近临界态凝析气藏地层流体特殊相态行为

以一种典型的近临界凝析气藏地层流体为研究对象，利用可实时监测录像的可视化DBR-PVT实验装置,开展了不同温度下地层流体在近临界区的超临界态奇异临界乳光现象观测实验、等组成膨胀实验以及注CO₂增溶膨胀相态配伍性实验研究。通过对近临界区超临界乳光现象的观测，发现在超临界温度压力区域内受超临界流体密度涨落的影响，在背景光源照射下流体会呈现出“临界乳光”折射现象，从透明的金黄色渐变为浅棕色、红棕色，最后转变为完全不透光的灰黑色，整个过程具有强烈的乳光特征；通过不同温度下的等组成膨胀实验，测试了超临界区地层流体的饱和压力、偏差因子、黏度、密度、反凝析液量变化特征和临界点的p-T范围；通过注CO₂增溶膨胀实验，测试了不同比例CO₂与凝析油混溶情况下，凝析油饱和压力的变化情况。所得实验结果为进一步研究近临界复杂流体的超临界相态特征及超临界区热力学模型的适应性,提供了有价值的基础数据。

Dynamic phase behavior of near critical condensate gas reservoir fluids

In order to study a typical fluid in a near critical condensate gas reservoir, we introduced a visual DBR-PVT measurement system capable of real time monitoring. Then, studies were conducted via the following experiments of observing singular critical opalescence of formation fluids under different temperatures at the supercritical state in the near critical region, CCE (constant composition expansion), and phase compatibility test via CO₂ induced swelling (solubilization). By observing the supercritical opalescence in the near critical region, we discovered a refraction of “critical opalescence” under the background light and the fluctuation of supercritical fluid density within the range of supercritical temperature and pressure. The opalescence changed from transparent golden yellow into light brown and reddish brown, and finally into completely opaque dark gray, which was a typical process with strong opalescence features. In the CCE experiment at different temperatures, parameters of formation fluids in the supercritical region were tested, including saturation pressure, deviation factor, viscosity, density, and the change features of retrograde condensate, and the p-T range at the critical point was also obtained. In the CO₂induced swelling experiment, the saturation pressure change of condensate oil was tested with miscible solutions of different proportions of CO₂ and condensate oil. The above experiment results provide valuable basic data for further studying the supercritical phase behavior of critical complex fluids and the adaptability of the thermodynamic model in the supercritical region.