California Oil, Gas, and Groundwater Program
Publication: Conference and Public Meeting Abstracts or Presentations
California Senate Bill 4 of 2013 requires the California State Water Resources Control Board to implement a Regional Monitoring Program (RMP) to assess potential interactions between oil/gas well stimulation treatment and groundwater resources. The U.S. Geological Survey is collaborating with the Water Board to implement the California Oil, Gas, and Groundwater (COGG) RMP. The areas in which well-stimulation methods are used in California have long histories of oil and gas development. Consequently, the effects of well stimulation on groundwater resources will be difficult to distinguish from the effects of other past or present components of oil and gas development. As a result, the COGG-RMP is designed to provide an overall assessment of the effects of oil and gas development on groundwater quality. During 2015-17, the study will focus on selected priority oilfields in the eastern and western portions of the San Joaquin Valley in Kern County to: (1) produce three-dimensional (3D) salinity maps, (2) characterize the chemical composition of groundwater and produced water, and (3) identify the extent to which fluids from oil and gas development may be moving into protected groundwater zones at regional scales.
As part of statewide analysis done during 2014-15 to design the RMP, water and petroleum wellconstruction data were compiled and used in classifying the proximity of oil/gas and groundwater resources. Analysis of salinity data near oil/gas fields indicates there are regional patterns to salinity depth profiles; however, data gaps between the depths of groundwater and oil/gas wells are common. These results provide a foundation for more detailed oilfield-scale salinity mapping, which include geophysical methods (borehole, surface, and airborne) to fill data gaps.
The COGG-RMP sampling-well networks are designed to evaluate groundwater quality along transects from oil/gas fields into adjacent aquifers and will consist of existing wells supplemented by monitoring-well installation in priority locations identified by using 3D visualization of hydrogeologic data. The analytes will include constituents with different transport characteristics such as gases, dissolved inorganic components (brines), and dissolved petroleum compounds. Analytes were selected because of their potential usefulness for understanding processes and pathways for fluids from oilfield sources to reach groundwater.