Reservoir Features of the Upper Carbon Sediments (Runovshchynska Area of the Dnieper-Donets Basin)

Paper concerned the research of elastic and electric properties of consolidated terrigenous rocks of Cambrian period of the southern slope of the Lviv Palaeozoic trough. The purpose of the research was to study the petrophysical parameters of the consolidated reservoir rocks (siltstones and sandstones), as the basis of the integrated analysis of their physical properties. The research looked at electric and elastic parameters of terrigenous rock samples, resistivity and formation resistivity factor, formation resistivity enlargement factor, velocities of the P-waves and interval (transit) time in atmospheric and reservoir conditions. Correlations between resistivity and formation resistivity factor, and between porosity and formation resistivity factor of consolidated rocks were established in atmospheric and reservoir conditions. The correlation between the resistivity and formation resistivity factor manifest itself in linear function. Physical modeling of reservoir conditions allows adapting the values of electrical parameters obtained in atmospheric conditions to parameters of rocks in reservoir conditions. Laboratory acoustic study of rock samples managed to establish correlations of: velocities of the P-waves and interval (transit) time with density and porosity in atmospheric conditions; velocities of the P-waves in atmospheric and reservoir conditions; velocities with porosity in reservoir conditions. The correlations between velocities of the P-waves in atmospheric and reservoir conditions for the studied rocks manifested itself in linear function. Physical modeling of reservoir conditions allows adapting the values of elastic parameters obtained in atmospheric conditions to parameters of rocks in reservoir conditions. The correlations between the electric and elastic properties and reservoir properties of siltstones and consolidated sandstones should be at the basis of preliminary interpretation of geophysical well logging on prospective areas of the southern slope of the Lviv Palaeozoic trough.

Electric and Elastic Properties of Consolidated Terrigenous Rocks of Cambrian Period of the Southern Slope of the Lviv Palaeozoic Trough

Vyzhva,

Onyshchuk,

Onyshchuk

et al. 2023

Lower Permian Carbonate Deposits Reservoir Parameters of Western Part of Hlynsko-Solohivska Area of Dnieper-Donets Depression Gas-Oil-Bearing District

Vyzhva

Onyshchuk

et al. 2020

The paper concerns the researches of the Lower Permian carbonate deposits reservoir properties of western part of Hlynsko-Solohivska area of gas-oil-bearing district of Dnieper-Donets depression. Such reservoir parameters as the open porosity factor, permeability coefficients and residual water saturation factor have been used to assess the promising rocks for the possible hydrocarbon reservoirs. Void structure of rocks with capillarimetric method and the correlation of rock density with their porosity were also studied. The porosity study was carried out in atmospheric and reservoir conditions. The bulk density of dry rock samples varies from 2212 kg/m3 to 2593 kg/m3 (mean 2413 kg/m3), water saturated rocks – from 2442 to 2642 kg/m3 (mean 2549 kg/m3), kerosene saturated rocks – from 2400 to 2622 kg/m3 (mean 2541 kg/m3); an apparent specific matrix density – from 2718 to 2828 kg/m3 (mean 2783 kg/m3). The open porosity coefficient of study rocks, saturated with the synthetic brine, varies from 0.045 to 0.181 (mean 0.127), if samples are saturated with kerosene then it varies from 0.049 to 0.184 (mean 0.128) and when N2 is used - from 0.063 to 0.217 (mean 0.149). The effective porosity has following values: 0.004-0.125 (0.036), and the residual water saturation factor - 0.4-0.97 (0.79). Analysis of reservoir conditions modeling revealed that porosity coefficient varies from 0.040 to 0.169 (mean 0.118). Due to the closure of microcracks under rock loading reduced to reservoir conditions the porosity decreases in comparison with atmospheric conditions, which causes a relative decrease in the porosity coefficient from 1.5 % to 11 % (mean 9.0 %). Capillar void of study rocks describes the prevalence of subcapillar pores (40-97 %, mean 79 %) while the overcapillars pores have range 1-22 % (mean 7 %) and the capillar pores - 2-38 % (mean 14 %). The permeability coefficient varies from 0.038 fm2 to 1.992 fm2 (mean 0.323 fm2). As result of petropysical researches the rocks have been classified with above mentioned reservoir parameters. The correlation analysis has allowed to establish a series of empirical relationships between the reservoir parameters (density, porosity coefficient, permeability coefficient and residual water saturation factor).

