Posts Tagged ‘carbon intensity’

An interesting study published in the Proceedings of the National Academy of Sciences (PNAS) was brought to my attention by leading offshore energy historian Tyler Priest. The study used airborne observations and emissions reports to measure the carbon intensity (CI) of Gulf of Mexico oil and gas production. Their CI measure is grams of CO2 equivalent of greenhouse gas emissions per megajoule of energy produced.

The authors conclude that inventory emissions of CO2 (as reported to BOEM) “are generally consistent with observations from our aircraft survey, suggesting that combustion is well represented in the federal inventory.

However, that is not the case for methane (CH4) emissions which are underestimated by the Federal inventories. As summarized in the chart below, deepwater facility methane emissions are consistent with the reported inventories, but shelf emissions in State and Federal waters differ significantly.


  • As previously discussed, the lower CI for deepwater production is entirely consistent with expectations. When the most modern 5% (57) of GoM platforms are producing 93% of the oil and 76% of the gas, their CI should be impressive (which indeed it is).
  • As summarized using ONRR data, more gas-well gas was vented from 2015-2021 than was flared, which is not what you want from a GHG standpoint. Gas wells are predominantly at shallow water facilities, many of which are not equipped with flare booms.
  • Oil-well gas, most of which is produced at deepwater platforms, is flared rather than vented by a ratio of approximately 4 to 1.
  • About 15 years ago, the Federal government (MMS) considered requiring that older production platforms be retrofitted with flare booms, but safety, space limitations, and cost considerations precluded such a regulation. Instead, additional flaring/venting limits, and measurement and reporting requirements were imposed.
  • One bad actor may have been a major contributor to the shelf methane emissions observed during the study’s observational flights. That company entered into bankruptcy proceedings. Presumably those issues have been resolved and more rigorous monitoring and enforcement practices have been implemented. I’ll be looking at the 2022 ONRR flaring and venting data for evidence of such improvement. The remainder of the 2022 data should be available in May.
  • The subject study’s only observational measurements were in August 2020. Followup airborne measurements would be helpful.
  • The study only considered production emissions. Shelf facilities are primarily natural gas producers and would thus have a lower relative CI when consumed.
  • When will updated BOEM GOADS flaring and venting data be available? The latest data are for 2017 (cover below)? Are GOADS data being compared with ONRR and World Bank data?

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With regard to air emissions, the advantages of deepwater Gulf of Mexico production are rather obvious:

  • High production rates per well
  • Few surface facilities (57 deepwater platforms, 3% of GoM total, produce 90+% of oil)
  • Modern gas turbines for power generation
  • Tightly enforced restrictions on flaring and venting
  • Better control of fugitive emissions
  • Distant from shore (not a factor for GHG effects)

Wood Mackenzie, NOIA, and others contend that restrictions on GoM leasing are contrary to carbon reduction goals.

An important and unintended consequence of enacting more restrictive policies such as a lease ban or increase in royalty rate in the Gulf of Mexico is that it could give rise to carbon leakage to countries that export crude to US.

Wood Mackenzie
Chart: Emissions intensity for US crude importers. US Gulf of Mexico deepwater emissions are less intensive than all but one importer.

In light of the policy implications of GHG emissions, a Carbon Intensity Workshop is highly recommended. The estimates generated by Wood Mackenzie, Rystad, and others need to be explored in depth. Is data quality an issue? How are the data verified? Is there regulator or third party oversight? What are the assumptions behind the estimates? Also, for the purposes of US policy decisions, product transportation emissions should certainly be included. A barrel produced in the Middle East is not the same as a barrel produced in the GoM.

Looking at the chart above, I have immediate questions about the drilling emissions (blue). What wells are included? What about workovers and other well operations? I’m surprised that the deepwater GoM drilling emissions are so high relative to the other regions. While dynamically positioned MODUs have high fuel consumption rates, deepwater wells are few in number relative to shale drilling. Also, why are Brazil’s drilling emissions, which I assume are primarily associated with deepwater operations, so much lower that those for the GoM.

BOEM/BSEE and/or the Gulf Research Program (NASEM) would seem to be good sponsors for such a workshop.

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A previous BOE post estimated that current stabilized GoM oil production rates were 1.7 – 1.8 million BOPD. EIA recently announced that May production was 1.791 million BOPD, which is consistent with our estimate. Per the chart below, GoM production was essentially unchanged from the beginning of the year despite a 37% increase in the price of oil (WTI) from 1 January to 31 May. This suggests that stabilized GoM production may have peaked pending first oil from several new projects.

Key production questions:

  • Will new production from Mad Dog 2, Vito, PowerNap, Thunder Horse South 2, and the recently sanctioned Whale project offset high depletion rates elsewhere in the deepwater GoM?
  • Looking further ahead, is deepwater GoM production sustainable without increased drilling activity? Per BSEE data, only 33 deepwater wells were started in 2021 YTD, just 18 of which are classified as exploratory. Drilling is thus at historic low levels. For reference, there were 477 wells started in 2001, 149 of which were exploratory. This level of activity facilitated a 30% growth in oil production, peaking at 2 million BOPD in 2019.

Regardless of one’s views on the urgency and timing of the “energy transition,” is there any doubt that oil and gas will continue to be important to our economy and security for years to come? If not, should deepwater GoM production, with its relatively low carbon intensity, be a core element of our energy strategy? To better understand the trade-offs, I suggest that BOEM’s Environmental Studies Program conduct a peer reviewed assessment of the carbon intensity of domestic and international supply alternatives. Product transportation considerations should be included in this assessment.

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