Год издания: 2014

Finding water-oil rations in a saturated porous reservoir by means of EM logging is established on the possibility of imaging the dielectric spectra by the borehole inductive probe, identification of the components of the reservoir from these dielectric spectra, and determination of the water-oil ratio and porosity from the relaxation parameters. To find the water-oil ratio and porosity in the reservoir using dielectric spectroscopy, the mixing formula is often used. This formula expresses the complex dielectric permittivity via complex dielectric permittivities of the subsystems. Such a formula works in the MHz frequency range of the electromagnetic field. However, there are many problems associated with applying the mixing formulae. First, relaxation parameters of the Maxwell-Wagner polarization for the watersaturated porous media often fall outside of the domain where the Maxwell-Wagner polarization exists in reality and, as a result, the mixing formula is deemed inapplicable. Second, the number of relaxation parameters of the water-saturated porous medium (e.g. in the case when the formation is saturated with both water and oil) is typically lower than the number of dielectric degrees of freedom for the subsystems. Therefore, alternative methods are necessary to calculate bulk fractions of the subsystems present and formation porosity. The lab study of dielectric spectra of sandstones and dolomites saturated with a water-oil mix demonstrates that elements of a qualitative difference between a water-saturated reservoirs can be introduced to that saturated with a water-oil mix using the acoustic frequency range of the electromagnetic field. This difference is from the huge values of dielectric polarization unrelated to the Maxwell-Wagner polarization. This paper shows that Havriliak-Negami dielectric spectra enable the introduction of a natural measure of water saturation in the samples saturated with a water-oil mix find the water-oil ratio. As a result, the universal dependence for finding porosity of the samples saturated with a water-oil mix is used. Knowledge ofa priori information regarding the material content of the reservoir is not necessary. The water-oil ratio and porosity depend exclusively on the Havriliak-Negami polarization parameters, which can be found univalently from the characteristic values of the parameters of the measured dielectric spectra.