Microscopic Analysis on Fluid Displacement Phenomena in Porous Media

The investigators have constructed a2-D micromodel that simulated a pore network in porous media and developed an experimental apparatus to observe and analyze pore-scale fluid displacement phenomena.1.Micromodel ConstructionThe method of producing glass micromodels is as follows：(1)designing and drawing a pnetwork by computer，that simulates a network of flow channels in porous media，(2)printing the pore network on parating a pnetwork by computer，that simulates a network of flow channels in porous media，(4)projecting the masking film on the glass plate with UV light to polymerize the photoresist sections that are not covered by the masking pattern，(5)washing away the unpolymerised photoresist on the pore network，(6)etching the pore network by soaking the plate into HF，(7)sealing the etched plate on a cover plate by heating in an electric furnace.2.Analysis of fluid displacement behaviorOil displacement phenomena by water and polyming in an electric furnace.2..Analysis of fluid displacement behaviorOil displacement phenomena by water and polymerize the furnace.After the pore network in the micromodel was saturated with oil，water and 200-ppm polyacrylamide solution were injected to displace oil at a constant flowrate using a micro-feeder pump。Three oils with different viscosities of 1.5，28，55mPa·s were used in each experiment。The oil-displacement phenomena were observed through a microscope and recorded on videotape by a color CCD camera.The video-recorded sequences were analyzed to find the features of oil displacement for a pore scale.The following conclusions were obtained by analyzing the influence of oil viscosity，flowrate and fluid rheology on oil displacement：(1)areal sweep efficiency becomes higher with decreasing oil viscosity when water displaces oil；and(2)polymer solution is effective to improving areal sweep efficiency。The micromodel apparatus being developed in this study would be a useful tool to observe pore-scale oil displacement phenomena quickly.

The investigators have constructed a 2-D micromodel that simulated a pore network in porous media and developed an experimental apparatus to observe and analyze pore-scale fluid displacement phenomena.1.Micromodel ConstructionThe method of producing glass micromodels is as follows : (1)designing and drawing a pore network by computer, that simulates a network of flow channels in porous media, (2)printing the pore network on a transparency film (making a masking-pattern film), (3)coating a glass plate uniformly with a photoresist by a spin coater, (4)projecting the masking film on the glass plate with UV light to polymerize the photoresist sections that are not covered by the masking pattern, (5)washing away the unpolymerised photoresist on the pore network, (6)etching the pore network by soaking the plate into HF, (7)sealing the etched plate on a cover plate by heating in an electric furnace.2.Analysis of fluid displacement behaviorOil displacement phenomena by water and polymer solutions have been studied using the micromodel. After the pore network in the micromodel was saturated with oil, water and 200-ppm polyacrylamide solution were injected to displace oil at a constant flowrate using a micro-feeder pump. Three oils with different viscosities of 1.5,28,55 mPa・s were used in each experiment. The oil-displacement phenomena were observed through a microscope and recorded on videotape by a color CCD camera. The video-recorded sequences were analyzed to find the features of oil displacement for a pore scale. The following conclusions were obtained by analyzing the influence of oil viscosity, flowrate and fluid rheology on oil displacement : (1)areal sweep efficiency becomes higher with decreasing oil viscosity when water displaces oil ; and (2)polymer solution is effective to improving areal sweep efficiency. The micromodel apparatus being developed in this study would be a useful tool to observe pore-scale oil displacement phenomena quickly.