Maximising Oil Recovery Through Thermally-Activated Polymer Placement

The presence of a thief zone in oil reservoirs presents many complications for operators. Perhaps the most important of these issues is early water breakthrough. A solution has been presented which ameliorates sweep in the pay zone and does not exacerbate any pre-existing injectivity problems. Thermally activated polymer (TAP) is an expandable micro-particle injected at close-to-water viscosity which has been efficaciously implemented as a water flood conformance control technique.

This paper has used simulations to explore the reservoir properties, as well as various existing and innovative techniques which may improve the efficiency of this technology. An economic analysis was also carried out to determine the feasibility of a given project. A 2D conceptual model was used to investigate the reservoir conditions required for an optimal treatment before examining the polymer properties and injection techniques available to further enhance its effectiveness. The model was able to successfully simulate temperature-initiated pore blockage by the TAP particulates which diverted subsequently-injected water into the surrounding, un-swept layers.

Simulations revealed that these polymers are able to significantly improve recovery efficiency by the blockage of flow pathways in the high-permeability streak. For an effective treatment, it was found that reservoirs with a low vertical-to-horizontal permeability ratio (0.05 - 0.1) and a high permeability contrast between the thief zone and surrounding layers (1600–2000mD thief zone) are most ideal for TAP implementation. Sensitivity analyses and optimisations found that optimal treatments depend on a plethora of parameters, namely: TAP concentration; slug size; treatment start date; method of injection; and spacers.

The method of injection presents a new opportunity to explore for future TAP treatments. With appropriate design it is possible to improve oil recovery and reduce water production, leading to an improved NPV and decreased carbon footprint from reduced water handling.