天然气水合物预测综合模型及其应用

【作者】 胡顺渠；

【导师】 李颖川；

【作者基本信息】 西南石油学院 ， 油气储运工程， 2003， 硕士

【摘要】 在天然气开采及储运过程中，水合物会导致阀门堵塞、气井停产、管道停输等严重事故。为了有效地防止天然气水合物在设备和管道中生成，本文建立了水合物预测综合模型。此模型考虑了天然气管流及气嘴节流的压力和温度等水合物生成的环境因素、抑制剂及其浓度对水合物生成条件的影响，为防止天然气水合物形成的工艺设计提供了可靠的技术依据。 基于能量守恒原理和范德华混合规则，导出了天然气节流温降机理模型，该模型采用Peng-Robinson方程描述天然气节流的相平衡过程。应用Brown焓熵图版数据对所建立的节流温降机理模型验证表明，在较宽的应用范围内，机理模型的预测与查焓熵图值十分吻合。 应用杜亚和、郭天明所建立的天然气水合物生成条件预测模型及其改进的PR状态方程，考虑了醇类抑制剂加入对体系相平衡的影响，推导了水活度系数的计算方程，使其适用于含醇类抑制剂体系水合物生成条件的预测。综合左有祥、郭天民提出的新水合物热力学模型及左有祥等改进的PT状态方程，对含电解质体系的水合物生成条件进行了预测。天然气水合物预测综合模型具有适用范围广、实用方便等优点。 应用Visual Basic语言自行研制了天然气管流和嘴流的压力、温度计算及天然气水合物生成条件预测的程序，为防止天然气水合物生成提供了工艺技术设计手段。并针对加热、降压、脱水、注抑制剂等防止水合物形成的措施，重点进行了天然气最大容许含水量及抑制剂加入量的计算。 本文根据现场数据，按上述模型，应用自行编制的计算程序，计算了井口至水套炉间天然气的压力、温度及天然气的最大容许含水量，对天然气水合物的生成条件进行了预测，分析了影响水合物生成条件的因素，如天然气相对密度及丙烷含量等，并对加入热力学抑制剂进行了详细计算与分析。更多还原

【Abstract】 Gas hydrate formation during exploitation and transportation is a well recognized operational hazard. It can impose serious accidents such as the choke’s plugging, the gas well’s off production. In order to avoid gas hydrate plugging the equipment, general gas hydrate forecast model is needed. Accounting for the environmental fact of gas hydrate formation such as temperature and pressure of gas flow through pipeline and choke, inhibitor and inhibitor’s concentration, general gas hydrate forecast model is established, which supplies a more reliable technical support for the technical design of gas hydrate prevention. Based on energy conservation theory and van der Waals’s mixed rule, a mathematical model considering phase equilibrium with Peng-Robinson equation is deduced to describe gas flow through choke and temperature drop through choke. A series of data points are acquired from the Brown enthalpy-entropy diagram to calculate by this model. At relative wide range, the results acquired from the model match well with the values from the Brown enthalpy-entropy diagram.Applying the gas hydrate forecast model of Du and Guo, combining their improved Peng-Robinson equation, calculation equation of water’s activity coefficient is educed based on the consider of the infection to the system’s equilibrium from alcohols and mathematical model is extended to the system containing alcohols. Combining the new gas hydrate thermodynamics model put forward by Zuo and Guo with improved Patel-Teja phase equation from Zuo, the mathematical model is expanded to the system containing salts. The general gas hydrate forecast thermodynamics model has merits such as wide adaptability and good convenience.The software of predicting the temperature and pressure of gas flow through pipeline and choke, the gas hydrate forecast is programmed in Visual Basic language, which supplies technical design means for preventing the gas hydrate formation. Also, for methods preventing gas hydrate from formation such as heating, reducing pressure, dehydration and injecting inhibitor, the gas’s maximalallowed water content and the minimum amount of inhibitor injection for avoiding hydrate formation are computed especially.The case calculation is done with field data. The paper makes the predictions which include temperature, pressure, the maximal allowed water content, gas hydrate formation condition of the gas between gas wellhead and jacket heater, and analyzes such influence facts as gas relative density, propane content and water content on the formation of gas hydrate, also makes carefully calculation and analysis to the system containing thermodynamics inhibitor.更多还原