# Estimated Ultimate Recovery (EUR): How Oil and Gas Reserves Are Measured

Published: 2026-02-23
Author: Warren Team
URL: https://www.heywarren.com/blog/estimated-ultimate-recovery

---
Estimated Ultimate Recovery is the single most important metric in oil and gas economics — the projected total volume of hydrocarbons a well or field will produce over its entire life. EUR drives drilling decisions, reserve reporting, and stock valuations for every E&P company. Understanding how EUR is calculated and why different approaches produce different numbers is essential for energy investing.

## What Is Estimated Ultimate Recovery?

**Estimated Ultimate Recovery (EUR)** is the total quantity of oil, gas, or natural gas liquids (NGLs) that a well, lease, or field is expected to produce over its economic life — from first production to the point when continuing production is no longer economical.

![EUR equals cumulative production already extracted plus the estimated remaining reserves over the well's economic life.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20660%20125%22%20width%3D%22660%22%20height%3D%22125%22%20role%3D%22img%22%3E%3Ctitle%3EFlow%20diagram%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Crect%20x%3D%2230%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22115%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ECumulative%20Production%3C%2Ftext%3E%3Ctext%20x%3D%22115%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3EProduced%20to%20date%3C%2Ftext%3E%3Cline%20x1%3D%22205%22%20y1%3D%2262.5%22%20x2%3D%22237%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22244%2C62.5%20235%2C57.5%20235%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22245%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22330%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ERemaining%20Reserves%3C%2Ftext%3E%3Ctext%20x%3D%22330%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3EFuture%20estimate%3C%2Ftext%3E%3Cline%20x1%3D%22420%22%20y1%3D%2262.5%22%20x2%3D%22452%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22459%2C62.5%20450%2C57.5%20450%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22460%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22545%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EEUR%3C%2Ftext%3E%3Ctext%20x%3D%22545%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3ETotal%20recovery%3C%2Ftext%3E%3C%2Fsvg%3E)

*EUR equals cumulative production already extracted plus the estimated remaining reserves over the well's economic life.*

**EUR = Cumulative production to date + Estimated remaining reserves**

EUR is typically expressed in:
- **Oil**: Barrels (bbl) or thousand barrels (Mbbl)
- **Gas**: Thousand cubic feet (Mcf), million cubic feet (MMcf), or billion cubic feet (Bcf)
- **Combined**: Barrels of oil equivalent (BOE) — with 6,000 cubic feet of gas equivalent to 1 barrel of oil

## Why EUR Matters

EUR determines nearly every economic decision in upstream oil and gas:

**Individual well economics**: Will this well pay back its drilling and completion costs and generate an acceptable return? A $10 million shale well with a 500,000 BOE EUR at $60/bbl realized price has gross revenue of $30 million — potentially profitable after operating costs and taxes.

**Field development decisions**: Should we develop this discovery? How many wells and what infrastructure should we build?

**Acquisition pricing**: Oil and gas companies value acquisitions primarily based on EUR (PV-10 or PV-15 valuation) applied across acquired wells.

**Reserve reporting**: Companies disclose proved reserves (PV-10) in SEC filings — EUR is the building block.

**Investor valuation**: Stock analysts build sum-of-the-parts valuations based on expected EUR across a company's well inventory.

## The Decline Curve Method

The most common approach to estimating EUR is **decline curve analysis**:

**Basic premise**: Oil and gas wells follow characteristic production decline patterns. By fitting a mathematical curve to early production data, analysts project future production.

**Common decline curves**:

**Exponential decline**: Constant percentage decline per year. Production(t) = qᵢ × e^(−Dt), where qᵢ is initial rate and D is decline rate.

**Hyperbolic decline**: Decline rate slows over time. More common in conventional reservoirs.

**Harmonic decline**: Very slow asymptotic decline. Rare but can occur in certain reservoirs.

**Power-law exponential (Arps hyperbolic, SWPLE)**: Common in unconventional shale wells — steep initial decline followed by long tail.

