高压含硫天然气水合物预测方法与防治措施研究

Analysis on Prediction Method and Prevention Measures of High Pressure Sour Natural Gas Hydrate

以相平衡热力学理论为基础,建立适用于水、醇、酸气体系的天然气水合物热力学模型,研究气体溶解度在酸性介质水、醇体系相平衡条件下的变化规律,以及含硫量和醇对高压酸性天然气水合物形成条件的影响规律。研究结果表明:在温度264.9~311.64 K、压力0.56~186.2 MPa的100组实验数据中,天然气水合物形成条件与实验值的平均绝对偏差分别小于1 K和5.86 MPa,其精度高于PR和SRK状态方程预测值,高浓度范围内甲醇和乙二醇质量浓度变化引起的水合物生成温度下降速率大于低浓度范围。当富水相中甲醇或乙二醇液的质量分数在60%~70%范围内变化时,水合物生成温度的下降速率最大。以高压含硫气井麟3井为例,针对三种工况制定了水合物抑制措施,确定了热力缓蚀剂的加注量和加注浓度,可避免水合物冰堵,在各级节流过程中使用效果显著。

Based on the theory of phase equilibrium thermodynamics,this paper establishes a thermodynamic model of natural gas hydrate applicable to water,alcohol and sour gas systems,and studies the variation law of gas solubility under the phase equilibrium conditions of water and alcohol systems in acidic media,as well as the influence law of sulfur content and alcohol on the formation conditions of high-pressure acidic natural gas hydrate.Results show that the average absolute deviation of natural gas hydrate formation conditions from the experimental values is less than 1 K and 5.86 MPa in 100 sets of experimental data from 264.9 K to 311.64 K and 0.56 MPa to 186.2 MPa,respectively,and its accuracy is higher than the predicted values of PR and SRK equation of state,and the temperature drop of hydrate formation caused by the change of methanol and ethylene glycol mass concentration in the high concentration range is greater than that in the low concentration range.When the mass fraction of methanol or glycol liquid in the water-rich phase varies in the range of 60% to 70%,the rate of hydrate formation temperature drop is the largest.Taking high-pressure sulfur-bearing gas well Lin 3 Well as an example,hydrate suppression measures are developed for three working conditions,and the filling amount and filling concentration of thermal corrosion inhibitor are determined,which can avoid hydrate ice plugging,and used in the throttling process at all levels with remarkable effect.