Geological model and characteristics of dissrete fracture network in tight sandstone gas reservoir constrained by multi-factors

Key words:  multi-factors  tight sandstone  discrete fracture network  reservoir geological model

Abstract:

As important flow channels in tight sandstone reservoirs, fracture networks have complicated distribution characteristics and are controlled by multiple geological factors, which have restricted the modeling of fractured sandstone reservoirs. Based on seismic, geological,logging and thin sections data in the KX area, scale limits for fractures or faults were revised and re-evaluated in terms of from fracture mechanics and scale features. The formation periods of fractures were inferred by means of structural evolution history and fluid inclusions tests in order to establish geological model for fractures. Then relationships between the fracture parameters and tectonics, lithology, physical properties were analyzed in detail, and the main controlling factors for distribution of fracture parameters were concluded and optimized. A set of fault-fold-fracture symbiotic systems at different scales were then established. By using entropy weight theory, each factor was assigned relative weights in the above analyses, through which the single fracture intensity curve of every well and 3-D fracture intensity model were built. Finally a complete discrete fracture network model(DFN) for different scales is found using four key techniques, including using determination approach to build large-scale fracture model; and using SGCS to interpolate or build middle and small-scale fracture model. The results show that fractures of tight sandstone in the KX area have obvious multi-scaleand multi-stage characteristics.The optimized modeling method restricted by multiple geological factors is effective for establishing a discrete fracture model, offers feasible improvement over traditional DFN constructions, and provides a reliable geologic basis for progressive optimization and adjustment of tight sandstone reservoir development scheme.