Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA

Journal of Hydrology: Regional Studies (Elsevier) | April 11th, 2022

Study region: Santa Barbara County, California, USA. Study focus: To analyze a wide array of newly collected chemical, isotopic, dissolved gas, and age dating tracers

Study region: Santa Barbara County, California, USA. Study focus: To analyze a wide array of newly collected chemical, isotopic, dissolved gas, and age dating tracers in conjunction with historical data from groundwater and oil wells to determine if water and/or thermogenic gas from oil-bearing formations have mixed with groundwater in the Orcutt Oil Field and surrounding area. New hydrological insights for the region: Three of 15 groundwater samples had compositions indicating potential mixing with water and/or thermogenic gas from oil-bearing formations. Relevant indicators included salinity tracers (TDS, Cl, Br), NH3, DOC, enriched δ13C-DIC, δ2H- CH4, δ13C-CH4, and δ13C-C2H6 values, and trace amounts of C3-C5 gas. The potential sources/ pathways for oil-bearing formation water and/or thermogenic gas in groundwater overlying and adjacent to the Orcutt Oil Field include: (1) upward movement from formations developed for oil production due to: (a) natural migration; or (b) anthropogenic activity such as injection and/or movement along wellbores; and (2) oil and gas shows in overlying non-producing oil-bearing formations. Groundwater age tracers, elevated 4He concentrations, and isotopic compositions of noble gases indicated legacy produced water ponds were not a source. This phase of the study relied on samples and data from existing infrastructure. Additional data on potential end-member compositions from new and existing wells and assessments of potential vertical head gradients and pathways between oil and groundwater zones may yield additional insight.

Oil, Food, and Water: Challenges and Opportunities for California Agriculture

Pacific Institute | December 1st, 2015

A new comprehensive study by the Pacific Institute  sheds light on the risks posed when oil and gas exploration and production operate alongside agriculture. “There

A new comprehensive study by the Pacific Institute  sheds light on the risks posed when oil and gas exploration and production operate alongside agriculture. “There is growing concern about competition for land and water, and the impacts of soil and water contamination on the food supply and health and safety of farmworkers and consumers,” said Matthew Heberger, the study’s lead author. The disposal of oil and gas wastewater, which contains harmful chemicals, is a particular concern for agriculture. Disposal in unlined percolation pits poses a significant risk of contaminating groundwater resources that may, in turn, be used by agriculture. While this practice has been banned in several states, it is still widely used in California’s Central Valley, one of the nation’s most important agricultural regions. There are also serious deficiencies in the way California regulates the underground injection of wastes – current practices are not sufficiently protective of freshwater aquifers that may be used as drinking water or to irrigate crops and water livestock.

Origin of methane and sources of high concentrations in Los Angeles groundwater

American Geophysical Union (AGU) | February 12th, 2018

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified as microbial activity rather than from the burial and heating of organic material. The source of the methane was microbial production in shallow, oxygen-depleted aquifers rather than the upward migration or leakage of methane associated with oil fields in the basin.

Pesticides in the Nation’s Streams and Ground Water, 1992–2001

U.S. Geological Survey (USGS) | February 28th, 2006

This report is one of a series of publications, The Quality of Our Nation’s Waters, that describe major findings of the NAWQA Program on water-quality issues of regiona

This report is one of a series of publications, The Quality of Our Nation’s Waters, that describe major findings of the NAWQA Program on water-quality issues of regional and national concern. This report presents evaluations of pesticides in streams and ground water based on findings for the first decadal cycle of NAWQA. “Pesticides in the Nation’s Streams and Ground Water, 1992–2001” greatly expands the analysis of pesticides presented in “Nutrients and Pesticides,” which was the first report in the series and was based on early results from 1992 to 1995. About 1 billion pounds of conventional pesticides are used each year in the United States to control weeds, insects, and other pests. The use of pesticides has resulted in a range of benefits, including increased food production and reduction of insect-borne disease, but also raises questions about possible adverse effects on the environment, including water quality. The NAWQA assessment of pesticides provides the most comprehensive national-scale analysis to date of pesticide occurrence and concentrations in streams and ground water. NAWQA results show where, when, and why specific pesticides occur in streams and ground water across the Nation, and yield science-based implications for assessing and managing the quality of our water resources.

