鄂尔多斯盆地浅水三角洲沉积体系储层非均质性研究——以马岭油田长8油藏为例

Research of reservoir heterogeneity of shallow- water delta system,Ordos Basin:taking Chang 8 reservoir in Maling Oilfield as an example

鄂尔多斯盆地浅水三角洲沉积体系与盆地内三叠系其它开发层系沉积微相的微观特征差异不大,主要区别在于宏观尺度上。以马岭长8油藏为例,采用基于高分辨率层序地层学原理的小层砂层划分对比方法,建立在沉积学基础上的沉积微相以及砂体展布研究,同时采用了较为实用的参数计算方法,对宏观非均质性进行定性-定量表征。结果表明:该类浅水三角洲沉积体系形成的储层在层间、层内和平面上均表现出特有的强非均质性特征。最后对形成原因做了深入研究,认为浅水三角洲沉积体系形成的分流河道频繁改道分叉及侧向迁移,使砂体展布呈网状交织或串珠状展布,这是强非均质性形成的主因,成岩作用和局部微裂缝为次因。

Taking Chang 8 reservoir in Maling Oilfield as an example,sedimentary microfacies and sandbody distribution based on sedimentology were studied by using the division and correlation method of small layer sands based on the principle of high resolution sequence stratigraphy. Meanwhile,macroscopic heterogeneity was expressed quantitatively and qualitatively by the practical parameter calculation method. The result revealed that the reservoir formed in the shallow-water delta depositional system shows unique strong heterogeneity in the interlayer,layer and plane. This was mainly explained by the sandbodies with meshy interweaved or beaded distribution caused by frequently diverted bifurcation and lateral migration of distributary channel,which was formed in shallow- water delta sedimentary system. The diagenesis and the local micro- cracks was a secondary cause.