New Low-Hydrogen Stick Electrode Helps Pipeline Contractor

Using a new low-hydrogen stick electrode has helped a contractor improve productivity, reduce costs and beat the construction deadline on a carbon-dioxide pipeline constructed of 24-inch by 0.469-inch, API 5L X80 steel.

With increasing global energy demand and fluctuating oil prices, there is renewed interest in maximizing known energy resources. With a focus on maximizing crude oil reserves, enhanced oil recovery (EOR) methods were developed to recover up to 30-60% of a field’s original oil reserves.

In one EOR process, carbon dioxide (CO-2) pushes additional oil to a production well. CO-2 injection is one of the most efficient methods for enhanced oil recovery. Transporting the CO-2 to an oil field is accomplished through high-pressure pipelines. Welding on these pipelines can be challenging, making the selection of a low-hydrogen welding consumable critical.

Progressive Pipeline Inc., of Meridian, MS recently used low-hydrogen vertical-down electrodes for the construction of a CO-2 pipeline owned and operated by Denbury Onshore LLC, a wholly owned subsidiary of Denbury Resources Inc., an oil and gas company headquartered in Plano, TX. Using Lincoln Electric’s Pipeliner® LH-D100 electrode, the company beat the construction schedule and achieved a 15-20% increase in productivity on the pipeline, which runs 80 miles from Tinsley, MS to Delhi, LA.

The Emergence Of CO-2 Pipelines
It is important to understand the role CO-2 plays in enhanced oil recovery. The CO-2 is transported through a pipeline in dense phase from a CO-2 source to an injection well. The CO-2 is injected into the oil reservoir where it mixes with oil droplets, expands them and moves them to producing wells. The CO-2 also reduces the viscosity of the oil, which helps remove the oil from the reservoir formation.

The production stream consists of oil, water and CO-2. On the surface, production components are separated. The oil is sold, produced water is disposed of and the CO-2 is recycled and re-injected into the reservoir. After the process is completed, the CO-2 can be injected and sequestered in the oil reservoir. In the future, CO-2 EOR should become an important process supporting carbon capture and sequestration, while producing crude oil that would not otherwise be produced.

The construction of the CO-2 pipeline is critical to this type of oil recovery. The pipeline in this specific case is constructed of 24-inch x 0.469-inch API 5L X80 steel. It is designed to operate under a maximum pressure of 2,160 psi, making the integrity of the welds critical.

Why Is The Consumable Important?
High-strength steel enables gas pipelines to withstand higher operating pressures and achieve higher throughput. It may also allow for a reduction in wall thickness which reduces costs associated with hauling and handling of material, as well as in time spent welding the pipe. However, the move to higher strength steels results in a greater susceptibility to weld metal hydrogen-assisted cracking (HAC). Manufacturers, such as Lincoln Electric, have focused on developing low-hydrogen vertical-down (LH-D) electrodes that address this challenge, while providing increased productivity, greater Charpy V-notch impact toughness and reduced repair rates.