Flow Control Devices (FCDs) have demonstrated significant potential for improving recovery in Steam Assisted Gravity Drainage (SAGD) production wells. One initial hypothesis was that steam breakthrough was delayed because the FCDs better homogenized injection and production by equalizing flow and compensating for pressure changes along the wellbore. However, in many cases, the field results were far greater than such an approach would have justified. The actual physics for this process are unclear, and not demonstrated in literature. Upon review of field data published by ConocoPhillips, the possibility of a steam blocking effect was proposed (Stalder, 2012), although the physical basis for this effect was not explored. This paper proposes an updated hypothesis to explain this effect, presents preliminary data to support the assumption, and introduces a new apparatus and methodology to characterize FCDs for SAGD applications. The traditional approach to steam control states that steam flashing at the producer should be avoided, as it will eventually lead to a completion failure. Alternatively, the proposed hypothesis contemplates using steam flashing at the producer to regulate flow in various segments of the completion, thus better enforcing conformance. The physics of this process will primarily be described analytically; however, this effect was also observed qualitatively in a small-scale experiment where water was flashed across an orifice. In order to design SAGD completions that leverage FCDs (and this effect), it was necessary to accurately characterize different FCDs under these challenging multiphase flow conditions. Since vendors use a variety of approaches when designing their FCDs, a protocol was developed to create a characterization procedure which was independent of the underlying FCD design and architecture, resulting in a direct comparison of the overall performance of each FCD. Part of this protocol required the construction of a new, high temperature multiphase flow loop capable of subjecting FCDs to representative SAGD operating conditions. Through fine control of the relevant test parameters, accurate performance measurements can be obtained for each FCD. This paper will present some information regarding the design and specifications of this new flow loop, as well as impart some of the lessons learned from its commissioning and initial operation.
The successful development and implementation of high temperature Electric Submersible Pump (ESP) technology for Steam Assisted Gravity Drainage (SAGD) applications has allowed operators to reduce their flowing bottom-hole pressures and achieve higher production rates. However, operating under these conditions brings the Pump Intake Pressure (PIP) closer to the saturation pressure of steam, which can result in live-steam production through the pump. The effect that live-steam has on pump performance is not particularly well understood, and has been a key challenge for operators when designing and optimizing ESP systems for SAGD applications.In early 2011, ConocoPhillips, Baker Hughes and C-FER Technologies embarked on an experimental test program to determine the consequences of producing live-steam through a centrifugal pump. This new program was meant to build on multi-phase work that had begun over a decade ago at the University of Tulsa (TU), where researchers had focused on experimentally measuring the two-phase flow performance of ESP stages with air and at moderate temperatures [Pessoa and Prado 2001]. The TU work ultimately resulted in a wave of new technology aimed at increasing ESP gas handling capabilities.Following a similar testing and ESP instrumentation philosophy, this new collaboration looked to build upon the TU experiments and expand the test fluids to include live-steam, water, and air at higher temperatures.This ultimately involved the design and construction of a unique high temperature Steam Flow Loop that allows for live-steam injection into a centrifugal pump, while monitoring both head and performance degradation. This paper will reveal some of the unique test results collected with the first pumping system, including snapshots of the stage-by-stage pressure contributions captured in real-time as air or air and steam migrates through the ESP being tested. These results also demonstrate the impact the presence of other gases can have on steam flashing and how it is important to consider both the gas and steam vapor effects in SAGD ESP designs. How Two-Phase Flow Affects a Multi-Stage Centrifugal PumpThe difficulties in pumping a two-phase liquid with a centrifugal pump (such as an ESP) generally arise from the large difference in density between the two phases. As the fluid enters the impeller eye, the buoyant force on the gas bubbles pushes them toward the low pressure area in the center of the pump; while the drag force on the bubbles acts in the same direction as the fluid flow through the stage, thereby having an effect of carrying the bubbles through the stage. If the buoyant force is very large or if the drag force is too small, retarded gas flow through the stage can result in an accumulation of gas near the center of the pump. The size of the bubble can then grow to a point where it reduces the capacity of the impeller, as a result of the gas phase interfering with the movement of the liquid through the fluid passages. For the purposes of this paper, this phenomenon will be
Summary The successful development and implementation of high-temperature electrical-submersible-pump (ESP) technology for steam-assisted-gravity-drainage (SAGD) applications have enabled operators to reduce their flowing bottomhole pressures and achieve higher production rates. However, operating under these conditions brings the pump-intake pressure (PIP) closer to the saturation pressure of steam, which can result in live-steam production through the pump. The effect that live-steam has on pump performance is not well-understood, and has been a key challenge for operators when designing and optimizing ESP systems for SAGD applications. In early 2011, ConocoPhillips, Baker Hughes, and C-FER Technologies (herein referred to as the operator, manufacturer, and independent laboratory, respectively) embarked on an experimental test program to determine the consequences of producing live steam through a centrifugal pump. This new program was meant to build on multiphase work that had begun more than a decade ago at the University of Tulsa, where researchers had focused on experimentally measuring the two-phase-flow performance of ESP stages with air at moderate temperatures (Pessoa and Prado 2003). The University of Tulsa work ultimately resulted in a wave of new technology aimed at increasing ESP gas-handling capabilities. Following a similar testing and ESP-instrumentation philosophy, this new collaboration looked to build upon the University of Tulsa experiments and expand the test fluids to include live steam, water, and air at higher temperatures. This ultimately involved the design and construction of a unique high-temperature-steam flow loop that enables live-steam injection into a centrifugal pump, while monitoring both head and performance degradation. This paper will reveal some of the unique test results collected with the first pumping system, including snapshots of the stage-by-stage pressure contributions captured in real time as air or air and steam migrated through the ESP being tested. These results also demonstrate the impact that other gases can have on steam flashing and the importance of considering gas- and steam-vapor effects in SAGD-ESP designs.
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