Laboratory method for investigating permeability upscaling

The purpose of this work is to describe, evaluate, and demonstrate a laboratory-based method for physically investigating permeability upscaling. The method makes use of a simple instrument, the gas permeameter, to acquire rapid, precise, and nondestructive permeability measurements from heterogeneous blocks of dry rock. Critical to investigating permeability upscaling is the ability to acquire data at multiple sample supports subject to consistent boundary conditions and flow geometry. Such measurements, spanning almost 4 orders of magnitude on a per volume basis, are made with the gas permeameter by simply varying the size of the permeameter tip seal. The precision and consistency of measurements made in this way were evaluated using a suite of data collected from blocks of three relatively homogeneous materials: Berea Sandstone and two synthetic rocks. Results suggest that measurement error is small (approximately ±1% of the measured permeability) and consistent, and measurements made at different sample supports are free from systematic bias. To demonstrate the ability of this method to measure and quantify upscaling processes, limited data sets were collected with four different-sized tip seals from the Berea Sandstone block. Analysis reveals distinct and consistent trends diagnostic of permeability upscaling relating the sample mean (increased), variance (decreased), and semivariogram to increasing sample support.