LONDON/HOUSTON, Sept 17 (Reuters) - Commercially recoverable reserves of tight oil in the rest of the world could be double or more those of North America and the geology of the 23 best opportunities is better in some cases, according to a new study.

But the study by analysis firm IHS warned development in newer regions will likely to be slower than in the United States as many countries could run into constraints including government policy and regulation, lack of access to specialised kit and skilled labor, and access to land.

Tight or unconventional oil requires the same hydraulic fracturing and horizontal drilling techniques as shale gas.

"The global potential is really quite large and the challenges don't just involve technology but legal frameworks and above-ground issues too," Pete Stark, a co-author of the study, told Reuters.

The 23 highest-ranking tight oil areas identified by the study include well-documented areas such as the Vaca Muerta formation in Argentina, the Silurian "hot" shales in North Africa and the Bazhenov Shale in west Siberia.

However, the list also includes lesser-known geological plays in Europe, the Middle East, Asia and Australia.

Costs for unconventional wells in tight deposits can be three or four times higher than for conventional wells.

Like shale gas, tight oil it has become a boom U.S. industry, transforming the economy through cheaper energy and reduced reliance on imports, leading other countries to look at developing similar reserves.

The study found that more than half the global technically recoverable reserves outside North America were concentrated in just 23 of 148 potential development areas it analysed. It put the total at 300 billion barrels, with 175 billion in the top 23 areas - known as "plays" in the oil and gas industry.

Commercially recoverable resources in North America have been estimated at 43 billion barrels.

The study maps the potential for "tight" or unconventional oil without the benefit of well data and so estimated only what are known as "technically recoverable" reserves outside North America by looking at their geological characteristics.

"The final measure of technical or commercially recoverable resources cannot be truly known until the actual well data is available," Jan Roelofsen, IHS research director and adviser for unconventionals, said in a statement.

"The potential of just the highest-ranking plays is likely double the size of North America's resources, and that is a conservative estimate."

Output from fracked wells are often characterized by rapid rates of decline, then steady production for about 20 years, according to IHS assumptions.

Major Plays, Costs

"The range of geological characteristics and risks of the 23 highest-ranking global tight oil plays compare favorably, or even better in some cases, than those of leading North American plays," said Steve Trammel, also an IHS research director and adviser and the project leader for the study.

The IHS study puts the cost of the average well outside North America at $8 million compared with $5.6 million inside North America, ranging from $6.5 million in Australia to more than $13 million in parts of the Arabian Peninsula, said Stark.

"There is no single magic cost because the plays differ dramatically," Stark, an IHS senior research director, said. One big cost factor is well depth and "some plays are in deserts so water is a major issue."

He said the study assumed basic levels of infrastructure development and field services were in place for the oil sector in emerging markets.

"Currently, costs for wildcatters are much higher," he said, referring to people who are among the first to drill on untapped terrain.