This is an independent model of the Extraction Oil and Gas January 2017 proposal of four pads with a total of 139 wells in Broomfield Colorado. In a May 15th proposal, Extraction reconfigured the 4 pads by moving some wells to a 5th pad. There might be enough detail to build a valid five pad model, but the four pad model was complete, debugged (I hope), and 90% documented, the total well count remained the same, and the recommendations and unknowns are still valid. A model including the reconfigured five pads, and the addition of a sixth pad with its additional wells should be built but not enough information exists at this time.
The study starts with an Environmental Protection Agency (EPA) report on drilling in the Niobrara formation with monthly additions from one average rig, the average time to drill a well, and a Colorado University (CU) study on natural gas well depletion. An assumption is made that fracking, and flowback of previously drilled wells are done in parallel with continual drilling. The result calculates production flows for 72 months (6 years).
The pressures, flows, pipe sizes, and safety setbacks needed to carry the gas to a gathering facility show setback limits. The average of four wells in Broomfield from a Colorado Oil & Gas Conservation Commission (COGCC) study lists the percent of each contaminant in the gas. A Colorado State University (CSU) study reports average losses, and the Colorado Department of Public Health & Environment (CDPHE) define losses limits for the Front Range. Another CSU study measures losses during drilling, fracking, and flowback. One year of local hourly surface weather data and upper air data define the weather inputs.
With the above information, the EPA AERMET (weather), and AERMOD (dispersion of contaminants) models were run. It produced a ream of data. The data were copied to a database and Google Maps is used to display them in a more comprehendible format. The study shows max hourly average losses in micrograms per cubic meter (ug/m^3), and parts per billion (ppb) at 500, 1000, 2500, and 5000 feet from each pad, and at the Prospect Ridge Academy from all four pads during drilling, fracking, flowback, and production for all the contaminants in the Occupational Safety and Health Administration's (OSHA) volatile organic compound (VOC) limits list. There is a large variation in concentrations by hours of the day and months of the year.
There is a page of recommendations and a page of unknowns. The web page: https://www.modelsw.com/OilGasMonitor/index.html contains a PowerPoint document on the study, a spreadsheet of the pressures, flows, and volumes, two spreadsheets on the losses and concentrations, and a 72 month model of the four pads on Google Maps. Losses can be adjusted and the list of contaminants can be selected on the model. You are welcome to copy and share any information on the site. Most of the papers that are referenced in the study have been copyrighted by the authors. I have not asked permission to link the studies.
Gerard Gilliland June 6, 2017