北部湾盆地乌石凹陷东区断裂封闭性评价

Sealing ability evaluation of faults in east area of the Wushi Depression,Beibuwan Basin

借助高精度三维地震、钻井、综合测井等资料,文中选取断面正应力、泥质体积分数、断裂泥比率、断面紧闭指数及一种全新的张扭断裂封闭性评价参数——标准化断裂泥比率(SSGR),利用模糊数学评价方法对乌石凹陷东区断裂开展了封闭性综合评价。结果表明:横向上,乌石凹陷东区断裂封闭性具有区域性特征,自西向东逐渐变差;纵向上,流沙港组一段及涠洲组断裂封闭性整体较好,可作为油气运移的有效遮挡,下洋组封闭性较差,不具现实控藏意义。断裂类型方面,反转断裂反转层段封闭性最好,伸展断裂次之,张扭断裂封闭性较差。分析结果与断裂所封油柱高度拟合较好,为进一步揭示油气成藏规律提供了指导。

Based on the high-precision 3D seismic,drilling and comprehensive logging data,the normal stress on fault surface,shale content,shale gouge ratio,fault tightness index and a new evaluation parameter of transtensional fault sealing,namely standardized mudstone scraping ratio(SSGR),are selected to evaluate the sealing ability of faults in the east area of Wushi Depression by using the analysis method of fuzzy mathematics.The evaluation results show that the sealing ability of faults in the east area of Wushi Depression has the regional characteristics horizontally and becomes worse from west to east;vertically,the sealing ability of the first Liushagang member and Weizhou Formation is better,which can be used as an effective shelter for oil and gas migration.The sealing ability of Xiayang Formation is poor,which has no practical significance for reservoir control.In terms of fault types,the inversion section of inversion fault has the best sealing performance,followed by extensional fault,and transtensional fault has poor sealing ability.The analysis results are in good agreement with the height of the oil column sealed by faults,which provides guidance for further revealing the hydrocarbon accumulation law.