川中德阳—安岳古裂陷槽震旦系灯影组残丘型储层特征及其油气勘探意义

川中德阳—安岳古裂陷槽东侧磨溪—高石梯地区灯影组已建成以台缘带为主、台地内为辅的大规模天然气生产基地，而同期德阳—安岳古裂陷槽内灯影组遭受更强烈岩溶作用，灯影组残丘型储层发育，且距离寒武系筇竹寺组优质烃源岩更近，具备形成大型天然气藏的潜力。结合前期勘探认识，精细研究了川中德阳—安岳古裂陷槽灯影组残丘型储层特征、形成过程和成藏条件。结果表明：①古裂陷槽内灯二段遭受强烈的表生溶蚀和河流深切侵蚀作用，形成多个大规模的残丘型储层；②古裂陷槽内灯二段残丘型储层溶蚀孔洞、裂缝均广泛发育，储集类型多样，储层厚度大，同一残丘内各类储层纵横向变化快，物性差异大，非均质性强；③古裂陷槽分布面积达6×10⁴ km²，灯影组残丘型储层宽度大于40 km，长度大于150 km，储层发育，上部受筇竹寺组和麦地坪组烃源岩遮挡、侧向受滩间洼地致密层封堵，近优质烃源岩天然气优先充注，生储盖组合良好，在古裂陷槽内具备形成多个大型的残丘型潜山天然气藏的地质条件，是该区下一步天然气勘探的有利方向。

Characteristics of residual hill-type reservoir of Sinian Dengying Formation in Deyang-Anyue ancient rift trough,central Sichuan and its significance for oil and gas exploration

A large-scale natural gas production base has been established in the Dengying Formation of Moxi-Gaoshiti area on the east side of Deyang-Anyue ancient rift trough in central Sichuan, which is mainly based on the platform margin zone and supplemented by the platform. The Dengying Formation in Deyang-Anyue ancient rift trough was subjected to more intense karst in the same period, and the residual hill-type reservoir of the Dengying Formation in the ancient rift trough was more developed, which was closer to the high-quality source rock of the Qiongzhusi Formation, and had the potential to form large-scale gas reservoirs. Combined with the preliminary exploration, the characteristics, formation process and accumulation conditions of residual hill-type reservoir of Dengying Formation in Deyang-Anyue ancient rift trough in central Sichuan are carefully studied. The results show that: (1) Deng 2 Member in the ancient rift trough was subjected to strong supergene dissolution and deep erosion of rivers, forming many large-scale residual hill-type reservoirs. (2) The dissolution pores, dissolution caves and fractures of the residual hill-type reservoirs of Deng 2 Member in the ancient rift trough are widely developed. The reservoir types are diverse and the reservoir thickness is thick. All kinds of reservoirs in the same residual hill-type reservoir change rapidly in vertical and horizontal directions, having large physical property differences and strong heterogeneity. (3) The distribution area of the ancient rift trough is up to 6×10⁴ km², the residual hill-type reservoirs of Dengying Formation is developed, which has a width of more than 40 km and a length of more than 150 km. The upper part of Dengying Formation is blocked by the source rocks of Qiongzhusi Formation and Maidiping Formation, and the lateral part of Dengying Formation is blocked by the dense layer deposited in the tight layers in the interbeach depressions. The natural gas of near high-quality source rocks is preferentially filled, and the source-reservoir-cap rock combinations are well good. The good geological conditions for the formation of multiple large residual hill-type natural gas reservoirs are in the ancient rift trough. The residual hill-type reservoirs of Deng 2 Member in the ancient rift trough are favorable for the next step of natural gas exploration.