A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outc...A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outcrops and drilling data,its isochronous stratigraphic framework was built according to a particular graptolite zone and an important marker bed,and lithofacies,paleontology,calcareous content,well logging,geochemistry and other geologic information were combined to describe the sedimentary microfacies of Longmaxi Formation and its stratigraphic sequence,sedimentary evolution process and high quality shale distribution features as follows:①with regional diachronism of the top and the bottom,the Longmaxi Formation is divided into two third-order sequences(SQ1 and SQ2),of which SQ1 is mainly an abyssal sedimentary assemblage deposited in the marine transgression period,and SQ2 is a bathyal to shallow sea sedimentary assemblage deposited in the marine regression period;②there are eight microfacies such as deep calcareous shelf and deep argillaceous shelf in this formation and the organic-rich shale was mainly deposited in the deep water area of SQ1;and③from SQ1 to SQ2,the depocenter moved from the depression area in southern-eastern to northern Sichuan Basin,but the central Sichuan uplift remained an underwater one.It is concluded from this study that:①shale gas production layers were mainly deposited in SQ1,the southern-eastern depression area was the depocenter in SQ1 and a shale gas enrichment area;and②black shale in northern Sichuan was deposited in late SQ2,with limited distribution and relatively insufficient exploration potential,but the potential of shale gas exploration in western Hubei area is between southern-eastern and northern Sichuan Basin.展开更多
基金State Key Basic Research and Development Program(No.973 Program)ProjectSpecial and Significant Project of Na-tional Key Science and Technology(No.2011ZX05018-001)National Strategic Petroleum Resources Area Selection and Evaluation Project(No.2009GYXQ15-01).
文摘A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas.On the basis of outcrops and drilling data,its isochronous stratigraphic framework was built according to a particular graptolite zone and an important marker bed,and lithofacies,paleontology,calcareous content,well logging,geochemistry and other geologic information were combined to describe the sedimentary microfacies of Longmaxi Formation and its stratigraphic sequence,sedimentary evolution process and high quality shale distribution features as follows:①with regional diachronism of the top and the bottom,the Longmaxi Formation is divided into two third-order sequences(SQ1 and SQ2),of which SQ1 is mainly an abyssal sedimentary assemblage deposited in the marine transgression period,and SQ2 is a bathyal to shallow sea sedimentary assemblage deposited in the marine regression period;②there are eight microfacies such as deep calcareous shelf and deep argillaceous shelf in this formation and the organic-rich shale was mainly deposited in the deep water area of SQ1;and③from SQ1 to SQ2,the depocenter moved from the depression area in southern-eastern to northern Sichuan Basin,but the central Sichuan uplift remained an underwater one.It is concluded from this study that:①shale gas production layers were mainly deposited in SQ1,the southern-eastern depression area was the depocenter in SQ1 and a shale gas enrichment area;and②black shale in northern Sichuan was deposited in late SQ2,with limited distribution and relatively insufficient exploration potential,but the potential of shale gas exploration in western Hubei area is between southern-eastern and northern Sichuan Basin.
