复合钻井液添加剂抑制天然气水合物形成研究

PRELIMINARY STUDY ON HOW COMPOSITE DRILLING FLUID ADDITIVES INHIBIT GAS HYDRATION

近年来深水钻井过程中天然气水合物抑制剂的研究方向从热力学抑制剂转向动力学抑制剂和防聚剂。然而一旦注入系统发生故障,对于不定期关闭气井或抑制剂不足等原因造成的水合物堵塞,动力学抑制剂是无能为力的;而表面活性剂价格昂贵,单纯使用表面活性剂做防聚剂对于油田成本而言不经济。因此鉴于单一试剂在实际应用中存在诸多限制,将动力学抑制剂、防聚剂、热力学抑制剂以及其他辅助剂联合使用,将不同类型的抑制剂进行复配,会大大改善作用效果。文章研究各类抑制剂的优缺点,本着减少用量,提高过冷度,更适用于工业化应用,对复合抑制剂的配方进行试验。在此基础上,进行水合物抑制钻井液配方试验,得到性能较佳的钻井液配方。水合物抑制钻井液在土侵8%条件下,动速比低于0.6、API滤失低于3 m L,模拟水下压力温度条件,保持无水合物生成1.5 h以上。

In recent years,the research on natural gas hydrate inhibitors for deepwater drilling has transformed from thermodynamics inhibitors to kinetic inhibitors and anti-agglomerant inhibitors. However,once the malfunction occurs in the injection system,kinetic inhibitors will become useless when plugged by gas hydrates due to irregular well shut-in or insufficient inhibitors. Meanwhile surfactants will not be economically viable as a single anti-agglomerant inhibitor. Considering that any single inhibitor has some limitations in the actual application,compounding kinetic inhibitors,anti-agglomerant inhibitors,thermodynamic inhibitors and other auxiliary agents is expected to prevent hydrate plugging. As described in this article,a comprehensive study on the advantages and disadvantages of various inhibitors was made. And on the condition of less dosage,higher supercooling degree,and more suitable for commercial application,the prescription for the composite inhibotors was experiment studied in the lab,and then experiments on hydrate-inhibiting drilling fluids were done to get the best prescription for drilling fluid.When soil invasion being 8%,the developed inhibiting drilling fluid had a ratio of dynamic shear force / yield value to plastic viscosity lower than 0.6,API filtration lower than 3ml,kept in hydration-free state for over 1.5 hours when under simulated subsea pressure and temperature conditions.