Stress-mediated closing of fractures: Impact of matrix diffusion
2014 (English)In: Journal of Geophysical Research B: Solid Earth, ISSN 2169-9313, Vol. 119, no 5, 4149-4163 p.Article in journal (Refereed) Published
Fracture apertures may decrease by several mechanisms when the fractures are subject to stress. This paper considers only stress-enhanced dissolution of the crystals on the stressed surfaces. First, it is argued that the stress-induced dissolution is active already at the smallest difference between effective stress on the stressed surfaces and the unstressed surface of a crystal when in contact with water. This is in contrast to the concept that there exists a critical stress below which, this does not happen, assumed in some earlier studies. Second, and in addition to, but independent of the first argument, it is shown that there is a very strong sink for the stress-enhanced dissolved crystal mass due to diffusion into the porous rock matrix. There, the solute reprecipitates on the crystal surfaces in the matrix, which are subject to lower stress than the crystals bearing the load in the fracture. Diffusion into the porous matrix of the rock has not previously been considered in this context. A simple model that includes this sink is developed, and it is shown that matrix diffusion can be the by far largest sink for the solute and can considerably increase the rate of closure of the fractures. It is further found that under some possibly not uncommon conditions, the dissolution rate of quartz crystals becomes essentially independent of the strength of the sinks for the dissolved silica.
Place, publisher, year, edition, pages
2014. Vol. 119, no 5, 4149-4163 p.
closing fractures, critical stress, impact of matrix diffusion, stress dissolution
IdentifiersURN: urn:nbn:se:kth:diva-148256DOI: 10.1002/2013JB010645ISI: 000338009800011ScopusID: 2-s2.0-84902492764OAI: oai:DiVA.org:kth-148256DiVA: diva2:737662
QC 201408132014-08-132014-08-042014-08-13Bibliographically approved