Stage 3: Going Beyond
- Volumetrics
Petrophysical in-place volumes per unit area: how net pay, porosity and water saturation become oil and gas in place with the formation volume factors, how the fluid properties and the reservoir pressure and temperature are estimated, and how errors in the inputs propagate to volume.
- Lithofacies Modelling
Assigning a rock type to each depth sample from the logs: deterministic rules, unsupervised clustering and supervised classification, with the choice of curves, the standardisation across wells and the handling of missing data that all three share.
- Laminated Sand/Shale Analysis
Why laminated sand breaks conventional analysis, how the Thomas-Stieber diagram identifies the shale distribution, and how to get sand-only porosity, resistivity and water saturation.
- Pore Pressure
How pore pressure is estimated from sonic and resistivity logs: the overburden and hydrostatic references, normal compaction trendlines, and the Eaton, Bowers and equivalent depth methods, with the loading and unloading distinction.
- Shear Log Modeling
Why a shear log is modeled when no dipole sonic exists, and how the Greenberg-Castagna, Castagna, Brocher, Eskandari and Carroll Vp-Vs regressions differ, with unit handling, calibration and quality checks.
- Geomechanics
How to get dynamic elastic moduli from sonic and density logs, convert them to the static values that govern drilling and fracturing, estimate strength, friction angle, cohesion and the Biot coefficient, and rank brittleness, with explicit warnings about how local the empirical relations are.
- Wellbore Stability (1D Geomechanical Model)
How to build a one-dimensional geomechanical model for a vertical well: vertical stress from density, minimum and maximum horizontal stress, the stress around the wellbore, breakout and breakdown pressures, and the mud weight window, with emphasis on what must be calibrated and how large the uncertainties are.
- Carbonate Analysis
How Lucia's rock fabric number, separate-vug porosity and cementation exponent are used in carbonates, and how permeability, Swirr and Sw are kept consistent.
- SwH Analysis
How capillary pressure, the Leverett J-function, rock quality and the free water level combine into a saturation-height model, and how to choose, calibrate and check one.
- Relative Permeability
How irreducible and residual saturation, the Brooks-Corey and power-law curves and the fractional flow combine into a log-based relative permeability, and how to choose and check the pieces.