The potential for energy resources from unconventional sources will likely play an important role for three decades and require more than $2 trillion in capital to fully develop, an industry analyst and financier said.

Bill Marko, managing director of Jefferies & Co. Inc., said the total breaks down to an average of $70 billion in capital needs every year for the next 30 years.

In a recent presentation to the Independent Petroleum Association of America, Marko said the industry has undergone a major transformation since technology allowed producers to “crack ...