气井非稳态流井筒温度压力模型的建立和应用

Construction and application of a wellbore temperature and pressure model for unsteady flow in gas wells

国内外围绕井筒温度方面的研究主要集中在稳态流条件下,建立了较成熟的气井稳态流井筒温度、压力计算模型。但气井在生产过程中,由于生产组织和试井测试的需要,对其产量将进行调整,此时井筒管流属于非稳态流,已有的基于稳态流的井筒温度模型不适用于非稳态流的井筒温度计算。为此,通过分析井筒非稳态传热温度变化特征,根据井筒瞬态温度与稳态温度的关系,将任意时间点的井筒温度变化划分为递减、稳定和递增3种类型。采用微元时间段计算井筒温度和压力的思路,对定产量开井井筒温度模型进行改进,提出温度叠加递增井筒温度压力计算方法,并根据杜哈梅的等效叠加原理,提出温度叠加递减井筒温度压力计算方法,建立了气井非稳态流井筒温度压力模型,解决了变流量条件下气井井筒温度、压力的计算问题。通过实例分析对比表明,在气井开井和产量调整初期,气井非稳态流井筒温度压力模型比稳态流井筒温度压力模型计算更加准确,该模型适用于气井生产全过程,应用范围更广,符合生产实际。

The global studies on wellbore temperatures are mainly focused on the steady flow condition, and the relatively mature well- bore temperature and pressure models for steady flow in gas wells have been built. However, in the production process of gas wells, the production will be adjusted for the purpose of production organization and well testing, and then the wellbore tubing flow is unsteady flow. The available wellbore temperature models based on steady flow are not suitable for calculating wellbore temperatures for unsteady flow. In this paper, based on the analysis of changes in unsteady heat transfer temperatures in wellbore, and according to the relationship between wellbore transient temperature and steady temperature, the wellbore temperature changes at any time were divided into three types： decline, stability and increment. According to the idea of calculating wellbore temperatures and pressures by the infinitesimal time period, the wellbore temperature model for wells producing at a constant rate was modified, and the wellbore temperature and pressure calculation method based on the superimposed increment of temperatures was proposed. Moreover, according to the Duhamel＇s equivalent superimposition principle, the wellbore temperature and pressure calculation method based on the superimposed decrement of tempera- tures was presented. Then, the wellbore temperature and pressure model for unsteady flow in gas wells was built for calculating wellbore temperatures and pressures in gas wells under the condition of variable flow rates. The analysis and comparison of some examples show that, at the initial stage of gas well producing and production adjustment, the wellbore temperature and pressure model for unsteady flow in gas wells provides a higher accuracy than the model for steady flow. The proposed model is suitable for the whole production process of gas wells, so it can be more widely used.