鄂尔多斯盆地东南部山西组泥岩封盖性能评价

Evaluation on Sealing Capability of Shanxi Formation in Southeast Ordos Basin

为弥补鄂尔多斯盆地东南部盖层的研究空白,借鉴已有研究成果与盖层基本特征,选取泥岩孔隙度、渗透率、厚度以及排替压力4个参数,结合灰色理论分析方法,对鄂尔多斯盆地东南部山西组泥岩盖层封盖性能进行了综合定量评价。结果表明:盆地东南部泥岩北东部较厚,整体呈从北向南减薄的趋势,南部孔隙度及渗透率均偏高;泥岩盖层排替压力较大,大于8 MPa的平面面积占70%以上;由灰色理论打分评价可知,山西组整体盖层封盖性能较好,封盖能力特强(Ⅰ类盖层)、封盖能力强(Ⅱ类盖层)的盖层分布区域广泛,Ⅰ类和Ⅱ类盖层主要发育于盆地北部、北东部,中部延长、延安、志丹等周边地区,盖层封盖性好,Ⅲ类盖层(封盖能力中等)、Ⅳ类盖层(封盖能力差)主要发育于南部。盖层发育较好的地区,经勘探开发与试气,单井日产量可达上万方,证明评价结果与勘探实践匹配。

No previous researches have been conducted regarding sealing ability of seal in southeast Ordos basin.In order to evaluate the sealing ability in the study area,four indexes including porosity,permeability,mudstone thickness,and displacement pressure were chosen based on grey system theory.The results indicate that the mudstone thickness is thicker in north and east part of the area,which shows a decreasing thickness from north to south.In the south of the study area,the porosity and permeability increase and the displacement pressures of the seal are higher.The area where displacement value is more than 8 MPa accounts for 70% of the study area.The quality of sealing capacity of Shanxi Formation is good and with a wide distribution of type Ⅰ and type Ⅱ.Type I and type Ⅱ distributedcommonly in north and east part as well as areas surrounding City Yanchang,Yan＇an and Zhidan.Type Ⅲ and type Ⅳ developed mainly in the south of the study area.The study has been proved that the well evaluated areas have ten thousands m～3 output in a single well per day.The research conducted will guide next step of gas exploration and exploitation in southeast Ordos basin.