CN2911178Y - High resolution static nature potential logging unit - Google Patents

Abstract

A high-resolution static natural potential logging tool includes a static natural potential SSP electrode system and a measuring circuit. The electrode system is composed of 9 symmetrically arranged electrode rings embedded on an insulating rod to form the main body of the electrode system. The order from top to bottom is: A2, A1, M2, M1, M0, M1', M2', A1 ', A2'; Among them, M1, M1'; M2, M2'; A1, A1'; A2, A2' are electrodes with the same name and short-circuited with wires; M0 is the static natural potential measurement electrode; electrode N is placed at a distance; The electrode with the same name, electrode M0 and electrode N are connected to the measurement circuit through wires. The measurement circuit provides current between the A1 electrode and the A2 electrode according to the size of ΔVm, so that ΔVm approaches zero; and calculates the value of the static natural potential of the formation when ΔVm approaches zero. The utility model has the performance of high resolution and can provide reliable data for describing the characteristics of thin reservoirs.

Description

High resolution ratio static natural potential well logging instrument

Invention field

The utility model relates to a kind of tester, is meant a kind of petroleum geology exploration well logging downhole instrument, i.e. high resolution ratio static natural potential well logging instrument especially.

Background technology

In general, employed drilling mud all is a water-base mud in Process of Oil Well Drilling, so for the water-base mud oil drilling, the reason that natural potential SP produces in the well mainly contains two: the mud filtrate resistivity Rmf's that produces because of formation water resistivity Rw and drilling mud is different, cause the suction-operated of the diffusion of ion and rock particles, produce the diffusion adsorption potential ion; Because of strata pressure and mud column pressure not simultaneously, filtration can take place in the part that contacts with mud at sandstone formation, produces electrofiltration potential.

At present, the measuring principle of natural potential SP logging instrument is as shown in Figure 1 in the petroleum geology exploration: among Fig. 1, and the 1--mudstone stratum; The mud-filled open hole well of 2--; The 3--triumphant dress cable of logging well; The 4--sandstone formation; The 5--ground instrument of logging well; The 6--measurement electrode; 7--ground reference electrode.

Place a measurement electrode 6 and be connected on the ground logger (5) by the triumphant dress cable 3 of logging well in the open hole well 2 of finishing drilling, ground is placed a reference electrode (7) and is connected with ground logger (5) by lead.When measurement electrode (6) when pit shaft moves, the well logging ground instrument can write down the natural potential SP curve (shown in (3) among Fig. 2) that next bar changes with mine shaft depth.

Facts have proved that the natural potential of oil well mainly is the diffusion adsorption potential, only under the very big situation of the pressure differential of mud column and ground interlayer, just consider the influence of electrofiltration potential.

In open hole well, the mechanism that natural potential SP produces as shown in Figure 2.In Fig. 2: the 1--mudstone stratum; The mud-filled open hole well of 2--; 3--natural potential SP log; The 4--sandstone formation; The fine and close lithologic character stratum of 5--impermeability.

Referring to Fig. 2, when the stratum is drilled wear after, drilling mud is full of (2) in the pit shaft, F directly contacts with formation water in the hole.Because under general situation, the resistivity Rmf of F is greater than stratum resistivity of water Rw (the salinity Cmf of drilling mud filtrate is less than the salinity Cw of formation water), and supposition F and the contained salt of formation water all be sodium chloride nacl, so:

A. at sandstone reservoir (4), chlorion Cl ^-With sodium ion Na ⁺Reservoir one side direction salinity low well mud one side higher from salinity spreads.Because chlorion C1 ^-Migration rate than sodium ion Na ⁺Hurry up, so when diffusion reaches balance, the electronegative chlorion Cl that in the pit shaft of this interval, is assembled ^-Than positively charged sodium ion Na ⁺Many, thus the negative electricity potential difference that forms between well and reservoir is Ej, and Ej is known as diffusion potential.The size of Ej is relevant with the resistivity Rmf of stratum resistivity of water Rw and F, that is:

