For a basin or sag with low exploration maturity,the understanding of its provenance system and clastic distribution system is the key to the analysis of its sedimentary framework and further influence the decision ma...For a basin or sag with low exploration maturity,the understanding of its provenance system and clastic distribution system is the key to the analysis of its sedimentary framework and further influence the decision making and deployment of exploration.This study analyzed the Jurassic provenance of the Sikeshu Sag based on the data from cores,well logging,and seismic survey.The analysis of seismic profile characteristics revealed that there is a remote possibility that the Chepaizi Uplift in the northern part serves as the main Jurassic provenance of the Sikeshu Sag.On the contrary,systematic indicative signs of provenance have developed in the study area,including west-to-east progradational reflection config-urations and composite mounded reflections that show bi-directional downlapping contact in both the south and north directions.These systematic indicative signs suggest that the denuded uplift area in the western part is the main Jurassic provenance in the study area.Controlled by the provenance in the western part,the study area shows an orderly distribution of paleosedimentary systems from west to east and from shallow to deep water.The paleosedimentary system mainly exhibits the following characteristics after undergoing later high-intensity transformation.(1)The western part is dominated by the subfacies of a braided river delta front and is composed of three microfacies including distributary channels,interdistributary bays,and sandbars;(2)The middle and eastern parts show a semi-deep lacustrine environment,where debris flow sedimentary systems of slumping origin or in deep can-yons,gullies and channels connected to the denudation area developed from west to east.These debris flow sedimentary systems jointly form the clastic sedimentary system under the control of western provenance.展开更多
The unconformity surface at the bottom of the Paleogene, located in the Sikeshu Sag of the Junggar Basin, Northwest China, is one of the most important hydrocarbon migration pathways and characterized by 3 layers of u...The unconformity surface at the bottom of the Paleogene, located in the Sikeshu Sag of the Junggar Basin, Northwest China, is one of the most important hydrocarbon migration pathways and characterized by 3 layers of upper coarse clastic rock, lower weathering crust and leached zone. The upper coarse clastic rock displays features of higher density, lower SDT and gamma-ray logging while the weathering crust in the lower part displays opposite features. The formation water is of NaHCO 3 type but at lower mineralization degree. The QGF indices are generally between 2.19 and 3.77 and the GOI parameters vary from 1% to 5%. From the southeast to the northwest of the sag, the content of saturated hydrocarbon increases from 30.81% to 53.74% while that of non-hydrocarbon and asphaltene decreases. The Pr/nC 17 decreases from 0.65 to 0.47 while the Ph/nC 18 decreases from 0.66 to 0.27, and the content of benzo[c] carbazole declines while the benzo[a] carbazole amount and (alkyl carbazole)/(alkyl+benzo carbazole) ratio both increase. These revealed that the hydrocarbons migrated from the sag to the ramp region along the unconformity surface.展开更多
The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservo...The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.展开更多
文摘For a basin or sag with low exploration maturity,the understanding of its provenance system and clastic distribution system is the key to the analysis of its sedimentary framework and further influence the decision making and deployment of exploration.This study analyzed the Jurassic provenance of the Sikeshu Sag based on the data from cores,well logging,and seismic survey.The analysis of seismic profile characteristics revealed that there is a remote possibility that the Chepaizi Uplift in the northern part serves as the main Jurassic provenance of the Sikeshu Sag.On the contrary,systematic indicative signs of provenance have developed in the study area,including west-to-east progradational reflection config-urations and composite mounded reflections that show bi-directional downlapping contact in both the south and north directions.These systematic indicative signs suggest that the denuded uplift area in the western part is the main Jurassic provenance in the study area.Controlled by the provenance in the western part,the study area shows an orderly distribution of paleosedimentary systems from west to east and from shallow to deep water.The paleosedimentary system mainly exhibits the following characteristics after undergoing later high-intensity transformation.(1)The western part is dominated by the subfacies of a braided river delta front and is composed of three microfacies including distributary channels,interdistributary bays,and sandbars;(2)The middle and eastern parts show a semi-deep lacustrine environment,where debris flow sedimentary systems of slumping origin or in deep can-yons,gullies and channels connected to the denudation area developed from west to east.These debris flow sedimentary systems jointly form the clastic sedimentary system under the control of western provenance.
基金financially supported jointly by the National Key Project of Science and Technology for Development of Large-size Oil & gas Fields and Coal-bed Gas (Grant No. 2008ZX05003-002)the State Key Laboratory of Petroleum Resources and Prospecting (No. prp2009-02)
文摘The unconformity surface at the bottom of the Paleogene, located in the Sikeshu Sag of the Junggar Basin, Northwest China, is one of the most important hydrocarbon migration pathways and characterized by 3 layers of upper coarse clastic rock, lower weathering crust and leached zone. The upper coarse clastic rock displays features of higher density, lower SDT and gamma-ray logging while the weathering crust in the lower part displays opposite features. The formation water is of NaHCO 3 type but at lower mineralization degree. The QGF indices are generally between 2.19 and 3.77 and the GOI parameters vary from 1% to 5%. From the southeast to the northwest of the sag, the content of saturated hydrocarbon increases from 30.81% to 53.74% while that of non-hydrocarbon and asphaltene decreases. The Pr/nC 17 decreases from 0.65 to 0.47 while the Ph/nC 18 decreases from 0.66 to 0.27, and the content of benzo[c] carbazole declines while the benzo[a] carbazole amount and (alkyl carbazole)/(alkyl+benzo carbazole) ratio both increase. These revealed that the hydrocarbons migrated from the sag to the ramp region along the unconformity surface.
基金Supported by PetroChina Science and Technology Development Project(2023ZZ0206,2021DJ0303,2021DJ0105,2021DJ0203)National Natural ScienceFoundation of China(U22B6002).
文摘The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.
