Production from the Bakken began in earnest in 2004, with the advent of multi-stage horizontal fracturing technology. Along the Canada-US border development has been underway in the Torquay formation in recent years, directly below the Bakken. Both of these zones continue to be targeted for oil production. The Bakken remains a lucrative formation, which is in part due to secondary recovery techniques, while the extent of the Torquay play is still being delineated by area operators. The oil in the Bakken and Torquay is trapped by a decrease in permeability which prevents the oil from continuing to migrate to the north.