# Conventional oil and gas production: Efficiency

Why most of the oil in a field is never recovered

Source page: https://www.materialinsights.org/energy/e_oil_gas_conv/efficiency/

What this tab covers How much of the energy available is actually captured or extracted, in per cent: theoretical limits, laboratory records, typical new equipment and in-service averages, each with exactly what is being measured.

For oil wells, efficiency means the recovery factor: the share of the oil in place that is ever brought to the surface. Natural pressure alone rarely recovers more than 20%; adding water or gas injection typically brings the total to 35-45%, and estimates of the world average range from 22% to 40%. The energy returned is typically 10 to 35 times the energy spent, falling as fields age.

Chart: Efficiency ranges
 In service Record Theoretical limit

#### Efficiency by measure

| Measure | Range | Type | What is measured |
|---|---|---|---|
| **Primary recovery (natural reservoir pressure)** | 20%^[1](https://www.spe.org/en/industry/increasing-hydrocarbon-recovery-factors/) | In service | Upper bound in most reservoirs: share of original oil in place produced by natural pressure and pumping |
| **Primary plus secondary recovery (water or gas injection)** | 35 to 45%^[1](https://www.spe.org/en/industry/increasing-hydrocarbon-recovery-factors/) | In service | Typical combined recovery of original oil in place after waterflooding or gas injection |
| **World average oil recovery factor** | 22 to 40%^[2](https://www.ogj.com/drilling-production/production-operations/ior-eor/article/17227761/global-oil-reserves-1-recovery-factors-leave-vast-target-for-eor-technologies)^[15](https://www.iea.org/commentaries/whatever-happened-to-enhanced-oil-recovery) | In service | Estimates differ by method: 22% (weighted by major provinces), 27-30% (field databases), 40% (USGS); the IEA says primary and secondary recovery typically leave about 70% in the ground |
| **Best regions and fields** | 46 to 66%^[2](https://www.ogj.com/drilling-production/production-operations/ior-eor/article/17227761/global-oil-reserves-1-recovery-factors-leave-vast-target-for-eor-technologies) | Record | North Sea average 46%; Statfjord field 66% without enhanced recovery |
| **Practical ceiling with pressure maintenance** | 45 to 50%^[2](https://www.ogj.com/drilling-production/production-operations/ior-eor/article/17227761/global-oil-reserves-1-recovery-factors-leave-vast-target-for-eor-technologies) | Theoretical limit | Theoretically up to 70%, but values above 60% are very rare |
| **Energy return on energy invested, oil and gas** | 11 to 35 ratio^[3](https://www2.mdpi.com/2071-1050/3/10/1796) | In service | US 11-18 (mid-2000s); global 26 (1992), 35 (1999), 18 (2006) |
| **Net energy return across 40 major oilfields** | 2 to 100 ratio^[4](https://doi.org/10.1371/journal.pone.0144141) | In service | MJ of crude produced per MJ of fuel consumed; lowest for thermally enhanced fields |

#### Where the energy is lost

| Step | Loss |
|---|---|
| **Oil trapped in small pores by capillary forces or bypassed by injected water** | typically 60-78% of oil in place stays underground (calculated from 22-40% recovery)^[2](https://www.ogj.com/drilling-production/production-operations/ior-eor/article/17227761/global-oil-reserves-1-recovery-factors-leave-vast-target-for-eor-technologies) |
| **Energy used to produce, process and transport oil liquids** | about 15.5% of gross energy output today, possibly half by 2050^[5](https://ideas.repec.org/a/eee/appene/v304y2021ics0306261921011673.html) |

Oil does not sit in underground lakes; it fills tiny pores in sandstone or limestone. When a well is drilled, pressure pushes some oil out, but as pressure falls the oil stops moving and much stays stuck to the rock. Injecting water or gas keeps pressure up and sweeps more oil towards the wells. Gas flows far more easily than oil, so gas fields usually recover a higher share.

Sources disagree on the world average because they weight fields differently and some count expected future recovery. Net energy is falling as easy fields deplete and more water must be lifted and reinjected per barrel.

#### Sources

1. [Increasing Hydrocarbon Recovery Factors (Zitha, Felder, Zornes, Brown and Mohanty)](https://www.spe.org/en/industry/increasing-hydrocarbon-recovery-factors/) Society of Petroleum Engineers, 2011
2. [Global Oil Reserves 1: Recovery factors leave vast target for EOR technologies (Sandrea and Sandrea), field-database review](https://www.ogj.com/drilling-production/production-operations/ior-eor/article/17227761/global-oil-reserves-1-recovery-factors-leave-vast-target-for-eor-technologies) Oil & Gas Journal, 2007
3. [A Review of the Past and Current State of EROI Data (Gupta and Hall, Sustainability 3(10))](https://www2.mdpi.com/2071-1050/3/10/1796) MDPI, 2011
4. [Energy Return on Investment (EROI) for Forty Global Oilfields Using a Detailed Engineering-Based Model of Oil Production (Brandt et al., PLoS ONE 10(12): e0144141)](https://doi.org/10.1371/journal.pone.0144141) PLoS ONE, 2015
5. [Peak oil and the low-carbon energy transition: A net-energy perspective (Delannoy et al., Applied Energy 304)](https://ideas.repec.org/a/eee/appene/v304y2021ics0306261921011673.html) Elsevier (via RePEc IDEAS), 2021
6. [Whatever happened to enhanced oil recovery?](https://www.iea.org/commentaries/whatever-happened-to-enhanced-oil-recovery) International Energy Agency, 2018

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_oil_gas_conv/index.md)
- [Overview](https://www.materialinsights.org/energy/e_oil_gas_conv/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_oil_gas_conv/correlation/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_oil_gas_conv/techniques/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_oil_gas_conv/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_oil_gas_conv/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_oil_gas_conv/links/index.md)