Heavy-oil recovery from thin pay zones by electromagnetic heating

There are many heavy oil reservoirs with thin pay zones (less than 10 m). Conventional thermal recovery methods such as steam injection, are not cost effective for these thin reservoirs due to the excessive heat loss through the overburden. In order to minimize heat losses, it is necessary to have the ability to carry out controlled heating of the pay zone. One such way to introduce heat to the reservoir in a controlled manner is electromagnetic heating. This paper describes laboratory studies on electromagnetic heating of scaled thin heavy oil reservoir pay zone models. Combination of electromagnetic heating and gas injection with horizontal wells was studied. Higher electromagnetic frequencies provide faster heating rate and can overcome problems associated with discontinuity of the media through which electromagnetic waves must propagate in the reservoir. Heat loss can also be minimized with the use of higher frequencies. For moderately heavy oil reservoirs (less than 1000 mPs.s), it is not necessary to heat the entire pay zone. Heating of the wellbore vicinity is sufficient. Oil recoveries as high as 45% of OIIP (Original Oil in Place) were achieved using electromagnetic heating and gas injection compared to estimated primary recovery rates of less than 5%. The results obtained in this work clearly show that electromagnetic heating provides an effective mean of recovering heavy oil from reservoirs with thin pay zones.