歧南断阶带明下段低阻油层地质成因

为了更好地预测区域内低阻油层分布，以岩心、室内试验数据及薄片资料为基础，对歧南断阶带明下段低阻油层的成因机理及控制因素进行了研究。结果表明：研究区低阻油层成因机理主要包括低幅构造、复杂孔隙结构、黏土矿物附加导电性、砂泥岩薄互层、淡水水入侵及钻井液污染6个方面。低阻油层地质成因包括构造、沉积及成岩作用3个方面，明下段沉积时期频繁而强烈的断层活动导致原生油藏发生淡水水侵，同时形成低幅构造，导致低幅构造型低阻油藏发育。受可容空间与沉积物供给比值变化影响，研究区内发育砂泥薄互层型及复杂孔隙结构型低阻油层。早成岩阶段较弱的成岩作用导致研究区发育黏土矿物附加导电性及钻井液污染型低阻油层。受以上3种因素影响，歧南断阶带明下段地层中低阻油层主要发育于与断层相接的低幅构造区域内的弱水动力区。

GEOLOGICAL GENESIS OF LOW-RESISTIVITY OIL LAYERS OF MINGHUAZHEN FORMATION IN QINAN FAULT STEP BELT

In order to better predict the distribution pattern of low resistivity oil layers of the Lower Minghuazhen Formation in the Qinan fault step belt, genetic mechanism and controlling factors of the layers were studied on the basis of core observation, thin section analysis and laboratory testing data. Results show that the genetic mechanism of the low-resistivity oil layers in the Qinan fault step belt depends upon six factors: the low structural amplitude, the complex pore structure, the additive conductivity of clay minerals, the thin sand-shale interbedding, the natural water flooding and the drilling fluid pollution. The geological origin of low resistivity reservoirs includes three aspects: tectonics, sedimentation and diagenesis. Frequent and intense faulting activities lead to natural water flooding and the formation of low amplitude structures. The frequent change in the ratio of accommodation space and sediment supply leads to the formation of the reservoir consisting of thin sand-shale interbedded deposits with complex pore structures. The weak diagenesis of the early diagenetic stage leads to the formation of additive conductivity of clay mineral and drilling fluid pollution. Influenced by the above-mentioned three factors, the low resistivity oil layers of lower Minghuazhen Formation in the Qinan fault step belt mainly develop in the weak hydrodynamic zones of the low amplitude structural areas with connection to faults.