Pressure Modification or Barrier Issues during Polymer Flooding Enhanced Oil Recovery

Abstract

Effective oil displacement from a reservoir requires adequate and properly directed pressure gradients in areas of high oil saturation. If the polymer bank is too large or too viscous during a polymer flood, the pressure drops from the injection well to the polymer front may act as a pressure modification or barrier by usurping most of the downstream driving force for oil displacement. Polymer injection pressures must be limited. The maximum allowable injection pressure is commonly constrained by caprock integrity, injection equipment, and/or regulations, even though fractures can be beneficial to polymer injectivity. This paper examines when the pressure-barrier concept limits the size and viscosity of the polymer bank during a polymer flood. Analytical and numerical methods are used to address this issue. We examine the relevance of the pressure modification concept for a wide variety of circumstances, including oil viscosities ranging from 10 cp to 1650 cp, vertical wells versus horizontal wells, single versus multiple layered reservoirs, permeability contrast, and crossflow between layers. We also examine the relation between the pressure-barrier concept and fractures and fracture extension during polymer injection. We demonstrate that in reservoirs with single layers, the pressure-barrier concept only limits the optimum viscosity of the injected polymer if the mobility of the polymer bank is less than the mobility of the displaced oil bank. The same is true for multizoned reservoirs with no crossflow between layers. Thus, for these cases, the optimum polymer viscosity is likely to be dictated by the mobility of the oil bank, unless other factors intervene. For multizoned reservoirs with free crossflow between layers, the situation is different. A compromise must be reached between injected polymer viscosity and the efficiency of oil recovery. This work is particularly relevant to viscous oil reservoirs where polymer viscosities are substantially lower than the oil viscosity.

Study of the Rheological Characteristics of Sediment-Gelling Compositions for Limiting Water Inflows

“…In recent years, researchers have begun to pay serious attention to finding technological solutions to eliminate the consequences of water breakthrough through highly permeable interlayers of heterogeneous reservoirs while using the so-called flow-diverting technologies (FDT) [4][5][6][7][8]. Most of the functions of FDT are aimed at the formation of a water barrier by pumping the appropriate compositions into injection wells.…”

“…The obtained results of the rheological characteristics of the proposed SGCs were compared with the results of experimental works [1][2][3][4][5][6][7][8][9][10][11][12][13], which made it possible to determine the optimal compositions for further research.…”

“…This explains the great attention of researchers on this problem. Like any other process that is a serious problem, watering also requires the establishment, proper understanding, and analysis of the causes of excess water supply [8]. To date, methods have been developed and proposed, according to which problems and their nature are determined using modern diagnostic methods, which make it possible to prevent and eliminate the source of excessive watering.…”

The method of non-stationary flooding and the conditions for its effective use in the operation of an oil field

“…The effectiveness of this method is influenced by the geological structure of the deposit, the current state of development (the flooding system, the working stock of wells, the level of waterlogging, the proportion and nature of the production of geological reserves), heterogeneity in permeability, etc [5]. Therefore, the need to predict the effectiveness of the cyclic impact process is an urgent task.…”