Horizontal Well Path Design with Seismic Inversion for a Shale Oil Reservoir in the Ordos Basin, China

Abstract

The shale oil reservoir of Chang 7 member, Yanchang Formation in Ordos basin has shown great potential. They are highly heterogeneous and relatively thin sand body interbedded with mudstone and siltstone. This proposes the demand for accurate and high-resolution inversion data. We propose a workflow to plan the horizontal well path with seismic interpretation. Basic interpretation is conducted, which included well tie, horizon interpretation, and fault interpretation. A time-to-depth conversion workflow based on full waveform inversion, is proposed to gain the precise seismic and inversion data. The velocity model of FWI shows more high wavenumber variations that reflect thin and localized geological features than that of conventional migration velocity analysis. The geological statistical inversion is applied to get the high-resolution reservoir models for the thin layers beyond the seismic resolution. A comprehensive index is computed with the inverted parameters to reflect the quality of reservoir and identify the sweet-spots. We define the coordinates, direction and length of horizontal section on the sweet-spot maps. After that, the sections of seismic and inversion data along the paths are extracted to define the depth of the paths. In the study, the optimal paths are close to the centerline of target oil sand layers. The effectiveness of the workflow was verified by the application practice in Qingcheng oil field, Ordos Basin.