Paper No. 95
Presentation Time: 8:30 AM


TYRRELL, J.P., Department of Geology, Washington & Lee University, 204 West Washington Street, Lexington, VA 24450, SAMUELS, R.M., Department of Geology, Washington and Lee University, 204 W West Washington Street, Lexington, VA 24450 and LOW, P.C., Department of Geology, Washington and Lee University, Science Addition, Lexington, VA 24450,

California has a large oil and natural gas industry with an expanding wastewater footprint. Although oil and gas production in CA has decreased since the mid-1980s, the volume of wastewater produced from its wells has risen substantially. Anticipated development of untapped reserves in the Monterey Shale has the potential to increase the volume of produced wastewater even further. Managing this wastewater appropriately is important to minimize the oil and gas industry’s environmental footprint.

Using data from over 80,000 wells reported by CA’s DOGGR, we determined trends in oil and gas production and wastewater disposal from 2002 to 2012. During this time, oil production in CA decreased 24% and natural gas production decreased 17%, while wastewater production increased 39%. The volumetric ratio of wastewater to oil produced has risen steadily from 9:1 in 2002 to 16:1 in 2012. Subsurface injection is the most common disposal method for produced wastewater and its use increased from 56% in 2002 to 63% in 2012. Disposal via unlined percolation ponds, the other major disposal method, decreased from 25% to 20%. Disposal via sewer systems, surface bodies of water, and evaporation with lined sump are minor factors and have not significantly changed. These trends are different from trends in Pennsylvania’s natural gas industry, where treatment at wastewater facilities is the primary method of wastewater processing.

Over the past decade, the volume of water produced per unit of oil and gas recovered has increased substantially in CA. Methods of wastewater disposal with lower potential for environmental impact, such as subsurface injection, are increasingly being utilized. This study shows an industry trend in CA toward using safer wastewater management practices. Nonetheless, a large portion of wastewater is still managed using techniques that pose a potential threat to groundwater, such as percolation. In addition, a significant portion of wastewater disposal remains unclassified by method. With expected increases in wastewater volume, it is vital for CA to have an effective regulatory structure that includes stricter disclosure requirements and incentives to reduce the volume of waste disposed via percolation ponds, which will decrease the environmental footprint of CA’s oil and gas industry.