2026-10-07T17:17:04Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34037905 2026-10-01T03:07:09Z category_4 category_16 category_19 category_21 category_272 category_873 category_39 portal_63 item_type_6 month_year_10_2026

Quantifying Methane Emissions from Oil Fields in the Central Valley of CA Colin J. Finnegan (8713377) Zutao Ouyang (12004327) Ken Reichl (25150990) Andrew B. Moyes (7059194) Andre L. D. Santos (25150993) Javier Gonzalez-Rocha (25150996) Francesca Hopkins (10526437) Evan D. Sherwin (10796971) Sebastien C. Biraud (2910866) Robert B. Jackson (192911) Biochemistry Physiology Pharmacology Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology 8 × 10 47 repeat measurements 219 total observations emitted ∼ 100 also measured benzene california energy commission 9 mg h 26 kg h 01 kg h 6 </ sub 4 </ sub total methane emissions quantifying methane emissions 000 active wells gcs rose sharply methane emissions measured methane ∼ 50 ≥ 50 overwhelmingly dominated mean mass largest producer kern county increasing oil gas production ended line crude oil central valley casinghead gas capturing gas based ratio 2 barrels In 2024, California was the eighth-largest producer of crude oil in the U.S. by volume with ∼50,000 active wells. Working with the California Energy Commission, we measured methane (CH₄) emissions from 172 actively producing oil wells (219 total observations with 47 repeat measurements) either with or without casinghead gas collection systems (GCS) in two oil fields near Bakersfield in Kern County. We also measured benzene (C₆H₆) emissions at a subset of wells to assess C₆H₆ to CH₄ ratios. The mean mass-based ratio for C₆H₆:CH₄ was 7.8 × 10^–7 with a mean benzene emission rate of 0.9 mg h^–1. Wells with an open-ended line (OEL) emitted ∼100-fold more methane on average than wells with a GCS: 1.26 kg h^–1 and 0.01 kg h^–1, respectively. The prevalence of wells with a GCS rose sharply with increasing oil and gas production, rising from 36% for wells producing <2 barrels of oil equivalent per day (boed) to 97% for wells producing ≥15 boed. The top 5.7% highest-emitting wells were responsible for ≥50% of total methane emissions from casinghead gas. Methane emissions were overwhelmingly dominated by wells without a GCS, accounting for 98.5% of total casinghead gas emissions across both fields. Capturing gas from these wells would eliminate almost all of the methane emissions we detected. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/acsestair.6c00126.s001 https://figshare.com/articles/journal_contribution/Quantifying_Methane_Emissions_from_Oil_Fields_in_the_Central_Valley_of_CA/34037905 CC BY-NC 4.0