The Effect of Dead End on Imbibition Face Condition During Counter-current Spontaneous Imbibition

Abstract

Counter-current spontaneous imbibition is one of the main displacement processes in fractured reservoirs. Determination of an imbibition face boundary condition has been the main challenge in this area. A recent work presents a new approach that proposes a solution to specify this boundary condition in the case of infinite core length, which results in a saturation less than the maximum reachable wetting phase saturation. The new method is applicable only in the case of infinite cores and cannot be applied in the case of counter-current spontaneous imbibition in matrix blocks of fractured reservoirs that are finite in length. The case of finite core, which includes a dead end, makes the situation very complex and a new challenge in this area. The present article presents a solution for specifying an imbibition face boundary condition when the imbibition front reaches the dead end of the core. The methodology is based on the investigation of the physics of the counter-current imbibition process in a finite core that includes a dead end. Numerical simulation was used to compare the non-wetting phase recovery rate by implementing different boundary conditions in one- and three-dimensional blocks. The results for the one-dimensional core show that the rate of oil recovery during counter-current spontaneous imbibition is higher when imbibition face saturation is higher, but the recovery fractions reach the same value and rate at late times. For a matrix block, it was illustrated that the new boundary condition leads to a higher recovery rate.

Keywords:

• capillary pressure
• counter-current imbibition
• dead end
• numerical simulation
• open face condition