As gas reserves at shallower depths are depleted and the decline rate of producing reservoirs accelerates, the search for economically viable reservoirs in North America now focuses on drilling to greater depths. Deeper drilling creates added challenges: harder / more abrasive rock, elevated temperatures, higher pressures and higher costs to drill and operate. These operations will narrow the margin for error and create opportunities to add significant value through the drilling and completion process. Therefore, it is imperative to evaluate all available technology in selecting the optimum drilling equipment through a more technically stringent economic model. Through this evaluation, applications in which turbodrilling can be economically beneficial will be evident.

Turbodrills have been used in the oil and gas industry since the 1920s, yet they remain relatively obscure. This paper examines the history of turbodrilling and describes a number of the harshest and most complex drilling environments in which turbodrills have been notably successful. Through a historical analysis of turbodrilling, the evolution of the technology, including the most recent technological advancements, is detailed. Finally, recent case histories in North America are evaluated for application and performance.

Introduction to Turbodrilling

Turbine power was introduced in the United States over a century ago, in 1873. The first patent, a single stage, impulse turbodrill, issued to C. Cross. In 1884, the turbodrill design was rethought and a second patent issued to M. Baker for a single stage, axial flow turbodrill. Over the next 40 years, few advancements were made to the technology of turbodrilling. Most design emphasis during this period was directed to the development of the rotary drilling rig, which, in 1901, was utilized to drill the Spindletop discovery well. This discovery proved to mark the beginning of the modern petroleum industry. It wasn't long until better, more efficient methods for drilling were considered essential. Turbodrill developments resumed in the US in 1922. In 1924, the multi-stage, axial flow turbodrill was patented by Scharpenburg. The Scharpenburg design wastested in Elk Hills, California in 1926, with mixed results. During the following 10 years, the design was improved with the addition of rubber radial bearings and the removal of specific internal seals with which it was originally equipped.1

At about the same time, 1923, Russian engineers began development work on a single stage turbodrill for oil and gas drilling applications. In 1924, the Russians developed the first geared turbodrill in conjunction with a single stage, axial flow design. These developments were motivated by an interest in modifying one of the main turbodrill characteristics: high rotational velocity (RPM). The hope was to increase the nominal drive shaft torque, while reducing drive shaft speed. The planned modification hoped to reduce turbodrill output RPM, then ranging between 2,000–3,000 RPM to 15–60 RPM at the drill bit. Since drill bit technology of the day was in its infancy, and the only drill bits available in Russia were roller cone bits, this entire development was an attempt to lower the output RPM to a range in which a roller cone bit could endur

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