存在液流析出的超深高含硫气藏压力响应特征

Pressure response characteristics of ultra-deep and high-sulfur gas reservoirs with liquid sulfur condensation

目前高含硫气藏硫元素研究主要以固硫沉积引起的储层伤害为主,鲜有超深高含硫气藏液硫析出后储层压力动态特征方面的报道。考虑超深高含硫气藏的液硫析出及流动特征,建立了表征存在液硫析出及流动的多区径向复合储层渗流模型,讨论了液硫聚集、流动及冲刷模式下的储层含硫饱和度以及储层渗透率变化规律,分析了不同液硫析出阶段下的储层压力响应特征。研究结果表明:多区径向复合储层渗流模型能够有效表征液硫析出后储层气体渗流特征,根据压力导数曲线特征可以识别储层液硫析出的不同阶段。液硫析出早期,压力导数曲线成“连续下降”台阶状;液硫析出中期,压力导数曲线成“先小降、后大降”的台阶特征;液硫析出后期,压力导数曲线为“先小升、后大降”的台阶特征。研究结果可为超深高含硫气藏液硫析出模式的诊断提供理论依据。

The current research of sulfur in high-sulfur gas reservoirs is mainly based on the reservoir damage caused by the sulfur deposition,and there are few reports on the dynamic characteristics of the reservoir pressure after the liquid-sulfur condensation in the ultra-deep and high-sulfur gas reservoirs.Considering the condensation and existence state of liquid-sulfur,a multi-zone radial composite reservoir seepage model was established to characterize the condensation and flow of liquid-sulfur.The distribution of reservoir permeability,liquid-sulfur saturation,and pressure response under different stages of liquid-sulfur condensation are analyzed.The research results show that the multi-zone radial composite reservoir seepage model can capture the gas seepage feature after the liquid sulfur condensation,and based on the pressure response derivative type curve can identify the different stages of the liquid-sulfur condensation.At the early stage of liquid sulfur condensation,the derivative curve of pressure is“continuously descending”;At the middle stage of liquid sulfur condensation,the pressure derivative curve shows a step characteristic of“small drop at first and then big drop”;At the late stage of liquid sulfur condensation,the pressure derivative curve shows a step characteristic of“small rise at first and then big drop”.The research results can provide a theoretical basis for the diagnosis of the liquid-sulfur condensation stage in ultra-deep and high-sulfur gas reservoirs.