储层结构非均质性及其在深层油气成藏中的意义

Structural heterogeneity of reservoirs and its implication on hydrocarbon accumulation in deep zones

储层孔渗物性的非均质性客观存在,对于地下流体的流动过程影响明显,这不仅对于油气田开发十分重要,在油气运聚成藏研究中也不能忽视。文章讨论一类较为特殊的结构非均质性,即储层中沉积结构的非均质性导致各种致密隔夹层构成某种三维空间结构,阻碍储层中流体的流动,引起埋藏过程中成岩作用、油气运聚成藏及储层致密化过程的强非均质性。模拟分析结果表明这种非均质性会导致油气运移路径和聚集位置的强非均质性。结合岩心观察和油气藏解剖分析,发现准噶尔盆地腹部侏罗系含油储层在埋藏到盆地深层的过程中成岩—成藏作用交替发生,结构非均质性的存在可在深层条件下保持有效储集空间,有利于晚期油气运聚成藏。

Porosity and permeability heterogeneities of reservoirs are common geological phenomena that influence significantly fluid flowing. They are very important not only for oil and gas production but also for oil and gas migration and accumulation researches. In this paper, a kind of special structural heterogeneity was discussed. Owing to the heterogeneities of sedimentary structures in reservoirs, a certain 3D spatial structure is formed by various tight intercalations. Due to the existence of such 3D structures, the flow of fluids in reservoir is impeded, diagenetical heterogeneity is induced during the burial history, and strong heterogeneities are generated in the process of hydrocarbon accumulation and porosity reduction. It is shown from simulation results that this kind of structural heterogeneity can result in strong heterogeneity of migration pathways and accumulation locations. Based on core observation and hydrocarbon reservoir dissection analysis, diagenesis and reservoir formation took place alternatively when Jurassic oil-bearing reservoirs in the central Junggar Basin were buried to the deep zones in the basin. Due to the existence of structural heterogeneity, the high-quality reservoirs can be preserved in the deep zones and it is favorable for the migration and accumulation of oil and gas at the later stage.