Mechanism of sand-control and quantitative evaluation of reservoir effectiveness in the northern steep slope of Chengnan area in the Zhanhua Sag

Fans are widespread in the Shahejie Formation in the northern steep slope of Chengnan area in the Zhanhua Sag. They are distributed in a complicated pattern. It is difficult to make stratigraphic correlation. Reservoir heterogeneity is strong. As a result, an effective method for the quantitative evaluation of reservoir is demanded. We studied the mechanism of sand-control, and determined the vertical and horizontal evolution rules of reservoirs by the quantitative calculation of slope angle. The distribution of paleo sources matches well with paleotopography. Higher boundary fault angle led to a wider fan root and narrower middle-fan. The distribution of the sand body can be summarized as the matching of the channel and fan, the matching of a large channel and large fan, sufficient supply, continuous development, and vertically backward fan. We found some effective reservoirs by using geophysical and geological statistics. Sand group no. 3 in the lower section of the third member of Shahejie Formation close to wells Binggu604 and Yi159 has a tight fan root, which impedes lateral hydrocarbon migration. Middle fan facies around wells Yi109 and Yi104-4 work as effective reservoirs for either oil or dry gas, and are favorable exploration targets. The area around well Yi107-1 is a fan edge, where few effective reservoirs developed.