Favorable area prediction of tight sandstone: A case study of the He8 formation in the Kangning area, Eastern Ordos Basin, China

The reservoirs of the Lower Permian He8 formation are typically tight sandstones, which have geologic features such as rapid lateral changes, strong heterogeneities and complex pore structures. Rock physics characteristics are similar between tight sandstones and mudstones, mean while fluid AVO characteristics are unclear. These factors make reservoir prediction and hydrocarbon detection become difficult. The keys to successful exploration are the effective elimination of non-reservoirs, including mudstones and ineffective tight sandstones, and the successful discovery of favorable areas. Rock physics analysis indicates that tight sandstone can be identified by V-p/V-s, while gas-bearing can be distinguished by fluid compressibility. In order to improve inversion accuracy, a new method of favorable area prediction is proposed. Firstly, predict sandstone boundary by V-p/V-s inversion under the control of sedimentary setting. Secondly, distinguish effective reservoirs and gas-bearing areas with porosity inversion and fluid compressibility inversion under the control of sandstone boundary. Finally, confirm favorable areas according to V-p/V-s, porosity and fluid compressibility. The tight sandstones of the He8 formation can be divided into three types. Favorable area I is the first choice of exploration, target followed by the favorable area II, whereas the unfavorable area III is not chosen as exploration target. The new method has achieved excellent results in the favorable area prediction of tight sandstone in the Kangning area and has significant implications for late exploration.