油充注和超压形成对库车前陆盆地深层砂岩储层物性作用机理研究

The deeply buried sandstone reservoirs are characterized with overpressure and oil charge occurred in the reservoirs before natural gas charge. Sandstone reservoirs in the Kela-2 gas field with a maximum burial depth over 6000 m display anomalously high porosity (22%) and sandstones with higher porosity have higher palaeo oil saturation. Sandstone reservoirs in the Dabei and Keshen zones are belong to tight sandstone reservoirs, however, 3D porosity/bitumen networks display an excellent interconnectivity and the permeability of the sandstone reservoirs is higher. The developments of excellent sandstone reservoirs have relationship with the oil charge and overpressure and the relationship between sandstone reservoirs compaction, cements formation, oil charge and overpressure evolution are the evidence to reveal the mechanisms of the effect of oil charge and overpressure developmenton on reservoirs physical property.In this study, the petroleum charge history, evolution of pore fluid pressure, sandstone reservoirs pore structure, the carbonate and quartz cements content are studied by fluid inclusions, Quantitative Grain Fluorescence (QGF), 3D micro-CT, in situ carbonate mineral compositions and carbon and oxygen stable isotope technologies for the deeply buried sandstone reservoirs as well as physical simulation experiments on the carbonate cements formation in the reservoirs with oil charge and overpressure to determine the influence of oil charge and overpressure development on diagenesis and reveal the mechanisms of the effect of oil charge and overpressure on physical property.

库车前陆盆地深层砂岩储层普遍发育超压，且存在早期油晚期气充注的特点。克拉2气田砂岩储层经历的古埋深大于6000m，却保留了异常高的孔隙度（22%），高孔隙砂岩对应高的古含油饱和度；大北和克深地区深层砂岩储层虽已致密化，但由孔隙和沥青组成的空间网络在微米尺度上具有较好的连通性，渗透性相对较好。深层优质储层的发育与早期油充注和超压发育有关，砂岩压实和胶结作用过程与油充注和超压演化之间的关系研究是揭示油充注和超压发育对储层物性作用机理的重要证据。本研究将综合运用流体包裹体、颗粒定量荧光、三维微米CT扫描、碳酸盐矿物微区原位成分和同位素等分析技术开展油气充注史、古压力恢复、砂岩孔隙结构、碳酸盐和硅质胶结物研究，并开展油充注和超压作用下储层碳酸盐胶结物形成过程物理模拟实验，确定库车前陆盆地油充注和超压演化对深层储层成岩作用的影响，揭示油充注和超压发育对储层物性的作用机理。

库车前陆盆地深层砂岩储层普遍发育超压，且存在早期油晚期气充注的特点。 深层优质储层的发育与早期油充注和超压发育有关，砂岩压实和胶结作用过程与油充注和超压演化之间的关系研究是揭示油充注和超压发育对储层物性作用机理的重要证据。本研究以库车前陆盆地为研究对象，综合运用流体包裹体、颗粒定量荧光、三维微米CT扫描、碳酸盐矿物微区原位成分等分析技术开展油气充注史、古压力恢复、砂岩孔隙结构、碳酸盐和硅质胶结物研究，确定库车前陆盆地油充注和超压演化对深层储层成岩作用的影响。研究结果表明强烈的构造挤压作用和快速沉积使储层上覆地层压力快速增加是使库车前陆盆地大北和克深地区储层致密化的主要原因，原油充注到砂岩储层中之后在好的盐岩盖层封闭条件下发生欠压实而阻止了水平构造挤压和上覆地层的压实作用，并使砂岩储层中形成超压，超压的发育使砂岩储层中异常高的孔隙得以保存。