A criterion for evaluating the efficiency of water injection in oil sand reservoirs
A criterion for evaluating the efficiency of water injection in oil sand reservoirs
复制标题
油砂油藏注水效率评价标准
DOI：
10.1016/j.petrol.2016.10.056
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发表时间：
2017-01-01
影响因子：
--
通讯作者：
Chen, Shengli
中科院分区：
文献类型：
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作者：
Lin, Botao;Jin, Yan;Chen, Shengli
蒸汽辅助重力排采（SAGD）技术在新疆克拉玛依市超稠油油藏开发中得到了大规模的应用。在循环蒸汽之前，以前SAGD项目的副产品水被注入SAGD井对，以便在井间区域形成一个膨胀的高渗透率区域。需要一个标准来评估注入/增产的效率。该标准基于双井周围区域的孔隙压力分布，这是使用Drucker-Prager模型描述油砂的有限元分析结果。分析使用实验室结果校准的本构参数和实时注射数据输入作为加载条件。在模拟压力剖面的基础上，提出了代表注水效率的通信参数（CP），其数量级为0 ~ 1。发现CP随注射过程逐渐持续增加，表明效率随时间和压力的增加而增加。此外，通过监测现场注入速率急剧增加的时间点，根据之前完成的各种油砂储层增产项目，建立了一组阈值CPs。然后通过将计算CP与特定油藏类型的阈值CP进行比较，满足该标准。将该准则应用于现场两口井对的增产工程中，发现当CP超过相应储层类型的阈值后，两口井的压力迅速相互响应，注入速度急剧增加。这两口井的预热周期从常规的180-300天缩短到60天和90天，意味着储层增产成功。所提出的标准不仅可以定量描述注水过程的效率，还可以确定油砂油藏的增产是否成功完成。当满足标准时，现场工程师可以放心地进入蒸汽循环阶段。
Steam Assisted Gravity Drainage (SAGD) has been implemented at a large scale in the development of ultra heavy oil reservoirs in Karamay city, the Xinjiang province of China. Before circulating steam, byproduct water from previous SAGD projects is injected into a SAGD wellpair in order to create a dilative and highly permeable zone in the inter-well domain. A criterion is desired to evaluate how efficient this injection/stimulation has been performed. The criterion was based on pore pressure distribution in the domain encompassing the dual wells, which was the outcome from finite element analysis using the Drucker-Prager model to describe oil sand. The analysis used constitutive parameters calibrated by laboratory results and the real-time injection data input as loading conditions. Based on the simulated pressure profile, communication parameter (CP) was proposed to represent the efficiency of water injection, with a magnitude varying from 0 to 1. It was found that CP gradually and continuously increased with the injection process, demonstrating that the efficiency increases with time and pressure. Moreover, by monitoring the time point at which the injection rate dramatically increased in the field, a group of threshold CPs were established based on the previously completed stimulation projects on a variety of oil sand reservoirs. The criterion was then fulfilled by comparing the calculated CP to the threshold CP of a specific reservoir type. By applying the criterion in the stimulation projects of two wellpairs in the field, it was observed that immediately after the CP exceeds the threshold value of the corresponding reservoir type, the pressure of the dual wells was quickly responsive to each other and the injection rates sharply increased. The preheating periods of the two wellpairs decreased from conventionally 180-300 days to 60 and 90 days, implying the success of reservoir stimulation. The proposed criterion can not only be used to quantitatively describe how efficient a water injection process has achieved, but also to determine whether the stimulation of an oil sand reservoir has been successfully accomplished. When the criterion is satisfied, the field engineers can confidently move on to the steam circulation stage.