Reservoir Characterization Flashcards
7 cards from real SPE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Reservoir Characterization flashcards as text
What is the purpose of a variogram in geostatistical reservoir modeling?
Answer: To quantify spatial correlation and heterogeneity of reservoir properties
A variogram measures how dissimilar values of a property (e.g., porosity) are as a function of distance and direction, defining spatial continuity for geostatistical simulation.
In a pressure-depth plot from MDT data, what does a change in the pressure gradient slope indicate?
Answer: A different fluid phase or density (fluid contact or compartmentalization)
Pressure gradient changes on a P-D plot indicate a different fluid (e.g., oil vs. gas have different densities) or a pressure discontinuity suggesting compartmentalization.
Which concept describes the tendency of a reservoir to flow oil or water based on the relative proportion of each phase present?
Answer: Relative permeability
Relative permeability (kr) is the ratio of effective permeability of a phase at a given saturation to absolute permeability, governing multiphase flow behavior.
What is the 'skin factor' in well testing, and what does a positive skin value indicate?
Answer: A dimensionless measure of wellbore damage that restricts flow; positive skin means additional pressure drop near the wellbore
Skin factor quantifies the additional pressure drop near the wellbore beyond ideal radial flow; positive values indicate damage (reduced permeability) while negative values indicate stimulation.
In clastic reservoirs, which depositional environment typically produces the best reservoir quality due to high energy sorting?
Answer: Fluvial braided channel sands
Braided fluvial channels deposit well-sorted, coarse to medium-grained sands with high porosity and permeability due to high-energy, clean sediment transport.
What technique uses the difference in travel time between compressional (P-wave) and shear (S-wave) velocities to infer fluid type in a reservoir?
Answer: Vp/Vs ratio analysis (AVO/rock physics)
The Vp/Vs ratio is sensitive to fluid content because S-waves do not propagate through fluids; gas typically lowers Vp while Vs remains largely unchanged, reducing the ratio.
Which statistical measure is used to describe the spread or variability of a reservoir property such as porosity across a field?
Answer: Standard deviation
Standard deviation quantifies the dispersion of values around the mean, directly measuring variability of petrophysical properties like porosity across the reservoir.