Electrical and Acoustic Parameters of Lower Permian Carbonate Rocks (Western Part of the Hlynsko-Solokhivskyi of Gas-Oil-Bearing District of the Dnieper-Donets Basin)

Vyzhva

Onyshchuk

et al. 2020

The main objective of this article is to study electrical parameters of Lower Permian carbonate rocks of Western part of the Hlynsko-Solokhivskyi gas-oil-bearing district of the Dnieper-Donets Basin (DDB) in normal (atmospheric) and modeling (reservoir) conditions. In atmospheric conditions it has been revealed that the resistivity of dry extracted limestones (the specific electrical resistivity of framework of grains was measured) varies from 12.147 kΩ⋅m to 111.953 MΩ⋅m (mean 1.542 MΩ⋅m). The resistivity of saturated limestone samples with kerosene varies from 44.478 kΩ⋅m to 14.449 MΩ⋅m (mean 1.435 MΩ⋅m). The resistivity of dry and saturated with kerosene samples is almost the same. The resistivity of limestones saturated with model of reservoir water (salinity M = 190 g/l) is lower and varies from 1.11 Ω⋅m to 23.16 Ω⋅m (mean 3.12 Ω⋅m). It has been determined that formation resistivity factor of limestones in atmospheric conditions varies from 13.5 to 230 Ω⋅m (mean 32.5 Ω⋅m). In addition to resistivity, the parameter of relative permittivity of investigated limestones was studied. It was determined that relative permittivity of dry limestones varies from 3.0 to 7.5 (mean 4.2). Relative permittivity saturated samples of limestones with kerosene varies from 2.8 to 8.8 (mean 4.5) and practically does not differ from dry ones but significantly lower than values of samples saturated with model of reservoir water (from 655 to 9565, mean 4280). That means when pores of limestones are saturated with NaCl solution their relative permittivity increases rapidly – from hundreds to thousands times (on average 944 times). It can be explained by the high conductivity of model of reservoir water. Limestones saturated with NaCl solution have velocities of P-waves in the range from 3346 m/s to 4388 m/s (mean 4030 m/s), and velocities of Swaves – from 1753 m/s to 2121 m/s (average 1942 m/s). If rocks are saturated with kerosene then velocities have strictly higher values – P-waves from 3433 m/s to 4514 m/s (mean 4011 m/s) and S-waves – from 2137 m/s to 2464 m/s (average 2344 m/s). Physical modelling of reservoir conditions (temperature 50 °С, pressure 30 MPa) showed that the specific electrical resistivity varies from 0.81 Ω⋅m to 13.19 Ω⋅m (mean 2.67 Ω⋅m), and limestones – from 0.49 Ω⋅m to 7.81 Ω⋅m (mean 1.95 Ω⋅m). Also, "specific electrical resistivity – pressure" connection was investigated. Due to the closure of microcracks and the deformation of the pore space, the electrical resistance of rocks increases with increase of pressure. The regression dependence of the formation resistivity enlargement factor with pressure for the studied rocks has a linear character. It was determined that in reservoir conditions the range of the formation resistivity factor for limestones varied from 17.3 to 271.9 Ω⋅m (mean 50.7 Ω⋅m), and range of variation of porosity coefficient was from 0.040 to 0.169 Ω⋅m (mean 0.118 Ω⋅m). The comprehensive analysis of petrophysical data has been resulted in a set of correlation ratios between reservoir, electric and elastic parameters of studied limestones in normal and modeling conditions.