陕北下寺湾油区长7致密油储层物性下限的确定

Lower Limit Determination of Chang 7 Tight Oil Reservoir Property in Xiasiwan Oilfield,Northern Shaanxi Province

针对陕北下寺湾油区长7油层组致密油储层物性下限开展研究。在对储层沉积特征、填隙物特征、孔隙类型、微观孔隙结构综合分析基础上,综合运用物性与含油性关系统计法、压汞法、经验统计法3种方法进行长7致密油储层物性下限确定。研究表明,下寺湾油区长7致密油储层以浊积主水道沉积为主,胶结物成分主要为(铁)方解石、绿泥石、伊利石及伊/蒙混层;孔隙类型主要为溶蚀粒间孔、长石溶孔;平均喉道直径为0.13μm。长7致密油储层孔隙度平均为6.7%,渗透率平均为0.29m D,属小孔隙—微喉道型和小孔隙—微细喉道型储层;3种方法综合确定研究区长7致密油储层物性下限为孔隙度5.3%、渗透率0.11m D。

The research is aimed at the lower limit of tight oil reservoir property of Chang 7 oil-bearing formation at Xiasi- wan Oilfield, Northern Shaanxi Province. On the basis of comprehensive analysis about sedimentary characteristics, inter- stitial material characteristics, pore type, and microscopic pore structures, we comprehensively used the statistical method, the mercury intrusion method and the empirical approach to the relations between physical property and oiliness to deter- mine the lower limit of Chang 1 tight oil reservoir property. Study showed that Chang 7 oil-bearing reservoirs at Xiasiwan Oilfield were mainly turbidite channel sediments, with the main cement compositions being calcite or ferrocalcite, chlorite, illite, and illite-smectite mixed-layer, the main pore types being intergranular dissolved and feldspar dissolved pores, and the average throat diameter being 0. 13/~m. The average porosity was 6. 7%, and average permeability was 0. 29mD. Chang 7 oil-bearing reservoirs belong to small pore ＆ micro throat type and small pore ＆ micro or fine throat type tight reservoirs. By use of these three methods, porosity and permeability of the lower limit of Chang 7 tight oil reservoirs were 5.3% and O. 1 lmD, respectively.