National Institute of Advanced Industrial Science and Technology (AIST) This page is a page of the former research institute. We stopped updating on March 31.2001.
E-mail to webmaster (Japanese) E-mail to webmaster (English)
National Institute for Resources and Environment HomePage

NIRE Annual Report
Back Contents Next
1996

Measurement of Downhole Conditions while Drilling

Mining System Engineering Division
Mining and Geotechnology Department
Objectives
To investigate methods for the estimation of downhole conditions such as the rock strength and the tooth wear of bits while drilling, drilling tests were carried out using roller cone bits with different degree of tooth wear. Tuff, sandstone and two types of andesite were drilled in the tests. The information which is only related to the rock strength and the tooth wear was investigated based on the test results.
Results
We have obtained the relation between the bit weight per unit length of bit diameter (F/d) and the penetration per revolution (u/N) for each bit in each rock drilling, where F is the bit weight, d the bit diameter, u the penetration rate, and N the rotary speed. In addition, we have obtained the relation between the rotary energy per revolution divided by the cross-sectional area of the bit (8T/d2) and u/N, where T is the torque. On the basis of these relations obtained, the information which shows the rock strength and the tooth wear was investigated.
Figure 1. shows the relation between the effective axial energy per revolution divided by the bit diameter (Feu/Nd) and the square of the effective rotary energy per revolution divided by the cross-sectional area of the bit ((8T/d2)2), where Fe and Te are the effective weight and the effective torque respectively. T0, T4 and T7 in the figure exhibit the new, half worn and 7/8 worn bits, respectively. From the figure, it is obvious that the relation between Feu/Nd and (8T/d2)2 is closely linked to the rock strength.
Figure 2. shows the relation between the reduction ratio of the tooth height (TW) and the square of the dimensionless effective torque (Ted2), where Ted is equal to 8Te/Fed. The same trends mentioned above were obtained for Ted instead of Ted2. It is clear that we can estimate the tooth wear quantitatively from the dimensionless effective torque (Ted), except for tuff and sandstone for T0 bit.


Selected Publication
1),2) Study on analytical technique for downhole information (2nd and 3rd Reports), Submitted for J. of MMIJ.

Back Contents Next










National Institute for Resources and Environment