$\mathrm{Ej}=\mathrm{Kj}\×\lg \frac{\mathrm{Rmf}}{\mathrm{Rw}}---\left(1\right)$

Kj=11.6 (in the time of 25 ℃)

B. in mudstone stratum (1) and since in the mud stone contained clay mineral to electronegative chlorion Cl ^-Very strong adsorption capacity is arranged, so chlorion Cl ^-Can't move, have only the sodium ion Na of positively charged ⁺Can move in the pit shaft, thereby form positive electricity potential difference Em between well and mudstone stratum, Em is known as adsorption potential.The size of Em is relevant with the resistivity Rmf of formation water resistivity Rw and F, that is:

$\mathrm{Em}=\mathrm{Km}\×\lg \frac{\mathrm{Rmf}}{\mathrm{Rw}}---\left(2\right)$

Km=59.1 (in the time of 25 ℃)

C. at the fine and close lithologic character stratum (5) of impermeability,, do not have diffusion phenomena and take place, so in pit shaft, can not produce potential difference because compacted zone does not have hole not contain formation water yet.

We with negative potential Ej and positive potential Em and be called static spontaneous potential (SSP) SSP, that is:

$\mathrm{SSP}=\mathrm{Ej}+\mathrm{Em}=\mathrm{Kj}\×\lg \frac{\mathrm{Rmf}}{\mathrm{Rw}}+\mathrm{Km}\×\lg \frac{\mathrm{Rmf}}{\mathrm{Rw}}$

$\mathrm{SSP}=K\×\lg \frac{\mathrm{Rmf}}{\mathrm{Rw}}---\left(3\right)$

Or $\mathrm{SSP}=K\×\lg \frac{\mathrm{Cw}}{\mathrm{Cmf}}$

Wherein: the SSP---static spontaneous potential (SSP)

K---static spontaneous potential (SSP) coefficient, in the time of 25 ℃, K=70.7

The Rmf---mud filtrate resistivity

The Rw---formation water resistivity

Cmf---F salinity

The Cw---formation water salinity

Because the size of static spontaneous potential (SSP) SSP is relevant with mud filtrate resistivity Rmf with formation water resistivity Rw, and mud filtrate resistivity Rmf is known, so can ask for formation water resistivity Rw or formation water salinity Cw with static spontaneous potential (SSP) SSP.And formation water resistivity Rw or formation water salinity Cw estimate the indispensable crucial parameter of reservoir oil saturation.

The defective of existing natural potential SP measuring technique:

Have natural potential SP measuring principle now shown in Fig. 3-1, Fig. 3-2, the 1--mudstone stratum; Mud in the 2--pit shaft; 3--F flushed zone; 4--sandstone undisturbed formation.

The big or small available following The Representation Equation of its measured value SP:

$\mathrm{SP}=\mathrm{Rm}\×\mathrm{Isp}=\mathrm{SSP}\×\frac{\mathrm{Rm}}{\mathrm{Rm}+\mathrm{Rsh}+\mathrm{Rxo}+\mathrm{Rt}}---\left(4\right)$

Wherein: mud equivalent resistance in the Rm----pit shaft

Rsh---mud stone equivalent resistance

Rxo---reservoir flushed zone equivalent resistance

Rt---reservoir undisturbed formation equivalent resistance

The SSP---static spontaneous potential (SSP)

The SP---natural potential

The Isp---natural electric current

From (4) formula as can be seen, mud (2) equivalent resistance Rm one timing in static spontaneous potential (SSP) SSP, mudstone stratum (1) equivalent resistance Rsh and pit shaft, the amplitude of natural potential SP mainly is subjected to flushed zone (3) the equivalent resistance Rxo of reservoir and the influence of undisturbed formation (4) equivalent resistance Rt size.And the size of Rxo and Rt is relevant with the resistivity and the bed thickness of this reservoir.When thickness one timing of reservoir, Rxo and Rt increase along with the increase of reservoir resistivity, and the amplitude of natural potential SP then increases along with Rxo and Rt and reduces; When one timing of reservoir resistivity, Rxo and Rt can increase along with reducing of reservoir thickness, thereby cause the amplitude of natural potential SP to reduce.

