A NEW APPROACH FOR DETERMINING IN-SITU ROCK STRENGTH WHILE DRILLING

A new method is developed for determining rock strength while drilling with a tri-cone roller bit. The technique employs the well-known ''dr ill-off'' test, using commonly measured drilling data, and does not re quire knowledge of drill bit parameters. The method was evaluated with drill-off test darn collected from the Gas Research Institute's SFE ( staged field experiment) well no. 4 and compared with calculated in-si tu compressive rock strengths provided by Hareland (1992). The results indicate that the proposed approach produces reasonable results and i s easily implemented.