Novel Drilling System Offers Rotary Steerable System Performance with Real Time Survey in Top Hole Sections While Reducing Overall Costs
Authors: Neil P. , Gaines M. , Herrington D. 
Published: September 2013

The challenges involved in maintaining a truly vertical wellbore in the vertical section result in significant losses in drilling efficiency, raising the cost to reach the final target. The increasing complexity of modern drilling programs frequently require extended lateral and horizontal sections to be drilled to allow for production through multiple pay zones. As the reach of these wells is extended further each year, the importance of maintaining a truly straight and vertical top section becomes more critical, but modern solutions to this challenge are either inefficient or prohibitively expensive. A more financially viable solution must be provided for the drilling industry to continue the pursuit of hydrocarbons in these applications.

Ensuring that the vertical section of the well is as straight and true as possible is vital in today's drilling operations. This will reduce the frictional forces as much as possible, allowing the driller to more effectively provide Weight on the Bit (WOB) to penetrate the formation. Natural variations in the earth, such as tendencies in the formation caused by layers that are deposited at an angle to the surface or random deposits of hard rock, can push the bit off of its true vertical trajectory, which then require corrections to steer the bit and drill string back on a true vertical course. The curves or kinks created by correcting the drift of the bit create additional points of contact with the wellbore wall by increasing the tortuosity of the vertical section.

Unfortunately, the solutions to maintaining true verticality and a straight bore are limited. Controlled drilling is slow and limited in terms of performance, while bent housing motors can correct deviation, but result in increased tortuosity. Rotary Steerable Systems (RSS) offer excellent performance, but are expensive to run both in terms of daily cost and the increased risk of Lost in Hole (LIH) charges.

The industry has taken a new step in the evolution of this technology by creating a tool that combines the quality and speed of an RSS system with the economics of a bent housing motor solution. By focusing on simple mechanical and electrical design features, this tool has driven down the cost required to supply RSS performance while maintaining the same high standards. By combining the field proven design elements from a number of existing technologies such as motors and Measurements While Drilling and Logging While Drilling equipment, a robust and reliable system has been developed which not only provides drilling correction in vertical sections, but also provides the real time surveys that are required to keep the well on course. This system is fully autonomous providing an economical solution that will deliver a high quality vertical wellbore while reducing the cost per foot of the well.

A major independent oil company estimates they would increase adoption of RSS technology from 5% of their wells to 70% if a product could be offered with a 50% reduced cost. This paper will detail a new system that is being used to deliver the ground performance and economics to answer that call, and will provide performance data and analysis showing the value and advantages provided by this unique drilling system.