This dataset consists of 119,494 lines of data consisting of idle well fluid level depth, auxiliary measurements, and well parameters from California oil and gas wells that were reported to the California Department of Conservation, Geologic Energy Management Division (CalGEM). The dataset was provided by CalGEM in March 2018 and includes measurements made from 1976 to 2018. There are 5 sets of operator-reported data: idle well fluid level depth (N=101,734), well clean out depth (N=8,402), depth of base of fresh water (N=108,216), well top perforation depth (N=93,569), and depth reached (N=15,756). These are associated with a well, defined by API number, well number, operator name, test date, township, section, range, and pool code. While detailed metadata for these measurements was not provided by CalGEM, they are thought to be collected under idle well testing regulations. Present regulations broadly define an idle well as one that has not been used for production or injection for 24 months or longer (California Code of Regulations, 2022, Title 14 §1760). Below, a summary of current regulations related to this program are presented; however, regulations at the time of data collection may be different. Once a well is classified as an idle well, a fluid level test using acoustical, mechanical, or other methods must be conducted within 24 months, and every 24 months beyond that, as long as a well is idle, unless the wellbore does not penetrate an underground source of drinking water (USDW) (California Code of Regulations, 2022, Title 14 §1772.1). Currently, within 8 years of a well becoming idle a clean out tag is required. This is done to demonstrate that the well can be properly plugged and abandoned. A clean out tag is done by passing open-ended tubing or a gauge ring of a minimum diameter equal to that of tubing necessary to plug and abandon a well (California Code of Regulations, 2022, Title 14 §1772.1). This testing must generally be repeated once every 48 months as long as a well is classified as an idle well. Freshwater is defined as water that contains 3,000 milligrams/liter (mg/L) or less of total dissolved solids (California Code of Regulations, 2022, Title 14 §1720.1). The base of freshwater is the depth in a well where the overlying water is freshwater. Neither top perforation depth or depth reached is defined by statute. Top perforation is generally the shallowest active perforated interval. It is not clear what depth reached represents. Well elevation and pool name were added from other datasets to aid in analysis. Pools, identified by pool code and pool name, are defined as independent hydrocarbon zones (California Public Resources Code § 3227.6.b). The accuracy of the values reported to CalGEM by oil-field operators is unknown. Unrealistic values were discarded from the data as noted in the process steps.
This dataset was compiled and analyzed as part of the California State Water Resources Control Board Oil and Gas Regional Monitoring Program and the U.S. Geological Survey California Oil, Gas, and Groundwater (COGG) program.