This dataset contains geochemical and other information for 340 samples of produced water from the Elk Hills Oil Field. Water that is produced as a byproduct of oil production is called produced water. The publicly available produced water chemistry data was compiled by USGS staff using historical DOGGR datasets and scanned images. The data were transferred manually into a numerical dataset and organized by specific produced water chemical characteristics. Each sample is identified by its API (American Petroleum Institute) number, latitude and longitude, well name, formation name, perforation interval, and date tested. The geochemical analyses include major ions, some minor ions, total dissolved solids (TDS), pH, specific gravity, resistivity, electrical conductivity, and charge balance.