The Development And Distribution Characteristics Of Bank Of Reservoir Changxing Formation In Yuanba Area

Carbonate bank is a good oil and gas reservoir, it is primarily a special form ofcarbonate sedimentary bodies piled up by the bioclastic,calcarenite and oolitic,alsoimportant type of oil and gas deposits of carbonate reservoir and exploration prospectsare enormous. Carbonate rocks buried deeply in Sichuan Basin, which led to the poorquality of seismic data and multiple solutions. It is difficult to identify and forecast,and a kind of oil and gas reservoir that has difficulty in exploration.Drilling sequence is divided on the basis of classical sequence stratigraphytheory and according to the latest sequence stratigraphy standardization concept（Catuneanu，2009）, four sedimentary origin types of systems tracts LST, TST, HST,FSST are as as the basic unit of analysis and calibrate the drilling sequence results tothe seismic profiles.The bank reservoir is Identified on the basis of recovering thebasin prototype and sequence stratigraphic framework combined with seismic faciesanalysis.The law of development and the distribution characteristics each period ofthe bank reservoir are studied on the basis of ancient geomorphology and sedimentaryfacies. There has some progress and conclusion as follows:(1)Changxing Formation concludes five deposition cycles (or forth sequence),five systems tracts. It includes a third sequence (SQ1) in lower part and of anincomplete tiird sequence (SQ2)in the upper part.(2) The seismic response of bank reservoir is the weak-strong amplitude andhummocky overlay closely, the trough is top surface and the peak is bottom.Also withthe following characteristics:①General low-amplitude convex mound-like shape;②Hummocky overlay closely inside and lateral accretion to both sides;③Untidywaveform and phase axis is not smooth, discontinuous;④The amplitude is thestrongest on zhe top and weaken to both sides;⑤The bank can develop on the top ofzhe reef,in zhe back of zhe reef and in front of zhe reef.(3)The development of bank continues to migrate on the basis of bank planedistribution law. Any time bank is developing only development location is migrating.In lowstand systems tract, bank are well developed in platform margin.Inearly transgressive systems tract the bank migrates to land. And then from the latetransgressive systems tract to highstand systems tracts and forced regressive systemstract the bank migrates to basin In upper lowstand systems tract, the rate of increase ofaccommodation space equal to the rate of deposition of sedimentary tidal flatdolomite with the rise of sea-level. Therefore, the tidal flat dolomite reservoircontinued to develop. At this time bank can developd in lagoon behind zhe barrierreef，but not big.