Fractures Characteristics and Quantitative Evaluation of Ultra-Deep Tight Sandstone Reservoir in Kuqa Depression, Tarim Basin, Northwest China

Abstract

As the main gas production layer, the subsalt Cretaceous Bashijiqike Formation of Kuqa foreland basin is 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 development characteristics, origin, and distribution pattern of different size of fractures are different, this study defined fracture classes, summarized the development characteristics and patterns of various clssses of fractures and their groups, and explored the control of reservoirs by fracture system. 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.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018