考虑蒸汽超覆的稠油蒸汽吞吐产能预测模型

常规稠油油藏蒸汽吞吐产能预测模型假设注入蒸汽活塞式驱替原油，油层顶底加热面积相同，实际生产过程中，由于原油和蒸汽密度不同产生重力分异作用，出现蒸汽超覆现象，导致油层顶部加热面积大于底部加热面积。通过确定顶底盖层加热半径之间的关系，引入等效半径，在拟稳态产量公式基础上，建立了考虑蒸汽超覆的蒸汽吞吐产能预测模型。以孤岛油田M区块为例，分别采用本文模型、Marx模型和商业模拟器CMG计算产能。模拟结果表明，Marx模型由于未考虑蒸汽超覆现象造成热损失较小，预测产能偏高，平均相对误差为41%，而本文模型计算结果平均相对误差为12%，最小相对误差为7%，与商业软件计算结果较吻合。研究结果表明，考虑蒸汽超覆的稠油蒸汽吞吐产能预测模型具有一定可靠性，可用于稠油油藏蒸汽吞吐产能预测。 

A Productivity Prediction Model for Heavy Oil Steam Huff and Puff Considering Steam Override

In the conventional productivity prediction model, steam huff and puff in heavy oil reservoirs is assumed to have a piston-type displacement,and considers the heating area to be the same from the top to the bottom of the reservoir.However,in an actual field application,the steam heat can transmit upward due to different oil and gas densities resulting in gravity differentiation,leading to a larger heating area at the top of the reservoir than that at the bottom(this phenomenon is called steam override).By determining the relationship between the heating radii of the top and bottom cap rocks,and introducing equivalent radius,a prediction model of steam huff and puff productivity in consideration of steam override was established on the basis of quasi-steady-state yield formula.Taking the M block in Gudao Oilfield as an example, the new model in this paper,the Marx model and a commercial simulator were used to calculate productivity.Simulation results indicated that the Marx model obtained a relatively high productivity because of without considering the steam override,with less heat loss and an average error up to 41%.However,our new model has an average relative error of 12% and a minimum relative error of 7%,which is consistent with the calculation results of the commercial software.The research results showed that the new productivity prediction model for steam huff and puff that takes into consideration steam override is reliable and could be put into practice.