**Example — Shale well Arps hyperbolic decline**:
- Initial rate (qᵢ): 1,200 BOE/day
- Decline rate (Dᵢ): 70% per year initially
- b-factor: 1.2 (moderately hyperbolic)

The curve declines steeply in year 1 (produces ~250,000 BOE), moderates in year 2 (~120,000 BOE), and continues with gradually slower decline for 20-30 years.

**Total area under the curve = EUR**

## EUR in Shale vs. Conventional

EUR patterns differ dramatically between shale and conventional wells:

![Shale wells typically reach economic limits faster but with steeper early decline; conventional wells produce more steadily over decades.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20800%20210%22%20width%3D%22800%22%20height%3D%22210%22%20role%3D%22img%22%3E%3Ctitle%3EComparison%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Ctext%20x%3D%22230%22%20y%3D%2257.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EShale%20%28typical%29%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%2225%22%20width%3D%22450%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%232563eb%22%2F%3E%3Ctext%20x%3D%22702%22%20y%3D%2257.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%232563eb%22%3EBOE900K%3C%2Ftext%3E%3Ctext%20x%3D%22230%22%20y%3D%22152.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EConventional%20%28onshore%29%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%22120%22%20width%3D%2250%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%237c3aed%22%2F%3E%3Ctext%20x%3D%22302%22%20y%3D%22152.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%237c3aed%22%3EBOE100K%3C%2Ftext%3E%3C%2Fsvg%3E)

*Shale wells typically reach economic limits faster but with steeper early decline; conventional wells produce more steadily over decades.*

### Conventional Wells

- Gradual production buildup as well establishes pressure communication with reservoir
- Moderate decline rate (10-30% per year)
- Long production tail (often 20-50 years)
- Lower initial production but more stable output
- Typical EUR: Highly variable — from 100,000 BOE for modest onshore wells to tens of millions for offshore super-giants

### Shale (Unconventional) Wells

- Very high initial production rate
- Extremely steep year 1 decline (70-85% decline from peak)
- Leveling off after 2-3 years
- Long tail at low rates (1-5% decline per year)
- Typical shale EUR: 300,000 - 1,500,000 BOE per well, depending on basin

**Implication**: Shale wells produce most of their EUR in the first 3-5 years. This is very different from conventional wells, where production profiles extend over decades.

**Treadmill effect**: Shale companies must continuously drill new wells to maintain production — because of steep declines. Maintenance CapEx requirements are enormous relative to traditional producers.

## Reserve Categories (SEC Definitions)

The SEC categorizes reserves by confidence level, and each has implications for EUR estimation:

