利用数字岩心技术研究变质岩潜山裂缝油藏剩余油特征

Remaining Oil Distribution Patterns of Metamorphic Buried-Hill Fractured Reservoir Based on Digital Core Technology

针对传统裂缝介质岩心驱替实验存在无法观察岩心内水驱油过程及剩余油特征等问题,利用数字岩心技术将传统驱替实验数字化,得到裂缝介质岩心水驱后剩余油特征参数,分析其形成机理。结果表明:不同尺度裂缝中均有剩余油富集,小裂缝中剩余油比例约占1/2,形成的机理为不同尺度裂缝间强烈的干扰效应,导致小裂缝中剩余油未形成足够的驱替压差,从而使小裂缝中剩余油多以分散的油滴形式存在;较大裂缝中剩余油比例约占1/3,形成机理为大裂缝中驱替速度大于原油从岩石表面剥离速度,从而使较大裂缝中剩余油以油簇或油斑形式富集于大裂缝表面,长期的稳定驱替导致该类剩余油处于平衡状态。不稳定注水能打破原有流场分布,有效动用大裂缝的剩余油,表面活性剂驱能提高大裂缝中原油的驱油效率;封堵大裂缝,降低裂缝油藏的非均质程度,同时增大生产压差有利于动用较小裂缝中的剩余油。该项研究对提高裂缝油藏的开发效果具有重要意义。

Traditional core flooding experiment of fractured medium is limited by no observation of waterflooding process and remaining oil distribution. The digital core technology was used to digitize the traditional flooding exper iment and gain the remaining oil characteristic parameters of fractured core flooding and analyze its genesis mecha nism. Research indicates that the remaining oil distributes in the fractures with different scales. The remaining oil in the small-scale fracture accounts for about 1/2, which results from the strong interference between the fractures with different scales. There is no sufficient displacement pressure -different for the remaining oil in the small-scale fracture, and the remaining oil usually distributes as scattered pattern. The remaining oil in the fracture with rela tively large scale accounts for 1/3, which results from the higher di placement velocity in the fracture with relatively large scale than that of the oil on the rock surface. The remaining oil in the fracture with relatively large scale usual ly distributes on the fracture surface as the form of oil cluster or pol spot. Long-term steady displacement leads to a balance for the remaining oil. Unsteady water injection can break the original flow field distribution and effectively produce the remaining oil in the fracture with relatively large scale. Surfactant flooding can improve the oil displace ment efficiency of the remaining oil in the fracture with relatively large scale. Fractured reservoir heterogeneity can be improved by plugging the large-scale fractures and the remaining oil in the small-scale fracture can be recovered by increasing producing pressure difference. This research could provide great significance to the improve the devel opment performance of fractured reservoir.