四川叠合盆地海相碳酸盐岩油气分布特征及其构造主控因素

为了研究四川叠合盆地海相碳酸盐岩油气藏的分布规律和主控因素，预测勘探接替区，从盆地区域构造角度，分析油气沿（或在）拉张槽、古隆起和盆山结构区的分布特征，探讨拉张槽、古隆起和盆山结构对海相油气成藏和分布的控制作用，并据此探讨四川叠合盆地深层-超深层海相油气的勘探前景和有利地区。研究发现，拉张槽控制油气成藏的基础条件，即烃源岩、储集岩和优质源-储组合的发育，为油气成藏打下了坚实的物质基础；古隆起是油气运聚的指向地区，控制古油藏和古气藏的形成与演化，奠定了油气成藏的主要聚集区，属于油气藏的建造过程；盆山结构则进一步改变盆地内的构造格局，再分配和调整古油气藏，形成现今油气藏，属于改造过程。拉张槽是油气早期富集最根本的控制因素，古隆起是油气运聚的指向地区，盆山结构是油气晚期散失最主要的控制因素，从基础到建造再到改造的一系列过程相辅相成，共同控制了四川叠合盆地海相碳酸盐岩油气的分布。在此基础上，推测川西中北段深层-超深层是未来四川叠合盆地海相碳酸盐岩油气勘探最主要的有利地区，具备形成大型气田的基本条件，可能是原生气藏和次生气藏共存的天然气富集区，理由为：①具有以下寒武统优质烃源岩为主的多源供烃系统；②具有多时代优质储集层的叠合层系；③具有以断裂（及不整合面）和优质储层构成的立体输导网络；④具有致密碳酸盐岩、泥质岩和膏盐等构成的多级封盖系统。

Distribution characteristics of marine carbonate reservoirs and their tectonic controlling factors across the Sichuan superimposed basin

Based on structural and tectonic geology, this paper discussed the distribution characteristics and their structural/tectonic controlling factors of the marine carbonate oil and gas accumulation around/on the intracratonic sags, paleo-uplifts and basin-mountain systems across the Sichuan superimposed basin. During the early stage of hydrocarbon accumulation formation, the intracratonic sags controlled the formation of high-quality source rocks, reservoir rocks and their assemblage, whilst the paleo-uplifts controlled the hydrocarbon migration and accumulation to form paleo oil reservoir and paleo gas reservoir. Subsequently, the basin?mountain systems changed the structural geology and adjusted the hydrocarbon accumulations to accommodate gas-fields across the basin. It is considered that the intracratonic sags are the essential factors for hydrocarbon accumulation in early stage, paleo-uplifts are the best places for hydrocarbon migration and accumulation, and the basin-mountain systems are the most important factor for hydrocarbon accumulation and adjustment in late stage. The coupling relationships accounted for hydrocarbon distri?bution in carbonates across the Sichuan basin. Therefore, it is suggested that the prospect areas of deep to super-deep reservoir in carbonates are in the middle and northern segments of the western Sichuan Basin, where could be dominant with large?scale primary and secondary gas reservoirs. There are four favorable factors as following: （1） wide-spread high-quality source rocks of Lower Cambrain black shale, （2） high-quality multi reservoir rocks, （3） good carrier or conducting network composed of faults and unconformities for hydrocarbon migration and accumulation, and （4） multi cap rocks composed of low?porosity and low-permeability carbonate, mudstone and gypsum-salt strata.