CN1945357A - Method for setting exploration signal receiver amplifying time of artificial field source electric method - Google Patents

Abstract

The invention discloses a method for setting the magnification of receivers for electromagnetic survey signals of artificial source including the following steps: (1) measuring the apparent resistivity of at least one point, (2) making a prediction about the signal by using the measured apparent resistivity, (3) and setting the magnification of the receiver based on the result of step 2.

Description

Method for setting exploration signal receiver amplifying time of artificial field source electric method

Technical field

The present invention relates to a kind of geophysical exploration method, especially relate to a kind of method for setting exploration signal receiver amplifying time of artificial field source electric method.

Background technology

In artificial field source resistivity prospecting, send electric field, magnetic field or electromagnetic wave signal to the earth with electric exploration signal transmitter (hereinafter to be referred as " transmitter ").Receive the response in the earth of above-mentioned electric field, magnetic field or electromagnetic wave signal with receiver of electrical prospecting signal (hereinafter to be referred as " receiver ") by electric field and magnetic field sensor.In the artificial field source resistivity prospecting method, for resistivity method and induced polarization method, in the probing process, because equipment therefor and supply current is different, great changes have taken place to cause received signal, and this requires before each the measurement enlargement factor of receiver to be set.At present, the method to set up of receiver enlargement factor is a size of measuring received signal in advance, by artificial or automated manner enlargement factor is set again.This method has following shortcoming: 1, since the signal frequency that resistivity method and induced polarization method receive generally below 1Hz, the measuring-signal size can cause Measuring Time to prolong in advance, reduces work efficiency; 2, generally there is filtering circuit receiver inside, and the enlargement factor change can cause filtering circuit to produce transient state, enters steady state (SS) from transient state, needs a plurality of signal periods, and this has prolonged Measuring Time again; If 3 enlargement factors that are provided with during measuring-signal in advance are too little, then measuring error is very big, be difficult to correctly be provided with enlargement factor,, can cause the saturation of receiver again if the enlargement factor that is provided with is too big, receiver returns to normal condition from state of saturation and also needs the long period, therefore, when the each signal of measuring of receiver has than great fluctuation process, correct enlargement factor is set, need repeatedly be provided with or a plurality of signal periods of needs enlargement factor, have a strong impact on measuring speed.

Summary of the invention

The objective of the invention is to overcome the above-mentioned defective that existing receiver enlargement factor method to set up exists, a kind of method for setting exploration signal receiver amplifying time of artificial field source electric method that increases substantially efficiency of measurement is provided.

The objective of the invention is to be achieved through the following technical solutions:

Because being volumetric, resistivity prospecting measures, although the electric condition in ground (resistivity of geologic body) alters a great deal, but the variation of parameter (apparent resistivity) between adjacent measuring point or pole span of measuring is little, thereby can predict the apparent resistivity of measuring point to be measured by the apparent resistivity of the measuring point measured.

The acute variation of receiver received signal mainly is because the variation of device and supply current causes.And device parameter and supply current all are known quantity before measurement.Therefore, as long as known device parameter and supply current, and the apparent resistivity of the tested point of prediction, just can calculate the signal magnitude of measuring point to be measured.Known the size of measuring point signal to be measured, the signal amplification factor of receiver just can correctly be set.Because the minimum shelves of the signal amplification factor of a receiver difference is 2, bigger shelves difference has 3,4,5,6,8 and 10 etc., and the predicated error that needs only apparent resistivity is controlled in 50%, just can guarantee the correct setting of enlargement factor.

The computing formula of apparent resistivity is as follows:

${\mathrm{\ρ}}_a=K\frac{\mathrm{\ΔU}}{I}---\left(I\right)$

In the formula, ρ _aThe expression apparent resistivity, K indication device coefficient, I represents supply current, Δ U represents potential difference (PD), is the signal that receiver is measured;

The prediction and calculation formula of receiver received signal is as follows:

${\mathrm{\ΔU}}_p={\mathrm{\ρ}}_{\mathrm{ap}}\frac{I}{K}---\left(\mathrm{II}\right)$

In the formula, Δ U _pThe signal magnitude of expression prediction, ρ _ApThe apparent resistivity of expression prediction, the implication of other variable is identical with formula (1).

