Some of the wells in a North Sea field have a relatively low reservoir pressure. For those wells without gas lift installed, lifting heavy fluid out of the well when flowing back can be a problem. For this type of well, one of the options for the inhibitor squeeze treatments is to use a low density package to avoid pumping a large amount of relatively heavy brine based inhibitor. Through a research program, a polymer inhibitor and non aqueous solvent based package was developed for the squeeze treatments for the field.

This paper will present the detailed discussions of the chemistry of the formulation package. A number of scale inhibitors were screened for the suitability with a low density solvent as a carrying fluid. Due to both environmental concern and different function groups attached on the inhibitors, very limited inhibitor candidates were found to be suitable for being formulated into the low density package. The paper will further present the laboratory evaluation results such as product compatibility, inhibitor partitioning from solvent to brine phase, inhibitor efficiency as well as core flood data.

The paper will also present the field evaluation data. One well treated with this low density package squeezed a water based inhibitor with several times in the past. Due to the reservoir pressure depletion, the low density package was developed for the squeeze treatments. The same inhibitor used in the water based squeeze was formulated into the non-aqueous package. The field trial results show that none of the wells experienced lifting problems while back producing the inhibitor pill. In most of the wells, an improved oil production was seen and maintained for a while after the treatments. A possible mechanism for this will be discussed. In addition, a comparison was made between the treatments from the water based and non-aqueous squeezes.

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