注富烃气凝析/蒸发混相驱机理评价

基于状态方程和气液两相相平衡理论,建立了注气压力组成及多级接触实验相平衡的计算模型,再应用建立的计算模型,根据室内注气配套实验(压力组成实验、多级接触实验、细管实验)数据,模拟压力-组成相图、多级接触拟三元相图和细管特征曲线,评价注气驱混相能力及驱替机理。应用该方法对吐哈盆地丘陵油田注富烃气混相驱机理进行了评价,研究了该过程中油气两相中的C1、C2-C6和C7-组分、界面张力、密度与黏度等特性参数的变化规律,证实了注富烃气驱替过程中存在凝析和蒸发双重作用,因此在较低界面张力状态(即近混相)下采收率可以达到与混相驱接近的效果,认为凝析／蒸发混相就是近混相的提法不妥。图5表1参12

Mechanism evaluation of condensing/vaporizing miscible flooding with hydrocarbon-rich gas injection

Based on the EOS and the phase equilibrium theory of oil-gas systems, the calculation models for pressure-composition experiment and multi-contact miscible experiment of gas injection were built. And a systemic evaluation method was proposed,which applies the existing work tools (component simulator) to simulate the PVT experiment data, pressure-composition experiment, multiple contact miscible experiment and slim-tube experiment available to evaluate the miscible ability and mechanism of gas displacement. The miscible mechanism of hydrocarbon-rich gas injection in Qiulin Oilfield, Tuha Basin, was evaluated. The results approve the existence of the combined condensing/vaporizing mechanism in hydrocarbon-rich gas displacement and show that the evaluation method by extending the experimental data presented here can provide a reliable theoretical basis for the design of miscible gas injection project in oilfield. The recovery under relatively low interfacial tension, i.e, near miscible flooding, is near to that of miscible flooding.