since the early 2000s, advances in drilling and completion technology have made horizontal wellbores much more economical. horizontal wellbores allow far greater exposure to a formation than conventional vertical wellbores. this is particularly useful in shale formations which do not have sufficient permeability to produce economically with a vertical well. such wells, when drilled onshore, are now usually hydraulically fractured in a number of stages, especially in north america. the type of wellbore completion is used to determine how many times a formation is fractured, and at what locations along the horizontal section.