Policy Considerations for Managing Agricultural Nitrogen to Reduce Groundwater Contamination in California

California Roundtable on Agriculture and the Environment (CRAE) | May 28th, 2013

Recent research, including “The California Nitrogen Assessment”1 and the UC Davis Report for the SWRCB SBX2 1 Report to the Legislature2, has produced an important co

Recent research, including “The California Nitrogen Assessment”1 and the UC Davis Report for the SWRCB SBX2 1 Report to the Legislature2, has produced an important collection of data about how nitrogen compounds move in the environment. Members of the California Roundtable on Agriculture and the Environment (CRAE) share an interest in meaningfully addressing water quality challenges while maintaining a healthy and prosperous agriculture sector. Because of the serious health concerns associated with nitrate in groundwater, CRAE members agree that the immediate goal should be to find cost-effective solutions to cleaning up drinking water supplies or providing safe alternate sources of drinking water to affected communities. We support ongoing efforts, such as the governor’s Drinking Water Task Force, to address this important issue. While CRAE’s ultimate interest is in addressing the full range of water quality challenges related to agriculture—from drinking water to legacy issues, groundwater to surface water, and nitrate to Total Maximum Daily Loads (TMDLs)—and supporting improved nutrient management broadly speaking, the group has chosen to focus specifically on the longer-term challenge of reducing nitrate loading in groundwater from agricultural sources. Recognizing that a range of research and policy processes to address the harmful impacts of excess reactive nitrogen-based compounds in the environment are ongoing, CRAE stakeholders agreed that a focus on preventing further contamination of groundwater from nitrate is an area where CRAE has a unique opportunity to contribute. Furthermore, we anticipate that approaches to reduce nitrate loading that adhere to the considerations below will simultaneously improve other challenges, including air quality, energy use, and climate change. Nitrate contamination is projected to increase in the coming years as legacy contributions work their way through the soil profile. The short-term remediation of groundwater basins is so costly as to be practically impossible. Therefore, CRAE has concentrated on intermediate and longer-term groundwater quality issues by helping to find practical solutions to groundwater quality challenges. Reflecting our membership composition, our focus is on the contribution of agricultural sources of nitrate in particular. CRAE has compiled the following set of key facts on our state of knowledge about nitrogen management and a set of considerations to inform related policy and programs focused on improving water quality.

Pollution Prevention (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

Pollution prevention can be defined as the reducing or eliminating of waste at the source by modifying production processes, promoting the use of non-toxic or less toxic

Pollution prevention can be defined as the reducing or eliminating of waste at the source by modifying production processes, promoting the use of non-toxic or less toxic substances, the implementation of practices or conservation techniques including activities that reduce the generation and/or discharge of the pollutants, and the application of innovative and alternative technologies which prevent pollutants from entering the environment prior to treatment. These preventive activities can also include new equipment designs or technology, reformulation or redesign of products, substitution of raw materials, updating or improvements of existing management practices, continued maintenance of previously implemented management practices, training and education/outreach, and improved collaboration. Pollution prevention begins at the source. Sources of water quality pollution can be categorized into two types: point-source and non-point-source. In California, point-source pollution prevention is addressed through the Clean Water Enforcement and Pollution Prevention Act of 1999, Water Code Section 13263.3(d)(1), which authorizes the State Water Resources Control Board (SWRCB), a regional water quality control board (RWQCB), or a publicly owned treatment works (POTW) to require a discharger to prepare and implement a pollution prevention plan. A point-source discharger is defined per Water Code Section 13263.3(c) as any entity required to obtain National Pollutant Discharge Elimination System (NPDES) permit or any entity subject to the federal pretreatment program. A non-point discharger is any discharger not covered by a NPDES permit. Pollution prevention can contribute to the protection of water quality for beneficial uses by protecting water at its source and therefore may reduce the need and cost for other water management and treatment options. By preventing pollution, restoring, and then protecting improved water quality throughout a watershed, water supplies can be used and reused by a greater number and types of downstream water uses. Protecting water quality through appropriate pollution prevention is consistent with a watershed management approach to water resources problems.

