The Researches Of Depositional System And Formation Factors Of Reservoir In The Middle Depression Of Wuliyastai Depression, Erlian Basin

The resource increased in a depression of ErLian basin is greater than those discoveredoil&gas depression in fact. The southern depression of Wuliyastai depression, which has the samegeology buildup as center depression, gets a big discovery in the lithologic trap, it is the mostimportant field to enlarging the exploration outcome. Based on the limited drilling data and thecomplex reflections on seismic profile, the equitime frames were set up by using the theory ofsequence stratigraphy;in these frames, the condition of reservoir such as the initial rock of gasand oil, reservoir and non-structure trap were analyzed. Then the pattern of reservoir was made.Predication for voluble area and voluble drilling target was made based on the analysis of thedrilled wells, success or failure.Generally, on the upper part of the center depression, faults are not rich. It's a structurelooks like a winnowing fan, breaking in west and overlapping in east, it can be divided into acticregion, middle low-laying land and ramp region, the last two are bigger than first. The shortage offaults caused the lack of big structure trap. Lithologic traps were well developed because of thebig broad slop.There are 12th sequences and 11 pluvial planes from Jurassic system to Tengyi zone.Mesozoic was divided into 11 middle period basal level cycles, or 11 third sequences. Thereservoir rock has three types: deltaic fan, subsea apron and turbidite fan. 4 middle period cyclesdevelop in Aershan and Tenyixia with 33 lithologic trap in it. A new deposit pattern described as atypical half graben was set up after core research, sequence stratigraphy and deposit systemanalyze. The provenances of the depression come from gentle slope more than steep slope.Descriptions and evaluations were made to the formation condition of reservoir such assource rock, reservoir rock and lithologic traps in middle low-laying land. Aershan and Tenyiwere confirmed have the valid source rock and reservoir rock. The generation of the low-layingland is 5×10~8t, the accumulation is 1-1.4×10~8t. The features of the middle low-laying land areshort of faults, thin reservoir bed, limited distribution range and closed oil translate distance. Thecharacters of the reservoir rock are middle –low porosity and low permeability, and it is theoriginal place production. Aershan and Tenyi are the most important target layer of exploration inthis area. The pattern of reservoir formation is set up on the generalization of all the factorsaffecting the formation. There is a huge slope at the east of middle law-laying land and less offaults, it is good for develop lithologic trap. Many fans scatters at the far end of the slope, theylocated in mature and high produced generating rock, and got plenty resource;Lithologic traps,above of tectonic setting, will become the main area of exploration in low-laying land.