![SEC reserve classifications by probability of economic recoverability, from proved (90%) to possible (10%).](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20760%20211%22%20width%3D%22760%22%20height%3D%22211%22%20role%3D%22img%22%3E%3Ctitle%3EHierarchy%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Crect%20x%3D%22300%22%20y%3D%2220%22%20width%3D%22160%22%20height%3D%2258%22%20rx%3D%228%22%20fill%3D%22%232563eb%22%2F%3E%3Ctext%20x%3D%22380%22%20y%3D%2254%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22white%22%3ETotal%20Resources%3C%2Ftext%3E%3Cpath%20d%3D%22M%20380%2078%20L%20380%20105.5%20L%20110%20105.5%20L%20110%20133%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%20fill%3D%22none%22%2F%3E%3Crect%20x%3D%2230%22%20y%3D%22133%22%20width%3D%22160%22%20height%3D%2258%22%20rx%3D%228%22%20fill%3D%22white%22%20stroke%3D%22%230891b2%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22110%22%20y%3D%22158%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EProved%20%281P%29%3C%2Ftext%3E%3Ctext%20x%3D%22110%22%20y%3D%22176%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E90%25%20confidence%3C%2Ftext%3E%3Cpath%20d%3D%22M%20380%2078%20L%20380%20105.5%20L%20290%20105.5%20L%20290%20133%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%20fill%3D%22none%22%2F%3E%3Crect%20x%3D%22210%22%20y%3D%22133%22%20width%3D%22160%22%20height%3D%2258%22%20rx%3D%228%22%20fill%3D%22white%22%20stroke%3D%22%230891b2%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22290%22%20y%3D%22158%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EProbable%20%282P%29%3C%2Ftext%3E%3Ctext%20x%3D%22290%22%20y%3D%22176%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E50%25%20confidence%3C%2Ftext%3E%3Cpath%20d%3D%22M%20380%2078%20L%20380%20105.5%20L%20470%20105.5%20L%20470%20133%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%20fill%3D%22none%22%2F%3E%3Crect%20x%3D%22390%22%20y%3D%22133%22%20width%3D%22160%22%20height%3D%2258%22%20rx%3D%228%22%20fill%3D%22white%22%20stroke%3D%22%230891b2%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22470%22%20y%3D%22158%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EPossible%20%283P%29%3C%2Ftext%3E%3Ctext%20x%3D%22470%22%20y%3D%22176%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E10%25%20confidence%3C%2Ftext%3E%3Cpath%20d%3D%22M%20380%2078%20L%20380%20105.5%20L%20650%20105.5%20L%20650%20133%22%20stroke%3D%22%23cbd5e1%22%20stroke-width%3D%222%22%20fill%3D%22none%22%2F%3E%3Crect%20x%3D%22570%22%20y%3D%22133%22%20width%3D%22160%22%20height%3D%2258%22%20rx%3D%228%22%20fill%3D%22white%22%20stroke%3D%22%230891b2%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22650%22%20y%3D%22158%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EContingent%3C%2Ftext%3E%3Ctext%20x%3D%22650%22%20y%3D%22176%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3ENot%20yet%20economic%3C%2Ftext%3E%3C%2Fsvg%3E)

*SEC reserve classifications by probability of economic recoverability, from proved (90%) to possible (10%).*

**Proved (1P) Reserves**:
- 90% probability of being economically recoverable
- Must be producible under existing economic conditions
- Reported in 10-K filings, reviewed by independent engineers
- "PV-10" valuation of proved reserves is standard in E&P analysis

**Probable (2P) Reserves**:
- 50% probability of being recoverable
- Proved + Probable = 2P
- Used internally for planning but not disclosed under SEC rules

**Possible (3P) Reserves**:
- 10% probability of being recoverable
- Proved + Probable + Possible = 3P
- Highest upside case, lowest confidence

**Contingent Resources**:
- Discovered but not yet proven economically recoverable
- Development pending further appraisal or improved conditions

**Prospective Resources**:
- Undiscovered; estimated potential in exploration prospects
- Highest uncertainty

**Proved Developed vs. Proved Undeveloped (PUD)**:
- Proved Developed (PD): Producing or capable of production without additional CapEx
- Proved Undeveloped (PUD): Require additional capital to develop (drilling, completion)
- PUDs are economic at current prices but haven't been drilled yet

## Type Curves: Industry Standard Approach

Shale companies typically communicate EUR through **type curves** — representative production profiles for a specific basin and well design.

**Example type curve**:
- Location: Permian Basin, Midland sub-basin
- Lateral length: 10,000 feet
- Completion: 2,000 lbs/ft proppant
- Type curve EUR: 950,000 BOE
- Year 1 production: 260,000 BOE
- Payback: 18 months at $65/bbl

Investment decisions are made based on type curves — does this well design at this location and expected cost generate an acceptable return?

**Type curve variance**: Actual wells produce within a range around the type curve. The best wells (P10) may produce 1.5-2x the type curve; poor wells (P90) may produce 60-70% of the type curve.

## EUR Uncertainty and Revisions

EUR estimates change over time:

**Positive revisions**: 
- Improved drilling and completion technology increases recovery
- Longer production history validates higher decline curve parameters
- Commodity price increases push more reserves into economically recoverable

**Negative revisions**:
- Wells declining faster than projected
- Lower commodity prices make some reserves uneconomic
- Geological surprises

**SEC reserve revisions**: Companies must disclose reserve changes annually. Significant downward revisions (5%+ of reserves) are closely watched by analysts as quality indicators.

