Abstract

The Fadhili Formation located in the Awali Field, Bahrain is a carbonate reservoir with an active water drive. Five horizontal gas-lifted wells drilled in the Fadhili with initial production rates of over 1500 BOPD began showing scaling symptoms once watercut rates increased to over 90% within a year. The scaling was found to be largely problematic as wells descaled with acid would find reoccurrences within 4 months of any treatment. Calcium carbonate scale found in both production tubing and flowlines would not only hamper production, but also damage flowline valves and leak as a result of the frequent descaling. The purpose of this study was not only to reduce the frequency of costly acid stimulation treatments, but to also inhibit the growth of scale and successfully allow for the conversion of these gas-lifted wells to annular lift without the risk of scale growth in the casing. This was done firstly by testing the extent of scale growth within the tubing and flowline through an integrated approach of combining fluid chemical analysis, system mass balance, and pipeline simulation. Differing scale inhibition methods were then considered before continuous treatment through gas lift injection was selected. Finally, an extensive production selection was then carried out to identify the optimal inhibitor composition and concentration. This paper displays a simple and low cost approach through which scale growth should be identified, classified, and then dealt with.

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