Methodology for Selecting Corrosion Inhibitors for Wet, Offshore, All-Phases Pipelines
Authors: Asperger R.G. 
Published: October 2008

As wet pipelines become more widely used and understood, their real complexity becomes apparent. Corrosion control in them is achievable if the system is managed competently. A pipeline or a pipeline system is complex and requires the insight of several domain specialists to keep them from corroding. A machine based expert system is not yet available to help in the operational decision making to minimize internal corrosion. The best that one can do today is to utilize a systems analysis on the mentally segmented portions of the system and then to study the impact of the uniting of these segments into an integrated, operating system. The unit operations of the system maybe understood, but new problems are being recognized:top of the line corrosion; andthe complexities of keeping field corrosion inhibitor formulations of constant quality which are also appropriate for the ever changing conditions of the pipeline system which always occur over it's lifetime.

This paper reviews some unit operations, discusses some field experiences on wet sweet and sour pipelines and points to some future problems and opportunities.

INTRODUCTION

With the rapidly changing global economics and availability of both crude oil and natural gas, comes the need to rethink the methods for their production and transportation. This paper focuses on coping with pipelines and how wet products can be safely and economically carried in them at the bottom of oceans, in the mountains and over very hot plains. This focused review will begin with a historical assessment. It will proceed to a discussion of applications technology for inhibitors and the issues involved in determining if laboratory evaluations and field monitoring data are correct at all times and places along the pipeline. It will be pointed out how a systems approach involves, among other things, thinking about the corrosion changes occurring in pipelines over time. These changes are caused by either anticipated or surprising changes in reservoirs fluids production, their well's workovers, and changes of production protocols in the fields to which a pipeline is dedicated. If additions or subtractions are made to a pipeline network, the system has been chancfed. The corrosion control protocol must be rethought from first principles using a systems approach. Because of surprising changes in wet systems, an annual review of each pipeline network is good and sound engineering practice for all regions of the world.

Historical

Years: 1800–1930 Wet pipelines have transported fuel gases since the early 1800's. They were usually low pressure lines and were treated to remove contaminants which were thought to be harmful to the pipelines. An early process is still used today to remove H2S in low concentrations. It is based on the reaction of wet HS with iron oxides which are usually finely divided particles distributed on a solid substrate. No C02 or vaporized water were removed.

Years: 1930 1987. Modern techniques were introduced to process corrosive, wet gas being carried in large diameter steel pipelines.