## PV-10 Valuation Using EUR

EUR flows into PV-10 (present value at 10% discount) valuation:

1. Project annual production from EUR using type curves
2. Apply SEC price deck (12-month [average price](/blog/average-price), pricing by basin)
3. Subtract operating costs, severance taxes, production taxes
4. Subtract forecasted CapEx to develop PUDs
5. Discount future net cash flows at 10%
6. Sum to PV-10

**Example**:
- EUR: 500,000 barrels over 20 years
- Annual production profile from decline curve
- Realized oil price: $65/bbl
- Lifting cost: $15/bbl
- Severance tax: 4.6%
- Total [operating margin](/blog/calculate-operating-margin): $47/bbl
- NPV at 10%: Calculated based on year-by-year production and costs
- PV-10 per well: Maybe $8-12 million depending on front-loading

Summed across a company's well inventory, PV-10 provides a valuation floor (though market typically trades at multiples of PV-10 for high-quality producers).

## Common EUR Mistakes

**1. Over-relying on short production history**: Early production is often strongest; extrapolating to long-term decline requires caution.

**2. Ignoring economic limit**: Wells eventually produce too little to cover lease operating expenses. The "economic limit" ends the production forecast.

**3. Straight-line decline on shale wells**: Shale declines are non-linear; using simple linear or exponential decline significantly misestimates tail production.

**4. Comparing EURs across technologies**: A well drilled in 2018 with modern completions may have 2x the EUR of a 2010 well in the same reservoir — technology matters enormously.

**5. Not accounting for parent-child well interference**: In shale, closely-spaced wells "communicate" and can reduce each other's EUR (parent-child degradation). Older analysis assumed wells were independent.

## EUR in Unconventional Resource Plays

**Permian Basin**: Top shale play, average well EUR 400,000 - 1,000,000 BOE depending on sub-basin and vintage. Premium operators (Pioneer, Diamondback, EOG) achieve upper range.

**Bakken**: Mature play, EURs typically 300,000 - 700,000 BOE. Older wells approaching depletion.

**Marcellus/Utica (Appalachia)**: Natural gas dominant. EUR expressed in Bcf — 5-20 Bcf per well common.

**Eagle Ford (Texas)**: Oil-rich, 400,000 - 800,000 BOE typical.

**Haynesville**: Deep dry gas shale, 15-30 Bcf per well.

## Authoritative Sources

For deeper background and primary-source data on this topic, the following authoritative sources are useful starting points:

- [IRS](https://www.irs.gov/)
- [SEC](https://www.sec.gov/)
- [Federal Reserve](https://www.federalreserve.gov/)

## Conclusion

Estimated Ultimate Recovery is the bedrock of oil and gas valuation — and one of the most consequential numbers in the industry. It determines whether a well is worth drilling, a field is worth developing, or a company is worth acquiring. EUR estimation combines geology (how much hydrocarbon is in place), engineering (how much can technology extract), and economics (at what price is it recoverable). The uncertainty around EUR — especially for unconventional shale wells with limited production history — is substantial, and investors should always consider the range of possible outcomes rather than a single point estimate.

For related financial analysis topics, see our guides on [net profits interest](/blog/net-profits-interest), [CAGR formula](/blog/cagr-formula), and [OpEx vs. CapEx](/blog/opex-vs-capex).

Warren at [heywarren.com](https://heywarren.com) helps investors evaluate E&P companies, reserves, and [free cash flow](/blog/cashflow-free) generation potential across oil and gas investments.

---


## Related Reading

**More from Warren**:

**Authoritative sources**:
- [SEC Investor.gov — Investing Basics](https://www.investor.gov/introduction-investing/investing-basics)
- [FINRA — Investor Education](https://www.finra.org/investors)