Reserves and Forecasting · Module R6
Material Balance and Volumetric Cross-checks
Three independent ways to estimate the same volume — volumetrics, material balance and decline analysis — and how to reconcile them. The module works a gas p/z analysis, shows how aquifer support and overpressure distort it, and uses implied recovery factor and abandonment pressure as checks on a forecast.
- Level
- Intermediate
- Position
- Module 6 of 8
- Video
- About 19 minutes, narrated
- Format
- Narrated video lesson with captions and slide reading view; with the certified option, a quiz whose pass unlocks the next module.
What the module covers
- Drive mechanisms and typical recovery factors
- The p/z straight line and its assumptions
- Water-drive and overpressure signatures
- Mapped versus connected gas in place
- Oil material balance as a concept
Learning outcomes
After the module you should be able to:
- Reconcile volumetrics, material balance and decline into one volume story.
- Estimate gas in place from pressure surveys
- Recognise when a straight-line extrapolation is invalid
- Reconcile three volume estimates without averaging them
A short preview
For a dry-gas reservoir without water influx, p/z falls linearly with cumulative production and reaches zero at the original gas in place. If p/z starts at 5,000 psia and has fallen to 4,000 psia after 15 Bscf, the line reaches zero at 15 / (1 − 4,000/5,000) = 75 Bscf. When each new survey pushes that answer higher, the line is curving upward, the classic sign of aquifer support, and a straight-line extrapolation will overstate the gas in place.
Who it is for
Reservoir and production engineers, petrophysicists and geoscientists who estimate, review or report reserves and production forecasts.
Prerequisites: None required; working familiarity with production data and volumetrics helps.
Take the module in the Learning Hub
Reserves and Forecasting: Specialty course, sold separately: eight modules from PRMS classification and decline curves to type wells, material balance, aggregation and the reserves report. The lesson opens in the Learning Hub once the track is purchased; graded quizzes and the certificate come with the certified option.