So, existing natural potential SP well logging is at the measured value that preserves interval and be not equal to static spontaneous potential (SSP) SSP, it is subjected to the influence of mineshaft diameter, mud resistivity, reservoir resistivity and thickness very big, particularly when the thickness attenuation of reservoir (less than 1 meter), existing natural potential SP log amplitude can become very little even without any reaction (referring to Fig. 7).So existing natural potential SP log can not be directly used in quantitative calculating formation water resistivity Rw, up to the present, also can measure formation water resistivity Rw directly and accurately without any a kind of other logger.

Summary of the invention

The purpose of this utility model is to provide a kind of high resolution ratio static natural potential well logging instrument, it can solve the difficult problem that can directly measure formation water resistivity Rw for a long time without any a kind of logger, particularly, for the pure reservoir of thickness greater than 0.3 meter, the utility model institute survey data can be directly used in calculates formation water resistivity Rw.

From equation (4) as can be seen, if Rm＞＞Rsh+Rxo+Rt

Then have: $\frac{\mathrm{Rm}}{\mathrm{Rm}+\mathrm{Rsh}+\mathrm{Rxo}+\mathrm{Rt}}\≈1---\left(5\right)$

SP≈SSP

(5) formula is set up, just must be increased mud equivalent resistance Rm.In order to increase mud equivalent resistance Rm, resistivity with regard to inevitable requirement mud is very high, and water-base mud generally is to add water concocting by the special-purpose chemicals of sodium, calcium, magnesium base bentonite and various mud to form, so the resistivity of water-base mud is all smaller usually, can't satisfy the requirement that (5) formula is set up.Therefore want to rely on the way that increases feasible (5) formula establishment of mud resistivity on actual engineering, to be difficult to accomplish.

Designed a kind of brand-new electrode system in the utility model, it is to utilize the principle of electric field stack to realize the measurement of SSP, and the resistivity of mud is not had special requirement.

The technical solution of the utility model is:

A kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system, measuring circuit, it is characterized in that: described electrode system is to constitute the electrode system main body by 9 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A2, A1, M2, M1, M0, M1 ', M2 ', A1 ', A2 '; Wherein, M1, M1 '; M2, M2 '; A1, A1 '; A2, A2 ' are homonymy electrode and use the lead short circuit; M0 is the static spontaneous potential (SSP) measurement electrode; M2, M2 ', M1, M1 ' are a pair of monitor electrode; A2, A2 ', A1, A1 ' are a pair of bucking electrode; Electrode N places at a distance; Each homonymy electrode, electrode M0 and electrode N are connected with measuring circuit by lead.

Another technical scheme of the present utility model is:

A kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system, measuring circuit, it is characterized in that: described electrode system is to constitute the electrode system main body by 7 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A1, M2, M1, M0, M1 ', M2 ', A1 '; Wherein, M1, M1 '; M2, M2 '; A1, A1 ' are homonymy electrode and use the lead short circuit; M0 is the static spontaneous potential (SSP) measurement electrode; M2, M2 ', M1, M1 ' are a pair of monitor electrode; A1, A1 ' are a pair of bucking electrode; A2 is a loop electrode; Electrode A 2 and electrode N place at a distance; Each homonymy electrode, electrode M0, electrode A 2 and electrode N are connected with measuring circuit by lead.

Wherein, described measuring circuit circuit is made up of operation amplifier circuit, operation amplifier circuit, signal operation amplifier circuit, variable connector and A/D analog to digital conversion circuit, one-chip computer and D/A D/A converting circuit, it is characterized in that: one-chip computer is that the size according to Δ Vm provides electric current between bucking electrode and loop electrode, makes Δ Vm level off to zero; And level off to the numerical value that calculates the static spontaneous potential (SSP) on stratum zero time at Δ Vm.

