Well-Casing Protection Method Wins Patent

Husain M. Al-Mahrous of the Consulting Services Department of Saudi Aramco on March 30 was granted patent No. 6,712,139 by the U.S. Patent and Trademark Office for his "Method of Well Casing Cathodic Protection Optimization Using the Drill Stem Data."

His invention identifies corrosive zones as the producing well is being drilled. Then it optimizes the corrosion protection requirements without the need for running additional, expensive logs.

Al-Mahrous got the idea for his invention after concentrating on the analysis of drill stem data since 1998. "I thought as the analysis of the anode bed drill stem data helps identify low/high corrosivity spots along an anode hole, this same concept and method can be applied to the producing well itself," Al-Mahrous said. Currently, Cathodic Protection Evaluation Tool (CPET) logs are conducted to evaluate the need for corrosion protection and to determine the protection level that would be sufficient to protect the deepest corrosive zone.

Exact current and location of corrosive zones can only be identified with CPET logs. The practice has been to do only one CPET log at each new field and generalize the data gathered from that log to all wells in that field. Each log costs about $10,000.

Al-Mahrous' invention will provide clearer identification of the corrosive zones for each well and optimize corrosion protection to cover the corrosive zone of each well.

This new invention can result in developing a device whereby the drill stem resistances gathered during the well casing drilling operation will be used to optimize the corrosion protection of that well.

This graphic shows the use of the two-pin method to measure the drill-stem resistance of a well being drilled and to analyze the data to predict areas that have a higher tendency to corrode. The information gathered then is used to optimize the cathodic protection requirement.