Abstract

In offshore areas of Canada: Nova Scotia, Newfoundland, and the Beaufort Sea, a total of 60 turbodrilling tests were run with 5 different classifications of bits on both 2 and 3 section turbines. The economics of each of these runs were evaluated in terms of offset rock bit on rotary data. It was found that 2 section turbines better matched the rig capabilities and shales in these areas. Several drill bit design changes and standards were implemented to improve bit life under the turbodrilling system. In areas where sufficient drilling tests were conducted in a given size hole with a variety of bit styles, economic patterns became evident. Generally, step bits showed the best performance, PDC and impregnated bits higher in the hole and diamond step bits in deeper sections. Overall, the 60 turbodrilling tests were economical.

Introduction

For a long time, turbodrilling has been regarded as an exceptional practice needed to solve drilling problems or to avert potential problems. For instance, it was developed on a large scale in the USSR to compensate for the deficiency of drill pipe and rotate roller cone bits.

About 25 years ago, western countries began to develop this technology to compete with the already advanced techniques of conventional rotary drilling. Ie quickly appeared that only diamond bits. either natural or synthetic, depending upon the application, make turbodrilling economical.

After 15 years of development, both with the tool and the bits, turbodrilling had become an economical, even standard, drilling practice in the North Sea and the Middle East where daily rig costs are high. Since then, research and development in both elements of the system have made turbodrilling a common practice in major drilling areas where deep and expensive drilling are being encountered. A direct transfer of the technology from Europe to Canada was not expected because of differences in drilling conditions. The Canadian lithology is not yet well documented. Water base mud is the Canadian drilling fluid as opposed to oil base mud used in overseas turbodrilling. Rig capacity, most notably the pumps, are of very different configurations depending on the side of the Atlantic they are on. Still, the technology looked promosing for Canadian implementation with the very high daily operating costs seen on the East Coast and in the Beaufort Sea.

A few major operators decided to investigate the feasability of adapting turbodrilling for Canadian applications. They worked with several bit manufacturers and with turbine experts to develop an understanding (If the system for their applications.

THE TURBINE

For the last two years, major oil companies in Canada have been testing and evaluating the turbodrilling applications in the Beaufort Sea and on the East Coast of Canada. Although the major advantages of turbodrilling have always been faster penetration and a reduced number of trips, there are numerous advantages that can be gained in successful turbodrilling.

The low drill string RPH reduces wear in casing, BOP's, riser

String torque is lower and steadier, reducing the chances of twist off.

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