低渗碳酸盐岩稠油油藏启动压力梯度研究

The Starting Pressure Gradient Research of Low Permeability Carbonate Heavy Oil Reservoir

采用"压差-流量"法测定了3个渗透率级别、3个原油黏度级别条件下的低渗透碳酸盐岩油藏样品的非达西渗流曲线。得到不同黏度、不同渗透率条件下叙利亚O油田的油相启动压力梯度及流量-压差关系,分析认为原油黏度和渗透率对低渗透碳酸盐岩稠油油藏启动压力梯度影响明显;通过对实验结果进行非线性回归,得到适用于低渗碳酸盐岩稠油油藏的启动压力梯度与流度关系的经验公式及关系图版;通过加热测定高温对启动压力梯度影响,与冷采条件下相比,高温条件下低渗碳酸盐岩稠油油藏油相启动压力梯度可下降约1个数量级,从而有效改善了原油在地层的渗流能力,但高温改变启动压力梯度存在临界温度。该研究成果为低渗碳酸盐岩稠油油藏开发方式优选及热采参数优化提供了理论支持。

For the low permeability heavy oil reservoir,fluid flow feature is non-Darcy flow characteristics because of the formation＇ s low permeability and the high viscosity of crude oil.The starting pressure gradient is existed in this type reservoir.According to the percolation characteristics of low permeability heavy oil reservoir,a reasonable experimental method was designed so as to measure the starting pressure gradient of low permeability heavy oil reservoir.The starting pressure gradient and the relationship between velocity and pressure gradient under irreducible water saturation was studied through various percolation experiments at different permeability,viscosity and temperatures conditions with the natural carbonate cores from Syria O oilfield Sh reservoir.Through experimental data regression,the empirical formula between the starting pressure gradient and mobility was established,which is suitable for the low permeability carbonate heavy oil reservoir.The experimental results show that：the influences of oil viscosity and permeability on starting pressure gradient are similar between the low permeability carbonate heavy oil reservoir and sandstone ordinary heavy oil reservoir.Both of their starting pressure gradient have the power-law relationship with their mobility.The starting pressure gradient of low permeability carbonate heavy oil reservoir is higher than that of the high permeability sandstone heavy oil reservoir,up to 1 order of magnitude.Through thermal process,the oil phase starting pressure gradient decreased obviously,and there is a critical temperature.The research provides a theoretical supporting for the optimization of development mode and thermal recovery parameter optimization of the low permeability carbonate heavy oil reservoir.