MODELING OF MULTISTEP DRAINAGE PROCESS USING THE EXTENDED INTERACTIVE TUBE-BUNDLE MODEL

The relative permeabilities at low saturation and high capillary pressure are important for any drainage process such as CO2 storage and steam-assisted gravity drainage. The relative permeabilities can be estimated by analyzing the wetting phase production histories at each step in a multistep drainage process. Different from the conventional porous plate method, the multistep drainage process applies a plastic membrane to significantly reduce experiment time while prevent the nonwetting phase from being discharged from the porous medium The conventional tubebundle model has some difficulties in modeling this process because in a drainagetype process the sealing effect of the membrane significantly changes the multiphase flow pattern. In this paper, an extended interactive tubebundle model (ITBM) was developed to model this process. First, in order to qualitatively model this process, a new threetube interacting capillary model was developed and the reverse flood and bidirectional flood were properly modeled. This model also explains in concept why, in this process, the phase with lower mobility determines the wetting phase production history. After that, the threetube interacting capillary model was extended to a complex ITBM, consisting of hundreds of tubes. The saturation profiles along the porous medium, the wetting phase production curves, and the multistep drainage process were all successfully modeled. The application of the ITBM indicates that it can better represent the pore structure of a porous medium and potentially be applied to history match a multistep drainage process.