Abstract: The Geological and Geochemical Study of the Mud Volcanoes of Azerbaijan

I. S. Guliyev, A. A. Aliyev, R. R. Rahmanov, A. A. Feizullayev

Azerbaijan is a classic region for the study of mud volcanism. Of the 700 mud volcanoes known in the world, 220 are in Azerbaijan. These are of great interest, not least in relation to oil and gas exploration since they give information on subsurface sediments beyond the reach of drilling.

Mud volcanoes are clearly visible on satellite images. They are confined to structural lineaments and associated fractures. Changes in the morphology of some mud volcanoes post-eruption can be detected from a series of images pre-dating and post-dating eruptions.

Mud volcanoes are notable for gradients of temperature that are by an order of magnitude or a factor of 10² greater than the temperature gradients established elsewhere.

The gases of mud volcanoes consist mainly of methane (95-100%). There are small amounts of C_2-6, CO₂, N₂, He and Ar. The isotopic composition of carbon (ICC) within the methane varies from -61.2 ^pmil to -35.9 ^pmil which is isotopically heavier than the methane from producing fields. The ICC of the CO₂ has a very wide range (from -49.6 ^pmil to +23.1 ^pmil), indicating several sources of its formation. The isotopically superheavy CO₂ (+5 ^pmil) is especially interesting.

Oils from mud volcanoes are typically severely biodegraded. Their ICC ranges from -24.76 ^pmil to -28.2 ^pmil. A relationship between ^dgr¹³C of oils and ages of accumulations has been established.

Waters of mud volcanoes are lightly mineralised, containing chiefly bicarbonates and sodium. The hydrogen composition of the water is abnormally heavy.

Ejected rocks from mud volcanoes range in age from Cretaceous-Pliocene. Their study suggests that deeply buried reservoirs maintain good poroperm characteristics because of relatively little catagenesis.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France