海洋双层管双梯度钻井井筒温度分布规律研究

Distribution Law of Wellbore Temperature in Offshore Dual-layer DEG

井筒温度对天然气水合物的存在状态有显著影响。为了准确掌握海洋双层管双梯度钻井井筒温度分布规律,基于传热学理论,充分考虑岩屑对内管混合流体热物性参数的影响,以及隔水管、套管、裸眼等井段环空内不同流体类型对传热的影响,引入综合导热系数,建立了适用于双层管双梯度钻井的井筒温度场预测模型,并探究了井筒温度分布规律。研究结果发现:对双层管双梯度钻井井筒而言,其在海底附近的温度达到最低值,在水合物固态流化开采时应特别注意该井段的井筒温度分布;注入流体温度、排量和钻井液比热容的增大,会导致内管流体温度剖面整体增大;注入流体温度主要影响井口附近的内管流体温度,而排量和钻井液比热容主要影响海底附近的内管流体温度,可以通过调节上述参数来改善不同井段井筒温度分布,以减少水合物的生成。研究结果可为水合物的安全高效开采提供理论支撑。

Wellbore temperature has a significant influence on the state of natural gas hydrate.In this paper,a wellbore temperature field prediction model for dual-layer dual-gradient drilling (DGD) was built according to the theory of heat transfer by incorporating the comprehensive thermal conductivity and considering the influence of cuttings on the thermal physical parameters of the mixed fluid in the inner pipe and the influence of different fluids in the annulus of riser,casing and open hole on the heat transfer.With this model,the distribution law of wellbore temperature in offshore dual-layer DGD was investigated.It is found that,for the dual-layer DGD wellbore,the temperature near the seabed is the lowest,which should be carefully considered in the process of hydrate solid fluidization production.The increase of injected fluid temperature,displacement and specific heat capacity of drilling fluid lifts the temperature profile of inner pipe fluid.Specifically,the temperature of the injected fluid mainly affects the temperature of the inner pipe fluid near the wellhead,while the displacement and the specific heat capacity of drilling fluid mainly affect the temperature of the inner pipe fluid near the seabed.Therefore,it is possible to improve the wellbore temperature distribution in different well sections by adjusting the above parameters to minimize the formation of hydrate.The research provide theoretical support for the safe and efficient exploitation hydrate.