水平井注蒸汽非稳态传热与流动分析

水平井注汽采油在稠油开采过程中得到广泛的应用,建立热采注汽过程中水平井井筒-储层耦合的非稳态传热与渗流模型,利用数值方法研究注蒸汽阶段的油、水、汽在井筒和油藏中三相非稳态流动与传热规律,分析井筒内积存原油对蒸汽推进的影响;同时计算分析湿蒸汽参数沿水平井段变化特点。研究结果表明:新建模型揭示了井筒内蒸汽前沿推进机制;在注汽速度8 t/h、注汽干度0.7时,注汽5 d后井筒内积存原油被驱替;受井筒内蒸汽流量变化和井筒与油藏热交换影响,湿蒸汽比焓(或干度)从水平井跟端到趾端下降较快;随着注汽速度和注汽干度的增大水平井吸汽段长度增加。

Process analysis of unsteady heat transfer and fluid flow during steam injection via horizontal wells

Steam injection via horizontal wells has been widely used for heavy oil recovery. In this study, numerical simulation models of heat transfer and fluid flow in wellbore in coupling with reservoir flows during the process of steam injection in a horizontal well were established, in which the unsteady flow and heat transfer of multi-phase(i.e. steam, water and oil) in reservoir and wellbore were considered. The influence of oil accumulation in wellbore on the migration and diffusion process of steam and water was analyzed, and the variations of the flow and thermal parameters of wet steam along the horizontal well were calculated. The simulation results of a case study indicate that the proposed horizontal well steam injection model can effectively simulate the moving steam front in the wellbore, and the accumulated oil stockpile can be flooded out from the wellbore after 5 days of steam injection with injection rate of 8 t/h and steam dryness of 70%. During the injection process, the enthalpy of the injected wet steam decreases rapidly from the heel to the toe of the horizontal well. Increasing steam injection rate and its dryness can increase the heat transfer to the oil formation along the horizontal well.