New Sour Gas Corrosion Inhibitor Compatible with Kinetic Hydrate Inhibitor
Authors: Menendez C. M. , Jardine J. , Mok W. Y. , Ramachandran S. , Jovancicevic V. , Bhattacharya A. 
Published: May 2016

The presence of hydrogen sulfide in high pressure gas systems causes several complications. Sour gas corrosion is a major concern in the oil and gas industry due to the presence of localized corrosion. At high pressures and low temperatures hydrates can occur. Sour gas decreases the pressure and increases the temperature at which hydrate formation occurs. Operators have used both corrosion inhibitors and kinetic hydrate inhibitors to decrease the capital requirements of developing sour high pressure gas systems. The development of sour gas corrosion inhibitors that are compatible with kinetic hydrate inhibitors is a major requirement for qualifying corrosion inhibitors for these applications.

This paper describes laboratory work on the development of a new corrosion inhibitor by performing various performance and compatibility tests with kinetic hydrate inhibitor. The new corrosion inhibitor needed to meet various additional requirements which made the development process even more complex. The partitioning of a corrosion inhibitor between the oil and water phases has a significant impact on inhibitor selection and treatment strategy. General corrosion performance was addressed using mass loss and electrochemical data. Evaluation of localized attack was performed using vertical scanning interferometry (VSI). The main advantage of this approach is in providing quantitative data for product performance differentiation in the presence of localized corrosion.

Introduction

The production and transportation of oil and gas fluids in remote locations as well as under sever climate conditions can present major technical challenges to operators1. This is because of the inherent characteristics of produced fluids, which can lead to operational issues such as corrosion, hydrate occurrence, scaling, wax and/or paraffin deposition2–5. Changes to the properties of produced fluids over the life cycle of an asset can also introduce operational complications. Consequently, a thorough consideration of these various issues is necessary in order to maintain flow assurance and assets integrity during the lifetime of a producing field.

The transportation of unprocessed fluids from offshore to onshore processing facilities is an attractive economic incentive since significant capital savings can be achieved. This kind of operational practice can bring along the potential risks of corrosion and hydrate formation in wet gas transportation systems6. The main cause of these problems is the presence of water, and dissolved in it acid gases like carbon dioxide (CO2) and/or hydrogen sulfide (H2S) which generates a highly corrosive environment. The presence of organic acids and other dissolved species can greatly enhance the corrosively of produced fluids as well. A significant amount of H2S can be present in sour systems; however, the general corrosion rate of carbon steel is generally low due to the presence of a semi-protective iron sulfide film on the surface. The main mode of corrosion in this case is localized attack or pitting. A viable solution to control this type of corrosion attack is the application of corrosion inhibitors to provide protection of carbon steels.