CN100451680C - High resolution ratio static natural potential well logging instrument and its measuring method - Google Patents

Abstract

The present invention relates to a high resolution static spontaneous potential well logging instrument and a measuring method thereof. The well logging instrument comprises a static spontaneous potential (SSP) electrode system and a measuring circuit, wherein a main body of the electrode system is formed by that nine electrode collars are symmetrically inlaid in an insulating rod, the ordering is A2, A1, M2, M1, M0, M1', M2', A1' and A2' from top to bottom, M1 and M1', M2 and M2', A1 and A1', A2 and A2' are isonym electrodes and respectively form short connection by a conducting wire, M0 is a static spontaneous potential measuring electrode, an electrode N is arranged in a far place, and the isonym electrodes, the electrode M0 and the electrode N are connected with the measuring circuit through conducting wires; the measuring circuit provides electrical current for the place between the electrodes A1 and A2 according to the size of delta Vm to make the delta Vm to approach zero, and a number value of the stratum static spontaneous potential is calculated when the delta Vm approaches zero. The present invention has the performance of high resolution, can accurately measure information of the static spontaneous potential at thin reservoir beds larger than 0.3 meter, and reliable data information which describes characteristics of thin reservoir beds can be provided.

Description

Static natural potential well logging instrument and measuring method thereof

Invention field

The present invention relates to a kind of testing tool, be meant a kind of petroleum geology exploration well logging subsurface equipment, i.e. high resolution ratio static natural potential well logging instrument and measuring method thereof especially.

Background technology

The fundamental purpose of petroleum geology exploration well logging is to estimate the reservoir whether to contain oil or rock gas.Whether contain oil or three parameters the most basic of rock gas needs and estimate the reservoir, that is: the contained formation water resistivity in the resistivity of reservoir, factor of porosity and reservoir.The logging instrumentation that is used to measure reservoir resistivity has a series of instruments such as lateralog and induction instrument, and the logging instrumentation that is used to measure porosity of sandstones has logging instrumentations such as sound wave, density, neutron and nuclear magnetic resonance.And this parameter of formation water resistivity, having never had a kind of logging instrumentation since nineteen twenty-six begins to develop the petroleum geology exploration well logging can be used for directly measuring asking for, main experience by the reservoir evaluation personnel is estimated, the numerical value that this experience by the evaluation personnel estimates is insecure often, thereby causes the failure to reservoir evaluation.

In general, employed drilling mud all is a water-based mud in Process of Oil Well Drilling, so for the water-based mud petroleum drilling, the reason that spontaneous 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 reservoir 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 spontaneous potential SP well logger is as shown in Figure 1 in the petroleum geology exploration: among Fig. 1, and the 1--mudstone stratum; The mud-filled uncased hole of 2--; The 3--triumphant dress cable of logging well; The 4--sandstone formation; The 5--surface instrumentation of logging well; The 6--potential electrode; 7--ground reference electrode.

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

Facts have proved that the spontaneous 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 uncased hole, the mechanism that spontaneous potential SP produces as shown in Figure 2.In Fig. 2: the 1--mudstone stratum; The mud-filled uncased hole of 2--; 3--spontaneous 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, mud filtrate directly contacts with local water in the hole.Because under general situation, the resistivity Rmf of mud filtrate is greater than stratum resistivity of water Rw (the salinity Cmf of drilling mud filtrate is less than the salinity Cw of local water), and supposition mud filtrate and the contained salt of local water all be sodium chloride nacl, so:

A. at sandstone reservoir (4), chlorion Cl ^-With sodion Na ⁺Reservoir one side direction salinity low well mud one side higher from salinity spreads.Because chlorion Cl ^-Migration rate than sodion 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 sodion 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 mud filtrate, 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 adsorptive power is arranged, so chlorion Cl ^-Can't move, have only the sodion 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 mud filtrate, 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 (PD) because tight zone does not have hole not contain local 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---mud filtrate salinity

The Cw---reservoir 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 reservoir water salinity Cw with static spontaneous potential (SSP) SSP.And formation water resistivity Rw or reservoir water salinity Cw estimate the indispensable crucial parameter of reservoir oil saturation.

The defective of existing spontaneous potential SP measuring technique:

Existing spontaneous potential SP measuring principle is shown in Fig. 3-1, Fig. 3-2, wherein: the 1--mudstone stratum; Mud in the 2--pit shaft; 3--mud filtrate flushed zone; 4--sandstone virgin zone.

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 virgin zone equivalent resistance

The SSP---static spontaneous potential (SSP)

The SP---spontaneous potential

The Isp---spontaneous 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 spontaneous potential SP mainly is subjected to flushed zone (3) the equivalent resistance Rxo of reservoir and the influence of virgin zone (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 spontaneous 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 spontaneous potential SP to reduce.

So, existing spontaneous 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 spontaneous potential SP logging trace amplitude can become very little even without any reaction (referring to Fig. 7).So existing spontaneous potential SP logging trace can not be directly used in quantitative Analysis formation water resistivity Rw, up to the present, also can measure formation water resistivity Rw directly and accurately without any a kind of other logging instrumentation.

