Разработан и в лабораторных условиях на слоистых образцах из искусственного геоматериала апробирован экспериментальный метод, позволяющий в рамках модели среды с двойной проницаемостью определить параметры, контролирующие процессы миграции флюидов и пороупругое деформирование трещиновато-пористых породных массивов - трещинную проницаемость k1 и коэффициент массообмена β, а также их зависимость от напряжений σ. Предложена и реализована процедура испытаний: при ступенчато возрастающем нормальном напряжении σ измеряются стационарные расходы Q1(σ) и Q2(σ) в трещиновато-пористом образце квазирегулярной структуры при заданном перепаде давления: по стандартной схеме (Q1) и закрытых трещинах на торце (Q2). Создана математическая модель эксперимента, получено аналитическое решение задачи о стационарной фильтрации: распределение давления в трещинах и матрице, зависимость расходов от σ. Представлен алгоритм для интерпретации данных эксперимента - расчета k1 и β по зарегистрированным расходам Q1 и Q2. Показано, что проницаемость k1 пропорциональна σ -2, а β практически не меняется. The experimental procedure is developed and tested on a laboratory scale and using layered samples of manmade geomaterials. Within the dual-permeability model, the procedure enables determining parameters that govern fluid flow and poroelastic deformation in fractured porous rock masses, namely, fracture permeability k1 and mass transfer coefficient β, as well as their dependence on stresses σ. The testing procedure is proposed and implemented. In the procedure, under the stepwise increasing normal stress σ, the stationary flow rates Q1(σ) and Q2(σ) are measured in a quasiregular fractured porous sample at the preset pressure difference: using a standard setup (Q1) and in closed end-face fractures (Q2). The mathematical model of the experiment is constructed, and the analytical solution of the problem on stationary flow is obtained: pressure patterns in fractures, and stress-dependence of flow rates. The experimental data interpretation algorithm enables calculating k1 and β by the recorded flow rates Q1 and Q2. It is shown that the permeability k1 is proportional to σ -2, and β remains almost unchanged.

The authors show that data on characteristics of drill mud penetration zone improve reliability of geoinformation obtained from borehole geology and geophysics. The developed procedure for the data interpretation takes into account the geomechanics and hydrodynamics of drilling. A part of the drill mud penetration zone is represented by mudcake which prevents direct measurement of porosity and permeability. The article describes the experimental studies on growth of the mudcake on the samples of low-permeable sandstone from the Jurassic reservoir rock mass using an original facility. The petrophysical nonuniformity of the mudcake was determined. The repeated measurements revealed the mudding zone.

The experimental procedure is developed and tested on a laboratory scale and using layered samples of manmade geomaterials. Within the dual-permeability model, the procedure enables determining parameters that govern fluid flow and poroelastic deformation in fractured porous rock masses, namely, fracture permeability k_1 and mass transfer coefficient β , as well as their dependence on stresses σ . The testing procedure is proposed and implemented. In the procedure, under the stepwise increasing normal stress σ , the stationary flow rates Q_1(σ) and Q_2(σ) are measured in a quasiregular fractured porous sample at the preset pressure difference: using a standard setup ( Q_1 ) and in closed end-face fractures ( Q_2 ). The mathematical model of the experiment is constructed, and the analytical solution of the problem on stationary flow is obtained: pressure patterns in fractures, and stress-dependence of flow rates. The experimental data interpretation algorithm enables calculating k_1 and β by the recorded flow rates Q_1 and Q_2 . It is shown that the permeability k_1 is proportional to σ^-2 , and β remains almost unchanged.

Program for modeling the growth of mud cake with taking into account its changes of filtration-capacitive by thickness parametres has been developed, taking into account its changes of filtration-capacitive by thickness.The usage of the program, when compared with experimental data, allows to determine the parameters of the equations describing the change in porosity and permeability of the mud cake during its growth caused by a change in pressure on the cake.

This article deals with the topical problem of estimating water content in water–oil mixtures within porous media they saturate, according to low-field NMR relaxometry and dielectric spectroscopy. The aim of the research is experimental validation of the capability of complex data interpretation to acquire information on the filtration-volumetric properties of drill cuttings, relaxation characteristics of oil-containing fluids, the water/oil ratio in water–oil mixtures, and their saturation of drill cuttings to control the composition of liquids produced from boreholes. The studies are carried out on samples of cuttings and oils taken from fields in the Northern regions of the West Siberian oil-and-gas province, where NMR studies have not been performed before. Based on the experimental data obtained, the possibility of water content assessment in water-in-oil mixtures and porous media they saturate were proved through NMR relaxometry. With the use of the proposed methodology, the amount of water in oil–water mixtures was established, and their main NMR characteristics were determined. The relative error in evaluating the proportion of water in mixtures based on high-viscosity oils is less than 10%, and about 20% for those based on light oils. When determining the oil–water ratio in the pore space of the drill cuttings, the error is about 15%. It was proven that joint use of these two techniques makes it possible to increase the reliability of the oil–water ratio assessment of all the samples studied. Furthermore, it was revealed that the NMR spectrum shifts to the right, and the spectrum of the complex permittivity shifts downwards during the transition from high-viscosity oils to light ones.

