It’s not an entire offshore rig, but it’s close. Rig 574 and four other rigs like it contracted to Williams Production Company have an interesting family tree. The substructures and masts on these rigs are based on the Nabors Offshore Super Sundowner designs which are purpose built to drill multiple wells. The Super Sundowner rig designs have been proven successful on numerous offshore multiwell platforms, worldwide. These rigs are usually installed on crowded offshore platforms with fixed production equipment.
The idea was a joint collaboration between Nabors and Williams Production Company. The rig was specifically designed to provide increased operational efficiency with the ability to drill and complete more wells in a shorter time frame.
The compact arrangement of the Super Sundowner rigs enables Williams to minimize the required footprint for the rig and they can drill and complete multiple wells on a single location which reduces the overall cost and environmental impact. Rig 574 provides significant cost and time savings compared to a typical drilling rig.
While it is already common practice to skid some conventional land rigs, this requires all the tubulars to be laid down prior to skidding. A typical rig move takes 20 hours and is limited to four to five wells in a straight line. The Super Sundowner design can move between wells with full setback in 3 to 4 hours.
The rig design has been optimized for simultaneous operations (SIMOPS) with the footprint of the drill floor minimized to cover the least number of wells as practically possible. This provides Williams with the ability to access and complete more wells. Optimizing the rig design for SIMOPS while having the ability to access and complete as many wells as possible resulted in the rig floor width being just 20 ft (6 m) across. In order to achieve this, the drawworks was mounted above the driller’s cabin.
The rig is currently configured to drill 22 wells on one location (two rows of 11 wells). The drill floor and mast design allows for the V-door to be located on two sides of the rig, which provides additional flexibility to configure the rig for different well site locations.
The drawworks is rated at 1,000 hp and the mast is rated at 600,000 lb static hook load. The rig is powered with three Caterpillar 3512C engines rated at 1,476 hp each. It is also equipped with two 1,600-hp mud pumps and a 275-ton top drive. Typical well depth is approximately 8,000 ft (2,439 m).
During rig-up, once the mast base section is in place, the remaining sections of the mast are hoisted and positioned horizontally, then swing into the vertical position and are scoped up. The upper section of the mast is installed complete with the traveling block. This unique design does not require additional space on location to lay over the mast as typically required for cantilever type masts. The remote operated catwalk pipe handling system provides safe and efficient handling of drill pipe, collars and casing from the pipe racks to the drill floor.
Rig 574 is currently drilling the third of 10 wells on a pad in the Piceance Basin. The rig will then be moved to another multiwell pad location in the Piceance Basin of Colorado.
Nabors says Rig 574 has performed very well since it began operating and claims that it has drilled with fewer problems and less downtime when compared to other rigs.
None of this necessarily portends the arrival of a drillship in Midland, but it is yet another example of how nimble thinking continues to change the landscape of drilling