Abstract
We present the developed theoretical-empirical technique for predicting of rocks’ oil-and-gas bearing in wells sections according to acoustic logging (AL) and core research (CR) and its variants by using data of other loggings and also the results of testing them on wells sections data in the Western oil and gas bearing region of Ukraine (WOGR). The mathematical apparatus of the created technique is based on a mathematical model of solid porous rock, empirical relationships between elastic and reservoir characteristics of rocks and acoustic logging data for specific studied wells. The key parameter in the calculations is the rock compressibility. Determination of the porosity of rocks and prediction of the type of pore filler (water, oil, gas) is implemented by comparing the results of calculating the velocities using theoretical and constructed empirical relationships with the actual data of the AL, by the parameter of compressibility of rocks, by the density of the pore filler fluid. Additional versions of the technique have been developed based on correlation dependences and data from other logging methods — gamma-ray logging (GL), electric logging (EL/SP), offset method and seismic logging (SL). They are used in case of absence of AL data for the studied wells or for the intervals of their sections, and also for improving the reliability of prediction the oil and gas content of these sections. The software for the implementation of the technique was developed in Fortran, C# and Excel software environments. The technique was tested on the data of wells of a number of structures of the WOGR of Ukraine (Lishchyns’ka, Buchats’ka, Ludyns’ka, Zaluzhans’ka, Zarichnyans’ka and Nyklovyts’ka).The technique ensures reliable prediction of petrophysical characteristics, porosity and oil-gas-water saturation of rock layers of different thicknesses (including thin layers — from 0.1—0.2 m) in well sections. For this, in addition to the data of the general parametric base of the WOGR reservoir rocks, the specially constructed refined empirical relations for various specific types and subtypes of the WOGR reservoir rocks are used, they are based on the results of analysis of petrophysical characteristics of those rocks.
Highlights
We present the developed theoretical-empirical technique for predicting of rocks’ oiland-gas bearing in wells sections according to acoustic logging (AL) and core research (CR) and its variants by using data of other loggings and the results of testing them on wells sections data in the Western oil and gas bearing region of Ukraine (WOGR)
Since our special studies have shown that the logarithmic dependence of compressibility on pressure has a better agreement with the real data than power equations, empirical formulas have been constructed in the form of a logarithmic dependences of compressibility on pressure for varieties of WOGR’ sandstones
This paper presents a new theoretical and empirical technique for predicting the elastic characteristics and the oil, gas or water content of well sections according to acoustic logging data, as well as its variants by using data from other logs of the studied wells, by applying the compressibility parameter of rocks as the key parameter
Summary
Distinguishing oil and water by the density of the fluid as a pore filler. The density of reservoir water is known to be 1000—1150 and even up to 1450 kg/m3, due to impurities of salts; the density of oil/gas condensate in layer conditions reaches 600—850 kg/m3. The prediction of elastic parameters, the coefficient of porosity, the pore filler (for layers of 0.2 m thickness) in the section of This well in the basic version of the technique and gamma-logging [Skakalska, Nazarevych, 2015a,b] are in a good agreement with the data of industrial geophysics [Kurovets et al, 2012]. To improve the reliability of predictive estimates for the theoretical-empirical technique, empirical relations for a number of specific types and subtypes of reservoir rocks available in the sections of the corresponding wells were investigated and established in addition to statistical studies of relations for the general parametric base of the WOGR For this purpose, the data were used for the compressibility of varieties of sandstones of WOGR for different depths/.
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