No abstract

No abstract

No abstract

Summary Cold heavy oil production with sand (CHOPS) is the process of choice for unconsolidated heavy oil reservoirs with relatively high gas content. The key challenge of CHOPS is that the recovery factor tends to be between 5% and 15%, implying that the majority of the oil remains in the ground after the process is rendered uneconomic. Continued cold production (without sands) is not productive for a post‐CHOPS reservoir because of the low oil saturation and depleted reservoir pressure in the wormhole regions. There is a need to develop viable recovery processes for post‐CHOPS reservoirs. Here, different follow‐up processes are examined for a post‐CHOPS heavy oil reservoir. In post‐CHOPS cold water flooding, severe water channeling is ineffective at displacing high viscosity heavy oil. Hot water flooding improves the sweep efficiency and produces more oil compared with cold water flooding. However, the swept region is limited to the domain between the neighboring wormhole networks, and the energy efficiency of the process is relatively poor. Compared with the hot water flooding case, steam flooding achieves higher oil production rates and lower water use. A cyclic steam stimulation strategy achieves the best performance regarding oil production rates and water usage. Based on our results, it is observed that thermally based techniques alone are not capable to recover the oil economically for post‐CHOPS reservoirs. However, it is suggested that techniques with combined use of thermal energy and solvent could potentially yield efficient oil recovery methods for these reservoirs. Copyright © 2015 John Wiley & Sons, Ltd.

Stochastic optimization, based on a simulated annealing method, was done to determine the optimum hot water-flooding strategy for recovery of oil from thin (<6 m) heavy oil reservoirs. The results reveal that high injection pressures are critical to a successful hot water flooding strategy. For water temperature during injection, the results show from a thermal efficienty point of view that that it is most efficient to adopt a temperature profile where the injection temperature starts high and ends at low water temperature. Multiple cycles of this profile might be beneficial depending on the reservoir conditions. The lower temperature injection at later stages of the recovery process partially recovers the heat stored in the reservoir matrix and therefore increases the overall heat utilization efficiency. A sensitivity analysis shows that the permeability distribution affects the performance of the hot water flooding process most significantly. The existence of a higher permeability zone in the lower part of the reservoir leads to earlier oil production and water breakthrough. The absolute permeability value has the largest effect on process performance. High permeability was found to lead to more oil and water production in the early stage of operation and achieved the best economic performance. The low permeability case was found to show a slow oil production. Although it has the lowest cumulative injected energy to oil produced ratio, poor oil production made the operation process uneconomic.