Artificial Lift systems for Steam Assisted Gravity Drainage (SAGD)

Many early SAGD wells were produced by rod or tubing pumps or by the use of “poor boy” gas lift. Today, Electric Submersible Pump (ESP) systems have been developed that can handle high production rates at high temperatures. Flow rates can be optimized using variable speed drives.  ESP solutions can operate under low bottomhole pressure, which means that less energy (and cost) is required to produce steam. They also offer construction savings since the design of the pad and facilities need not be based around gas lift.

In some locations, such as parts of Venezuela, heat dissipated from the ESP is used to reduce the viscosity of fluids passing through it – see article.

Such systems, typically applicable in wells between 160 and 212 degF (70 - 100 degC) are often kick-started with the help of a diluent to maintain flow until the heat of the motor sufficiently lowers the viscosity of the heavy oil. Schlumberger uses P, T, vibration and current measurements from the Phoenix multisensor, combined with espWatcher remote real-time surveillance, to automatically optimize flow through these systems. Most Canadian oil is too viscous for the use of systems that exploit heat from the ESP.

 ESP’s have been around for about 70 years, but is has required considerable research and development (R&D) effort to deliver ESP systems suitable for high temperature applications such as SAGD wells. According to Allan Peats, the Schlumberger commitment to R&D, and its established processes and systems, enabled and accelerated the ongoing ESP development process started by REDA. Schlumberger identified a client need and a growing market requiring new fit-for-purpose technology. “We set new goals and challenged convention”, he said. “We looked for and found new materials from the aerospace industry and used new design technology and computer modeling to minimize the time taken to develop effective solutions”. Innovative solutions included the use of metal bellows in the protectors, which helps maintain system integrity within the hostile downhole environment. The result was the Hotline 550 ESP system, which includes pumps, protectors, gas & vapor handling devices, motors and cables for reliable, continuous service at wellbore temperatures up to 456 degF (218 degC).

 SAGD applications have much in common with geothermal energy applications, steam flood fields and High Pressure High Temperature (HPHT) requirements; however SAGD has the additional challenge of moving viscous fluids at low pressures.

Hotline 550 system installations have, to date, delivered run times in excess of 1100 days. Allan Peats recalls that ten years ago, people would not have expected such equipment longevity even in conventional wells. The statistics improve every day, and Alan predicts that in the next 18 to 24 months the industry will have a sufficient installed base of units to conduct meaningful long-term statistical analysis to determine Hotline system longevity.

 Schlumberger is responding to client requests to further expand the temperature rating of the Hotline ESP system. Work is currently underway to design and test the equipment for higher temperature environments.

 SENSA fiber-optic technology is used in some SAGD wells to measure temperatures, typically at 1m (3.3-ft) intervals. Episodic bursts of steam can be detected and pump speeds adjusted accordingly – avoiding steam break-through into the producer. Schlumberger is currently testing new PT gauge technology for use at very high temperatures. Combined with control systems and variable speed pumps, this will provide the opportunity to greatly improve the optimization of production rates from SAGD fields.

 Solutions tried and tested in Alberta are likely to spread worldwide as the use of SAGD expands into new areas such as Venezuela, China, the Middle East and Alaska.  In addition, there will be new challenges and opportunities relating to carbonate heavy oil reservoirs. 

 Future developments will require integrated solutions involving AL for heavy oil will need to particularly address (1) system reliability & longevity and (2) monitoring and control.  The more measurements we can take, the better we will be able to adjust parameters and extend the life of the hardware. Today’s expert manpower shortages reinforce the need for more automated systems using timely data to action effective control.  

Read about other artificial lift methods.