Венесуэла, Пояс Ориноко: An Estimate of Recoverable Heavy Oil Resources
Introduction
The Orinoco Oil Belt Assessment Unit (AU) of the La Luna−Quercual Total Petroleum System encompasses approximately 50,000 km2 of the East Venezuela Basin Province that is underlain
by more than 1 trillion barrels of heavy oil-in-place (fig. 1)
The East Venezuela Basin is a foreland basin south of a fold belt (fig. 2).
The progressive west-to-east collision of the Caribbean plate with the passive margin of northern South America in the Paleogene and Neogene formed a thrust belt and foreland basin that together compose the East Venezuela Basin Province. Thrust faults associated with the fold belt caused lithospheric loading and basin formation, and the resulting burial placed Cretaceous and possibly older petroleum source rocks into the thermal window for the generation of oil. The oil migrated updip from the deeper basin to the shallow southern basin platform, forming the Orinoco Oil Belt. The oil is considered to be concentrated along a forebulge that formed south of the foreland basin (Bartok, 2003). The heavy oil in the Orinoco Oil Belt AU is largely contained within fluvial, nearshore marine, and tidal sandstone reservoirs of the Miocene Oficina Formation (Kopper and others, 2001; Bejarano, 2006).
Estimates of Original Oil-in-Place
A comprehensive study by Petroleos de Venezuela S.A. (PDVSA) established the magnitude of the original oil-in-place (OOIP) at 1,180 billion barrels of oil (BBO), a commonly cited estimate for the Orinoco Oil Belt (Fiorillo, 1987); PDVSA recently revised this value to more than 1,300 BBO (Gonzalez and others, 2006). In this study the median OOIP was estimated at 1,300 BBO and the maximum at 1,400 BBO. The minimum OOIP was estimated at 900 BBO, given the uncertainty of regional sandstone distribution and oil saturation (Fiorillo, 1987).
Estimates of Recovery Factor
Recovery factor, or that percentage of the OOIP that is determined to be technically recoverable, was estimated from what is currently known of the technology for recovery of heavy oil in the Orinoco Oil Belt AU and in other areas, particularly California, west Texas, and western Canada. The minimum recovery factor was estimated to be 15 percent, the recovery expected for cold production using horizontal wells. The median recovery factor was estimated to be 45 percent, on the assumption that horizontal drilling and thermal recovery methods might be widely used. The maximum recovery factor was estimated to be 70 percent, on the assumption that other recovery processes, in addition to horizontal drilling and steam-assisted gravity drainage, might eventually be applied on a large scale in the Orinoco Oil Belt AU.
Summary of Results
The assessment of technically recoverable heavy oil and associated gas resources is shown in table 2. The mean of the distribution of heavy oil resources is about 513 BBO, with a range from 380 to about 652 BBO. The mean estimate of associated dissolved-gas resource is 135 trillion cubic feet of gas (TCFG), with a range from 53 to 262 TCFG.
No attempt was made in this study to estimate either economically recoverable resources or reserves within the Orinoco Oil Belt AU. Most important, these results do not imply anything about rates of heavy oil production or about the likelihood of heavy oil recovery. Also, no time frame is implied other than the use of reasonably foreseeable recovery technology.
http://pubs.usgs.gov/fs/2009/3028/
http://pubs.usgs.gov/fs/2009/3028/pdf/FS09-3028.pdf
The Orinoco Oil Belt Assessment Unit (AU) of the La Luna−Quercual Total Petroleum System encompasses approximately 50,000 km2 of the East Venezuela Basin Province that is underlain
by more than 1 trillion barrels of heavy oil-in-place (fig. 1)
The East Venezuela Basin is a foreland basin south of a fold belt (fig. 2).
The progressive west-to-east collision of the Caribbean plate with the passive margin of northern South America in the Paleogene and Neogene formed a thrust belt and foreland basin that together compose the East Venezuela Basin Province. Thrust faults associated with the fold belt caused lithospheric loading and basin formation, and the resulting burial placed Cretaceous and possibly older petroleum source rocks into the thermal window for the generation of oil. The oil migrated updip from the deeper basin to the shallow southern basin platform, forming the Orinoco Oil Belt. The oil is considered to be concentrated along a forebulge that formed south of the foreland basin (Bartok, 2003). The heavy oil in the Orinoco Oil Belt AU is largely contained within fluvial, nearshore marine, and tidal sandstone reservoirs of the Miocene Oficina Formation (Kopper and others, 2001; Bejarano, 2006).
Estimates of Original Oil-in-Place
A comprehensive study by Petroleos de Venezuela S.A. (PDVSA) established the magnitude of the original oil-in-place (OOIP) at 1,180 billion barrels of oil (BBO), a commonly cited estimate for the Orinoco Oil Belt (Fiorillo, 1987); PDVSA recently revised this value to more than 1,300 BBO (Gonzalez and others, 2006). In this study the median OOIP was estimated at 1,300 BBO and the maximum at 1,400 BBO. The minimum OOIP was estimated at 900 BBO, given the uncertainty of regional sandstone distribution and oil saturation (Fiorillo, 1987).
Estimates of Recovery Factor
Recovery factor, or that percentage of the OOIP that is determined to be technically recoverable, was estimated from what is currently known of the technology for recovery of heavy oil in the Orinoco Oil Belt AU and in other areas, particularly California, west Texas, and western Canada. The minimum recovery factor was estimated to be 15 percent, the recovery expected for cold production using horizontal wells. The median recovery factor was estimated to be 45 percent, on the assumption that horizontal drilling and thermal recovery methods might be widely used. The maximum recovery factor was estimated to be 70 percent, on the assumption that other recovery processes, in addition to horizontal drilling and steam-assisted gravity drainage, might eventually be applied on a large scale in the Orinoco Oil Belt AU.
Summary of Results
The assessment of technically recoverable heavy oil and associated gas resources is shown in table 2. The mean of the distribution of heavy oil resources is about 513 BBO, with a range from 380 to about 652 BBO. The mean estimate of associated dissolved-gas resource is 135 trillion cubic feet of gas (TCFG), with a range from 53 to 262 TCFG.
No attempt was made in this study to estimate either economically recoverable resources or reserves within the Orinoco Oil Belt AU. Most important, these results do not imply anything about rates of heavy oil production or about the likelihood of heavy oil recovery. Also, no time frame is implied other than the use of reasonably foreseeable recovery technology.
http://pubs.usgs.gov/fs/2009/3028/
http://pubs.usgs.gov/fs/2009/3028/pdf/FS09-3028.pdf