Water in oil (w/o) formulations containing a range of scale inhibitors have been prepared for squeeze application. Depending on their composition these have been found to be either microemulsions or weakly structured mixtures.

A particular feature of the materials described is the type and concentration of surfactant used. High concentrations of surfactants are traditionally required to generate and stabilise conventional microemulsions. However, the back-production of the surfactants following a squeeze may cause undesirable process upsets. To minimise these upsets and to maximise the performance of the delivery technique, novel complexing agents, which, when combined with suitable scale inhibitors, form semi-stable species capable of stabilising w/o systems have been developed.

A detailed investigation of the properties of selected materials has been performed and experimental measurements including phase behaviour, reservoir condition coreflood tests and inhibitor desorption data are presented. A new technique which provides data in-line with core performance tests is also described.

The possibility to utilise the phase behaviour of these materials to increase squeeze life is also explored. Data for Miller Field conditions, showing an increase in squeeze life, are presented.

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