FEATURE

Subsurface temperatures and pressures in SAGD development

nergy are very hard on the pumping E

s equipment that brings

vu to the surface. o PHOTO: Cen

Hot and bothersome Quiet above ground, the extreme subsurface environment of thermal operations spurs evolution in artificial-lift technology for thermal developments

by Darrell Stonehouse

24 OILSANDS REVIEW | MAY 2010 Hot and bothersome When British writer Rudyard Kipling visited the southeastern Alberta city of Medicine Hat in 1907, he famously commented that “this part of the country seems to have all hell for a basement,” referring to the area’s prodigious natural gas resources lighting the streets and heating the homes and factories of the prairie city.

MAY 2010 | OILSANDSREVIEW.COM 25 FEATURE nergy E s vu o PHOTO: Cen is one of many in situ producers that have added electric submersible pumps to their operations.

One wonders if Kipling were alive today can also be pump-killers, as can high vol- what he would make of the underworld cre- umes of gas and produced water. ated by the thermal oilsands developments This extreme in situ environment has led to that are multiplying hundreds of kilometres an evolution of artificial-lift systems over the north of Medicine Hat in northern Alberta. last decade as producers and pump suppliers Temperature-wise, the underground experimented with a variety of technologies thermal chambers in steam assisted grav- aimed at securing efficient and cost-effective ity drainage (SAGD) operations can reach production. as high as 220 degrees Celsius. That’s hot In the early days of SAGD develop- enough to melt a tin can. In cyclic steam “Pull quote”  ment, “poor-boy” or traditional stimulation (CSS), bottomhole temperatures rod-and-tubing plunger pumps were the can reach 330 degrees Celsius. That’s hot ~ Person, Company artificial-lift systems of choice for oper- enough to melt a lead pipe. ators. The visible part of the rod-and-tubing While maybe not comparable to the system is the familiar pumpjack, common eternal fire of the metaphorical hell Kipling across Western Canada. A poor-boy gas lift referred to during his Medicine Hat visit, system pumps gas downhole through a pipe these temperatures are definitely hell on the into the production stream where it mixes downhole pumps used to artificially lift bitu- with the bitumen, lowering its viscosity and men in thermal oilsands developments. And allowing it to flow to the surface. the heat is only part of the challenge facing Both systems had issues. In many instan- pump manufacturers and operators working ces the gas-lift system had high upfront to create reliable production from the in situ costs for engineering well pads, and high resource base. ongoing operational costs for natural gas. Wild temperature swings from the sur- The traditional rod-and-tube system, the face, which can be as low as -40 degrees workhorse of the conventional oil industry, Celsuis during winter, also stress pumps. suffered reliability issues caused by the vis- Corrosive liquids and gases eat away at seals cosity of the bitumen, fluctuating flow rates, and coatings, seriously limiting pump life. and sand incursions. Abrasive sands wear down pump compon- The issues with the early artificial-lift sys- A engineer installs a REDA Hotline ESP on a ents. Inconsistent or intermittent flow rates SAGD well near Bonnyville, Alberta. tems caused operators to look at other

26 OILSANDS REVIEW | MAY 2010 FEATURE existing pumping mechanisms, including and shut down in high-temperature thermal electrical submersible pumps (ESPs) and operations. Temperature swings stressed S o progressing cavity pumps (PCPs). Early tests ur seals and bearings. Corrosion and abra- c using both pumping methods proved less S e: sion from fluids and sand also damaged the than stellar, with reliability issues and short chl pumps, shortening their useful lifespan. run-life common. But since then, pump sup- u Schlumberger began working with in situ oil- mb

