3D natural fracture model of shale reservoir based on petrophysical characterization

Abstract

The existence and distribution of natural fractures in shale reservoirs is of great significance to shale gas exploitation. A 3D fracture spatial distribution model with varying reservoir burial depth and regional tectonicsin southeastern Chongqing is constructed based on an enhanced DFN modeling method. Fracture volume density (P32) is calculated by petrophysical test and verified from test wells. The geometric parameters of fractures (length, occurrence, opening) are clustered by regional tectonics. Uncertainties are considered by a stochastic description of the fracture network geometry, utilizing Monte Carlo simulation techniques. The application of the model in seven wells and the quantitative analysis of the relationship between fracture density and burial depth allow the modeling to be extended to deep and ultra-deep reservoirs. Fracture models with reservoirs buried depth over 3000 m are predicted and analyzed. For the various input parameters, the influence of model size and fracture shape on model reliability is analyzed. The establishment of fracture model can effectively quantitatively characterize the reservoir fracture distribution at different burial depths, and its efficient implementation in finite element software can provide support for shale gas mining engineering.