Chemical and Isotopic Testing as Part of Colorado’s Unique Approach to Monitoring Oil and Gas Development – What Have We Learned?

Environmental Forensics
Oral Presentation

Prepared by P. Travers
Environmental Standards, PO Box 460262, Denver, CO, 80246, United States


Contact Information: [email protected]; 970.231.0320

ABSTRACT

Colorado presents a unique opportunity to investigate the use of widespread chemical and isotopic sample data in monitoring oil and gas development, particularly near populated areas as the state’s population and oil and gas production have both grown significantly in the last decade. Regulations in Colorado have required limited baseline groundwater sampling and analysis both before and after drilling and hydraulically fracturing new oil and gas wells since 2005, though there has been a significant evolution of the regulations in recent years. Unique to Colorado, sampling and chemical and isotopic analyses are now required statewide as part of Colorado’s baseline groundwater monitoring regulations, as well as during annual wellbore integrity testing. The rationale behind selecting these analyses will be examined, along with their utility in creating a geochemical “fingerprint” that can provide insight into the source of unknown fluids.

As a result of these regulations, there are now tens of thousands of sample results in a publicly available Colorado Oil and Gas Conservation Commission (COGCC) database. Chemical and isotopic data from Colorado’s Wattenberg Field, one of the largest oil and gas fields in the country that has been developed since the 1970’s with vertical wells and more recently with horizontal drilling and high-volume hydraulic fracturing, will be presented as a case study. The collection of these data has allowed regulators and oil and gas operators to clearly differentiate between microbially sourced methane and deeper sourced thermogenic natural gas, identify stray gas occurrences, and efficiently guide remediation. These data also provide information on the source of fluids found in the annuli of existing wells, which can be a useful indicator of an oil and gas well’s casing and cement integrity. The utility of these analyses in Colorado is extensive and may serve as a model for other states in the future.