【作者】 刘晓兰；

【导师】 孙宝江；

【作者基本信息】 中国石油大学 ， 油气井工程， 2008， 博士

【摘要】 在深水油气钻探过程中,节流压井管线、隔水管、防喷器及海底井口等部位在钻遇天然气层后均易聚集天然气水合物,给深水油气钻探开发安全带来不利影响。因此,研究深水钻井井筒环空水合物的生成机理,探讨合理的防治措施,对深水油气钻探开发具有重要且深远的意义。基于质量、动量、能量守恒原理及传热学理论,建立了钻井过程中井筒环空压力和温度分布的计算模型并进行了求解。计算结果表明,循环钻进期间,为了防止隔水管内温度太低而形成水合物,应保证隔水管的保温层完好,并尽量增大循环排量;停止循环时,随着关井时间的增加,井筒内流体温度逐渐接近外界环境温度,使得有可能形成水合物。以相平衡理论为基础,应用统计热力学建立了天然气水合物的分子热力学模型,在此基础上,通过修正逸度系数得到了电解质体系的天然气水合物预测模型;通过UNIQUAC模型确定非电解质抑制剂富水相中水的活度系数,获得了醇类体系的天然气水合物预测模型。设计了水合物形成及分解的室内实验方案,并进行了纯水合物体系、无机盐类添加剂、醇类添加剂、有机聚合物类泥浆添加剂和商用聚合醇抑制水合物实验,得到不同添加剂在不同质量百分数情况下的水合物生成及分解曲线,对实验结果拟合回归获得多种添加剂的水合物预测相态曲线;通过过冷度对比的方法,对各类添加剂的抑制水合物形成能力大小进行判断,并最终给出合理钻井液配方。在实验数据的基础上,引入新的模型参数——相对活性K_A,提出了新的水合物预测方法,并结合无机盐实验结果验证了新方法的可行性。在理论和实验研究的基础上,开发了天然气水合物生成预测软件,针对加入的不同抑制剂、不同抑制剂浓度、不同天然气组分等情况,软件均能提供水合物生成温度、压力区域的预测结果。结合本文研究成果,根据天然气水合物的产生机理,从升温、降压和添加剂三个方面分析了防治天然气水合物的有效措施;并针对某些特殊的气井作业,介绍了蒸汽换热器和逐级节流防止水合物的方法。更多还原

【Abstract】 When natural gas reservoir is broached, gas hydrate is easy to assemble on throttle fill up line, marine riser, blowout preventer and well head in sea floor etc., which bring great affection to petroleum exploration drilling in deep water. For this reason, study on the generation mechanism of hydrate in annular of deep water drilling pit shaft, and advisable prevention bring important and profound sense to deepwater exploration drilling in future.Basing on the principle of conservation of mass, principle of conservation of momentum, principle of conservation of energy and the theory of thermal conduction study, the paper establishes computational model of annular pressure and temperature distribution in wellbore of drilling process, and solves it. The computational solution indicates that, it should take precautions against the temperature in marine riser too low which can formate gas hydrate, so the insulating layer of marine riser should be well and the circulation delivery volume should be broadened to the full during the circulating drilling term. When stopping circulation, with the increase of close time, the fluid temperature in wellbore will be close to the outside environment temperature inch by inch, and this make the gas hydrate formation possible.Basing on phase equilibrium theory, applying statistics thermodynamics, the paper builds molecular thermodynamics pure model of gas hydrate. By amending the formula of fugacity coefficient, the paper achieves the gas hydrate forecasting model of electrolyte system. Using UNIQUAC model to get activity of water in wealthy aqueous of non-electrolyte inhibitor, then the paper obtains gas hydrate forecasting model of alcohol system.The paper designs experiment scheme of hydrate formation and dissociation in-house, successively proceeds hydrate experiment of pure hydrate system, inorganic salt additive, alcohol additive, organic polymer mud additive and commercial polyalcohol, then obtains hydrate generation and dissociation curve of different additive with different quality percent. The paper gets hydrate prediction phase curves of different additives after the fit and regression to the laboratory findings. By the method of comparing super-cooling degree, the paper judges the effect of inhibitting hydrate generation of different additive, and then provide a drilling fluid composition. On the base of laboratory datum, the paper inducts relative activity K_A, a new model parameter, and proposes a new hydrate prediction means, which is verified feasible by the inorganic salt laboratory findings.The paper draws up forecasting software of gas hydrate formation on the bases of theory and experiment studies. In view of adding inhibitor of different concentration with different concentration and different natural gas component, the software can provide the forecasting calculation of hydrate formation temperature and pressure.Combining with the research mentioned above, according to the formation mechanism of gas hydrate, the paper introduces effectively well control measure of inhibitting gas hydrate through temperature ascension, pressure release and additive. Moreover, in view of some special gas well operation, the paper also introduces the measure of steam exch and throttling step by step to inhibit hydrate.更多还原