四川叠合盆地深层海相碳酸盐岩油气的形成和分布理论探讨

Discussion on the theories of the hydrocarbon formation and distribution of the deep-seated marine carbonates in the Sichuan superimposed basin, China

利用地质—地球物理—地球化学综合研究方法,以叠合盆地构造多阶段演化和油气多期成藏过程为主线,揭示四川叠合盆地深层海相碳酸盐岩在(曾)深埋和长(多)期构造差异性作用下油气的形成和分布理论。研究提出四川叠合盆地深层海相油气形成的四中心耦合成藏理论及油气分布的三级三元联控理论。认为天然气藏的形成是在多期构造作用控制下由油气四中心(生烃中心、生气中心、储气中心和保气中心)的耦合关系决定的,"三中心"(生气中心、储气中心和保气中心)在空间上的分布关系决定了油气的最终分布;盆地级别(第一级)的三元素(烃源岩发育、有机质成气率高和保存条件佳)控制了油气分布的基础条件和勘探前景;区带级别(第二级)的三元素(拉张槽、古隆起和盆山结构)联合控制了油气分布的有利区带;圈闭或油气藏级别(第三级)的三元素(圈闭闭合高度、封盖强度和油气充注程度)具体控制了规模性气田的分布。油气四中心耦合成藏理论和三级三元联控理论的提出,对(四川)叠合盆地深层天然气勘探开发具有重要的指导意义。

In this paper, a comprehensive geology-geophysics-geochemistry research method was used to reveal the theories of oil and gas formation and distribution in deep marine carbonates in Sichuan superimposed basin under the effect of （ancient） deep burial depth and long- term （multi-phase） structural difference with multi-stage structural evolution and multi-phase reservoir formation process in superimposed basins as the main research line. And two theories were proposed on the formation of marine oil and gas in deep zones in the Sichuan superimposed basin and they are the four-center coupling reservoir formation theory and the three-level three-element joint control theory. It is indicated that the formation of gas reservoirs is controlled by the coupling relationship of four hydrocarbon centers （hydrocarbon generating center, gas generating center, gas storage center and gas retention center） under the effect of multi-phase tectonism, and the ultimate distribution of oil and gas is dominated by the spatial distribution relationship of three centers （gas generating center, gas storage center and gas retention center）. Oil and gas distribution is controlled in terms of basic conditions and exploration prospects by three basin-scale （the first level） factors （developed source rocks, highly matured organic and high-quality sealing conditions）. The favorable hydrocarbon distribution zones are jointly controlled by three play-scale （the second level） factors （intracratonic sags, paleo-uplifts and basin-orogenic belt systems）. And the distribution of large-scale gas fields is dominated by three trap-scale or reservoir-scale （the third level） factors （trap closure, seal strength and hydrocarbon infilling richness）. Both four-center coupling reservoir formation theory and three-level three-element joint control theory are significant for the exploration and development of deep gas in Sichuan superimposed basin and other superimposed basins in China.