南海珠江口盆地Y油田文昌组五段低渗透储层特征及物性控制因素

Characteristics and physical property controlling factors of the low permeability reservoir of the 5^(th) Member of Wenchang Formation for the Y Oilfield in Pearl River Mouth Basin, South China Sea

针对南海珠江口盆地Y油田文昌组五段低渗储层特征及物性主控因素不明确、油田规模开发缺乏地质依据等问题,综合利用铸体薄片、扫描电镜、岩芯物性以及全岩等分析化验资料开展储层物性特征及储层物性主控因素研究。Y油田文五段主要发育岩屑砂岩,其次发育长石质石英砂岩和长石质岩屑砂岩,依据储层物性分类标准,该段为低孔特低渗储层。储层物性主控因素研究表明,文五段沉积时期的构造抬升弱化了压实对储层的改造,改善了储层物性条件;沉积作用控制了不同微相中沉积物的结构成熟度和成分成熟度,进而影响了不同微相的孔渗性,并间接影响了成岩作用对储层的改造;成岩作用对储层改造的定量研究表明,压实作用对储层物性起主导作用,其次是胶结作用,最后是溶蚀作用。研究成果夯实了对南海珠江口盆地Y油田文五段的储层特征及其物性控制因素的认识,为油田下一步规模开发提供了一定的地质依据。

The characteristics of the low permeability reservoirs in the 5^(th) Member of Wenchang Formation of the Y Oilfield in the Pearl River Mouth Basin of the South China Sea and their controlling factors remain unclear up to date, and the geological basis for large scale oil development is insufficient. In term of these problems, various analysis and testing data, such as the data of cast thin section, scanning electronic microscope, and core physical properties, are used conducted in this study. It is revealed that lithic sandstone dominates the reservoir, followed by feldspathic quartz sandstone and feldspathic lithic sandstone. The sandstones are low in porosity and very low in permeability. The research on the main controlling factors on reservoir physical properties further suggests that the tectonic uplifting simultaneously with sedimentation may reduce the compaction of the reservoir to make its physical properties better. Depositional processes control the compositional and texture maturities and the distribution of microfacies, and finally affects the porosity and permeability of the reservoir directly, and the reservoir diagenesis indirectly. Quantitative study of reservoir diagenesis suggests that compaction plays a leading role in reservoir physical properties, followed by cementation and dissolution. The research has much improved the understanding of reservoir characteristics and physical property control factors for the 5^(th) Member of Wenchang Formation of the Y Oilfield in the Pearl River Mouth Basin, and will provide a solid geological basis for the scale development of the oilfield.