珠江口盆地东部地区从北往南,地温梯度整体升高,不同地温梯度范围的储层物性随埋深变化趋势不同,低孔低渗深度下限差异明显.在大量铸体薄片和岩心分析的基础上,结合扫描电镜、X-衍射、压汞测试等资料,开展该地区不同地温梯度下的储层特征响应研究,结果表明:①高地温梯度下压实强度高、速率快、压实减孔效应明显.②高地温梯度下成岩演化快,成岩作用复杂,铁白云石等晚期胶结物类型多,浅埋藏条件下长石等易溶颗粒已不完全溶解并伴随高岭石的沉淀,高岭石伊利石化深度浅.③高地温梯度导致的成岩演化的加速最终使砂岩储层的孔隙结构多为小孔细喉型.④不同地温梯度地区低孔低渗的埋深界线不同,低地温梯度区为4600 m,中低地温梯度区为3500~4000 m,中高和高地温梯度区分别为3200和2600 m.⑤低地温梯度区中深部储层甜点寻找方向为原始沉积条件优、成分和结构成熟度高的中粗粒以上粒级砂岩,抗压实能力强,可保存较多的原生孔;而超压保护、有效次生孔隙发育和早期烃类充注可成为高温盆地中深层储层甜点的有利条件.%The overall geothermal gradient of the eastern area in the Pearl River Mouth basin increases from the north to the south.The variation trend of reservoir physical property with burial depth in different geothermal gradients is different, and the difference of the maximum depth limit of low porosity and permeability reservoir is distinct.Based on abundant casting thin sections and core analysis, combining data of SEM, XRD and mercury injection etc., reservoir property responses under different geothermal gradients are carried out in the research area.The results show that: ①under high geothermal gradient, compaction strength is stronger, rate is higher, and porosity loss by compaction is more obvious;②diagenetic evolution is faster and more complex under high geothermal gradient, resulting in more late cements such as ankerite, incomplete dissolution of soluble granules such as feldspar and kaolinite precipitation at shallow burial depth, as well as the conversion from kaolinite to illite;③acceleration of diagenetic evolution resulted from high geothermal gradient causes pore structure poorer, usually fine pore throat;④the burial depths of low porosity and low permeability reservoirs vary with geothermal gradients.The depths are 4600 m, 3500~4000 m, 3200 m and 2600 m under low, low-medium, high-medium and high thermal gradients, respectively;⑤medium-coarse sandstone with superior original deposition condition and high maturity of composition and texture in the deep reservoir under low geothermal gradient is sweet spot for exploration because more primary pores are kept due to its strong compaction resistance, while overpressure protection, effective secondary pore development, and early hydrocarbon charging are favorable conditions for medium-deep sweet spot in the high geothermal basin.
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