The next generation of land-based rigs for the frozen North?
Remote Arctic onshore exploration can be very costly, frequently exceeding the cost of a deepwater Gulf of Mexico well. The short drilling season, combined with logistics complexities, typically limits each exploration rig to just one or two wells.
ConocoPhillips has significant Arctic onshore exploration acreage in Alaska, Canada and Russia. A number of exploration prospects are 50 to 200 miles from existing infrastructure. While ice roads and conventional wheeled vehicles can be used to reach exploration sites close to infrastructure, most remote exploration sites, or those greater than 50 miles from infrastructure, are accessed using snow roads and low ground pressure vehicles. The drilling operation requires significant loads to transport rig and associated equipment.
The Arctic drilling seasons are very limited with first tundra access typically commencing in mid- to late-December and most drilling activities normally complete by May 1. This means approximately 130 drillings days are available. Mobilization of the drilling rig often does not start until early January. Mobilization and demobilization typically takes 30 days each with the current rigs. Drilling time is approximately 30 days, so the time for one well is 90 days, which precludes drilling a second well. In Russia, typically one winter season is required for mobilization and erection. Drilling will continue through the spring, summer and fall, and the rig will be demobilized the following winter.
What ConocoPhillips requires is a rig design which could reduce mobilization and demobilization cost and time. Reducing the final hole size by drilling a slimhole well would allow the use of smaller rigs. These rigs allow significantly reduced number of loads, simple rig up, no stacking of components, flexibility to use the rig in other operating areas, drop and plug/play, arctic tundra conditions transportable, and arctic environment adaptable.
After evaluating a number of rigs, the Hybrid Coil Tubing Drilling (CTD) rig (used for shallow drilling in Canada) has been identified as the best vehicle to develop the current concept for Arctic Rigs. Current hybrid rigs used are capable of drilling to depths of 3,000 feet. In order to reach depths of 10,000 feet, the rig design had to be revised with stronger masts and larger capacity pumps.
Technically, there are no barriers to using a Hybrid CTD rig for exploration drilling and geological / geophysical objectives can be met. Using existing technology wells could be drilled to 10,000 feet. The rig design and operation have inherent health, safety and environmental advantages. For example, manual labor, particularly pipe handling, is reduced and this should reduce the personal injury rate. Environmentally, the CTD units have less impact than conventional rigs.
A Hybrid CTD rig can potentially reduce the well costs by 50 percent. The reduced time to mobilize, drill and demobilize a CTD rig allows multiple wells to be drilled in one season. This concept has been proven through field trials in Canada and is being investigated for application in other ConocoPhillips-operated Arctic locations.