高温高压凝析气藏石蜡沉积条件预测研究

Study on prediction of wax deposition conditions in high temperature and high pressure condensate gas reservoir

高温高压凝析气藏地层到地面的流动保障对开发至关重要。针对高温高压凝析气藏含有较高重烃,开发过程中容易出现石蜡沉积,而实验测试往往费时复杂的问题,提出了基于简单的实验和相平衡热力学模型相结合进行石蜡沉积条件预测的新方法。以南海西部某凝析气藏为例,利用PVT仪测试凝析气高温高压相态特征,通过差热扫描仪测试地面凝析油石蜡沉积温度。基于气液固三相相平衡热力学模型,在拟合地面凝析油石蜡沉积点和高温高压凝析气相态基础上,预测地层凝析气流体石蜡沉积点和沉积量。研究凝析气气—液—固三相相态特征和石蜡沉积的温度压力规律。结果显示:气液固三相热力学模型结合实验可以很好的预测凝析气的石蜡沉积和气液固三相相态特征;YC13-1地面油当温度大于30℃后,压力需要高于60 MPa才可能有石蜡沉积。压力降低,析出蜡的量逐渐增加,在大气压的时候,析出的蜡的重量比重约0.45%。高温条件下,该凝析气难以出现石蜡沉积,但在地面输送过程中需重点考虑石蜡沉积。该方法对其它类似凝析气体系的石蜡沉积预测具有重要指导意义。

It is important for the exploitation in protecting the flow of the high temperature and high pressure condensate gas reservoir formation to the surface. In view of problems of wax deposition in the exploitation process of the gas reservoir with high heavy hydrocarbon and prone under high temperature and high pressure the test is often time consuming. A new method of paraffin deposition prediction was proposed based on the combination of simple experiment and phase equilibrium thermodynamic model. Taking a condensate gas reservoir in the west of the South China Sea as an example, the test of the phase characteristics of condensate gas under high temperature and high pressure by PVT instrument and Paraffin deposition temperature of ground condensate through differential thermal scanners was carried. Based on the thermodynamic model of vapor-liquid-solid phase equilibrium and fitting the paraffin wax deposition point of ground condensate and the high temperature and high pressure condensate gas phase, the paraffin deposition point and the wax deposition amount of condensate gas were predicted. Analysis of the condensate gas phase characteristics and gas-liquid-solid three phase of paraffin deposition temperature and pressure conditions. Research results show that the gas-liquid- solid three-phase thermodynamic model combined with experiments can be a good predictor of condensate gas paraffin deposition and gas-liquid-solid phase characteristics. When the temperature is greater than 30 ℃, the pressure needs to be higher than 60 MPa then YC 13-I ground oil may have wax deposition. The pressure was decreased while the amount of precipitated wax was gradually increased. At atmospheric pressure, the weight ratio of the precipitated wax was about 0.45 %. While under high temperature, the wax deposition is hard to apper in the condensate gas. But it is still to be considered during the ground transportation process, This method has important guiding significance for the wax deposition prediotion of the other similar condensate gas systems.