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USGS pegs Orinoco's recoverable figure at 513 billion bbl

Alan Petzet
OGJ Chief Editor-Exploration

HOUSTON, Jan. 22 -- The volume of technically recoverable heavy oil in Venezuela’s Orinoco oil belt is 513 billion bbl, making it one of the world’s largest accumulations of recoverable oil, the US Geological Survey said Jan. 22.

The range of recoverable oil is estimated at 380-652 billion bbl, the USGS said. Technically recoverable associated-dissolved gas is estimated at a mean of 135 tcf and a range of 53-262 tcf.

USGS made no attempt to estimate either economically recoverable resources or reserves, and the assessment implies nothing about rates or timeframes of production or the likelihood of heavy oil recovery.

The Orinoco Oil Belt Assessment Unit of the La Luna-Quercual Total Petroleum System covers 50,000 sq km of the East Venezuela Basin Province, which is underlain by more than 1 trillion bbl of heavy oil in place, the agency said.

The heavy oil in the assessment unit is largely contained in fluvial, nearshore marine, and tidal sandstone reservoirs of the Miocene Oficina formation.

“The reservoir sandstones, although porous and permeable, are characterized by several depositional sequences with considerable internal fluid-flow heterogeneity caused by juxtaposition of different facies and by shale barriers that reduce recovery efficiency,” USGS said.

The reservoirs are 150-1,400 m deep with heavy oil of 4-16° gravity. Viscosities range from 2,000 to 8,000 cp.

The oil in place estimate relied mainly on published geologic and engineering data for reservoirs (net oil-saturated sandstone thickness and extent), petrophysical properties (porosity, water saturation, and formation volume factors), recovery factors determined by pilot projects, and estimates of volumes of oil in place.

Petroleos de Venezuela SA estimated 1.18 trillion bbl of oil in place in 1987 and revised that in 2006 to a median of 1.3 trillion bbl, a maximum of 1.4 trillion bbl, and a minimum of 900 billion bbl.

Recovery factor was estimated at a minimum of 15% for cold production using horizontal wells. Recovery factor was put at a median of 45% to a maximum 70% using horizontal drilling and thermal recovery methods.

The USGS assessment is the first to identify how much is technically recoverable; that is, producible using currently available technology and industry practices, said Brenda Pierce, USGS Energy Resources Program coordinator.

USGS noted that worldwide oil consumption was 85.4 million b/d in 2008. The three largest consuming countries were the US at 19.5 million b/d, China at 7.9 million b/d, and Japan at 4.8 million b/d.

“Knowing the potential for extractable resources from this tremendous oil accumulation, and others like it, is critical to our understanding of the global petroleum potential and informing policy and decision makers,” Pierce said.

The Orinoco is the largest accumulation ever assessed by the USGS.

Contact Alan Petzet at alanp@ogjonline.com.


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