Effects of velocity and concentration on diffusive transport in low permeability geological systems. (December 2015)

• Record Type: Journal Article
• Authors: Zou, Boyuan; Ohe, Toshiaki; Wogelius, Roy A.
• Is Part Of: Applied geochemistry. Volume 63(2015:Dec.)
• Page Start: 357
• Page End: 365
• Publication Date: 2015-12
• Subjects: Diffusion -- Granite -- Micro-fluidic -- Tuff -- Permeability; Environmental geochemistry -- Periodicals; Water chemistry -- Periodicals; Geochemistry -- Social aspects -- Periodicals; Geochemistry -- Periodicals; 551.9
• DOI: 10.1016/j.apgeochem.2015.09.012
• Languages: English
• ISSNs: 0883-2927

Abstract

Abstract: A new micro-fluidic method, which is known as the Micro-Reactor Simulated-Channel (MRSC) method, has been employed to rapidly determine the effective diffusion coefficients of lithium in three important representative low permeability lithologies including: Melechov granite (Czech Republic), Borrowdale tuff, and Land's End Cornish granite (both UK). The concept of MRSC is similar to the micro chemical reactor which enables fast measurements to be done on a small intact sample. The effective diffusion coefficients were measured and comparisons between the MRSC results and conventional column methods showed excellent agreement. Our measured effective diffusion coefficient for Melechov granite is 1.7 × 10 −12 m 2 /s, directly comparable to previous conventional measurements. However the measurement time of the MRSC method is at least one order of magnitude faster than the conventional method and only requires small reaction volumes (as small as 10 ml). In addition, by exploiting the advantages of the MRSC method, the effects of velocity and concentration on diffusive transport for the two different UK rock types have also been investigated. Depending on flow rate and inlet tracer concentration, the effective diffusion coefficient for lithium in the Cornish granite ranges between 0.9 and 1.5 × 10 −11 m 2 /s while that measured for the Borrowdale tuff varies between 1.2 and 1.6 × 10 −11 m 2 /s. Highlights: Geological application of the Micro-Reactor Simulated-Channel method (MRSC). MRSC advantages include high sensitivity and rapid output (90% less time needed). Diffusion coefficients for Borrowdale Tuff, Cornish Granite, and Melechov granite.