Overview of Economic and Engineering Aspects of Corrosion in oil and Gas Production
Authors: Cron C.J. , Marsh G.A. 
Published: December 2007

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to informthe general readership of recent advances in various areas of petroleum engineering.

Introduction

Corrosion in oil and gas production has important economic aspects. The direct losses resulting from corrosion--i.e., the cost of replacing corroded parts--are often minor compared with indirect costs parts--are often minor compared with indirect costs such as the loss of revenue caused by lost ordeferred production. An exception is the case of offshore production. Anexception is the case of offshore production, where the direct loss resulting from production, where the direct loss resulting from corrosion of an offshore platform can be extremely expensive.

Many phases of oil and gas production are affected by corrosion. Two corrodents are responsible for problems found in the petroleum industry: dissolved problems found in the petroleum industry: dissolved oxygen and acidicspecies, most commonly CO2. Dissolved oxygen accounts for the corrosive nature of seawater and produced water and also for the corrosive nature of soil. CO2accounts for corrosion in many oil and gas wells. H2S, when present, rendersproblems with dissolved oxygen and CO2 even more serious. H2S also can introduce a serious cracking problem, sulfide stress cracking (SSC), when it contacts high- strength steel that is under stress. The combined action of acorrodent with cyclic (periodic) stress can result in corrosion fatigue, a problem often found in drillpipe and in the sucker rods of pumped wells.

Besides serious downhole corrosion problems associated with oil and gas production, corrosion problems also occur frequently during waterflood problems also occur frequently during waterflood operations in which produced water or seawater is injected. In each case corrosion-preventive measures are available(such as oxygen removal or corrosion- inhibitor injection), but they require careful application.

Corrosion resulting from corrosive soil is potentially serious for pipelines, tank bottoms, and well casings. An electrical method of corrosion control, cathodic protection, is often applicable to these cases. Offshore protection, is often applicable to these cases. Offshore platforms and related pipelines present severe potential platforms and related pipelines present severe potential corrosion problems that are controlled by coatings and by cathodic protection.

Corrosion is an economic as well as an engineering problem. The cost of corrosion to the worldwide problem. The cost of corrosion to the worldwide industry is staggering. For example, in a 1975 study, the annual cost of corrosion in the U.S. alone was estimated at $70 billion. Of this total, about15% or $10 billion was considered avoidable--i.e., could be saved through existing corrosion-control technology. The cost of corrosion in the petroleum industry no doubt represents a large fraction of the total cost.

Besides the economic importance of corrosion, two other aspects make corrosion control an urgent consideration: conservation and human safety. Corrosion represents a waste of valuable resources and requires care to ensure public safety and welfare. This paper examines both the economic and engineering paper examines both the economic and engineering aspects of corrosion and its control.

Economic Impact of Corrosion

Two types of losses are attributed to corrosion: direct and indirect. Direct losses are those that can be accounted for directly, such as replacement costs, including parts and labor, and protection costs such as the cost of alloying, corrosion inhibitors, coatings, cathodic protection, and R and D.

Indirect losses caused by corrosion failure can be far larger than directlosses.

JPT

P. 1033