The uses for coiled tubing (CT) have expanded over the last two decades to encompass more broad based applications than ever before. This coincides with advancements in drilling technology that have extended these applications to deeper depths, in more hostile environments, the drilling of more complex well profiles, and CT drilling at shallower depths. CT technology has had to keep pace in order to perform effectively in workover operations, and in drilling operations such as sidetracking, wellbore extensions and grass roots drilling, in these more hostile environments.
Technology has been adapted to CT as it has been required. However, in many instances, these adaptations have fallen short of achieving optimal performance. The use of Turbodrills is a prime example of this unrealized potential. Using Turbodrills in CT applications provides many benefits, but, historically, a standard Turbodrill, configured for drilling, has been taken off the shelf for use on CT. This method can and has been successful. However, by analyzing the specific applications encountered with CT, Turbodrill design enhancements can be made to better match the Turbodrill to CT applications. One major advancement in this area, is the creation of a Turbodrill that can provide more power with a shorter tool. This paper will detail the design enhancements made to the Turbodrill to accomplish the goals of establishing a shorter tool, with more power, to address current and future applications.
CT technology has progressed dramatically over the last two decades to include a much broader range of applications than ever before. These applications range from CT's original intent, for workover and remedial operations, albeit with much greater capabilities today than when originally introduced, to wellbore extensions, sidetracking, drilling grass root wells, completions, and pipelines. It was during the 1980's that CT technology made great advancements. Materials science advancements, coupled with better manufacturing and quality processes, allowed the CT itself to become more durable, with the added ability to be manufactured in larger diameters. These advancements enabled CT to reliably be deployed in deeper, more complex applications.1
In the mid 1980's, efforts on reducing the costs associated with extracting hydrocarbons became more closely scrutinized, as commodity prices plummeted to historical lows. The evolving reliability of CT exemplified a low cost alternative, versus a standard workover or drilling rig. At a fraction of the traditional cost, remedial operations could be undertaken to improve recovery rates, with the added benefit that operations could be performed without killing the well. Identifying the shortcomings of this new approach then proved quite simple: the functionality and flexibility of tools deployed on CT were surpassed by the CT itself and focused efforts were required to design downhole tools specifically for CT.2
During the 1990's, other technologies, such as 3D seismic, identified numerous bypassed reserves around existing wellbores, left behind due to sweep inefficiencies, smaller reservoirs behind pipe, and deeper reservoirs below previously set casing shoes. The identification of these vast reserves, coupled with technological advances in drilling, and the existing production infrastructure, made it economically feasible to target many of these hydrocarbons. Once again, advances in drilling with CT provided a feasible backdrop to tap these reserves. Numerous benefits of the use of CT could be realized in these applications; smaller rig footprints, smaller volumes of drilling fluids to be handled, smaller volumes of drill cuttings requiring handling, faster rig up time, faster tripping time, reduced noise levels, fewer personnel requirements, reduced environmental impact, safer operations and, ultimately, drilling underbalanced.3