含蜡晶天然气水合物浆液黏度的影响因素

天然气水合物浆液黏度特性是判别水合物浆液输送流动性的重要指标。在深海油气田开发中,特别是对于高含蜡体系,蜡晶与天然气水合物共存的情况时有发生。为此,利用高压天然气水合物流变测量系统,探究了含蜡量、搅拌转速和压力等因素对含蜡晶存天然气水合物浆液黏度的影响规律。实验结果表明:(1)含蜡晶天然气水合物浆液呈现剪切稀释性;(2)含蜡量越大,天然气水合物浆液黏度越高,原因在于悬浮在连续相的蜡晶与吸附在天然气水合物颗粒表面的蜡晶,均对天然气水合物聚并体的增大起到了促进作用;(3)在相同含蜡量的情况下,随着搅拌速率的增加,因体系所受剪切作用强度增加,导致天然气水合物浆液黏度下降;(4)当体系初始反应压力提高时,天然气水合物生成驱动力增强,生成量增加,会显著增加天然气水合物浆液黏度。结论认为,研究蜡晶在高压搅拌天然气水合物浆液体系内的微观分布规律,将是未来探讨蜡晶对天然气水合物浆液黏度特性影响的重要方向。

Factors influencing the viscosity of natural gas hydrate slurry with wax crystal

The viscosity of natural gas hydrate slurry, is an important indicator for discriminating the fluidity of slurry during transportation.When deep-water oil and gas fields are developed, the coexistence of hydrate and wax occurs frequently, especially in the systems with a high wax content. In view of this problem, the influences of wax content, stirring speed and pressure on the viscosity of natural gas hydrate slurry with wax crystal were investigated by using a high-pressure hydrate rheology measurement system. It is found that natural gas hydrate slurry with wax crystal is characterized by shear-thinning; that the viscosity of natural gas hydrate slurry increases with the increase of wax content, since the enlargement of hydrate aggregate is promoted greatly by the wax crystal suspended in the continuous phase and adsorbed to the hydrate particles; that when the wax content is fixed, the shearing strength on the system increases with the increaseof stirring speed, and correspondingly the viscosity of natural gas hydrate slurry decreases; and that if the initial response pressure of the system is increased, the force driving the formation of hydrates is strengthened, more hydrates are generated, and consequently the viscosity of natural gas hydrate slurry is increased significantly. It is concluded that the microscopic distribution of wax crystal in the high-pressure stirring hydrate slurry system would be a critical subject of study to identify the effect of wax crystal on the viscosity of hydrate slurry in the future.