A note on a method for measuring the transport properties of a formation using a single well

Abstract

For some subsurface investigations of contaminant transport, particularly those conducted in consolidated material, the costs related to well construction prohibit the installation of a comprehensive field of monitoring wells. To alleviate this problem for fractured, low‐porosity formations, a method for measuring transport properties using a single well was developed. The method involves the injection of fluid and tracer over a short duration which establishes a radial source condition in the formation. Following this the ambient flow is allowed to carry the tracer back through the injection well where tracer concentration is monitored passively, in situ. To interpret the experimental results, a numerical model was adapted to account for the mass balance of solute in the source/monitoring well during the injection and monitoring periods. The model accommodates advection‐dispersion, adsorption, decay, and matrix diffusion in a framework of fractures having a variety of geometries. To illustrate the use of the method, a field experiment was conducted using a single well which is intersected by a discrete horizontal fracture in a flat‐lying shale and limestone formation. Interpretation of the results agreed well with the interpretation of other tracer experiments conducted previously in the same fracture plane. This suggests that the method may yield defensible estimates of transport properties such as matrix porosity and groundwater velocity in geological formations that are expensive and difficult to characterize.