Methods of Enhancing Fluid Communication in Oil Sands

Abstract

Abstract Effective steamflooding of oil sands requires fluid communication between injectors and producers. Such a communication path can be developed through a naturally occurring zone of low bitumen saturation. If a water sand with little or no bitumen saturation is encountered, high injectivity can be achieved and a steamflood can be carried out immediately. With zones having mobile water and some bitumen as well, special enhancement processes are required to prevent tar bank ing when steam is injected which is common in steam drive processes where cold bitumen is displaced ahead of a steam front. One way to prevent tar banking is to heat the mobility zones slowly with hot water so that hot bitumen will be displaced when steam drive is initiated. Depending upon the nature of the mobility zones, the efficiency of the enhancement process might be improved by the use of solvents such as naphtha or synthetic crudes. In this study numerical simulation was used to develop a communication enhancement process which involves the stimulation of production wells with hot water followed by hot water injection into the injection well. A reservoir description was assumed with initial mobility such that a steam drive process could not be started readily. Results of the study indicate that the communication path can be heated gradually using production wellbore stimulation and hot water injection. However, the process is not effective for low mobility zones. In the latter case organic solvents may be used to enhance the process. The study generally outlines the range of permeability thicknesses for which hot water can be used as an enhancement agent. The possibility of using CO2 as a viscosity reduction agent was also considered. Results show that CO2 injection cannot attain mobile conditions for the bitumen unless the reservoir pressure is sufficiently high. On the other hand, CO2 has an adverse effect on water injectivity; CO2 is not recommended as a communication enhancement agent unless sufficient high injection pressure is used.