Microbial Aspects of Corrosion

Abstract

Microbial Aspects of Corrosion

This is a brief paper to describe a case history described largely in photographs (not reprinted here), illustrating severe, and rapid, microbiologically-influenced corrosion (MIC) from a ground water aquifer used for oilfield pressure maintenance.

Facility Design

Water is commonly used in oil production to maintain an .adequate pressure in the reservoir or to drive (sweep) oil towards the producing wells, and. this application is known in the oil industry as Waterflood or Water Injection. With offshore oilfields, seawater is routinely used but occasionally aquifer water is used, and with onshore oilfields then it is aquifer water which is routinely used.

The project described here uses a shallow aquifer, only 40 metres below ground level.

The water is abstracted by electro-submersible pumps (ESPs), then fed, at 2 bar pressure through a short (800 metre) unlined carbon steel pipeline to a surge tank. From there it is pumped through coarse (80 micron) then fine filters (dual media, nominally 5 micron rating), then to high pressure water injection pumps, and on through unlined carbon steel pipelines to the water injection wells at 40 barg.

In order to protect the pipelines against oxygen corrosion, ammonium bisulphite oxygen scavenger was dosed into the water prior to the surge tank, and the surge tank was gas blanketed to prevent air/oxygen ingress.

To guard against bacterial problems, provision was made for dosing both sodium hypochlorite (from an electrochlorinator) and biocide just downstream of the source water wells.