井筒结构对注蒸汽井筒导热的影响

Influences of borehole structure on heat conductivity of steam injection borehole

井筒和地层间的温度交换普遍存在于钻井、完井或油气井增产、注蒸汽开采稠油等作业过程中,由于热交换产生的温度变化对工质流体的性质产生影响,从而影响措施实施效果,准确计算井筒与地层的导热具有重要的意义。不同于以往的井筒导热模型研究单一结构下的井筒热损失,而是从符合实际情况的基本假设出发,建立了考虑有无隔热层、封隔器以及井筒偏心结构等情况下的井筒导热模型。把导热分为井筒到水泥环外壁和地层导热两部分计算,对不同的井筒结构采用不同方法计算总传热系数,数值法求解每个节点处的热损失,并通过模型对比计算了不同井筒结构对井筒热损失的影响程度,得到最经济有效的井筒结构。

Heat interchange among borehole and formations commonly exists in the processes of drilling, well completion, production well stimulation or steam injection, as a consequence of which, the temperature variation would generate impacts on the properties of working fluid and then affect the treatment effect. Accurate computation of heat conductivity between borehole and formations are of great importance. Differing from focusing on borehole heat loss under single structure by conventional borehole heat conductivity model, a new borehole conductivity model has been buih up here as to take into considerations on the existence of thermal insulators, packers and also borehole decentralization structure, which complies with practical situations more appropriately. The heat conductivity calculation has been divided into two parts, form the borehole to the exposure of cement mantle and in the formations, as for corresponding to different borehole structures, different methods have been adopted to sum the overall heat transfer coefficients and numerical method is used to calculate the heat loss on each nodal point, furthermore, through the model proposed herein, the degrees of influences of different borehole structures on heat loss could be calculated in order to get the most economic and efficient borehole structure.