元坝长兴组储层温度分布对液硫析出的影响

元坝地区长兴组气藏属于超深类高温、高压、高含硫的三高气藏,目前生产制度下的井底温度、压力条件远高于硫元素固态熔点条件且即将低于酸气析出硫的临界条件.因此在较长的生产过程中,井底温压条件下酸气析出硫呈现液态.现有的硫析出模型均建立在等温储层的基础上,为了探究储层温度分布对酸气液硫析出的影响规律,基于实验测试数据建立了非等温液硫析出及预测模型,对比分析了等温储层和非等温储层液硫析出的差异性.结果 表明:相比于恒温储层,储层到井筒之间温度的降低会导致酸气中液硫析出提前发生;不考虑储层-井筒温度的分布情况,将会低估液硫析出的压力条件;储层等温分布条件下的液硫析出范围计算结果偏小,储层-井筒温度的非均匀分布会加剧近井附近的液硫沉积量.高含硫气藏储层到井筒之间的温度分布对硫析出条件、析出范围、析出量的影响明显,应当充分考虑储层温度的分布特征,不可以"等温储层"的假设来简单处理.

Characteristics of the Influence of Reservoir Temperature Distribution on Liquid-sulfur Condensation in Changxing Formation Gas Reservoirs

Changxing Formation gas reservoir in the Yuanba area is an ultra-deep gas reservoir with high temperature, high pressure, and high sulfur content. The current bottom-hole temperature and pressure conditions are higher than the solid-sulfur melting point and lower than the liquid-sulfur condensation point. Therefore, the condensed sulfur is liquid under current bottom-hole conditions. The existing sulfur condensation models are all based on isothermal reservoirs. To explore the influence of reservoir-wellbore temperature distribution on liquid-sulfur condensed by sour gas, non-isothermal liquid-sulfur condensation model was established based on experimental test data. The difference in liquid-sulfur condensation between isothermal and non-isothermal reservoirs was analyzed. The results as follows. First, compared with isothermal reservoirs, the temperature decrease from the reservoir to wellbore will cause the liquid-sulfur condensation to occur earlier. Second, ignoring the temperature distribution of reservoir-wellbore, the condensation pressure of liquid-sulfur will be underestimated. Third, the assumption of the isothermal reservoir will underestimate the range of condensed liquid-sulfur in the reservoir, and the uneven temperature distribution will increase the volume of condensed liquid-sulfur near the well. It is concluded that temperature distribution between the reservoir and wellbore will affect the liquid-sulfur condensation conditions, condensation scope, and condensation volume. The reservoir-wellbore temperature distribution should be fully considered, and the assumption of isothermal reservoir cannot be simply used to predict high-temperature and high-sulfur gas reservoirs.