Climate impacts of oil extraction increase significantly with oilfield age


Record-breaking temperatures1 have induced governments to implement targets for reducing future greenhouse gas (GHG) emissions2,3. Use of oil products contributes 35% of global GHG emissions4, and the oil industry itself consumes 3–4% of global primary energy. Because oil resources are becoming increasingly heterogeneous, requiring different extraction and processing methods, GHG studies should evaluate oil sources using detailed project-specific data5. Unfortunately, prior oil-sector GHG analysis has largely neglected the fact that the energy intensity of producing oil can change significantly over the life of a particular oil project. Here we use decades-long time-series data from twenty-five globally significant oil fields (>1 billion barrels ultimate recovery) to model GHG emissions from oil production as a function of time. We find that volumetric oil production declines with depletion, but this depletion is accompanied by significant growth—in some cases over tenfold—in per-MJ GHG emissions. Depletion requires increased energy expenditures in drilling, oil recovery, and oil processing. Using probabilistic simulation, we derive a relationship for estimating GHG increases over time, showing an expected doubling in average emissions over 25 years. These trends have implications for long-term emissions and climate modelling, as well as for climate policy.

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Figure 1: Oil fields data quality assessment.
Figure 2: Time-series trends in normalized upstream GHG intensities of twenty-five global oil fields (offshore and onshore) with different extraction practices (water injection/flooding, gas injection/flooding/lifting, or steam flooding) over the course of production in the period of 1949–2015.
Figure 3: Effect of FOR on total LCA GHG intensities of two Canadian offshore oil fields (Hibernia and Terra Nova) over the course of production till 2015.
Figure 4: Probabilistic Monte Carlo GHG intensities dynamics of twenty global giant oilfields.
Figure 5: Time-series normalized GHG intensities mean (μt) and standard deviation (σt) of lognormal distribution fitting data with fitted first-order polynomial trends.


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V. Tripathi provided historic data for five oilfields. The Natural Sciences and Engineering Research Council of Canada (NSERC) and Ford Motor Company provided financial support to M.S.M.

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Both M.S.M. and A.R.B. were involved in data gathering, processing and analysis of different fields. The final results were integrated and produced by M.S.M. He also wrote the manuscript, and all authors contributed to revising the paper.

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Correspondence to Mohammad S. Masnadi.

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The authors declare no competing financial interests.

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Masnadi, M., Brandt, A. Climate impacts of oil extraction increase significantly with oilfield age. Nature Clim Change 7, 551–556 (2017).

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