Marcellus gas wells can be drilled using 21st century vertical or horizontal technologies. Vertical wells are sometimes first drilled in an area to obtain information valuable for planning the drilling of more costly and technically demanding horizontal wells. Marcellus Shale natural gas wells in Pennsylvania are drilled horizontally because it offers access to a larger quantity of natural gas, while disturbing a smaller area on the surface. Both vertical and horizontal Marcellus Shale wells produce marketable quantities of natural gas.
The drilling process focuses first on reaching – and protecting – water-bearing zones beneath the ground. Drilling is completed using a small amount of lubricating agents, then the entire length of the well, from the surface to the groundwater strata, is cased and cemented tightly to form a barrier between the wellbore and the earth. As the drill continues to push deeper into the earth, a series of long drilling pipes follow it to establish the well. While drilling through the water barrier there may be short-term cloudiness or turbidity and diminishing of flow.
After drilling vertically to the depth that reaches slightly above the Marcellus Shale formation, the drill bit can then turn to push its way horizontally into the Marcellus Shale, sometimes as much as 5,000 feet, into the formation. This allows for the extraction of larger quantities of natural gas from a single wellhead. Marcellus Shale wells generally take between 15 and 30 days to drill, operating around the clock.