An Introduction to Flow Control Devices and the Potential Benefits to Geothermal Applications

摘要

Geothermal operators face several significant challenges in creating and maintaining optimal production from their wells. One of these challenges is the uniform distribution of both injected and produced fluid to and from the reservoir. Preferential production of fluid from one zone of a reservoir can result in thermal drawdown, reducing the temperature of the produced fluid. Additionally, the formation of direct pathways between injection and production wells, commonly referred to as "short-circuits", can heavily impact downhole heat transfer efficiency, particularly in Enhanced Geothermal System (EGS) operations. Thermal heavy oil producers, particularly those who use Steam Assisted Gravity Drainage (SAGD), face a very similar challenge (though reversed in terms of heat transfer). In SAGD operations, the injected steam needs to be uniformly distributed in the target oil reservoir, or the operators risk abating the area effectively heated by the steam. Additionally, there is a risk that some of the injected steam may flow directly to the production well, resulting in an inefficient reservoir heating process and similar short-circuiting. To help address this problem, SAGD operators have begun to employ Flow Control Devices (FCDs) to provide an effective means of well control. Though the concept of FCDs is not new, having been utilized in conventional Oil and Gas for many years, the widespread adoption of this technology in SAGD wells is relatively recent. The first commercial deployment of FCDs in a SAGD well was completed in 2009 by ConocoPhillips Corporation at their Surmont SAGD Project; however, in the last 10 years FCDs have since become more widely adopted. Several SAGD operators have reported significant process improvements since the introduction of FCDs, including: better reservoir conformance, more efficient production of oil (i.e. less water and energy use, and lower GHG emissions) and increased total production. Given the similarities between the challenges faced by SAGD and Geothermal operators, FCDs may be a viable technology to help mitigate imbalanced reservoir flow in Geothermal operations. In order to evaluate the potential of FCD technology for Geothermal applications, there are key differences between the operations of a SAGD well and a Geothermal well that need to be assessed. This paper will summarize the current state of commercially available FCDs and their operation, how FCDs are typically used in the Oil and Gas industry, and the potential benefits and limitations if operators used FCDs in the Geothermal industry.