地下侧积砂坝建筑结构研究及储层评价——以孤东油田七区西Ng5^(2+3)砂体为例

The Architecture and Rreservoir Evaluation of Underground Lateral Accretion Bar:a case study on the Ng5^(2+3) sand-body in 7^(th) block west of the Gudong oil field

分析了在不同沉积环境下侧积砂坝的沉积模式,研究了侧积体的空间组合特征,并利用模式预测的方法建立侧积砂坝的建筑结构模型。研究表明,孤东油田七区西Ng52+3侧积砂坝是小型河流形成的,其侧积体的空间组合模式为水平斜列式,侧积体的宽度为80~240 m,倾角为5°~12°。薄片、扫描电镜分析证实,七区西Ng52+3的成岩作用较弱,原始的粒间孔隙保存完好,储层孔隙度平均为32.3%,渗透率为3500×10-3μm2。侧积砂坝内含有高岭石、蒙脱石、伊利石等粘土矿物,使其储层物性变差。

Based on the published depositional models of lateral accretion bars formed in different environment, this paper studied the spatial assemblage patterns of the lateral accretion bodies and established architectures of lateral accretion bars through model prediction method. It is revealed that lateral accretion bars are formed by small - size river in the Ng5^2＋3 of 7th block west, Gudong oil field. The spatial assemblage model of the lateral accretion bodies is horizontal echelon pattern, the width of the lateral accretion bodies is 80 -240 m, and the dip angle is 5° - 12°. By thin slice and SEM （Scanning Electronic Microscope） analysis, it is concluded that diagenesis is weak and the primary intergranular pores are in good conservation in the Ng5^2＋3 of 7th block west, Gudong oil field. The average porosity and permeability of the reservoir are 32.3% and 3 500 × 10^-3 μm^2 , respectively. There are several types of clay minerals in the lateral accretion bars, such as kaolinite, montmorillonite and illite, which weaken the quality of the reservoir.