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It is widely known that for highly corrosive environment, corrosion-resistance alloy (CRA) is recommended as the production tubing material. This is because its alternative, carbon steel (CS) is prone to corrosion that leads to integrity issues such as tubing leak and tubing parted. However, CRA usage would increase well cost resulting in unattractive commercial implication especially for a marginal field development which tends to be very sensitive economically. This paper gathers the actual performance of various tubing materials that have been installed in a high CO2 oil field in Peninsular Malaysia, in which the findings would be used to determine a proper tubing material selection strategy for future development. Actual data from 30 years of production was collected and to be analyzed statistically. Each well's water cut trend was evaluated to establish relationship between producing water to the corrosion rate and metal loss in the presence of CO2. It is noted that some wells completed with CS both in single and dual completion are still producing with no leaks after 30 years. This case applies to either single string or dual string, with both strings are completed as producer. However, majority of active CS-completed wells require tubing pack off to overcome multiple leaks, especially in dual utility wells. Notably, wells that are completed with CRA e.g., 13 Cr are active with no possible leaks at all. Some wells which are completed with glass-reinforced epoxy (GRE) and higher grade of CRA; 22 & 25 Cr, also do not show any potential leaks or tubing integrity issue. It is proven and highly recommended to complete high CO2 fields with CRA material. Nevertheless, by understanding the well and reservoir performance, particularly on the effect of water cut in relation to general corrosion due to CO2, the use of more expensive materials can be optimized. This paper is to discuss, in the context of marginal field development where production life is relatively shorter and production rate is low, the consideration of deploying a cheaper material and/or less corrosion-resistant substances as the tubing material to make the development more commercially attractive or remain status quo with CRA. |
