Comparison of Specific Energy Between Drilling With High Power Lasers and Other Drilling Methods

Abstract

Abstract Specific energy is often used as a measure of a drilling methods performance. Specific energy as defined in this paper is the amount of energy required to remove a given volume of rock (energy/volume). This is a normalization method used to compare the efficiency of one rock destruction technique to another. This paper compares specific energy between drilling with high power lasers and other drilling techniques such as traditional rotary and other novel methods such as water jets. Specific energy calculations made from laboratory measurements taken using four high power lasers, are compared to specific energy calculations reported in the literature. Although many other rock types were lased in this research, all comparisons are made on Berea sandstone, as it is the most commonly tested rock. A discussion of how the sample type, shape of test sample, and experimental conditions effect the calculations and results is included. It was found that there could be, and probably is, confusion caused by the way that specific energy is defined and calculated. The definition of specific energy, as used in this paper, is often compared to specific kerfing energy that is defined as power per kerf depth multiplied by the speed the cutting mechanism is moving across a rock surface. It was also found, by reviewing published work, that there have been many comparisons made in the literature that did not take into consideration such things as rock type and shape. Experimental conditions such as the atmosphere where the "cutting" tool and the rock interact have not been accounted for when many of the previous comparisons were made. Sample size in relationship to power density has also not been accounted for.