SU1242613A1 - Method of evaluating strained state of rock - Google Patents

Description

one . 12426

The invention relates to mining and is intended to study the stress state of rocks in natural occurrence.

The purpose of the invention is to improve the accuracy of measurements,

FIG. 1 shows the waveform-N # 1 of the signals arriving at the receiver KHj in FIG. 2, the location of the receivers along the nepm-ieTpy well; in FIG. 3, a temporary hodograph when the fracture plane is oriented parallel to the axis of the well; FIG. 4 - the same, with the orientation of the fracture fracture plane at an angle to the axis of the well. - 15 The method is carried out as follows.

 The selected area of the well is isolated from the rest of the well with two special glands. 20 The space isolated by the glands is pressurized with fluid or special solutions. Fluid pressure rises to. the moment of hydraulic fracturing of rocks on the wall 25 of the well. At the moment of rupture. The pressure in the system abruptly decreases to a certain value at which the crack is in the open state. From the magnitude of the pressure of the liquid in the isolated space at the time of opening the cracks and the orientation of the plane of the cracks in the space, the stress tensor is calculated. To determine the orientation of hydraulic fracturing along the perimeter of a circular section of a well, at least equal spacings of receivers are located at equal distances, and each well of the receivers ring is spaced at a distance of no more than 1.5 times the borehole radius. Such a location of the receivers makes it possible to determine the orientation of the cracks in space with sufficient accuracy for experiments.

40

13 2

As a result of the injection of fluid into the isolated space, a high pressure develops in it and hydraulic fracturing occurs, which is the source of the acoustic waves converted by the receivers into an electrical signal.

The electrical signal from each receiver is amplified and fed in parallel to a multichannel high-speed high-frequency recorder and an electronic switch (EC), B the moment the first EC signal arrives, it includes a scanner of the recorder. The oscillograms obtained on the recorder determine the difference in the arrival times of the waves at the receiver (Fig. 1).

Using these data, a temporary hodograph is constructed (Fig. 3), from which the azimuth and angle of inclination to the axis of the working fracture well are calculated.

This example is given for the case of tp -j90, i 0 orientation of fracture cracks parallel to the axis of the well, where H is the azimuth of the plane of the crack, Jf is the angle of inclination of the plane of the crack to the axis of the well;

In the case of orientation of the crack plane at a certain angle to the well axis, the time hodograph will look like (Fig. 4), where I, II, III are 1,2,3 rings of the receivers, respectively.

The hodograph determines the average value of the slope of the curves from the expression

(S, 4 s,

 )

 about(.

3 - - с. The inclination angle of the plane of the crack to the bore of the well is determined by the formula

1 arcsin (tg oСрр)

The projection of point A on the V axis determines the azimuth of the normal to the crack plane.

f1 / g.

vt

ABOUT

f

Editor N. Dankulich

4

Compiled by G. Alekseev. . Tehred N. Bonkalo Proofreader E. Roshko

Order 3675/31 Circulation 470Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. 4/5

Production and printing company, Uzhgorod, st. Design,. four

Claims (1)

METHOD FOR EVALUATING THE STRESSED STATE OF ROCKS, including injecting fluid into the sealed interval of the well to a pressure leading to hydraulic fracturing of the rocks, and determining the orientation of the guide plane. the fracture, which is used to judge the direction of the larger component of the stress field, characterized in that, in order to increase the accuracy of measurements, the acoustic vibrations generated during the formation of the fracturing plane are recorded, using the receivers located in the sealed space of the well, its perimeter and height, the arrival times of acoustic waves of each receiver and their difference determine the orientation of the fracturing plane in space. SU 1242613 A1 1 12 '