Unconventional oil and gas: Efficiency

Why fracking leaves over 90% of shale oil underground

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.

Unconventional methods extract oil and gas that will not flow on its own, and their recovery factors span the widest range of any fuel: under 10% of the oil in shale, 15-30% of shale gas, 40-60% of bitumen with steam and over 90% of bitumen in mined ore. Energy returns range from about 3 for oil sands at the point of use to around 85 for Marcellus shale gas.

Chart: Efficiency ranges

In service Commercial

Efficiency by measure

Measure	Range	Type	What is measured
Shale (tight) oil primary recovery	3 to 10%¹²³	In service	Share of oil in place recovered by fractured horizontal wells; EIA/ARI assessments used 3-7%
Shale gas recovery	15 to 30%²³¹	In service	Share of gas in place assumed recoverable from shale formations (EIA/ARI world assessment); a separate review gives 15-25% for tight formations
Gas-injection enhanced oil recovery, added to waterflooding	10 to 15 percentage points²	In service	Extra share of original oil in place recovered; miscible gas floods can in theory push total recovery above 50%
Oil sands SAGD (steam-assisted gravity drainage)	40 to 60%³	In service	Average recovery of bitumen in place in developed areas
Oil sands surface mining, extraction plant	90%³	Commercial	Bitumen recovered from ore fed to the plant (regulatory minimum for ore above 11% bitumen); achieved values are higher
Energy return, oil sands	3 to 6 ratio⁴	In service	About 6 GJ out per GJ in at the mine mouth, about 3 at point of use (2010)
Energy return, Marcellus shale gas	64 to 112 ratio⁵	In service	Mean about 85, assuming 3.0 billion cubic feet ultimate recovery per well

Where the energy is lost

Step	Loss
Oil left in nano-scale shale pores between fractures	over 90% of oil in place (calculated from recovery under 10%)¹
Natural gas burned to raise steam for in situ bitumen and thermal EOR	thermally enhanced recovery gives the lowest energy returns of the 40 fields studied⁶

Shale rock is so tight that oil and gas move only where fractures have been created, so most of the resource stays in place even after expensive fracturing. Gas, being lighter and more mobile, recovers several times better than oil. Bitumen in oil sands is too thick to flow at all; it must be dug up or heated with steam, which costs a large share of the energy produced.

Energy return figures are not strictly comparable: some stop at the wellhead or mine mouth, others include upgrading and transport. In one simulation, 20 years of gas injection in shale (huff-and-puff) recovered 16.69% of the oil against 5.75% for 10 years of primary production; field use is still limited.

Sources

Technology 101: EOR methods for shale and tight formations Journal of Petroleum Technology (SPE), 2016
Increasing Hydrocarbon Recovery Factors (Zitha, Felder, Zornes, Brown and Mohanty) Society of Petroleum Engineers, 2011
Alberta's Surface Mineable Oil Sands Projects: Recovery Factors That Are Far From Conventional (Freeborn, GLJ) BOE Report, 2016
Energy efficiency of oil sands extraction: Energy return ratios from 1970 to 2010 (Brandt, Englander and Bharadwaj, Energy 55: 693-702, doi:10.1016/j.energy.2013.03.080) Stanford Environmental Assessment and Optimization Group, 2013
Net Energy Analysis of Gas Production from the Marcellus Shale (Aucott and Melillo, Journal of Industrial Ecology 17(5)) RePEc IDEAS, 2013
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
EIA/ARI World Shale Gas and Shale Oil Resource Assessment (Kuuskraa, EIA Energy Conference presentation) US Energy Information Administration / Advanced Resources International, 2013