白豹油田延长组低电阻率油层成因机理研究

Genesis Mechanism of Low Resistivity Pay Zone in Yanchang Formation of Baibao Oilfield

白豹油田三叠系延长组长4+5储层孔隙结构复杂,引起束缚水饱和度高,测井显示高孔隙度、低渗透率。为提高测井解释符合率,研究了该储层低电阻率成因。利用测井、岩心物性、压汞、薄片、水性分析、试油等资料,对正常油层长3和低电阻率油层长4+5的岩石学特征、孔隙结构特征、物性、电性特征做了详细的对比研究和评价。分析了6种因素对长4+5储层形成低电阻率油层影响,即:泥质、阳离子交换量、地层水矿化度、高孔隙度、粒度、束缚水饱和度。认为复杂的孔隙结构、高束缚水饱和度、岩性粒度细和高孔隙度是长4+5形成低电阻率油层的主要原因。利用核磁共振测井资料确定束缚水饱和度的方法提高了低电阻率油层解释精度。根据研究结果对白豹地区的B154井进行地质解释,其结论与实际情况相符。

Pore structure of Chang4＋5 reservoir complicated that it causes high irreducible water of Yanchang Formation in Triassic System is so saturation, and log data shows the reservoir has high porosity and low resistivity in Baibao Oilfield. In order to improve the log interpretation veracity, studied is the genesis of the low resistivity reservoir in this area. Based on various information, such as well logging, core analysis, mercury injection, slices analysis, water analysis and well test,compared are lithology, pore structure, physical property and electric property of the Chang4＋5 low resistivity reservoir and the Chang3 normal reservoir. Analyzed are six factors that influence the low resistivity pay zone in Chang4＋5 reservoir： mud content, cation exchange capacity, water mineralization, high porosity, granularity and irreducible water saturation. It is considered that the complicated pore structure, high irreducible water saturation, fine granularity of formation and high porosity are the main reason for the zone in Chang4 ＋ 5 reservoir. The method using NMR data to calculate irreducible water saturation increases the precision of log interpretation. Based on the research conclusion, interpreted is the geologic characteristic of well B154 in Baibao area. The interpretation result is in accordance with the real situation.