复杂构造区天然裂缝差异分布及成因——以塔里木库车前陆冲断带为例OA

The tectonic structure of the southern Tianshan foreland thrust belt is complex,in which natural fractures have extensively developed in deep and ultra-deep tight sandstone reservoirs.The Lower Cretaceous strata,a significant target for exploration and development,have experienced multiple episodes of tectonic movement,forming a complex fracture system that provides essential storage and permeability space for reservoirs.However,there are clear differences in the fracture distribution characteristics among different gas fields,within various folds,and at different stratigraphic levels in the Kuqa foreland thrust belt.Taking the Kuqa Depression as an example,which is a key area for enhanced resource discovery and production,we investigated the differential development of fractures and their genetic types based on imaging logging data,core data,conventional logging data,microscopy,and field geological profiles.The analysis of stress evolution in the study area revealed that since the deposition of the Lower Cretaceous strata,there has been no significant change in the stress field direction,clarifying the structural patterns and combination features of key blocks.The investigation also delineated the characteristics and distribution laws of complex natural fractures in the key block:the fractures in the Bozi-Dabei area mainly trend nearly north-south(N-S),those in the Keshen X area primarily trend nearly east-west(E-W)with some N-S trending fractures,and the Dina Y area is characterized by E-W trending fractures.Three main types of tectonic origin fractures are identified:regional tectonic fractures,deformation-related fractures,and fault-related fractures.Combined with the geological structural background and stress field environment,typical development features of different genetic fractures are summarized,and the fracture distribution characteristics are classified into two primary modes in the Kuqa foreland thrust belt.This study provides a guide for predicting fracture distributions in this foreland thrust belt.