CN101737037A - Synthetic focusing method capable of inducing polarization well logging - Google Patents

Abstract

The invention relates to a synthetic focusing method capable of inducing polarization well logging. According to the synthetic focusing method, nine annular electrodes are embedded in a columniform insulating rod to form an electrode system, wherein two pairs of monitor electrodes and two pairs of shielding electrodes are symmetrically arranged with a main electrode in the center; the electrodes are short-circuit mutually; a well logging is divided into a plurality of split fields to supply power separately, and corresponding split field inducing polarization potential of the split fields and a secondary potential attenuation curve after power-off are recorded; split field secondary potential is equivalent to the split field inducing polarization potential to obtain an inducing polarization potential curve during power supplying of the split field; and then polarization total field potential is synthesized by means of an electric field superposition principle and equipotential focusing synthetic conditions to obtain the attenuation curve of primary potential, inducing polarization total field potential and the secondary potential, a specific resistance and polarizability well logging curve after focusing. The synthetic focusing method has the advantages that the detection depth of the method reaches 2.4m, while the layering capability reaches 0.5m; and meanwhile, the method can reduce influences on inducing polarization well logging caused by boreholes, wall rocks and invaded zones, thereby increasing both the layering capability and measuring precision.

Description

The synthetic focusing method of induced polarization log

Technical field:

The present invention relates to the logging method of petroleum geology exploration and metal mineral reserves exploration.Particularly a kind of synthetic focusing method that can be used for the induced polarization log of dark survey and shallow survey.

Background technology:

In the at present external prior art, the Amoco of the U.S. and Shell Co. Ltd have developed experiment type non-focusing frequency domain, time domain shooting on group polarization logging instrument, Russia also attaches great importance to the research to induced polarization log method and instrument, and the non-focusing induced polarization instrument of having developed can be measured 15 parameters of three electrode spacings simultaneously.

China has also developed non-focusing induced polarization log instrument, and this instrument is applied in the oil field, has obtained certain geological effect.

But because the investigation depth of non-focusing induced polarization log instrument is more shallow, investigation depth is a 0.6-0.8 rice, and resolution ratio is also not enough, and vertical resolution is 1 meter, and is subjected to the influence of well, country rock and invaded zone bigger, thereby has influenced its certainty of measurement and range of application.

Show through Hubei Province's information retrieval center online information retrieval: the patent and the document that also find no the synthetic focusing method aspect of closing induced polarization log at present.

Summary of the invention:

The purpose of this invention is to provide a kind of synthetic focusing method that can be used for the induced polarization log of dark survey and shallow survey, the focusing induced polarization log is achieved.

The object of the present invention is achieved like this: by nine ring electrodes, be embedded on the columniform insulating rod and constitute electrode system, main electrode A0, two couples of monitor electrode M1, M1 ' and M2, M2 ', two couples of bucking electrode A1, A1 ' and A2, A2 ' are the center with the main electrode, and each is arranged symmetrically to the relative main electrode A0 electrode of electrode, and short circuit mutually between every pair of electrode, the current supply circuit electrode B places relative infinity with measurement loop electrode N.

No matter be dark the survey or shallow survey, all induced polarization log be divided into independent power supply in two another arenaes or a plurality of another arena and measurement and divide field potential; First another arena is by main electrode A0 emission constant current I0, and bucking electrode A1, A1 ' and A2, A2 ' emission current not writes down another arena induced polarization current potential on its corresponding monitor electrode M1, M1 ' and M2, the M2 ' and the secondary electric potential attenuation curve after the outage; Second another arena has only bucking electrode emission constant current I1, and main electrode A0 emission current not, writes down another arena induced polarization current potential on its corresponding monitor electrode and the secondary electric potential attenuation curve after the outage.Match another arena secondary electric potential attenuation curve obtains its secondary electric potential amplitude; With another arena secondary electric potential equivalence to another arena induced polarization current potential, induced polarization potential curve in the time of can obtaining the another arena power supply, utilize electric field principle of superposition and monitor electrode equipotential to focus on synthesis condition again, the total field potential of synthetic polarization, just a current potential after can obtaining focusing on, the total field potential of induced polarization and secondary electric potential attenuation curve, resistivity and polarizability log after also can obtaining focusing on.Thereby the focusing induced polarization log is achieved.

In power supply process,, form polarization field because rock and ore under constant External Electrical Field, ionic polarization takes place.If the passive system of being studied is linear, and do not consider the electrokinesis influence, secondary electric potential attenuation curve after charging curve when then powering and the outage is corresponding consistent, that is can be with the secondary electric potential attenuation curve (or being called discharge curve) after the outage corresponding equivalence be induced polarization potential curve (or being called charging curve) when powering.

