4.21 Oil Production Fields
Categories 48 and 1575
4.21.1 Introduction
Categories 48 and 1575 account for point and area source criteria pollutant emissions (NOx, CO, PM, PM10, PM2.5, ROG, SO2, TOG), respectively, from oil production fields in the San Francisco Bay Area. Emission sources associated with oil production include waste pits, well blowouts, gas/liquid separators, heater treaters, control valves, pressure relief valves, spills, pipe fittings, pump seals and compressor seals. During oil production, pollutants of concern are volatile organic compounds (VOCs), methane (CH4), hydrogen sulfide (H2S) and hazardous air pollutants (HAPs).
4.21.2 Methodology
Point Sources
Point Sources are operations that emit air pollution into the atmosphere at a fixed location within a facility, for which the Air District has issued a permit to operate, e.g., refinery cooling towers. These could also be a collection of similar equipment / sources located across multiple facilities, e.g., reciprocating engines.
During the permit to operate (PTO) issuance process, the BAAQMD collects information from the operating facility and/or determines from published literature, e.g., EPA’s AP-42, characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. These characteristics are then stored for future use in the BAAQMD’s internal database. Facilities that hold a permit to operate are required to renew this permit periodically (this period varies based on facility and source type). Upon renewal, the facilities are requested to provide any updates to source characteristics as well as the source throughput for the last 12 months. This throughput, in combination with the emission factors and controls factors stored in the internal database, are used to estimate annual emissions at the source level. These source level emissions are then sorted and aggregated into categories.
Further speciation and quality assurance of emissions are performed as a part of the inventory process. The last part of the inventory development process includes forecasting and back casting, and aggregation into sub-sectors and sectors for documentation purposes. For those years where no data is available, emissions data are backcasted to year-1990, as well as forecasted to year-2040 using either interpolation or another mathematical approach (see Trends section). Finally, emissions trends spanning from year 1990-2040 for each category and pollutant are evaluated for anomalies that are then investigated and addressed.
Category 48 is considered a point source category and follows the above methodology for emissions estimates.
The Air District adopted Rule 8, Regulation 37 on March 20, 1985, to control emissions at crude oil and natural gas production facilities. This rule has a control of 80% on reactive organic compounds, with a rule effectiveness of 90% reached by 1989. However, based on emissions data, the overall control efficiency is estimated at 92%.
Area Sources
For certain categories in the base year inventory, emissions data are derived by inventory staff of the state’s chief air quality regulatory agency, the California Air Resources Board (CARB). This significant emissions dataset, sorted by county, is published every few years and is a product of the State Implementation Plan (SIP) emissions document formally known as the California Emissions Projection Analysis Model (CEPAM) inventory110. For related sets of categories, such as airport ground support equipment (GSE), ships, structures coatings etc., where independent data collection and derivation of emissions are both cost- and time-prohibitive and likely a redundant effort, BAAQMD staff export the emissions data directly from CEPAM into the District’s Base Year inventory package. This calculation approach and collection of categories is internally termed as “CARB Source Categories”.
The CEPAM provides historical emissions as well as forecasts emissions for major emission source classifications including –
on-road mobile sources [from Emissions Factor (EMFAC) model],
off-road mobile sources (OFFROAD model), and,
stationary and area-wide sources - For these major source classifications, CEPAM combines facility level /area source emissions data reported to the California Emissions Inventory Development and Reporting System (CEIDARS) for multiple years by various regional air quality agencies (including the BAAQMD).
This inventory uses the 2016 CEPAMv1.051 to estimate emissions for “CARB Source Categories”. This version of the CEPAM derives emissions from a 2012 base year inventory and contains backcasts and forecasts from year-2000 to year-2035. All applicable regulatory and technological controls are assumed to be built into the CEPAM data set during CARB staff’s inventory computation work. After the emissions data are exported, the inventory for CARB Source categories is taken through a quality assurance (QA) process.
Area source Category 1575 is designated as a CARB Source Category. Therefore, activity or throughput and emissions information is obtained from the California Air Resources Board (CARB) as noted above.
4.21.3 Changes in Methodology
There are no changes to methodology for Category 48 in this version of the base year emissions inventory.
Category 1575 for this base year follows the methodology used for CARB Source categories.
4.21.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
4.21.5 Trends
According to the California Energy Commission, future California oil production, although uncertain, is expected to decline at a small annual rate during the next 20 years. According to the California Department of Conservation; Oil, Gas, and Geothermal Statistics and Production111 future oil production in the Bay Area could increase despite the decrease in number of operating oil wells.
Statistical extrapolation from historical data produces a very broad range, varying between a 7 percent decline to 1 percent increase. California oil production is responsive to prevailing oil prices. If economically feasible, enhanced oil recovery techniques can be used to extract oil from fields that have been nearly depleted using conventional methods.
(a) Historical Emissions / History
Since late 1980s, California oil production has been declining. Oil production in the nine Bay Area counties peaked in the mid-1980s and has dropped steadily since. The number of producing oil wells in the nine bay counties has dropped from 87 in 1986 to about 40 in 2000s. Historical emissions for these categories have varied with oil production activity in the Bay Area.
Historical emissions for point source emissions ( category 48) are derived from source-specific throughputs provided by the permitted facility, compiled/reported emission factors, and regulation-based control factors. This information is archived in the BAAQMD’s internal database which is queried to retrieve the data for historical and current years. Interpolation techniques to account for missing data are used when necessary, this is the case for years 1991-1992.
For category 1575, due to small emissions contribution from this category, CARB staff had suggested just doing a linear extrapolation from available CEPAM data for year 2000 back to year 1990 by ignoring the production data. However, the Air District staff disagreed with the CARB backcasting approach since oil and gas historical production data for the Bay Area is available and the production data shows that activity varied non-linearly during that period. Therefore, emissions from 1990 to 1999 were backcasted based on the gas production data from the California’s Department of Conservation-Division of Oil, Gas, and Geothermal Resources (DOGGR) for category 1575.
(b) Future Projections / Growth
In general, future Bay Area oil production, although uncertain, is expected to decline at a small annual rate.
Forecasting of category 48 is done based on calculations as shown in the equation below using recently updated growth profiles and a base year of 2020. The growth profiles for BY2015 inventory have been verified and updated to represent the most likely surrogate for growing emissions for a given category up to year 2040. Forecasting for point source emissions includes impact of in-place regulations, but does not include estimation of controls that will theoretically be implemented as part of future policy emission targets or proposed regulation and legislation.
\[ \text{PE} = \text{Gr} * \text{Ci} * \text{Ei} \]
\(PE\) = projected emissions of pollutant i in a future year
\(Gr\) = growth rate by economic profile of industry or population
\(Ci\) = control factor of pollutant i based on adopted rules and regulations
\(Ei\) = base year emissions of pollutant i
Since future emissions from 2036 to 2040 are not available in the CEPAM data set, emissions forecasting for category 1575 was done by holding 2035 emissions constant for years 2036 to 2040.
4.21.6 Uncertainties
Uncertainties in oil prices and production levels may lead to inaccuracies in emission growth projections development.
4.21.7 Contact
Author: Sukarn Claire
Reviewer: Ariana Husain
Last Update: November 06, 2023
4.21.8 References & Footnotes
The California Emissions Projection Analysis Model (CEPAM). 2016 SIP - Standard Emission Tool. https://www.arb.ca.gov/app/emsinv/fcemssumcat/fcemssumcat2016.php↩︎
The California Department of Conservation. Oil, Gas, and Geothermal Statistics and Production. https://www.conservation.ca.gov/calgem/pubs_stats/Pages/stats_prod.aspx↩︎