September 12, 2025
Reading a Reservoir From Its Production Data
Before the simulators, we learned to listen to a field. A short note on what the numbers were always trying to tell us.
There is a temptation, now that we can model everything, to forget that a reservoir will tell you most of what you need to know if you simply watch it produce.
The decline curve is a confession
A well that is declining at a steady percentage each year is not being shy about its future. The arithmetic of decline analysis has not changed since I was a young engineer with a slide rule, and it remains the most honest forecast we have.
A model tells you what you assumed. A decline curve tells you what the rock decided.
What I tell young engineers
- Plot the data before you fit it.
- Trust the long, boring trend over the exciting anomaly.
- A pressure survey is worth a thousand assumptions.
The tools have changed. The discipline has not.