苏丹穆格拉德盆地福拉凹陷AG1层低阻油层形成机制及其控制因素

Formation mechanisms and controlling factors of low resistivity pays of AG1 layer in Fula Sag,Muglad Basin,Sudan

首先综合各项资料研究低阻油层成因,并将低阻油层按成因分类,分别研究其测井响应特征,然后明确不同油田各成因类型分布,将其与储层地质特征对比分析,明确低阻油层形成控制因素。结果表明,低阻油层形成机制包括泥质含量高、孔隙结构复杂、存在导电矿物、黏土矿物附加导电、油气充注不足等。低阻油层形成控制因素可分为沉积因素、成岩因素、沉积-成岩综合因素及成藏因素。沉积因素对低阻油层的控制主要通过对泥质含量的控制实现;成岩因素对低阻油层的控制主要体现在导电胶结物的沉淀和孔隙结构复杂化上;沉积-成岩综合因素对低阻油层的控制主要体现在黏土矿物和有效储层展布上;成藏因素的控制作用体现在条件较差时,油气充注不足,造成油层低阻。各油田储层地质特征不同,低阻油层控制因素不同,最终造成低阻油层成因类型分布出现差异。

Comprehensive data analyses were applied to study and categorize the formation mechanisms of low resistivity pays.Accordingly,the mechanismsare summarized as high mud content,complex pore structure,conductive minerals,additive conductive caused by clay minerals and insufficient hydrocarbon incharge,respectively. The well log responses of different types of low resistivity pays and the distribution of different types were studied. Then reservoir characteristics of AG1 layer of different oilfields were studied simultaneously with the distribution of different low resistivity pay categories. Several factors were found to be the controlling factors of low resistivity pays,including sedimentary,diagenesis,sedimentary-diagenesis,and hydrocarbon accumulation. The first three factors affect the low resistivity pays through the control on the shale content,the conductive cement content and the complexity of pore structure,and the clay mineral content and the distribution of effective reservoir,respectively. The hydrocarbon accumulation factor mainly controls the distribution of low resistivity pays when hydrocarbon incharge was insufficient. Because of these different reservoir characteristics and controlling factors,the distribution of different categories varies in the four oil fields.