RUSSIAN RESERVES TERMINOLOGY BECOMING CLEARER

Russian scientists are slowly lifting the official secrecy that for more than 50 years shrouded data on the former Soviet Union's oil reserves.

Information now being disclosed by Moscow researchers is still short on specifics and generally provides only broad parameters regarding crude/condensate reserves in the new Commonwealth of Independent States. A major problem is that the category of reserves termed "explored" in the Soviet era and carried over to evaluate C.I.S. reserves is more inclusive than the proved classification employed by such nations as the U.S., Canada, and Saudi Arabia.

Even so, recent Russian reports shed considerably more light on the division of oil reserves among the 15 republics that used to comprise the U.S.S.R. Comparisons have also been made between crude/condensate reserves in western Siberia's Tyumen Province-by far the biggest C.I.S. petroliferous region-and several of the Middle East's leading oil producing nations.

TYUMEN VS. MIDDLE EAST

V. Isayev, a director of the Russian Federation Academy of Sciences' Institute for Oriental Studies, asserts that Tyumen Province has 13.8 billion metric tons (100.74 billion bbl) of "black gold" reserves presumably in the explored category, which include A, B, and C, classifications.

He compares Tyumen's reserves with those he attributes to Iraq (96.36 billion bbl), Kuwait (95.63 billion bbl), and Iran (88.33 billion bbl).

However, the figures Isayev cites for the three Persian Gulf nations are very close to the proved reserves estimated for those countries by western petroleum experts. Only Moscow's categories A and B plus the smaller part of C, would be considered proved by U.S. criteria.

Writing in the Moscow newspaper Argumenty i Fakty (Arguments and Facts), Isayev also states that the Russian Federation has 85% of the explored oil reserves of the former U.S.S.R., Kazakhstan 9%, Azerbaijan 2.3% (mostly offshore in the Caspian Sea) Turkmenistan 2%, and all of the other C.I.S. republics, including Ukraine, only 1.7%.

Western Siberia's share of C.I.S. explored reserves is placed at 66%, with Tyumen Province apparently accounting for about 62% and Tomsk Province almost all of the area's remaining 4%.

COMPARING RESERVES

Assuming there is a close relationship in definition between Isayev's estimated 100.74 billion bbl of explored oil reserves for Tyumen Province and the 95.63 billion bbl attributed to Kuwait, the proved reserves total for the entire C.I.S. could be projected as high as 162.5 billion bbl.

But since Moscow's explored reserves also include a considerable quantity of oil that would be considered probable by U.S. definition, proved reserves for the C.I.S., according to Isayev's assessment, would likely be considerably less than 162.5 billion bbl.

Further complicating the picture is Isayev's tacit acceptance of "various estimates," presumably including those made abroad, that the former U.S.S.R. had 6-10% of the world's explored oil reserves (compared with more than 40% for gas).

On this basis, equating explored with proved and using the International Petroleum Encyclopedia (IPE) estimate of 991 billion bbl of worldwide proved reserves on Jan. 1, 1992, the C.I.S. would have 99.1 billion bbl of proved reserves, assuming 10% of the global total, but only 59.5 billion bbl assuming a 6% share.

The 59.5 billion bbl figure for C.I.S. proved reserves is very close to IPE's estimate of 57 billion bbl for the commonwealth at the beginning of 1992. A number of western estimates closely approximate the IPE figure, while some differ radically.

OTHER ESTIMATES

Among U.S. geologists specializing in C.I.S. petroleum research, estimates of western Siberian oil reserves alone range from as little as 40 billion bbl in the explored category to 180 billion bbl including 60 billion bbl of proved plus 120 billion of probable (including inferred) reserves.

If the higher 180 billion bbl figure for western Siberia is accurate, overall C.I.S. proved plus probable reserves could be as high as 273 billion bbl. That would compare with nearly 258 billion bbl of proved oil reserves credited to Saudi Arabia on Jan. 1, 1992, by IPE.

