a significant increase in our gathered volumes. In October, we exceeded 900,000 barrels per day on numerous days. The increase is a combination of volume growth from overall raw feed and additional ethane that is being recovered.

For the natural gas gather and processing segment, third quarter 2017 adjusted EBITDA increased 11% compared with the second quarter 2017. With the segment once again posting solid volume growth in the Williston Basin and STACK and SCOOP areas. In the Williston Basin, volumes processed again established new highs with an average of more than 840 million cubic feet per day during the quarter, despite planned maintenance at some of our processing facilities and the maintenance on Overland Pass Pipeline. Midcontinent volumes averaged more than 740 million cubic feet per day, and8% increase compared with the second quarter 2017.

Rigs remained steady across our acreage with approximately 30 rigs operating on our dedicated acreage in the Williston Basin and approximately 15 rigs on our dedicated acreage in the STACK and SCOOP areas combined. In the Williston Basin, we connected 130 wells during the third quarter for a total of 313 through the first nine months of the year, well on our way to completing our target of 400 in 2017.

We now estimate that drilled but uncompleted wells on our dedicated acreage increased to between 350-400, compared with 300 previously. We continue hearing of improved efficiencies across the basin, including indications of between 10-15% productivity improvements in wells completed in 2017 compared with 2016. At current rig activity levels, in addition