Basic functional principle of the present utility model is:

After logging instrument is transferred to the pit shaft that is full of water-base mud by the well logging armored cable, along the natural electric current Isp that flows in the pit shaft when flowing through regional between electrode M1, M2, just can produce potential difference Δ Vm between electrode M1, the M2, measuring circuit was added to electrode A 1, A2 is last and produces opposite, an equal-sized electric current with natural electric current Isp polarity in pit shaft according to suitable current signal Ip of size output of Δ Vm this moment, make the potential difference Δ Vm between electrode M1, the M2 level off to zero, i.e. electrode M1, M2 equipotential.When the current potential of electrode M1, M2 equates, as long as the spacing of electrode M1, M2 is selected suitablely, between M1, M2, just do not have again electric current to flow through in the zone of well section, the equivalent resistance Rm that is equivalent in this zone is infinity, that is:

Rm＞＞Rsh+Rxo+Rt

$\frac{\mathrm{Rm}}{\mathrm{Rm}+\mathrm{Rsh}+\mathrm{Rxo}+\mathrm{Rt}}\≈1$

Potential difference between electrode M0 and the electrode N is at this moment:

$\mathrm{SP}=\mathrm{Rm}\×\mathrm{Isp}=\mathrm{SSP}\×\frac{\mathrm{Rm}}{\mathrm{Rm}+\mathrm{Rsh}+\mathrm{Rxo}+\mathrm{Rt}}\≈\mathrm{SSP}$

Can measure static spontaneous potential (SSP) SSP promptly by this method: when the potential difference Δ Vm between electrode M1, the M2 levels off to zero the time, the potential difference between electrode M0 and the electrode N is static spontaneous potential (SSP) SSP.

Can calculate formation water resistivity Rw or formation water salinity Cw according to formula (6) (7).

$\mathrm{Rw}={10}^{-\frac{\mathrm{SSP}}{K}}\×\mathrm{Rmf}---\left(6\right)$

Or $\mathrm{Cw}={10}^{\frac{\mathrm{SSP}}{K}}\×\mathrm{Cmf}---\left(7\right)$

In the formula: K----static spontaneous potential (SSP) coefficient, in the time of 25 ℃, K=70.7

Advantage of the present utility model is: the utility model has solved the difficult problem that can directly measure formation water resistivity Rw or formation water salinity Cw for a long time without any a kind of logger.Owing to the utlity model has high-resolution performance, can be the oily property of describing thin reservoir valuable well-log information is provided.

Description of drawings

Fig. 1 is existing natural potential SP measuring method schematic diagram;

Fig. 2 is the principle schematic that natural potential produces;

Fig. 3-1, Fig. 3 the-the 2nd, the schematic diagram of existing natural potential SP measuring principle;

Fig. 4 is the theory diagram of the utility model high resolution ratio static natural potential well SSP logging instrument embodiment 1;

Fig. 5 is the theory diagram of the utility model high resolution ratio static natural potential well SSP logging instrument embodiment 2;

Fig. 6 is the formation water salinity comparison diagram that the formation water salinity Cw that calculates of the utility model institute survey data and laboratory obtain by core analysis;

Fig. 7 is the log data of the utility model in actual open hole well and the comparison diagram of the curve data of traditional natural potential SP well logging and other logging method.

The specific embodiment

The utility model is described in further detail below in conjunction with drawings and Examples.

Embodiment 1:

The theory diagram of the utility model high resolution ratio static natural potential well SSP logging instrument embodiment 1, as shown in Figure 4.In Fig. 4: electrode system part 10 comprises: electrode M0 (11), electrode M1 (12), electrode M1 ' (12 '), electrode M2 (13), electrode M2 ' (13 '), electrode A 1 (14), electrode A 1 ' (14 '), electrode A 2 (15), electrode A 2 ' (15 '), electrode N (16).

