Simulation of micellar-polymer flooding of a layered oil reservoir of nonuniform thickness

Abstract

The dynamics of oil displacement from a layered reservoir of nonuniform thickness consisting of two hydrodynamically connected layers of different absolute permeability is studied. Results of numerical calculations are given. The influence of the main determining factors on the oil displacement dynamics is studied.A promising method for increasing the reservoir production is micellar-polymer flooding [1]. Because of the low surface tension on the boundary of the micellar solution with the reservoir fluids, almost the entire oil is set in motion. The higher viscosities of the micellar solution and the injected spacer fluid bank (aqueous polymer solution) compared to the oil viscosity allow an increase in the displacement area.As is known, real oil reservoirs are nonuniform, one of the main types of nonuniformity of porous media is permeability variation across a section of monolithic reservoirs [1]. We consider the profile problem [2] in a two-dimensional region. A mathematical model for micellar-polymer flooding is given in [3]. In [4], this model is extended to the case of nonuniform layered reservoirs, and in [5], to the case of pattern flooding in a well system.The present paper gives the results of a numerical study of micellar-polymer flooding based on models [3-5] for the case of a nonuniform layered reservoir.1. Oil Displacement from a Nonuniform Layered Reservoir with Specified Volume Flow Rate of the Injected Fluid. We consider various flooding modes in increasing order of complexity.We first study oil displacement by water in an oil reservoir of nonuniform thickness consisting of two layers of different absolute permeability (Fig. 1). We solve the problem with a specified volume flow rate of the injected fluid Q(t). Let the filtration region be a square (l y = l x ). The parameters of the porous medium and the hydrodynamic parameters of the fluids (oil and water) being filtered are chosen as follows: (s 0 α ) * = 0, k α = (s 0 α ) 2 , μ α = const, and s 0 10 = 1. We also set Q(t) = 1, l x = l y = 1, and k (1) = 1. Figure 2 shows oil saturation isolines at the moment of injection of a water volume 0.2V pore , for uniform reservoir (k (2) = k (1) = 1) and nonuniform reservoir (k (2) = 6).Unlike in the uniform reservoir, the displacement dynamics in the reservoir of nonuniform thickness has the following features: in the high-permeability layer, the fluids move more rapidly, and although in the bottom low-permeability layer, the absolute permeability is the same as in the uniform layer, the fluids in it move more slowly. According to the problem formulation, the amount of the fluid injected into each layer is identical in the uniform and nonuniform cases. Therefore, the lower rate of displacement in the lower layer compared to that in the uniform layer is explained by the cross-flow of part of the fluid from this layer to the top layer. Hence, in the high-permeability layer, the filtration flux is higher. Nevertheless, with time, the displacement covers the entire zone of low permeability. In this case, ac...

The Application of Signal Collection and Disposal Technology in Measuring the Front of Oil and Water with Polymer Flooding

“…This research results have been validated by tertiary recovery technology [1]. The mechanism on viscoelastic polymer flooding basis on the numerical simulation, physical model and nuclear magnetic resonance technology is perfect [2][3][4], but the theory and technology of percolation and residual oil distribution aren't studied deeply. We have mastered the technology of making the large physical model, so the front of water and oil is measured by signal collection and dealing technology in this paper.…”