关键词: 四川盆地, 深层—超深层, 碳酸盐岩, 泥灰岩, 成藏条件, 勘探潜力

Abstract: The deep–ultra-deep carbonate rock series in Sichuan Basin have an area of about 10×10⁴ km², with superposition and orderly distribution of source rock and reservoir, showing huge exploration potential. After systematically studying the basic petroleum geological conditions of deep–ultra-deep formation in Sichuan Basin, the possible exploration types and their exploration potential are analyzed, and the future exploration orientation is put forward. The study results show that: (1) The “rift–depression” structural cycle controlled the distribution of deep–ultra-deep carbonate reservoirs. Four sets of thick dolomite reservoirs were developed in the region, and their distribution was mainly controlled by sedimentary facies zones, with the most favorable reservoir developed in platform margin at the edge of the rift. (2) The structural pattern of multi-stage alternating uplift and depression controlled the widespread marine source rocks in Sichuan Basin, among which source rocks with the best quality included the Cambrian Maidiping Formation–Qiongzhusi Formation, Silurian Longmaxi Formation, and Permian Longtan Formation. (3) The conventional porosity type carbonate reservoirs were mainly developed in the Sinian–Cambrian and Permian in the northwestern and central–eastern Sichuan Basin, with burial depth of 6000-10000 m. Three types of hydrocarbon accumulation combinations were formed, i.e., lower source rock and upper reservoir, side source rock and side reservoir, and upper source rock and lower reservoir, with superior hydrocarbon accumulation conditions. The key zones for increasing reserves on a large scale include Dengying Formation platform margin and Changxing Formation reef flat in the northwestern margin of Yangtze Craton, and the reef flat in the lower combination in the Sinian and Permian in the eastern Sichuan Basin, with a resource scale of more than one trillion tons. (4) The unconventional marl reservoirs were mainly developed in the first member of Maokou Formation (Mao 1 member) and the second sub-member of the third member of Leikoupo Formation (Lei 32 sub-member), with integrated source rock and reservoir, burial depth of 3000-6000 m, and resources of more than 3×10¹² t, which is expected to be a major replacement field. The favorable area of Mao 1 member is mainly distributed in the eastern–southern Sichuan Basin, while that of Lei 32 sub-member was mainly distributed in the central Sichuan Basin.

Key words: Sichuan Basin, deep–ultra-deep formation, carbonate rock, marl, hydrocarbon accumulation condition, exploration potential