The utility model is made up of static spontaneous potential (SSP) SSP electrode system 10, measuring circuit 20.Described electrode system 10 is to constitute the electrode system main body by 9 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A2 (15), A1 (14), M2 (13), M1 (12), M0 (11), M1 ' (12 '), M2 ' (13 '), A1 ' (14 '), A2 ' (15 ').Wherein, M1 (12), M1 ' (12 '); M2 (13), M2 ' (13 '); A1 (14), A1 ' (14 '); A2 (15), A2 ' (15 ') are homonymy electrode and use the lead short circuit; M0 (11) is the static spontaneous potential (SSP) measurement electrode; M2 (13), M2 ' (13 '), M1 (12), M1 ' (12 ') are a pair of monitor electrode; A2 (15), A2 ' (15 '), A1 (14), A1 ' (14 ') are a pair of bucking electrode; Electrode N (16) places at a distance; Each homonymy electrode, electrode M0 (11) and electrode N (16) are connected with measuring circuit by lead.

The function that measuring circuit realizes is: set up an electric field and measure the potential difference between each electrode in the electric field simultaneously in the stratum, and calculate the numerical value of the static spontaneous potential (SSP) that obtains the stratum by one-chip computer.Described measuring circuit 20 is made of following circuit: operation amplifier circuit 21; Operation amplifier circuit 22; Signal operation amplifier circuit 23; Variable connector and A/D analog to digital conversion circuit 24; One-chip computer 25; D/A D/A converting circuit 26.One-chip computer 25 is that the size according to Δ Vm provides electric current between bucking electrode and loop electrode, makes Δ Vm level off to zero; And level off to the numerical value that calculates the static spontaneous potential (SSP) on stratum zero time at Δ Vm.

The functional description of each circuit is as follows:

Potential difference signal on operation amplifier circuit 22 magnifying electrode M0 (11), the N (16);

Potential difference signal on operation amplifier circuit 23 magnifying electrode M1 (12), the M2 (13);

Variable connector and A/D analog to digital conversion circuit 24 are finished the conversion of analog signal/data signal;

One-chip computer 25 is finished instrument is carried out system control and to the processing of survey data;

The D/A D/A converting circuit is finished the conversion of data signal/analog signal;

Operation amplifier circuit 21 provides focus current Ip to electrode A 1 (14), A2 (15).

Operating principle of the present utility model:

One-chip computer 25 control D/A change-over circuits 26 produce a focus current Ip signal, this signal exports to after operation amplifier circuit 21 amplifies on the electrode A 1, A2 of electrode system, just in pit shaft, set up an electric field, the electric field stack that natural potential is set up in this electric field and the pit shaft also is the stack of two electric fields reaching the potential difference VM0 and the Δ VM that produce between M1 and the M2 between electrode M0 and the N; VM0 and Δ VM signal are converted to data signal by variable connector and A/D change-over circuit 24 again and deliver in the one-chip computer after operation amplifier circuit 22,23 amplifies respectively; One-chip computer is adjusted the size of D/A change-over circuit output signal Ip according to the size of Δ VM signal, makes Δ VM/VM0≤0.0001.After Δ VM satisfied Δ VM/VM0≤0.0001 and requires, the numerical value of the signal VM0 that measures on electrode M0 and N was the numerical approximation of static spontaneous potential (SSP) SSP.One-chip computer transfers to static spontaneous potential (SSP) SSP measured value in the special-purpose well logging ground instrument (28) of well logging by the log well special-purpose transfer of data instrument 27 and the special-purpose armored cable of logging well and carries out record.

Can calculate formation water resistivity Rw or formation water salinity Cw by formula (6) or (7).

