Estimating Rock Properties Using Sound Levels from Drilling
Figure 4: Definition of Functions Including One-to-one and Many-to-one Relations and Excluding One-to-many Relations
One-to-one (function) A
B Figure 6: Sample Flowchart Explaining the Computer Programme Input drill condition
X Y
Input hole locations
One-to-many (relation) (cannot be a function)
Many-to-one (function)
A B C
X A B
X Y Z
Input noise spectrum curve for all drill holes up to full drill depths
Compare observations with database
Generate 3D view Y Figure 5: Drill Conditions as Permutations of Various Drill Parameters
Drill bit 1 Drill bit 2
Drill machine 1 Drill machine 2
Drill machine
Drill machine n …………
Table 4: Relational Database Consisting of Compressive Strengths, Drill Conditions and Noise Spectrum Curves
Compressive Condition Condition Condition Condition
Strength of rock123M Comp1 Comp2 Comp3 Comp4 Comp5 CompN
Curve 1,1 Curve 1,2 Curve 1,3 Curve 1,M Curve 2,1 Curve 2,2 Curve 2,3 Curve 2,M Curve 3,1 Curve 2,2 Curve 3,3 Curve 3,M Curve 4,1 Curve 3,2 Curve 4,3 Curve 4,M Curve 5,1 Curve 4,2 Curve 5,3 Curve 5,M Curve N,1 Curve N,2 Curve N,3 Curve N,M
………… Drill bit m
Condition 1 Condition 2
………… Condition m
air pressure have a significant effect on the sound level produced by a pneumatic drill at the measurement location, i.e. near the drill bit. An increase in sound level in the order of 1.0–1.7 dB near the drill bit can result from an increase in air pressure by 2.0 kg/cm2 at 160 N thrust, with an increase in compressive strength and decrease in abrasivity of rocks from shale to gabbros. Similarly, an increase in thrust by 200 N at a constant air pressure of 5.0 kg/cm2 can result in an increase in sound level near the drill bit by 0.9–1.9 dB, with an increase in compressive strength and decrease in abrasivity of rocks from shale to gabbros.
The increase in sound level near the drill bit with increase in compressive strength and decrease in abrasivity of rock from shale to gabbros is in the order of 1.0–2.0 dB at constant thrust and air pressure values. It needs to be emphasised that to maintain a constant penetration rate in the rocks, both the thrust and air pressure need to be increased with a corresponding increase in compressive strength and decrease in abrasivity of rocks. Therefore, increased compressive strength and lower abrasivity of rocks will require higher air pressure and greater thrust to be applied to achieve an optimum penetration rate and will therefore result in a higher sound level near the drill bit.
view of the field, over the whole drilling area and up to the complete drilling depth, will be shown.
A sample flowchart of the computer program is shown in Figure 6. The 3D view created may contain several layers of rocks within the specific depth drilled. Attempts will be made to make the program increasingly user-friendly by adding features such as negotiation of 3D view, splitting of distinct rock layers, inspection of section view across any plane, etc.
Conclusions
An increase in the level of thrust causes an increase in the sound level at higher midband frequencies in the noise spectrum. Both thrust and
1. 2.
Vardhan H, Adhikari GR, Govinda RM, Estimating rock properties using sound levels produced during drilling, Int J Rock Mech Min Sci, 2009;46(3):604–12.
Roy S, Adhikari GR, Worker noise exposures from diesel and
This study shows that the estimation of rock properties using sound levels produced during drilling, both experimentally and analytically, can be a very useful technique in the drilling of deep oil wells as well as exploratory holes. In addition to estimating rock properties, it can be used to select suitable drill tools for enhanced output and better monitoring of drilling by the crew. Furthermore, drilling parameters such as thrust, RPM, etc. can be controlled for optimum penetration rate and longer life of the drilling tools. n
Acknowledgements
The principal author sincerely thanks the Ministry of Science and Technology in the Government of India for the ‘Young Scientist Award’ provided under the Science and Engineering Research Council. All the necessary equipment and fabrication was carried out from this award.
electric surface coal mining machinery, Noise Control Eng J, 2007;55(5):434–37.
3.
Vardhan H, Murthy ChSN, An experimental investigation of jack hammer drill noise with special emphasis on drilling in
rocks of different compressive strengths, Noise Control Eng J, 2007;55(3):282–93.
4. Brown ET, Rock Characterization Testing and Monitoring. I.S.R.M. Suggested Methods, Elservier, 1981.
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EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 2
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