The Characteristic Of Sedimentary Filling Evolution And The Control Function Of Synsedimentary Faulting Of The Palaeogene Strata In Liaozhong Sag

Liaozhong sag is in the central region of Liao dongwan depression and have thick sedimentary formation in Paleogene,which is the primary exploration potential region.Lots of structural traps have been found with exploration more and more mature in recent years,the exploration direction of oil and gas gradually transfer to the subtle reservoirs.But the single geophysical characteristics is can not distinguish rich or poor sand content in depositional system effectivelly throughing lots of well drillings.So this paper applying sequence stratigraphy,tectonic geology theories for guidelines,by identifying the control function of activities synsedimentary faulting to sedimentary system filling in the sag to predict sand enrichment trend,which then providing the most favorable reference to lithological reservoir exploration.This paper by using the latest sequence stratigraphy theory to divide the Paleogene formation of the LiaoZhong sag into ten third-order sequences. In the high-resolution data of Dongying group throughing identify sub-regression interface divide it into six fouth-order sequences.The high resolutional sequence stratigraphic divide scheme was established in the region,the stratigraphic framework precision was improved,which is having important theoretical significance to identify sand enrichment systerm.Combined with log facies,core and seismic facies identify the fan delta, meandering river-braided delta,littoral and shallow lake-beach and bar, turbidite fan and deep-half a deep lake sedimentary system in sequence stratigraphic framework. Steep slope and gentle slope belt is mainly by fan delta aggradation in the early stage of shahejie forms;Gentle slope belt is mainly by fan- braided delta and beach bar retrogradation;Steep slope belt is also by fan delta aggradation,but in the middle of the sag developed lots of turbidite system with waterway supply during the late stage of shahejie to early stage of Dongying forms;Gentle slope belt is mainly by meandering river-braided delta progradation,steep slope belt is mainly by fan-braided delta progradation, in the middle of the sag developed meandering river delta from the axis, massive slump turbidite body developed from delta front during the late stage of Dongying forms. By analysis the characteristics of synsedimentary faulting distribution and activity, basin tectonic subsidence and evoluational process shows that there is obvious control function to the provenance, water system and accommodation space change throughing the alignment activities differences of synsedimentary faulting.And the sedimentary system filled position and pattern was affected by this features.The research shows that gentle slope fault adjusting belt,slope-break zones,reverse fault combination belt due to synsedimentary faulting activity; steep slope belt fault slope-break zones; circumferenially goose fold after take in the middle of the sag. All is sand enrichment positions.which is the favorable positions for lithologic reservoir.Based on the comprehensive analysis and combing reservoir features present that the fault adjustment belt of LD16-3-1 well southwest gentle slope belt in the southern, reverse fault zone north of LD16-1-1 well northeast and extrusion reversal belt of LD12-1 area are the favorable target zones. And for provides favorable reference for the next step exploration.