Abstract:

Gao No.81 Block in Gaosheng Oilfield of Liaohe basin is a monocline structure plunging towards east, and its confined by faults in three directions of northwest, southwest and southeast. The oil bearing strata is upper sub-member of Es⁴ which is mainly composed of fan-delta sediments, and its lower part(Dujiatai oil layer) is fan-delta front subfacies, consisting of underwater distributary watercourse, river mouth sandbar and interfluve microfacies.Whereas its upper part is chiefly made up of profan-delta subfacies which is interbedded by underwater distributary watercourse and river mouth sandbar of fan-delta front subfacies occasionally. Dujiatai oil layer can be divided into three sand groups, located at the upper part of the layer, No.1sand group has great change laterally, whereas No. 2 and No.3 group(below No.1) which are quite stable. The physical property of reservoir of No.3 sand group is believed to be the best, and with the greatest effective thickness of oil bearing on the average and oil bearing area is relatively large too. Therefore, No.3 sand group has made greatest contributions to reserving oil and gas in Gao No.1 Block. No.2 sand group, with small effective thickness of oil bearing on the average, lowest oil-water interface and largest oil-bearing area, has made less contributions to reserving oil and gas on the average than No.3 sand group. No.1. group tends to pinch out towards the higher part of the structure and has made a little contribution to reserving oil and gas due to its highest oil-water interface and smallest oil-bearing area.

Key words: sedimentary facies, reservoir, Liaohe basin, Shahejie Formation