Reservoir Characterization & Geological Modeling (QCB4043)

A compilation of key terms and definitions related to reservoir heterogeneities and geological modeling for petroleum geoscience.

Reservoir Heterogeneity

Variations in reservoir properties as a function of space impacting production and fluid flow.

•Small to large scale geologic features

•from static reservoir characterization (significant and

non significant)

•from dynamic reservoir characterization (significant)

Micro Heterogeneity

Heterogeneities at the grain level affecting pore and pore throat.

•Produced by deposition of sediments and subsequent  compaction, cementation and dissolution phenomena

•Identified from laboratory measurements → variations  in pore and pore throat size, grain shape and size,  throat opening, minerals, pore roughness, etc.

•Create preferential paths for displacing fluids while  residual or trapped hydrocarbon is left behind

Macro Heterogeneity

Heterogeneities at the core level affecting porosity and permeability.

•Identified from laboratory measurements → variations  in porosity, permeability, fluid saturation, capillary  pressure, wettability, etc.

•Used to calibrate logs, well tests, to provide inputs to  flow simulators

•Influence the shape of the front of the displacing fluids  (hence determine the amount of bypassed hydrocarbon)

Mega Heterogeneity

• Heterogeneities between wells impacting lateral continuity.

• Identified from transient pressure well test  analysis, log correlations, high resolution  seismic, investigated using reservoir simulation → lateral discontinuities of individual strata,  pinchouts, fluid contacts, trends, reservoir  compartmentalization…

• Same impact as macroscopic heterogeneities,  but on a larger scale

Giga Heterogeneity

Heterogeneities at the basin level influenced by original depositional  setting or subsequent structural  deformations and modifications due to tectonic activities.

Sealing Fault

A fault that prevents fluid movement between reservoir units.

Semi-Sealing Fault

A fault that restricts but does not fully block fluid movement.

Non-Sealing Fault

A fault that allows free flow of fluids across the fault plane.

Permeability Zonation

Variation in permeability within genetic units affecting fluid flow.

Clay Smearing

Injection of clay into the fault plane causing low permeability zones.

Diagenesis

The physical and chemical changes occurring in sediments as they become rock.

Fractures in Reservoirs

Cracks within rocks that can enhance or hinder fluid flow depending on their nature.

Genetic Unit Boundaries

Stratigraphic discontinuities representing variations in deposition.

Baffles

Geological features that impede fluid flow, often associated with shale.

Lamination

Thin layers of sedimentary deposits resulting from deposition processes.

Cross-Bedding

Sedimentary structures formed by the movement of sediment in flows.