鄂尔多斯盆地合水地区长8储层特低渗透成因分析与评价

Origin Analysis of Extra Low-Permeability and Evaluation of Chang 8 Reservoir in Heshui Area of Ordos Basin

鄂尔多斯盆地合水地区长8储层的物性总体较差,发育粒间孔、溶孔,孔隙结构类型属小孔隙、微细喉道和微喉道型;分析表明其特低渗透成因主要受沉积作用和成岩作用的共同影响,不同沉积微相储层的物性差异较大,柔性组分含量高、粒度细和成分成熟度较低是造成储层特低渗透特征的主要原因;同时成岩压实、胶结作用使得储层的孔隙度减小、渗透性变差,而溶蚀作用和少量成岩微裂缝的产生又在很大程度上改善了储层的特低渗透性能;水下分流河道与河口坝砂体是研究区主要储层的分布相带。

Chang 8 reservoir of Heshui area in Ordos Basin is poor in accumulation properties, where the reservoir mainly develops intergranular fine pores and emposieu. The synthetical study of the origins of extra low-permeability shows that sedimentation and diagenesis have great impact on the origins of extra lowpermeability together. The varying accumulation properties in different sedimentary microfacies, the content of low-energy component, fine grade and the low compositional maturity are mainly responsible for the extra low-permeability. The permeability becomes worse as the compaction and cementation have decreased the porosity. However, denudation and fractures have improved the extra low-permeability to some great extent. Subsea river channel and mouth bar sand body are the mainly distributed facies of reservoir.