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

2.5 Scale Prevention using Inhibitors 
The discussion above relates primarily to the diagnosis of various mineral 
scaling problems along with a practical discussion of some related field issues. 
In this section, we present an introductory discussion of the most widely used 
method of preventing topside and downhole mineral scale formation – that is, 
through the use of chemical scale inhibitors. 
The chemical structures of the commonly applied generic types of oilfield scale 
inhibitors are presented in Figures 5A and 5B. 
Figure 5A: Molecular Structure for Penta-Phosphonate (PETPMP) 

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TOPIC 2: Oilfield Scale 
 
 
 
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Figure 5B: Molecular Structure for Hexa- Phosphonate (PO-85) 
Inhibitor 
And again in Figure 6A and 6B
. 
 
Figure 6A: Molecular Structures for Polyacrylate Inhibitor

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TOPIC 2: Oilfield Scale 
 
 
 
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Figure 6B: Molecular Structure for Phosphino Polycarboxylate (PPCA) 
Inhibitor
In a given field situation, suitable scale inhibitors must be chosen, possibly 
through the comparative screening of a number of different products. 
These must then be applied at a suitable point in the topside plumbing, or 
must be applied downhole in a “squeeze” treatment, as explained below 
(Vetter, 1973; Vetter, 1975; Yuan, 1991; Mitchell, 1980; Vetter, 1982; Lindlof, 
1983). 
Note that, although the primary focus of this chapter is in treating the topside 
scaling problems, it is important to discuss this in the context of downhole 
squeeze treatments. 
The topside treatment will be linked in a number of respects to the downhole 
squeeze programme (if there is one), since the produced brines may be