Potential Impacts of Future Geological Storage of CO2 on the Groundwater Reservoirs in California's Central Valley

California Energy Commission (CEC) | May 1st, 2013

This study assessed the history of oil production and pressure changes in the southern portion of the San Joaquin Basin in California’s Central Valley as a reverse anal

This study assessed the history of oil production and pressure changes in the southern portion of the San Joaquin Basin in California’s Central Valley as a reverse analog for understanding the pressure response to potential geologic carbon sequestration. Sequestration involves injecting carbon dioxide into permeable strata such as those that trap oil. This results in pressure increases in the existing fluid in the subsurface that can provide a motive force for brines at those depths to migrate into groundwater, affecting its quality. The pressure can also cause differential ground surface uplift that can affect surface water flow, particularly in engineered water conveyances such as canals. The strata underlying the Central Valley have been assessed as having considerable capacity to store carbon dioxide, but the area also contains urban areas and extensive agriculture that rely on engineered surface water delivery systems and groundwater supplies. The Stevens Sand, Temblor Formation and Vedder Formation were identified as having the largest cumulative net production from typical geologic carbon sequestration depths. Two oil pools were identified in each of these stratigraphic units for more detailed analysis, which included converting fluid level data to pressure at the pool scale. Data were collected that allowed an assessment of the hydraulic connectivity of each unit. The results indicated that the Vedder was hydraulically connected at the near basin scale, the Stevens was hydraulically connected at the pool scale and was disconnected between pools and the Temblor was disconnected within pools. Researchers used these results to analyze possible brine leakage driven by geologic carbon sequestration. They also reviewed over 200 articles on historic groundwater contamination. They concluded that no instance of contamination due to upward leakage of brine in the Central Valley was reported.

Predicting Redox Conditions in Groundwater at a National Scale Using Random Forest Classification

American Chemistry Society (ACS) | March 7th, 2024

Preliminary Results from Exploratory Sampling of Wells for the California Oil, Gas, and Groundwater Program, 2014–15

U.S. Geological Survey (USGS) | January 26th, 2017

In 2014 and 2015, the U.S. Geological Survey (USGS) sampled water wells in the Los Angeles Basin and southern San Joaquin Valley, California, and oil wells in the San Joa

In 2014 and 2015, the U.S. Geological Survey (USGS) sampled water wells in the Los Angeles Basin and southern San Joaquin Valley, California, and oil wells in the San Joaquin Valley for analysis of multiple chemical, isotopic, and groundwater-age tracers (fig. 1). The purpose of this reconnaissance sampling was to evaluate the utility of tracers for assessing the effects of oil and gas production activities on groundwater quality in California. The study was done in cooperation with the California State Water Resources Control Board. Results of the study are intended to help design a regional groundwater monitoring program to be implemented as part of California Senate Bill 4 (SB 4 statutes of 2013). The regional monitoring program plans to assess the effects of oil and gas production activities on groundwater quality and to provide a regional context for local monitoring of the groundwater-quality effects from well-stimulation treatments, which are techniques used to improve oil and gas production by increasing their rate of flow to the well. California SB 4 mandates that this local monitoring is to be done by oil-well operators in accordance with monitoring criteria established by the State Water Board. This report evaluates the utility of the chemical, isotopic, and groundwater-age tracers for assessing sources of salinity, methane, and petroleum hydrocarbons in groundwater overlying or near several California oil fields. Tracers of dissolved organic carbon in oil-field-formation water are also discussed. Tracer data for samples collected from 51 water wells and 4 oil wells are examined.

Proposed Health-Protective Concentration for the Noncancer Effects of Hexavalent Chromium in Drinking Water

California Environmental Protection Agency (CalEPA) | November 21st, 2023