THE ORINOCO OIL BELT, VENEZUELA

Abstract

The Orinoco Oil Belt of Venezuela is a very extensive, non‐discrete, crude‐oil producing area located along the southern third of the Maturín (Eastern Venezuela) basin, north of the Orinoco River and the Guayana Shield. It extends due westwards from Puerto Ordaz for 460km; the main producing areas, defined on the basis of productivity and magnitude of crude oil in‐place, cover 13, 600 sq. km. There are no significant surface indications of petroleum anywhere in the Belt. The first well drilled was La Canoa‐1 in 1936, initiating a stage of exploration which ended in 1967 with publication of a preliminary evaluation of the potential reserves; the Ministry of Energy and Mines, then of Mines and Hydrocarbons, and the State oil company Corporación Venezolana del Petróleo (CVP) completed a second stage of exploration in 1977; Petróleos de Venezuela and its operating companies then drilled 669 wells in five years (1979–83) totalling 643,000 m with 5.5 MM** m of logs, and shot 15,000 km of seismic lines at a cost of $US 615 MM, an effort conservatively estimated as having taken 2,500 man‐years. The main producing areas are, from east to west, Cerro Negro, Pao, Hamaca, San Diego, Zuata, and Machete. Petroleum characterisation in the Belt is based on the study and analysis of 288 samples. Viscosity (dynamic) of the crude oils at reservoir conditions ranges from 2,000 to 7,000 m Pa.s (cp)†.Production rates average 25 cu. m/d(160 b/d), increasing fourfold after steam stimulation. At the end of 1985, production was 13,000 cu.m/d(80,000b/d)†, from the Cerro Negro and Hamaca main producing areas. Operating costs are similar to those in other heavy‐crude oilfields in the basin. The volume of crude oil in‐place is estimated to be 187.8 B cu. m (1,181 B brls), which makes the Orinoco Oil Belt the largest crude oil accumulation in the world. Proved reserves are 4.161 B cu. m (26.170 B brls). and unproved reserves 14.822 B cu. m (93.230 B brls). Investigative activities are underway, particularly in the Cerro Negro and San Diego producing areas. In subsequent papers of this thematic survey, A. Isea presents a geological synthesis of the Orinoco Oil Belt; G. Don Kiser discusses the exploration results of the Machete area; A. Santos and L. Frontado describes the reservoir geology of the Cerro Negro steam‐injection area; and A. Vega and I. de Rojas summarise exploration results from the Zuata area.