Produced Water Disposal In The Southern San Joaquin Basin: A Direct Analog For Brine Leakage In Response To Carbon Storage

Abstract

Injection of CO2 during geologic carbon storage pressurizes reservoir fluid, which can cause its migration. Migration of saline water from the reservoir into underground sources of drinking water (USDW) via pathways such as permeable wells and faults is one concern. As of 2010, 2 billion cubic meters (MMMm3) of oil, 10 MMMm3 of water, and 400 MMMm3 of gas had been produced in the southern San Joaquin Valley. A considerable portion of the gas and a majority of the water were injected into production zones for pressure support, water flooding, or as steam for thermal recovery. However a portion of the produced water was disposed of by injection into zones without economic quantities of hydrocarbons, termed saline aquifers in the geologic carbon storage community. These zones often lay above the producing zone and, in the absence of hydrocarbon production, were at their original pressures. The subset of such zones at CO2 storage depths received disposed water volumes equivalent to tens of megatons (MT) of CO2 injected at overpressures of many MPa. For instance, in the Fruitvale field, a water volume equivalent to over 20 metric tons (MT) of CO2 was injected at a depth of 900 m and an average wellhead pressure of 6 MPa. The Fruitvale field lies only one half mile east of downtown Bakersfield and many domestic water supply wells produce from the aquifer overlying the disposal zone in the area. Consequently the produced water disposal injection in the Fruitvale field provides an analog for assessing the occurrence of water leakage impacts due to reservoir pressurization. Almost 230 articles regarding groundwater contamination published from 2000 to 2013 by The Bakersfield Californian, the main newspaper in the area, were assessed. These were written by 71 authors including 38 staff writers. The articles covered 53 different types of facilities or activities that either contaminated groundwater or for which there was such a concern, and discussed 85 different geographic locations. They described groundwater contamination at hundreds of wells during and previous to the publication period. Contamination due to upward leakage caused by produced water disposal injection was not mentioned. This suggests the lack of reporting of groundwater impacts from leakage due to produced water disposal injection indicates no significant public impact, such as closure of numerous public supply wells, occurred during the article time period or for some years previous. This research continues with analysis of historic groundwater constituent data available from the California State Water Resources Control Board's Geotracker Groundwater Ambient Monitoring and Assessment database. This database contains TDS and other constituent results for 149 wells within or in the immediate vicinity of the Fruitvale oil field.

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015