Carboniferous-Permian Geological Architecture Of The Shawan Sag And Its Adjacent Area, Junggar Basin

Shawan sag is located in the southwest of Junggar Basin.It is the hydrocarbon source center of Permian.This paper studies the geological architecture and the formation evolution of Shawan sag,by using fault-related folding theory,petroleum geological comprehensive research method and balanced cross section restoration technique,combined seismic profiles,well logging,well drilling,and core data,set up integrated formation system of Permo-Carboniferous in Shawan sag,identify regional unconformities,divide tectono-stratigraphic sequence.Secondly,this paper studies the fault system of Shawan sag,by tracking each series of strata.And combined with the characteristics of unconformity and fault system,this paper divided the geological architecture of Permo-Carboniferous,by the remnant isopach of Carboniferous-Permian.Finally,the influence of tectonic movement about geological architecture is discussed by using tectonic evolution profile.In the process,the following main achievements are achieved:?1?Since the Late Carboniferous,seven important regional stratigraphic unconformities have been developed in the Shawan sag and its adjacent areas.These are the unconformities between the Palaeogene and the Cretaceous;the Cretaceous and the Jurassic;the Jurassic and the Triassic;the Triassic and the Upper Permian;the Upper Permian and the Middle Permian;the Middle Permian and the Lower Permian;the Lower Permian and the Upper Carboniferous respectively.Accordingly,the strata are divided into seven tectonic-stratigraphic sequence from bottom to top.Among them,Carboniferous-Permian strata are divided into three tectonic sequences,including the Upper Carboniferous-Lower Permian sequence,the Middle Permian sequence and the Upper Permian sequence.?2?The seventeen Carboniferous-Permian faults are identified in Shawan sag and its adjacent area.Among them,there are seven normal faults,four reverse faults,and six vertical faults.The map-view is distributed along NW-SE and SN.In addition,there are three combinations,shaped like"pectination","backward Chinese number eight"and"an 8",and there are two styles of parallel domino and“Y“in the section.Late Carboniferous-Permian in the Shawan sag and its adjacent areas have experienced three evolutionary stages of the Late Carboniferous extension,the Early Permian extension and the Middle Permian compression.?3?The isopach of Carboniferous-Permian,regional unconformity distribution and the map-view characteristics of fault system are used to divide the geological architecture in Shawan sag and its adjacent.The Upper Carboniferous is divided into six highs and five sags in Shawan sag,the Lower Permian is divided into two sags and one highs,the Middle-Upper Permian is divided into one sag.?4?There is a paleo-uplift between the Shawan sag and the Well Pen-1 West sag,the map-view is NW-SE.The shape of the paleo-uplift is widen to the uplift sides of the two sides and narrow to the inter of the sag.?5?The Shawan sag and its adjacent areas mainly experienced six tectonic evolution,respectively:the Late Carboniferous-Early Permian?C₂-P₁?extensional faulted basin stage,Middle-Late Permian?P₂-P₃?extrusion inversion stage,Triassic-early Jurassic?T-J₁?inter-continental depression,Middle-Late Jurassic?J2-J3?transpression basin stage,Cretaceous-Paleogene?K-E?terrestrial depression stage and Neogene-Quaternary?N-Q?terrestrial foreland basin stage.