南海 A 油田珠江组钙质层成因与控制因素分析

南海 A 油田珠江组内部发育多套钙质层，它是控制底水上升及剩余油分布的主要因素。 利用岩石薄片鉴定及碳、氧同位素分析，研究了不同钙质层的岩石组分，并确定了其物质来源及形成阶段；结合沉积特征，探讨了钙质层的沉积主控制因素。 结果表明：钙质层在微观成因上具有一致性，即主要由成岩过程中孔隙流体的化学沉淀而形成；物质来源上具有多源性，主要来源于同生碳酸盐的结晶、生物碎屑的溶蚀及黏土矿物的转化。 宏观上钙质层的分布受构造深度、钙质层与泥岩厚度比及沉积旋回等沉积因素的控制，平面分布具有一定的连续性和突变性；底钙层分布面积大的区域剩余油富集程度高。

Origin and controlling factors of calcareous interlayers of Zhujiang Formation in Nanhai A oilfield

Several sets of calcareous interlayers are well developed in Zhujiang Formation in Nanhai A oilfield, and they are the main factors controlling bottom water rising and remaining oil distribution. Based on rock thin section identification, carbon and oxygen isotope analysis, the rock components in calcareous interlayers were studied, and its origin and forming stages were defined. Combined with sedimentary characteristics, the controlling factors of calcareous interlayers were discussed. The results show that calcareous interlayers have consistency at microscopic origin, and they are formed by the chemical precipitation of rock pore fluid during the diagenetic process. The calcareous material came from the crystallization of contemporaneous carbonates, the dissolution of bioclasts and the transformation of clay minerals. The distribution of calcareous interlayers are controlled by structural depth, their thickness ratio to mudstone and sedimentary cycle, with the characteristics of continuity and discontinuity in lateral. The enrichment degree of remaining oil is high in the large distribution area of bottom calcareous interlayers.