苏里格气田储层的新型辫状河沉积模式

鄂尔多斯盆地苏里格气田二叠纪下石盒子组盒8段和山西组山1段表现出明显的岩石学、沉积学和古气候特征:①碎屑颗粒粒度粗,成分成熟度和结构成熟度低;②反映强水动力条件的交错层理和块状构造发育,垂向粒序变化大;③砂体侧向叠置普遍;④存在暴露标志;⑤在沉积期,古气候为季节性干旱气候。这些特征表明苏里格气田储层属辫状河沉积。根据这些特征以及目的层与其他相似的古代和现代沉积的沉积学类比结果,建立了新的苏里格气田储层的沉积模式。与传统的辫状河沉积模式相比,新建立的沉积模式强调:气田盒8、山1沉积时期发育了废弃河道、决口扇以及泛滥平原沉积,使得储层砂体的隔层、夹层发育。不稳定试井数据揭示的有效砂体规模以及有效砂体的岩石相构成研究表明,苏里格气田储层骨架砂体连片性好,但有效砂体仅呈透镜状分布在骨架砂体中。

New braided river model in Sulige Gas Field of Ordos Basin

The eighth member of Shihezi Formation(He8) and the first member of Shanxi Formation(Shan1) of the Permian in Sulige Gas Field of Ordos Basin show obvious petrological,sedimentological and geologic climatic characteristics as follows.The clastic grain size is large,and the mineralogy and fabric maturity are low.The common cross-strata and massive structures showing strong water dynamic conditions are developed,and the vertical grain successions varies greatly.There are commonly lateral superposition of sandstones and exposure signs.There was seasonally dry geologic climate during the deposition period.These characteristics indicate the intervals deposited from the braided rivers.Based on the above characteristics,a new braided river model for the reservoirs of Sulige Gas Field was established.Compared with the traditional braided river models,the new model emphasizes that abandoned channels,crevasse splays and flooding plains were developed during the deposition periods of He8 and Shan1 Member and resulted in the frequent interlayers in the reservoir.The sizes of effective sandbody indicated by unstable well test and the constitution of effective sandbody show that the framework sandbody in the reservoirs of Sulige Gas Field has good continuity,and the effective sandbody is distributed in the framework sandbody in the shape of lens.