Wellbore Pressure and Temperature Prediction Model and Its Affecting Factors for CO2 Injection Wells
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摘要: 为了提高注CO2驱替效率及驱替成功率,开展了影响驱替效率的井筒压力温度分布及影响因素研究。针对CO2特殊的物理性质,选用基于赫姆霍兹自由能的Span-Wagner状态方程,将井筒传热、压力与CO2物性参数耦合迭代计算,建立了注CO2井筒温度压力分布的数学预测模型。该模型能够预测井筒温度压力及其他物性参数,应用该模型预测井筒各点温度压力,并与江苏草舍油田草8井现场2次实测结果对比,其温度误差均小于1%,压力最大误差不超过1.6%,表明该模型能够满足现场应用要求。利用该模型可以研究注入温度、注入压力、注入速度及注入时间等工艺参数对井底压力温度的影响规律,实现系统敏感性分析。研究表明,建立的模型具有很高的精度,对提高CO2驱替效率具有指导作用,并适用于(超临界)CO2钻井、压裂过程中井筒温度压力预测及影响因素分析。Abstract: In order to improve the displacement efficiency and success rate of CO2 flooding,research has been carried out to predict the pressure and temperature distribution in the wellbore,which affects the displacement efficiency.In view of the special physical properties of CO2,Span-Wagner equation of state,based on the dimensionless Helmholtz energy,has been adopted to establish a model to predict the distribution of temperature and pressure while injecting CO2,calculated by iterative coupling with CO2 physical parameter and pressure as well as heat.The model can predict the bottomhole temperature and pressure accurately.Compared with the well site data of Well Cao 8 in Jiangsu Oilfield,the error of predicted temperature less than 1%,and the maximum error of pressure less than 1.6%,it can meet the requirements of field application.Moreover,the sensitivity analysis can be done through the research of effecting regularity on the bottomhole pressure and temperature produced by injection temperature,injection pressure,injection rate and time,etc.Study shows that model is very accurate,and it can guide CO2 flooding,fit for prediction and analysis of wellbore temperature,pressure and related affecting factors in supercritical CO2 drilling and fracturing.
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Keywords:
- CO2 injection /
- state equation /
- well bore flow /
- pressure /
- temperature
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