SU1684490A1 - Method for determination of pressure of subsoil waters - Google Patents

Abstract

The invention relates to geophysical studies and is intended for geohydrodynamic systems when monitoring groundwater regimes in infiltration wells. The goal is to improve the measurement accuracy by reducing the hydrostatic component of the measured value. Pressure determination method

Description

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Neither the groundwater is carried out by opening the aquifer with a borehole 1, equipped with a column pipe 2 with filter 3, above which a pressure sensor 4 is installed, above which a waterproof ceiling 5 is installed, a hydrogeological survey is carried out and the minimum and maximum piezometric values are determined groundwater levels above filter 3 wells 1. Pressure sensor 4 and waterproof

The invention relates to geophysical studies and can be used in geohydrodynamic systems for monitoring the regime of groundwater in infiltration wells.

The purpose of the invention is to improve the measurement accuracy by reducing the hydrostatic component of the measured value.

The drawing shows a diagram of the implementation of the method for determining groundwater.

In the drawing, a borehole 1 is shown, equipped with a column pipe 2 with filter 3 above which pressure is measured by a pressure sensor 4 installed above which a waterproof floor 5 is installed. Hydrogeological research is carried out and the minimum and maximum piezometric groundwater levels are determined 3 wells 1. A pressure sensor 4 and a waterproof overlap 5 are set below the minimum piezometric level of the groundwater, and the pressure of the groundwater is determined taking into account minimum and maximum piezometric level of groundwater.

The method is implemented as follows.

The well 1 is drilled to a predetermined elevation and is equipped with a column pipe 2 with filter 3 installed at the bottom of the well 1. The filter outlets 3 of the annulus of the well 1 are plugged with a low-permeable material, after which the well is maintained so that the groundwater level is restored. According to the results of preliminary hydrogeological studies, the minimum hmin and maximum hmax levels of groundwater are determined.

The measurement limit P of the pressure sensor scale 4, i.e. The groundwater pressure, displacement 5 is set below the minimum piezometric level of the groundwater, the groundwater pressure is determined taking into account the minimum and maximum piezometric level of the groundwater, and the measurement limit of pressure sensor 4 is equal to the difference between the maximum and minimum piezometric groundwater levels. 1 il.

rage in units of height of the water column, choose from

P (hmax - hmln) / 3 9,

where p is the density of water;

g is the acceleration of the force of gravity.

In order to improve measurement accuracy and the possibility of using a highly sensitive pressure sensor, sensor 4 is installed above filter 3 at

-7 - I, P

2L- hmax- -,

where 2D is the height of installation of the pressure sensor from the upper mark of the well filter.

Above the pressure sensor 4 in the pipe string, a waterproof overlap 5 at the mark is created, taking into account the ratios

2d znep hmin,

where Znep is the excess of the waterproof overlap over the well filter.

Thus, the pressure of groundwater, expressed in units of the height of the water column above the upper mark of filter 3, is determined from the expression

H 2d +

P-Q

where H is the groundwater pressure, expressed in units of the height of the water column;

P is the hydrostatic pressure measured by the pressure sensor.

Example. As is known, the error in measuring the level of groundwater, due to the inertia of an open piezometric well, is estimated by the formula

AHc-- -v КЈ

where L Hs is the error in measuring the pressure of groundwater due to the inertia of the well;

ftt is the free cross-sectional area of the well;

V is the rate of change of pressure (pressure) of groundwater;

K - rock filtration coefficient:

E is the length of the filter.

At m, V m / day. TO

ten

P

m / day and f 1 m, the error in measuring the pressure of groundwater due to the inertia of the well is

kg2 10

ten

, -2

one

  m

that is significantly more than the permissible metrological error of measuring the water level in the well.

The actual inertia of the measuring system is even greater, since the water exchange between the rock and the well takes place through a filter located in the lower part of the well. Therefore, as the level changes, practically all the water mass in the well is set in motion, and this process has its own system, but does not find its reflection in the known calculation dependencies.

In this example, the pressure sensor is the well itself (equipped with a filter tubing located in a predetermined depth interval), the large inertia of which is due to a significant specific water exchange between the internal volume of the well and the rock equal to 10 liters groundwater. Installing a hydrostatic pressure sensor or a floating piezograph in a well equipped with an open casing does not change its sensitivity and inertia. If the pipe column is above the pressure sensor, but below the water level, create a waterproof overlap, then the sensitivity of the well-pressure sensor system is determined by the sensitivity of the pressure sensor only.

Let us assume that the sensitive element of the pressure sensor is a bellows with a spectacular area of Raff. 4.0 cm stroke

 15

-j Q

 g 20 25 to 35 40

which under the action of a pressure drop of 0.1 kg / cm is 0.3 mm.

Then the change in pressure of groundwater to 1 m of water. Art. causes a change in the volume of the bellows (and Be the volume of water in the well under the waterproof overlap) by about 0.12 ml. those. almost 5 times less than in an open well.

The device allows to measure the hydrostatic pressure from 0 to 100 kPa and at the same time its sensitivity aged 3-4 cm water column. at 1 Hz, and the measurement accuracy is not inferior to the accuracy of the readings of the level of other known constructions.

The use of a less rigid bellows as a sensitive element makes it possible to increase the sensitivity of the device and, therefore, the accuracy of groundwater pressure measurement.

Thus, this technical solution allows to significantly reduce the inertia of the measuring system, use highly sensitive pressure sensors and thereby increase the measurement accuracy.

The invention of the method for determining the pressure of underground aodes, containing the opening of an aquifer by a borehole, equipped with a filter pipe, above which pressure is measured by a pressure sensor, above which waterproof overlap is established and hydrogeological studies are carried out, characterized by those. that, in order to increase the measurement accuracy by reducing the hydrostatic component of the measured value, the minimum and maximum piezometric groundwater levels above the well filter are determined, the pressure sensor and waterproof overlap are set below the minimum piezometric groundwater level, and the groundwater pressure is determined from taking into account the minimum and maximum piezometric levels of groundwater.

Claims (1)

Claim The method of determining the pressure of underground aodes, containing the opening of the aquifer by a borehole, equipped with a column pipe with a filter, above which the pressure is measured with a pressure sensor installed, above which a waterproof overlap is established and hydrogeological studies are carried out, characterized in that. that, in order to improve measurement accuracy by reducing the hydrostatic component of the measured value, determine the minimum and maximum piezometric groundwater levels above the well filter, the pressure sensor and waterproof overlap is set below the minimum piezometric groundwater level, and the groundwater pressure is determined taking into account the minimum and maximum piezometric groundwater levels.