川东北地区上二叠统盘龙洞生物礁储层特征及其主控因素分析

Reservoir Characteristics and Main Controlling Factors of Upper Permian Panlongdong Organic Reefs in Northeastern Sichuan

盘龙洞生物礁是目前所发现的川东北地区最具特色的长兴组二叠系生物礁,其生物礁古油藏是此类型古油气藏的典型代表。通过对其岩相特征、储集空间、沥青含硫特征及成岩作用分析认为:该生物礁古油藏储集空间良好,充填有大量演化程度较高的沥青,以炭质沥青和沥青质沥青为主;沥青具高含硫特征,这可能与热化学硫酸盐还原作用(TSR)反应有关,TSR反应可使沥青具高含硫特征,同时为晚期溶蚀作用提供了酸性物质H2S等;白云石化作用过程是等体积交代,使盘龙洞生物礁储层中分散的微小孔隙整合变大或连通,增强了岩石的渗透能力,同时为后期岩石大规模的溶蚀作用奠定了物质基础;溶蚀作用的2个阶段对生物礁储层具有不同的作用效果,准同生阶段的溶蚀作用易于形成选择性溶蚀孔隙,晚期溶蚀作用主要对白云质储层进行大量溶蚀改造,晶形发育不完整的白云石被优先溶蚀。

Panlongdong organic reefs is the most typical Permian reefs of Changxing Formation in northeast- ern Sichuan, and its paleo-reservoir is the typical representation of this kind of reservoirs. By analyzing the lithofacies features, reservoir space, sulfur-containing asphalts characteristics and diagenesis, this paper indicates that the reef paleo-reservoir has good reservoir space and is filled with massive higher-evolution- degree asphalt, mainly carbonaceous and asphaltene asphalts. The thermochemical sulfate reduction （TSR） occurred in this reservoir, and the asphalt with high sulfur was the result of TSR reaction and pro- vided acidic material such as HaS for dissolution at late. The replacement process of dolomitization was an equal volume replacement. Dolomitization made the dispersed small pores of Panlongdong reefs reservoir become bigger and connect, enhanced the petrosal transmission capacity and established the material base for large-scale dissolution at later time. The two stages of the dissolution had different action effects for reef reservoirs. The dissolution of parasyngenetic stage was prone to become the selective denudation pore. The advanced dissolution mainly dissolved and reformed the dolomitic reservoirs, and the dolomites whose crystal form was developed half-baked would be corrosed at first.