Pipeline Border Crossing

Matching Right Rig For The Job Ensures Success
January 2009 Vol. 64 No. 1

In order to tackle the really long bores, Dolan makes sure his 70 employees have adequate equipment. For the ONEOK project, Dolan used his recently purchased Vermeer D500x500 Navigator rig to drill a 5,000 foot shot that stretched underneath the Red River, which flows east and forms the border between Oklahoma and Texas.

“It was a nice river crossing and a nice length, and it gave us the opportunity to get our 500,000 pound rig out there so that we could stretch it out a little bit,” Dolan says.

The 5,000 foot bore was just one portion of the project that Dolan Directional Drilling was involved with. In all, the company will install about 40,000 feet of the 12 inch gas pipeline. Other subcontractors have been hired to simultaneously complete the other spreads.

As with any HDD job, proper planning can be the difference between success and failure. Because this bore was unique in its length and the fact that Dolan and his crews would be crossing state lines, they spent four days shooting survey and setting up their wire line grid. Once their bore plan was in place, they turned their attention to bringing in the equipment.

Crews set up the D500x500 in the middle of a rural field in Texas about 1,800 feet south of the Red River and then drilled up to the river and underneath it. “There was some pretty rough terrain and we weren’t going to be able to dig on the other side of the river. That’s why the bore had to be 5,000 feet long,” Dolan says.

Changing soils

Typically, when contractors drill shorter bores, they encounter only one or two soil changes. But with a bore nearly a mile long with varying depths and crossing under a river, Dolan and his crews had to navigate through many different soils, including sand, clay, sandstone, gravel and caliche.

To begin, Dolan Directional Drilling placed a mud motor with an 11 inch TCI drill bit on the D500x500 to shoot the entire bore. “The mud mix changed as the ground conditions changed, but primarily we had a bentonite mix,” Dolan says.

For most of the bore, work was routine. It wasn’t until they had crossed north under the Red River with just about 900 feet remaining that they faced the first real obstacle. While the soil conditions had been somewhat favorable with sand, clay and sandstone leading up to the river, they soon changed to gravel and caliche as the drill head worked its way north into Oklahoma. “We hit a gravel bed and lost our returns, so it made it challenging in trying to keep up with the mud,” Dolan says. “It was difficult keeping the mud mix flowing fast enough to be able to drill, which slowed us down a little bit.”