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本文通过对四川盆地元古宇—下古生界勘探最成功的两个地区——威远震旦系气田和资阳震旦系含气区天然气成藏要素和成藏过程的详细比较,得出:①资阳含气区和威远气田的原始烃源相同,均是下寒武统生成的油裂解的天然气,不同的是资阳为残留的气顶气,威远是水溶气脱溶气。②资阳含气区和威远气田震旦系碳酸盐岩基质孔隙度相近,资阳地区溶蚀洞穴发育,但裂缝不发育,储层渗透性较差,非均质性强;威远地区储层洞穴不发育,但裂缝发育,形成统一的裂缝-孔洞系统。③威远地区具有统一的圈闭,闭合度高(800m),闭合面积大(895km2)。资阳含气区不具有统一的圈闭,多为局部的小高点。④喜马拉雅期隆升作用使资阳统一含气区分散化和气藏变小,形成多压力系统的含气区;威远地区快速大幅度隆升,溶于水中的天然气脱溶,形成具同一压力系统的整装气田。⑤资阳含气区的成藏过程为:(资阳—威远)古油藏→原油裂解→气顶天然气→隆升调整→现今(残留)含气区,其天然气藏是隆升调整成藏,是在原古气藏的基础上改造残留而成;威远地区的成藏过程则是:(资阳—威远)古油藏→原油裂解→天然气大量溶于水中→隆升使得带有大量天然气的水向威远运移和天然气脱溶→现今(新生)气藏,属天然气的脱溶成藏。资阳含气区受古构造的控制明显;威远气田则主要受今构造的制约。因此,在四川盆地震旦系和下古生界的油气勘探中,既要研究其古构造的特征和演化,也要研究今构造的特征和分布规律,才能发现不同类型的天然气藏。
In this paper, a detailed comparison between the gas accumulation in the Weiyuan Sinian gas field and the gas-bearing area in the Ziyang gas-bearing area in the two most successful areas of the Yuanfubu-Lower Paleozoic in the Sichuan Basin shows that: ① The original hydrocarbon sources of the Ziyang gas-bearing area and the Weiyuan gas field are the same, all of which are oil-cracked natural gas produced by the Lower Cambrian. The difference is that Ziyang is the residual capitals, and Weiyuan is the water-soluble gas desolventizing. ② The Sinian carbonate matrix in Ziyang gas-bearing area and Weiyuan gas field have similar porosity, while the dissolution caves in Ziyang area are developed, but the fractures are not well developed with poor permeability and strong heterogeneity in the reservoirs in Weiyuan area Cave is not developed, but the cracks developed to form a unified crack - hole system. ③ Weiyuan area has a unified trap, closed high (800m), closed area (895km2). Ziyang gas zone does not have a unified trap, mostly small local high. ④ Himalayan uplift caused the Ziyang unified gas zone to be decentralized and the gas pool to become smaller, forming a gas-bearing zone with multi-pressure system; the gas from the far-reaching area of Weiyuan was rapidly and sharply uprooted, and the gas dissolved in water dissolved and formed to form the same pressure system The gas field. (5) The process of gas accumulation in Ziyang gas-bearing area is: (Ziyang-Weiyuan) ancient reservoir → crude oil cracking → gas dome gas → uplift adjustment → present (residual) gas-bearing area, Is based on the transformation of the original paleo-gas reservoirs formed; Weiyuan area is the process of accumulation: (Ziyang - Weiyuan) ancient reservoir → crude oil cracking → a large number of natural gas dissolved in water → uplift makes with a lot of natural gas Water migration to Weiyuan and desorption of natural gas → Today’s (newborn) gas reservoir belongs to the desolvation and accumulation of natural gas. The Ziyang gas-bearing area is controlled by palaeostructures obviously; the Weiyuan gas field is mainly constrained by this structure. Therefore, in the exploration of oil and gas in Sinian and Lower Paleozoic in the Sichuan Basin, it is necessary to study the characteristics and evolution of its palaeo-tectonics and to study the characteristics and distribution of this structure so that different types of natural gas reservoirs can be discovered.