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Ufa Section September Technical Meeting

Posted on 25 September 2017

The upcoming technical session organised by Ufa Section will take place on 29 September 2017, 1900 hours.

Topic: 'Complex Well Log Analysis in Naturally Fractured Paleozoic Reservoirs', the speakers are Kirill Ezhov, Expert for the petrophysical interpretation of logging data, and Mladen Blagojevi , Specialist for the petrophysical interpretation of logging data, NTC NIS-NAFTAGAS d.o.o.Novi Sad.

Participation is free. If you plan to attend, please send your request to FaizovaSN@ufntc.ru or leave your request at Ufa NTC Facebook Group before 1800 hours (Moscow time) 28 September 2017, so that section can prepare enough seats.

ABSTRACT

Introduction
Hydrocarbon reserves related to the basement were discovered in each part of the world. Such reservoirs include fractured or weathered metamorphic or magmatic rocks with complicated structure. There is no clearly defined method for identifying pay zones and their properties using standard techniques. Each oil field has to be studied individually; patterns have to be identified and result-oriented approaches developed. 
Combining core analysis, standard and special logging techniques and modern reservoir properties simulation methods in a unified complex study. The Paleozoic rock has three main types of cavitation: fractures, caverns and the hollow zones of disintegrated rock. The best-producing intervals are often related to fractured zones with specific elastic and mechanical properties. The complex geological structure of Paleozoic rock contains too much uncertainty, which prevents precise estimation of petrophysical parameters based on common interpretational models (the use of these models would lead to an overestimation of petrophysical parameters), as well as the use of standard well log techniques for separating and defining productive intervals. 

In this paper, indirect and direct approach to the reservoir characterization of fractured zones were applied based on the estimated physical and mechanical characteristics of the formation with the help of advanced well logging techniques.
The first step towards the allocation of perspective zones is done with the use of conventional well logging set to determine the mechanical characteristics of formation, lithology, fluid phase participation and total porosity.
The indirect approach can be separated into 2 main directions which are included in the producing intervals characterization:
· Petrophysical analysis on qualitative and quantitative level;
· Analysis of elastic and mechanical properties.
Reservoir properties are estimated on the base of 3-mineral model adapted for schistose rocks: clays (metamorphized chlorite and kaolinite), micas (metamorphized muscovite and biotite) and group presented by metamorphized quarts and plagioclases. Relatively small amount of pyrite and hematite (1-2%) was integrated into the properties of the third group. Correction and correlation of the created model was performed on the basis of SCAL analysis (XRD), while the porosity of the calculations from the volumetric mineral model was compared with the estimated porosity based on the NMR measurement in key wells.
Quantitative estimation of fluid saturation currently is not possible due to the high resistivity of formation and measuring tool constraint. Properties of the fluid phase and water-cut are known from active production.
The second step of the indirect investigation was around acoustic and geomechanical properties. On the first step shear slowness (S-wave) was synthesized from compressional slowness (P-wave) and mineral volumes.
Each mineral has specific mechanical properties: elastic, brittle or plastic. In a mixture, it is not always the same. On the next step, the relative brittleness was estimated.