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断层封闭性对西湖凹陷平湖油气田的油气分布具有重要的控制作用,对其开展系统的研究和评价是目前勘探实践的需要。利用断层泥比率、泥岩涂抹潜力及构造应力场分析等方法对平湖油气田5条主要断层进行了封闭性综合评价。结果表明: 当断层泥比率大于60%且泥岩涂抹潜力大于4时,基本达到断层侧向封闭条件。断层封闭性与构造应力相关,拉张应力期,断层开启; 挤压应力期,断层封闭。平湖油气田0号断层在平湖组P4—P12砂层组沉积时期封闭性好,在平湖组P1—P3砂层组沉积时期封闭性差;在花港组沉积时期断层封闭性中等。1号断层在平湖组沉积时期封闭性较好,在花港组沉积时期封闭性差。2号断层在平湖组沉积时期封闭性较好,在花港组沉积时期封闭性好。4号断层和11号断层在平湖组、花港组沉积时期封闭性均差。
The fault sealing plays an important role in controlling the oil and gas distribution in Pinghu oil and gas field in Xihu Sag. Therefore, it is necessary to conduct a systematic study and evaluation of the faults. Based on the ratios of fault mud, smear potential of mudstone and tectonic stress field, five major faults in Pinghu oil and gas field are evaluated comprehensively and closedly. The results show that when the ratio of fault mud is more than 60% and the potential of mudstone smear is greater than 4, the condition of lateral sealing of the fault is basically reached. Fault sealing is related to tectonic stress. During tensile stress, the fault is open. During the compressive stress period, the fault is closed. Fault No. 0 in Pinghu oil and gas field has good sealing in the sedimentary period of the Pinghu Formation P4-P12 sand group, poor sealing in the sedimentary period of the P1-P3 sandstone group in Pinghu Formation, and fault sealing in the sedimentary period of Huagang Formation. The No. 1 fault has good sealing in the Pinghu Formation during its deposition period and poor sealing during the deposition period of the Huagang Formation. Fault No. 2 has a good seal during the deposition of Pinghu Formation and good sealing during the sedimentation of Huagang Formation. Fault No. 4 and fault No. 11 in Pinghu Formation and Huagang Formation were poorly closed during deposition.