摘要
为了研究特低渗透储层渗流特征及影响因素,以鄂尔多斯盆地白豹油田为例,对特低渗透岩心的单相和两相渗流特征进行分析。结果表明,特低渗岩心单相渗流具有拟启动压力梯度,渗透率越小,拟启动压力梯度越大;其渗流曲线不再为一条直线,而为下凹型曲线,呈现非达西渗流特征;其流变曲线不是直线,而为上凸型曲线,流体为非牛顿假塑性流体,在较小外力作用下不发生流动,只产生弹性变形,只有当外力大于某值时,流体才发生流动,且具有明显的屈服应力;动极限剪切应力与渗透率的关系表明,动极限剪切应力随渗透率减小而急剧增大;随着剪切速率的增大,视黏度逐渐降低,在剪切作用之后,流体浓度具有变小的特性;油水两相渗流曲线说明束缚水饱和度和残余油饱和度偏高,共渗区较窄,且随着含水饱和度增大,油相渗透率快速下降,水相渗透率缓慢增长。岩心的渗透率大小、润湿性、水锁等因素均对渗流特征有影响。
In order to study seepage characteristics and influencing factors in ultra-low permeability reservoirs,with samples taken from Ordos,experiments of single phase flow and oil-water phase flow were conducted.The results indicate there exists a threshold pressure gradient for single phase flows for part of samples.The flow is of non-darcy seepage when the pressure gradient is low and it changes into darcy flow at high pressure;but for other samples,no obvious non-darcy flow is found.The lower the core permeability is,the higher the pressure under which non-Darcy state will retain and less the flow volume will be.The flow curve for the core is not a straight line but a curve protruding to the shearing stress axis.The fluid is non-Newtonian and fake plastic fluid,which does not move besides some elastic deformation under a weak external force,and which moves under a strong external force,with an obvious yield stress.The relation between moving shearing stress and permeability indicates that the shearing stress decreases rapidly with the decrease of permeability.The apparent viscosity reduces slowly when the shearing rate increases The density of the fluid decreases after shearing.Irreducible water saturation and residual oil saturation become high and the two-phase region becomes narrow under the condition of two-phase seepage.The relative permeability value of oil-phase reduces quickly and the water-phase increases slowly with the increase of water saturation.The permeability,wettability and water-lock influence the seepage characteristics.
出处
《科技导报》
CAS
CSCD
北大核心
2011年第1期36-39,共4页
Science & Technology Review
基金
国家重点基础研究发展计划(973计划)项目(G199902250)
关键词
特低渗透储层
启动压力梯度
单相渗流
非达西渗流
ultra-low permeability reservoirs
threshold pressure gradient
single phase flow
non-Darcy flow
