Published September 2018

The role of mud volcanism in formation of oil and gas fields

I.S. Guliyev

N.P. Yusubov

On the territory of Azerbaijan located in the central part of Mediterranean mobile belt and characterized with high seismicity, mud volcanism, wide-scale distribution of soil slip processes, as well as contrast nature of modern vertical and horizontal movements, permanent geodynamic processes take place in sedimentary sequence. More active of them are tectonic processes and mud volcanism. The paper presents various opinions and the views of the authors concerning geodynamic processes, due to which oil-gas deposits, connected with mud volcanism are formed. The results of researches on the elaboration of distribution zone of Maikop sediments, with which the roots of mud volcanoes connected, are commented. According to the results of investigation, carried out using 2D/3D seismic exploration and geophysical well survey data, the conclusion is made on that the mud volcano is connected with the Maikop delta with the square of 57 000 km2, with numerous river arteries, bringing to it terrigenic material from three directions – north-west (Paleokura), north (Paleopirsaat, Palovelvelechay, Paleosamur, Paleovolga) and north-east (Paleoamur) as well. It is supposed that in the course of basin filling, depending on tectonic processes (downwarping, upheaval, dip, inversion, etc.) stipulating transgression and regression of coastline, river systems occupied the same areas. This process was of inherit character, i.e. river systems remained practically in the former areas, in other words, occupied certain space above Maikop delta. The evolution of basin sedimentation formed multiple-deck deposits in geological section, formed by river systems. The fluid with non-Newtonian properties, which are Maikop clay formations, accumulated in conditions of fast-submerging sedimentary basin and located under the multiple-deck river systems, as a result of Rayleigh-Taylor phenomenon, formed the intrusion into the overlying environment (the process is still ongoing). It is obvious that this liquid containing the mass of mud and hydrocarbons, initially fills the porous zones with gas, oil and water. The process continues until the pressure injecting the fluid into the porous medium created by river systems remains higher than geostatic one. At a sufficient pressure, the liquid breaks through to the surface. Thus, hydrocarbon deposits and eruptive channels of mud volcano are formed. Described process creates conditions for horizontal and vertical migration of hydrocarbons.