Experimental Analysis of Laser Drilling Impacts on Rock Properties

The petroleum industry welcomes new technologies that not only increase production rate effectively but also minimize the formation damage. The energy required to remove a unit volume of rock, namely the specific energy (SE), is a critical rock property data that can be used to determine both the technical and economic feasibility of laser oil and gas well drilling. When a laser beam is applied on a rock, it can remove the rock by thermal spallation, melting, or vaporization depending on the applied laser energy and the way the energy is applied. Our experiments showed the most efficient rock removal mechanism would be the one that require the minimum energy to remove a unit volume of rock. This paper will present study results on using a pulsed CO2 laser to drill through the given rock samples. Preliminary test shows that CO2 laser can drill the rock as efficiently as the other types of high power lasers and the permeability of the rock lased by pulsed CO2 laser beam increases up to 150% compared to non-lased rocks due to clay dehydration and microfractures induced by the high temperature gradient and phase transformation volume expansion generated in the rock while lasing.