Microporous rocks features and identification on the base of core and well logging data

UDK: 550.8.05:551.734
DOI: 10.24887/0028-2448-2018-6-58-61
Key words: structure of the porous space, porosity, permeability, residual water saturation, electric resistivity, microlog, normalization of logging data, nuclear magnetic logging, capillary tests
Authors: G.R. Amineva (BashNIPIneft LLC, RF, Ufa), A.V. Dvorkin (BashNIPIneft LLC, RF, Ufa), T.V. Burikova (BashNIPIneft LLC, RF, Ufa), K.D. Shumatbaev (BashNIPIneft LLC, RF, Ufa), O.R. Privalova (BashNIPIneft LLC, RF, Ufa)

The paper describes the study of microporous rocks based on core laboratory analysis, their characterization and evaluation from wireline logs. Very fine grained fabric of carbonate rocks with significant concentration of micrite creates pores in the groundmass at the micro level attributed to the microporous type of the void space, characterized by lower permeability, higher residual water saturation and lower electrical resistivity as compared to fractured-vuggy-porous types. Taking into account the characteristics of microporous rocks identified in core laboratory studies such parameters as residual water saturation and electrical resistivity are analyzed as criteria for the identification and evaluation of microporous rocks in well logs. In the absence of standard well logging special methods in the carbonate sediments, it is possible to identify microporous rock type using the following methods. In the zone of maximum saturation for normalization of electrical logging and neutron gamma ray logging curves, there is the absence of increments of these methods for microporous non-reservoir rocks (porosity 5-10%) is typical. Irrespective of reservoir saturation, microporous limestone is distinguished by higher absolute values of electrical resistivity on microprobes as compared to pore-cavern reservoir when recording logging in a well drilled with clay drilling mud and the absence of micropotential-probe values increment as compared to microgradient-probe values increment for microporous non-reservoir rocks.

So application of proposed algorithm allows microporous rocks intervals identifying by electrical logging which allows specifying thickness of reservoir and, consequently, fundamentally changes the concept of fluid model.


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