The present invention's the concrete method to set up of receiver received signal enlargement factor is as follows:

(1) measures at least one measuring point apparent resistivity to be measured, utilize the computing formula (I) of apparent resistivity to calculate apparent resistivity;

(2) utilize formula (II) prediction measured signal size, when surveying apparent resistivity ρ _aWhen measuring point has only 1, with measuring point apparent resistivity value ρ _aApparent resistivity ρ as prediction _Ap, utilize formula (II) to calculate prediction measured signal size then; When surveying the apparent resistivity measuring point and have 2, utilize the linear extrapolation method to predict the apparent resistivity of measuring point to be measured earlier, utilize formula (II) to calculate prediction measured signal size again; When surveying the apparent resistivity measuring point is 3 or during more than 3, predicts the apparent resistivity of measuring point to be measured earlier with extrapolation, utilizes formula (II) to calculate prediction measured signal size again; The apparent resistivity prediction method for optimizing of measuring point to be measured is a polynomial extrapolation; The used measuring point of polynomial extrapolation number is preferably the 3-4 point.

(3) obtain the prediction measured signal size of measuring point to be measured after, determine in view of the above again the signal amplification factor of receiver the receiver signal enlargement factor to be set then.

Beneficial effect: before resistivity or induced polarization method measurement, by effective prediction measured signal size, guarantee to set in advance optimum enlargement factor before receiver is measured, need not all the receiver enlargement factor to be set, can increase substantially the work efficiency of resistivity method and induced polarization method by measuring each measured signal size.

Description of drawings

Fig. 1 is a FB(flow block) of the present invention.

Embodiment

The invention will be further described below in conjunction with accompanying drawing.

With reference to Fig. 1,＜1〉surveyed apparent resistivity measuring point number=0? condition is true, successively execution in step＜9〉and step＜6, promptly earlier determine the receiver enlargement factor with the measured signal method, the receiver enlargement factor is set then, otherwise execution in step 2;＜2〉surveyed apparent resistivity measuring point number=1? condition is true, execution in step 10, step 5 and step 6 successively, promptly earlier with surveying the first measuring point apparent resistivity as measuring point apparent resistivity predicted value to be measured, utilize formula (II) to calculate prediction measured signal size again, determine the enlargement factor of receiver, the receiver enlargement factor is set then, otherwise execution in step 3;＜3〉measuring point number=2? condition is true, execution in step 11, step 5 and step 6 are promptly earlier predicted measuring point apparent resistivity to be measured with the linear extrapolation method successively, utilize formula (II) to calculate prediction measured signal size again, determine the enlargement factor of receiver, the receiver enlargement factor is set then; Otherwise execution in step 4;＜4〉predict measuring point apparent resistivity value to be measured with polynomial extrapolation;＜5〉utilize formula (II) prediction measured signal size, determine the enlargement factor of receiver;＜6〉the receiver enlargement factor is set;＜7〉A/D converter of startup receiver reads the A/D transformation result;＜8〉calculate actual measurement potential difference (PD) size.

Claims (1)

1, a kind of method for setting exploration signal receiver amplifying time of artificial field source electric method is characterized in that, may further comprise the steps:

(1) measure at least one measuring point apparent resistivity to be measured, utilize the computing formula of following apparent resistivity to calculate apparent resistivity:

${\mathrm{\ρ}}_a=K\frac{\mathrm{\ΔU}}{I}---\left(I\right)$

In the formula, ρ _aThe expression apparent resistivity, K indication device coefficient, I represents supply current, Δ U represents potential difference (PD), is the signal that receiver is measured;

(2) utilize following formula prediction measured signal size:

$\mathrm{\Δ}{U}_p={\mathrm{\ρ}}_{\mathrm{ap}}\frac{I}{K}---\left(\mathrm{II}\right)$

In the formula, Δ U _pThe signal magnitude of expression prediction, ρ _ApThe apparent resistivity of expression prediction, the implication of other variable is identical with formula (I);

When surveying apparent resistivity ρ _aWhen measuring point has only 1, with measuring point apparent resistivity value ρ _aApparent resistivity ρ as prediction _Ap, utilize formula (II) to calculate prediction measured signal size then; When surveying the apparent resistivity measuring point and have 2, utilize the linear extrapolation method to predict the apparent resistivity of measuring point to be measured earlier, utilize formula (II) to calculate prediction measured signal size again; When surveying the apparent resistivity measuring point is 3 or during more than 3, predicts the apparent resistivity of measuring point to be measured earlier with extrapolation, utilizes formula (II) to calculate prediction measured signal size again;

(3) obtain the prediction measured signal size of measuring point to be measured after, determine in view of the above again the signal amplification factor of receiver the receiver signal enlargement factor to be set then.

Images