Advances continue to be made into the squeeze application experience of Oil Soluble Scale Inhibitors (OSi). Recent challenges within the North Sea include applying the chemical to inhibit scale in brines with high calcium levels, produced from variable permeability, water sensitive reservoirs at temperatures up to 165°C. In some cases, additional constraints such as an effective limit on fluid injection pressure can also pose a challenge.

This paper is intended to outline the problems experienced in the Texaco Galley reservoir, from a historical laboratory and field perspective using traditional techniques, before going on to describe the use of an OSi package to solve the problems, increase reservoir recovery & impact on field economics. Firstly it will be described why effectively ‘dry’ Galley wells had to be treated at such an early stage due to uncertainty in the prediction of the water cut profile. Although reservoir simulation did predict reasonably early seawater breakthrough, intuitively it was felt that the actual progression might be more significant due to the presence of high permeability streaks.

A description of the laboratory study that was carried out to support the use of a traditional water based scale inhibitor for well 15/23a-G1 will be given. The subsequent field treatment, using a low molecular weight nonionic amphiphile package, additive free diesel (AFD) spacer, water based scale inhibitor and AFD overflush will be described. Pressure problems experienced during the treatment and the ultimate, permanent loss in well productivity will be shown.

Finally, a description of the laboratory study and core floods carried out to further investigate the application of an OSi package on a second, very similar well 15/23a-G3z, will be given. This section will highlight the realisation of the potential advantages of OSi over traditional treatments including: early scale inhibition; reduction of backpressure during injection; minimum deferred oil production; & most importantly increased productivity following treatment.

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