Modeling and Analyzing SCP Data in the Wattenberg Field: Lessons Learned and Best Practices

Investigations of stray gas contamination in the Wattenberg Field of Colorado have revealed multiple incidents where faulty oil and gas wells were the pathway for gas migration. Since 2010, the Colorado Oil and Gas Conservation Commission has required operators to submit well integrity tests in the region. These tests, known locally as bradenhead tests, evaluate the outermost annulus of the well for sustained casing pressure (SCP). We collected SCP and well construction data for 3,923 wells in the Wattenberg Field. These data informed two studies: 1) a data analysis study focused on building a framework for identifying high-risk wells and 2) a numerical modeling study in which we simulate SCP buildup behavior. Analytical results demonstrated the value of regional-scale SCP testing. The greatest risk for gas migration was exhibited by wells with short surface casings and a level of SCP greater than the formation fluid pressure at the surface casing bottom. Our modeling results illustrated the relationship between SCP buildup and gas migration. The models can be used to constrain gas fluxes into and out of the annulus and also show the impact of different well construction practices on SCP buildup behavior. In this presentation, we synthesize the findings of these studies to highlight well construction, SCP testing, and SCP management best practices for gas migration prevention. Specifically, we emphasize the need for more frequent, standardized, and comprehensive SCP testing.