Ado Muhammad Rabiu
Department of Chemical Engineering, College of Engineering, King Faisal University, P.O. Box 380, Al-Ahsa, 31982 Kingdom of Saudi Arabia.
J Pet Explor Prod Technol. 2022;12(2):421-435. doi: 10.1007/s13202-021-01345-5. Epub 2021 Oct 30.
The current commercial technologies used to produce heavy oils and bitumen are carbon-, energy-, and wastewater-intensive. These make them to be out of line with the global efforts of decarbonisation. Alternative processes such as the toe-to-heel air injection (THAI) that works as an in situ combustion process that uses horizontal producer well to recover partially upgraded oil from heavy oils and bitumen reservoirs are needed. However, THAI is yet to be technically and economically well proven despite pilot and semi-commercial operations. Some studies concluded using field data that THAI is a low-oil-production-rate process. However, no study has thoroughly investigated the simultaneous effects of start-up methods and wells configuration on both the short and long terms stability, sustainability, and profitability of the process. Using THAI validated model, three models having a horizontal producer well arranged in staggered line drive with the injector wells are simulated using CMG STARS. Model A has two vertical injectors via which steam was used for pre-ignition heating, and models B and C each has a horizontal injector via which electrical heater and steam were respectively used for pre-ignition heating. It is found that during start-up, ultimately, steam injection instead of electrical heating should be used for the pre-ignition heating. Clearly, it is shown that model A has higher oil production rates after the increase in air flux and also has a higher cumulative oil recovery of 2350 cm which is greater than those of models B and C by 9.6% and 4.3% respectively. Thus, it can be concluded that for long-term projects, model A settings and wells configuration should be used. Although it is now discovered that the peak temperature cannot in all settings tell how healthy a combustion front is, it has revealed that model A does indeed have far more stable, safer, and efficient combustion front burning quality and propagation due to the maintenance of very high peak temperatures of mostly greater than 600 °C and very low concentrations of produced oxygen of lower than 0.4 mol% compared to up to 2.75 mol% in model C and 1 mol% in model B. Conclusively, since drilling of, and achieving uniform air distribution in horizontal injector (HI) well in actual field reservoir are costly and impracticable at the moment, and that electrical heating will require unphysically long time before mobilised fluids reach the HP well as heat transfer is mainly by conduction, these findings have shown decisively that the easy-and-cheaper-to-drill two vertical injector wells configured in a staggered line drive pattern with the horizontal producer should be used, and steam is thus to be used for pre-ignition heating.
目前用于生产重油和沥青的商业技术碳密集、能源密集且废水排放量大。这些因素使得它们与全球脱碳努力背道而驰。需要替代工艺，例如从脚跟到脚尖的空气注入法（THAI），它作为一种原位燃烧工艺，利用水平生产井从重油和沥青储层中回收部分提质油。然而，尽管进行了试点和半商业运营，但THAI在技术和经济上尚未得到充分验证。一些研究利用现场数据得出结论，认为THAI是一种低产油率工艺。然而，尚无研究全面调查启动方法和井网配置对该工艺短期和长期稳定性、可持续性及盈利能力的同时影响。使用经过验证的THAI模型，利用CMG STARS软件模拟了三个模型，其中水平生产井与注入井呈交错排状排列。模型A有两个垂直注入井，通过它们注入蒸汽用于点火前加热；模型B和C各有一个水平注入井，分别通过它们使用电加热器和蒸汽用于点火前加热。研究发现，在启动过程中，最终应使用蒸汽注入而非电加热进行点火前加热。显然，结果表明，在空气通量增加后，模型A的产油率更高，其累计产油量为2350立方厘米，分别比模型B和C高9.6%和4.3%。因此，可以得出结论，对于长期项目，应采用模型A的设置和井网配置。尽管现在发现峰值温度在所有情况下都无法说明燃烧前缘的健康状况，但研究表明，由于模型A大多能维持高于600℃的非常高的峰值温度，且产生的氧气浓度非常低，低于0.4摩尔%，而模型C高达2.75摩尔%，模型B为1摩尔%，所以模型A确实具有更稳定、更安全和更高效的燃烧前缘燃烧质量及传播特性。总之，鉴于在实际油藏中，在水平注入井中进行钻井并实现均匀的空气分布目前成本高昂且不切实际，而且由于热传递主要通过传导，电加热需要很长时间才能使流体到达生产井，这些研究结果明确表明，应使用易于钻探且成本较低的两个垂直注入井，它们与水平生产井呈交错排状排列，并使用蒸汽进行点火前加热。
