31 July 2020
Chart of the month
SWD operators could see potential time and cost savings by broadening their focus to include underutilized disposal zones that have available capacity.
This month, WiO is presenting two strategraphies rather than a chart. These images come from a webinar held earlier this month by oilfield water intelligence firm Sourcewater on the topic of produced water disposal in the Permian Basin. The first stratigraphy shows average permitted volumes for individual saltwater disposal wells (SWDs) by formation in 2018 and 2019, while the other depicts the target zones for new SWDs granted during the 2014-2018 period.
In some cases, SWD operators reach their maximum injection pressures before meeting permitted injection volumes. This is especially true at wells injecting into historically targeted formations where overpressurization is occurring, such as the San Andres. Overpressurization challenges are related to both the cumulative volumes that have been injected – for example, the San Andres is estimated to contain more than 325 million bbls of reinjected water, accounting for around 27% of total volumes disposed in the Permian Basin – as well as the fact that many popular disposal intervals are also hydrocarbons-producing. As unconventional development has increased and moved across the basin over the past decade, so too have localized pressure trends, due to the impact of simultaneous hydraulic fracturing and disposal activities.
The second stratigraphy suggests that even though many options exist for new SWDs, several historically popular injection zones continue to be favored, even in formations that have been associated with issues like overpressurization. This may be because the geology and behaviors of those formations are better understood, as well as because SWD operators tend to follow their counterparts in terms of the zones they target. For example, as pressures have crept up in the shallower San Andres, causing operational problems, many SWDs have trended towards the same deep formations, such as the Ellenburger. Operators have not shown much willingness to explore the many underutilized formations that exist, even though they may be ideal for avoiding higher-cost drilling or risks associated with overpressurization, seismicity or protests in certain locations.