The control method of plugging in the construction of cut-off grouting curtains

 

(57) Abstract:

The invention relates to the field of mining and can be used for the protection of the quarries from groundwater. The control method of plugging in the construction of cut-off grouting curtains includes the determination of the parameters of the backfill, a comparison of the current parameters of the backfill with the project, selection of the optimal mode in comparison parameters, the calculation of the radii distribution of cement slurry and evaluation of backfill on the comparison of the current radius with the project. It is new that determine the residual pressure on the earth's surface and take it into account to determine the residual pressure at the well bottom. Modeling of stress-strain state of rock massif determine the design pressure at the well bottom. Compare the pressure at the well bottom and its design pressure. The optimal regime consider the mode under the condition of equality or excess residual pressure at the well bottom above its design pressure. Given calculation formula for determining the radius distribution of cement slurry. table 1.

The invention relates to the field of mining and can be ispolzovanie in a comprehensive method to plug (1). It lies in the fact that the injection of cement slurry in each permeable interval osushestvlya to achieve the design pressure during injection or stop and volume of cement slurry, which are defined by the following ratios:

,

where PC- pressure fluid at the well bottom,

odynamic shear stress of cement slurry,

r is the radius of the spreading solution around a single well (for simplicity, the influence of anisotropy filtration properties excluded),

- average disclosure temporarely cracks

PPL- reservoir pressure,

V is the volume of cement slurry,

h - power permeable interval,

mtfractured voidness.

The disadvantage of this method is low efficiency and insufficient accuracy due to the use of formula (1) as it is only fair to calculate the pressure in a single fracture, and does not apply to fractured environment containing multiple fracture systems, and use the relation (2) to calculate the volume of cement slurry as it is not true at all filtering modes because it does not take into account the deformation of the massif is taken care solution for large cracks.

The closest in technical essence and the achieved result is a control method of bridging [2], where an attempt is made to assess the dynamics of formation of the grouting curtain on the nature of changes in discharge pressure. The process is considered to be optimal if the discharge pressure during injection rising steadily. In the calculation of the radius distribution is taken into account only the volume of solution pumped with increasing discharge pressure.

The disadvantage of this method is the low efficiency of plugging caused by wrong choice of the criterion for the optimal mode to plug, because it does not consider the possibility of geroestinenny already protonirovannoi zone, which is accompanied by the development of new cracks, partial closure of old and, as a consequence, the change in initial permeability that leads to a nonmonotonic behavior of the discharge pressure.

The purpose of the invention is improving the efficiency and quality of the backfill due to the use of updated dependencies (formula) to calculate the parameters and a new quantitative criterion of optimality to plug in the exercise of control over him.

This objective is achieved in that in the method of controlling camponogara current settings with the design and evaluation of backfill on the comparison of the current radius from the project, additionally determine the residual pressure (Popon the surface of the earth and the residual pressure (Poz) on the bottom hole, determine the design pressure (P'or), modeling the stress-strain state of the rock mass, compare the residual pressure at the well bottom (Poz) design pressure (P'or), select the optimal mode of bridging and determine for him the current radius distribution of cement slurry according to the formula:

< / BR>
where Vabout- the volume of cement slurry pumped in optimal mode, plug, m3;

h - power companyremoval interval, m;

is the coefficient of appointest fractured rocks, MPa-1;

Pozresidual pressure at the well bottom, MPa;

PPL- reservoir pressure, MPa.

It is known that when plugging watered fractured rocks, located at a great depth in hard-intense-deformed condition, high quality backfill is achieved when the following two conditions:

all cracks inside the zone plugging shall be filled with cement slurry;

after hardening of the mortar between him and the wall temporarely of tridecanal in protonirovannoi zone. As the plug is clinicamente solution that obeys the law filtration with maximum pressure gradient in the watered fractured massif, located in complex stress state, after a full stop solution pressure at the well bottom falls not to the reservoir pressure (PPL), and to the maximum equilibrium pressure /5/, called the residual (Poz), which is determined by the formula:

Poz=Gr+PPL,

where G is the maximum pressure gradient, KPa/m;

r is the current radius, m;

PPL- reservoir pressure, MPa.

If the residual pressure (Poz) retains a constant value until the hardening solution, then, made the first necessary condition for the achievement of high quality plug - all cracks healed, inside protonirovannoi zone no voids, leading to pressure relief. Thus, additional determination of the residual pressure at the well bottom (Pozallows you to quickly assess the effectiveness and quality of the backfill.

To perform the second exercise good adhesion of mortar with the breed hardening is necessary that during discharge of the solution happens the cracks due to their "reverse" deformations. For this purpose, the pressure of the solution must exceed the normal compressive stress acting from the side of the mountain at the crack. This means that should run the following condition:

PozP'or< / BR>
where P'or- design pressure.

