Unit Drilling launches advanced-technology BOSS rig design

By Linda Hsieh, managing editor

Unit Drilling has put the first of its newly designed BOSS series, Rig 401, to work in the Texas Panhandle for Unit Petroleum. The 1,500-hp, AC-powered walking rig incorporates several features aimed at reducing the number of loads and increasing mobility, including a ram-raised box-on-box substructure. “What makes it unique is the top sub fits down over the lower sub for transportation,” John Cromling, Executive VP for Unit Drilling, explained. “It’s all hydraulically controlled – the raising, the pinning, etc. There’s not another substructure like this one.”

Excluding tubulars and camp facilities, the rig has just 32-34 loads. However, the design of the rig was underpinned not just by a desire to have fewer loads but to actually manage the loads better, Mr Cromling said. For example, the BOSS rigs have been designed so that rig-up can begin with any part of the rig. “You could begin with the mud pits. You could begin with the substructure. You could begin with the engines. It can rig-up no matter which load arrives first. That facilitates a faster rig-up,” he said.

Throughout the design process, significant focus was also placed on engineering each component and load to minimize the weight, height and width and to eliminate as many extra-large permit loads as possible. “When you keep every load under 12 ft wide, that adds to the overall efficiency of the rig,” he said. The rig-up does require crane assistance, although it’s minimal, Mr Cromling added. Overall, he said, he believes the BOSS rig can achieve a 15% quicker rig-up compared with other advanced-technology, fast-moving rigs and up to 40% quicker compared with conventional box-on-box rigs.

Another feature is the two 2,200-hp quintuplex mud pumps, which Unit Drilling opted over triplex versions for higher pump output. “This means we can truly drill most of the horizontal wells with one mud pump, with the second as a standby,” Mr Cromling said. The company also chose to outfit the rigs with diesel engines with bifuel capability, rather than natural gas engines. “We felt like going all gas would limit us in places where field gas isn’t available. Another environmental feature is that the skids underneath the engines and pumps are totally enclosed and can trap any fluid that might spill. Any fluid is contained within the system to be pumped away to a disposal area,” he commented.

The first BOSS rig began operating in the Granite Wash in Texas’ Hemphill County at the end of March, drilling horizontal wells with 14,500-ft to 16,000-ft MDs. Since Unit Petroleum is a sister company, Mr Cromling said, it has provided greater flexibility to work out problems throughout the assembly and testing process at the company’s Oklahoma City yard. “Things that typically happen with a new design or any new rig – we were able to address them here in the yard before we ever sent the rig out.”

The company is now in the process of building four more BOSS rigs, and all but the last one has two-year contracts in place. The first of these four will be completed by mid-June, when it will mobilize to North Dakota. The second rig will go to work in the Niobrara in Colorado, and the following unit will operate in North Dakota. “Right now, the goal is to have one rig out every two months,” Mr Cromling said, adding that he hopes to build between eight to 12 new BOSS rigs in the coming year.

In the meantime, the company is investing heavily in training. Unit sees this as a critical aspect to the success of the new rigs, especially because they represent the first advanced-technology units in Unit’s 119-rig fleet. “For Rig 401, we had the crews do a mix of hands-on and classroom training for about 60 days, and we expect to continue that for all of these rigs as they go out,” Mr Cromling said. “We see a significant focus from the operators on training, and we’re prepared to invest the time necessary to make sure our people are well prepared for these new technologies.”