Energize Weekly, June 12, 2019
Horizontal wells accounted for 96 percent of the oil production from tight geological formations, such as shale, in 2018, up from 15 percent in 2004, according to data from the federal Energy Information Administration (EIA).
The horizontal wells, with laterals that can run two miles or more underground, also accounted for 97 percent of natural gas production in these formations in 2018, up from 14 percent in 2004.
“Although horizontal wells have been the dominant source of production from U.S. shale gas and tight oil plays since 2008 and 2010, respectively, the number of horizontal wells did not surpass the number of vertical wells drilled in these plays until 2017,” the EIA said.
There were about 88,000 vertical wells in tight oil and shale gas plays in the U.S. producing crude oil or natural gas at the end of 2018, but the volume produced by these wells was minor compared with the volume produced by horizontal wells.
The key to opening these tight formations was the combination of horizontal drilling and sequential hydrofracturing, or fracking, in which large volumes of water, chemicals and sand were pumped into the well under pressure to fracture the rock and release hydrocarbons. The sand acts as a proppant to keep the crack open.
“The lateral length of horizontal wells has also increased, allowing for more exposure to oil- and natural gas-producing rock from a single well,” the EIA said.
The output from horizontal wells compared to vertical wells varies by play. In the Permian Basin, straddling West Texas and New Mexico, vertical wells generated 96 percent of the crude oil in 2004, and in 2014, they still accounted for half the production. By 2018, however, vertical wells accounted for just 7 percent of production from these formations.
In the Marcellus formation in the Appalachian Basin, almost 99 percent of the production is the result of horizontal drilling. “While some of the first natural gas wells in the United States were drilled in the Marcellus, production shifted to more economic areas and only resumed upon the development of horizontal drilling and hydraulic fracturing techniques,” the EIA said.
