In gas and oil well completion, perforation channels must be made through the steel casing wall and cement and into the rock formation in the production zone to allow formation fluid to enter the well. This paper will present study results on using a pulsed CO2 laser to drill the perforation channels through reservoir rocks. With fiber optic cable delivery capability, a CO2 laser beam has the potential to be delivered to deep oil production zones. Effects of laser pulse parameters, beam properties, and assistant gas purging on the perforating efficiency and rock permeability will be reported. Unlike the conventional explosive charge perforation that often causes great reduction of rock permeability, laser perforation would enhance the rock permeability, therefore increasing the oil or gas production rate of the well.

Laser on time, laser relaxation time between laser bursts and sample rotary speed also affect the perforation. A laser burst is the sum of the multiple pulses over the period of laser on time. Pulsed CO2 laser with fiber optic cable delivery is a strong candidate for laser perforation application for oil and natural gas wells. Preliminary test shows that CO2 laser can perforate 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 566% 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.

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