Photonic-Hydraulic Fracturing Hybrid Approach Minimizing Breaking Pressure

Abstract

AbstractThis paper presents a novel approach to reducing the hydraulic breakdown pressure utilizing near-infrared continuous-wave high-power lasers (HPL). The thermo-mechanical and thermo-chemical processes induced by the HPL illumination of the rock above a particular threshold can lead to lower formation strengths, significantly reducing the formation's breaking pressure. This HPL application could improve energy efficiency and reduce the risk of hydraulic fracturing operations.The rock absorbs a portion of the HPL's energy as thermal energy, causing a localized temperature surge, resulting in various physical and chemical changes. The former arises from sharp and fast-developing thermal gradients that generate micro and macro cracks in the formation. The thermal-chemical transformations of the rock include mineral dehydration, dissociation, decomposition, clay collapse, and retorting of organic matter. This electromagnetic-based mechanism has been assessed and proven to effectively reduce breaking pressure for all types of rocks. The process is independent of the rock's stress state and composition. It was evaluated on carbonate, shale, and sandstone formations in the lab. The experimental results guided the development of the first high-power laser field system. The system design incorporates an HPL generator and the optical assembly needed to deliver and manipulate the HPL in the subsurface. The optical assembly includes a subsurface optical tool whose primary function is to control the size, shape, and propagation direction of the HPL beam.The HPL technique was tested on various rock types. Pre- and post-exposure analyses were conducted to evaluate its efficacy. These studies included uniaxial stress tests, unconfined ultrasound velocity measurements, permeability, porosity, composition, grain shapes, contact, and cementation. This investigation provided valuable information about the physical dynamics of the process. The results show that this HPL method could reduce breaking pressure in all rock types. The technique and HPL perforation could create targeted weak spots in the near-wellbore formation, improving the precision of hydraulic fracturing while decreasing its energy intensity, cost, and environmental impact.