Material Selection and Corrosion Management

Materials selection for plants is an important factor in product cost competitiveness, but in practice it tends to simply become an issue of “staying on the safe side” to assure stable operation and avoid equipment failure. Two reasons for this tendency are the difficulty of clearly defining operating environments and the lack of established measuring techniques for accurate determination of materials appropriate to a given operating environment. Corrosion is the effect of a complex interaction between the materials, the construction, and the chemical composition of the environment.

The integrity, safety and profitability of field developments depend on the correct materials being used in their construction, completion, and operation. The selection process requires accurate fluids data as well as expert assistance from corrosion and materials specialists. PetroPlat is capable in providing both crucial services. We review data from crude, gas, and brine samples to ensure they are representative of field conditions. Where necessary, the water chemistry is also modelled to calculate reservoir composition and back-out contamination from drilling and completion fluids.

This data is then analyzed using industry standard predictive corrosion software to consider corrosivity to carbon steel flow lines. Our tests consider any protective effects from hydrogen sulfide in the system, application of glycols, flow regime to establish top of line and bottom of line effects and variation with oil and water cut-over field life. Based on our assessments and flow regime data, the feasibility of a carbon steel line – with corrosion inhibitor applied, if necessary – is defined to establish material suitability as well as the corrosion allowance required during the field’s life. The severity of the carbon steel corrosion regime and expected inhibitor performance determines the requirements of corrosion resistant alloy (CRA).