SU1298376A1 - Method of checking the size of crack formed by hydraulic rock fracturing - Google Patents

Abstract

The invention relates to the mining industry and is intended to determine the linear dimensions of the crack opening (T) around the squash (C). The goal is to improve the accuracy of determining the size of a single T fracture. For this, in C, crossing T, a fluid is injected (L) and the flow parameters J are changed. First, the dependence of the velocity F in T on the distance to C is measured. The boundaries T are determined by the location of the points where the velocity F is zero. . The dependence of the velocity W on the distance to C is determined by the time of occurrence in the control C, crossing the T dye supplied to C periodically. Next, measure the flow rate W in C. The T line is determined from the expression: h Q-2 ii r K (P) / / 2 u rVp, m. The average radius T is determined from the expression i:, p 4Q / 2irK (P), m, where r is the distance from the working C to the measurement point, m; h is the T reference at a distance g from C; V is the speed of movement Ж in T at a distance g from C, m / s; Q is the flow rate of F in C, K (P) is the filter characteristic of the rock, is equal to the flow of F through the unit surface T at a pressure F equal to the pressure F in C, m / s. 3 hp f-ly, 1 ill. g (L N3 CO 00 co

Description

The invention relates to the technique of monitoring the parameters of hydraulic fracturing of rocks, in particular, is intended to determine the linear dimensions of the opening of a fracture around a well.

The purpose of the invention is to improve the accuracy of determining the size of a single fracture of a fracture.

The drawing shows a scheme for monitoring the size of hydraulic fracturing of rocks.

The method is carried out as follows.

The method is based on the liquid found in the regeneration is filtered through

.

a study of the processes of hydraulic fracturing of the dependence of the linear dimensions of the created gap on pressure, flow, velocity, and filtration characteristics of the liquid in the zone of rock failure.

When performing hydraulic fracturing, from working 1 in rock mass 2, a working well 3 is drilled, in which a germ slot 4 is created and a packer 5 is installed. the pressure at which hydraulic fracturing occurs with the formation of a fracture 10 intersected by the well 3.

In order to control the size of hydroframes along the mine 1, the test wells 11 to the intersection with the fracture 10 are drilled at predetermined distances, and photodetectors 12 are installed in them, which are connected to gauge 1A of time intervals through cables 13. In control wells, sealants are installed.

one

Q.

2TK (P)

m

(2)

jams 15. From the additional pump 16 from the reservoir 17 to the manipulator 8 A dye (colored liquid) is supplied, where r, which moves the piston 18 and 45 through pipe 9 and the germinal gap 4 of the hydraulic fracture, m.

enters the crack 10. The pressure of the liquid for a round crack forms the average crack radius,

resulting in

The bones pumped into the well are measured with a pressure gauge 19. At the moment the dye is supplied, the pressure of the additional pump 16 is adjusted to the pressure of the working fluid, and the pressure of the main pump is released. According to the arrival time of the dye to the photodetectors and the known distance between the control wells, the dependence of the fluid velocity with the distance from the working well is found and, based on this dependence, the hydraulic fracture sizes are determined: at those points where the fluid velocity is zero, and there is a crack boundary.

In the case of hydraulic fracturing, the feed fluid is filtered through the walls of the resulting cracks. The flow rate of the fluid going to filter at a given pressure is proportional to the area of the fracture zone. If the flow rate of the feed fluid is kept constant, the area of the fracture zone, having reached certain values, does not change. All coming from Q.

crack wall that can be expressed as

Q

(P) -S, m7s,

(one)

K (P) 25

S 20 where Q

flow rate of liquid supplied from pumps, m / s; the filtration characteristic of the rock is equal to the flow rate of the liquid at pressure P through a unit of surface area of the trashna, m / s; total surface area of the formed cracks, m

40 c like

thirty

Funkts and K (P) for specific rocks are determined by known methods.

If the hydraulic fracturing is carried out under the conditions of an equal component (hydrostatic) stress state of rocks, when the shape of the resulting fracture can be considered quasi-circular, then the average fracture radius is determined by expression (1)

one

Q.

