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Technology
Balanced cement plugs -
necessity & challenges
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There are a number of challenges which can be faced in cement plugging operations.
Emad Elfeki, well operations specialist, ADNOC Offshore, discusses the challenges associated with the balanced cement plugs operation, and how they can be addressed. HE MOST COMMON method used for the placement of cement plugs is the balanced plug method. It is used for applications such as: • Partial isolation of unfavourable zone producing water and decreasing well potential, where the zone is watered out and recompletion well is needed on a higher zone; • Securing risk rank wells and recompletion wells; • Plug and abandonment utilising coiled tubing operation. There are a number of challenges which can be faced during cement plugging. These include: • Losing all cement and formation still losing/gaining (plug failed) • Cement spread on the low side of most horizontal wells due to operational errors • Well completion string is plugged or partially restricted inside diameter due to
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incorrect implementation • The well is not completely pressure controlled, so there is a gain from the formation which goes into the cement while it is still green, causing channelling or contamination. Consequently the plug does not hold when it hardens, so the situation will need to be remedied. The cement will need to be squeezed, or redrilling will be required to reduce the height of cement, complete the job and secure
There are different approaches that can be adopted to ensure the cement plugging is successful first time.”
the well with proper isolation procedures, thus incurring extra costs and requiring additional time • High salinity or salt rocks could make Gclass cement lose its water and consequently flash set • If pumping pressure is not controlled, frac might occur • The existence of coral reefs or rocks, or casing shoe is not holding / free pipe • Communication between strings and casing • Unbleedable annular pressure with direct communication with the tubing string • Cavity and wash-outs in open wells is a challenge. Even extra designed slurry volume for slim hole will not be enough (hole updated calliper run is to be considered) Cement plugging is not new; it has been done since the beginning of the oil industry. However there are different approaches that
