Mark Wright is a busy man. As a general superintendent for the pipeline contractor Driver Pipeline Company Inc. in Dallas, Texas, he currently oversees the installation of more than 70,000 ft. (21,336 m) of natural gas lines.
“Sometimes it’s like running around with your hair on fire,” said Wright, who has been in the pipeline business for 29 years, including six with Driver Pipeline.
Business is brisk for the pipeline contractor because, like many Texas pipeline contractors, a portion of the company’s work now includes installing lines for natural gas companies drilling the Barnett Shale.
The Barnett Shale is a geologic formation underneath a 17-county area in north Texas. It is the largest natural-gas-producing field in the state. In 2005 alone, it produced 485 billion cu. ft. of natural gas, enough to heat 6.7 million homes. In the northern county of Tarrant, drilling of the natural gas field produced approximately 115 billion cu. ft. of natural gas, according to the Railroad Commission of Texas.
“Many different exploration production companies have come in, and that offered our business more opportunity,” said Scott Driver, president of Driver Pipeline. “We ramped up with more trenchers and more people to do the work.”
In fact, Driver said the company has been buying rock trenchers steadily since 2000 to keep up with the increased workload. The company has six Vermeer track trencher units — three T755 units, two T1055 units and a T655.
“We have found that the cost of excavating the linear foot of ditch is less expensive with a rock trencher than an excavator,” Driver explained. He also noted that trenchers create spoil with small particles of 1 to 2 in., which makes it easier for the company to use it as backfill.
“If you dig with an excavator, the spoil is four- to six-inch sized, and you end up having to haul a lot of it off,” Driver said.
Laying pipes for gas companies tapping the shale poses an array of challenges.
One is location. Driver noted that a large gas deposit sits directly under the city of Fort Worth, the Tarrant County seat. Natural gas wells stand in vacant lots and backyards, and alongside railroad tracks and roads.
Working in urban locations is nothing new for Driver Pipeline, which has provided line installation services for 35 years. The company’s primary business is installing gas and electric lines in the Dallas/Fort Worth metroplex and suburbs. This experience made the company a perfect match for Barnett Shale work.
When Wright was given the task of overseeing a job just south of downtown Fort Worth, he knew what to do.
Like much of the company’s Barnett Shale work, the job included running gathering systems from wells to compressor stations. The stations recompress the gas to the required pressure for it to continue down the line.
Then, Driver Pipeline crews run pipes to the gas company’s sell point.
Wright explained that his crew places sections of the steel pipe to the side of the trench line and welds them together before digging begins.
Once the trencher starts digging, the crew waits until it is approximately 2,000 ft. (610 m) ahead before it starts to lay the pipe, Wright explained.
Digging 9,000 ft. (2,743 m) of trench with a Vermeer T1055 track trencher, Wright said soil conditions on the Fort Worth job were surprisingly merciful for most of the work.
Using carbide teeth in a standard V-pattern formation, Wright’s crew didn’t lose a single tooth. Production rates for the job were relatively low, however, because the crew had to run lines parallel to a railroad track and then through horse pens and backyards.
They even had to dig through trash.
“When we got to the one end of the job going up to the well bed, it was filled with concrete, tires and cars,” Wright said of the trench. “We dug through it, but then we would have to pull stuff out with a backhoe.”
Wright’s crew was able to clear the area and properly dispose of the debris.
His 12-man crew ran a 10-in. (25.4 cm) and a 4-in. (10.2 cm) steel pipe parallel in the same trench. The two lines required a trench depth of 6 ft. (1.8 m) and a width of 32 in. (81.3 cm).
One pipe was a gas line and the other was a line for water returns. Operators at the Barnett Shale use water to fracture formations and release natural gas. When the water returns to the surface after a fracture, gas companies often recapture and use the water at other sites.
Getting through backyards and under roadways would not have been possible without assistance from directional drilling equipment. While Wright was able to trench with the T1055 for the majority of the Fort Worth job, he brought in a Vermeer D100 x 120 horizontal directional drill to continue under roadways and creek crossings. “We wouldn’t have been able to cross the street without it,” Wright stated.
Forty miles north of Fort Worth, in Decatur, Texas, another Driver Pipeline crew used the D100 x 120 to drill through a “mountain.”
“We call anything in Texas higher than 102 feet a mountain,” Wright said.
While installing approximately 8,000 ft. (2,438 m) of 8-in. (20.3 cm) steel line with risers and block valves, Wright’s crew came across a sudden change in elevation of approximately 60 ft. (18.3 m). Wright brought in the horizontal directional drill to bore a length of approximately 1,600 ft. (488 m) through the hill.
For the majority of the Decatur run, however, Wright depended on the Vermeer T755 track trencher to dig a trench 18-in. (46 cm) wide by 6-ft. (1.8 m) deep. He faced tough soil conditions and relied on the machine’s 66,000 lb. (29,937 kg) weight and 250 hp engine to cut through limestone.
Having equipment that can handle difficult soil conditions is essential in Texas, which was once a prehistoric ocean bed. The soil, filled with limestone, clay, granite and sandstone, is often ruthless on equipment. Driver said that the limestone can be 2,000 psi and higher.
“As the material gets harder, an excavator just won’t cut it — the rock trencher does,” he said.
On the Decatur job, Wright again used carbide teeth in the standard V formation to grind through the rock. Because of the limestone, Wright’s crew went through approximately 15 teeth a day.
“Which isn’t so unusual considering the conditions,” Wright said.
Production rates for the two jobs varied depending on the soil condition and location. Wright said at times the nine- to 12-man crews averaged 2,000 ft. per 10-hour day. In the urban settings, where they had to stop and change machines to go under streets and utilities, crews achieved 500 ft. (152 m) a day.
Typically, pipeline jobs on the Barnett Shale take three to four weeks to complete, Driver said. Time is money when a typical oil-field gathering job averages $100,000, and as soon as one job ends, another one starts. The machines must forge ahead.
“Durability and routine maintenance go hand-in-hand,” Driver said.
Talking on the phone as he drove to another job location, Wright agreed. “We put them through the mill,” he said, adding that the Vermeer units keep on working. Just like he does.