| Abstract |
Capillary imbibition is an important mechanism during water reinjection in fractured porous media. Using an X-ray computerized tomography (CT) scanner, and a novel, CT-compatible core holder, we performed a number of experiments to study air expulsion from rock samples by capillary imbibition of water in a three-dimensional geometry. Different injection rates and fracture apertures were utilized. The existence of two flow periods during imbibition by the matrix was observed. The early-time period can be understood as an infinite acting media and the square root of time model of imbibition with the appropriate characteristic time and length can be used. Although the late-time period has not been analyzed fully, a set of both characteristic times and lengths is proposed. Two different fracture flow regimes were also identified. The first one, named "filling-fracture" shows a variable length plane source due to relatively slow water flow through fractures; the second flow regime, named "instantly-filled fracture", where the time to fill the fracture is much less than the imbibition time, shows a constant plane source imbibition. The behavior of the second regime is very similar to that observed in both counter current and cocurrent one-dimensional imbibition experiments reported previously in the literature. |