A common problem in many waterflooded oil reservoirs is early water
breakthrough with high water cut through highly conductive thief zones.
Thermally active polymer (TAP), which is an expandable submicron particulate of
low viscosity, has been successfully used as an in-depth conformance to improve
sweep efficiency of waterfloods.
This paper describes the workflow to evaluate technical feasibility of this
conformance technology for proper pilot-project designs supported with detailed
simulation studies. Two simulation approaches have been developed to model
properties of this polymer and its interaction with reservoir rock. Both
methods include temperature-triggered viscosification and adsorption/retention
effects. Temperature profile in the reservoir is modeled by energy balance to
accurately place this polymer at the optimum location in the thief zone. The
first method considers a single chemical component in the water phase. The
second method is based on chemical reactions of multiple chemical components.
Both simulation approaches are compared and discussed.
Results show that temperature-triggered polymers can increase oil recovery
by viscosification and chemical adsorption/retention, which reduces thief-zone
permeability and diverts flow into unswept zones. Sensitivity analyses suggest
that ultimate oil recovery and conformance control depend on the thief-zone
temperature, vertical- to the horizontal-permeability ratio
(Kv/Kh), thief-zone vertical location,
injection concentration and slug size, oil viscosity, and chemical adsorption
and its reversibility, among other factors. For high-flow-capacity thief zones
and mobility ratios higher than 10, oil recoveries can be improved by
increasing chemical concentration or slug size of treatments, or both.
Reservoirs with low Kv/Kh (< 0.1) and
high permeability contrast generally shows faster incremental recoveries than
reservoirs with high Kv/Kh and strong water
The presented workflow is currently used to perform in-depth conformance
treatment designs in onshore and offshore fields and can be used as a reference
tool to evaluate benefits of the TAP in waterflooded oil reservoirs.
© 2012. Society of Petroleum Engineers
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- Original manuscript received:
29 April 2011
- Meeting paper published:
19 July 2011
- Revised manuscript received:
17 August 2011
- Manuscript approved:
25 September 2011
- Published online:
13 February 2012
- Version of record:
29 February 2012