Integrated Carbonate Reservoirs Studies - Linking Static and Dynamic Models to Expand Evaluation Validity in Space and Time
By
Jean-Remy Olesen1, Andrew Carnegie2
(1) Schlumberger Logelco Inc, 11728 Maadi Cairo, Egypt (2) Schlumberger Oilfield Services, Abu Dhabi, United Arab Emirates
The permeability distribution of most carbonate reservoirs is extremely heterogeneous and profoundly affects the reservoir behaviour when subjected to rapid fluid withdrawal. Variations in rock texture, diagenetically altered layers, secondary porosity, solution channels, faults or fractures, all contribute to the complexity of the fluids flow and the reservoir pressures distribution.
In carbonates, conventional open-hole
petrophysical logs do not provide
enough permeability information to allow the building of a realistic reservoir
model. Recent developments in the fields of electrical conductivity and NMR
images evaluation are now providing a much clearer picture of the permeability
distribution. Other recent developments in the interpretation of cased-
hole
pulsed neutron spectroscopy data in carbonate reservoirs allow the accurate
evaluation of depletion profiles in cased
hole
.
The knowledge of the permeability profile acquired in newly drilled in-fill
key-wells can be extended through the evaluation of depletion profiles in
selected cased hole
wells and this can be further extended to field-wide
permeability mapping through fast, efficient, geo-statistical techniques
integrating 3-D surface seismic if available, open-
hole
, cased-
hole
and
production log data with historical well performance data.
Geo-statistical tools were used to match observed water breakthrough and to
predict future water breakthrough. They are based on proportion curve analysis
and on a network approach which is guided by some simple physical rules. It
allows one to detect or exclude specific high permeability paths, such as faults
interpreted from seismic or diagenetically altered layers detected from open
hole
or production data.
An application of this integration is presented in a typical carbonate reservoir.