高含硫气藏井筒硫沉积机理研究

At present, sulfur deposition mechanism of high-sulfur wellbore study mainly focused on testing the solubility of sulfur, which considered sulfur reach saturation that precipitated sulfur deposition, without considering the diffusion, adsorption, dynamic deposition mechanism of interaction with the wall. Existing models had used empirical equations with experimental data regression and phase model to predict the wellbore sulfur deposition, combined with sulfur-carrying to determine whether the sulfur of wellbore had deposited or not, which did not correspond to the actual dynamic wellbore sulfur deposition mechanism. Therefore, the project has proposed method of sulfur diffusion coefficient with high temperature and high pressure gas wellbore of sulfur deposition, studied on diffusion processes of S/H2S/CO2/N2/CH4 in high-sulfur gas and liquid sulfur, and focused on elemental sulfur precipitation, diffusion, adsorption, nucleation growth process by using microscopic visualization of sulfur deposition, experiment testing device, quantified the changes of sulfur nucleation conditions, growth rate, sulfur deposition thickness and other parameters in sulfur deposition. On the basis of simulation experiments, establishing dynamic prediction model of sulfur deposition wellbore which consider with wellbore phase transition, fluid state diffusion and adsorption of the gas reservoirs with high sulfur content, and predict the rate of wellbore sulfur deposition, the change of thickness with time, so that provide the basis for the study of the mechanism of high sulfur gas wellbore dynamic deposition.

目前对高含硫井筒硫沉积机理研究主要集中在测试硫的溶解度，认为气体中硫达到饱和状态即析出沉积，没有考虑扩散、吸附、与管壁相互作用的动态沉积机理；现有模型采用实验数据回归的经验公式和相态模型来预测井筒硫沉积问题，并结合携硫模型判别井筒硫是否沉积，和实际井筒硫动态沉积机理不相吻合。因此，本项目提出了高温高压高含硫气井井筒硫沉积扩散系数的测试方法，研究S/H2S/CO2/N2/CH4在高含硫气体及液态硫中的扩散过程，利用微观可视化硫沉积实验测试装置，研究元素硫析出、扩散、吸附、形核生长过程，量化硫沉积过程中硫形核条件、生长速率、硫沉积厚度等参数的变化。在模拟实验的基础上，建立综合考虑井筒相变、流态、扩散及吸附影响的高含硫气藏井筒硫沉积动态预测模型，预测井筒硫沉积速度、硫沉积厚度随时间的变化规律，为研究高含硫气田井筒硫动态沉积机理提供依据。

目前对高含硫井筒硫沉积机理研究主要集中在测试硫的溶解度，认为气体中硫达到饱和状态即析出沉积，没有考虑扩散、吸附、与管壁相互作用的动态沉积机理；现有模型采用实验数据回归的经验公式和相态模型来预测井筒硫沉积问题，并结合携硫模型判别井筒硫是否沉积，和实际井筒硫动态沉积机理不相吻合。.本项目提出了高温高压硫沉积扩散系数测试装置和方法，研究了元素S在H2S/CO2/N2/CH4气体中的扩散过程，建立了高温高压下单质硫在不同气体组分中的扩散系数方程，利用发明的微观可视化硫沉积实验测试装置和分子模拟技术，研究了元素硫析出、扩散、吸附、形核生长过程，指出了硫沉积存在多种机理：流体内部均质成核或异质成核、流体与管壁异质结晶、液态硫与管壁粘附等，直接在管壁上结晶沉积的硫属于化学吸附，而气流中硫微粒在管壁上属于物理吸附。若单质硫从地层出来为固态，在一定流速下单质硫就能够被携带出井筒，若井筒中为液态硫，液硫优先吸附在管壁有晶核诱导的位置，很难被气流带走；若井筒中单质硫直接从气体析出吸附在管壁上，沉积的硫很难清除。同时建立了高含硫天然气中硫单质析出的临界形核预测模型及管壁微粒粘附剥离力学模型。在模拟实验的基础上，建立了综合考虑井筒相变、流态、扩散及吸附影响的高含硫气藏井筒硫沉积动态预测模型。对普光气田元素硫沉积预测表明，井筒流体内部析出硫微粒的可能性非常小，但在地面管线和设备中很容易析出硫微粒，井筒硫沉积主要为硫在管壁上的异质结晶沉积。同时发现了井筒硫沉积伴随腐蚀，并与天然气和凝析水发生了化学反应，生成了碳，使得样品呈黑色，形成机理不清楚。