PVT from correlations
Bubble point, solution GOR, Bo, oil and gas viscosity, z-factor and Bg from gravity, temperature and pressure — the module the other reservoir tools call.
Reservoir
Volumetric OOIP / OGIP with Monte Carlo
The volumetric equation run tens of thousands of times over triangular distributions, returning P90, P50 and P10 instead of one number that pretends to be certain.
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How it is calculated
- OOIP = 7758 · A · h · φ · (1 − Sw) / Bo, in acres, feet and STB. For gas the constant is 43 560 and the divisor is Bg in ft³/scf.
- Each variable is sampled from a triangular distribution defined by your low, most-likely and high values, using inverse-CDF sampling.
- The sampler is seeded, so the same inputs always produce the same percentiles and a result can be quoted in a report and reproduced later.
- P90 is the low estimate and P10 the high one, following the industry convention rather than the statistical one.
Standards it speaks
Where this stops being true
The variables are sampled independently, and in a real field they are anything but — area and thickness come from the same structural interpretation, porosity and water saturation from the same logs and the same cementation exponent. Ignoring that correlation makes the distribution narrower than the truth, so a P10–P90 range from this tool is optimistically tight. A triangular distribution is also a statement about your beliefs, not a measurement: the answer inherits whatever the high and low values encode, including the tendency to set them too close together.
The capability that automates this
- SR-11Forecasting with UncertaintyProduces P10, P50 and P90 production forecasts whose spread is calculated, not chosen to look reasonable.
- SR-14Automated Reserves Estimation & DCAFits decline curves across every well in the field on a consistent basis and keeps the audit trail that a reserves report needs.
Related tools
Gas material balance — P/z
Paste reservoir pressure against cumulative production and read gas in place off the intercept, with z computed at every point rather than assumed constant.
EOR method screening
Ten EOR methods checked against your reservoir and fluid properties, each one told to say exactly which criterion rules it out.
Minimum miscibility pressure
CO₂ and lean-gas MMP from three independent correlations, corrected for injectant impurities, with the spread between them shown rather than averaged away.