过量地层水影响深层凝析气相态机理及基于GE-EOS模型的相态模拟研究

Because of the understanding on mechanism of deep gas condensate phase behavior affected by excessive formation water is not very clearly, there’re some unreliable in GIIP calculation and the development plan design. In this study, the question of would be aimed, and the deep gas condensate with excessive formation water would be selected as the research object. Combined the experimental research, theoretical research with simulation research, using the reservoir fluid phase behavior theory, experimental method, chemical thermodynamics theory, numerical method, and computer technology, a suit of phase behavior experimental method for deep gas condensate with excessive formation water would be established. Based on the experimental research considering different formation water ionic component, formation water ionic concentration, gas condensate component and gas condensate composition, the mechanism on gas condensate phase behavior with excessive formation water would be revealed. Based on the GE-EOS model, the phase behavior simulation model for deep gas condensate with excessive formation water would be founded, and the phase behavior variation law would be understood clearly. The research result has important theoretical and applied values for researching on the percolation law of deep gas condensate reservoir deeply and improvement the ability of gas reservoir development plan design.

因对过量地层水影响深层凝析气相态机理认识不清，导致该类气藏储量计算和开发设计存在不可靠。本研究针对目前对过量地层水影响深层凝析气相态机理认识不清的问题，选取含过量地层水的深层凝析气体系为研究对象，采用实验研究、理论研究和模拟研究相结合的研究思路，综合运用油气藏流体相态理论及实验方法、化工热力学原理、数值计算方法和计算机技术等多学科理论和方法，建立一套考虑过量地层水的深层凝析气相态实验方法；在考虑地层水离子组成、地层水离子浓度、凝析气流体组分及凝析气流体组成变化的相态实验研究基础上，揭示过量地层水影响深层凝析气相态的机理；最后基于GE-EOS模型，建立考虑过量地层水的深层凝析气相态模拟模型，明确过量地层水影响深层凝析气相态变化规律。研究成果对于深入研究深层凝析气藏的渗流规律，提高气藏的开发设计水平具有重要的理论和应该价值。

项目围绕拟解决的科学问题，建立了考虑过量地层水的小体积反凝析油体积实验测试方法。根据调研确定的深层凝析气藏典型组成，开展了考虑不同地层水水型、矿化度和流体组成的过量地层水-凝析气体系PVT实验测试，通过实验分析得出了过量地层水影响深层凝析气相态的主要机理是：过量地层水-凝析气体系压降过程，H2O组分被抽提至反凝析液中，从而增加反凝析液饱和度；同时，受抽提作用的影响，地层水矿化度增加，导致水中溶解天然气析出，增加体系轻质组分含量，从而影响体系相态。.明确过量地层水影响凝析气体系相态机理后，综合应用油气藏流体相态理论和化工热力学原理，优选PR状态方程，并引入HV吉布斯能量模型修正了混合规则参数，从而建立了过量地层水-深层凝析气体系相态模拟模型。并对模型进行求解，编制了相态模拟器，模拟得到过量水影响凝析气变化规律为：（1）地层水水型不会影响相态规律；（2）地层水矿化度对体系相态规律影响较小，基本规律为矿化度越高体系饱和压力越高、反凝析液量降低；（3）过量水饱和度大小不会影响体系饱和压力；（4）过量水饱和度越大，体系反凝析液饱和度越大，且低压时比高压时增加幅度要大，当饱和度大于一定程度后倾向于稳定。项目研究成果对于深层凝析气藏开发技术对策确定、开发方案编制具有重要的指导意义，可为深层凝析气藏提高凝析油和天然气采收率提供理论支撑。