Visit our interactive news application — "Shale Play: Natural Gas Drilling in Pennsylvania."

To create this news application, NPR StateImpact acquired lists from the Pennsylvania Department of Environmental Protection — the agency charged with permitting and regulating oil-and-gas drilling in the Keystone State.

The agency releases well data semi-annually, so the records in the application represent wells in the system from January 1, 2012 to June 30, 2012. Gas production totals and days represent activity during that period. The application also reflects violations reported from Jan. 1, 2009 to June 30, 2012 on any wells that were active during the first half of this year.

The app used to track only producing (or “active”) wells. Recently, however, after realizing that several of the wells that were being drilled were not visible in our map, we changed that to also include the  wells DEP had issued permits for, but that weren’t aren’t yet producing.

Finally, a reminder that 8,982 wells doesn’t mean there are 8,982 large drilling rigs dotting Pennsylvania. Energy companies drill multiple wells on each site.

The wells data are presented largely as released by the department, though we did omit a handful of duplicate records in which wells were assigned separate owners.

The violations data are presented as released by the department, so some violations appear as duplicates because two enforcement actions can be associated with one violation in the department’s relational database. The agency, however, releases a flat dump from the database, so these duplicates are unavoidable. Be careful if you plan to use the data for well counts or fine totals without first separating inspections, violations and enforcements into separate tables with distinct records.

Please let us know if you spot errors or have questions about the data.