(GENETIC TYPES AND DISTRIBUTION PATTERNS OF FRACTURES IN CARBONATE NATURAL RESERVOIRS OF TIMAN-PECHORA OIL-AND-GAS PROVINCE)
The article presents the results of a set of geological and geophysical studies, which are used to characterize fracturing in carbonate natural reservoirs of the Timan-Pechora oil-and-gas province, its role in reservoir structure and its influence on the filtration-capacitative properties of rocks.
On the basis of literary and factual data, various parameters of fracturing (length, number of fractures per meter, their orientation, configuration, degree of opening, presence of traces of secondary mineralization/leaching, geodynamic state) and its genetic types, patterns of lateral distribution of fracturing and prerequisites for its development in different lithotypes of carbonate rocks as well as influence of different fracture types on filtration-volume properties are systematized and described.
Thus, for example, the baundstones are characterized by chaotic fracturing; the fractures are often twisted and cut the formational elements of the rocks. An exception is specific boundstones with biogenic layering (laminites), where sedimentary inherited subhorizontal fracturing prevails, sometimes determining lateral superpermeability of the thickness. At the same time, the number of fractures of different orientation, determining the vertical permeability, may be different, which affects the filtration-capacity properties of the reservoir as a whole. In clastic limestones with low values of primary porosity and low pore connectivity, the role of fracturing in the reservoir structure may be significant in contrast to organogenic-clastic limestones, where high primary porosity and attenuation of various fractures are observed. The role of fractures connecting inherited voids is high in secondary dolomites with a divergent crystalline structure.
It is noted that despite the low capacity of the fractured void space, the migration of fluids through the fractures often leads to leaching and formation of highly permeable fracture zones, increasing the total reservoir capacity.
I.S. Putilov1, 2, e-mail: Ivan.Putilov@pnn.lukoil.com
D.V. Potekhin1, 2, e-mail: Denis.Potekhin@pnn.lukoil.com
A.D. Saetgaraev3, e-mail: Almir.Saetgaraev@lukoil.com
A.V. Postnikov4, e-mail: Postnikov.a@gubkin.ru
O.V. Postnikova4, e-mail: olgapostnikova@yandex.ru
A.S. Rakhmatullina4, e-mail: rakhmatullina.a@gubkin.ru
D.O. Almazov4, e-mail: almazov.d@gubkin.ru
1 PermNIPIneft – branch of LUKOIL-Engineering LLC (Perm, Russia).
2 Federal State Autonomous Educational Institution of Higher Education “Perm National Research Polytechnic University” (Perm, Russia).
3 LUKOIL-Komi LLC (Usinsk, Russia).
4 Federal State Autonomous Educational Institution for Higher Education “Gubkin Russian State University of Oil and Gas (National Research University)” (Moscow, Russia).
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