Development Characteristics and Quantitative Prediction of Reservoir Fractures in the Chaoyanggou Oil Field

The Chaoyanggou oil field is a fractured low-permeability reservoir, where the distribution of oil and gas is controlled by the distribution and development of fractures. Based on outcrop, drilling core, thin section and log data, the development characteristics of fractures in this area are described. On this basis, the degree of fracture development was predicted by quantitative analysis of fracture strength and numerical simulation. The result shows that four groups of structural fractures, i.e., in near NS, and EW directions and in due NW and NE directions, were developed in the reservoir, with the nearly NS and EW fractures dominant, which are the along bedding decollement fractures formed by compressive folding action, while low angle shear fractures are related to thrusts. These fractures are mainly formed in the reversed tectonic stage at the end of the Mingshui formation during the Cretaceous period. The degree of fracture development is controlled by such factors as lithology, stratum thickness, faults, folds and depth. The fractures are developed with a clear zonation and are best developed in the northern zone, moderately developed towards the south and poorly developed in the middle zone. These prediction results are in good agreement with interpretation results from logs.