基于蒸汽超覆的稠油蒸汽驱地层热效率计算模型

A calculation model for thermal efficiency based on steam overlap in heavy oil steam flooding

目前地层热效率评价方法主要基于活塞式驱替模型,忽略了蒸汽超覆的影响。通过对蒸汽受力及渗流速度分析,针对反九点注采井网,获得不同蒸汽前缘注采井间的蒸汽超覆程度。基于蒸汽超覆程度的分析,运用热平衡原理及瞬时热平衡理论推导出储层热效率评价模型,并利用拉普拉斯变换及Stehfest数值反演方法进行求解。研究表明:注汽早期阶段,蒸汽超覆程度较弱,蒸汽超覆对热效率影响很小;蒸汽驱中后期阶段,随着蒸汽腔的扩展,蒸汽超覆程度增加,蒸汽沿油层顶部驱替作用明显,蒸汽超覆对油藏热效率影响严重。

T he existing evaluation method of stratum thermal efficiency is on the basis of piston steam displacement model and ignores the influence of steam overlap .By studying the stress and seepage velocity of the steam in inverted nine-spot well pattern ,the overlapping degree evaluation method is obtained , considering different steam frontiers between the producer and the injector .The evaluation model for reservoir thermal efficiency is received on account of the study of steam overlapping degree ,heat balance theory and the instantaneous heat balance expression ,and solved by Laplace transformations and Stehfest numerical inverse method .T he results show that in the early stages of steam injection ,the steam overlap degree is small and the steam chamber expands evenly on longitudinal ,so steam overlap has little influence on the thermal efficiency ;in the middle and later stages of steam injection ,with the expansion of the steam chamber and the increase of steam overlap degree ,the steam displaces along the top ,so steam overlap has severely impact on the thermal efficiency of the reservoir .