The hydrocarbon enrichment characteristics of the AD well area in Tahe Oilfield, Tarim Basin China

Abstract In response to challenges such as poor identification of low-order faults with weak activity and insufficient understanding of fracture-cavity genetic mechanisms and hydrocarbon enrichment patterns in the fault-controlled karst area of western Tahe Oilfield, this study investigates the development characteristics of faults and fracture-cavity systems, as well as their control on hydrocarbon enrichment. Research indicates that enhancing seismic imaging accuracy through multi-scale filtering can effectively identify low-order faults that are undetectable by conventional seismic attribute analysis. Based on the genetic mechanisms and activity periods of faults, they are classified into three categories. The newly identified NE-trending low-order faults are classified as second-order faults and possess certain hydrocarbon charging capabilities. Controlled by faults and unconformities, fracture-cavity systems are distributed in both shallow and deep layers. In the eastern and western regions, vertical dissolution dominated by fault-controlled is predominant, while the central area exhibits a combination of fault-controlled vertical dissolution and layer-controlled karst conduits. Based on the oil-water distribution characteristics observed in actual drilling, two hydrocarbon enrichment and high-productivity models have been established: 1) NE-trending fault-controlled vertical charging and enrichment along source-connected faults, and 2) lateral charging and enrichment controlled by secondary faults in sandwiched zones. Through hydrocarbon enrichment assessment, both models can be extended from conventional secondary fault-controlled areas to unexplored low-order fault zones, and from shallow layers to unexplored deep formations. The success of appraisal wells has confirmed this understanding, which provides important guidance for the effective development of unproduced reserves in Tahe Oilfield.