A value of P'oris determined for each tamponirovanie well and interval of the simulation results of the stress-strain state of rock massif, where a waterproofing veil. This is the optimal mode of bridging. A measure of the optimality of the mode is the value of the residual pressure at the well bottom. Hence, this interval is plugged quality and it can be calculated radius.

Because the current radius distribution solution around tamponirovanie well in elastic mode filter can be defined by the formula:

< / BR>
where Vabout- the volume of solution that has spread radially around a single hole in the optimal mode plug; is the coefficient of appointest companyremoval mountain massif, which is determined, for example, the results of hydrocldone, and the value of the maximum pressure gradient (G) at a known radius (r) of opredelennosti residual pressure (Pop) by the formula:

Poz=Pop+Pg-Pt,

where is the density of the solution, g is the acceleration of gravity, l and d are length and diameter of the hole, respectively, we can calculate the value of the current radius by the following formula:

< / BR>
where Vabout- the volume of cement slurry pumped in optimal mode, plug, m3;

h - power companyremoval interval, m;

is the coefficient of appointest fractured rocks, MPa-1;

Pozresidual pressure at the well bottom, MPa;

PPL- reservoir pressure, MPa.

The method is as follows. Using mathematical modeling, taking into account the geomechanical properties of rocks, geological and hydrological conditions, the calculated stress-strain state of a rock mass in the area created grout. From the simulation results determine the value of P'or.

Determine the residual pressure on the earth's surface (Pop); taking into account pressure losses in the pipeline and in the well (Pt) and the hydrostatic pressure of a column of cement slurry (Pgdetermine residual Davie - the density of the solution, g is the acceleration of gravity, l and d are length and diameter of the hole, respectively.

Compare Pozwith P'or. If the condition PozP'orthen, considering that prior to the stop plugging passed in the optimal mode, determine the radius distribution of the solution by the formula:

.

Compare the radius r project rp. If the condition of r>rpthen backfill cease.

Example.

Plugging permeable interval power (h) depth (l), diameter injection wells (d), the coefficient of appointest breeds ( ), pressure (PPL).

Promodlive stress-strain state of the rock mass, for example, around the career of "the World" in Yakutia, has determined the estimated value (P'or).

Backfill was carried out, for example, in three stages with three process stops. After each stop was determined by the residual pressure on the earth's surface (Popand the volume of injected solution (V). Backfill was conducted clinicamente solution with density ( ), dynamic shear stress (o) .

Previously at the design stage was to define what. (line 1).

Controlled plug in the first stage. Measured residual pressure on the earth's surface (Popand the volume of injected solution (V) residual pressure at the well bottom (Poz) was calculated by the formula (9) were compared Pozwith P'or. By comparing the results found that the plug was conducted in a non-optimal mode, therefore, the optimal volume Vaboutand the current radius qualitatively protonirovannoi the field equal to zero. Given the conclusion: continue plugging. The results of the control plug at the first stage are listed in the table. (line 2).

Controlled plug in the second stage. Measured Popand V; calculated Pozby the formula (9); compared Pozwith P'or. By comparing the results found that the plug was conducted in the optimal mode, therefore, was calculated optimal volume Vaboutand the current radius qualitatively protonirovannoi the field by the formula (10). Comparing r and rCR. By comparing the results issued conclusion: the design radius is not reached, continue plugging. The results of the control plug at the second stage are listed in the table. (line 3).

Controlled plug on Tr. By comparing the results found that the plug was conducted in the optimal mode, therefore, was calculated optimal volume Vaboutand the current radius qualitatively protonirovannoi the field by the formula (10). Comparing r and rCR. By comparing the results issued conclusion: the design radius is exceeded, backfill to finish. The results of the control plug at the third stage are listed in the table. (line 4).

The control method of plugging in the construction of cut-off grouting curtains, including determination of the parameters of the backfill, a comparison of the current parameters of the backfill with the project, selection of the optimal mode of plugging in comparison parameters, the calculation of the radii distribution of cement slurry and evaluation of backfill on the comparison of the current radius from the project, characterized in that to determine the residual pressure on the earth's surface and take it into account to determine the residual pressure at the well bottom, the modeling of the stress-strain state of rock massif determine the design pressure at the well bottom, compare the pressure at the well bottom and its design pressure and optimal mode consider the mode provided

PaboutC< the design pressure of the well,

and the radius distribution of cement slurry are calculated according to the formula

< / BR>
where Vaboutthe volume of cement slurry pumped in optimal mode, plug, m3;

h power companyremoval interval, m;

is the coefficient of appointest fractured rocks, MPa-1;

PaboutCthe residual pressure at the well bottom, MPa;

Pplreservoir pressure, MPa.

 

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