浅薄层特超稠油油藏冷热交替开采技术研究

针对浅薄层特超稠油油藏蒸汽吞吐开发初期面临的油层厚度薄、原油黏度高、蒸汽热损失大、吞吐有效期短等问题，提出了冷热交替大周期吞吐开发模式，有效改善开发效果。为此开展了浅薄层特超稠油油藏冷热交替开采三维物理模拟研究，结果表明：受顶底盖层热损失影响，蒸汽吞吐温度下降迅速，峰值产量较高，但单周期生产时间较短，约100 min；降黏吞吐可以降低吞吐井附近含油饱和度，提高产油速度，降低含水率，延长吞吐周期50 min 以上；提高温度可以增强降黏剂的降黏效果，第二周期开始冷热交替改善效果优于第一周期，其生产时间延长60 min，含水率降低45%，周期采出程度提高1.7%。利用数值模拟方法优化了冷热交替的注入参数，建立了该技术的政策界限：最佳转冷热交替的时机为2～3 周期，注入强度为0.02 t/m；适用的油层厚度小于8 m，原油黏度小于200 000 mPa?s，含油饱和度大于0.6，渗透率大于1 000 mD。

Research on alternating heat and cold fluid injection technology in shallow-thin ultra-heavy oil reservoirs

Small reservoir thickness， high crude oil viscosity， large steam heat loss， and short cyclic steam stimulation （CSS） period are problems facing in shallow-thin ultra-heavy oil reservoirs at the early stage of CSS development. Therefore， the development model of large CSS of alternating hot and cold fluid injection was proposed to improve the development effect effectively. In addition， carried out a three-dimensional physical simulation experiment of alternating heat and cold fluid injection in shallow-thin ultra-heavy oil reservoirs. The results show that the temperature of CSS decreases rapidly and the peak production is high because of the heat loss of the top and bottom cap rocks， but the single cycle production time is short， about 100 min. The injection of viscosity reducer can reduce the oil saturation near the well， improve the oil production rate， lower the water content， and increase the CSS period by more than 50 min at the production stage. Increasing temperature can enhance the viscosity reduction effect of the viscosity reducer， and the improvement effect during the second cycle is better than that during the first cycle. In addition， the production time is increased by 60 min， water content is cut by 45%， and the oil recovery is enhanced by 1.7%. The injection parameters of heat and cold fluid were optimized and the policy limits of this technology were established by a numerical simulation method：The best timing of alternating heat and cold fluid injection is the second or third cycle； and the injection strength is 0.02 t/m. The suitable reservoir thickness is less than 8 m； the crude oil viscosity is less than 200 000 mPa·s；the oil saturation is higher than 0.6，and the permeability is higher than 1 000 mD.