摘要
基于恒速压汞实验和扫描电镜分析,分析松辽盆地北部下白垩统18块特低渗—致密砂岩样品(渗透率为(0.05～14.90)×10-3μm2)孔隙结构,研究孔隙结构参数的变化规律,总结其控制因素。结果表明:从特低渗至致密砂岩样品,孔隙体进汞饱和度及喉道半径明显降低,但孔隙体大小变化不大;随渗透率降低,位于低压段的"大孔—细喉型"孔隙比例逐渐降低,渗透率低于0.25×10-3μm2,位于高压段的"树形网络"孔隙影响致密砂岩储集及渗流能力。压实和黏土胶结共同主导孔喉结构的演化,前者以机械挤压形式破坏"大孔—细喉型"孔隙空间,对孔渗相关关系影响较弱;后者以化学沉淀方式充填粒间孔及溶蚀孔,对砂岩储集空间及渗流能力造成不同程度的破坏,使孔渗相关关系变差。与特低渗砂岩相比,致密砂岩的孔喉比大,达到渗流阈值时充填孔隙的比例低,易发生水锁等伤害。研究结果有助于深化致密砂岩储层孔喉结构演化及成因机制等方面的认识。
The study of characteristics of microscopic pore structure and its impacts on macroscopic physical properties of ultra-low permeability and tight sandstones is the basis for further understanding the genetic mechanism of tight sandstones reservoirs.Based on rate-controlled porosimetry(RCP)and scanning electron microscopy,the pore-throat structures of 18 ultra-low permeability and tight sandstones samples from the lower Cretaceous in northern Songliao basin were probed and compared for studying the evaluation of pore throat structure and its controlling factors.It is concluded that the pore bodies intrusion saturation and throat radius decrease significantly from the ultra-low permeability to tight sandstones,but the pore bodies radius does not change as much.With the decrease of the permeability,the percentage of"large pores connected with narrow throats"presented in the low pressure section decreases gradually,and when the permeability is lower than 0.25×10-3μm 2,the"treelike network"pores presented in the higher pressure section plays a major role in the accumulation and seepage capacity of tight sandstone reservoirs.Compaction and clay cementation both dominate the evaluation of pore-throat structure.Compaction mechanically destroys both large pore bodies and narrow throats,which has a weak influence on the correlation between porosity and permeability.While clay cementation fills the intergranular pores and dissolution pores by chemical precipitation,and leads to the different kinds of destruction for the accumulation and seepage capability of tight sandstones,which causes the poor correlation between porosity and permeability.Compared with ultra-low permeability sandstone,the pore-throat ratio of tight sandstones is larger,the percentage of filled pore space corresponding to the percolation threshold is lower,indicating that tight sandstones are more inclined to water lock.This study will help to further deepen the understanding of the pore-throat structure evolution and genetic mechanism of tight sandstone reservoirs.
作者
张飞飞
Zhang Feifei(Oil Recovery Plant No.10 Daqing Oilfield Company Limited,Daqing,Heilongjiang 163517,China)
出处
《东北石油大学学报》
CAS
北大核心
2018年第5期54-62,128,129,共11页
Journal of Northeast Petroleum University
基金
国家自然科学基金项目(41602141)
构造与油气资源教育部重点实验室开放基金项目(TPR-2017-15)
关键词
松辽盆地
致密砂岩
恒速压汞
孔隙结构
成岩作用
Songliao basin
tight sandstone
rate-controlled porosimetry
pore structure
diagenesis
