Polymer flooding separate layer

When no crossflow occurs between layers, the performance of a multilayered, linear reservoir flooded under a constant pressure drop can be simulated by computing the displacement performance of each layer separately as a function of time, as described in Sec. 5.5.5. Then, the predicted performance of the composite reservoir is determined by combining the results from individual layers at the same time. Composite results are computed for predetermined time increments by linear interpolation. When crossflow between layers occurs, a numerical model must be used to simulate polymer-flood performance. Consideration of crossflow in polymer flooding is beyond the scope of this text. 

A reservoir consists of two layers separated by a permeability barrier so that there is no flow between layers except at the wellbores. The permeability of the upper layer and lower layers is 1,400 and 33 md, respectively. Table 5.74 gives other properties of the reservoir. A determination of the potential of a polymer flood for this reservoir is desired assuming that displacement is linear. The wells are on 10-acre spacing so that the distance between rows of injection and production wells is 660 ft. Polymer is retained by the reservoir rock Table 5.74 gives the values of polymer retention at the injected concentration of 250 ppm. Retention is assumed to be irreversible, and the density of the rock matrix is taken as 2.65 g/cm. The eflfec-tive IPV is 0.25. Relative permeability relationships given by Eq. 3.197 and 3.198 are assumed to be applicable for both layers. Use constants in Table 3.20 for Layers 1. a , = — 3 for Layer 2. 

Here,/is initial water cut value before the polymer flood 2 is the proportion of the channel sand body kd is permeability ratio Vk is Dykstra-Parsons coefficient of permeability variation m is well pattern density and 0 is a factor affected by the polymer-injection formula (that is to say, how much the effectiveness is affected by factors such as concentration, viscosity, and polymer-bank size). R is the oil recovery before polymer flood N is the connectivity factor between injectors and producers S is the proportion of wells with separate layers and B is the proportion of the wells that adopted the measures of profile modification. 

Wu, L, Chen, P., and Lu, J. 2005. Study of injection parameters for separate layers during the period of polymer flooding. Petroleum Geology Oilfield Development in Daqing 24 (4) 75-77. 

Zhang, Y., Li, C., and Wang, X. 2004. Discussions on the technical of string with backflush for separate layers during the period of polymer flooding. Oil Gas Ground Engineering 23 (9) 26-27. 

---