Inspectioneering Journal

Practical Guide for Auditing a Chemical Treatment System in an Operating Oil and Gas Facility

By Abdulaziz Moshaweh, Senior Corrosion Engineer at Dolphin Energy. This article appears in the May/June 2020 issue of Inspectioneering Journal.


Chemical treatment is one of the most widely used corrosion control measures in the oil and gas industry. Chemicals range from corrosion inhibitors to biocides and water treatment. Out of the different corrosion control options, changing materials may or may not end up being more expensive than chemical treatment.

For an aging facility, where documents are missing and the operation depends heavily on experience rather than proper engineering designs, auditing a chemical treatment system is a rather challenging task for corrosion professionals.

This article presents a gap analysis that is developed after monitoring the chemical treatment systems in different facilities for more than six months. A structured approach to identify and close the gaps in any chemical system is outlined. This approach can be applied and tailored to fit any operating facility's chemical treatment needs.

Upon applying this approach, one facility saved more than 65% of its annual chemical treatment costs by reducing the corrosion inhibitor consumption by about 70%.

Typical Corrosion Inhibition Systems

A typical system consists of the following components:[1]

  1. Chemical storage tank: usually corrosion inhibitors are delivered pre-mixed, especially in remote and offshore facilities. In case they are not, tanks should be fitted with mixers.
  2. Strainers: strainers should be installed in all chemical injection systems between the tank and the metering pump to protect the pump from any debris or particles suspended in the corrosion inhibitor. Frequent cleaning of the strainers should be a normal practice in the facility. They should be installed as far upstream in the injection system as possible, i.e. after the chemical storage tank.
  3. Calibration columns, cylinders, pots: these columns are used for calibration of the injection rates periodically. They should be graduated clearly. Calibration should be performed whenever there is a change in the production flow rate or after any pump maintenance. The calibration columns should be vented to the atmosphere. Care should be taken when venting the columns; chemical should not spill over the cylinder or on the floor. Most of the calibration columns are made of PVC; while they are rugged, they get discolored, especially when under direct sunlight. Thus, tempered glass columns are preferred in such case. 

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