$\mathrm{Rw}={10}^{-\frac{\mathrm{SSP}}{K}}\×\mathrm{Rmf}---\left(6\right)$

Or $\mathrm{Cw}={10}^{\frac{\mathrm{SSP}}{K}}\×\mathrm{Cmf}---\left(7\right)$

In the formula: K----static spontaneous potential (SSP) coefficient, in the time of 25 ℃, K=70.7

The SSP----static spontaneous potential (SSP)

The Rmf----mud filtrate resistivity

Embodiment 2:

The theory diagram of the utility model high resolution ratio static natural potential well SSP logging instrument embodiment 2, as shown in Figure 5.In Fig. 5: electrode system part 10 comprises: electrode M0 (11), electrode M1 (12), electrode M1 ' (12 '), electrode M2 (13), electrode M2 ' (13 '), electrode A 1 (14), electrode A 1 ' (14 '), electrode A 2 (15), electrode N (16).

The utility model is by static spontaneous potential (SSP) SSP electrode system 10 and measuring circuit 20.Described electrode system 10 is to constitute the electrode system main body by 7 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A1 (14), M2 (13), M1 (12), M0 (11), M1 ' (12 '), M2 ' (13 '), A1 ' (14 ').Wherein, M1 (12), M1 ' (12 '); M2 (13), M2 ' (13 '); A1 (14), A1 ' (14 ') are homonymy electrode and use the lead short circuit; M0 (11) is the static spontaneous potential (SSP) measurement electrode; M2 (13), M2 ' (13 '), M1 (12), M1 ' (12 ') are a pair of monitor electrode; A1 (14), A1 ' (14 ') are a pair of bucking electrode; A2 (15) is a loop electrode; Electrode A 2 (15) and electrode N (16) place at a distance; Each homonymy electrode, electrode M0 (11), electrode A 2 (15) and electrode N (16) are connected with measuring circuit by lead.

Measuring circuit 20 is identical with embodiment 1, so repeat no more.

The difference of two kinds of electrode systems among embodiment 1 and the embodiment 2 is: A2 (15) electrode both can be used as the two ends (referring to Fig. 4) that a pair of homonymy electrode A2 (15), A2 ' (15 ') are symmetrically placed in the electrode system main body, also can be used as a single electrode A 2 (15) and place (referring to Fig. 5) outside the electrode system main body, these two kinds of electrode system conjunction measuring circuit 20 all can be realized purpose of the present invention.

The utility model is logged well in the open hole well of finishing drilling, and the log data that obtains is referring to Fig. 6 and Fig. 7.

Fig. 6 is the formation water salinity comparison diagram that the formation water salinity Cw that calculates of the utility model institute survey data and laboratory obtain by core analysis.In Fig. 6: the formation water salinity that Cw--calculates with the SSP opisometer, horizontal straight line are represented the formation water salinity of lab analysis; SP--nutural potential logging curve; SSP--high resolution ratio static natural potential well log; RMG--MINV curve; RMN--micro-normal log curve.

Fig. 7 is the comparison diagram of the curve data of the utility model is surveyed in a bite open hole well curve data and traditional natural potential SP well logging and other logging method.In Fig. 7: CAL--calliper log curve; GR--natural gamma ray logging curve; AC--acoustic velocity logging curve; RMG--MINV curve; RMN--micro-normal log curve; SP--nutural potential logging curve; SSP--high resolution ratio static natural potential well log; MSFL--micro-SFL (MSFL) curve; LL3D--high-resolution deep lateral log curve; LL3S--high-resolution shallow lateral logging curve.

By the log data of above-mentioned two mouthfuls of wells, can obtain to draw a conclusion:

1, located and can be seen by (1) (2) (3) among Fig. 6, on the clean sandstone stratum, the formation water salinity Cw that utilizes institute of the present invention survey data to calculate conforms to by the formation water salinity that core analysis obtains with the laboratory.Illustrate that the utility model has solved the difficult problem that can directly measure formation water resistivity Rw or formation water salinity Cw for a long time without any a kind of logger.

