The project goal was to apply laser peening to oil and gas drilling hardware and equipment, evaluate specific areas where cracking initiates, and treat and test sample material and actual hardware.
This project was funded through DOE's Natural Gas and Oil Technology Partnership Program. The program establishes alliances that combine the resources and experience of the Nation's petroleum industry with the capabilities of the National Laboratories to expedite research, development, and demonstration of advanced technologies for improved natural gas and oil recovery.
Lawrence Livermore National Laboratory (LLNL)
University of California
Laser peening is bursting on the scene as a process that treats the surface of metal components to significantly reduce fatigue and stress corrosion cracking. A commercially viable laser and process technology was transferred to industry by LLNL in May 2002. This new technology immediately has been shown to bring enormous benefit to the airline industry with respect to eliminating crack growth in key jet engine components. It has solved a severe cracking problem that no other technology was able to do. Since initial deployment, the laser process has impacted over $25 billion worth of commercial jet aircraft by providing longer life spans for expensive jet engine fan blades. The process extends the useful lifetime of a $0.7 million set of fan blades by a factor of up to 20 times and converts a $500,000 engine teardown and rebuild every two months into a once-per-two-year requirement. The benefit/cost ratio for aircraft components is about 1000 to 1. The process now is expanding to solve an even broader group of problems. This project looks at the application to oilfield hardware and its potential for extending tool life.
The first major project goal was to determine the achievable life improvement of laser-peened welded four-point bend fatigue coupons compared with unpeened coupons. It appears that laser peening could be used to induce compressive stresses at selected regions inside and outside of the welded pipes.
The laser-peened treated pipes in both welded and unwelded sections demonstrated roughly four- to five-fold superiority over conventional methods.
The project tasks break out as:
Year 1, evaluation and sample treatment.
-Task 1, evaluation of gas and oil drilling mechanical failures. With experts from the drilling industry, LLNL is to identify equipment mechanical failures related to fatigue failure and stress corrosion and the materials and geometries involved and propose approaches to reduce those failures by laser peening.
-Task 2, treatment of sample materials. Researchers are to treat sample materials and complete fatigue and stress corrosion cracking tests to demonstrate the value of laser peening.
-Task 3, estimate benefit/cost ratio. With improved sample lifetime by laser peening, the lab can estimate value to the industry.
Year 2, treatment and testing of field components.
-Task 1, evaluation of actual components. LLNL is to evaluate how to treat actual hardware and design appropriate tooling for handling the large, heavy components.
-Task 2, treatment of actual components. Researchers are to build hardware to handle field components and treat a representative number for field testing.
-Task 3, evaluation of treatment. Work is to proceed with drilling contractors to test treated and untreated components to evaluate lifetime improvement and benefit/cost ratio.
Year 3, commercial deployment.
-Task 1, transfer to commercial production. LLNL is responsible for transferring treatment of components for initial commercial production treatment.
-Task 2, field testing. The project is to support field testing of commercially treated components.
-Task 3, upgrades, final review, and final reporting. Researchers are to upgrade any deficiencies resulting from field testing and complete final review and testing of a commercialized process.
The first major project goal was to determine the achievable life improvement of laser-peened welded four-point bend fatigue coupons compared with unpeened coupons. ExxonMobil, using a coupon geometry defined by LLNL and the University of California at Davis, CA (UCD), fabricated welded and base-metal coupons from ASTM A656 Grade 1 steel. Initial testing of the welded coupons was completed. Treating fatigue coupons with laser peening allows for an increase in applied stress of more than 20 ksi, while maintaining the same fatigue life-an order-of-magnitude increase in life at a particular test stress.
UCD has completed residual test models with matching geometries and planned complementary residual stress measurement for small cylindrical geometries. It appears that laser peening could be used to induce compressive stresses at selected regions inside and outside of the welded pipes.
The next step laid out in the project plan was the application of laser peening to cylindrical geometries. LLNL started with small, unwelded pipe sections with laser peening and residual stress measurements, followed by axial fatigue testing of small-diameter welded pipes, both laser peened and unpeened. The final goal is laser peening and fatigue testing large diameter (on the order of 18-inch) welded pipes. To date, ExxonMobil has provided several small-diameter pieces of both welded and unwelded pipe, which LLNL laser peened using a helical pattern. The laser-peened treated pipes in both welded and unwelded sections demonstrate roughly a four- to five-fold increase in fatigue life.
LLNL is to upgrade any deficiencies resulting from field testing and complete final review and testing of a commercialized process in the final year of the project.