In the current context, it may be economically more profitable to look at old oil fields than to look for new ones. This is the astonishing conclusion that researchers from the Institute of Oil and Gas Problems have just delivered in the "Reports of the Russian Academy of Sciences". Oil reappears from time to time in old fields and wells that have been in operation for a long time. Russian specialists under the leadership of academician Anatoly Dmitrievsky have offered an explanation for this phenomenon.
The earth's crust looks like the puff pastry of a cake. It is made of hard layers and porous and cracked layers, filled with various fluids, including petroleum. In some places, the bark is crossed by a network of cracks and fractures. The fractures form hollow cavities, arranged almost horizontally and united in a network. Under the action of tectonic forces, this complex system is in perpetual motion. The layers move, the cracks widen and liquids start to flow from the neighboring porous layers into the cavities that form. According to scientists, this mechanism of liquid displacement is present both in fractures and in thin cracked layers which extend over considerable distances and which operate at a depth of 10 to 15 km.
The displacement of liquids caused by the enlargement of the internal cavities is variable. Sometimes the oil flows, sometimes it flows back. The regime and the period of the oscillations depend on the size of the region concerned. The Romachkino deposit in Tatarstan is exemplary in this regard. The quantity of oil that has been extracted from it already considerably exceeds the previously proven reserves. According to the oil company Tatneft, more than 65% of the oil produced in Tatarstan comes from old deposits, already 80% exploited. Thorough exploration of certain strata has increased oil reserves by half over the past 25 years. Scientists have also discovered that the area of petroleum deposits and their reserves increases with increasing density of the fracture network.
source:
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