Cyclical hydraulic pressure pulses reduce breakdown pressure and initiate staged fracture growth in PMMA

• Published in: Geomechanics and geophysics for geo-energy and geo-resources. Vol. 10; no. 1; pp. 1 - 20
• Main Authors: Mouli-Castillo, Julien, Kendrick, Jackie E., Lightbody, Alexander, Fraser-Harris, Andrew, Edlmann, Katriona, McDermott, Christopher Ian, Shipton, Zoe Kai
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2024; Springer Nature B.V; Springer
• Subjects: Breakdown; Breakdown pressure; Cables; Crack initiation; Crack propagation; Earthquake damage; Earthquakes; Energy; Engineering; Environmental Science and Engineering; Fluid injection; Foundations; Fracture mechanics; Geo-energy; Geoengineering; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Geothermal; Hydraulic fracturing; Hydraulic pressure; Hydraulics; Injection; Mathematical models; Numerical models; Optical fibres; Original Article; Permeability; Polymethyl methacrylate; Power consumption; Pressure; Pressure pulses; Pulsed pumping; Sedimentary rocks; Seismic activity; Shale; System effectiveness; Temperature effects; Pulsed pumping; Geo-energy; Geothermal; Breakdown pressure
• DOI: 10.1007/s40948-024-00739-z
• ISSN: 2363-8419

Using unique experimental equipment on large bench-scale samples of Polymethylmethacrylate, used in the literature as an analogue for shale, we investigate the potential benefits of applying cyclical hydraulic pressure pulses to enhance the near-well connectivity through hydraulic fracturing treatment. Under unconfined and confined stresses, equivalent to a depth of up to 530 m, we use dynamic high-resolution strain measurements from fibre optic cables, complemented by optical recordings of fracture development, and investigate the impact of cyclical hydraulic pressure pulses on the number of cycles to failure in Polymethylmethacrylate at different temperatures. Our results indicate that a significant reduction in breakdown pressure can be achieved. This suggests that cyclic pressure pulses could require lower power consumption, as well as reduced fluid injection volumes and injection rates during stimulation, which could minimise the occurrence of the largest induced seismic events. Our results show that fractures develop in stages under repeated pressure cycles. This suggests that Cyclic Fluid Pressurization Systems could be effective in managing damage build-up and increasing permeability. This is achieved by forming numerous small fractures and reducing the size and occurrence of large fracturing events that produce large seismic events. Our results offer new insight into cyclical hydraulic fracturing treatments and provide a unique data set for benchmarking numerical models of fracture initiation and propagation. Article Highlights Cyclical Hydraulic Pressure Pulses (CHPP) can reduce the breakdown pressure required to fracture PMMA. CHPP have potential to reduce peak power consumption to achieve failure and increase permeability of a rock, with positive implications for geothermal applications. CHPP induced multi-staged fracture propagation, implying an enhanced ability to control damage initiation by hydraulic fracturing.