- Buyer's guide
Energy Growth Fuels Large HDD Rig Boom
“Many bores are in rural mountainous areas,” Lamb said. “The distance between a bore’s entry and exit may only be 1,000 to 3,000 linear feet, but it takes an hour to get from one end to the other. Matted roads up to a mile long are often required to gain truck access to the drill sites.”
Marcellus shale with multi-layered strata and multiple fractured formations vary in depth with hardness ranging in compressive strengths of 10,000 to 30,000 psi, he said.
“Fractured formations complicate production and increase chances of frac-outs,” he continued. “Steering through multiple layers with drastically different hardnesses is difficult and creates situations where the pilot wants to follow the path of least resistance, making it difficult to hold radius. These formations require careful downhole tool management, including inspecting drill strings and downhole tools for abrasive wear and tracking hours on tools to minimize the potential for failures during construction.”
Elevation changes pose steering challenges, Lamb added, and create mud management issues and increase the risk of frac-outs.
“Frac-outs,” he said, “can occur as far as 500 feet left or right of the drill alignment, requiring large areas to be monitored for inadvertent returns (IRs). The HDD crossings are usually under and/or near creeks and rivers that have been slowly cutting through the different layers of rock along the face of the terrain. There are seams of sediment in between layers of rock that allow the drill fluid to travel through the strata for long distances. Therefore, the drilling fluid can reach the surface at the areas where the erosion has exposed the layers along the edge of the river.”
Drill sites in wetland areas raise environmental issues, and construction and related activities have a high public profile because of controversies about natural gas collection issues.
USA’s work on HDD crossings ends with completion of pipe installation. Typically the mainline contractor welds sections of pipe together into a string for the HDD contractor to pull in and makes final connections to the mainline to complete the project.
Several recent USA projects illustrate the complexities of HDD installations in energy shale.
Project 1: Installing 1,920 linear feet of 16-inch steel pipe under low-level terrain and crossing a river.
Elevation changes: 320 vertical feet entry to exit; 420 vertical feet, bottom to exit.
Drill rig: Vermeer D330x500 developing 330,000 pounds of pullback.