Texas groundwater conservation: oil and gas produced water discharge

The demand for water is continuing to increase as population and industry grow. The Natural Resources Defense Council indicated that Texas is at “extreme risk” for implementation of sustainable water management practices especially since groundwater is the supplier of a majority of the state’s fresh water. This study is designed to assess groundwater conservation practices in association with oil and gas production from the surrounding areas of the Carrizo-Wilcox formation in Texas. The results of this study reveal that the Railroad Commission of Texas (RRC), the governing agency for Texas oil and gas development, permits produced water to be discharged into surface waters if the discharged water quality meets Texas Surface Water Quality Standards (TSWQS) set by the Texas Commission on Environmental Quality (TCEQ) for the specific receiving water body. Additionally, based on the Clean Water Act regulated by the Environmental Protection Agency (EPA), each discharge point must submit a Whole Effluent Toxicity (WET) test as part of the EPA National Pollutant Effluent Discharge System (NPDES) permit. The term “produced water” signifies waters that are produced as a byproduct along with oil and gas. A majority of the produced water discharged amounts to having Total Suspended Solid (TDS) levels of less than 650 mg/L, although some discharges amount to 1,500 TDS (mg/L), based on TSWQS. The RRC is not legally required to share the discharge information with local Groundwater Conservation Districts. After careful evaluation of data provided by the Railroad Commission of Texas, it is believed that nearly 5,331,975 cubic meters (1,408 million gallons) of produced water per year is being removed from locations surrounding the Carrizo-Wilcox aquifer through discharge permits. This is not surprising since it was shown that approximately 10 barrels (1.2 cubic meters, 315 gallons) of water are produced with each barrel of crude oil in a standard oil producing well. It is important to note, however, that between 2004 and 2011, the San Antonio Water System (SAWS) and Bexar County aquifer recharge program has been injecting an average of 17,715,865 cubic meters (4,680 million gallons) of fresh water a year into the Carrizo-Wilcox Aquifer from the Edwards Aquifer through the Twin Oaks Recharge Facility. The system spends approximately $9.5 million dollars a year to maintain the Aquifer Storage and Recovery (ASR) program which is located in Bexar, Wilson, and Atascosa Counties, in proximity to many of the produced water discharge locations identified in this study. This could be causing several negative impacts, the most apparent of which would be contribution to aquifer over-exploitation and alteration of hydraulic gradients, in turn negatively impacting the storage efforts implemented by the SAWS program.