Abstract:

Aiming at the problem of wax deposition in gas well exploitation of offshore HPHT gas reservoir, the gas?liquid?solid and fluid phase equilibrium theory and method of throttling effect principle was used to reveal the wax deposition mechanism of the abnormal high temperature and high pressure gas well, and it was found that wax deposition in high temperature and high pressure gas wells mainly occurs at the position of the oil nozzle where the temperature drops sharply when the wing valve of the gas well is closed. According to the phase equilibrium theory, the phase state of the original formation fluid in HPHT gas well was recovered and characterized, and the phase state change characteristics of gas?liquid?solid three?phase fluid, wax precipitation mechanism and process were described accurately. Based on the phase equilibrium model, the wax location, fluid composition change and the influencing factors of wax deposition were analyzed. It was reasonable to explain that the mechanism of wax precipitation in HPHT gas well is the transient phase transition from gaseous to liquid and then to solid due to the rapid change of temperature and pressure, and the corresponding prevention and control strategies are put forward.

Key words: High temperature high pressure （HPHT）, Wax deposition, Phase equilibrium, Fluid phase, Prevention and control strategy

摘要：

针对海上高温高压气藏气井开采过程中结蜡的问题，采用气?液?固流体相平衡理论及节流效应原理，分析了海上异常高温高压气井析蜡机理，发现高温高压气井蜡沉积主要发生在关闭气井翼阀瞬间温度急剧降低的油嘴位置处。根据相平衡理论，对高温高压气井原始地层流体进行了相态恢复和表征，准确描述了气?液?固三相流体相态变化特征、蜡的析出机理和析出过程。依据相平衡模型分析了气井结蜡位置、流体组分组成变化和结蜡的影响因素，合理解释了高温高压气井析蜡机理是温度压力急剧变化导致流体由气态向液态，再向固态瞬时相变的过程，并提出了相应防治策略。

关键词: 高温高压, 蜡沉积, 相平衡, 流体相态, 防治策略