Characterizing environmentally-assisted cracking and corrosion in field environments through laboratory testing presents an ongoing challenge to the oil and gas industry. As laboratory equipment is rarely capable of precisely recreating field conditions in oil and gas production wells, qualification of materials for service is typically carried out using (often simplified) laboratory simulations. Focusing on elevated temperature and pressure conditions, this paper will briefly identify the choices of field parameters that are relevant for laboratory simulations and explore different laboratory approaches to establish and maintain the target environment.

The effects of acid gases on materials are frequently defined by acid gas partial pressures, but the impact may be more closely related to either dissolved acid gas concentrations, acid gas fugacities, or the chemical activity of the acid gases in solution. This paper will explain how partial pressures, dissolved acid gas concentrations, and acid gas fugacities deviate from each other as the temperature and pressure of the system are increased and discusses how a lower pressure laboratory simulation can be designed based on an assessment of the field parameter chosen for the simulation.

When designing the experiment to simulate specific environmental conditions, various methods to achieve target acid gas loading may be deployed, such as (1) continuous purge of mixed gases, (2) purge-and-heat approaches, (3) sequential loading of constituent gases, and (4) loading of certain molar quantity of the constituent gases. Using thermodynamic modeling, the authors will demonstrate some of the temperature and pressure limitations of certain of these approaches and provide recommendations for conducting proper experiments. Examples will be given for standard test environments and field simulations with a brief review of how a laboratory test simulation relates – and does not relate - to the actual field environment in terms of parameters mentioned previously..

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