Summary
Simulation of an in-situ combustion (ISC) process was performed for a
fractured system at core and matrix-block scales. The aim of this work was: (1)
To predict the ISC extinction/propagation condition(s), (2) understand the
mechanism of oil recovery, and (3) provide some guidelines for ISC upscaling
for a fractured system. The study was based on a fine-grid, single-porosity,
multiphase, and multicomponent simulation using a thermal reservoir
simulator.
First, the simulator was validated for 1D combustion using the corresponding
analytical solutions. 2D combustion was validated using experimental results
available in the literature. It was found that the grid size should not be
larger than the combustion-zone thickness in order for the results to be
independent of grid size. ISC in the fractured system was strongly dependent on
the oxygen diffusion coefficient, while the matrix permeability played an
important role in oil production. The effect of each production mechanism was
studied separately whenever it was possible. Oil production is governed mainly
by oil drainage because of gravity force, which is enhanced by viscosity
reduction; possible pressure-gradient generation in the ISC process seems to
have a minor effect. The nature (oil-production rate, saturations distribution,
shape of the combustion front) of ISC at core scale was different from that in
a single block with surrounding fracture. The important characteristics of
different zones (i.e., combustion, coke, and oil zones) at block scale were
studied, and some preliminary guidelines for upscaling are presented.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
22 August 2008
- Meeting paper published:
20 October 2008
- Revised manuscript received:
24 January 2009
- Manuscript approved:
7 February 2009
- Published online:
11 February 2010
- Version of record:
24 February 2010
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