Theoretical substantiation and lab tests of the method for synthesis of a relationship describing angular anisotropy of the effective permeability in borehole environment based on the inverse coefficient problem solution in terms of the data on percolation tests of regularly non-uniform cylindrical specimens with a central hole are set forth in the paper. With a view to provide the algorithmic support of GIS data inversion in the course of determination of poroperm properties of production intervals the researchers developed and implemented by the hybrid numerical method to realize the multiphysical model of the evolution of geomechanical and electrohydrodynamic fields under filtration of multiphase fluid in the borehole environment with consideration for anisotropy of permeability induced by difference in components of the external stress fields. The numerical experiments enabled to establish that in the overbalanced drilling the configuration of invaded zone depends on the proportion between horizontal stress components outside of the well influence zone.

The database of relaxation characteristics of core samples from the parametric well was created. It includes their main petrophysical parameters, the NMR signal and the results of its processing and interpretation. A comparative analysis of the obtained data with the results of lithological and stratigraphic analysis was carried out. Using the example of a parametric well, it is shown that NMR data can be used to quickly obtain information on the distribution of reservoir properties of core samples both along the section as a whole and separately for each suite.

Using the geophysical and hydrodynamic compatibility model allows to reduce ambiguity of the solution of the inverse problem and to increase the reliability of productive layer parameters definition. It includes the parameters of permeability and porosity of the filter cake, which significantly affect the result of filtration modeling, but are not determined during the drilling. To investigate the process of formation of a mud cake, to study its properties and to determine the main parameters, the authors of the article carried out a series of experiments on a setup assembled at IPGG SBRAS, on core samples of low-permeability sandstone extracted from the YUS collector. The results of experiment with core samples from the Tevlinsko-Russinskoe and Russinskoe oil fields.

The spectral-induced polarization (SIP) response of porous materials at frequencies below 1 kHz can be used to determine the pore size and rock permeability. Although the results of certain studies are encouraging, in recent years it has been argued that there cannot be a universally applicable approach to predict permeability using the SIP response. This article proposes a broadband dielectric spectroscopy method in the frequency range from 100 Hz to 500 MHz for assessing the permeability and average pore size. An original experimental setup has been developed that makes it possible to measure the dielectric spectrum of quartz-based consolidated sedimentary samples of porous rocks in this frequency range. The rock samples with permeability from 0.17 to 206 mD and an average pore size from 6.3 to 21.1 mu m have been studied during the experiments. The dielectric spectra of four sandstone samples and two siltstone samples moistened with distilled water and a NaCl solution with a con-centration of 1.5 and 4 g/L were measured. The volume fraction of the solution in the samples varied from complete saturation to a moisture of 0.04-0.05 m3/m3. The dielectric spectra were modeled by three relaxation processes, the parameters of which were determined using the Debye and Cole-Cole formulas. The strength of two low-frequency processes with the relaxation times of about 1.2 ms and 0.15 ms are well correlated with the low-frequency conductivity of the samples; however, no stochastic dependence on the pore size and permeability was found. The parameters of the high-frequency relaxation process with the relaxation times of tens and hundreds of nanoseconds depend both on the solution ratio in the sample and its concentration, as well as on the pore size and permeability. The strength of this process is better related to the pore size and permeability when moistened with distilled water, and the relaxation time correlates best with them when using the solution with a concentration of 4 g/L. No significant differences in the process parameters in the samples of sandstone and siltstone were found.

The method for correlation of poroperm properties and effective stresses in weakly coherent rocks has been developed and tested on a lab scale. An appropriate lab testing installation is designed and manufactured; it includes a hydraulic press, a system of force plungers, a polyurethane measurement cell to be filled with sized sand, a compressor and a high-precision autonomous measurement system for fluid flow rate and pressure. The method consists in sequential steady-state and unsteady-state flow tests of a granular geomaterial sample placed in the measurement cell where nonuniform stress state generated by application of the external load to the cell. In the unsteady-state flow tests, the change in pressure was measured during gas release from the cell. In the steady-state flow tests, the flow rates were measured at the varied input pressure. The measured flow rates and pressures were used as the given data in the inverse coefficient problems on determinations of the empirical parameters in the exponential dependence of porosity, permeability on effective stress. Resolvability of the formulated inverse problems within the nonlinear models of mass transfer in a granular media is demonstrated.

The process, justified by theory and physical modeling, enables to establish dependence of poroperm properties of loose geomaterials versus fluid pressure and stresses. The laboratory unit designed and manufactured by researchers, comprises a measurement cell filled with a loose material, a hydraulic press, and a recorder of pressure, flow rate, and stress $$ \sigma_{m} $$ , stepwise applied to the cell. At each loading stage the permeability test was carried out at different input gas pressures $$ p_{n} $$ . The stationary measured flowrate data $$ Q_{mn} $$ and the back analysis were employed to establish the empirical permeability–effective stress dependence, followed with approximation by two-parameter exponential function. The measurement cell was vacuumized at fixed $$ \sigma_{m} $$ the cell was connected to a vessel, filled with air of a preset mass. Porosity $$ \varphi_{m} $$ was calculated based on the equilibrium pressure gained in “cell–vessel” system. The experiments performed with the medium-grained sand revealed that the exponent factor characterizing the relationship between permeability and effective stress is something like 0.02 bar−1; the permeability–porosity relation can be described by a power function; thereto, Kozeny–Carman equation is fulfilled with good precision as well.

