SU1695176A1 - Method of determining relative phase permeabilities of a porous medium - Google Patents

Abstract

The invention relates to engineering and geological research and m. used in various technological processes in which porous media (PS) and liquids with different physical properties are involved. The goal is to increase the efficiency of permeability determination by increasing the volume and reliability of the information obtained on the hydrodynamic parameters of the studied medium by taking into account the influence on these parameters of a three-dimensional character and heterogeneity of the structure of the pore space. Initially, the average length of the interpore distance in the PS under study is determined. Simultaneously with measuring the capillary pressure between the filtering phases with different physical properties, at each saturation value of the medium with a wetting fluid, the electrical conductivity of the investigated volume of this PS is measured at each saturation value of the PS with a wetting fluid. The relative phase permeabilities are determined from the obtained dependences of capillary pressure and electrical conductivity of the PS volume under study on its saturation with the wetting liquid and the average interpore distance in the PS under study. The relative phase permeability set by calculating the formula for a given Q, 1 CF f-crystals, 6 Il.HF 01

Description

Xi on

The invention relates to engineering and geological, hydrogeological and geophysical studies and can be used to justify the development of metal ore deposits by the method of underground leaching, oil and gas deposits by the method of areal displacement, the construction of various structures, roads and land-improvement systems, as well as in various technological

processes involving porous media and liquids with different physical properties.

The purpose of the invention is to increase the efficiency of determining the phase permeabilities of porous media by increasing the volume and reliability of the obtained information on the hydrodynamic parameters of the studied medium by taking into account the influence on these parameters of a three-dimensional character and heterogeneity of the pore space structure.

The idea of the structure of the feather space as a three-dimensional spatial grid of capillaries determines the period of this grid, i.e. average length of interporous distance d. If in the one-dimensional model the length of the pore channels is assumed to be infinite, then to determine the nature of the motion and distribution of the phases in the grid of intersecting capillaries, it is required to know its period d. The determination of d should be carried out before measuring the dependences of capillary pressure on the saturation of the medium PK (S) and on the electrical conductivity on the saturation of the medium a (s), so that subsequent effects on the porous medium (for example, injection of mercury) will not change the geometric parameters of the unperturbed porous environment. Conducting the conductivity measurement simultaneously with the measurement of capillary pressure provides information not only about the pore-node subsystem, which is characterized by PK (S), but also about the p-bond subsystem.

The change in capillary pressure with a change in the saturation of any phase reflects the process of phase redistribution in the pore space. At the same time, the change in saturation will reflect the change in the number of large nodes filled with this phase. A change in the number of pore channels filled with this phase cannot be judged by the change in Pk (5).

At the same time, the number of such capillaries filled with this phase and participating in the formation of conductive channels for it can be judged by the electrical conductivity of the medium under study at a known saturation.

Both the electrical conductivity and the hydroconductivity of any chain of capillaries filled with liquid is determined primarily by the thinnest capillaries. Therefore, a change in the conductivity of the medium with a change in saturation means that a part of the capillaries with the smallest radii, which previously contained an electrically conducting fluid, now do not contain it. Thus, by changing the electrical conductivity, it can be monitored that the capillaries of which radius at a given saturation contain an electrically conductive liquid and, accordingly, conduct not only electric current, but are also hydroconductive for this liquid,

Therefore, measuring simultaneously PK (s) and cr (s), we obtain information on substantially different-scale subsystems of pore-nodes and pore bonds in a porous medium that is non-uniform in terms of the structure of the voids forming it. Moreover, measurements of capillary pressure and electrical conductivity of the medium should be carried out simultaneously rather than in an arbitrary sequence, since the process of measuring PK (S) for a given volume of medium (for example, by the method of injecting mercury) makes it impossible to reuse the studied volume of medium. This increase in the amount of information received allows

take into account the heterogeneous nature of feather space,

Using for determining the relative phase permeabilities ki (s) from measured values of capillary pressure, electrical conductivity and average length of interpore distance allows to take into account the information on the heterogeneity of the pore space structure, as well as its three-dimensionality. In this case, the pore space is not represented as a bundle of linear one-dimensional capillaries of different radius, but as a three-dimensional spatial grid, in the nodes of which

pores connected by porous channels (capillaries) of different radius are located.

Figure 1 and 2 shows typical examples of thin sections of cores, respectively, of granular and cavernous porous media, reflecting the structure of their pore space; FIG. 3 shows a model of a pore space in the form of a three-dimensional grid consisting of pore nodes and pore bonds:

Fig. 4 shows a scheme for measuring the values of Pk and o in the process of forcing into the test volume, previously saturated with a wetting fluid (for example, air), mercury; in Fig. 5, the curves of dependencies PK (S) and cr (s) constructed on the results of measurements (curve 1 - PK (S), curve 2 - a (s)); Fig. 6 shows the relative phase permeabilities obtained by applying the proposed method (ki (s) curve 1 and kg (h) - curve 2).

