Michels Directional Crossings successfully completed a complex, highly publicised horizontal directional drilling crossing underneath the Atchafalaya River and the accompanying levee system in central Louisiana, US.

The nearly one-mile Atchafalaya drill was one of the last of a total of 15 horizontal directional drilling (HDD) installations that Michels ultimately completed on the Acadian Haynesville Extension Project, a 270 mile natural gas pipeline that originates in the Haynesville Shale in Red River Parish, Louisiana, and terminates near Donaldsonville, Louisiana.

The Haynesville Extension Project will expand the existing Acadian Gas Pipeline System, which is owned by Acadian Gas LLC, a jointly-owned subsidiary of Enterprise Products Partners L.P. and Duncan Energy Partners L.P. The project will increase market share for existing customers, connect the service to new markets, and add more than 200 MMcf/d of new customers along the route.

Michels Directional Crossings completed the Atchafalaya River drill for Michels Pipeline Construction, which was the prime contractor for spreads 3 and 4 of the Acadian Haynesville Extension Project. Michels Directional Crossings completed a total of seven drills for Michels Pipeline Construction and a total of ten drills for Willbros Group, Inc., the prime contractor for spreads 1 and 2.

Careful crossing

Crossing the Atchafalaya River was of extreme importance as the river is classified as a navigable channel of the Mississippi River and has been a significant project of the US Army Corps of Engineers for over a century. As a primary industrial shipping channel and the cultural heart of Cajun Country, maintaining the integrity of Atchafalaya, the levee system and the surrounding environment has been a primary issue for the Corps.

Because of this, any utility lines designed for crossing the waterway and levee system must undergo significant planning. Any state-of-the-art equipment and methods must be submitted to and approved by the Corps of Engineers.

If the Mississippi River were allowed to flow freely, the Atchafalaya would not be merely a distributary of the Mississippi – it would be the Mississippi itself. Instead, the Atchafalaya provides an important alternate path to the Gulf of Mexico while the current arrangement of dams and spillways allows the Mississippi to feed Baton Rouge and New Orleans.

The Atchafalaya Basin also plays an important role in protecting those cities – the Corps of Engineers can open the Morganza Spillway in order to relieve pressure on the levee system and protect Baton Rouge and New Orleans from major flooding. The Corps did just that in May, releasing roughly 52 per cent of the Mississippi River flow and leaving ten per cent of Louisiana flooded, primarily in the Atchafalaya Basin.

A difficult challenge overcome

The controversial opening delayed the Atchafalaya installation and put the project on an extremely tight timeline. This made an already difficult challenge – previous attempts to drill and place utility lines underneath the Atchafalaya have encountered failures due mostly to difficulty with hole stability in the sandy, silty soils – even more difficult.

With that setting as the backdrop and evidence of the past failed HDD attempts visible in the form of pipe bridges spanning over the river, Michels began work in mid-July using Corps-approved technology and methods, which included pilot hole intersect technology and annular pressure monitoring through sensitive zones designated beneath the levee areas on either side of the Atchafalaya. While working underneath the watchful eye of the Corps of Engineers, it did not take much more than a week for the two sides to meet 104 ft below the riverbed.

From there, Michels’ vast experience with the conditions helped the project team hold the hole open during larger reaming passes which is where others had failed.

“People ask me, ‘What’s the difference between you guys and them?’” Michels Project Manager Larry Shilman said. “You don't want it to come off the wrong way, but it’s our people. It’s our experience. We’ve seen this stuff before and we know how to deal with it.”

The 36 inch diameter Atchafalaya drill ultimately spanned 4,993 ft and was one of four drills Michels Directional Crossings completed on spread 4. Michels completed one drill on spread 3 – a 42 inch crossing – and nine more 42 inch crossings on spreads 1 and 2. Michels completed one other 36 inch crossing on spread 1.

While the Atchafalaya drill was the most technically difficult of the 15 drills, Michels broke the one-mile mark on two other occasions: once in Kingston, Louisiana, while drilling under the Kansas City Railroad (5,325 ft), and once in Boyce, Louisiana, while bypassing the Boise Cascade (5,340 ft). All told, Michels’ 15 HDD installations spanned more than 10.2 miles.

The Acadian Haynesville Extension Project was completed this fall.