The concept of a giant accumulation of heavy oil in the Eastern Venezuela Basin was born during the 7th World Petroleum Congress, heldin Mexico City, April 2-9, 1967. The Venezuelan geologists Jose Antonio Galavis S. (Ministry of Mines and Hydrocarbons, Caracas) and Hugo Mario Velarde Ch.(Corporacion Venezolana Del Petroleo, Maracaibo) presented and published their work "Geological Study and Preliminary Evaluation of Potential Reserves of Heavy Oil of the Orinoco Tar Belt, Eastern Venezuela Basin".
The Orinoco Belt takes its name from the Orinoco River,since is located along the northern margin of the river, to the North of Bolivar State - Guayana Shield-, spanning from East -West of the southern portions of the states Delta Amacuro, Monagas, Anzoategui and Guarico. The publication defined the Orinoco Tar Belt as the zone about 600 kilometers long[365 miles] and 53 kilometers wide [31 miles], with a volume of heavy oil "in situ" estimated at 693 x 10^9 barrels.
Currently, the State-owned PDVSA extended the width to 70 kilometers [44 miles], and maintain an estimated of 235 billion barrels of recoverable oil [3.74x10^10 cubic meters], applying EOR.
Galavis and Velarde summarized 30 years of exploration after the first well was drilled and tested in Jan 1936, ~ 25 miles west of the Soledad town in the State of Anzoategui. The well is the Canoa-1, T.D. 3855 ft.[1176 m], and oil gravity of 7 (API), from sands, but was no commercial. During 1938, the Suata-1 was drilled and tested, ~ 87 miles to the northwest of Soledad, near the town of Zuata, at the limit between the states of Anzoategui and Guarico. The Soledad town is a small port at the Orinoco River, in front of Ciudad Bolivar. The eastward Cerro Negro field was discovered in 1939, after the first two wells tested were dry.
The Orinoco Oil Belt is delimited to the north by the following giant oil fields, from west to east:
- Greater Las Mercedes area to the West, Guarico State. Discovered in 1941. Average API is 25-35. To the North-East of Las Mercedes are located the Yucal-Placer gas fields, discovered in 1948.
- Greater Oficina area, Anzoategui State.Discovered in 1937, average API gravity oil is 34, but 34-57 were reported, and a trend to have heavy oil to the South.
- The Anaco oil fields are located immediately to the north of Oficina, discovered by the Santa Rosa field in 1937; API gravities are in the range of 33-47. Associated gas is very important in these trend of fields.
- Greater Jusepin area, to the North of Monagas, was discovered in 1938, with average oil API gravity of 31.5. This is an area with associated gas.
- Greater Temblador area, to the East of the state of Monagas and discovered in 1936, includes the fields Uracoa (1937) and El Salto (1936). They are gas rich, and the API ranges between 18 -22, 22-28 to the West.
- The Tucupita field discovered in 1945. It's located to the East, at the limit between the Monagas and the Delta Amacuro states. The API oil gravity varies between 10-22.
In 1977, Petroleos de Venezuela, S.A., divided the Orinoco Oil Belt into 4 regions, and assigned them for E&P to the former affiliates(West -East): Corpoven, S.A.- Machete; Maraven, S.A.- Zuata; Meneven, S.A.- Hamaca; and Lagoven, S.A.- Cerro Negro. An intense exploration and production program was carried out, and during the official program called Apertura, in 1995, several projects started as Strategic Associations between private international/national sectors and Petroleos de Venezuela. The Sincor (Zuata area), Petrozuata, Ameriven in Hamaca, and the Cerro Negro were established in the Orinoco Oil Belt. However, a presidential decree in 2007 nationalized the extra heavy oil production and new Mixed companies were formed with PDVSA as the main associate, and the Oil Belt blocks got new names and mainly state-owned companies as partners of PDVSA.
From West to East the new names are Boyaca (former Machete), Junin (former Zuata), Ayacucho (former Hamaca), and Carabobo (former Cerro Negro). In that way, nearly 26 small blocks were separated and some of the former associations changed partners and names: Sincor is now PetroCedeño, Petrozuata is now Petroanzoategui, Cerro Negro is now Petromonagas, and Ameriven is now Petropiar. New Mixed Companies are formed nowadays after some initial partners sold their stakes.
Maps and summaries of this changes can be obtained via PDVSA's website or searching the net. Some publications with information related to the geology, exploration and production data are listed below.Notice only a few publications in Spanish, to reach a wider audience.
- Hedberg, H.D., Saas, L.C., Funkhouser, H.J. 1947. "Oil fields of Greater Oficina Area, Central Anzoategui, Venezuela". AAPG Bull., 31(12):2089-2169.
- Corfield, G.S. 1948. "Recent activities in Venezuela's petroleum industry". Economic Geography, 24(2):114-118.
- Mencher, E., Fichter, H.J., et al. 1953. "The Geology of Venezuela and its oilfields". AAPG Bull.37(4):690-777.
- Gonzalez de Juana, C., Iturralde de Arozena, J.M. & Picard Cadillat, X. 1980. "Geologia de Venezuela y de sus cuencas petroliferas". Ediciones FONINVES, Caracas.
- Perrodon, A. 1983."Dynamics of oil and gas accumulations". Elf Aquitaine. Comment: Figure 201 is the map of fields in the Central part of the Orinoco basin,Venezuela.
- R.F. Mayer, Editor, 1987. "Exploration for Heavy Crude Oil and Natural Bitumen". AAPG Studies in Geology # 25. Papers by: De Audemard, N.M., Chirinos, ML. & Layrisse, I. Fiorillo, G. Taheri, M. & N.M. De Audemard. The papers contain data about Crude properties, API gravity values, Cut Off values parameters for calculation of Net Oil Sand, ranges andaverage values of reservoir data, fluid properties of heavy oils, estimates ofrecovery factors and recoverable oil in Stock Tank Barrels (STB).
- Journal of Petroleum Geology. 1987. 10(2). Papers by Martinez, A.R. Isea, A. Don Kiser, G. Vega, A. & I. De Rojas, Santos, A. & Frontado, L. The papers contain data about Orinoco Oil Belt, geological synthesis, exploration results in Machete area, evaluation of Zuata area, and reservoir geology of the Cerro Negro Steam injection area.
- Trebolle, R.L. et al. 1993. "The Orinoco Heavy oil belt pilot projects and development strategy". OnePetro #25798-MS.
- James, K.H. 2000." The Venezuelan hydrocarbon habitat, Part 2. Hydrocarbon occurrences andgenerated-accumulated volumes". Jour. Petrol. Geology. 23(2):133-164.
- Uzcategui, E.2001. "Reservoir characterization and exploitation scheme in the Orinoco Oil Belt". OnePetro#69698-MS.
- Martínez, A.R.. 2004. "La Faja Del Orinoco". Editorial Galac, Caracas.
- Goddard, D. 2006."Venezuela Sedimentary Basins: Principal Reservoirs and Completion Practices. academy.edu.