Typically, in a high-pressure, high-temperature (HPHT) well, operators incorporate heavy workover and drilling fluids to provide a barrier to control the pressure. Often, the end result is formation damage, loss of un-recoverable fluids and appreciable increases in workover and completion costs. To help alleviate this and other problems in challenging environments, the use of snubbing units has come into vogue as a viable solution to the obstacles and resulting problems associated with drilling, workover and completion operations in an HPHT environment. The technology has evolved to the point that it can efficiently perform any function required of a conventional drilling rig. Recent experiences in the Haynesville and other un-conventional shale gas plays onshore the US have demonstrated the advantages of snubbing units in a variety of applications, including those involving hostile HPHT environments.
This paper discusses the evolution, design and application of snubbing units for HPHT applications with particular emphasis on the pre-well planning involved. To illustrate the operational, economic and environmental advantages of snubbing technology compared to coiled tubing and other more conventional approaches, the authors will present operational data from a recent HPHT well, along with a discussion on the ideal scenarios where snubbing technology should be considered.
Designed to provide insight for both operators and service companies, the paper will share experiences and lessons learned to demonstrate the effectiveness of snubbing units in an HPHT wellbore.