Известия Томского политехнического университета: Инжиниринг георесурсов (Aug 2016)
Lithologic and petrographic features and reservoir properties of rocks of the AV1 horizon in the Las-Egan oil field
Abstract
Nowadays the problem of the efficient methods for exploring unconventional reservoirs and poor reservoir rocks are of great importance. Such rocks include the «ryabchik»-type AV1 horizon of Las-Egansky oilfield, represented by interbedded fine layers of sandstone, siltstone and claystone. This horizon is widely distributed in the Nizhnevartovsk Arch. The aim of the research is the detailed and systematic study of lithological and petrographic features of sediment horizon AB1 of the investigated oilfield and their typification on the basis of two or more parameters. The methods used. The core samples from sediments AV1 horizon of Las-Yogansky oilfield (wells 3001, 187r, 9609, 9617 were used for the study. The authors have analyzed more than 50 core samples using sedimentological and lithological research techniques of clastic sedimentary formations and carried out macro description of the core defining the textural features. The laboratory work included optical microscopy, particle size distributions, X-ray, electron-microscopic methods of study of the given rock samples, which allowed identifying their distinctive features by the physical and petrophysical parameters. Results. The AV1 horizon in the oil fields of Sublatitudinal Near-Ob region is characterized by a complex structure. The upper part of the horizon is composed of rocks with a high content of clay component. Lower section the clay «ryabchiks» are replaced by sandstone-bearing «ryabchiks», then the interlayers of laminar siltstones and siltstone-sandstones with flazernymi textures are observed. One can observe the top-down coarsening of terrigenous material, while the density of the rock is reduced, and the coefficient of porosity and permeability increases. Regional marker represented by the clayey deposits of the Koshai member occurs in the upper part of the AV1 horizon. The low marker is lumpy variegated clayey sediments of the Vartovsk formation. Two pay zones (АV1 [1+2] и АV1 [3]) are known in the AV1 horizon. They differ in lithology, depositional environment and oil flow rate.
