Unconventional natural gas — most notably that found in shale rock — is transforming the gas industry. It will be transformational for major international oil companies, too. But that won’t happen right away, according to an analysis by consultant Wood Mackenzie.

“Material reshaping of these companies’ portfolios — to the extent that some of these companies will become much more weighted to unconventional gas — will occur over a longer timeframe as the assets acquired in recent years become more mature and the majors are able to leverage their scale and capabilities in developing these positions,” Wood Mackenzie said in a recent report.

Among the eight majors in the Wood Mackenzie universe — Eni, Statoil ASA, Total SA, Chevron Corp., Royal Dutch Shell plc, BP plc, ExxonMobil Corp. and ConocoPhillips — natural gas accounts for about half of proved probable (2P) reserves; however, unconventional gas is typically less than 10% of reserves, the firm said.

“With the exception of Chevron, all of the majors have increased their production of unconventional gas between 2004 and 2010,” the firm said. “However, Chevron’s unconventional gas production will increase in the medium term following the acquisition of Atlas Energy [see Shale Daily, Nov. 10, 2010], a major player in the Marcellus Shale in the Northeast U.S.”

Overall, increases in unconventional gas production among the majors are less dramatic than the overall increase in unconventional production, Wood Mackenzie said. Unconventional production in North America grew by 15.5 Bcf/d between 2004 and 2010, “with some independent companies in the region enjoying annual production growth rates of over 15%,” the firm said.

“Even with large corporate acquisitions of key unconventional gas players in North America, ExxonMobil and ConocoPhillips still have less than 11% of their commercial 2P reserves in unconventional gas plays,” Wood Mackenzie said.

“…[A]s industry begins to evaluate unconventional plays internationally, the majors can expect to be well positioned to leverage their existing international expertise and established relationships.”