Because what main electrode and bucking electrode sent all is constant current, under stable case, its field that produces in the stratum is quasi-static field.For the formed electric field of stabling current, the differential equation of primary field and induced polarization resultant field, interface condition and fringe conditions, they all are the linear representations about unknown function u and derivative thereof, promptly this consideration be the linear differential equation and linear fringe conditions, thereby satisfy the electric field principle of superposition.The linear superposition of the another arena polarization potential that the combined potential of polarization resultant field produces when equaling each electrode and powering separately.

Because this invention is adopted synthetic on secondary electric potential equivalence to the time current potential, thereby the focusing induced polarization log is achieved.If directly synthetic secondary electric potential then lack effective means and theoretical proof, technical scheme of the present invention then has its corresponding theory basis to be foundation.If the induced polarization potential curve when directly measuring power supply then because secondary electric potential and a current potential differ one, two order of magnitude, is difficult to guarantee the certainty of measurement of secondary electric potential.

By adjusting the size that focuses on the induced polarization log electrode system, its investigation depth can reach 2.4 meters, and vertical resolution can reach 0.5 meter.Focus on induced polarization log and can reduce the influence of well, country rock and invaded zone, improve vertical resolution and certainty of measurement induced polarization log.This will provide how prior well logging information for the remaining oil distribution and the thick zone subdivision of high water-cut stage.

Description of drawings:

Fig. 1 is an electrode system schematic diagram of the present invention;

Secondary electric potential attenuation curve figure after charging curve when Fig. 2 is power supply and the outage.

The specific embodiment

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.

Electrode system of the present invention has nine ring electrodes, is embedded on the columniform insulating rod.9 is main electrode A0,7,11 and 5,13 is two couples of monitor electrode M1, M1 ' and M2, M2 ', and 3,15 and 1,17 is two couples of bucking electrode A1, A1 ' and A2, A2 ', is the center with the main electrode, each is arranged symmetrically to the relative A0 electrode of electrode, and short circuit mutually between the every pair of electrode.2,4,6,8,10,12,14,16 is insulating rod.The current supply circuit electrode B places relative infinity with measurement loop electrode N.

UPT is the another arena polarization potential, means UPT0 (M1), UPT0 (M2), UPT1 (M1), UPT1 (M2), and URT is the current potential in another arena, the another arena secondary electric potential attenuation curve of U2T (t) after for outage, mean U2T0 (M1, t), U2T0 (M2, t), U2T1 (M1, t), U2T1 (M2, t).As shown in the figure, apply a constant external electric field at first for the sand shale stratum, make it to produce polarization field, that is electricity layer deformation of generation idol and local change in concentration, when extra electric field is disconnected go after because the diffusion of ion, ion concentration gradient will fade away, be that secondary field is decayed gradually, return to original state.

Optimum implementation of the present invention is with the equal short circuit of all symmetry electrodes, when surveying deeply with A1 and A2 short circuit as bucking electrode, B is the current supply circuit electrode; During shallow survey with A1 as bucking electrode, A2 is the current supply circuit electrode.In the another kind of power supply mode, also main electrode A0, bucking electrode A1 and bucking electrode A2 can be powered separately as three another arenaes, measure the branch field potential on monitor electrode and the current electrode, utilize method synthetic focusing same as described above.Optimum implementation of the present invention is identical with three another arena synthetic effects, but has reduced the measurement number of times, has improved measurement efficient.

First another arena is by main electrode A0 emission constant current I0, and bucking electrode emission current not, write down on its corresponding monitor electrode M1 and the M2 another arena induced polarization current potential UPT0 (M1), UPT0 (M2) and the outage after secondary electric potential attenuation curve U2T0 (M1, t), U2T0 (M2, t); Second another arena has only bucking electrode emission constant current I1, and main electrode A0 emission current not, write down on its corresponding monitor electrode M1 and the M2 another arena induced polarization current potential UPT1 (M1), UPT1 (M2) and the outage after secondary electric potential attenuation curve U2T1 (M1, t), U2T1 (M2, t).Match secondary electric potential attenuation curve U2T0 (M1, t), U2T0 (M2, t), U2T1 (M1, t), (M2 t), obtains its secondary electric potential amplitude U2T0 (M1), U2T0 (M2), U2T1 (M1), U2T1 (M2) to U2T1.

