准噶尔盆地克百断裂封闭性研究及其对成藏的控制作用

The Sealing Properties of Ke-Bai Fault and Its Control on Oil Accumulation in Junggar Basin

克百断裂为一大型逆掩断裂,其封闭性能控制了克拉玛依—百口泉地区油气的分布。对区域主应力方向、断裂带岩性特征、测井响应、地层水性质的研究表明,克百断裂的封闭性具有分段的特点。断裂封闭段的断裂走向与主应力方向近于垂直,断裂带断层泥发育,破碎带厚度、声波时差变化幅度差、井径扩大值较小,地层水以CaCl2型为主,钠氯比值小于0.7。断裂开启段的断裂走向与主应力走向交角小于45°,断裂带断层泥不发育,破碎带厚度、声波时差变化幅度差、井径扩大值较大,地层水以NaHCO3和Na2SO4型为主,钠氯比值大于0.85。断裂开启段是该区主要的油气充注点,而断裂封闭段是下盘油气的主要封堵段,是下盘油气聚集的有利地区。

The Ke-Bai fault is a large overthrnst fault. Its sealing properties control the distribution of oil accumulation in the northwestern area of Junggar basin. By analysis of the tectonic stress, fault zone characteristics, logging response and formation water features, we come to a conclusion that the Ke-Bai fault is typical of sectional sealing. The fault seals well where the fault strike is vertical to the tectonic stress, the tectonic mudstone rock is developed, the thickness of the damage zone, change of AC and increment of SDT are relatively small, the formation water is of CaC12 type near the fault zone, and the Na＋ to C1- ratio is less than 0.7. The fault seals badly where the intersection angle of fauh strike with the tectonic stress is less than 45~, the thickness of the damage zone, change of AC and increment of SDT are relatively large, the formation water is of NaHCO3 or Na2SO4 type, and the Na＊ to C1- ratio is more than 0,85. The sector of the fault where it seals badly is the major migration pathway, while the foot wall part where the fault seals well is the preferential place for oil accumulation.