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深入认识低渗透储层的渗流特征,对如何经济有效开发低渗透油田具有重要指导意义。应用1米长露头岩心渗流模拟系统,研究了低渗透岩心单相渗流过程、恒压水驱油过程中压力动态传播特征,克服了短岩心模拟过程中产生的端面效应,较真实的反映了低渗透储层的渗流特征。低渗透长岩心单相水渗流实验表明,低渗透储层由于应力敏感效应导致渗透率沿渗流方向降低。储层渗透率并非常数,而是孔隙流体压力的函数。低渗透储层内部压力分布呈非线性特征,生产压差越大,岩心内部压力分布的非线性程度增强。压力损失因应力敏感效应主要消耗在生产井近井地带,越靠近生产井,压力分布的非线性程度越明显。恒压水驱油过程中,渗流阻力主要损失在油水两相区。在油水前缘到达各测压点之前,其压力逐渐下降,油水前缘通过该点后,其压力逐渐上升。
Understanding deeply the seepage characteristics of low permeability reservoirs has important guiding significance for how to develop low permeability oil fields economically and effectively. In this paper, a 1-meter-long outcrop core flow simulation system is applied to study the dynamic characteristics of pressure propagation in low-permeability core during single-phase seepage process and constant-pressure water flooding process, which overcomes the end effect produced in the short core simulation process, Percolation reservoir seepage characteristics. Experimental results of single-phase water seepage in low-permeability long core show that the permeability of low-permeability reservoirs decreases along the direction of seepage due to stress-sensitive effect. Reservoir permeability is not a constant but a function of pore fluid pressure. The pressure distribution in the low permeability reservoir shows a nonlinear characteristic. The larger the production pressure difference, the more nonlinear the pressure distribution inside the core. Pressure loss due to stress-sensitive effect is mainly consumed in the production well near the wellbore, the closer to the production wells, the pressure distribution of the more obvious non-linearity. In the process of constant pressure water flooding, the main loss of seepage resistance is in the oil-water two-phase zone. Before the oil-water front arrives at each pressure-measuring point, the pressure gradually drops. After the oil-water front passes this point, the pressure gradually rises.