G. Alan Petzet
Exploration Editor
Mongolian Petroleum Co. (MGT), formerly the Ministry for Energy, Mining, and Geology, is trying to disseminate information about Mongolia's oil and gas potential in a bid to attract foreign operators.
Exploration Associates International of Texas Inc., Houston, has prepared a report on the country's potential, mainly by translating reports prepared by geoscientists from the Soviet Union, Hungary, Romania, Poland, and the former East Germany.
The reports, in Russian, resulted from geological and geophysical studies conducted in Mongolia during 1939 89 under agreements with the Mongolian government, says William C. Pentilla, vice president of Exploration Associates.
Exploration Associates is completing a report on the country's petroleum potential. The Mongolian government plans to award exploration areas to western companies in 1991 or 1992.
GEOLOGICAL SETTING
Soviet and Mongolian geoscientists have defined 13 major sedimentary basins in Mongolia. They divided the basinal systems into 59 sub basins.
Outside the basins, the surface is metamorphic, granitic, or volcanic rock.
The subbasin and basin boundaries and thickness of sediments have been determined by surface geological mapping, core holes, production wells, exploratory wells, interpretation of satellite photographs, and geophysical surveys.
The geophysical data include electrical, gravity, magnetic, and seismic surveys.
Mongolia contains Cenozoic and Mesozoic rift basins developed in accretionary terrane on the southern margin of the Siberian craton.
Successive tectonostratigraphic terrane accreted to the Laurasian, Siberian craton during the Proto-Tethys, Paleo Tethys, and Neo-Tethys.
These tarranes have been described as microplates made up of continental, ocean basin, and volcanic arc fragments docking onto the Siberian craton. The first accretionary terrane north of Mongolia is the late Proterozoic Baikalian.
In northern Mongolia the terrane involves Caledonian accretion of Devonian and younger sediments. In southern Mongolia, the terrane is made up of the Hercynian accretion of Permian and younger sediments.
Extensive, post accretionary rifting developed during extensional periods of opening and closing of Paleo-Tethys and Neo-Tethys.
Rift and graben deformation was initiated in the Upper Jurassic. Rift fill included conglomerates, breccias, and volcanics.
During the Lower Cretaceous, continental deposits with lacustrine clastics continued as the rift fill sequence. The Upper Cretaceous continental sediments are related to the wrench rifting, compressive phase.
The Upper Jurassic-Lower Cretaceous lacustrine shale sandstone sequence contains the known hydrocarbon source rocks and reservoir rocks in the southeastern and eastern Mongolian basins.
OIL OCCURRENCES
Oil occurrences in Mongolia's basins and subbasins are surface oil seeps, impregnated outcrops, and oil shows in cores and samples.
Two oil fields, Zuunbayan and Tsagaan-Els, have been discovered in the Zuunbayan subbasin of the East Govi basin.
Zuunbayan field, about 286 miles southeast of Ulaanbaatar, was discovered in late 1941 by core hole drilling of surface oil seeps.
Tsagaan-Els field, about 12 miles southwest of Zuunbayan field, was discovered in 1953 by exploratory drilling on an anticline defined by seismic data.
Zuunbayan field was developed, and oil was produced until the on site refinery was destroyed by fire in December 1969. Tsagaan-Els field was not developed because of lack of facilities to lift and transport the high paraffin content oil.
Zuunbayan field, a faulted anticline with about 3 sq miles of closure, had a total of 200 wells that produced a combined 1,040 b/d during 1955, 840 b/d in 1957, and 710 b/d in 1959. Cumulative production is reported to be about 3.85 million bbl.
Reservoirs are silty sandstones and conglomerates. Source rocks are bituminous claystones and shales. All are in lacustrine sediments of Lower Cretaceous and Upper Jurassic.
EXPLORATION HISTORY
About 200 exploratory wells have been drilled in Mongolia, about 80% of them in the East Govi basin.
Several thousand shallow core holes related to oil and gas exploration have been drilled in Mongolia, mostly in the East Govi basin.
More than 60% of Mongolia has been covered by surface geological mapping, at various scales, supplemented by geochemical and geophysical surveys.
The total volume of seismic data acquired in Mongolia is unknown because of incomplete records.
There are estimates that more than 1,240 line miles of analog single fold seismic data were acquired by Soviet and Hungarian geophysical expeditions in the 1940s to 1960s, mainly in eastern Mongolian basins.
RECENT ACTIVITY
During late 1989 and early 1990, the Mongolian Geophysical Expedition acquired about 150 line miles of 1,200% digital common depth point reflection seismic data in the Nyalga basin.
In early 1990, the new Ministry of Heavy Industry, formerly the Ministry of Energy Mining, and Geology, formed Mongolian Petroleum Co (Mongol Gazryn Tos or MGT).
The company was formed to administer all petroleum related matters for the ministry and the government.
Subsequently, MGT staff members have been conducting geological exploration surveys in the field. The geophysical expedition staff also has been conducting field exploration. These staffs compile, prepare, and evaluate data reviews and studies.
MGT is continuing a major effort to formulate a petroleum law with supplemental regulations.
It is the intent of the government to have the petroleum law and regulations submitted for debate and adoption by the Great People's Khural (congress) before yearend 1990.
In September 1990, during the reorganization of the government, the Ministry of Heavy Industry was dissolved. MGT, which was responsible to that ministry, now is an independent organization responsible to the government.
An MGT delegation and Exploration Associates will present a joint venture report, "The Petroleum Potential of Mongolia," in Houston Dec. 3.
The MGT delegation, to be in Houston Nov. 26-Dec. 8, will include D. Sodnom, president; B. Dendevchuluun, vice president; D. Purevdorj, geoscientist; D. Baatar, lawyer; and D. Khuralbaatar, economist and translator.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.