酸气回注井筒流动模型

将酸气压缩后回注到已废弃的产层或水层中，逐渐成为石油和天然气工业有效减少环境污染的方法之一。酸气回注不仅可缓解目前硫磺生产和需求的矛盾，而且可利用硫化氢和二氧化碳作为提高采收率措施的气源。酸气回注不同于常规的注水或注天然气，涉及到复杂的相态转变以及相应的流体物理性质（如密度和粘度的变化）。因此，与压力、温度和流体组成相关的相态是决定井内流动压力剖面的关键因素，如何选取适当的状态方程至关重要。文章针对目前研究存在的不足，结合Patel Teja三参数状态方程和修改的Peng Robinson状态方程预测酸气在不同相态下的密度和粘度，建立了井内流体流动的数学模型，用四阶龙格-库塔法对该模型进行了求解，然后用现场实测数据对模拟结果进行了验证和比较，并讨论了相态对流体物理性质和注入压力剖面的影响。

WELLBORE FLOW MODEL OF ACID GAS REINJECTION

The compressed acid gas reinjection into aba ndoned payzone or aquifer has gradually become one of the effective methods of r educing environmental pollution in oil and gas industry. The acid gas reinjectio n may alleviate the contradiction between sulfur production and sulfur demand at present, and the acid gas may be used as the gas source of the enhanced oil rec overy measure. The acid gas reinjection is different from the conventional water injection and natural gas injection, and it involves the complicated phase tran sformation and relevant fluid physical properties (as the changes in density and viscosity). The phase behavior related to the pressure, temperature and fluid c omposition is the key factor of deciding wellbore flow pressure profile, therefo re how to select the proper state equations is very important. In the paper, in consideration of the shortcomings existing in current study, the densities and v iscosities of the acid gas at different phase behaviors are predicted by use of the Patel-Teja three-parameter state equation and modified Peng-Robinson stat e equation respectively; a mathematical model of wellbore fluid flow is set up a nd solved by the fourth-order Runge-Kutta integration; then the simulation res ults are verified and contrasted with the field data; and then the effects of ph ase behaviors on fluid physical properties and injection pressure profile are di scussed finally.