2TK (P)

m

fracturing,

, fracturing, m

 - the average radius of the crack,

resulting from

the stroke of the fluid supplied from the pumps can be presented as

,, MVc, (3)

Q is the flow rate of the fluid that is filtered in the fracture zone bounded by a circle with radius g, MVcj

Q is the flow rate of a fluid that flows outside the fracture zone limited

31

circle with paflHvcOM g,. It's obvious that

Qn-z- r KCP)

Q, 2urh, V,

where hp is the view. cracks. at a distance f from the working well, m;

VP is the radial velocity of fluid at a distance g from the working well, m / s. Outcome from (3) and (4) the view of the crack

, Q-z-irr кт,.

Radially, the velocity V ,, of the fluid at the intersection of the control wells of the fracture can be measured by known means. They allow for single wells to determine both the speed and the direction of fluid flow in a fracture and in some cases can be successfully applied. However, borehole (and the main disadvantage of such tools is a small base, limited by the diameter of the well and, therefore, low measurement accuracy.

When conducting hydraulic fracturing in most cases, it is assumed that the movement of fluid is directed from the working well to the fracture boundary. Then its speed can be determined simply and with high accuracy by feeding the dye into the slit and measuring its arrival time at the control wells drilled along one of the lines of motion of the fluid. In this method, test wells are drilled through known distances along the mine, in which the working well is located, and the dye is pumped into the fracture from the reservoir with additional suction as follows. The pressure of the dye (colored fluid) is brought to the pressure of the working fluid and fed to the manipulator 8. After that, the pressure of the working fluid is released. Under the action of the pressure difference between the working fluid and the dye, the piston 18 moves towards the main pump and the dye through the manipulator 8, the pipe 9 and the embryonic slit 4 enter the gap of the rock. It is important that during the period of filing the dye the pressure of the fluid in the crack does not change and, after

Consequently, the stationarity of the npoiu cca of its filtration into the rock is not disturbed. The viscosity of the dye and the working fluid should be approximately the same. In the test wells, a photodetector device 12 is installed, which is a tube with longitudinal slots, with one of the ends of which a LED is installed, and with the other - a photodiode.

Photodetectors through cables 13 is connected to the meter time intervals. At the inputs of the time interval gauges there are comparators to which the photodiodes are connected. Comparators are triggered when the dye enters the tubes through the longitudinal slots and changes the light fluxes in them from the LEDs to the photodiodes. Fluid velocity is defined as the ratio of the distance between control wells to the difference in the arrival time of the dye in them.

After determining the time of dosing to the dye wells, the pressure of the main pump is adjusted to the same, and the pressure of the additional pump is released. Porteni 18 moves in the direction of the additional pump 16. The working fluid enters the crack and passes the photodetectors. The comparators are reset. The meter 14 time intervals set to the zero position. After that, the system is ready for the next measurements.

Claims (4)

1. A method for monitoring the dimensions of a fractured hydraulic fracture of rocks, including the injection of fluid into a well intersecting a fracture, and measuring parameters of fluid flow, characterized in that, in order to improve the accuracy of determining the dimensions of a single fracture of a fracture, The distance to the well and the location of the points where the fluid velocity is zero determine the fracture boundaries. 2, a method according to claim I, characterized in that the flow rate of the fluid in the well is measured, and the position of the flow is determined from the expression Qili.iiMll ZITrV., M, de r - distance from working borehole to measuring point, m; h is the crack height at a distance g from the well; VP .- fluid velocity in the fracture at a distance of r JQ from the well, m / s; Q - fluid flow in the well, K (P), the filtration characteristic of the rock, is equal to the flow rate of the fluid through the unit surface of the fracture at fluid pressure, equal to the fluid pressure in the well, m / s. 3. The method according to paragraphs. 1 and 2, casting by the fact that the dependence of the velocity of the fluid in a crack on the expansion 20 Editor A. Sabo Compiled by S. Potapov Tehred L. Serdyukova Order 871/32 Circulation 455 Subscription VNIZHSCH of the USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Resszyuka nab. 4/5 Production and printing company, Uzhgorod, st. Design, 4. One hundred meters to the well is determined by the time of occurrence in the test wells crossing the fracture of the dye supplied to the well periodically. 4. The method according to paragraphs. 1 and 2, characterized in that the average crack radius is determined from the expression  T 9 2 IR (P) m five 0 where r o , RK (R.) average crack radius; fluid flow in the well, MVc; - the filtration characteristic of the rock is equal to the flow rate of the fluid through the unit surface of the fracture at a fluid pressure equal to the fluid pressure in the well, m / s. Proofreader M.Samborsk