胜利油田低渗透水驱油藏含水变化特征及影响因素

生产中含水率的变化特征在一定程度上可以反映水驱油效果的好坏。见水早、含水上升快、水驱油效率低等问题一直困扰着低渗透油藏开发。水驱油藏含水率的变化问题属于岩石中油水两相渗流的范畴，含水变化特征必然决定于岩石物性、油水特征和驱动力等因素。针对胜利油田低渗透水驱油藏，通过大量实验数据分析了储层孔隙结构特征、原始含水饱和度、应力敏感性和驱替压力等因素对含水率变化和水驱油效率的影响。研究发现孔隙的连通性是影响含水上升规律的重要因素，而初始含水率主要是由原始含水饱和度决定，适当的控制驱替压力有利于控制含水率，提高水驱油效率。考虑到低渗透储层渗透率的应力敏感性，建议实施超前注水，避免压力下降造成的渗透率伤害，从而利于提高水驱油效率。

Characteristics and influential factors of water cut change in low permeability water-drive oil reservoirs in Shengli oilfield

The characteristic change of water cut can reflect the effectiveness of waterflooding to some extent.Early water breakthrough,fast water cut rise,and low efficiency of waterflooding have always been the obstacles preventing the development of low permeability reservoirs.Variation of water cut in waterflooding oil reservoirs involves two-phase flow of oil and water in rocks,thus is controlled by petrophysical property,oil-water features and driving force.In regard to the low permeability water-drive oil reservoirs in Shengli oilfield,we analyzed the factors influencing the variation of water cut and waterflood efficiency based on larges amounts of experimental data.These factors are characteristics of reservoir pore structure,original water saturation,stress sensitivity and displacement pressure.The results show that pore connectivity is the major factor for water cut rising,while the initial water cut mainly depends on original water saturation.Appropriate control on displacement pressure is beneficial for controlling water cut and increasing waterflood efficiency.Considering the stress sensitivity of permeability in low permeability reservoirs,we suggested the implementation of advanced water injection to avoid the permeability damage caused by pressure drop,so as to improve waterflood efficiency.