Prediction for steam chamber development and production performance in SAGD process

Abstract

Understanding steam chamber development of the steam assisted gravity drainage (SAGD) is important to predict SAGD production performance. In early research, a number of investigations have been conducted on the steam chamber development process and SAGD production performance separately. Although there must be some links between steam chamber development and SAGD production performance, as to our knowledge, few studies have been published to build a relationship between them. This paper proposes a new analytical model to predict steam chamber development process and SAGD production performance simultaneously. Comparisons have been made between the new model results and STARS (a mature commercial reservoir numerical simulator) results for a specific super-heavy oil reservoir case in Canada and similarity is observed. According to previous numerical and experimental research, we assume that the steam chamber shape is a combination of two symmetrical parabolas rather than an inverted triangle. The oil production rate is expressed by the steam chamber expansion rate as a function of reservoir properties as well as production and injection parameters. An energy balance equation is employed to connect the steam expansion rate and heat loss rate to surrounding formation (overburden, underburden, and formation ahead of steam chamber). With the parabola-shape assumption and energy balance equation, the steam expansion rate is calculated. Meanwhile, some key production parameters, such as oil production rate and steam oil ratio are predicted. With the help of the new model, a quick decision can be made for the SAGD production limit, such as the least reservoir thickness, or the least mobile oil saturation.