Blog · RFour Energy
Technical notes
and field tutorials.
Articles on reservoir engineering, production surveillance, decline analysis, and applied machine learning in upstream oil & gas. Written for engineers who want to understand the physics, not just run the calculation.
Rock Typing Reimagined
Building a Python, agentic AI, Excel, and dashboard framework for modern reservoir
characterization. Six methods, one platform — Winland R35, FZI/HFU, PGS,
Modified Lorenz, Leverett J-function, and ML on logs. Where the calculations end
and the interpretation begins.
Reading the Whole Production System
A practitioner's guide to nodal analysis. Where IPR meets VLP, why the operating point
is never decided at any single component, and how to translate seventy years of
correlations into something that runs on your laptop. Equations kept to what's useful,
references kept honest, opinions kept brief.
Hydrocarbon Reserves in Probabilities
Why P50 isn't enough — and how Monte Carlo Simulation transforms volumetric reserves
estimation. Probabilistic OGIP/OOIP, choosing the right distribution per parameter,
multi-zone aggregation, tornado analysis, and the upcoming MCVR tool.
Reciprocal Rate Method — reserves from rate-time data alone
When Arps hyperbolic fits over-extrapolate by 40% or more, the reciprocal rate plot
offers a theoretically rigorous second opinion. Plot 1/q vs Np/q, fit a line,
take the inverse slope. Worked example, log-log cross-check, and the factor-of-2 caveat
for gas wells.
The Complete Guide to Gas Material Balance Analysis
How to estimate OGIP and identify drive mechanism from pressure decline. P/Z plot,
Cole plot, Roach plot, aquifer modeling across four classical models, and three worked
numerical examples spanning volumetric, water drive, and geopressured reservoirs.
Ershaghi X-Plot — waterflood performance & ultimate recovery
Mature waterfloods need a different forecasting tool than rate-time decline. Ershaghi's
log-WC vs cumulative oil linearization extracts ultimate recovery directly from data
the operator already has. Worked example, window selection, and engineering override.
Chan diagnostic plot — reading water production mechanisms
Coning, channeling, or near-wellbore problem? Chan's 1995 diagnostic plot turns
water-oil ratio time series into a mechanism identification tool. Read it correctly
and the workover plan writes itself.
Arps decline curve analysis — a practical guide
When to use exponential, hyperbolic, or harmonic. How to read the b-factor as reservoir
physics. Window selection, terminal decline switch, and common pitfalls when forecasting
EUR.
Understanding Coleman-Turner Critical Rate for Gas Wells
Gas wells don't fail because the reservoir runs dry — they fail because liquids start
winning the upward race. A practical guide to the equation, the physics behind it,
and how to read the safety ratio in the field.
More articles coming.
Topics in the pipeline: physics-informed ML for well health classification, intermittent producer detection, field-scale intervention ranking, and multi-zone correlation for probabilistic reserves.
Topics in the pipeline: physics-informed ML for well health classification, intermittent producer detection, field-scale intervention ranking, and multi-zone correlation for probabilistic reserves.