Investigating the Role of Different Rock Properties in Laser Perforation

Abstract High-power laser technology emerges as a feasible alternative to conventional perforation techniques in oil and gas wells, offering precise, clean, and debris-free perforations. The outcome of laser perforation is influenced by downhole conditions, rock properties, as well as laser properties. The objective of this paper is to evaluate how different rock properties affect laser-rock interaction and ultimately govern the perforation process. This review provides a rigorous assessment of the impact of different rock properties and downhole conditions on the laser perforation process, leveraging an extensive range of laboratory tests, computational simulations, and observational data. The investigation focuses on properties such as in-situ stresses, rock heterogeneity, and rock hardness, all of which play a pivotal role in the laser perforation process. Lab experiments and simulation models revealed that high-power laser drilling or perforation is a stress independent process. Changes in the confining stress magnitude or ratio did not influence the rate at which the material was penetrated. This was confirmed by the uniform temperature distribution in the tested sample among the different sensitivity cases with varying confining stress values and ratios. Heterogeneity, represented by variation in permeability and porosity, mineralogy, and presence of laminations, influenced the rate of laser perforation growth. Shale lamination had a faster thermal propagation due to the higher thermal conductivity of shale compared to the tested limestone samples. As for rock hardness, extremely hard rocks such as granite and basalt were laser perforated. Testing showed that they exhibited a faster ROP than softer and more porous rocks due to the efficiency of heat conductivity across dense and less porous rocks. Overall, high-power lasers can provide more sustainable alternatives compared to the conventional means for different oil and gas operations such as drilling, perforation, and descaling, while tackling different technical challenges associated with the existing methods. Another distinction of high-power lasers lies in performing all of these applications with the same laser engine and system in the field with a more significantly reduced footprint than conventional practices.