The paper presents the results of experimental studies of the dielectric and NMR characteristics of drill cuttings. It is shown how the fluid distribution in the pore space changes at different stages of extraction and saturation. It is shown that it is possible to estimate the degree of saturation of samples by sequential interpretation the spectra of the dielectric and NMR characteristics.

Summary The results of the study of drill cuttings samples saturated with a water-oil mixture by the methods of dielectric spectroscopy and NMR-relaxometry are presented. It is shown that the cooperative interpretation of these methods results makes it possible to estimate the content of water and oil in the samples of saturated drill cuttings. The NMR relaxometry method is well-behaved method in the study of water-in-oil emulsions. Emulsions based on viscous oils are characterized by bimodal spectra of transverse relaxation times, based on light oils - unimodal or with a slight inflection. It is possible to determine with high accuracy the content of water and oil in the emulsion from the amplitudes of the NMR spectra.

The article presents the results of studies of petrophysical properties and the study of samples by the method of nuclear magnetic resonance (NMR). The measurements were carried out on a collection of artificial core samples with different grain sizes. The procedure for preparing the samples is described, and the comparison of the results of measuring the petrophysical properties by different methods is given. The quantitative relationships between the size of the sand grains from which the samples are made, the filtration-capacity properties and the distribution of the relaxation times of the NMR spectrum of the samples are investigated.

The purpose of the study is to extend the use of nuclear magnetic resonance relaxometry and dielectric spectrometry methods. This is realized through a complex interpretation of the data by the above methods to timely provide additional petrophysical information about the drill cuttings pore space properties and structure. The relevance of the study is that the data on the drill cuttings obtained by the NMR method can be used as prior information in the logging data interpretation before a detailed petrophysical study of the core sample or in case of the core absence in the sampling interval. The objects of study are the drill cuttings samples from the fields of the West Siberian oil-and-gas province. The samples are saturated with different fluids, and their reservoir properties are determined by the nuclear magnetic resonance and dielectric spectrometry methods. As part of the experimental research, nuclear magnetic resonance investigations of the core samples of different discretization degrees have been carried out to determine the reservoir properties of the samples depending on the degree of their particle size reduction. It has been shown that the obtained results do not depend on the particle size of the measured sample and are consistent with the results of the standard petrophysical studies. The relationship between the porosity and the saturating fluid type has been established. Based on the data obtained by the dielectric spectroscopy method, the study has determined the value of the complex dielectric constant that shows how the degree of saturation changes depending on the fluid, and what happens in the pore space. The complex interpretation of the results obtained by the two methods provides additional information on the drill cuttings reservoir properties that can be used as a priori information on the formation properties.

The paper presents the results of an analytical review of the study properties rocks and their saturating fluids by dielectric spectroscopy, as well as experimental studies of their complex dielectric constant and NMR characteristics. The connection of the complex dielectric constant of oil with its geochemical properties and NMR characteristics is established.

Summary It is shown that the dielectric characteristics of the core samples depend on a number of petrophysical characteristics. As an example, the results of measurements of the complex dielectric permittivity (CDP) in the frequency range from 20 Hz to 120 MHz of three samples of sandstone cores with different average pore sizes are given. The measurements were carried out at different values of the level of saturation with distilled water. It is shown that two relaxation processes affect the frequency dependences of the CDP. The low-frequency process is caused by the polarization of the water-mineral interface, and the high-frequency process is due to the polarization of the water-air interface. The intensity of the high-frequency process strongly depends on the average pore size, increasing with pore size decreasing. The relaxation time increases with decreasing water saturation and weakly depends on pore sizes

Thermobaric tests are performed on Bazhenov oil-bearing shale containing above 10% of kerogen in view to determine its rheological properties. The test specimen under a statistical axial load is heated stepwise at temperatures \( T_{n} = 60 \), 100 and 150 ℃ with measurements of height \( H\left( t \right) \). The temperature is risen if relative velocity of \( H \) gets less than 0.05. Deformation of the specimen is described by Kelvin–Voigt model, within which the inverse problem is stated and solved to determine Young module \( E_{n} \) and effective viscosity \( \eta_{n} \) of rocks by \( H\left( t \right) \). The results of solution are approximated by two-parameter exponential functions, \( E = E\left( T \right) \) and \( \eta = \eta \left( T \right) \) relationships are established.

NMR studies of core samples of different disintegration degrees were carried out to determine their reservoir properties depending on the degree of size reduction. It was established that the results do not depend on the particle size of the measured sample and are consistent with the results of standard petrophysical studies performed on core samples. It is shown that the data operatively obtained on the drill cuttings by the NMR method can be used as initial information in interpreting production well logging before conducting detailed petrophysical core studies. The results of studying drill cuttings allow to obtain reservoir properties of productive layers even at intervals without core sampling.