Experiments on imbibition mechanisms of fractured reservoirs by microfluidic chips

To solve the problems of long experiment period and difficult measurement in core imbibition experiments, fracture matrix microfluidic chips of different sizes, boundary conditions and wettability regulated by surface property modification were designed to research the imbibition mechanisms of oil-water, oil-surfactant solution and oil-Winsor III type surfactant solution. In the oil-water, and oil-wettability modification system imbibition process, oil was replaced from the matrix through Haines jump, the capillary back pressure was the main resistance blocking the flow of oil, the reduction of interfacial tension caused the weakening of Haines jump, reduction of oil discharge rate, and increase of oil recovery. The imbibition of oil-water or oil-surfactant solution with low interfacial tension was a counter- current imbibition process dominated by capillary force, in which all boundaries had similar contribution to imbibition, and the recovery data obtained from this experiment fit well with the classic imbibition scaling equation. The imbibition of oil and Winsor III type surfactant solution was a co-current imbibition process dominated by gravity under super-low interfacial tension, and is essentially the formation and re-balance of neutral microemulsion. The imbibition dynamics obtained from this experiment fit well with the modified imbibition scaling equation.

Automated summary

Microfluidic chips with fracture matrix of various sizes, boundaries, and wettability were designed for studying oil-water, oil-surfactant solution, and oil-Winsor III type surfactant solution imbibition mechanisms. Results showed that reducing interfacial tension weakened capillary forces, affecting oil flow and recovery rates in different systems. The experiments demonstrated that capillary forces and gravity played key roles in the imbibition processes under different interfacial tension conditions.