The inclusion of unconventional shale gas with conventional gas reserves has caused a sharp increase in estimated recoverable natural gas in Canada. Until the 1990s success of hydraulic fracturing in the Barnett Shales of north Texas, shale gas was classed as "unconventional reserves" and was considered too expensive to recover. There are a number of prospective shale gas deposits in various stages of exploration and exploitation across the country, from British Columbia to Nova Scotia.