pliers have re-engineered both systems. erger sands developers in the early 1990s in an effort Competition between technologies has now to develop a high-temperature ESP that would narrowed, with new-generation ESPs becom- function in this extreme downhole environment. ing the method of choice for lifting heated In 1996, the first REDA Hotline ESPs rated for 180 bitumen to the surface. But more recently, the degrees Celsius well conditions were installed PCPs are giving ESPs a run for their money. in SAGD operations. Many systems were sub- ESP systems have been in use since the sequently installed with run times of up to four 1940s in oilfields around the world. An ESP years (1,460 days) achieved. The limitations is made up of a series of centrifugal pumps to of the early systems were due to the maximum move fluids upwards to the surface, an elec- working temperature of the ESP, in particular the tric motor to drive the system, a protector to motor insulation materials. Since then, the com- keep fluids out of the motor, and a cable con- pany and its competitors have been continually necting the pump to the surface. improving high-temperature ESPs. Standard ESPs offered a number of poten- In 2003, the next generation of REDA tial advantages to early oilsands developers Hotline ESP pumps was introduced with a experimenting with the pumping system. The well temperature up to 218 degrees Celsius. instruments could handle the large volumes Downhole electric motors are now protected of liquids generated by SAGD wells, which from extreme temperatures by special insula- can produce hundreds of barrels of heavy oil tion rated up to 288 degrees Celsius (550 F). and thousands of barrels of water per day. Seals, bearings, and other mechanical parts They could meet lift parameters, providing have been re-engineered as well to allow for up to 10,000 feet of lift, and could function thermal expansion and to provide wear resist- in wells with long horizontal sections. But ance from sand and corrosive fluids. New- probably most importantly, ESPs worked in generation coatings provide added protection. low-pressure environments. This could allow Systems to handle gas and vapours have also operators to lower reservoir pressures after been added to enable effective gas and steam the initial buildup of the steam chamber in management and to improve pump perform- Schlumberger’s REDA SAGD operations, leading to lower steam-to- Hotline pump is an ance and production rates. oil ratios (SORs). The lower ratio can provide example of a high- Today there are over 200 REDA Hotline temperature ESP with large economic benefits. an abrasion-resistant ESPs in operation in Canadian SAGD wells But the existing ESP systems came with bearing system, helping with continually increasing run times. it work in the extreme some drawbacks as well. The standard in situ environment of Producers recognize the results these im- downhole electric motors tended to overheat thermal operations. proved pumps can bring. Cenovus Energy re-

The high-temperature electric

Manufacturers High Temperature Wide flow ranges Corrosion and Gas exclusion say that ESP temperatures swings Pumps include a abrasion Gas excluders have components have The pumps are New-generation ESP specially designed Special coatings self-orientating been redesigned specifically systems incorporate bearing system that help protect the intake ports with harder stage designed to tolerate special features allows for thermal new-generation designed to direct and bearing extreme bottomhole like oversized growth and wear ESP systems fluid flow to the materials to temperatures. oil reservoirs, resistance from against corrosion bottom side of the improve radial For example, ESP parallel-bladder abrasive production, and abrasion. horizontal wellbore, stability, special motors use special systems in the seal, allowing operations Specialized thus closing off coatings to high-temperature and specialized across a wide range mechanical seal possible entrance of help withstand insulation rated high-temperature of flow rates and designs enhance gas into the system. corrosion/abrasion, up to 288 degrees insulation designed through unstable or stability and reduce and improved Celsuis. to tolerate intermittent flow. the need to use insulation wide swings in elastomers. materials to temperature. endure extreme temperatures, improving reliability.

28 OILSANDS REVIEW | MAY 2010 FEATURE ports that ESPs have played a key role in improving the economics at Like ESPs, PCP systems offer a number of characteristics desir- its SAGD operations at Foster Creek and Christina Lake. able for thermal production. They can handle large volumes of flu- “One of the most significant technological improve- ids, are resistant to abrasives and solids, and can operate at the ments to our SAGD process has been the introduction of ESPs, depth of most in situ oilsands developments. They are also very cost rather than using natural gas, to bring the oil to the surface. efficient. The standard PCP’s one big downside, however, is that the We worked with various vendors to design and develop the pumps for stator component constructed from elastomers isn’t durable enough SAGD operations, which were introduced at Foster Creek in 2003,” says for SAGD operations. Cenovus. “One of the benefits of using ESPs is a reduction in our steam- “Elastomer stators make standard progressing cavity pumps un- to-oil ratio. A low SOR results in lower water usage, more efficient use of suitable for use at extremely hot temperatures,” says Nicolas Parise, steam, a reduction of emissions per barrel of oil recovered, and an overall director of the oil and gas unit for French pump manufacturer PCM. reduction in operating costs. At our Christina Lake project the reduction In 2008, after 10 years of experimentation in partnership with in SOR has shown a 15 per cent decrease in the amount of water we use producers in Alberta, PCM, and its Canadian sister company Kudu to produce one barrel of oil and a 12 per cent decrease in steam-genera- Industries, introduced an all-metal PCP system called the Vulcain tion costs.” designed for thermal heavy oil operations. The system can pump While ESPs now dominate the SAGD market, PCP suppliers have at temperatures of 350 degrees Celsius. It has been field tested at also been working on adapting their systems for thermal develop- Total’s SAGD leases in the Athabasca oilsands and at ’s ments. A PCP consists of a stator and a rotor. The stator is a helix Cold Lake CSS operations. In 2009, the company announced one of resembling a DNA molecule. The rotor, which resembles half a DNA its Vulcain pumps had been operating non-stop for 20 months in strand, is rotated within the stator using either a surface motor or the SAGD trial. It is has now been released for commercial use. a bottomhole motor. Turning the rotor within the stator creates cavities within the pump that sequentially pass produced fluids up- wards towards the surface.

SR

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