SU1479635A1 - Method of determining rock seepage factor - Google Patents

Abstract

The invention relates to hydrogeology and can be used to estimate groundwater reserves. The goal is to increase the accuracy of the determination. Drilling test wells and measuring the flow rate and fluid level in the well over time. Bur t exploration wells. Select the core of the pilot and exploration wells. The modulus of fracture of rocks is determined. The effective pressure at the depth of coring is determined. The filtration coefficient of rocks by exploration wells is calculated using the above formula. The method allows to obtain additional information on the change in the filtration coefficient by the area of the aquifer. 2 tab.

Description

one

The invention relates to hydrogeology and can be used to assess groundwater reserves, to justify hydraulic engineering construction and drainage of mine and quarry floors.

The aim of the invention is to increase the reliability of determining the filtration coefficient of rocks.

The method is carried out as follows.

During the exploration of the field, the aquifer, represented by fractured rocks, is opened by several test and exploration wells. During the drilling process, core samples are taken from pilot and exploration wells;

which measures the thickness of the cracks. Samples are taken from the core at specified depths, which determine the density of rocks. After completion of drilling in test wells, test pumpings (or pouring) are carried out, based on the results of which, using known dependencies, filter coefficients of rocks of the aquifer under test are calculated. The obtained partial values of the filtration coefficients, modulus of fracture, taking into account the depths of the tested intervals, are subjected to statistical processing. Regression analysis methods determine the regression coefficients b and d in the equation

Ј

43

se co

SP

one

(

-L

(ABOUT

where KF - the filtration coefficient of rocks in experimental wells, m / day; С — coefficient depending on the geometry of cracks and their orientation relative to the filtration flow, m2- / day; M is the modulus of fracturing of rocks by well core, units / m; d and b are regression coefficients; a - coefficient of compressibility of rocks, units / Pa; P is the effective pressure at the depth of coring, Pa; RO - standard effective pressure, Pa.

Then, based on the values of the modulus of fracture, determined from the core of the exploration well, using the dependence

K C MpJj7 mTTi (P

Р Р d exp (-M) + b

)

where K. is the filtration coefficient of rocks exposed by a geological exploration well, m / day; C - coefficient depending on the geometry of cracks and their orientation relative to the filtration flow, m2 / day; M is the modulus of fracturing of rocks by well core, units / m; d and b are regression coefficients; d, is the coefficient of compressibility of rocks, units / Pa; P is the effective pressure at the depth of coring, Pa; PO — standard effective pressure, Pa; calculate the value of the filtration coefficient for the selected (aquifer interval, opened by a geological exploration well.

PRI me R. At the stage of detailed geological exploration of a magnesite deposit, the filtration coefficient of rocks was determined by experimental pumping from 68 wells (see Table 1).

The core of the experimental wells determined the modulus of fracturing of rocks (Table 2) and density.

i

At the magnesite deposit were

124 exploration wells were drilled, according to the core of which some 00

0

five

0 5 0 5

our modulus of fracture and rock density.

The results of determining the filtration coefficients and modulus of rock fracturing for the pilot wells were subjected to preliminary statistical analysis, which included: calculating the characteristics of empirical distributions; elimination of gross errors; checking the hypothesis of normality of distributions, if the hypothesis of normality of distribution is rejected, then we carry out the transformation of distribution to normal, test the hypothesis of normality of the transformed distribution.

The elimination of gross errors was performed using Student’s distribution. As a result, 3 values of the filtration coefficient and the modulus of rock fracturing were excluded.

The distribution normality hypothesis was rejected; therefore, the distribution of the filtration coefficient and the modulus of fracture was transformed by replacing K 1pK and M 1pM. After data conversion, the distribution normality hypothesis was tested by criterion x. The verification confirmed the hypothesis of the normal distribution of the transformed data.

The determination of the coefficients b and d in equation (1) is based on the additivity property of the logarithms of the filtration coefficients of fractured rocks, which was established as a result of research and is written as follows:

1PK 1PK (M) + 1PK (P),

(3)

where K is the filtration coefficient of fractured rocks, m / day; K (M) - the dependence of the filtration coefficient on the modulus of fracture; K (P) is the dependence of the filtration coefficient on the effective pressure. In equation (3)

K (M) CM (4)

and K (P) exp d (P-P0) 1

u.

