Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the ...Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the source,genesis,and distribution of different types of oils in the Mahu large oil province of the Junggar Basin are investigated.Four sets of potential source rocks are developed in the Mahu Sag.Specifically,the source rocks of the Permian Fengcheng Formation have the highest hydrocarbon generation potential and contain mainly TypesⅡandⅠorganic matters,with a high oil generation capacity.In contrast,the source rocks in other formations exhibit lower hydrocarbon generation potential and contain mainly TypeⅢorganic matter,with dominant gas generation.Oils in the Mahu Sag can be classified as three types:A,B and C,which display ascending,mountainous and descending C_(20)-C_(21)-C_(23)tricyclic terpenes abundance patterns in sequence,and gradually increasing relative content of tricyclic terpenes and sterane isomerization parameters,indicating an increasing oil maturity.Different types of oils are distributed spatially in an obviously orderly manner:Type A oil is close to the edge of the sag,Type C oil is concentrated in the center of the sag,and Type B oil lies in the slope area between Type A and Type C.The results of oil-source correlation and thermal simulation experiments show that the three types of oils come from the source rocks of the Fengcheng Formation at different thermal evolution stages.This new understanding of the differential genesis of oils in the Mahu Sag reasonably explains the source,distribution,and genetic mechanism of the three types of oils.The study results are of important guidance for the comprehensive and three-dimensional oil exploration,the identification of oil distribution in the total petroleum system,and the prediction of favorable exploration areas in the Mahu Sag.展开更多
Crude oil has been discovered in the Paleogene and Neogene units of the Weixinan Sag in the Beibu Gulf Basin.To determine the source and accumulation mode of this crude oil,12 crude oil samples and 27 source rock samp...Crude oil has been discovered in the Paleogene and Neogene units of the Weixinan Sag in the Beibu Gulf Basin.To determine the source and accumulation mode of this crude oil,12 crude oil samples and 27 source rock samples were collected and an extensive organic geochemical analysis was conducted on them.Based on the geological conditions and the analytical results,the types,origins and accumulation patterns of crude oil in the study area were elucidated.Except for a shallowly-buried and biodegraded crude oil deposit in Neogene rocks,the crude oil samples in the study area were normal.All of the crude oils were derived from lacustrine source rocks.According to biomarker compositions,the crude oils could be divided into two families,A and B,distinctions that were reinforced by differences in carbon isotope composition and spatial distribution.Oil-source correlation analysis based on biomarkers revealed that Family A oils were derived from the mature oil shale at the bottom of the second member of the Liushagang Formation,while the Family B oils formed in the mature shale of the Liushagang Formation.The Family A oils,generated by oil shale,mainly migrated laterally along sand bodies and were then redistributed in adjacent reservoirs above and below the oil shale layer,as well as in shallow layers at high structural positions,occupying a wide distribution range.The Family B oils were generated by other shale units before migrating vertically along faults to form reservoirs nearby,resulting in a narrow distribution range.展开更多
文摘Based on the geological and geochemical analysis of potential source rocks in different formations and the classification of crude oil types,combined with the hydrocarbon generation thermal simulation experiments,the source,genesis,and distribution of different types of oils in the Mahu large oil province of the Junggar Basin are investigated.Four sets of potential source rocks are developed in the Mahu Sag.Specifically,the source rocks of the Permian Fengcheng Formation have the highest hydrocarbon generation potential and contain mainly TypesⅡandⅠorganic matters,with a high oil generation capacity.In contrast,the source rocks in other formations exhibit lower hydrocarbon generation potential and contain mainly TypeⅢorganic matter,with dominant gas generation.Oils in the Mahu Sag can be classified as three types:A,B and C,which display ascending,mountainous and descending C_(20)-C_(21)-C_(23)tricyclic terpenes abundance patterns in sequence,and gradually increasing relative content of tricyclic terpenes and sterane isomerization parameters,indicating an increasing oil maturity.Different types of oils are distributed spatially in an obviously orderly manner:Type A oil is close to the edge of the sag,Type C oil is concentrated in the center of the sag,and Type B oil lies in the slope area between Type A and Type C.The results of oil-source correlation and thermal simulation experiments show that the three types of oils come from the source rocks of the Fengcheng Formation at different thermal evolution stages.This new understanding of the differential genesis of oils in the Mahu Sag reasonably explains the source,distribution,and genetic mechanism of the three types of oils.The study results are of important guidance for the comprehensive and three-dimensional oil exploration,the identification of oil distribution in the total petroleum system,and the prediction of favorable exploration areas in the Mahu Sag.
文摘Crude oil has been discovered in the Paleogene and Neogene units of the Weixinan Sag in the Beibu Gulf Basin.To determine the source and accumulation mode of this crude oil,12 crude oil samples and 27 source rock samples were collected and an extensive organic geochemical analysis was conducted on them.Based on the geological conditions and the analytical results,the types,origins and accumulation patterns of crude oil in the study area were elucidated.Except for a shallowly-buried and biodegraded crude oil deposit in Neogene rocks,the crude oil samples in the study area were normal.All of the crude oils were derived from lacustrine source rocks.According to biomarker compositions,the crude oils could be divided into two families,A and B,distinctions that were reinforced by differences in carbon isotope composition and spatial distribution.Oil-source correlation analysis based on biomarkers revealed that Family A oils were derived from the mature oil shale at the bottom of the second member of the Liushagang Formation,while the Family B oils formed in the mature shale of the Liushagang Formation.The Family A oils,generated by oil shale,mainly migrated laterally along sand bodies and were then redistributed in adjacent reservoirs above and below the oil shale layer,as well as in shallow layers at high structural positions,occupying a wide distribution range.The Family B oils were generated by other shale units before migrating vertically along faults to form reservoirs nearby,resulting in a narrow distribution range.