Induced polarization potential curve (or being called charging curve) when the corresponding equivalence of the secondary electric potential attenuation curve (or being called discharge curve) after the outage of another arena is powered for the another arena:

UPT0(M1，t)＝UPT0(M1)-U2T0(M1，t) (1)

UPT0(M2，t)＝UPT0(M2)-U2T0(M2，t) (2)

UPT1(M1，t)＝UPT1(M1)-U2T1(M1，t) (3)

UPT1(M2，t)＝UPT1(M2)-U2T1(M2，t) (4)

Another arena in the time of can being obtained not having polarization by the secondary electric potential amplitude after another arena polarization potential and the outage is (pure resistance effect) current potential once:

URT0(M1)＝UPT0(M1)-U2T0(M1) (5)

URT0(M2)＝UPT0(M2)-U2T0(M2) (6)

URT1(M1)＝UPT1(M1)-U2T1(M1) (7)

URT1(M2)＝UPT1(M2)-U2T1(M2) (8)

According to the electric field principle of superposition, one time the current potential composite formula is:

URT(M1)＝URT0(M1)+C1URT1(M1) (9)

URT(M2)＝URT0(M2)+C1URT1(M2) (10)

The equipotential focused condition is:

URT(M1)＝URT(M2) (11)

Can get primary field composite coefficient and potential focus is:

${\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_1=\frac{U_{\mathrm{RT}0}\left(M_1\right)-U_{\mathrm{RT}0}\left(M_2\right)}{U_{\mathrm{RT}1}\left(M_2\right)-U_{\mathrm{RT}1}\left(M_1\right)}---\left(12\right)$

URT＝URT(M1)＝URT(M2) (13)

By another arena polarization potential composite formula

UPT(M1)＝UPT0(M1)+C2UPT1(M1) (14)

UPT(M2)＝UPT0(M2)+C2UPT1(M2) (15)

And equipotential focused condition:

UPT(M1)＝UPT(M2) (16)

Resultant field composite coefficient and potential focus can polarize:

${\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_2=\frac{U_{\mathrm{PT}0}\left(M_1\right)-U_{\mathrm{PT}0}\left(M_2\right)}{U_{\mathrm{PT}1}\left(M_2\right)-U_{\mathrm{PT}1}\left(M_1\right)}---\left(17\right)$

UPT＝UPT(M1)＝UPT(M2) (18)

By the instantaneous polarization potential composite formula in another arena:

UPT(M1，t)＝UPT0(M1，t)+Ci*UPT1(M1，t) (19)

UPT(M2，t)＝UPT0(M2，t)+Ci*UPT1(M2，t) (20)

And equipotential focused condition:

UPT(M1，t)＝UPT(M2，t) (21)

Instantaneous composite coefficient of resultant field and potential focus can polarize:

$\mathrm{Ci}=\frac{U_{\mathrm{PT}0}({\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_1,t)-U_{\mathrm{PT}0}({\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_2,t)}{U_{\mathrm{PT}1}({\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_2,t)-U_{\mathrm{PT}1}({\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="H2008102272768E0000011.png"\; state="\{\{state\}\}">M</figure-callout>}}_1,t)}---\left(22\right)$

UPT(t)＝UPT(M1，t)＝UPT(M2，t) (23)

Thereby the resistivity that obtains behind the synthetic focusing is:

Rt＝K*URT/IA0 (24)

K is the instrument coefficient.

Secondary electric potential amplitude and attenuation curve thereof behind the synthetic focusing are:

U2T＝UPT-URT (25)

U2T(t)＝UPT-UPT(t) (26)

Polarizability amplitude and attenuation curve thereof behind the synthetic focusing are:

η2T＝U2T*100/UPT (27)

η2T(t)＝U2T(t)*100/UPT。(28)

Claims (1)

1. the synthetic focusing method of an induced polarization log is characterized in that:

By nine ring electrodes, be embedded on the columniform insulating rod and constitute electrode system, main electrode A0, two couples of monitor electrode M1, M1 ' and M2, M2 ', two couples of bucking electrode A1, A1 ' and A2, A2 ' are the center with the main electrode, and each is arranged symmetrically to the relative A0 electrode of electrode, and short circuit mutually between every pair of electrode, the current supply circuit electrode B places relative infinity with measurement loop electrode N;

Induced polarization log is divided into the independent power supply in two another arenaes or a plurality of another arena and measures the branch field potential; First another arena is by main electrode A0 emission constant current I0, and bucking electrode A1, A1 ' and A2, A2 ' emission current not, writes down another arena induced polarization current potential on its corresponding monitor electrode M1, M1 ' and M2, the M ' and the secondary electric potential attenuation curve after the outage; Second another arena has only bucking electrode emission constant current I1, and main electrode A0 emission current not, write down on its corresponding monitor electrode another arena induced polarization current potential and the outage after the secondary electric potential attenuation curve, match another arena secondary electric potential attenuation curve obtains its secondary electric potential amplitude; Another arena secondary electric potential equivalence to another arena induced polarization current potential, can be obtained the another arena induced polarization potential curve in when power supply; Utilize electric field principle of superposition and monitor electrode equipotential to focus on synthesis condition again, the total field potential of synthetic polarization, just a current potential after can obtaining focusing on, the total field potential of induced polarization and secondary electric potential attenuation curve, resistivity and polarizability log after also can obtaining focusing on.

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