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利用铸体薄片、阴极发光、扫描电镜、黏土矿物X-射线衍射等手段,对渤南洼陷北部沙四上亚段储层有利成岩相进行了系统研究。结果表明,储层主体处于中成岩A期—B期,在酸碱交替的成岩环境控制下,整体经历多期胶结、溶解和交代的演化过程。根据成岩作用类型及强度,将沙四上亚段储层划分为6种成岩相:硅质胶结—长石溶蚀相(Ⅰ)、绿泥石胶结相(Ⅱ)、中等压实—弱胶结相(Ⅲ)、压实致密相(Ⅳ)、碳酸盐胶结相(Ⅴ)和杂基重结晶相(Ⅵ)。不同成岩相的成岩和物性演化存在差异,导致储层质量明显不同。成岩相Ⅰ以长石溶蚀和硅质胶结作用为主,长石溶蚀增孔作用显著,次生孔隙发育。成岩相Ⅱ和Ⅲ分别发育早期绿泥石胶结和早期烃类充注,对后期胶结物的形成具有抑制作用,原生孔隙得以保存。成岩相Ⅰ、Ⅱ和Ⅲ储层物性好,含油级别较高,试油资料显示具有较高产能,为研究区有利成岩相。成岩相Ⅳ、Ⅴ、Ⅵ分别以压实作用、碳酸盐胶结作用和杂基重结晶作用为主,储层物性差,含油级别低,基本不具备产油能力,为研究区不利成岩相。
The favorable diagenetic facies of reservoirs in the upper Es4 of Bonan Sag have been systematically studied by the means of cast thin slab, cathodoluminescence, scanning electron microscopy and clay mineral X-ray diffraction. The results show that the main body of the reservoir is in the mid-diagenetic stage A-B, under the control of diagenetic environment with alternating acid-base conditions, the whole reservoir undergoes multi-stage cementation, dissolution and replacement processes. According to the type and intensity of diagenesis, the upper Es4 member reservoirs are divided into six diagenetic facies: Siliceous cementation-feldspar facies (Ⅰ), chlorite cementation (Ⅱ), medium compaction-weak cementation (Ⅲ), compacted tight phase (Ⅳ), carbonate cemented phase (Ⅴ) and miscellaneous recrystallization phase (Ⅵ). Diagenesis and physical evolution of different diagenetic facies are different, resulting in obviously different reservoir quality. The diagenetic facies Ⅰ is dominated by feldspar dissolution and siliceous cementation, and feldspar dissolution plays an important role in increasing porosity and secondary pores develop. Early diagenesis and early hydrocarbon filling of diagenetic facies II and III, respectively, have an inhibitory effect on the formation of cements in the later stage and the primary pores are preserved. Diagenetic facies Ⅰ, Ⅱ and Ⅲ have good physical properties and high oil level, and the oil production data show higher productivity, which is favorable diagenetic facies in the study area. The diagenetic facies Ⅳ, Ⅴ and Ⅵ are mainly compaction, carbonate cementation and miscellaneous recrystallization, respectively. The reservoir properties are poor, the oil level is low, and basically they do not have the oil producing ability, which is the unfavorable diagenetic facies in the study area.