Oil wells producing from carbonate formations generally experience chemical scaling (carbonates and/or sulfates) during some phase of their production history. In several Saudi Aramco vertical wells, production of formation water containing associated carbon dioxide gas has resulted in calcium carbonate scaling. Scaling potential studies have indicated the threshold level of an organic phosphonate scale inhibitor used to mitigate such scaling in these wells is less than one ppm. This low protection threshold allows considerable leeway in scale squeeze design for the problem wells. Phosphonate based scale inhibitor squeeze treatments provide the most common and effective means of preventing the scale formation in such fields. In vertical well applications, long squeeze lives of more than ten years have been observed in fields producing from carbonates. The residual inhibitor levels have fallen below 0.1 ppm in several of these wells without return of scale.

The increased drilling of horizontal holes and inevitable increases in watercut in these wells have led to scale problems. The design of a viable and economic horizontal well scale squeeze treatment was called for. Considerable problems are, however, inherent in the development of such horizontal treatment strategies. Sorbie, et al., recently published a mathematical scale inhibitor squeeze model for use in horizontal well treatments. This model was used to evaluate several treatment options for horizontal wells having a low carbonate scaling potential. Simulated residual returns and squeeze life data were used for different stages and scenarios in Sorbie's model to arrive at the most optimistic squeeze strategy. Based on the information provided by the model and previous vertical well experience, a simple and inexpensive bullheaded squeeze resulted in a successful treatment. This resulted in a substantial economic savings over a coiled-tubing delivered treatment. The theory behind this simple strategy will be discussed. The results of two case studies will be presented.

Keywords:
production chemistry, diesel, treatment strategy, scale formation, squeeze treatment, oilfield chemistry, upstream oil & gas, brine, remediation of hydrates, hydrate remediation
Subjects:
Production Chemistry, Metallurgy and Biology, Formation Evaluation & Management, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene, Completion Installation and Operations
Copyright 1999, Society of Petroleum Engineers
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