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

Severe Sulphate Scaling: Short Duration 
If the sulphate problem is severe but is only believed to be of short duration 
with only low volumes (< 500 bbls per day) of water, then a single squeeze 
may be sufficient to protect the well through this “dangerous” scaling period. 
This scenario often arises when seawater is injected into the oil leg of a 
reservoir. Seawater injection into an aquifer below the oil leg tends to produce 
early water breakthrough much larger (FW/SW) volumes, at progressively 
larger SW cuts, over much longer periods of time – see previous section. 
2.7.3 Scale Monitoring 
The build-up of scale within facilities can be measured topside by using 
thermography. The investigation of scale down hole can be conducted with 
calliper and gamma logs (gamma log will show a positive response to sulphate 
scale) and also with downhole video equipment avoid confusion between 
casing collapse and mineral deposit build up. 
What will happen if you have a scale problem and continue production 
(carbonate/ sulphate)? 
•
The continued production of a scaling well will normally only result in 
formation of scale as a skin on the production tubing with little damage 
to the formation itself, as long as a squeeze treatment is applied soon 
after seawater is detected within the produced water samples. 
•
This statement must be qualified by the severity of the predicted scale 
that will form with continued production. 

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TOPIC 2: Oilfield Scale 
 
 
 
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What will happen if you have a scale problem and shut the well in (cross flow 
issues; carbonate/sulphate)? 
•
If a well has significant crossflow, then shutting in that well when there 
is significant water production is not advised since, during the shut-in 
period, crossflow of sulphate rich fluid may enter other parts of the 
formation which can result in scale formation within the formation itself. 
•
This effect has been observed on both vertical and horizontal wells 
within the North Sea basin by a number of operating companies. 
 

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TOPIC 3: Wax Deposition 
 
 
 
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NIVERSITY B41OA December 2018 v3