四川盆地东北部气田海相碳酸盐岩储层固体沥青研究

Solid Bitumens in the Marine Carbonate Reservoir of Gas Field in the Northeast Area of the Sichuan Basin

川东北地区海相碳酸盐岩生物礁滩相储层中普遍存在着固体沥青。本文以普光气田上二叠统长兴组和下三叠统飞仙关组储层中固体沥青为研究对象,在显微镜下观察固体沥青的产状特征,测定固体沥青含量和计算固体沥青与储层孔隙的体积比率,分析固体沥青的成因及形成期次,推算古油藏的密度。普光气田飞仙关组固体沥青主要呈环边状附于鲕粒白云岩?残余鲕粒白云岩晶间溶孔,溶蚀孔壁,沥青含量在1.11%～5.73%之间,均值2.92%;长兴组生物礁储层固体沥青多呈团块状充填于各种溶蚀孔洞中,沥青含量0.31%～11.72%之间,均值3.57%。两套储层中的固体沥青含量都有随埋深而减少的趋势。飞仙关组储层中固体沥青与储层孔隙的体积比约为22%,长兴组为43%～56%。普光气田储层固体沥青为热演化成因并为两期形成,飞仙关储层固体沥青为轻质油古油藏裂解形成,长兴组储层固体沥青为稠油古油藏裂解形成。

Solid bitumens are distributed widely in the organic reef and bank-facies reservoir of marine-facies carbonate in the northeast of the Sichuan basin. This paper focused on the solid bitumens of Upper- Permian Changxing Formation and Lower-Triassic Feixianguan Formation reservoirs in the Puguang Gas Field. Based on our observation under microscope, their contents and the volumetric proportions of the solid bitumens to reservoir pore, this study analyzed genesis and forming period, finally calculated the density of palaeo-reservoirs. The solid bitumens of Feixianguan Formation in the Puguang Gas Field occurs mainly as circular banded in pores and dissolved pores and walls in oolitic dolomite and remnant oolitic dolomite. The content ranges from 1. 11 % to 5. 73%, averaging to 2. 92%. The solid bitumens of Changxing biogenetic reef reservoir occurs mostly as patches in various dissolved pores, with the contents ranging from 0.31% to 11.72% （averaging to 3.57%）. The contents of the solid bitumen are decreasing with depth. Volumetric proportions between solid bitumen and reservoir pore is about 22% for the Feixianguan reservoir and 43%-56% for the Changxing reservoir. The solid bitumen of the Puguang Gas Field is thermal evolution in origin and had two forming periods. The solid bitumen of Feixianguan reservoir was generated from cracking of light oil palaeo-reservoir, while the solid bitumen of Changxing reservoir was generated from cracking of heavy oil palaeo-reservoir.