鄂尔多斯盆地正宁地区长8油层组储层特征

Characteristics of Chang 8 reservoir in Zhengning area,Ordos Basin

为推进鄂尔多斯盆地正宁地区致密油气的勘探开发,基于长8油层组岩心薄片、扫描电镜及压汞资料,分析了储层发育特征、储层致密化的原因及物性与含油性的关系。结果表明,长8油层组岩性以岩屑长石砂岩和长石岩屑砂岩为主,填隙物含量较高,碎屑颗粒结构成熟度低。储层孔隙包括基质孔隙和裂缝两大类,基质孔隙主要发育粒间孔和长石溶孔,裂缝主要发育构造裂缝和成岩微裂缝。基质孔隙以小孔、细喉为主。压实作用和胶结作用均是储层致密的主要原因,天然裂缝是油气重要的渗流通道,溶蚀作用和天然裂缝均改善了储层物性。物性分布与砂体分布具有较好的一致性,长81小层物性明显优于长82小层。良好的物性是油井高产的关键因素。

In order to promote the exploration and development of tight oil and gas in Zhengning area,Ordos Basin,based on core slice,scanning electron microscope and mercury injection data,reservoir characteristics,reservoir densification and relationship between physical properties and oil-bearing property were analyzed. The Chang8 sandstone is mainly composed of feldspar lithic sandstone and lithic feldspar sandstone,with high content of interstitial matter,which is mainly composed by ferroan calcite,hydromica,chlorite membrane,kiesel,and kaolinite. The Chang 8 sandstone is low in clastic structure maturity,which is mainly medium-sorted subangular particles. Matrix pores and natural fractures jointly form reservoir pore system,and matrix pores are mainly small pores with fine throat. Compaction and cementation are main densification origins for Chang 8 tight reservoir.Natural fractures are main percolation pathway,and together with dissolution,they improved reservoir physical properties. Physical properties of Chang 81 reservoir are obviously better than that of Chang 82 reservoir. Oil-bearing is relative with physical property. Better physical property is the key for high oil production.