The mechanism and regularity of hydrocarbon accumulation of the lithologic reservoirs in the slope region of Qikou Sag

Qikou Sag is one of the important oil rich sags in the Bohai Bay Basin,with slope region as the dominant area of lithologic stratigraphic reservoirs.The slope region can be further divided into four categories which are step faulting slope,multi-step flexure slope,rotary tilting slope and simple slope according to the structural characteristics of lake basin.Through study on slope characteristics,sand control mechanism and hydrocarbon transport system,models of hydrocarbon accumulation were set up for different categories of slopes,suggesting that the lithologic stratigraphic reservoirs in the slopes have the regularity of oil higher than gas,compound superimposed and contiguous reservoirs,and concentration of favorable facies.The study result had effectively guided oil and gas exploration in slope regions and discovered sizable reserves such as in Chenghai fault ramp and Qibei slope.