The Orinoco Heavy-Oil Belt Pilot Projects and Development Strategy

Abstract

SPE Members Abstract The development of the Orinoco extra heavy oil belt (Faja Petrolifera), known as the largest extra-heavy (8.5 API) hydrocarbon accumulation in the world, has become a major goal for the venezuelan oil industry in the next decade. The Cerro Negro area, contains 213 billion stb and the current estimation for the primary recovery factor is 12% of the stock-tank original oil in place (STOIIP). Following the exploratory campaign, in the early eighties, three pilot projects were initiated (0-16, J-20 and K-20) in the Cerro Negro Area. These pilots consist of patterns of vertical producing wells and clusters of highly deviated wells with different spacing, completion type, sand control, stimulation (huff and puff) and lifting process. Furthermore, since 1990 two horizontal wells were drilled, evaluated and monitored in cold production, using the neighboring vertical wells. The acquisition of an exceptionally large data set in the exploration/appraisal step (207 wells) and the three pilot projects (155 wells) not only provided a unique opportunity for thorough study each of the relevant disciplines involved in the reservoir management and production facilities design, but also promoted a set of new technologies to be applied in the design of the commercial development of these prolific extra heavy reservoirs. Introduction The Orinoco Belt located in south-eastern Venezuela is probably the largest essentially untapped oil accumulation in the world. North of the Orinoco River, the Belt stretches over a length of some 700 km, covering an area of approximately 54000 km 2 (greater than the size of Denmark). It contains an estimated 1182 billion bbls of original oil in place (STOIIP), distributed in three areas as follows: Cerro Negro 213 billion STB Machete-Hamaca 469 billion STB Zuata 500 billion STB The Cerro Negro area was selected as the first area to be investigated, comprising a region of 7000 km 2 and contains in the main member (Morichal formation) 157 billion bbls of STOIIP. From 1979 to 1982 a total of 207 exploratory wells were drilled and 155 wells for development including three modules 0-16, J-20 and K-20 to determine the expected performance profile for future commercial development. The K-20 modern nine-well cluster has tested 550 BOPD each well in cold production. The feasibility study of the Cerro Negro, was initiated to answer the following questions: * What effects do reservoir parameters and well design have on short and long term performance? * Which reserves are needed to support a target plateau rate of 120,000 mil stb/d and at what well spacing? * How to increase understanding of the recovery mechanisms in order to contribute to the decision making process, and to partially minimise the risk associated with the future capital expenditure required for reservoir development? According the complexity of the development of this huge heavy oil accumulations it was considered in the early 80's the necessity for starting an experimental project located in Cerro Negro (Fig. 1). This project was based on the technological background accumulated by the Venezuelan oil industry in the development of the heavy-oil reservoirs during the last thirty years. Development of Heavy-Oil Reservoirs in Venezuela Before concentrating on the Orinoco Belt a brief summary of the experience obtained in the traditional areas will be discussed as a mainframe for the paper presented. In Western Venezuela, the main Bolivar Coast reservoirs under exploitation (Bachaquero, Lagunillas and Tia Juana Post-Eocene) contain heavy crudes of 11 to 15 APT gravity, with in-situ viscosities ranging from 100 to 10,000 cp. The original oil in-place estimated for these three reservoirs is 63 billion bbl of oil. The actual recovery is 14% STOIIP mainly due to formation compaction and solution gas drive, enhanced by steam soak in most of the reservoirs. P. 207^