Enhanced Oil Recovery of Heavy Oil in Reservoirs With Bottom Aquifer

Abstract

Oil production in presence of a bottom aquifer is one of the most challenging issues in reservoir engineering. In most cases water coning happens very quickly and the influx of water restricts oil production and limits recovery. The problem is even more difficult when the oil is heavy because the viscosity contrast is large. In some cases horizontal wells may be used to improve the situation but when reservoirs are thin and the oil is viscous even horizontal wells are of limited use. This paper presents the challenges and potential solutions for Enhanced Oil Recovery in heavy oil reservoirs with bottom aquifer. Existing literature is reviewed for field cases of EOR experience with bottom aquifer for chemical as well as thermal processes (SAGD, steam injection as well as In Situ Combustion). In the case of chemical EOR the chemicals may be lost to the aquifer; for thermal recovery the bottom water can act as a heat sink and affect and steam oil ratio. Some in-situ combustion projects have been successful in such settings but in every case the outcome is the same: the economics of the project can be affected. The paper contains some previously unpublished data of polymer injection in a heavy oil pool with some limited bottom aquifer; for the most part it is a review of the existing literature which may prove useful to practicing engineers who are faced with the issue of developing heavy oil resources in the presence of bottom aquifer.

Chemical-Enhanced Oil Recovery by Alkali/Sulfate Smart Water Flooding in Carbonate Reservoirs Using a Green Polymer Extracted from Plantago ovata Seed

“…Reservoirs with an active aquifer are usually sandstone and are not targeted for chemical water injection due to high production and technical issues. For example, a key risk in implementing chemical EOR in reservoirs with an active aquifer is the loss of injected chemicals in the aquifer, which can limit the economic success of the project. , It should be mentioned that gels and polymers with high viscosity are injected in such reservoirs not to increase the efficiency of oil sweeping but to prevent the negative effects of aquifer influx on oil production, which is different from the application investigated in this study.…”

“…For example, a key risk in implementing chemical EOR in reservoirs with an active aquifer is the loss of injected chemicals in the aquifer, which can limit the economic success of the project. 47,48 It should be mentioned that gels and polymers with high viscosity are injected in such reservoirs not to increase the efficiency of oil sweeping but to prevent the negative effects of aquifer influx on oil production, which is different from the application investigated in this study. High salinity is not a characteristic of all reservoirs, and reservoirs with very high salinity are in the category of reservoirs with difficult conditions.…”

Feasibility Investigation on the N2 Injection Process to Control Water Coning in Edge Water Heavy Oil Reservoirs

“…Among the so many heavy oil reservoirs, the heavy oil reservoir with an edge water zone is a typical heavy oil reservoir (Liu, 2013;Liu et al, 2013;Delamaide and Moreno, 2015). Because of the effect of aquifer energy, once the conventional steam injection process, CSS, is performed, a serious problem of water coning can be observed, especially in the initial stage of recovery process.…”

The Supercritical Multithermal Fluid Flooding Investigation: Experiments and Numerical Simulation for Deep Offshore Heavy Oil Reservoirs

“…The steam injection is the most successful and worldwide thermal method and has been applied in many offshore oil fields, such as Bohai field in China and Bressay field and Bentley field in the UK [5,6]. However, for deep offshore heavy oil reservoirs, injected steam has low quality, leading to an inefficient heavy oil production [6].…”