缝洞型油藏剩余油形成机制及分布规律

采用钻孔和熔蜡的方法分别制备了缝洞油藏定量模型和随机模型,并用两种模型进行全直径岩心驱油实验,研究缝洞型油藏中剩余油形成机制及分布规律。研究结果表明:驱替相与被驱替相的密度差异和缝洞连接点位置决定溶洞中流体分布规律;一次水驱结束后剩余油包括油水密度差异形成的"阁楼油"、油水置换非瞬时性造成的"封存油"、溶洞不规则性造成的"角隅油"、缝洞复杂连接关系或者低连通度造成的"盲洞油"以及岩石润湿性造成的"油膜"。连接点位置越高,"阁楼油"含量越少;注入速度越低、原油黏度越小,"封存油"含量越少;溶洞形状越规则,角隅数量越少,"角隅油"含量越少;缝洞连接关系越简单、连通程度越高,"盲洞油"含量越少;水湿岩石表面"油膜"含量较少。

Formation mechanism and distribution law of remaining oil in fracture-cavity reservoirs

Based on the relationship between the molecule structure of monomers and their performance,two types of polymerizable monomers with low oil/water interfacial tension have been synthesized,which coplymerizes acrylamide to create a novel polymer oil displacement agent under complex initiator and low polymeric temperature.Its structure and distribution status in brine solution were characterized by infrared spectroscopy and freeze etching electron microscope.The results show that the polymer has good water solubility,viscosifying properties,salt-resistance and temperature-tolerance,shearing-resistance in brines.Due to the graft polymerization of acrylamide and the polymerizable surface-active monomer,the polymer overcomes chromatographic separation effect,and has low oil/water interfacial tension.Interfacial tension of 0.15% solution of the polymer(prepared in Daqing simulation brine) is around 10?1 mN/m in Daqing No.1 oil plant crude oil.Core flooding experiments show that the oil recovery of the novel surface active polymer is 5.2% higher than that of ordinary hydrolyzed polyacrylamide because of its better viscosifying performance and lower oil/water interfacial tension.