New ‘walking’ rigs use a box-on-box design to operate on multiwell pads in sensitive, space-restricted areas. (See video of rig)
Drilling customers today are looking for the latest technology with compact but powerful equipment. They want faster moving features, enhanced safety elements, better power distribution, and greater control of torque and rate of penetration. These features allow operators to drill more efficiently and move more rapidly. Nabors Drilling USA (NDUSA) is meeting these drilling demands with a series of programmable AC electric (PACE) rigs.
The original PACE Academy rig debuted in 2005. Built by Nabors Canada, it is a 1,000-hp AC electric rig with programmable logic control. NDUSA unveiled its M-Series PACE rig two years later. These 1,000-hp rigs move in record time, averaging complete relocation in less than four days. In addition, these rigs have set numerous field drilling records in the growing shale plays. In 2007, the company successfully adapted multiwell offshore platform designs — Super Sundowner (SSD) — for land operations. The SSD compact arrangement minimizes the rig footprint in areas where location size is limited, such as the Rocky Mountains. The SSD rigs have realized significant increases in per-well productivity and are built to skid when drilling on a pad.
To address the importance of US shale gas, NDUSA recently reinvented its PACE model, which operates on multiwell pads in shale plays in the northern part of the US. The B-Series is a custom-designed box-on-box 1,500-hp rig specifically built for use in such plays, particularly North Dakota’s Bakken Shale.
Numerous rig designs and variations of the PACE format were evaluated, including self-elevating hydraulically raised masts and substructures. When considering the extreme weather conditions and winterization required for working in the northern regions of the country, it was decided that a box-on-box type rig was the preferred option. Several improvements were made to the standard box-on-box design to make the rig move faster from pad to pad.
Approximately two-thirds of the way through the construction of the inaugural rigs — B-01 and B-02 — the customer requested that NDUSA look at options to change the rig design to accommodate multiwell pads while carrying out simultaneous operations. The final well configuration selected by the customer required NDUSA to turn the substructure and mast 90 degrees, install a walking system, change the electrical grasshopper to a telescoping drag chain, and relocate the solids control equipment to optimize the design of the flowline.
Unique components of the B-Series
B-Series rigs are each equipped with a Columbia Walking System. Various NDUSA subsidiaries have been working with Columbia on the development of land rig moving systems since 1976. Moving technology has evolved from the pioneering rigs in Alaska to pad drilling in the Rocky Mountains and now to a new walking fleet using PACE technology.
B-Series rigs boast a variety of other features, including a Canrig TM80. This fully automated floor wrench is programmable logic controlled (PLC). Remote-control capability allows the unit to be activated from the driller’s console or from various rig floor locations. Pipe range is 23/8-in. to 8½-in. The maximum torque makeup is 60,000 ft/lb, and the maximum torque breakout is 80,000 ft/lb.
The rig also is equipped with a Canrig PowerCAT automated catwalk. It is designed to individually index racked drill collars, drillpipe, and casing into a center carrier where they can be lifted to the drill floor. It can safely raise subs, casing, logging tools, or utility baskets. The PowerCAT eliminates the need for pickup and lay down services when running casing. With its remote-controlled capability, the unit can be operated from the drill floor or from ground level.
A Canrig 1250AC, 500-ton top drive system is standard equipment on B-Series rigs. It is powered by a single 1,150-hp AC motor with a continuous torque rating of more than 51,400 ft/lb at 118 rpm. B-Rigs are equipped with a driller’s cabin featuring an ergonomic chair and integrated joystick control utilizing PLC technology. Touch-screen controls provide state-of-the-art monitoring and control of rig equipment and drilling parameters.
B-Rigs are powered by three Caterpillar 3512C engines rated at 1,476 hp, each driving one Kato 1365 KW generator for a total of 4,428 hp. A single house uses the Canrig Rig Control and Power System, 600-Volt AC power generation, variable frequency drive, and Smart MCCs. A 1,500-hp AC drawworks is available on the rig. It is powered by two 1,150-hp AC motors featuring regenerative AC braking and autodrill functionality.
The mast is 147 ft (45 m) high and is manufactured to API-4F specifications. The maximum static hook load capacity is 800,000 lb on 12 lines. Two 1,600-hp mud pumps control the flow of drilling fluids. Each is powered by one 1,500-hp AC motor and equipped with hydraulic liner retention and pump rod systems. The two-tank mud system has a capacity of approximately 1,000 bbl and four 6-in. by 8-in. centrifugal pumps powered with 75-hp motors. Solids control is handled by two M-I Swaco Mongoose PT dual motion adjustable shakers. One Brandt vacuum degasser, desander, and desilter is standard equipment on the rig.
The seven-station PLC-operated accumulator unit is equipped with one electric triplex and two air-operated pumps and is manufactured in accordance with API 16D. A remote panel is mounted on the drill floor. Additional equipment includes a dedicated man-rider winch, two hydraulic winches, camera system/intercom system, and a rotating mousehole.