Paleotectonic stress field modeling and prediction of natural fractures in the Lower Silurian Longmaxi shale reservoirs, Nanchuan region, South China

Abstract

Natural fractures serve as significant storage spaces for hydrocarbons and are favorable for fluid flow in shale gas reservoirs; therefore, predicting the intensity and distribution of natural fractures within reservoirs are of extreme significance for shale gas exploration and development. Natural fractures in the Nanchuan region are generally in high dip angles, and the dominant fracture strikes are in the ∼NE-SW and ∼NW-SE directions. Most natural fractures within the Longmaxi Formation are formed in the Late Yanshanian period. Therefore, in this study, the Late Yanshanian paleotectonic stress field was numerically investigated. The comprehensive rupture rate (CRR) was defined and calculated as an indicator to quantitatively predict the intensity and distribution of natural fractures within the Longmaxi Formation. The results indicated that regions with well-developed fractures were mainly located in/around fault zones and fold zones, among fault/fold orientations change, and at fault tips. The intensity and distribution of natural fractures in the Longmaxi Formation of Nanchuan region were influenced by many factors including tectonic activities, mineral compositions, etc. The present study provides preliminary insights into natural fractures within the Longmaxi Formation of Nanchuan region, South China, which can guide and support shale gas exploration and development.