深层超压低孔渗、致密砂岩储层物性新认识

New understanding of physical properties of low porosity and permeability,overpressure and tight sandstone reservoirs in deep layer

前陆冲断带深层、超深层已陆续发现了许多大中型油气田,其砂岩储层普遍发育流体超压、低孔低渗、甚至致密,但储层试井渗透率远远大于岩心实测渗透率,且高产、稳产。明确超压致密储层高产原因不但对深化认识深层超压砂岩储层物性和油气充注机理具有学术意义,而且对于提升油气储量具有经济价值。通过岩心微米CT扫描和核磁共振检测实验,剖析了深层超压状态下砂岩储层的物性及其变化。结果表明,流体超压改善了储层的孔隙结构,大大地提升了储层的孔隙度和渗透率,由此推断深层超压砂岩储层可能并不致密,颠覆了由常规测试方法形成的深层储层致密的传统认识。

Many large and medium oil and gas fields have been successively discovered in the deep and ultradeep layers of the foreland thrust belt,and their sandstone reservoirs are generally overpressured,low porosity,low permeability,and even tight. However,the well test permeability is far greater than the measured core permeability,with high and stable production. It is not only of academic significance to understand the physical properties of deep overpressure sandstone reservoirs and the mechanism of oil and gas filling,but also of economic value to enhance oil and gas reserves by clarifying the high-yield causes of overpressure tight reservoir.The physical properties and their changes of sandstone reservoirs under deep overpressure are analyzed by core micro CT scanning and nuclear magnetic resonance testing experiments in this paper. The results show that the fluid overpressure improves the pore structure of the reservoir and greatly improves the porosity and permeability of the reservoir. Therefore,it is inferred that the deep overpressure sandstone reservoir may not be tight,which subverts the traditional understanding of deep reservoir compaction formed by conventional testing methods.