Quantifying Heat Requirements for SAGD Start-up Phase: Steam Injection and Electrical Heating

Paper Number: WHOC11-513

Authors: B. Moini, N. Edmunds - Laricina Energy Ltd.

Source: This paper was prepared for presentation at the 2011 World Heavy Oil Congress held in Edmonton, Alberta, Canada, March 14-17, 2011.

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A proper and effective start-up of Steam-Assisted Gravity Drainage (SAGD) well pairs is a key parameter to its performance. A number of investigations have been conducted on the optimum start-up strategy and operational procedures; however, fewer studies have modelled the heat requirements of the process. This paper offers a simple method to calculate the required heat flux inside the wellbore to achieve a certain temperature outside the liner. Heat transfer problems are described using available equations in literature which are numerically solved. Two different approaches are investigated: a) variable heat flux (such as steam volumes injected) to maintain a constant desired temperature at the wellbore wall, and b) constant heat flux (such as an electrical element located inside the wellbore) to gradually increase and finally reach a desired temperature outside the wellbore. The results for a simplified model, using a 178 mm (7”) OD liner, 800 m long, under steam injection are presented. For electrical heating, elements with electrical powers of 500 W/m to 1000 W/m are studied to calculate the time required to gradually heat the wellbore wall to a desired temperature. This paper offers a method to calculate the minimum amount of heat required to keep the wellbore hot either by steam injection or through newer technologies of electrical heating of wellbores, where the minimum electrical power requirement is unknown.

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