Latin American oil finds come at right time. Despite slow market, oil finds will be boon to area's debt-ridden economies

For years petroleum geologist Bernardo Grossling has predicted that lots of oil would be found in Latin America. Now it's coming true: In July Brazil's giant state oil company, Petrobras, announced the discovery of a ``giant'' deep-water offshore oil well expected to produce 15,000 barrels a day. Brazil, says Mr. Grossling, could be self-sufficient in petroleum by 1990.

Because of new oil finds, Colombia expects to start exporting oil again in 1986. Discoveries in Colombia's Eastern Plains (Llanos Orientales) last year and early this year boosted the nation's oil reserves by 76 percent.

Mexico's proven reserves, almost half those of Saudi Arabia, continue to grow as exploration continues.

Grossling, who has just rejoined the United States Geological Survey after a leave-of-absence working for the Inter-American Development Bank (IADB), predicts major finds will also be made in Bolivia, Peru, and Argentina. And he expects Venezuela's already large reserves to grow as exploration continues in the Orinoco River area.

Indeed, the Chilean-born geologist forecasts that Latin America will eventually be found to have more petroleum reserves than the Middle East. The Middle East now has about 55 percent of world reserves, but is producing only some 20 percent of world consumption.

Some geologists find Grossling's forecasts overly ambitious. His recent book outlining the evidence behind such predictions, ``In Search of Oil'' (London, Financial Times), has aroused controversy. However, Grossling notes that he has been gathering the evidence for 10 years as part of assignments with both the World Bank and the IADB.

The latest Latin American finds come at a time when the oil business is what oil economist John H. Lichtblau calls a ``zero sum game.'' Since there is a glut of oil on the market and world oil consumption is growing slowly (about 1 percent a year), any new production probably means that somebody else's oil has to be left in the ground. Usually the marginal producers have been the Middle East nations that belong to the Organization of Petroleum Exporting Countries (OPEC), especially Saudi Ara bia.

Latin American oil is not as important to the world as it would have been in 1980, right after OPEC boosted its prices a second time, notes Mr. Lichtblau, president of the Petroleum Industry Research Foundation, Inc.

But for Latin American nations oil and gas finds can be extremely important.

Much of the oil, says Grossling, costs about $10 a barrel to produce. With crude priced at around $25 a barrel, profits on the new fields should be handsome, boosting government revenues and providing funds for economic development.

One giant new natural-gas field in southern Argentina has reserves whose present value matches that of Argentina's entire external debts, says Grossling.

Oil and gas exploration in Latin America was stepped up considerably in the 1970s and in this decade with aid from both the World Bank and the IADB. In some cases national oil companies did much or all of the job, as in Mexico, Brazil, and Colombia. In others, foreign oil companies have been given concessions.

However, Grossling points out, relatively far less exploration has been conducted in the prospective oil territories of Latin America than in the US, Middle East, or the Soviet Union.

``Latin America,'' he says, ``will be one of the major producing areas in the world.''

He sees the following as good prospects: sedimentary areas in the northern slope of Colombia, extending into the Caribbean; the region east of the Andes in Bolivia and Peru, where deeper drilling could find ``stratigraphic traps'' of oil; sedimentary basins off of Brazil and Argentina; and southern Chile.

``We are going to produce [an economic] revolution in these countries with very little money,'' Grossling says of Bolivia and Peru.

He doesn't see much hope for substantial amounts of oil in Central American nations. However, he speculates that Mexico's oil reserves could eventually double to match those of Saudi Arabia -- 160 billion barrels. Mexico, he says, is ``very cautious'' in releasing estimates of its petroleum reserves.

Colombia's latest discoveries include one field with an estimated 100 million barrels of crude so fine it is almost pure gasoline. Colombian output has nearly doubled from 179,000 barrels a day to 352,000 barrels The state-owned oil company, Ecopetrol (Empresa Colombiana de Petroleos) reckons that the new discoveries have added nearly 543 million barrels to the nation's reserves.

As recently as 1979, Brazil imported 85 percent of its petroleum, an economic burden that added to its massive external debts now exceeding $100 billion. Since then Brazil has managed to cut petroleum consumption, partially by stepping up the output of alcohol used for oil. At the same time, it has increased petroleum production to nearly half of the million barrels a day the country needs. Last year oil production rose by a record 40 percent.

Oil from new finds should help Brazil considerably with its foreign debt burden.