B41oa oil and Gas Processing Section a flow Assurance Heriot-Watt University

Mechanical Removal/Remediation Methods 
 
If chemical methods of mineral scale removal cannot be made to work then, in 
order to improve well productivity, it may be necessary to resort to physical 
means of removing scale. A brief review of some of the approaches which 
have been taken in the UK sector of the North Sea is presented below. 
Mechanical Remediation Method: Reperforation 
Reperforation bypasses the scale and remediates scale formation 
Reperforation of the formation is only recommended when severe scale 
problems have developed, either within the formation itself, or within 
perforation tunnels. If this situation were allowed to develop, then well 
productivity would be seriously impaired. In such a case, the only options are 
abandonment or reperforation. 
Mechanical Remediation Method: Fracturing 
Formation fracturing again bypasses the scale and remediates scale 
formation. Fracturing of the near wellbore region is a common method of 
increasing productivity of damaged or low productivity wells. 
In the case of fracturing a scaled-up formation, the nature of the scale itself 
may affect the outcome of such a treatment. For example, if the damage is 
due to sulphate-type scale, then the fracturing approach may work quite well. 
However, in the case of carbonate scale (which has formed in the formation 
itself due to excessive drawdown), fracturing may only give a short term 
improvement since the fractures themselves will have a strong drawdown 
along their length and may therefore encourages further carbonate scale 
formation. 
In this event the fractures would very rapidly re-scale in the formation giving 
only a short term solution to the carbonate scale formation damage problems. 
This has been experienced by an operating company in Alaska. 
Mechanical Removal Method: Milling 
Milling (on coiled tubing) will physically remove the scale. Milling of mineral 
scale deposits using coiled tubing (for downhole applications) is only 
recommend if the scale itself is very insoluble to chemical removal methods 
i.e. for barium sulphate scale. 

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TOPIC 2: Oilfield Scale 
 
 
 
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NIVERSITY B41OA December 2018 v3 
Mechanical milling is expensive and is only recommended if a downtime 
saving is clearly demonstrated over chemical removal methods, or if the 
chemical removal methods are unsuccessful.