西湖凹陷平湖构造带断裂垂向封闭性研究

Research on vertical sealing of faults in Pinghu structural belt of Xihu Sag

孙思尧 范昌育 蒲仁海 王刚 王爱国 黄雷

西北大学大陆动力学国家重点实验室，陕西 西安 710069 西北大学地质学系，陕西 西安 710069

State Key Laboratory of Continental Dynamics, Northwest University, Xi′an 710069, China Department of Geology, Northwest University, Xi′an 710069, China

西湖凹陷平湖构造带断圈发育，但勘探中失利较多，在其他成藏条件满足的情况下，断层的封闭性是成藏的主控因素。前人在该区断层侧向封闭性的研究中开展了一些工作，仅仅是针对断层侧向封闭性，对断层垂向封闭性的研究重视程度不够，导致漏评大量有利断块，因此断层垂向封闭性有着举足轻重的作用。西湖凹陷P5小层是一套准区域盖层，通过分析P5准盖层上下油气、压力分布以及岩石物理学性质后，使用泥岩涂抹系数（SSF）法对其评价，并以此对典型失利断块进行了分析。研究发现，SSF等于1.9是断层垂向封闭的界限。对T气田中T2失利断块进行分析，发现T2断块侧向封闭性良好，失利的主要原因是垂向封闭性差。西湖凹陷众多断块如K2，K3断块勘探的失利，主要是垂向封闭性差所致。

Fault traps are developed in the Pinghu structural belt in the Xihu Sag， but there are many failures in exploration. When other accumulation conditions are met, the sealing of faults is the main controlling factor for accumulation. Some previous studies on fault lateral sealing have been carried out in this area, but only focusing on the fault lateral sealing, while the research on the vertical sealing of faults has not been paid enough attention, which leds to the omission of a large number of favorable fault blocks. Therefore, fault veertical sealing  plays an important role. The P5 sublayer in Xihu sag is a set of quasi?鄄regional caprocks. By analyzing the oil and gas, pressure distribution and petrophysical properties above and below the P5 quasi?鄄caprock, the SSF method is used to evaluate it, and the typical failed fault blocks are analyzed. The research shows that SSF=1.9 is the limit of fault vertical sealing. The analysis of the failed fault block T2 in T gas field shows that the lateral sealing of the T2 fault block is good, and the main reason for the failure is the poor vertical sealing. The main reason for the exploration failure of many fault blocks in Xihu Sag, such as K2 and K3, is the poor vertical sealing.

10.6056/dkyqt202203011