Propagation of cryogenic thermal fractures from unconfined pmma boreholes
Cha M. Alqahtani N.B. Yin X. Wang L. Yao B. Kneafsey T.J. Miskimins J.L. Wu Y.-S.
September 2021MDPI
Energies
2021#14Issue 17
In cryogenic fracturing, a rock surface exposed to cryogenic fluids undergoes a large thermal gradient, and the resultant local tensile stress overcomes rock strength and initiates fractures. This study investigates the development of cracks generated from the cryogenic treatment of a borehole under no external confining stress on specimens. The experiments were performed on transparent PMMA specimens to observe fracture proliferation around boreholes. Liquid nitrogen was flowed through the boreholes to cool the borehole surface. The results show that initial fracture growth is characterized by abrupt starts and stops, and as the fracture propagates outward, the growth appears more continuous. In an early stage, horizontal/radial fractures and vertical fractures are the defining patterns. Horizontal fractures tend to be separated by a specific exclusion distance (i.e., spacing between cracks). While distinct horizontal/vertical fractures and exclusion distance manifest themselves at an early stage, fractures resulting from fracture interactions and curvatures can develop into complex shapes at later stages. Cryogenic thermal loading induces distinctively curved fractures. The tendency of curvature may prevent greater penetration. An increase in the borehole pressure during liquid nitrogen flow, however, can lessen fracture tortu-osity and facilitate radial propagation. A high flow pressure and rate are also advantageous in that they accelerate cooling and fracture propagation.
Cryogenic fracturing , Hydraulic fracturing , Liquid nitrogen , Thermal fractures , Thermal shock , Thermal stress , Well stimulation
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Department of Civil Engineering, Jeju National University, Jeju-si, 63243, South Korea
Carbon Capture, Utilization, and Storage Research Center, King Abdulaziz City for Science and Technology (KACST), Riyadh, 11442, Saudi Arabia
Department of Petroleum Engineering, Colorado School of Mines, 1600 Arapahoe St, Golden, 80401, CO, United States
School of Mining & Geosciences, Nazarbayev University, Qabanbay Batyr Ave 53, Nur-Sultan City, 010000, Kazakhstan
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, 94720, CA, United States
Department of Civil Engineering
Carbon Capture
Department of Petroleum Engineering
School of Mining & Geosciences
Lawrence Berkeley National Laboratory
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