The thesis is dedicated to development of the 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 testing them to study geological sections of wells in the Western oil-gas bearing region (WOGR) of Ukraine.
The mathematical apparatus of the 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, by using the compressibility of rocks as the key parameter in the calculations. Mathematical calculations integrate the theoretical and the empirical relationships between the elastic parameters of rocks, taking into account the influence of the effective pressure (depth), porosity, the type of fluid – filler of the rocks’ pores. On their basis, the resulting predictive functional is built which is the main search tool for distinguishing the type of fluid (gas, oil or water) in the pores of rocks. By comparing the results of calculation of the body waves velocities on this functional with the actual data of AL, the type of the pore filler is predicted.
The created basic variant of the predicting technique provides a reliable definition of petrophysical characteristics, porosity and the type of fluid filling of rocks in sections of wells. In particular, the porosity of the rock layers determined by it, differs on the average by no more than ±5-6 % from similar results by other methods. This ensures the effectiveness of both the basic and additional variants of the predicting technique and also of additionally developed methods of separate studying of the rocks solid phase parameters (in particular, compressibility) and the subsequent prediction of the type of the rocks in the wells sections, and separate studying of the parameter of a fluid – pore filler (in particular, its density) and further refined distinction of the type of fluid (especially, the distinction between oil and water) in the reservoir rocks of the wells sections.
For the cases of absence AL data for the studied wells or separate intervals of their sections, and also for improving the reliability of the prediction of oil-and-gas bearing of these sections, the additional variants of the technique were made, which are based on the additional correlation dependences and the data of other logging methods – gamma-ray logging (GL), electric logging (EL/PS), offset method and seismic logging (SL).
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 Western oil-and-gas region of Ukraine (Lishchyns’ka, Buchats’ka, Ludyns’ka, Zaluzhans’ka, Zarichnyans’ka and Nyklovyts’ka). It ensures a reliable prediction of petrophysical characteristics and oil-gas-water saturation of rock layers of different thicknesses (including thin layers – from 0.1-0.2 m) in wells sections: the porosity, elastic modules and the type of the pore-filler by the data of AL (GL, EL/PS, SL).
The appropriate multiplicative components (corrections) for pressure and porosity in empirical relationships for compressibility were determined for different specific rocks. With their use the values of compressibility of rocks in wells sections were specified and the type of these rocks was identified by compressibility of their solid phase.
Analysis of petrophysical characteristics of different types and subtypes of reservoir rocks of WOGR was made, on their results specified empirical relations for those rocks were constructed, which significantly increase the reliability of predicting the oil-and-gas content in wells sections by the theoretical-empirical technique. A method to supplement of the parametric base of compressibility by the data on the velocities of the body waves of reservoir rocks was developed. Also a method of estimation of fracturing and permeability of rocks in the sublayers of wells sections was elaborated.
Key words: mathematical prediction; oil-gas-water-saturation of rock; petrophysical characteristics of rocks; well sections; acoustic logging; gamma logging; core research; Western oil-gas bearing region of Ukraine (WOGR).
