Research On Sequence Stratigraphy Of Denglouku Group In The South Of Xujiaweizi Depression

Guided by the theories of sequence stratigraphy, structural geology, sedimentology and petroleum geology, using seismic data, borehole log, logging curves and cores, the sequence framework have been built, detailed research and analysis on sedimentary evolution, discriminate distribution of sand body and lithologic trap, carry on analysis for source, reservoir and cap rock, at last explore the prospect areas.On the basis of carefully analyzing and referring the research fruits,by means of the study on the seismic data,logging data and drilling data, five sequence boundaries were recognized, from bottom to top which are SB 1 (the bottom of the Denglouku group), SB2(the bottom of the second member of the Denglouku group), SB3(the bottom of the third member of the Denglouku group), SB4(the bottom of the fourth member of the Denglouku group), SB5(the bottom of the Quantou group),especially Denglouku bottom interface is a important regional unconformity interface.The SB1 and SB5 are the boundaries of the super-sequence of Denglouku grouop, which can be further divided into four third-order squence (SQ1,SQ2,SQ3,SQ4).by analyzing the characteristics of the third -order sequence,it can be known that SQ1 and SQ2 develop the whole tracts,including lowstand system tracts(LST), transgressive system tracts(TST) and highstand system trarcts(HST). Based on the above cognitions, an isochronous stratigraphic framework of Denglouku group in studied area is built by means of tracing and correlating the well-tie seismic sections and of combining the well data and seismic data.Through the analysis of single well facies,thickness of formation,thickness of sand and the sand-formation ratio, this paper gave the sedimentary characteristics:the whole feature performance many sources and depocenters because of the cutting of the palaeohigh. SQ1 depositional systems are the fan dalta,braided river delta and the smaller lake; SQ2 period is still the braided river delta, performing the much larger lake; the character in SQ3 squence spreads some samller lake, the upheaval decreases; the SQ4 has long source and larger lakes.At last, the favorable exploration zones in the studied area are pointed out by making an integrative consideration of various ingredients such as source rocks, reservoir rocks, cap rocks and traps.