Summary of the invention

The object of the present invention is to provide a kind of high resolution ratio static natural potential well SSP well logger and measuring method thereof, it can solve the difficult problem that can directly measure formation water resistivity Rw for a long time without any a kind of logging instrumentation, particularly, for the pure reservoir of thickness greater than 0.3 meter, institute of the present invention 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: $\begin{array}{c}\frac{\mathrm{Rm}}{\mathrm{Rm}+\mathrm{Rsh}+\mathrm{Rxo}+\mathrm{Rt}}\≈1\\ \mathrm{SP}\≈\mathrm{SSP}\end{array}---\left(5\right)$

(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-based 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-based 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 present invention, 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.

Technical scheme of the present invention is:

A kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system, metering 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 offset spread on the insulation 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) potential electrode; M2, M2 ', M1, M1 ' are a pair of monitor electrode; A2, A2 ', A1, A1 ' are a pair of guarded electrode; Electrode N places at a distance; Each homonymy electrode, electrode M0 and electrode N are connected with metering circuit by lead.

Another technical scheme of the present invention is:

A kind of high resolution ratio static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system, metering 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 offset spread on the insulation 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) potential electrode; M2, M2 ', M1, M1 ' are a pair of monitor electrode; A1, A1 ' are a pair of guarded 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 metering circuit by lead.

Wherein, described metering circuit circuit is made up of operation amplifier circuit, operation amplifier circuit, signal operation amplifier circuit, multi-way switch 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 guarded 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.

A kind of high resolution ratio static natural potential well logging method, it is characterized in that: it comprises: electrode system is placed in the uncased hole that is full of drilling mud; The spontaneous current that flows along pit shaft flow through electrode M1, M1 ', M2, M2 ' just can produce potential difference (PD) Δ Vm between electrode M1, M2; Metering circuit provides electric current according to the size of Δ Vm between guarded electrode and loop electrode, make Δ Vm level off to zero; Δ Vm levels off to zero, and electrode M1, M2 equipotential are described, no longer includes electric current flow through electrode M1, M2; At this moment, the potential difference (PD) between electrode M0 and the electrode N is static spontaneous potential (SSP) SSP.

Basic functional principle of the present invention is:

After well logger is transferred to the pit shaft that is full of water-based mud by the well logging sheathed cable, along the spontaneous current Isp that flows in the pit shaft when flowing through regional between electrode M1, M2, just can produce potential difference (PD) Δ Vm between electrode M1, the M2, metering circuit was added to electrode A 1, A2 is last and produces opposite, an equal-sized electric current with spontaneous current Isp polarity in pit shaft according to suitable current signal Ip of size output of Δ Vm this moment, make the potential difference (PD) 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 (PD) 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 (PD) Δ Vm between electrode M1, the M2 levels off to zero the time, the potential difference (PD) between electrode M0 and the electrode N is static spontaneous potential (SSP) SSP.

Can calculate formation water resistivity Rw or reservoir 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

The invention has the advantages that: the invention solves the difficult problem that directly to measure formation water resistivity Rw or reservoir water salinity Cw for a long time without any a kind of logging instrumentation.Because the present invention 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 spontaneous potential SP measuring method synoptic diagram;

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

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

Fig. 4 is the theory diagram of high resolution ratio static natural potential well SSP well logger embodiment 1 of the present invention;

Fig. 5 is the theory diagram of high resolution ratio static natural potential well SSP well logger embodiment 2 of the present invention;

Fig. 6 is the reservoir water salinity comparison diagram that the reservoir water salinity Cw that calculates of institute of the present invention survey data and laboratory obtain by core analysis;

Fig. 7 is the logging trace data of the present invention in actual uncased hole and the comparison diagram of the curve data of traditional spontaneous potential SP well logging and other logging methods.

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

Embodiment 1:

The theory diagram of high resolution ratio static natural potential well SSP well logger embodiment 1 of the present invention, 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 present invention is made up of static spontaneous potential (SSP) SSP electrode system 10, metering 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 offset spread on the insulation 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) potential 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 guarded electrode; Electrode N (16) places at a distance; Each homonymy electrode, electrode M0 (11) and electrode N (16) are connected with metering circuit by lead.

The function that metering circuit realizes is: set up an electric field and measure the potential difference (PD) 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 metering circuit 20 is made of following circuit: operation amplifier circuit 21; Operation amplifier circuit 22; Signal operation amplifier circuit 23; Multi-way switch 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 guarded 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);

Multi-way switch and A/D analog to digital conversion circuit 24 are finished the conversion of simulating signal/digital signal;

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

The D/A D/A converting circuit is finished the conversion of digital signal/simulating signal;

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

Principle of work of the present invention:

One-chip computer 25 control D/A change-over circuits 26 produce a focusing 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 spontaneous potential is set up in this electric field and the pit shaft also is the stack of two electric fields reaching the potential difference (PD) 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 digital signal by multi-way switch 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 surface instrumentation (28) of well logging by the log well special-purpose data transmission instrument 27 and the special-purpose sheathed cable of logging well and carries out record.

