Gel Placement in Heterogeneous Systems With Crossflow

K.S. Sorbie, R.S. Seright – 1992

Abstract

This paper studies gel placement in stratified reservoir systems where communication exists between layers (crossflow). Gel placement details are strongly affected by the level of interlayer communication, characterized by proximity to vertical equilibrium (VE) conditions. In systems close to VE, viscous crossflow can cause considerable volumes of gelant injected into the high-permeability layer to flow into low-permeability layers, where subsequent gel formation can seriously reduce subsequent waterflood performance. Results from experimental displacements in layered beadpacks and supporting numerical simulations demonstrate the central role of viscous crossflow in gel treatment outcomes for heterogeneous reservoirs.

Key Takeaways

  • Crossflow between reservoir layers critically affects gel placement outcomes — the closer a stratified system is to vertical equilibrium, the more gelant will crossflow into low-permeability layers.
  • In systems near vertical equilibrium, viscous crossflow during gelant injection can cause significant gelant volumes to enter low-permeability layers — where gel formation subsequently damages waterflood performance rather than improving it.
  • The level of interlayer communication (characterized by proximity to VE conditions) must be evaluated before designing a gel treatment in any stratified reservoir with connected layers.
  • Experimental displacements in layered beadpacks combined with numerical simulation provide a validated framework for predicting gelant crossflow behavior as a function of VE proximity, viscosity ratio, and layer geometry.
  • Gel treatments in stratified reservoirs with free crossflow must account for the crossflow dynamics during placement — ignoring crossflow effects can lead to gel forming in the wrong zones and reducing rather than improving sweep efficiency.
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