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Heavy lifting, Part 1

Published by
Oilfield Technology,


Norman Liley, Zilift, UK, examines the growing importance of artificial lift as heavy oil production continues to grow.

Last year, the global artificial lift market was worth over US$ 9.3 billion in revenue and this figure is expected to reach US$ 16 billion by 2018.1 Astonishingly, research suggests that some of the world’s largest reserves in over thirty countries are heavy oil reservoirs with oil in place equal to the largest conventional oil fields in the Middle East.

The main challenge in heavy oil is not in finding resources; the viscosity of heavy oil creates challenges for total recovery and economic production as well as selling the heavy crudes within often changing economic guidelines.

Under stable market conditions, heavy oil assets have the potential to generate many years of steady cash flow, typically producing for more than 50 years. However, when the energy ratio needed to produce and upgrade a barrel of heavy oil can be as high as 40%, balancing economics throughout the project is a challenge.

The significant operating investment in recovering heavy oil necessitates robust oil prices to financially justify heavy oil operations.

The need for artificial lift

At present a variety of steam-assisted methods are used to tackle the challenges of mobilising heavy oils and improve inflow to the well; however another issue that arises is an increased production of sand from unconsolidated formations. This in turn leads to a large proportion of failures of current artificial lift systems due to erosion or ‘sanding in’ of pumps, or downhole motors overheating in the absence of fluid for cooling.

Four trillion bbls of heavy and extra heavy oil has been discovered worldwide to date and dwindling reserves of conventional oil continue to drive a need to improve the efficiency of production technology for heavy and extra heavy oil. Artificial lift has been an established method for thousands of wells in North America and is now being applied more widely as reservoir pressures decline.

In the early life of conventional oil wells the reservoir pressure is often sufficient to drive the oil up to the wellhead and then onwards to the production facilities. As the reservoir pressure declines, it no longer has the energy to drive production to the surface without assistance. It is at this stage that methods such as gas lift, or the use of electrical submersible pumps (ESP) are needed to maintain and enhance production of well fluids.

Towards late life, gas wells tend to cease production due to being overwhelmed by liquid accumulation. To address this, the industry has used downhole pumps with one traditional solution being a sucker rod pump driven by rod string and surface pump-jack. Due to a number of effects there is a limit to the depth that these devices can operate and are almost unusable in deviated wells due to rod wear. They are unsightly, noisy and have a surface dynamic seal that inevitably leaks hydrocarbons to the environment.

References

1. MarketsandMarkets of Dallas.

Part 2 of this article can be reached here.

Part 3 of this article can be reached here.

Adapted by David Bizley

Read the article online at: https://www.oilfieldtechnology.com/exploration/07112013/heavy_lifting_part_1/

 

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