珠一坳陷深层砂岩储层孔隙演化研究

Research on the evolution of pores in deep sandstone reservoir in ZHU 1 depression

过去珠一坳陷古近系砂岩储层因埋藏深,其储层物性受到质疑,国内外深部优质储层的不断发现大大拓宽了油气勘探的新领域。通过对砂岩储层的沉积环境、岩石成分、成岩作用、矿物转化等与孔隙特征的关系综合分析发现,胶结作用是导致深部储层物性变差的主要因素,粘土矿物、硅质和硬石膏胶结堵塞了孔隙;深部储层毗邻珠江口盆地最为重要的烃源岩,在中成岩A亚期,有机质处于高成熟阶段,有机质生烃以及粘土矿物在转化过程中所释放出的酸性水的溶解作用是产生大量次生孔隙的重要因素,深部异常超压是孔隙得以保存的条件,珠一坳陷作为油气勘探的新领域,次生孔隙的大量出现和超压对孔隙的保护揭示了其巨大的勘探潜力。

The petrophysical properties of the Palaeogene deep sandstone reservoir in ZHU 1 depression have been queried because of its great burial depth. The successional discoveries of high-quality reservoirs in great depths have remarkably opened up a broad field of oil-gas exploration. Based on a comprehensive analysis of the connection of the characteristics of pores with the depositional environment, rock composition, diagenesis, and mineral transformation, we prove that the cementation is the major factor making the petrophysical properties of deep reservoir deteriorated. The pores will be blocked up by clay minerals, siliceous cement and anhydrite. The deep reservoir neighbours upon the most important source rock in the Pearl river mouth basin. The organic matter has undergone a high-mature time at the middle diagenesis stage A. The dissolving effect of organic acid produced in hydrocarbon generation and in transformation of clay minerals may produce substantial secondary pores in the reservoir, and the existence of deep abnormally high pressure is a crucial condition for partial original and secondary pores to be preserved. A great potential for prospecting oil and gas in the ZHU 1 depression is revealed by the enormous secondary pores and the protection given by the abnormally high pressure.