东海盆地西湖凹陷花港组储层孔隙演化与油气充注关系

采用岩石薄片鉴定、扫描电镜、电子探针、流体包裹体分析等测试技术，在储层基本特征分析基础之上，结合埋藏史、热演化史，利用孔隙恢复定量计算方法，对东海盆地西湖凹陷中央反转构造带中北部渐新统花港组致密砂岩储层的孔隙演化进行系统恢复，并探讨了孔隙演化与油气充注关系。研究表明，花港组储层孔隙演化主要经历了早成岩B期末的14.28%，中成岩A期末的10.35%，中成岩B期的8.75%。伴随储层成岩-孔隙演化，花港组储层先后接受了3期油气充注。第一、二期（19~17 Ma和17~9 Ma）油气充注发生于储层尚未致密的中成岩A期末以前，尽管其成藏意义不大，但充注带入的有机酸性流体却对储层物性改善起到了关键性作用，为后续油气充注提供了有利条件。第三期（7~0 Ma）大规模油气充注发生于储层逐渐致密化的中成岩A期末-中成岩B期，主要充注对象为埋深较浅且尚未完全致密化的花港组H3小层。因此，H3小层是现今花港组在总体致密化背景下相对最为有利的油气勘探目标。 

Relationship between porosity evolution and hydrocarbon charging in tight sandstone reservoirs in Oligocene Huagang Formation,Xihu Sag,East China Sea Basin

The pore evolution of tight sandstone reservoirs in the Oligocene Huagang Formation in the central and northern parts of the central reversal structural belt in the Xihu Sag of the East China Sea Basin was recovered based on the analyses of reservoir properties, burial history and thermal evolution history, and using cast thin section identification, scanning electronic microscope, electron microprobe, fluid inclusion analyses and porosity recovery quantified calculation. The relationship between porosity evolution and hydrocarbon charging was also discussed. The results showed that the porosity evolution in the Huagang Formation can be classified into three stages:14.28% in the stage B of early diagenesis, 10.35% in the stage A of middle diagenesis, and 8.75% in the stage B of middle diagenesis, accompanied by three stages of hydrocarbon charging. The first (19-17 Ma) and second (17-7 Ma) stages of hydrocarbon charging took place before the end of stage A of middle diagenesis. The reservoirs were not tight yet, and the acidic fluid brought by hydrocarbon charging played an important role in reservoir reformation, providing favorable porosity and permeability for later hydrocarbon charging. The third stage (7-0 Ma) of massive hydrocarbon charging happened from the end of stage A to the stage B of middle diagenesis, when reservoirs compacted gradually. The third section of Huagang Formation, buried shallow and was not tight yet, showed relatively better reservoir properties and became a main charging target. It is now the most favorable hydrocarbon exploration target for the Huaguang Formation in the overall densification background.