The E&P Synthesis
on Carbonate Reservoirs addresses practical
distinction of the different carbonate
play types and understanding of the
various controls on reservoir performance
and recovery efficiency using 202 carbonate
field analogs worldwide. We have classified
carbonate reservoir plays with an emphasis
on reservoir distribution and geometry.
Six major play types have been defined:
1) carbonate sand, 2) organic build-up,
3) muddy dolomite/chalky limestone,
4) primary chalk, 5) unconformity and
megakarst and 6) late burial diagenesis.
For each play type, important exploration
lessons are summarized by: 1) examining
the pre-discovery concepts, including
evolution of concepts and discovery
methods and 2) analysing the test results
of exploration wells and their implications.
These are followed by detailed discussions
on the various play elements (i.e.,
reservoir, source, seal and trap) and
their coordination in petroleum systems
to provide better exploration approaches
and strategies for the various play
types.
For the purpose of field development,
the studied reservoirs have been grouped
by examining their production history
and then by looking within these groups
to see what diagenetic and/or depositional
features were most important in producing
the observed production consequences.
This approach has produced six groups
of carbonate reservoirs: 1) heavy and
viscous oil reservoir, 2) karstic/fractured
oil reservoir, 3) chalky microporous
oil reservoir, 4) conventional carbonate
oil reservoir, 5) "reefal"
build-up oil reservoir, and 6) gas/condensate
reservoir. For each reservoir type,
multi-variable statistical analyses
have been carried out in order to understand
the relationship between recovery efficiency
on the one hand, and API gravity, viscosity,
well spacing, reservoir depth, field
size and matrix porosity/permeability.
Systematic analysis and comparison of
production history curves for the different
reservoir types and/or under different
producing mechanisms have allowed a
better understanding of the various
controls on reservoir performance and
recovery efficiency. [view
outline]
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