低流度稠油油藏启动机制及主控因素实验研究

Experimental Study on Start-up Mechanism and Main Controlling Factors of Low-Mobility Heavy Oil Reservoir

借助低流度稠油启动过程中沿驱动方向的压力跟踪测试,分析了启动的物理过程,评价各种测试方法的适应性,研究了温度、流度、驱动速度等对启动压力的影响规律,并回归检验了低流度稠油启动压力的算法模型。结果表明:稠油的启动是一个“压力传递—稠油部分流动—逐步扩大流动范围—整体稳态流动”的过程;对于低流度稠油油藏,传统启动压力测试方法会存在启动压力梯度值放大情况,通过测试岩心内部压差变化,可以规避端部效应对其影响,使得启动压力梯度测试更加精准;整体上启动压力梯度会随着驱动排量增大、流度减小、温度降低而呈现增大趋势,各因素影响敏感性上三者依次变弱;大流度、高温度下,启动压力梯度与驱动排量呈线性增大规律,在小流度、低温度下,启动压力梯度随着排量的增加存在明显拐点,其后启动压力梯度快速增大。低流度稠油开发过程中不宜采用大排量高压式注入方式,应当温和渐进式的驱替方式进行高效合理的开发。所回归的启动压力计算模型可综合考虑流度和排量的影响,可为低流度稠油油藏水驱开发方案设计提供借鉴。

With the help of the pressure tracking testing along the driving direction during the start-up process of low mobility heavy oil,the physical process of start-up is analyzed,the adaptability of various start-up pressure test methods is evaluated,the influences of temperature,mobility,driving speed,etc.on the start-up pressure are studied,and the start-up pressure calculation model of low mobility heavy oil is regressed.The results show that the start-up of heavy oil is a process of"pressure transmission-partial flowing of heavy oil-gradual expansion of flowing range-overall steady flowing".For the low mobility heavy oil reservoir,the traditional startup pressure testing methods will make the startup pressure gradient value amplified.By testing the change of the internal pressure difference of rock core,the impact of the end effect can be avoided,making the startup pressure gradient test more accurate.On the whole,the start-up pressure gradient will increase with the increase of driving displacement,the decrease of mobility and temperature,and the sensitivity of the start-up pressure gradient to driving displacement,mobility and temperature will become weaker in turn.The start-up pressure gradient increases linearly with the driving displacement at large mobility and high temperature.At small mobility and low temperature,the varying curve of the start-up pressure gradient with the increase of driving displacement has an obvious inflection point,and the starting pressure gradient increases rapidly after the inflection point.Therefore,high pressure injection with large displacement should not be adopted in the development of low mobility heavy oil reservoirs,and moderate displacement mode should be adopted for efficient and reasonable development.The regressed start-up pressure calculation model comprehensively considers the influence of mobility and driving displacement,and can provide reference for water flooding development scheme design of low mobility heavy oil reservoirs.