Design, Optimization and Operation of SAGD Wells Using Dynamic Flow Simulations

Abstract

Abstract Canada has the third largest oil reserves in the world and attracts a global attention because the majority of the reserves are bitumen and heavy oil production in western Canada. Steam assisted gravity drainage (SAGD) has been the established method to produce the bitumen and heavy oil. As the number of applications of SAGD continues to increase in Canada, there is an ongoing evolution and implementation of new technologies including those related to new improvements in design, optimization and operation. One of these new approaches involves the application of a dynamic multiphase flow simulator. Dynamic multiphase flow simulation has been widely used around the world for conventional oil and gas production since the 1990s for primarily offshore applications related to flow assurance issues. It has been used since 2012 for simulating SAGD wells, mainly in Canada. Dynamic simulation has been used to design SAGD wells, look at normal production and to identify and mitigate problems for both injector and producer wells in pre-circulation phase (also called pre-heating phase, or early-period). For the pre-circulation phase when steam is circulated in both wells (injector and producer), dynamic flow simulation shows how the wellbore (casing, cement and formation) is heated from the beginning of steam injection. As well, this simulation makes possible to verify the displacement of water in liquid phase by the steam as a function of time, identifying places where it is cumulated together with its impact on the temperature profile (inside and outside of well). In addition, for shut-in events, transient analysis combined with field data can help to estimate the thermal properties of formation (e.g. thermal conductivity) and steam leakage to the reservoir. For normal production operation, dynamic flow simulation can be used to evaluate the efficiency of steam injection to the formation by considering different steam splitters configurations and to determine the required injection pressure at wellhead. As well, for a producer pad (with all wells having electric submersible pumps installed), simulation shows how some operational parameters (such as flow rate, pressure and temperature at wellheads and separator) are influenced during different shut-in and start-up operations. In summary, this paper shows the value of dynamic flow simulations in improving SAGD subsurface systems and operations.