天然气水合物浆流变性的研究现状及发展趋势

Research progress in and developing trend of the rheological property of natural gas hydrate slurry

天然气水合物浆技术作为一种新兴的水合物防治手段和油气混输方式因其具有巨大的优势而引起了人们的普遍关注,浆液的流变性研究是水合物浆技术实现工业应用的关键,然而,目前相关的文献报道较少。为此,对国内外水合物浆流变性研究进行了系统的介绍,总结了水合物浆的宏观与微观流变性研究方法、测试手段及相关结论,归纳了水合物的体积分数、流速、含水量、水合物颗粒粒径等因素对水合物浆流变性的影响规律,从水合物颗粒聚集力及其影响因素、聚集动力学模型两方面解释了水合物颗粒微观聚集机理,在此基础上提出了强化水合物浆稳定性的4条措施:①提高水转化率,获得"干水合物"颗粒;②将水合物颗粒表面变为油湿性,以降低液桥形成几率;③控制热力学条件实现冷流技术;④寻找临界流速。同时,分析了目前水合物浆流变性实验及理论研究中存在的3个问题:①水合物浆流变性各影响因素之间可能存在交互作用,实验方案不免有疏漏之处,其结论难以具有代表性;②研究缺乏理论基础,说服力较差;③目前的实验研究结论不能直接应用于现场生产,实验研究有待改进且难度较大。最后,指出了未来水合物浆流变性研究的5个方向:①构建微观聚集动力学模型,研究水合物颗粒的聚集机理;②将水合物浆的宏观流变性与微观流变性研究相结合;③寻找水合物浆液稳定流动的临界条件及代表参数,建立稳定流动的评价指标;④加强防聚剂的研究,扩大其使用范围,提高防聚效果,降低药剂成本;⑤研究水合物浆流变性的机理,继续寻找其他可提高水合物浆液稳定性的措施。

Natural gas hydrate slurry is a new means for hydrate prevention and oil-gas mix-transportation and has aroused great concern due to its advantages.The research on the rheological property of the slurry is the key to its industrial application,but such related literature or reports can not be easily found.In view of this,this paper introduces the studies on the rheological property of hydrate slurry at home and abroad,summarizes both microscopic and macroscopic research methods,test means,and the corresponding results,presents the laws of how factors such as volume fraction,flow rate,water content,particle size distribution of hydrate affect the rheological property of slurry,and particularly explains the mechanism of mciro-agglomeration of hydrate particles from the aspects of agglomeration force and its controlling factors,and the agglomeration kinetics model.On basis of this,this paper presents the following measures for strengthening the stability of hydrate slurry:(1) increasing water transform efficiency to obtain the particles of dry hydrate;(2) turning the particle surface into the oil wettability to prevent the formation of liquid bridge;(3) keeping the thermodynamic conditions under control to realize the cold flow;(4) searching for the critical flow rate.Meanwhile,it also analyzes the problems in the present experimental and theoretical studies on the rheological property of hydrate slurry.(1) Because of the interaction between those controlling factors,omissions can be difficult to avoid in such experimental projects,the results of which can not be representative;(2) The results are weak for lack of theoretical basis;(3) The results of the present experimental studies can not be directly used for field practices,and need to be improved and have to face a great challenge.In the end,we point out the developing trend of such studies.(1) A micro-aggregation kinetics model should be built to study the aggtion mechanism of hydrate particles;(2) Macroscopic and microscopic rheological properties should be combined with each other;(3) The critical conditions and the representative parameters should be regarded as evaluating indexes for the steady flow of hydrate slurry;(4) The research on the anti-agglomerant should be encouraged and its application range should be widened to improve the effect of anti-agglomeration and reduce the cost of anti-agglomerant;(5) The mechanism of rheological property of hydrate slurry should be studied to search for other methods of improving the stability of hydrate slurry.