Early this year, the well-informed British monthly publication Eastern Bloc Energy (EBE) cited a figure of about 14 billion metric tons (102.2 billion bbl) of proved plus probable oil reserves for the former U.S.S.R. It based this calculation on a statement in July 1991 by Lev Churilov, the Soviet Union's then minister of the oil and gas industry, that the U.S.S.R. had 23.5 billion tons (171.55 billion bbl) of proved, probable, and possible oil (categories A, B, C1, C2, and most of C3), with the possible category representing about 70% as much oil as the 102.2 billion bbl in the proved plus probable classification.

Referring to data provided by Russian oil trader Valery Neverov, EBE calculated the U.S.S.R.'s remaining proved, probable, and possible reserves on Jan. 1, 1991, at 21.6 billion tons (157.7 billion bbl). Of this, western Siberia accounted for an estimated 15.3 billion tons (111.7 billion bbl).

The British publication believes Soviet proved plus probable reserves held steady at about 102.2 billion bbl during the 1980s and began to fall in 1990. But it said that the size of oil reserves was not in itself a constraint on production as of early 1992.

SUPPORTING PRODUCTION

Some observers now question whether C.I.S. category A reserves, most of which are defined as "drilled" or "developed," are still adequate to enable the commonwealth to maintain even its recent oil flow of about 9 million b/d.

Officials of the former U.S.S.R.'s Ministry of the Oil and Gas Industry complained before the Soviet Union's breakup that B, C1, and C2 reserves were being upgraded to the producible A category too slowly.

In establishing its table of categories for oil and gas reserves and potential resources, Moscow included in overall reserves (A, B, C1, C2) what would be classified as proved and probable reserves in the U.S., Canada, and Saudi Arabia.

The Soviet explored category (A, B, C1) was not only more inclusive than the U.S./Canadian/Saudi proved category but also broader than the French, German, and Dutch proved reserves category. But it was more restrictive than reserves rated as proved in North African countries, according to a Soviet handbook.

RUSSIAN CATEGORIES

By Moscow's definition, category A represents reserves "in deposits or parts of deposits studied in detail to the extent that there is complete ascertainment of the type, form, and size of the deposits, thickness of the effective oil and gas pay zones, reservoir type, changes in reservoir characteristics, oil and gas saturation of productive zones, characteristics and composition of oil, gas, and condensate in place, zone pressures, optimum development regime, well productivity, etc."

Category B covers hydrocarbon reserves "in deposits or parts of deposits where oil and gas content has been determined on the basis of commercial flow from wells in the various internals. Other data obtained regarding the deposit are sufficient to formulate development plans."

Category C1 reserves include a minor part that would be proved by U.S. standards, but most of this oil and gas would be classified as probable. Moscow says these reserves "are in deposits where the presence of hydrocarbons has been established on the basis of commercial oil or gas flows from wells.

"Positive results indicating C1 reserves have also been obtained by geological and geophysical work in untested wells. The type, form, and size of C1 deposits and reservoir conditions have been ascertained by exploratory and development drilling, with accompanying geological and geophysical evaluation of the area."

All C2 reserves, together with the large part of C1 reserves not included in the U.S. proved category, fall into the U.S. probable classification. Most C2 reserves would be regarded as inferred by U.S. definition, and a somewhat smaller percentage as indicated.

Moscow defines C2 reserves as "those in a deposit (or part of a deposit) whose presence has been based on data obtained from geological and geophysical studies of unexplored parts of the deposit adjoining other parts of the deposit containing reserves in higher categories."

C2 reserves also include those "in interstitial and overlaying untested formations of explored fields.

"Form and size of C2 deposits, occurrence conditions, thickness of pay, properties of the zones, and composition and properties of the oil, gas, and condensate have been generally determined by results of geological and geophysical study together with data obtained from a better studied part of the deposit or by analogy with explored fields."

According to the former Soviet and apparently current C.I.S. classification, C3, D1, and D2 categories are "potential resources." They include resources defined by U.S. standards as possible, hypothetical, and speculative.