The method is carried out as follows.

Initially, the initial parameters of the investigated volume of the porous medium and the filtering phases are determined by known methods: porosity t, length L and area of section F of volume A by direct measurement, specific conductivity of mercury ae, coefficient of surface tension

The mercury boundary is air y and the wetting angle of the capillary surface with mercury in the presence of air is 0- according to reference books. Next, the average length of the interporous distance d is determined from the sample of the undisturbed initial test material. After this, volume A is included in an electrical circuit with a current source B t as shown in Fig. 4, this allows determining its conductivity Cr I / V, where the current is measured by an ammeter A, and the voltage drop V is measured by a voltmeter V. Then Capillary pressure is measured at various saturations, for example, by injecting mercury, and simultaneously with the measurement of Pc, the electrical conductivity of volume A is measured using the indicated circuit, as well as after completion of the injection of the next portion of mercury. When implementing this method, the capillary pressure can be determined in various ways: by injection of mercury, impregnation in the gravitational field, forced impregnation, centrifugation. The corresponding measured values of a for convenience of further use are also plotted on the cr-s plane, where the values of s with the interval s / (m A) are plotted along the abscissa axis and a are shown along the ordinate axis (curve 2 in Fig. 5). Having measured for this porous medium, the capillary pressure values Pk (g) of the electrical conductivity of the volume A-g (g) and the average length of the interporous distance d determine the relative phase permeabilities: ki (s) for the wetting fluid, K2 (g) -d non-wetting.

The phase permeability is then determined by the ratio

W 7lF (rcl) -F (Of 9 1 - F (OG 0 (P) (D SG, d) dr al ...

(rci) -F (r) P9 i - F (r) (g) r1 atf (r, a. d) dr

1-1,2,

where 1 1 in the case of a wetting fluid, I 2 - for non-wetting; s - saturation of the medium with a wetting liquid, fractions of units;

Q (n) (r, cr, d) Ј aj (a (s)) - polynomial

nth degree, whose coefficients are functions of the electrical conductivity cr (s) and the average length of the interpore distance

d. ,,

F (r) is primitive Cr (r, 7, d), and F (r) is inverse to F (r);

Fi (r) - primitive QCn) (r, cr, d)

O (s) is the electrical conductivity of the investigated volume of the medium, measured in the experiment, cm;

d — average length of interporous distance in the porous medium under study, m; d - dumb is variable;

31 O, 32 2 ycosQ / PK (s); PK (S) —capillary pressure, measured in experiment, Pa; y is the surface tension coefficient at the interface of filtering phases, n / m; Q — wetting angle, hail; rc ((Bi) -1/4, m;

Bi, B2 a2.

Claims (1)

Claims 1. A method for determining the relative phase permeabilities of a porous medium, including measuring the porosity of a medium, saturation with its wetting fluid and capillary pressure between the filtering phases with different physical properties at each saturation value of the wetting medium fluid and the dependence of capillary pressure on the saturation of the medium with a wetting fluid is the calculation of relative phase permeabilities, characterized in that, in order to increase permeability determination by increasing the volume and reliability of the information obtained on the hydrodynamic parameters of the medium under study by ensuring that These parameters of three-dimensional nature and heterogeneity of the structure of the pore space, initially determine the average length of the interpore distance in the porous medium under study, simultaneously with the measurement of the capillary The pressure between the filtering phases with different physical properties at each saturation value of the medium with a wetting fluid is measured by the electrical conductivity of the investigated volume of the porous medium also at each saturation value of the medium by the wetting fluid, and the values of relative phase permeability are determined by the dependences of capillary pressure and electrical conductivity. of the investigated volume of the medium from its saturation with a wetting fluid and the average length of the interporous distance in the study my five porous medium. 2, the method according to claim 1, characterized in that the relative phase permeabilities are established by calculating the ratio kl (3) (r) (0 1-F 0r1a (n) (r, ad) dr (rq) -F (((d) G1 Q (r.ad) dr 1-1.2 where I 1 for a wetting fluid; 1 2- for non-wetting fluid; s is the saturation of the medium with a wetting fluid (fraction of units), Q (n) (r, a, d) 5 ar (cr (5)) is a polynomial The nth degree, the coefficients of which are functions of the electrical conductivity o (s) and the average interporous distance d: FIG L Fig Fig.Z 0 five F (r) is primitive, a, d); Fi (r) - primitive (r. Cr, d) a (s) is the electrical conductivity of the investigated volume of the medium, measured in the experiment, Cm; d - average length of interporous distance in the porous medium under study, m; g-nem is variable; 31 0; 32 2 ycosQ / PK (s); PK (S) —capillary pressure, measured in experiment, Pa; y is the surface tension coefficient at the interface of filtering phases, N / m; Q — wetting angle, hail; rC | (Bi) -1/4, m; B1 AG1; B2 a2. L Nd F. Voytsh FigL ; five FIG. five