延长油田坪北区长8储层孔隙结构特征及其对水驱油微观特征的影响

CHARACTERISTICS OF THE PORE-THROAT STRUCTURES AND THEIR INFLUENCES ON THE WATERFLOODED OIL MICRO-FEATURES FOR CHANG 8 RESERVOIR IN PINGBEI BLOCK OF YANCHANG OILFIELD

储层孔隙结构对水驱油特征有重大影响。以延长油田坪北区长8储层为例,综合利用岩心、铸体薄片、扫描电镜、压汞实验等资料对储层孔隙结构进行分析,通过真实砂岩微观模型实验,探讨了不同孔隙结构对水驱油效率的影响。研究表明:长8储层主要岩性为细粒长石砂岩和细粒岩屑长石砂岩,主要孔隙类型为残余粒间孔隙(原生孔隙)、溶蚀粒间和粒内孔隙(次生孔隙);储层类型可分为Ⅰ类、Ⅱ类、Ⅲ类和Ⅳ类,Ⅰ、Ⅱ类为主要储层;水驱油驱替类型以均匀驱替、网状均匀驱替、指状网状驱替以及指状驱替为主,储层物性、孔喉特征对驱油效率有重要影响,Ⅰ、Ⅱ类储层驱油效率高达50%。明确孔隙结构与驱油效率关系可更好地指导油气合理开发。

The structures of the pore and throat possess important influences on the characteristics of the waterflooded oil,taking Chang 8 reservoir in Pingbei Block of Yanchang Oilfield as example,comprehensively integrated with the core,cast thin sheet,scanning electron microscope mercury injection experimental data and so on,the structures were figured out,and moreover through the micro-model experiment of real sandstones,the influences of different pore structures on the waterflooded oil efficiency were explored. The study shows that Chang 8 reservoir is mainly composed of the fine-grained feldspar sandstone and fine-grained lithic feldspar sandstone,the principal pore type,are shown as follows： residual intergranular pore（ primary pore）,dissolved intergranular and intragranular pore（ the secondary pore）; the reservoir types can be classified into Class Ⅰ,Ⅱ,Ⅲ and Ⅳ,ClassⅠand Ⅱare the main reservoirs; the waterflooded oil kinds are generally divided into uniform displacement,reticular uni-form displacement,finger reticular displacement and finger displacement,the reservoir physical properties and pore-throat characteristics have important influences on the oil displaced efficiency,the flooded efficiencies of ClassⅠ Ⅱ reservoirs are up to 50%. Therefore making clear of the relationships between the structures and efficiencies can better guide the rational development of the oil and gas.