受桐湾运动影响,四川盆地震旦系灯影组发育大规模风化壳岩溶作用.以川中磨溪地区灯四段为例,基于三维地震和钻井、测井资料,分别应用残余厚度法和印模法对灯四段岩溶古地貌进行恢复.对2种方法的结果进行综合分析,按台内带和台缘带精细刻画了灯四段的岩溶古地貌:由东南向西北倾伏,局部存在岩溶高点;根据实际地质条件把岩溶斜坡细分为岩溶缓坡、台缘高点、岩溶陡坡,全区共划分出岩溶台地、岩溶缓坡、台缘高点、岩溶陡坡和岩溶谷地等5种地貌单元.沉积相带、岩溶古地貌和断裂系统共同控制了岩溶储层的发育和分布.台内带:岩溶台地储集空间多为针孔及较小的溶蚀孔洞,整体质量较差,溶蚀作用最弱;岩溶缓坡溶蚀作用较强,储集空间以大的溶蚀孔洞为主.台缘带:岩溶斜坡储集空间主要为蜂窝状溶蚀孔洞,溶蚀作用最强,岩溶强度受断裂控制.结果表明:台缘带断裂系统发育的岩溶斜坡是高质量岩溶储层最有利的发育区,台内带低勘探程度的岩溶缓坡也可作为下一步有利勘探区带.

Due to the Tongwan Movement, large-scale weathering crust karstification developed in the Sinian Dengying Formation, Sichuan Basin. Taking Moxi area as a case, the residual thickness method and the impression method are respectively used to restore the paleogeomorphology of the fourth member of Dengying Formation based on the 3D seismic data and drilling data. Comprehensive analysis shows that the paleogeomorphology in Moxi area is undulating from southeast to northwest with locally karst peak, and it can be subdivided into two parts such as internal zone and marginal zone according to the sedimentary facies. In general there are three geomorphology units, i.e., karst platform, karst slope, and karst valley, while in Moxi area the karst slope can be subdivided into gentle slope, steep slope, and marginal highland based on the restored maps, by which five units developed. The development of karst reservoirs are jointly controlled by sedimentary facies, paleokarst geomorphology, and fault systems. In the internal zone, the karst platform has the weakest dissolution, with storage space of mainly pinhole, and smaller dissolved pores and cavities, while the gentle slope has stronger dissolution, with reservoir space dominated by larger dissolved pores. In the marginal zone, the karst slope has the strongest dissolution, with storage space of mainly honeycomb dissolved pores and cavities, and the karst intensity is also controlled by the fractures. It is shown that the karst slope with fracture system developed in the platform margin is the most favorable zone of the best quality reservoirs, and the karst platform in the internal zone can also be the next favorable play, especially with low exploration degree.