Encana extends capacity of directional drilling
When Encana Oil & Gas (USA) was trying to figure out how to drill for the natural gas beneath a narrow box canyon north of Parachute, it was time for some out-of-the-box thinking.
The company’s solution? It drilled a remarkable 50-plus wells directionally from one well pad of just 4.6 acres. As a result, it developed about 640 acres of underground resources — the amount contained in a square mile — from a single location, based on underground well densities of as much as one every 10 acres. That’s the most wells that Frank Merendino, Encana’s drilling manager for its North Parachute Ranch property, believes has been drilled from an onshore pad anywhere in the United States.
“The reason they’re all here is to drain this massive area … without impacting the environment,” Merendino said as he surveyed the well pad. In the distance behind it, a long, thin waterfall coursed from the rim at the canyon head. It’s one of seven falls on the 45,000-acre ranch property.
The directional drilling prevented the cost and visual impact of trying to build pads on the canyon cliff sides, or drilling through a few extra thousand feet of earth from surrounding plateaus and having to locate pads near the rim, where possible spills into the canyon would be a concern.
Encana’s effort won it a Colorado Oil and Gas Conservation Commission award this summer. It also is appreciated by state wildlife officials because of the reduced disturbance of habitat.
Encana’s accomplishment reflects oil and gas technology’s continuing evolution, said Dean Riggs, assistant regional manager for Colorado Parks and Wildlife in Grand Junction.
“Many, many moons ago, we used to have one well per gas pad,” Riggs said.
Riggs took over as the manager of the wildlife area that includes Encana’s North Parachute project eight years ago, and back then four wells on a pad was probably normal in the region, he said.
“Eight wells per pad eight years ago was a big deal,” he said.
Directional drilling started to become more commonplace years ago in Garfield County largely as an effort to address concerns from residents and others about the plethora of well pads that had begun to checkerboard the landscape. But as companies such as Encana began to implement it more extensively, they found ways to make it economically advantageous, applying approaches commonly used on offshore rigs to onshore situations.
The rig for the job
Encana and Williams, the two largest gas producers in the Piceance Basin, worked with rig companies to create “fit-for-purpose” rigs. The rigs are designed to allow for drilling of numerous wells from a pad and for simultaneous operations under which wells are completed and put into production even as drilling continues on the pad. Rigs can be moved from spot to spot on the pad to drill each well without having to be disassembled. The latter method can cost $250,000 to $500,000 and takes days, compared to just a few hours to move the specially designed rigs, Merendino said.
The rigs used by Encana incorporate hydraulically driven systems that lift the four corners of the rig and slide it in varying directions in up to 3-foot increments before setting the rig down, advancing the lifters and moving the rig again. Encana calls them “stomper” systems because of the up-and-down movements of sliding a rig forward.
Directional drilling and simultaneous operation methods developed by companies such as Encana and Williams in the Piceance Basin are being incorporated elsewhere in the country, Merendino said.
Encana came up with a quad configuration in which it drills a set of four wells spaced 8 feet apart in a square, then moves the rig 20 feet and works on another quad.
“That allowed us to know eventually we would get 32 wells on a pad, two pads per (square-mile) section,” Merendino said. “That was just incredible to even think anybody could do it. That was just unheard of onshore anywhere.”
Then, faced with some tight canyons in the North Parachute Ranch property Encana bought from Unocal in 2004, it looked at whether it could develop even more wells from one pad.
Encana ended up drilling 52 wells from the pad for which it won the award, although it had to plug one of them because of a technical failure, Merendino said.
He said a 32-well pad is now the company’s standard on the ranch property, where it has drilled more than 600 wells. Topographical and other considerations come into play in determining a pad’s well density. Regulations also generally keep companies from using directional drilling to cross into a new square-mile section, but Encana has been allowed to avoid that restriction on its ranch because it owns the entire ranch and its underlying minerals.
Encana has sought to make its drilling on the ranch a model of responsible gas development. It monitors water quality and works closely with state wildlife officials to protect raptors, greater sage-grouse, big game and other wildlife through measures such as seasonal limits on operations in certain areas. It uses pipelines to pump fluids to hydraulically fracture pads from remote, centralized locations, greatly reducing the truck traffic that would be required to frack onsite.
“That also from a disturbance standpoint improves wildlife situations,” Riggs said.
A pipeline system also transports condensate from pads, another traffic reducer that also eliminates the need for air-polluting tanks on pads.
As for reducing the number of pads, Merendino said it used to be that Encana thought it was accomplishing a lot when it was able to reach out directionally 2,500 feet from a pad to a downhole location. Now it has extended that reach to as much as 4,877 feet for the S-shaped wells it drills down, diagonally and then down into gas-bearing sandstone formations.
He said the company found it can reach out directionally a maximum of about 52 degrees. Any more than that, and well completion tools such as the tools used to perforate well casing in preparation for fracking can get hung up in a well’s curves.
Technological advances in areas such as drilling muds, bits and motors all have helped increase what companies such as Encana can achieve through directional drilling, Merendino said. Anticollision software can prevent wells from being drilled into one another; electromagnetic tools can detect if a bit is approaching the metal casing of another well. Merendino said “60 to 90 feet of electronics behind a drill bit” send signals back to the surface saying where the bit is at all times. All of that helps in assuring drillers hit a 30-by-50-foot target that on Encana’s ranch can be 7,000 to 9,000 feet underground.
Safety on the site
But directional drilling advances are only part of the story of how so many wells are now being drilled from a single pad. The ability to conduct simultaneous operations ensures that even while drilling continues, wells can be put into production to allow Encana to begin seeing a return on its considerable investment on a pad. It can be drilling one well on a pad, perforating another, fracturing a third, and flowing back fracking fluids from a fourth, while producing gas from other wells on the pad.
But for all that to occur safely, Encana had to address the increased safety risks that come with so many industrial activities occurring in close proximity where natural gas is present under high pressure.
Its solutions include measures such as covering producing wells with cages to protect them from possible impacts, separating the drilling rig from completion activities with a blast shield, and designing rig steps that face away from the completion area rather than toward it, so workers head in a safer direction in an emergency. All workers on a simultaneous-operation site check in through a security person, making a head count available if needed.
Another safety measure is using secure detonators for the perforation tools, so blasting caps can’t be inadvertently set off by radio transmissions, a concern that workers otherwise must address through restrictions on radio-based communications on site. The secure detonators cost about $10,000 more per well but are “a key part of our risk mitigation,” Merendino said.
As Encana has developed and refined its directional drilling and simultaneous operations, it has reduced the average drilling time per well from 26 days to sometimes seven or less, not just reaching but exceeding what Merendino previously thought was the technical limit for the minimum time required.
“Without our engineers designing it and getting it to this point, it would have never happened,” he said.
Such efficiencies in Encana’s local operations are crucial to making a profit when gas prices are low. Operating a rig costs Encana about $2,000 an hour. As Merendino stands beside a rig running on its ranch property, he points out its use of drilling pipes that are 45 feet long, rather than the traditional 30 feet, a change that means less time is spent adding pipe lengths, and drilling friction is reduced due to fewer pipe connections.
“That’s how we got to seven days (drilling a well), is those things, all the little things,” he said. “Now we’re down to hours. Now we’re looking to the next hour to cut.”
That’s not to mention the next increase in wells on one pad.
“Right now we have a 60-well pad planned,” he said.
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