Abstract
This paper presents the results of modelling compressional and shear wave velocities and elastic moduli, and Poisson’s coefficient changes in the sandstone-shale rocks, based on the distribution of media reservoir (water, gas) in the pore space. Modelling was performed using Estymacja-TP computer program and theoretical Kuster-Toksoz and Biot-Gassmann relationships. The phase distribution of saturating pores (inclusions) in several ways was assumed. Calculations were made of elastic parameters in the deposits of the autochthonous Miocene Sarmatian in the borehole B-4. Using a method similar to the so-called “ Fluid substitution” modelling velocity changes of compressional and shear waves, elastic modulus, Poisson's ratio and the bulk density under various conditions of water and gas saturation were performed. The assumed of change in water saturation ranged from SW = 0% to 100 %.
Highlights
The purpose of this study was to clarify, whether and how the media distribution in the pore space of reservoir rocks impacts the physical parameters’ measurements in the well logging.It was noted during the tests on the samples, that there were significant differences in wave velocity behavior with increasing and decreasing water sample saturation
The structure B is located on the northern foreland Maćkowice gas deposits that lie in the eastern part of the Carpathian Foredeep, northwest of Przemyśl (Fig. 1)
Borehole B-4 was located in a place, where on the map of seismic attributes, an object of increased amplitude is distinguished, which may be due to gas saturation (The geological project in the area of B, PGNiG, Jasło, 2006)
Summary
The purpose of this study was to clarify, whether and how the media distribution in the pore space of reservoir rocks impacts the physical parameters’ measurements in the well logging. It was noted during the tests on the samples, that there were significant differences in wave velocity behavior with increasing and decreasing water sample saturation. A “hysteresis” velocity in the range of 30–90% (SW) (Endres & Knight 1989) was observed It was concluded, that the cause of such changes in the elastic parameters, at the various techniques of saturation with water, and air samples, may be changes in the geometrical distribution of liquid and gas phase in the pores of the rock.
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