolomitic lagoon microfacies;it is dominated by lamellar micrite dolomite tight in lithology. The inner shallow ramp subfacies includes dolomitic shoal and dolomitic flat in shoal top and dolomitic flat between shoals microfacies;it is mainly composed of crystal dolomite with metasomatic residual structure, as well as abundant karst vugs and intercrystalline pores. The crystal dolomite has an average porosity of 4.36%. The outer ramp subfacies includes medium-high and low energy grain shoal and inter-shoal microfacies;it is dominated by sandy limestone,oolitic limestone, and micrite limestone with few pores. The deep ramp subfacies is dominated by low-energy argillaceous deposits, with local presences of storm shoal microfacies. The Lower-Middle Ordovician has six third-order sequences from bottom to top, among which sequence(SQ3) represents the third member of Yingying Formation. The main reservoir has three fourth-order high-frequency sequences. Apparently, the favorable reservoir in the study area is jointly controlled by sedimentary microfacies and high frequency sequence in the carbonate ramp. The former controls the primary pore structure, and the latter controls the intensities of karstification exposure and dolomitization in the penecontemporaneous period. The dolomitic shoals and top dolomitic flats of different stages, superimposed and connected into favorable reservoirs of considerable scale like "platform margin", are favorable exploration facies in the carbonate ramp.展开更多
Based on seismic, drilling data and experimental analysis, the characteristics and main controlling factors of shoal dolomite gas reservoir in the third member of Ordovician Yingshan Formation of Gucheng area, Tarim b...Based on seismic, drilling data and experimental analysis, the characteristics and main controlling factors of shoal dolomite gas reservoir in the third member of Ordovician Yingshan Formation of Gucheng area, Tarim basin were examined.The study shows that the dolomite gas reservoir in Gucheng area is lithologic gas reservoir controlled by shoal and fault jointly,and its formation is mainly attributed to the following factors:(1) The continuously developing paleotectonic structure has been in the direction of gas migration and accumulation;(2) The large area of medium-high energy grain bank deposited in gentle slope environment is the material basis for the formation of dolomite reservoir;(3) Atmospheric water leaching and dolomitization and fluid dissolution in fault zone are the key factors for the formation of high-quality dolomite reservoir;(4)The natural gas comes from cracking of the ancient oil reservoir and hydrocarbon generation of dispersed organic matter in source rocks, and the NNE-trending strike-slip fault is the dominant channel for vertical migration of natural gas;(5) Limestone cap rocks in the first and second members of Yingshan Formation provide direct sealing for the formation of gas reservoir there. On the basis of comprehensive analysis, it is pointed out that the Gucheng area has three grain shoal zones in the third member of Yingshan Formation in nearly S-N direction, which together with seven strike-slip fault zones in NNE direction control the development of shoal dolomite gas reservoir.展开更多
Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the ...Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined.The Cambrian platform margin mound-shoal complex is divided into mound base,mound core,mound front,mound back and mound flat microfacies,which are composed of dolomites of seven textures with facies indication.The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed,and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established:namely,the first stage of gentle slope symmetric accretion type,the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type.Their microfacies are respectively characterized by-mound base-mound back+(small)mound core+mound front-mound flat"symmetric vertical accretion structure,"mound base-(large)mound core+mound front-mound flat"asymmetric vertical accretion structure,"mound base-(small)mound core+mound front-mound flat"asymmetric lateral progradation structure.With most developed favorable reservoir facies belt,the steep slope asymmetric accretion type mound-shoal complex with the characteristics of"large mound and large shoal"is the exploration target for oil and gas reservoir.展开更多
Lower Paleozoic carbonate rocks are an important exploration area in craton area of the Tarim Basin,with the proven oil and gas reserves of more than 2.2×10^8 t,but no large-scale discovery has been made in the G...Lower Paleozoic carbonate rocks are an important exploration area in craton area of the Tarim Basin,with the proven oil and gas reserves of more than 2.2×10^8 t,but no large-scale discovery has been made in the Gucheng area so far.The key issues restricting exploration are that the source rock,reservoir scale and law of oil and gas enrichment are unclear.By systematically examining the petroleum geological conditions of Lower Paleozoic carbonate rocks,the following findings are reached:(1)Source rocks of slope-basin facies developed in Cambrian-Lower Ordovician in the Gucheng area.(2)The dolomitized beach in the lower part of Ordovician Yingshan Formation has large-scale reservoirs,good reservoir-cap assemblage and developed gas source faults,and is an important field for increasing reserves and production in the near future;hydrocarbon enrichment is controlled by reservoir and gas source faults,and the central dolomitized beach zone is the main exploration area.(3)The Cambrian platform margin reef beach,large in scale,good in physical properties and close to source rocks,has the possibility to form monolithic gas field;the caprock and preservation conditions are the key factors for hydrocarbon enrichment;the northern part of the phasesⅠandⅡplatform margin reefs has better sealing conditions,and is the main direction of next exploration.(4)Limestone fault solution reservoirs in the upper part of Ordovician Yingshan Formation,controlled by faults and small in scale,but good in reservoir-cap combination,worth exploring.(5)The granular limestone beach of Ordovician Yijianfang Formation is well developed and gas-bearing,but short in exposure dissolution time,and the reservoirs are strongly heterogeneous,and are a potential exploration field.展开更多
基金Supported by the National Natural Science Foundation of China(42072171 and 41772103)National Oil and Gas Major Science and Technology Project(2016ZX05007-002)China National Petroleum Corporation Major Science and Technology Project(1016E-0204)。
文摘Based on the latest drilling core, thin section, 3D seismic, well logging data as well as exploration results, the sequence stratigraphy and sedimentary microfacies of the Middle-Lower Ordovician carbonates in Gucheng area, and their controlling effects on the development of reservoir were examined by the theories and methods of fine carbonate sedimentology.The results show that the Middle-Lower Ordovician in Gucheng area is a set of typical carbonate ramp deposits, which can be divided into 10 microfacies in 4 subfacies as follows: back ramp, inner shallow ramp, outer shallow ramp, and deep ramp. The back ramp subfacies consists of muddy-dolomitic flat and dolomitic lagoon microfacies;it is dominated by lamellar micrite dolomite tight in lithology. The inner shallow ramp subfacies includes dolomitic shoal and dolomitic flat in shoal top and dolomitic flat between shoals microfacies;it is mainly composed of crystal dolomite with metasomatic residual structure, as well as abundant karst vugs and intercrystalline pores. The crystal dolomite has an average porosity of 4.36%. The outer ramp subfacies includes medium-high and low energy grain shoal and inter-shoal microfacies;it is dominated by sandy limestone,oolitic limestone, and micrite limestone with few pores. The deep ramp subfacies is dominated by low-energy argillaceous deposits, with local presences of storm shoal microfacies. The Lower-Middle Ordovician has six third-order sequences from bottom to top, among which sequence(SQ3) represents the third member of Yingying Formation. The main reservoir has three fourth-order high-frequency sequences. Apparently, the favorable reservoir in the study area is jointly controlled by sedimentary microfacies and high frequency sequence in the carbonate ramp. The former controls the primary pore structure, and the latter controls the intensities of karstification exposure and dolomitization in the penecontemporaneous period. The dolomitic shoals and top dolomitic flats of different stages, superimposed and connected into favorable reservoirs of considerable scale like "platform margin", are favorable exploration facies in the carbonate ramp.
