Wang Fei, Yang Zhengda, Wang Xinwei, Lin Riyi
College of New Energy, China University of Petroleum, Qingdao, Shandong 266580, China.
ACS Omega. 2020 Nov 19;5(47):30478-30487. doi: 10.1021/acsomega.0c04264. eCollection 2020 Dec 1.
In the steam-assisted-gravity-drainage (SAGD) process, heat energy is transferred from the steam chamber to the farther cold reservoir by conduction and convection mechanisms, so as to reduce the oil viscosity. In previous research works, although it was proved that convection is an indispensable part of the heat-transfer process, there is still a controversy about the formation mechanism of heat convection. In this study, an analytical mathematic model was proposed to explore the convective heat transfer in SAGD operation. Typically, this model integrates three heat convection forms that are generated by pressure difference, gravity, and thermal expansion of connate water,. Subsequently, the simulation results are compared with field data to evaluate the accuracy of the new model, and they are reasonably consistent with UTF field data. The results indicate that convective heat transfer plays a predominant role in the immediate vicinity of the steam chamber interface. Furthermore, this paper derives a mathematic model of oil production to explore the effect of heat convection on oil production under different operation conditions. The results demonstrate that heat convection has an adverse impact on oil production, but it is inevitable. This study also displays that some parameters, such as the lateral spreading rate, the thermal diffusivity, the viscosity coefficient, and the curvature of oil relative permeability curve, can significantly affect the oil production rate. Based on this study, the effect of convection mechanism on the heat-transfer process and oil production will be further clarified, and the parameters in the SAGD process can be optimized, so as to effectively enhance and predict oil production.
在蒸汽辅助重力泄油（SAGD）过程中，热能通过传导和对流机制从蒸汽腔传递到较远的冷储层，从而降低原油粘度。在以往的研究工作中，虽然已证明对流是传热过程中不可或缺的一部分，但关于热对流的形成机制仍存在争议。在本研究中，提出了一个解析数学模型来探究SAGD作业中的对流换热。通常，该模型整合了由压力差、重力和原生水热膨胀产生的三种热对流形式。随后，将模拟结果与现场数据进行比较以评估新模型的准确性，结果与UTF油田数据合理一致。结果表明，对流换热在蒸汽腔界面附近起主要作用。此外，本文推导了一个产油数学模型，以探究不同作业条件下热对流对产油的影响。结果表明，热对流对产油有不利影响，但不可避免。本研究还表明，一些参数，如横向扩展速率、热扩散率、粘度系数和油相对渗透率曲线的曲率，会显著影响产油率。基于本研究，将进一步阐明对流机制对传热过程和产油的影响，并优化SAGD过程中的参数，从而有效提高和预测产油量。
