WASTEWATER DISPOSAL AND WATERFLOOD INJECTION VOLUMES IN CALIFORNIA

For decades, wastewater disposal and waterflood injection has occurred in California. It is not clear whether these injected fluids have been migrating into federally-protected (<10,000 ppm TDS) groundwater aquifers. In an effort to understand possible migration pathways, we have begun studying archived oil and gas well records collected by the California Division of Oil, Gas, and Geothermal Resources (DOGGR).

As a first step, we compiled location, depth, and injection volumes for wastewater disposal and waterflood injection wells available from 1977 to present for all digitally-accessible wells in the state. Preliminary analysis of a select well field (Lost Hills) shows that the largest individual injection sites are wastewater disposal wells, while total injection volume for the well field is dominated by waterflood injection.

As our next step, we are working with a large number of undergraduate researchers at CSU Sacramento and CSU Long Beach to identify key well records that that can be used to develop salinity maps and framework models for selected well fields. Geophysical well logs, including those measuring resistivity and porosity, are being used to develop three-dimensional maps of the distribution of of protected groundwater. Driller’s logs are also being used to construct three-dimensional texture models, which will then be used in a hydrogeological models.

This project is part of the broader effort of the California State Water Resources Control Board to implement Senate Bill 4.