Fracture sealing by mineral precipitation: The role of small‐scale mineral heterogeneity. Issue 14 (30th July 2016)

• Record Type: Journal Article
• Authors: Jones, Trevor A.; Detwiler, Russell L.
• Is Part Of: Geophysical research letters. Volume 43:Issue 14(2016)
• Page Start: 7564
• Page End: 7571
• Publication Date: 2016-07-30
• Subjects: Reactive Transport -- Permeability Alteration -- Fracture Flow; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL069598
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Fractures are often leakage pathways for fluid in low‐permeability rocks that otherwise act as geologic barriers in the subsurface. Flow of fluids in chemical disequilibrium with fracture surfaces can lead to mineral precipitation and fracture sealing. To directly evaluate the role of small‐scale mineral heterogeneity on mineral precipitation, we measured CaCO3 precipitation in a transparent analog fracture that included randomly distributed small‐scale regions of CaCO3 on one of the borosilicate surfaces. Steady flow of a well‐mixed CaCl2 ‐NaHCO3 solution ( log ( Ω CaC O 3 ) = 1.44) resulted in significant mineral precipitation during the 82 day experiment. Localized mineral precipitation reduced flow within regions of the fracture, but small‐scale reaction‐site heterogeneity allowed preferential flow to persist through pathways that contained 82% less area of CaCO3 regions than the fracture‐scale average. This resulted in a significant reduction in measured precipitation rate; excluding these effects results in more than an order‐of‐magnitude underestimation of fracture sealing timescales. Key Points: Mineral heterogeneity localizes precipitation‐induced aperture reductions Localized precipitation reactions enhance preferential flow channeling Preferential flow channels significantly increase time for fracture sealing