Fracture distribution and prediction of weathering crust reservoirs on the top of Leikoupo Formation, Xinchang area, western Sichuan Basin

Abstract

The Leikoupo Formation in the western Sichuan Basin is an important potential stratum for the increasing of reserves and production. Recently, industrial grade gas flow has been discovered for the first time from weathering crust reservoirs on the top of Leikoupo Formation in the Xinchang area. Dissolution pores as well as fractures are the main storage spaces and seepage channels. Then, how to accurately predict the distribution characteristics of these cracks in weathered crust reservoirs has become a key factor of advance exploration process. Core observation and imaging logging data were applied to clarify the geological characteristics of fracture development. Some seismic prediction methods such as coherence, dip, azimuth and curvature attributes were used to identify the plane distribution characteristics of fracture development zones. Results show that the fractures in weathering crust reservoirs on the top of Leikoupo Formation are mainly in the middle and low angles, and the strikes are NE-SW, NW-SE and near EW. Structure fractures are mainly distributed in the central and eastern area and near the big fault. In the southwest of the study area, there are NE-SW and NW-SE "net-like" interlayer fractures, of which the scale of the NE fractures is larger. Based on the analysis results of multiple methods, the fracture characteristics and distribution rules of weathered crust reservoirs on the top of Leikoupo Formation were determined. The prediction results are consistent with newly drilled wells and provide a reliable basis for the evaluation in future.

Keywords

• weathering crust
• fracture
• image logging
• curvature attribute
• leikoupo formation
• xinchang area
• western sichuan basin