The value of the coefficient C is determined by the formula (4) subject to the following condition:

K (M) K0 with M M0 (6

For magnesite deposit K0 0.695 and M0 11.8. Substitute the values of K0 and M0 in the formula (3) and, having solved it with respect to C, we obtain

C | ™ 0.0589 (m2 / day).

Further, for all tested intervals of the aquifer, taking into account dependence (3), we calculate the values of K (P). We denote:

1MM)

d exp (-M) + b

(7)

where (M) is the coefficient of structural weakening of rocks. In view of (7), equation (5) is written

We read as follows:

1pK (P) A (m) cl (rr).

(eight)

In equation (8), two unknown coefficients A (M) and oi. The coefficient tЈ is determined from the following condition:

MM) 1 when, (9)

where P is the effective pressure on

depth H, Pa.

In view of (9), equation (8) is written in the following form:

lnK (Pk) Ы (Pk Pfl).

(ten)

The effective pressure is calculated according to the following relationship:

Р (1-т) (Рс, - РЛ),

(P)

where t - fissure hollow rock, share, unit; Psk - pressure in the skeleton of the medium, Pa; RJ - pressure in fluid, Pa.

Under the conditions of a magnesite deposit, the numerical values of the parameters included in equation (10) are:

Ro 0, Pk 1.83 - I07 Pa, 1pK (Pk) - 4.828, p 0.05.

Substituting the values of the parameters and solving equation (10) with respect to 6i, we obtain

-T78f-To -2.64-107 (1 / Pa)

796356

We use the dependence (8) and for each tested interval of the aquifer calculate the value of A (M).

The regression coefficients b and d can be determined from the values of A (M) using the relationship (7). In this case, to determine 10 coefficients b and d, a system of two equations is sufficient. In fact, we obtain an overdetermined system of n equations with two unknowns, in which n is the number of determinations of the filtration coefficient of rocks. Therefore, the calculation of the coefficients b and d should be made, solving a system of equations:

n 1 and, - 1, - -Mi

20 2 l 7 d 2 e + nb;

T - k b

m

um

 -m-1 + b Zle

(12)

where Aj is the structural coefficient

attenuation for 1st determination;

M «is the modulus of fracturing of rocks for the 1st definition, units / m.

The regression coefficients calculated for the magnesite deposit have the following values: b 0.754 and d 0.583.

Thus, all coefficients included in equation (1) are determined for a magnesite deposit. Further, according to the values of the modulus of fracture, density of rocks, taking into account

the depth of the well and the aquifer, opened by the well, determine the filtration coefficients for the exploration wells.

The application of the proposed method

Claims (1)

It provides additional information on the change in the filtration coefficient over the aquifer distribution area due to the use of data on fracturing of rocks obtained from core geological exploration wells, increasing the accuracy of determining the filtration coefficient as a result, taking into account the effective pressure, reducing the volume of drilling and test-filtration works Invention Formula The method for determining the filtration coefficient of rocks, including drilling pilot wells, measuring the flow rate and fluid level in the well over time, characterized in that, in order to increase the accuracy of the determination, exploration wells are drilled, cores are taken from pilot and exploration wells, the rock fracture modulus is determined, the effective pressure at the depth of the core sampling, and the filtration coefficient of rocks by geological exploration wells is determined by the formula Table 1 TO CM exp (-M) + b ° (J de M and Kommersant P Ratio of filtration of rocks by exploration wells, m / day; the coefficient depending on the geometry of cracks and their orientation relative to the filtration flow, mg / day; modulus of rock fracturing by well core, units / m; regression coefficients; coefficient of compressibility of rocks, units / Pa; effective pressure at the depth of coring, Pa; standard effective pressure, Pa. Table 2 0 ABOUT 50 100 150 200 250 50 100 150 200 250 300 24 19 13 11 1 10 9 8 7 35 Total: 68