Conventional oil and gas production: Efficiency

Why most of the oil in a field is never recovered

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	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	In service	Typical combined recovery of original oil in place after waterflooding or gas injection
World average oil recovery factor	22 to 40%²¹⁵	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	Record	North Sea average 46%; Statfjord field 66% without enhanced recovery
Practical ceiling with pressure maintenance	45 to 50%²	Theoretical limit	Theoretically up to 70%, but values above 60% are very rare
Energy return on energy invested, oil and gas	11 to 35 ratio³	In service	US 11-18 (mid-2000s); global 26 (1992), 35 (1999), 18 (2006)
Net energy return across 40 major oilfields	2 to 100 ratio⁴	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
Energy used to produce, process and transport oil liquids	about 15.5% of gross energy output today, possibly half by 2050⁵

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

Increasing Hydrocarbon Recovery Factors (Zitha, Felder, Zornes, Brown and Mohanty) Society of Petroleum Engineers, 2011
Global Oil Reserves 1: Recovery factors leave vast target for EOR technologies (Sandrea and Sandrea), field-database review Oil & Gas Journal, 2007
A Review of the Past and Current State of EROI Data (Gupta and Hall, Sustainability 3(10)) MDPI, 2011
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) PLoS ONE, 2015
Peak oil and the low-carbon energy transition: A net-energy perspective (Delannoy et al., Applied Energy 304) Elsevier (via RePEc IDEAS), 2021
Whatever happened to enhanced oil recovery? International Energy Agency, 2018