2, the resolution ratio of the resolution ratio of data that the utility model is surveyed and micronormal, MINV curve is suitable.Referring to Fig. 7.For example: (1) is located in Fig. 7, and the thickness on this stratum is about 0.3 meter, and curve that the present invention surveys has tangible reflection, and traditional SP curve is in the almost not reflection of this layer.The resolution ratio of this explanation curve that the utility model is surveyed has reached requirement of the present invention.

3,, when utilizing the utility model institute survey data to calculate formation water resistivity Rw or formation water salinity Cw, carry out necessary shale and proofread and correct for containing the heavier reservoir of shale.

Illustrate by Fig. 6, actual measurement log data shown in Figure 7: above-mentioned embodiment has realized the purpose of this utility model.

Claims (4)

1, a kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system (10) and measuring circuit (20), it is characterized in that: described electrode system (10) is to constitute the electrode system main body by 9 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A2 (15), A1 (14), M2 (13), M1 (12), M0 (11), M1 ' (12 '), M2 ' (13 '), A1 ' (14 '), A2 ' (15 '); Wherein, M1 (12) and M1 ' (12 '); M2 (13) and M2 ' (13 '); A1 (14) and A1 ' (14 '); A2 (15) and A2 ' (15 ') are homonymy electrode and use the lead short circuit; M0 (11) is the static spontaneous potential (SSP) measurement electrode; M2 (13), M2 ' (13 ') and M1 (12), M1 ' (12 ') are a pair of monitor electrode; A2 (15), A2 ' (15 ') and A1 (14), A1 ' (14 ') are a pair of bucking electrode; Electrode N (16) places at a distance; Each homonymy electrode, electrode M0 (11) and electrode N (16) are connected with measuring circuit by lead.

2, a kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system (10), measuring circuit (20), it is characterized in that: described electrode system (10) is to constitute the electrode system main body by 7 electrode retaining collars that are embedded in the symmetric arrays on the insulating rod, and its ordering from top to bottom is: A1 (14), M2 (13), M1 (12), M0 (11), M1 ' (12 '), M2 ' (13 '), A1 ' (14 '); Wherein, M1 (12) and M1 ' (12 '); M2 (13) and M2 ' (13 '); A1 (14) and A1 ' (14 ') are homonymy electrode and use the lead short circuit; M0 (11) is the static spontaneous potential (SSP) measurement electrode; M2 (13), M2 ' (13 ') and M1 (12), M1 ' (12 ') are a pair of monitor electrode; A1 (14), A1 ' (14 ') are bucking electrode; A2 (15) is a loop electrode; Electrode A 2 (15) and electrode N (16) place at a distance; Each homonymy electrode, electrode M0 (11), electrode A 2 (15) and electrode N (16) are connected with measuring circuit by lead.

3, high resolution ratio static natural potential well logging instrument according to claim 1 and 2, described measuring circuit (20), it is made up of operation amplifier circuit (21), operation amplifier circuit (22), signal operation amplifier circuit (23), variable connector and A/D analog to digital conversion circuit (24), one-chip computer (25) and D/A D/A converting circuit (26), it is characterized in that: one-chip computer (25) is that the size according to the potential difference Δ Vm that produces between electrode M1, the M2 provides electric current between bucking electrode and loop electrode, makes Δ Vm level off to zero; And level off to the numerical value that calculates the static spontaneous potential (SSP) on stratum zero time at Δ Vm.

4, high resolution ratio static natural potential well logging instrument according to claim 1 and 2, it is characterized in that: it comprises:

The input of operation amplifier circuit (21) is connected with D/A D/A converting circuit (26), and output is connected with electrode A 2 (15) with electrode A 1 (14);

The input of operation amplifier circuit (22) is connected with electrode N (16) with electrode M0 (11), and output is connected with A/D analog to digital conversion circuit (24) with variable connector;

The input of signal operation amplifier circuit (23) is connected with electrode M2 (13) with electrode M1 (12), and output is connected with A/D analog to digital conversion circuit (24) with variable connector;

The output of variable connector and A/D analog to digital conversion circuit (24) is connected with one-chip computer (25).

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