A seller hands you a data room and a headline: 40 wells, roughly 1,800 boe/d net, "long-life, low-decline." That last phrase is the one that costs money. Before you build a model around it, you want to see the package the way it actually produces — not as 40 line items, but as one aggregated stream with a decline you can trust and a small number of wells you know are carrying the rest.
That rollup is a question you can ask in plain language against the record.
Start With the Aggregate, Not the Average
The first move is to pull every well in the package by API and stack their monthly production into a single time series — oil in barrels, gas in mcf, water if you want the full picture. The aggregate curve tells you three things the marketing deck won't:
- Current rate, verified. The combined last-month figure from the record, not a smoothed "representative" month the seller chose. Recent months often lag in state data, so read the trailing 3–6 months rather than the single latest point, which is usually incomplete.
- Shape of the recent trend. Is the group flat, gently declining, or rolling over? A package that's genuinely low-decline shows a shallow slope over the last 12–24 months. A package that peaked two years ago and is easing off tells a different story about where PDP value sits.
- The vintage mix. If half the wells came online in the last 18 months and half are 8-year-old strippers, the blended decline is a mirage — it's steep young wells averaged with flat old ones. You want to see both cohorts separately.
The Decline Rate That Actually Matters
Ask for the decline rate on the aggregate and on each vintage cohort. A single well's decline is noisy; 40 wells summed smooth out the month-to-month scatter and give you a cleaner exponential or hyperbolic fit.
What you're checking is whether the seller's "low-decline" claim survives contact with the data. A group of mature wells might show a base decline of 8–12% annually — genuinely shallow, genuinely valuable. A group dominated by two-year-old horizontals can still be shedding 30–40% year over year, and no amount of packaging changes the arithmetic. Fit the decline on the older, flatter tail if you want the number that governs the back half of your cash flow, and fit it on the young wells separately to see how much rate you'll lose in the first 24 months of ownership.
Find the Wells Carrying the Book
Every package has concentration, and you need to know exactly how much. Rank the 40 wells by current rate and by cumulative-to-date. It's common to find that the top 5 wells make half the volume — which means your valuation is really a bet on those five, and the other 35 are rounding error plus plugging liability.
This is where outlier detection earns its keep. Screen the package for any well producing well above its offsets or its own recent trend. A single well spiking above the pack often has a story: a recent workover that won't repeat, an offset frac giving it a temporary bump, or a load-recovery flush after a shut-in. If one anomalous well is inflating the aggregate rate, your "1,800 boe/d" is really 1,650 boe/d plus a fading transient. Better to know that before you sign than after.
Benchmark the Package Against the Neighborhood
A package doesn't exist in isolation. Compare the group's wells against their county averages and immediate offsets. If the seller's wells consistently underperform nearby wells on the same interval, you're either looking at a completion problem, a spacing problem, or an operator who left production on the table — the last of which is upside if you can execute better, and downside if you can't.
The reverse matters too: if the package outperforms its offsets, ask why. Superior rock is durable; an aggressive artificial-lift program the seller quietly ran up before marketing is not.
What the Rollup Leaves You With
By the end of a single conversational session you should have: a verified aggregate rate on trailing production, a decline rate split by vintage, a ranked list showing where the volume concentrates, any outlier wells flagged for a closer look, and a benchmark against the surrounding field. That's the skeleton of a PDP model, sourced from the record rather than the data room.
None of it replaces geology, title, or an AFE review. But it means you walk into the negotiation knowing which wells you're actually buying, how fast they're fading, and whether "long-life, low-decline" is a fact or a phrase. That's the difference between paying for a package and paying for the two wells inside it that matter.