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.