A multifaceted approach was used to address the corrosion inhibition program in Esso Resources Canada Limited's Redwater field. In the laboratory, inhibitor performance was measured by linear polarization and film persistency wheel tests. Both techniques produced similar inhibitor ranking, although the percent protection results were consistently higher for the linear polarization technique. In the field, corrosion rates were monitored by several devices. Metal loss measurements from flush strip electrical resistance probes best correlated to weight loss coupons, although the instrument's calculated corrosion rates did not agree with the indicated metal loss. To improve application efficiency, inhibitor and tracer concentrations were monitored during batch circulation well treatments. The concentration measurements showed that circulation time is the controlling factor in effectively batch treating wells that have high annular fluid levels. The foregoing investigations, which provided vital information for corrosion control in a specific field, also point the way to improvements in corrosion inhibition technology.


Esso Resources Canada Limited's Redwater oilfield, located northeast of Edmonton, Alberta, has experienced increased failure frequencies in the past five years due to internal corrosion in its production facilities. Previous efforts to control corrosion included reviewing failure history, monitoring corrosion by weight loss coupons, and predicting inhibitor return using ammonium thiocyanate as a chemical tracer. These efforts met with mixed success. To better address the corrosion problem, Esso Resources Canada Limited, Esso Chemical Canada and Exxon Chemical Company initiated a joint research project to optimize the corrosion inhibition program.

This project employed a multi-faceted approach. Inhibitor performance was determined in the laboratory using film persistency wheel tests and linear polarization measurements. Then, at the wellhead, the response to the inhibition treatment was measured using common techniques of corrosion monitoring. This also provided a basis for comparing the various monitoring methods. Finally, to improve inhibitor application efficiency, inhibitor and tracer concentrations were monitored during batch-circulation well treatments.

Experimental Procedure
Laboratory Measurements

The performance of four organic oil-dispersible/water-dispersible, film-forming inhibitors was measured using film persistency wheel tests and linear polarization techniques. Each inhibitors was evaluated using commercially available "as sold" strengths. The test concentrations were set at 500 ppm, 1500 ppm and 4500 ppm. Test fluids for both methods consisted of uninhibited produced brine and crude oil from Redwater. Samples were separated into oil and water fractions and stored in inert containers. For subsequent use, the oil and water phases were purged with carbon dioxide (> 99.99%) a minimum of six hours. A portion of the original aqueous phase was purged with hydrogen sulfide for two hours, measured for concentration, and recombined with the carbon dioxide saturated fluids to give a final concentration of 450 ppm hydrogen sulfide and an oil/water ratio of 7%/93%.

Film Persistency Wheel Tests

The wheel tests were performed by an independent consulting firm specializing in that method of corrosion inhibitor evaluation. (The detailed procedure is included in Appendix A.) Each inhibitor was run in triplicate at each of the three concentrations for 24 and 72 hours.

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