气体组分变化对油井水合物生成温度的影响

Effects of Gas Composition Change on Formation Temperature of Oil Well Hydrate

近年来对于气井井筒水合物生成研究甚多,而对油井水合物的生成研究则较少,且由于在重力作用下油相将气、水两相隔开给水合物生成条件测试造成了困难。为此,将测定油气水三相水合物生成问题转化为原油脱出气与水生成水合物的问题,首先开展了油气水三相水合物生成条件测试实验,并以此为基础评价优选出了适用的水合物生成条件预测模型;然后结合油藏流体相图和井筒压力温度预测方法及采出井井流物天然气组成的动态相态数值模拟预测,讨论了天然气组成含量随井深的变化规律;最后采用井口、井深1000 m和井深1900 m处组分数据预测了井筒水合物生成温度剖面,验证了气体组分变化对井筒水合物生成温度的影响。实验及计算结果表明:不同含水率对水合物的生成条件并无影响,各模型中简化牛顿热力学模型误差为7.31%,预测精度相对较高;随井深增加,轻烃逐渐下降,重组分逐渐增大;最后指出,采用组分数据预测油井水合物生成温度剖面时,其数据选择尤为重要,否则可能导致预测的准确性降低。该研究成果对于准确预测油井水合物的生成条件具有重要的意义。

In recent years,there are many researches focusing on wellbore hydrate formation in gas wells,but there are few researches focusing on the formation of oil well hydrate.It is difficult to test the formation condition of hydrate because oil phase separates gas and water under the action of gravity.Therefore,the problem of determining three-phase hydrate formation in oil and gas was transformed into crude oil degassing and water hydrate formation.First,the formation conditions of oil-gas-water three phase hydrate was tested.Subsequently,the suitable prediction model of hydrate formation condition was selected.Then,combined with the reservoir fluid phase diagram and wellbore pressure temperature prediction method and the dynamic phase simulation prediction of the gas composition of the well flow in the production well,the variation regularity of natural gas composition content with well depth was discussed.At last,the formation temperature profile of wellbore hydrate was predicted by using the wellhead,well depth 1000 m and the depth 1900 m of the well,which verified the influence of gas composition change on the formation temperature of wellbore hydrate.Experimental and computational results show these as follows.The different water content has no effect on the formation condition of hydrate.The error of simplified Newton thermodynamic model in each model is 7.31%and the prediction precision is relatively high.With the increase of well depth,the light hydrocarbon decreases gradually and the recombination division increases gradually.Finally,when the formation temperature profile of oil well hydrate is predicted by group fraction,the data selection is especially important because it may otherwise lead to lower accuracy of prediction.The research results are of great significance for predicting the formation conditions of oil well hydrate accurately.