深水气井环雾流水合物沉积和堵塞动力学模型

深水气田开发过程中,海底附近井筒内具有水合物形成和堵塞的风险。基于井筒气液两相环雾流流动模式,根据气芯和液膜内水合物颗粒不同动力学特征,在液膜内考虑水合物颗粒的形成、运移和管壁黏附过程,同时在气芯内考虑水合物颗粒的形成、聚并、破碎和沉降行为,建立了井筒水合物动态沉积和堵塞的动力学模型,可以用于模拟和预测不同工况下井筒内水合物堵塞时间和堵塞位置。模型预测结果与水合物环路实验堵塞压降的相对误差小于10%。针对典型深水气田开发井案例,进行了井筒水合物形成和堵塞风险分析,得到了不同工况下井筒水合物层增长速率、沉积厚度分布和完全堵塞时间的变化规律。

Kinetics Modeling of Gas Hydrate Deposition and Blockage at Annular-mist Flow State in Production Wells of Deep Water Gas Fields

During the production process of deep-water gas fields, gas hydrate can be formed in the wellbore near the wellhead at seabed, which can cause blockage of the production tubing. In this study, a gas-liquid two-phase annular-mist flow pattern is considered in the wellbore, and formation of hydrate particles in the gas core and the liquid films is assumed. A kinetics model for hydrate deposition and wellbore blockage is established, in which the formation, migration and wall adhesion of hydrate particles in the liquid film are considered, and the formation, coalescence, crushing and settling behaviors of hydrate particles are considered in the gas core. The model can be used to simulate and predict the hydrate blockage time and position in the wellbore under different operating conditions. The relative error between the model prediction results and the hydrate loop experiment blockage pressure drop is less than 10%. For a case study of a typical deep-water gas field, the risk analysis of wellbore hydrate formation and blockage is carried out, in which the growth rate of hydrate deposition layer in wellbore, its thickness distribution and complete blockage time are predicted.