Nonretrievable Rotating-Liner Drilling System Deployed Successfully
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 124854, ’Non-Retrievable Rotating Liner Drilling System Successfully Deployed To Overcome Challenging Highly Stressed Rubble Zone in a GOM Ultra-Deepwater Sub-Salt Application,’ by Jim Kunning and Yafei Wu, Anadarko Petroleum, and Ian J. Thomson, Larry Marshall, Derrick Daigle, SPE, Henry J. Mata, SPE, Robert Pena, Matt Hensgens, and Billy Eppley, Baker Hughes, originally prepared for the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, 4-7 October.

The full-length paper presents some of the geomechanical drilling hazards encountered in an ultradeepwater well in the Gulf of Mexico (GOM) Walker Ridge area, the effect of those hazards on the drilling operation, and the outcome of deployment of a nonretrievable rotating-liner drilling system. This drilling system, in conjunction with a specially designed liner drilling polycrystalline-diamond-compact (PDC) bit, enabled operators to drill through and isolate a challenging highly stressed rubble zone found adjacent to a problematic tar/bitumen layer. 

Introduction

It is well known in the industry that, because of seismic acoustic-wave-velocity uncertainty across thick salt bodies and the high acoustic-wave-velocity contrast between salt and surrounding formations, the subsalt-environment characteristics and pressure regimes cannot be determined accurately by seismic models. As a consequence, unexpected events commonly are encountered, which include lost circulation, stuck pipe, highly stressed rocks, and tar zones below the salt body. Lost circulation and tar are among the most dreaded hazards in the subsalt drilling scenarios, mainly in exploration and appraisal wells, where only limited information about the area being drilled is available.

When these hazards are found, drilling time and cost increase significantly. In many cases, these lead to unplanned sidetracks, suspension of operations, or even abandonment of the well. Casing/liner drilling traditionally has been used to solve localized drilling challenges related to wellbore instability while drilling through depleted reservoirs. Recent oilfield advances, including improved tubulars, and pipe handling, have proved that nonretrievable rotating-liner drilling is a viable cost-cutting option to overcome some of these new deepwater subsalt challenges.

Nonretrievable Rotating-Liner Drilling System

Advances in connections, rig technology, liner equipment, and mud systems have allowed liner drilling to move forward as a solution to challenges of drilling wells today, where conventional drilling may not be the best option. In deep- and ultradeepwater subsalt wells, it is proving more difficult to get a liner to bottom as a result of the challenging formations being drilled.  The ability to wash, ream, or drill the liner string to depth always has been limited by the high circulating pressures that may be required to achieve such goals. Circulation rates have always been kept sufficiently low to avoid presetting the hanger or prereleasing the running tool during drilling operations. To overcome these issues, an improved design of a nonretrievable-liner drilling system that is easy to implement and practical in application was introduced.