Abstract

As the main gas production layer, the subsalt Cretaceous Bashijiqike Formation of Kuqa foreland basinis charactered by large depth and poor matrix properties. Structural fractures are widespread with complicated characteristics and distribution, which have large influence on gas production. A lot of effort has been put into the research on the fracture in this area, the research includes refined fracture description on the basis of core and image log data; multi-methods and multi-times fracture distribution pattern prediction. However, the above studies are limited by core availability, seismic data quality, well log data, etc, so the fracture prediction results were not good. Considering the fractures of super-deep tight sandstone reservoirin Kelasu structural belt having the characteristics of multiscale, and the development characteristics, origin and distribution pattern of fractures with different sizes being different, this study defined fracture classes, systematically summarized the development characteristics and distribution patterns of fractures at different scales and their groups, and explored the control effect of fracture system on reservoir. The following understandings are obtained: (1) based on fracture length, aperture, development characteristics, etc, fractures are divided into three classes, namely first order fracture – large fractures, second order fracture – grain penetrating fractures, third order fracture – grain margin fractures; (2) based on fracture length, origin, and combination characteristics, three classes of fracture combinations are recognized, namely first order fracture combination – dominant fracture belt; second order fracture combination – dominant fractures and associated fractures; third order fracture combination – grain margin fracture network; (3) fractures are the main flowing channel in superdeep tight sandstone reservoir, fractures effectively improved reservoir flow property and act as the main contributor of high and stable production in low porosity sandstone reservoir.

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