乐安油田草13断块沙四段储集层微观特征及其与驱油效率的关系

利用岩石物性分析、薄片、铸体薄片、扫描电镜和压汞资料,对乐安油田草13断块沙四段储层及其微观结构进行了研究。结果表明,研究区沙四段储层岩性混杂、岩石疏松,属中偏低渗储层。其储层孔隙类型有原生粒间孔隙、晶间微孔隙和溶蚀孔隙,孔隙结构以中孔细喉类型为主;孔隙和喉道分布区间宽,孔喉参数变化范围大,分选和均质程度低,孔喉比偏大,孔隙结构的非均质性较强。利用相关分析法进行的定量分析结果表明,沙四段储层退汞效率与各孔隙结构参数之间存在正相关关系,其中随孔隙度、渗透率增大,退汞效率迅速增加;而随孔喉增大,退汞效率缓慢增加,喉道分选性与驱油效率虽也呈正相关,但相关性较差。总体上,研究区沙四段储层驱油效率随储集物性的变好而增加。

Reservoir microscopic characteristics and displacement efficiency in the fourth member of Shahejie formation of Cao 13 fault block in Le'an Oilfield

Reservoir characteristics and microstructure in the fourth member of Shahejie formation were studied based on analysis of rock physical properties, sections, cast sections, scanning electron microscope (SEM) and intrusive mercury data. The lithology of the fourth member reservoir is mixed and loose, and intergranular pores, intercrystalline micropores as well as dissolved pores. The main pore structure is intermediate pore and thin throat. The pore and throat widely distribute, the pore and throat parameters change greatly. The sorting coefficient and homogeneity are low, the ratio of pore to throat size tends to be on the high side, and the heterogeneity of the pore structure is heavy. The relationship between the efficiency of mercury withdrawal and pore structural parameters was analyzed quantitatively by correlation analysis method. The results indicate that the efficiency of mercury withdrawal is positively correlated to every pore structural parameter. the efficiency of mercury withdrawal increases sharply with the increase of porosity and permeability while increases slowly with the increase of the sizes of the pore and throat. The separating of the pore and throat is positively correlated to displacement efficiency, but such correlation is poor. As a whole, the displacement efficiency of the fourth member reservoir increases with the melioration of reservoir properties.