珠江口盆地陆丰凹陷古近系低渗储层应力敏感性研究

Study on Stress Sensitivity of Paleogene Low-permeability Reservoirs in Lufeng Sag of Pearl River Mouth Basin

珠江口盆地陆丰凹陷古近系以低渗储层为主,开发过程中面临地层压力衰竭引发应力敏感性的问题。为揭示陆丰凹陷古近系低渗储层的应力敏感特征及主控因素,选取该区域古近系储层天然岩心,开展储层应力敏感性评价试验,并结合岩心铸体薄片、图像分析、扫描电镜和高压压汞等方法,分析了储层物性、矿物成分和孔喉结构特征对岩石应力敏感性的影响。结果表明:陆丰古近系低渗储层岩心应力敏感性最大损害率为20.96%~94.44%,敏感性损害程度为弱—强,不同岩心应力敏感损害程度差异大。矿物组分和孔喉结构特征是岩石应力敏感性损害的主控因素,岩石敏感性损害率与石英、长石含量密切相关,相关性可达0.9;孔隙分布、连通性及喉道宽度也很大程度上影响着岩石的应力敏感性,岩石孔喉结构越差应力敏感性越强。研究成果可指导陆丰凹陷古近系低渗油田的高效开发。

The Paleogene reservoirs in Lufeng Sag of the Pearl River Mouth Basin is dominated by low-permeability ones,and stress sensitivity caused by formation pressure depletion is facing during the development.In order to reveal the stress sensitivity characteristics and main controlling factors of the Paleogene low-permeability reservoirs in the Lufeng Sag,natural cores of the Paleogene reservoirs in the region were selected and the evaluation test on the stress sensitivity of the reservoirs was carried out,and the effects of reservoir physical properties,mineral composition and pore throat structure characteristics on the stress sensitivity of the rocks were analyzed by combining core cast thin section,image analysis,scanning electron microscopy and mercury injection at high pressure.The results show that the maximum damage rate of core stress sensitivity in the Lufeng Paleogene low-permeability reservoirs ranges from 20.96%to 94.44%,and the degree of sensitivity damage is weak to strong with large differences in different cores.Mineral components and pore throat structure are the main controlling factors of stress sensitivity damage in rocks,and the sensitivity damage rate of rocks is closely related to the content of quartz and feldspar with correlation up to 0.9;pore distribution,connectivity and throat width also largely affect the stress sensitivity of rocks,and the rocks with worse pore throat structure has stronger stress sensitivity.The research results can guide the efficient development of the Paleogene low-permeability oilfields in the Lufeng Sag.