Numerical Study of the Effect of Dynamic Capillary Pressure on Oil–Water Flow in Tight Reservoirs

Abstract

AbstractDue to the fact that capillary pressure is one of the central key elements defining the oil–water flow behavior in porous media with low permeability, it’s of significance to take the dynamic capillarity (e.g., dynamic capillary pressure, i.e., DCP) into account during water flooding process in formations with extremely low permeability. This article studies the effect of DCP on oil–water flow in low permeable formations by performing reservoir simulation based on a new mathematical model included DCP. In addition, taking four different kinds of well patterns (diamond shaped inverted 9-spot well network, rectangular inverted 9-spot well network, 7-spot well pattern and 5-spot well pattern) for examples, the influence of DCP on displacement characteristics of these well patterns is analyzed. The primary results show that, under a given saturation, DCP is greater than quasi-static capillary pressure, thus, for low permeable formations, DCP was too significant to be neglected. In addition, significant effect of DCP on oil–water flow characterization (e.g., the pressure drop loss, degree of oil recovery) is observed. Specifically, DCP causes pressure drop loss to become larger. The faster the production rate is, the greater the amplitude of pressure drop loss will be. The pressure drop loss range from large to small is the diamond shaped inverted 9-spot well pattern > the rectangular inverted 9-spot well pattern > the 7-spot well pattern > the 5-spot well pattern. Meanwhile, a larger capillary dynamic coefficient leads to a lower degree of oil recovery rate and a lower output per well. As a result, the main objective of this research is to give an alternative perspective to study oil–water flow in low permeability reservoirs.KeywordsLow permeability reservoirsDynamic capillary pressurePressure drop lossDegree of oil recovery