EQUIPMENT/ENGINEERING: Industry effort to improve monitoring of corrosion in deepwater pipelines

The systems that monitor oil and gas production and the corrosion of pipelines in deepwater must be fail-safe and in place when the flow lines are installed on the ocean floor, stated Dr. Andrea Ethridge, Senior Consultant for InterCorr International, Inc. Corrosion-related failures, or excessive corrosion rates at today's tremendous oil production depths can be extremely expensive if left unchecked and can be potentially dangerous to the environment, Etheridge explains.

A new joint industry program, launched in April by InterCorr International, Inc. and Shell Global Solutions (US) (division of Shell Oil Products company), will investigate cost-effective and reliable systems for monitoring corrosion and flow assurance in subsea pipelines. In addition to Shell, other oil companies taking a lead role in developing the program are BP, Intevep-PVDSA, the R&D arm of Venezuela's national oil company, and Petrobras, the national oil company of Brazil. Input gained through two focus group meetings with these and other companies has helped to develop the scope of work for this major joint industry development effort.

"We expect to have 10-15 participants in the program, including oil and gas producers, major suppliers, and service companies," says Etheridge. "Those who sign early - within 90 days after the program starts - will save about 25% of the cost to participate," she says. "Our experience has shown that most companies recoup their participation costs in this type of program with only a single application of the technology."

Deepwater monitoring

Offshore oil comes from the ground in flowlines at high temperature, but then is rapidly cooled by deepwater at low temperatures once it is in the subsea pipeline. This can cause precipitation of water that increases corrosivity and can also cause deposition of waxy substances, both of which can jeopardize flow, system integrity, and ongoing operations. Until recently, producers saw the rate of flow and corrosion of pipelines as independent problems. The new InterCorr/Shell Global study will address both concerns and provide a common solution, says Etheridge.

One of the problems currently experienced by deepwater operators is that only limited monitoring options are available today and none have been proven in deepwater service. The major purpose of the InterCorr program will be to integrate several monitoring capabilities into a single unit and verify their performance under simulated deepwater conditions in advance of a field trial.

The new program will develop an enhanced, multifunctional monitoring capability that integrates existing high-reliability technologies capable of monitoring corrosion and flow assurance. This system will be adaptable to subsea, pipe-in-pipe, insulated or buried flowlines. The program will also provide a demonstration of long-term system performance and reliability under simulated deepwater conditions.

Effective corrosion monitoring and flow assurance of subsea flowline installations remains a challenge. In deepwater projects, flow lines are the most capital-intensive parts of the project. In the Gulf of Mexico and many other field developments around the world, these lines are made from carbon and low alloy steels to minimize costs. However, to achieve this cost benefit, the carbon and low alloy steels must be adequately protected against corrosion by chemical inhibitors and must be monitored for sand erosion, scaling, and organic solids deposition, which jeopardize production.

Excessive deterioration or loss of flow can lead to lost production, failure, or repair. The consequences in deepwater can range from very expensive to cost prohibitive. Therefore, it is critical to develop pipeline monitoring capabilities for deepwater systems. Etheridge said the new monitoring and corrosion control system will be designed around the following anticipated requirements:

• Continuous corrosion rate measurements and wall thickness data at multiple points of interest
• Rapid response monitoring capabilities for both general and localized corrosion
• Multi-functional capabilities that also include monitoring of flow, sand erosion and scale/organic solids deposition
• Effective and reliable operations in deepwater environments
• Interface with existing hardware systems for field production monitoring
• Reliable transmission of data at regular intervals using modern telemetry technology.

Dr. Andrea Etheridge can be contracted by Tel: (011-44-207-538-4982) or email aetheridge@intercorr.com.