作者简介:杨 智(1980—),男(汉族),中国石油勘探开发研究院高级工程师、博士. E-mail: yangzhi2009@petrochina.com.cn
中文责编:晨 兮; 英文责编:子 兰
DOI: 10.3724/SP.J.1249.2015.03257
从毫-微米级孔喉圈闭油气,向微-纳米级孔喉连续型油气延伸,是油气储层地质研究的趋势,加强对非常规油气储层微观表征研究意义重大.应用场发射扫描电镜和纳米计算机断层扫描重构等先进技术,在含油气致密泥页岩、砂岩和灰岩储层中发现孔径小于1 μm的纳米级孔喉系统普遍发育.研究发现,在非常规源储共生层系油气储层内,纳米级孔喉是储集空间的主体,占储集空间总体积的70%~80%,微米到毫米级孔隙、裂缝等储集空间仅局部发育.非常规油气致密储层主体孔径为20~500 nm,其中页岩气储层孔径为5~200 nm,页岩油储层孔径为30~400 nm,致密灰岩油储层孔径为40~500 nm,致密砂岩油储层孔径为50~900 nm,致密砂岩气储层孔径为40~700 nm.油气水在纳米级孔喉系统中,渗流能力差,油气被滞留吸附,在源储共生层系中大面积连续分布,泥页岩烃源层中可能滞留了占总生烃量30%~40%的油气资源,近源致密砂岩、灰岩等储层中可能聚集了20%~30%的油气资源,纳米级孔喉储集空间中很可能聚集了超乎想象的巨量油气资源.非常规致密储层中纳米级孔喉系统的发现,改变了对油气储层微观孔隙空间的传统认识,对认识非常规源储共生层系油气连续聚集的地质特征,拓展资源潜力有重要战略价值.
Petroleum geologists are expanding their perspective from conventional traps to unconventional continuous reservoirs, and characterization study for unconventional tight reservoir in micro-meter and nano-meter scale is becoming more and more important. Based on the field emission scanning electron microscope(SEM)and the nano-CT reconfiguration technique, we verify the nano-pore-throat system in tight sandstone, shale and limestone with size less than one micron. Systematic studies show that nano-scale pore-throat system develops extensively in rocks of unconventional reservoirs serving as both source and reservoir rock. The nano-scale pores provide the main storage space accounting for 70%-80% of the total, and millimeter-pores, micro-pores and micro-fractures develop much less. Pore diameter of the unconventional tight reservoir rock is mainly 20-500 nm, in which 5-200 nm for that of the shale gas reservoir and 30- 400 nm for that of the shale oil reservoir, the pore size of the tight limestone oil reservoir is 40-500 nm, pore size of the tight sandstone oil reservoir is 50-900 nm, and pore size of the tight sandstone gas reservoir is 40-700 nm. Oil, gas and water existing within the nano-pore-throat system are difficult to flow or separate. Oil and gas are caught or adsorbed and distributed extensively in the symbiotic layer of source and reservoir rocks. Petroleum resources caught in shales account for 30%- 40% of the total generated, and those in tight sandstone and limestone adjacent to source rock account for 20%-30% of the total. Consequently, unimaginable amounts of oil and gas resources may be accumulated in the nano-scale pore-throat space in unconventional reservoirs. The discovery of nano-scale pore system within unconventional tight reservoirs has changed the traditional understanding of the micro space fabric of reservoir rocks. This provides the significant scientific value on further understanding the geological characteristics of continuous petroleum accumulation in unconventional reservoirs, and increasing more valuable resources of unconventional reservoirs in future.