When someone asks how much a well is ultimately worth in barrels or cubic feet, the answer they are looking for is its estimated ultimate recovery. EUR is a forecast of everything a well will produce over its entire life, from first oil to the day it is no longer economic to run. This guide defines EUR, connects it to the decline curves and reserves categories it is built from, and explains why credible EUR numbers depend on accurate, metered cumulative volumes from the field.
Estimated Ultimate Recovery (EUR) in one line: Estimated ultimate recovery, or EUR, is the total volume of oil or gas a well is expected to produce over its entire producing life, from the beginning of production to its economic limit. It is the sum of what a well has already produced plus a forecast of what it will produce in the future, typically from a decline curve. EUR is a forecast rather than a measured fact, so it carries uncertainty and is refined as more production history accumulates.
EUR is defined by an endpoint: the economic limit, which is the production rate below which the revenue from a well no longer covers the cost of operating it. A well is not produced until it physically stops flowing but until it stops paying, and that economic limit depends on operating costs, prices, and the terms under which the well is held. EUR is the cumulative volume the well will have produced by the time it reaches that limit, so it is inherently tied to economics, not just to the reservoir.
Structurally, EUR has two parts: the production already achieved, which is known from metered history, and the remaining recovery still to come, which must be forecast. Adding the two gives the ultimate figure. Early in a well's life the forecast portion dominates and EUR is quite uncertain; late in life, most of the EUR is already produced and the number is well constrained. This is why an EUR quoted for a brand-new well and one quoted for a mature well carry very different confidence, even when both are expressed as a single volume.
Because it spans the whole life of a well, EUR is the natural unit for comparing wells, valuing acquisitions, and planning development. Type curves - representative decline curves for a play or area - are often expressed in terms of the EUR they imply per well, so that a company can estimate what a new well is likely to recover before it is drilled. But every such figure inherits the assumptions behind it, particularly the economic limit and the decline forecast, so an EUR is only as meaningful as the assumptions stated alongside it.
The most common route to an EUR is decline curve analysis: fit a decline curve to a well's production history, extend it to the economic limit, and integrate the area under the curve to get the cumulative volume the well will produce. The choice of decline form and parameters therefore flows straight through into the EUR - an optimistic high-b hyperbolic fit produces a larger EUR than a conservative exponential fit of the same data. This is why the discipline applied to the decline fit matters so directly to the credibility of the recovery estimate.
EUR also sits at the heart of reserves classification, though the two are not identical. Reserves are the portion of recoverable volumes that meet specific criteria of certainty and commerciality, and they are graded into categories such as proved, probable, and possible according to how confident the estimate is. EUR is the total recovery figure from which reserves are derived: subtracting cumulative production to date from EUR gives the remaining recoverable volume, and the confidence in that remaining volume determines which reserves category it falls into.
Because EUR feeds reserves, and reserves feed the reported value of an oil and gas company, EUR is not a casual number. It is documented, reviewed, and often audited, and it is revised as production history accumulates and the decline trend clarifies. A well that outperforms or underperforms its early forecast will see its EUR moved up or down, and those revisions ripple through reserves bookings. Treating EUR as a living estimate rather than a fixed truth is essential to using it responsibly.
The known half of an EUR - cumulative production to date - is only as trustworthy as the metering behind it, and errors there propagate directly into the ultimate figure and into the reserves derived from it. If cumulative volumes are misallocated among wells, reconstructed from incomplete paperwork, or corrupted by meter problems, then both the starting point of the forecast and the history the decline curve is fit to are wrong, and the EUR is wrong with them. Accurate, well-by-well cumulative volumes are therefore the foundation on which any credible EUR is built.
A cloud SCADA platform such as Merobix contributes precisely this: continuous, timestamped, well-by-well production data captured automatically from field metering over protocols such as Modbus and DNP3, with the full cumulative history retained in one place. Because the data is collected at the source rather than assembled after the fact, it gives the analyst a clean cumulative-production record to anchor the EUR and a clean rate history to fit the forward decline, removing a major source of error from the recovery estimate.
That same continuous record turns EUR into something that can be tested over time rather than set once and forgotten. With live cumulative volumes trended in Merobix against the forecast that underlies the EUR, an engineer can see early whether a well is tracking toward its estimated recovery or diverging from it, and revise the EUR when the evidence warrants. Because EUR revisions flow through to reserves, keeping the cumulative data clean and the forecast under continuous comparison is not just good bookkeeping - it is what keeps a company's reported recoverable volumes tied to how the wells are actually producing.
EUR is the total volume a well is expected to produce over its whole life, including what it has already produced. Reserves are the remaining recoverable volumes that meet specific criteria of certainty and commerciality, graded into categories such as proved and probable. In practice, reserves are derived from EUR by subtracting cumulative production to date and then classifying the remaining volume by confidence.
The most common method is decline curve analysis: a decline curve is fit to a well's production history, extended to the economic limit where the well stops being profitable, and integrated to give total cumulative production. That result, combining production already achieved with the forecast remaining recovery, is the EUR. The choice of decline form and the assumed economic limit strongly influence the number.
Because EUR is a forecast, not a measured fact, and the forecast portion is uncertain, especially early in a well's life. As more production history accumulates, the decline trend clarifies and the estimate is refined, so a well that outperforms or underperforms its early forecast will have its EUR revised up or down. Those revisions then flow through to the reserves derived from the EUR.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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