牛庄洼陷西南部沙三中亚段浊积岩储层成岩作用与物性演化

通过岩心观察、薄片鉴定、图像分析、包裹体分析、碳氧同位素分析及物性测试等技术方法,结合埋藏史、有机质热演化史和油气成藏史,对东营凹陷牛庄洼陷西南部沙三中亚段浊积岩储层成岩作用与物性演化进行研究。结果表明:沙三中亚段浊积岩储层整体以中低孔—低渗特低渗为特征,经历了弱碱性—酸性—碱性—弱酸性的成岩环境演化过程;成岩作用类型多样,主要胶结溶解作用序列为早期菱铁矿胶结/早期方解石胶结→长石溶蚀/石英加大/自生高岭石沉淀→铁方解石、铁白云石胶结/少量石英溶蚀→少量长石溶蚀/石英加大/黄铁矿胶结,压实作用存在于整个埋藏过程中;物性演化与油气成藏史的匹配关系表明,沙三中亚段浊积岩常规储层与致密储层共存,其中致密储层分为"边致密边成藏型"和"先致密后成藏型"两种类型;常规储层主要位于中厚层砂岩的中部,对勘探最有利,其次为"边致密边成藏型"储层,主要存在于中厚层砂岩的顶部或底部,"先致密后成藏型"储层最不利,多为薄层砂岩。

Diagenesis and physical properties evolution of turbidite reservoirs in Es3z of Niuzhuang sag, Dongying Depression

A comprehensive analysis was conducted to evaluate the diagenesis and property evolution of Es₃^z in Niuzhuang sag, by combining core observation, thin section identification, image analysis, fluid inclusion analysis, carbon and oxygen isotope analysis and physical property test. The burial, thermal and hydrocarbon charging history of the reservoirs were also taken into consideration. The results show that the turbidite reservoirs of Es₃^z are characterized with low porosity and permeability, and may have experienced diagenetic environment changes through the sequence of weak alkaline, acidic, alkaline, and weak acidic conditions. With various diagenesis, the main dissolving-cementation sequence was:early siderite and calcite cementation; feldspar dissolution/quartz overgrowth/authigenic kaolinite precipitation; first hydrocarbon charging; ferrocalcite/ankerite cementation/quartz dissolution; second hydrocarbon charging; a small amount of feldspar dissolution/quartz overgrowth/pyrite cementation, and finally compaction existing throughout the whole burial history. According to the matching relation of reservoir physical properties and hydrocarbon accumulation, both conventional reservoirs and tight reservoirs coexisted in the turbidites, and the tight reservoirs could be further divided into two types, one became tight reservoirs during hydrocarbon accumulation and the other became tight before hydrocarbon accumulation. It is concluded that the best exploration targets are the conventional reservoirs followed by reservoirs becoming tight during hydrocarbon accumulation, and then the reservoirs becoming tight before hydrocarbon accumulation.