Study On Formation Fracture Prediction Of Low Permeability Reservoir

Fractures are well developed in many petroleum exploration blocks in Jilin oilfield. After field geological observations and studies on well logging, seismic and dynamic data, several results have been attained and are discussed in the dissertation.1. Two types of fractures are developed in the study area: structural and diagenetic, trending nearly NS and nearly WE and consisting of several groups of fractures. Vertical and sharp angled fractures are dominated in the sandstone, while bedding fractures and chicken-cage-like fractures are formed in the mudstone.2. The fractures in the sandstone are characterized by deep and shallow lateral resistance and low micro electrode, as well as low density and high porosity.3. Based on the theory that vertical fractures produce anisotropy of seismic transmission, fracture spatial distribution is analyzed and predicted through 3D seismic data pre-stake processing, the direct modeling of fractured reservoir layers, petrophysical model establishment and fracture attributes analysis. The prediction results have well concordance with that is identified by well logging and dynamic data.4. The study of the structural stress field suggests that the maximum stress bearing be EW. Combined with dynamic data, the EW fractures in the field are open as the NS fractures are closed. Meanwhile, the fracture mechanism study shows that the lithology, thickness and assemblage of the reservoir layers are the internal factors for the development of fractures, while the tectonic movement is responsible externally.5. The fracture study results have been successfully applied to production. Three exploratory wells are designed to spud in Xinbei area, fulfilling recoverable oil reserve 200×104 t. This lays the foundation for producing well network adjustment and oil reserve modeling, and 2%～3% increment of recoverable ratio is delineated.