A new micromodel construction procedure has been developed as a tool to better understand and model pore level events in porous media. The construction procedure allows for the almost exact two-dimensional replication of any porous medium of interest. For the case presented here, a berea sandstone was chosen.
Starting with a thin section of the porous medium of interest, a two-dimensional replica of the flow path is etched into a silicon wafer to a prescribed depth. Bonding the etched pattern to a fiat glass plate isolates the flow path and allows the pore level flow events to be studied.
The high resolution micromodels constructed with the new procedure were used to study the effects of oil on the displacement characteristics of foam in a porous medium of intermediate wettability. A crude oil was injected into the micromodel, partially filling it. The oil was then produced under two different displacement schemes. First, a slug of surfactant was used. Second, foam generated in situ, far from the oil bank, was used to displace the oil.
Qualitative observations indicate significant differences at the interface between the oil and the displacing phase. When slug surfactant injection is used, the oil appears to wet the surface. The oil displacement process is efficient due to a large fractional production of oil from the large pores before the surfactant breaks through. When in-situ foam is the displacing phase, the foam is observed to break near the oil interface. The liquid phase in the foam becomes the wetting phase. It is observed to reside in the small pores and to coat most of the grain surfaces. Displacement of oil under this injection scheme is inefficient due to transfer of the surfactant along grain edges and subsequent early breakthrough of the surfactant.