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Artificial lift design for heavy oil systems is a continual changing process in which evolving technological advancements coupled with constant learning experience has led to production capabilities that were not feasible in the past. There has been an increase in installation of temperature tolerant Electric Submersible pumps (ESP) with the primary aim of improving deliverability from mature heavy oil fields. Similarly, in the heavy oil industry, the desire to attain energy efficiency has birthed variations of the Steam Assisted Gravity Drainage (SAGD) process that use solvent additives in further reducing bitumen viscosity. The heavy oil emulsion formed in these systems exhibit rheological characteristics and outflow behaviors different to conventional SAGD systems. Tubing hydraulic performance, steam trap requirements and flow assurance behaviors associated with production from these systems are investigated in this work. This paper presents dynamic multiphase simulations detailing fluid flow regimes, mass and heat transfer mechanisms and pressure/temperature changes as the reservoir fluid flows out of the reservoir, through an ESP and up the production tubing to the surface. The reservoir is a 3D fully coupled reservoir/wellbore model with properties similar to the Athabasca bitumen reservoir. The simulation was conducted considering all periods in the lifecycle of production i.e. pre and post ramp up. This research finds that a detailed understanding of fluid phase behavior and reservoir operating parameters during the different periods can dramatically improve operating efficiency and impact on ESP design. Furthermore, results generated from this research can be used as a yardstick for SAGD production engineers in designing artificial lift systems for solvent assisted processes
Artificial lift design for heavy oil systems is a continual changing process in which evolving technological advancements coupled with constant learning experience has led to production capabilities that were not feasible in the past. There has been an increase in installation of temperature tolerant Electric Submersible pumps (ESP) with the primary aim of improving deliverability from mature heavy oil fields. Similarly, in the heavy oil industry, the desire to attain energy efficiency has birthed variations of the Steam Assisted Gravity Drainage (SAGD) process that use solvent additives in further reducing bitumen viscosity. The heavy oil emulsion formed in these systems exhibit rheological characteristics and outflow behaviors different to conventional SAGD systems. Tubing hydraulic performance, steam trap requirements and flow assurance behaviors associated with production from these systems are investigated in this work. This paper presents dynamic multiphase simulations detailing fluid flow regimes, mass and heat transfer mechanisms and pressure/temperature changes as the reservoir fluid flows out of the reservoir, through an ESP and up the production tubing to the surface. The reservoir is a 3D fully coupled reservoir/wellbore model with properties similar to the Athabasca bitumen reservoir. The simulation was conducted considering all periods in the lifecycle of production i.e. pre and post ramp up. This research finds that a detailed understanding of fluid phase behavior and reservoir operating parameters during the different periods can dramatically improve operating efficiency and impact on ESP design. Furthermore, results generated from this research can be used as a yardstick for SAGD production engineers in designing artificial lift systems for solvent assisted processes
This paper summarizes the work of the exploratory phase of a Joint Industry Project (JIP) investigating operational instabilities and ‘no flow’ events observed in a large number of Steam Assisted Gravity Drainage (SAGD) wells produced with ESPs, where, while the ESP is operating, flow to surface suddenly stops. The impact of these events to the SAGD operations has included lost production due to downtime and reduced drawdown, additional stresses to the ESP due to operating without flow for extended periods and repeated shut-downs and restarts and some system failures. The primary objectives of this exploratory phase were to better understand the mechanisms and key factors responsible for these no flow events, to identify possible mitigation actions, which may be in the wellbore trajectory, ESP landing position, ESP system component designs, or operating practices. This work was structured as a series of progressive, inter-related tasks, using a combination of analytical models and Computational Fluid Dynamics (CFD), to systematically examine the components of an ESP completion and to narrow-in on the primary contributing factors. The approach was adopted in an effort to assess if the instabilities were due to flow conditions upstream of the ESP, past the ESP, through the intake or in the initial stages of the pump. For each step of the analysis, the output boundary conditions of an upstream analysis became the input boundary conditions of the corresponding downstream assessment. First, a combination of one-dimensional (1D) multiphase flow and multiphase CFD models were used to characterize the fluid conditions and flow behaviour in the lateral and heel of the well below the ESP. Second, flow past the ESP motor was examined using CFD models to examine the impact of motor heating on subcool reduction and steam vapour generation. CFD simulations were also used to examine fluid separation and flow into a bottom feeder ESP intake to assess the amount of non-condensable gas (NCG) entering the ESP and if the pressure drop through the intake was sufficient to cause significant steam vapour flashing. Finally, a representative SAGD ESP stage was analyzed using both a broad suite of analytical surge models to assess the stability of the pump given the gas-liquid fraction entering the pump, as well as CFD simulations of the rotating stage. The focus of the CFD assessment within the entrance and first stage of the pump was to determine whether vapour flashing was occurring within the ESP stage and the apparent impact on the stage’s ability to generate head. The results from this exploratory phase of the JIP indicated that vapour flashing within the ESP impeller due to insufficient required Net Positive Suction Head (NPSHr) appeared to be one of the dominant mechanisms causing no flow events, as opposed to NCG or steam entering the pump from the intake. Future work for this JIP includes validation of the CFD results using lab test data, further CFD simulations of other ESP stage designs and at a wider range of operating conditions, and examination of alternate ESP designs that may allow for production at lower subcool and lower NPSHr values.
It has been about 10 years since High Temperature Electrical Submersible Pumps (HT ESPs) were first deployed at downhole temperatures of 250°C (482°F). Since then, these pumps have become one of the most popular forms of artificial lift for most Steam Assisted Gravity Drainage (SAGD) producers. Despite this popularity, the severity of the operating conditions in SAGD wells continues to present challenges to the development of new HT ESP technology. A Joint Industry Project (JIP) of major thermal operators commissioned this research to evaluate the performance of some novel HT ESP technology that was developed by Summit ESP a Halliburton Company. This novel HT ESP technology was specifically designed to operate in a SAGD environment. This paper describes the full-scale testing that was independently conducted by the JIP on this HT ESP technology using a specialized high temperature flow loop at C-FER. Testing was completed to better understand the performance and reliability of this novel HT ESP technology over a wide range of representative SAGD conditions. The program included several diverse tests conducted at fluid temperatures up to 250°C (482°F). This included a wide range of operating conditions, including low levels of sub cool and different multiphase fluid combinations with oil, water, gas, and steam. As noted in past experimental work conducted on HT ESPs by Waldner et al. (2012), understanding the thermal profile of the ESP system (specifically the motor) as well as the effect of multiphase flow conditions on motor heat dissipation and pump hydraulic performance when operating in a SAGD wellbore are key considerations when assessing ESP systems. For this reason, additional downhole instruments were installed to monitor the temperature profile of the ESP system in the wellbore during this test. The experimental setup also included internal pressure monitoring of the ESP motor oil volume compensation system to carefully observe the interactions between the wellbore environment and ESP system performance. This paper presents an overview of the test objectives, the experimental setup (including the instrumentation), the HT ESP system, as well as a selection of key laboratory test results. Collectively this paper provides insight into the test methodology and performance of this new HT ESP under various conditions representative of a SAGD wellbore in the field. Technical Categories: ESP Thermal Operations, New ESP Technologies
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