基金Supported by the National Natural Science Foundation of China(Grant No.U20A201009 and 41972157)PetroChina Science and Technology Major Project(Grant No.2016E-0204)。
文摘Based on seismic, drilling data and experimental analysis, the characteristics and main controlling factors of shoal dolomite gas reservoir in the third member of Ordovician Yingshan Formation of Gucheng area, Tarim basin were examined.The study shows that the dolomite gas reservoir in Gucheng area is lithologic gas reservoir controlled by shoal and fault jointly,and its formation is mainly attributed to the following factors:(1) The continuously developing paleotectonic structure has been in the direction of gas migration and accumulation;(2) The large area of medium-high energy grain bank deposited in gentle slope environment is the material basis for the formation of dolomite reservoir;(3) Atmospheric water leaching and dolomitization and fluid dissolution in fault zone are the key factors for the formation of high-quality dolomite reservoir;(4)The natural gas comes from cracking of the ancient oil reservoir and hydrocarbon generation of dispersed organic matter in source rocks, and the NNE-trending strike-slip fault is the dominant channel for vertical migration of natural gas;(5) Limestone cap rocks in the first and second members of Yingshan Formation provide direct sealing for the formation of gas reservoir there. On the basis of comprehensive analysis, it is pointed out that the Gucheng area has three grain shoal zones in the third member of Yingshan Formation in nearly S-N direction, which together with seven strike-slip fault zones in NNE direction control the development of shoal dolomite gas reservoir.
基金Supported by the National Natural Science Foundation of China(41772103)China National Science and Technology Major Project(2016ZX05007-002)Petrochina Science and Technology Major Project(2016E-0204)。
文摘Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined.The Cambrian platform margin mound-shoal complex is divided into mound base,mound core,mound front,mound back and mound flat microfacies,which are composed of dolomites of seven textures with facies indication.The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed,and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established:namely,the first stage of gentle slope symmetric accretion type,the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type.Their microfacies are respectively characterized by-mound base-mound back+(small)mound core+mound front-mound flat"symmetric vertical accretion structure,"mound base-(large)mound core+mound front-mound flat"asymmetric vertical accretion structure,"mound base-(small)mound core+mound front-mound flat"asymmetric lateral progradation structure.With most developed favorable reservoir facies belt,the steep slope asymmetric accretion type mound-shoal complex with the characteristics of"large mound and large shoal"is the exploration target for oil and gas reservoir.
基金Supported by the China National Science and Technology Major Project(2016E-0204).
文摘Lower Paleozoic carbonate rocks are an important exploration area in craton area of the Tarim Basin,with the proven oil and gas reserves of more than 2.2×10^8 t,but no large-scale discovery has been made in the Gucheng area so far.The key issues restricting exploration are that the source rock,reservoir scale and law of oil and gas enrichment are unclear.By systematically examining the petroleum geological conditions of Lower Paleozoic carbonate rocks,the following findings are reached:(1)Source rocks of slope-basin facies developed in Cambrian-Lower Ordovician in the Gucheng area.(2)The dolomitized beach in the lower part of Ordovician Yingshan Formation has large-scale reservoirs,good reservoir-cap assemblage and developed gas source faults,and is an important field for increasing reserves and production in the near future;hydrocarbon enrichment is controlled by reservoir and gas source faults,and the central dolomitized beach zone is the main exploration area.(3)The Cambrian platform margin reef beach,large in scale,good in physical properties and close to source rocks,has the possibility to form monolithic gas field;the caprock and preservation conditions are the key factors for hydrocarbon enrichment;the northern part of the phasesⅠandⅡplatform margin reefs has better sealing conditions,and is the main direction of next exploration.(4)Limestone fault solution reservoirs in the upper part of Ordovician Yingshan Formation,controlled by faults and small in scale,but good in reservoir-cap combination,worth exploring.(5)The granular limestone beach of Ordovician Yijianfang Formation is well developed and gas-bearing,but short in exposure dissolution time,and the reservoirs are strongly heterogeneous,and are a potential exploration field.