Can calculate formation water resistivity Rw or reservoir 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 high resolution ratio static natural potential well SSP well logger embodiment 2 of the present invention, 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 present invention is by static spontaneous potential (SSP) SSP electrode system 10 and metering 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 offset spread on the insulation 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) potential electrode; M2 (13), M2 ' (13 '), M1 (12), M1 ' (12 ') are a pair of monitor electrode; A1 (14), A1 ' (14 ') are a pair of guarded 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 metering circuit by lead.

Metering 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 present invention logs well in the uncased hole of finishing drilling, and the logging trace data that obtains is referring to Fig. 6 and Fig. 7.

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

Fig. 7 is the comparison diagram of the curve data of the present invention surveyed in a bite uncased hole curve data and traditional spontaneous potential SP well logging and other logging methods.In Fig. 7: CAL--section gauge logging curve; GR--natural gamma ray logging curve; AC--acoustic velocity logging curve; RMG--MINV curve; RMN--micro-normal log curve; SP--natural potential logging curve; SSP--high resolution ratio static natural potential well logging trace; MSFL--micro-SFL (MSFL) curve; LL3D--high resolving power deep lateral logging curve; LL3S--high resolving power shallow lateral logging curve.

By the logging trace 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 reservoir water salinity Cw that utilizes institute of the present invention survey data to calculate conforms to by the reservoir water salinity that core analysis obtains with the laboratory.Illustrate and the invention solves the difficult problem that directly to measure formation water resistivity Rw or reservoir water salinity Cw for a long time without any a kind of logging instrumentation.

The resolution of the resolution of data that 2, the present invention surveys 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 of this explanation curve that the present invention surveys has reached requirement of the present invention.

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

Illustrate by Fig. 6, actual measurement logging trace data shown in Figure 7: above-mentioned embodiment has realized purpose of the present invention.

Claims (7)

1, a kind of static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system (10), metering 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 offset spread on the insulation 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) potential 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 guarded electrode; Electrode N (16) places at a distance; Each homonymy electrode, electrode M0 (11) and electrode N (16) are connected with metering circuit by lead.

2, a kind of static natural potential well logging instrument, it includes static spontaneous potential (SSP) SSP electrode system (10), metering 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 offset spread on the insulation 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) potential electrode; M2 (13), M2 ' (13 ') and M1 (12), M1 ' (12 ') are a pair of monitor electrode; A1 (14), A1 ' (14 ') are guarded 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 metering circuit by lead.

3, static natural potential well logging instrument according to claim 1 and 2, described metering circuit (20), it is made up of operation amplifier circuit (21), operation amplifier circuit (22), signal operation amplifier circuit (23), multi-way switch 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 Δ Vm provides electric current between guarded 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, static natural potential well logging instrument according to claim 1 and 2, it is characterized in that: it comprises:

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

The input end of operation amplifier circuit (22) is connected with electrode N (16) with electrode M0 (11), and output terminal is connected with A/D analog to digital conversion circuit (24) with multi-way switch;

The input end of signal operation amplifier circuit (23) is connected with electrode M2 (13) with electrode M1 (12), and output terminal is connected with A/D analog to digital conversion circuit (24) with multi-way switch;

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

5, a kind of static spontaneous potential (SSP) logging method, it is characterized in that: it comprises: electrode system is placed in the uncased hole that is full of drilling mud; The spontaneous current that flows along pit shaft flow through electrode M1 (12), M1 ' (12 '), M2 (13), M2 ' (13 ') just can produce potential difference (PD) Δ Vm between electrode M1 (12), M2 (13); Metering circuit provides electric current according to the size of Δ Vm between guarded electrode and loop electrode, make Δ Vm level off to zero; Δ Vm levels off to zero, and electrode M1, M2 equipotential are described, no longer includes electric current flow through electrode M1, M2; At this moment, the potential difference (PD) between electrode M0 and the electrode N is static spontaneous potential (SSP) SSP.

6, static spontaneous potential (SSP) logging method according to claim 5, it is characterized in that: it comprises:

A), when well logger after sheathed cable transfers to the pit shaft that is full of water-based mud by well logging, when flowing through regional between electrode M1, M2, just can produce potential difference (PD) Δ Vm along the spontaneous current Isp that flows in the pit shaft between electrode M1, the M2;

B), this moment metering circuit, suitable current signal Ip of size output according to Δ Vm is added to electrode A 1, A2 is last and produces opposite, an equal-sized electric current with spontaneous current Isp polarity in pit shaft, make the potential difference (PD) Δ Vm between electrode M1, the M2 level off to zero, i.e. electrode M1, M2 equipotential;

C), 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 to this zone in is infinity, that is:

Rm＞＞Rsh+Rxo+Rt

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

D), the potential difference (PD) between this moment electrode M0 and electrode N is:

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

E), when the potential difference (PD) Δ Vm between electrode M1, the M2 levels off to zero the time, the potential difference (PD) between electrode M0 and the electrode N is static spontaneous potential (SSP) SSP.

7, static spontaneous potential (SSP) logging method according to claim 5, it is characterized in that: it comprises: can calculate formation water resistivity Rw or reservoir water salinity Cw according to following 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

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