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Technical University of Crete
Technical University of Crete
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| URI: | http://purl.tuc.gr/dl/dias/FAE5DA49-236B-4107-8F3E-BF7BD0692F49 | ||
| Year | 2009 | ||
| Type of Item | Conference Full Paper | ||
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| Bibliographic Citation | V.C. Kelessidis, " Need for better knowledge of in-situ unconfined compressive strength of rock (UCS) to improve rock drillability prediction," presented at 3rd International AMIREG Conference, Athens, Greece, 2009. | ||
| Appears in Collections |
Rock - drill bit interaction while drilling hasbeen modeled for many years but a completeunderstanding of the phenomena occurring hasyet to materialize. Successful models will allowthe prediction of rate of penetration in a givenenvironment and optimal selection of drill bitand drilling parameters thus minimizing explorationcosts. In most rock-drilling models thevalue of the unconfined compressive strength ofthe rock (UCS), one of the most important engineeringproperties of rocks, is used in the predictiveequations, within the concept of specificenergy, and the value of UCS is the percentageof the value of the stress applied on the drillingbit in order for the bit to advance. While the exactpercentage depends on the model used and itis not known with certainty, good knowledge ofUCS is never-the-less required before any decentprediction can be made on rate of penetration.Determination of UCS, normally done viadestructive testing, requires not only availabilityof sound core samples, but also performance ofexpensive testing and significant time for thetest, which many times is not available for routinedrillability predictions. Hence, a multitudeof methods and techniques has been proposed toestimate UCS from various indirect and/or notdestructivemeasurements, or combination ofmeasurements using neural networks, such aspoint load index, block punch index, unitweight, apparent porosity, water absorption byweight, P-wave velocity and Schmidt hardness.The many proposed approaches are critically reviewedand the results are compared and whatbecomes apparent is that after many years, notonly in mining but also in oil-well drilling, accurateindirect determination of UCS is still anelusive property. Various approaches are suggestedto enable better indirect determination ofUCS.
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