ABSTRACT

Despite the unprecedented growth in the number of carbon capture and storage (CCS) projects, this figure needs to increase to meet global climate objectives. For this to happen, there is a need for corrosion testing of materials to be used in the CO2 injection wells. The present work tested several common corrosion resistant alloys (CRA) for the Acorn CCS project.

The conditions of CO2 injection wells were simulated using two types of testing with dense phase CO2 and the Acorn CO2 specification. The first test type simulated exposure to the CO2/water interface during a shut-in event after CO2 injection, at 80°C and 180 bar. The second test type simulated exposure during a short-term transient shut-in condition where the temperature was reduced to –15°C.

The results showed that the CRAs generally had good corrosion resistance in the tested environments. No cracks were observed but crevice corrosion attacks were commonly observed on nearly all materials. Some CRAs had in addition localised corrosion attacks that were 20 – 50 μm deep.

INTRODUCTION

The number of CCS projects (planned and in operation) is increasing, and project developers need to provide firm evidence that the proposed material is suitable for these applications.

The petroleum industry has long experience with materials selection for wells, but the conditions for CO2 injection wells are somewhat different from "conventional" oil and gas wells. This is due to the high CO2 content and pressure (up to several hundred bar) which results in low pH condensed water (exact value depends on pressure and temperature, but approximately pH 3.0). In addition, the injected CO2 is not typically "pure", meaning low concentrations of contaminants (impurities) may be present depending on the CO2 source and the capture technology employed. Some of these impurities are not normally present in "conventional" oil and gas operations.

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