Carbon intensity (CI) of oil and gas production varies widely across global oil plays. Life cycle extraction from certain unconventional plays (e.g., tar sands) have the highest CIs but even many North American shale plays have high CI. Flaring and venting of associated or non-associated natural gas dramatically increases CI. This paper applies peer-reviewed processes across broad averages of shale activity in North America and compares them with CI in countries in the Asia Pacific region. Ways to lower the carbon intensity in both areas are discussed.

We perform well-to-refinery calculations of CI for major unconventional oil plays in North America and conventional plays in Asia Pacific. This approach accounts for emissions from exploration, drilling, production, processing, and transportation. The analysis tool is an open-source engineering-based model called Oil Production Greenhouse Gas Emissions Estimator (OPGEE). OPGEE makes estimates of emissions accounting using up to 50 parameters for each modeled field. This model was developed at Stanford University. Data sources include government sources, technical papers, satellite observations, and commercial databases.

Applied globally, OPGEE estimates show highest values in areas with extensive flaring of natural gas and very heavy crude oils - heavy oils require large energy inputs (e.g., steam flooding) and/or the use of light hydrocarbon diluents for transportation offset. A few other major areas included for reference. Examples illustrate how OPGEE can be used to evaluate the CI of public policy actions. A sensitivity analysis to flaring volumes illustrates these impacts, and further sensitivity analyses to pad drilling and improving well performance show CI impacts associated with hydraulic fracturing.

Unconventional production, especially from light tight oil is the most significant new source of fossil fuels in the last decade. Under a wide variety of carbon constraints, oil usage will continue for many decades and increase in the near term. Operators, governments, and regulators need to be able to avoid "locking in" development of suboptimal resources and instead provide incentives for shale operators to manage resources sustainably. This approach provides quantitative measures of such actions. Oil producers must prepare by eliminating development of marginal projects, elimination of flaring and venting, optimizing hydraulic fracture treatments, using improved recovery methods (e.g., enhanced oil recovery using anthropogenic CO2), reducing energy use, and eliminating unnecessary gas waste.

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