Abstract: In the middle and late stage of development of offshore heavy oil field, strong injection and strong production are mainly adopted. Under this kind of large volume of liquid scouring, the microscopic pore structure of reservoir and the efficiency of water drive oil are changed, which brings difficulty to understanding the law of water drive development in high water cut stage of oilfield. Through simulating long⁃term water flooding and scouring physical experiments, the variation law of each characteristic parameter of reservoir during the long term water flooding scouring process is studied. The results show that for high porosity and high permeability reservoirs after long⁃term water flooding, the porosity change is not obvious, permeability is obviously increased, and invalid circulation channels are easily formed. The characteristics of pore microcosmic change are obvious, the radius of pore throat increases and the seepage ability increases. With the increase of displacement ratio, the isosmotic point shifts to the right. When the water saturation is the same, the oil phase permeability increases, the water phase permeability decreases, the residual oil saturation decreases, and the oil displacement efficiency increases by nearly 10%. The research results have been used in the field test of 2 000 m3/d liquid production per well in offshore sandstone reservoirs with high water cut, which provides theoretical support for the formulation of development strategy in high water cut period of offshore oil fields.

Key words: Offshore loose sandstone reservoir, High water cut stage, Microcosmic, Pore structure, Relative permeability curves, Fluid producing intensity

摘要： 海上稠油油田开发中后期主要采用强注强采开发方式，在这种大液量冲刷下储层微观孔隙结构及水驱油效率发生变化，给油田高含水期的水驱开发规律认识带来了难度。通过物理模拟实验方法，研究了储层在长期注水冲刷过程中的各特征参数变化规律。结果表明，对于高孔高渗储层经过长期注水冲刷后，孔隙度变化不明显，渗透率明显增大，易形成无效循环通道；孔隙微观变化特征明显，出现孔喉半径增大、渗流能力增强的变化规律；随着驱替倍数增加，等渗点右移，残余油饱和度下降，驱油效率提高近10%。研究成果验证了海上陆相疏松砂岩油藏特高含水期产液量2 000 m3/d的先导试验，为海上油田高含水期开发策略的制定提供了理论支持。

关键词: 海上疏松砂岩, 高含水期, 微观, 孔隙结构, 相渗曲线, 产液强度