CN104931821A - Sensor probe for measuring electrical parameters of underground rock - Google Patents

Abstract

The invention provides a sensor probe for measuring electrical parameters of an underground rock. The sensor probe comprises an emitter electrode, a collector electrode and a voltage source of the emitter electrode, and the voltage source of the emitter electrode is connected with the collector electrode and the emitter electrode via leads. The sensor probe is characterized by also comprising a shielding electrode and a voltage source of the shielding electrode, the shielding electrode is annular, the emitter electrode is arranged in a ring of the shielding electrode, and the voltage source of the shielding electrode is connected with the collector electrode and the shielding electrode via leads. The emitter electrode and the collector electrode are respectively arranged at the two sides of the sampled underground rock opposite to each other, the voltage source of the shielding electrode is loaded on the shielding electrode, and thus, current flowing out of the emitter electrode can penetrate a conductive slurry in parallel and reaches the collector electrode in the rock. The sensor probe can measure underground core samples in real time, and accurately and effectively obtains core information of the stratum in real time.

Description

Rock in Well electric parameter measurement sensor probe

Background technology

Core electrical quantity has very important meaning for correction logging trace, and traditional core electric parameter measurement method needs to measure sending ground experiment room after core sample collection back to.Measure the sensor probe adopted and comprise emitting electrode and passive electrode, emitting electrode and passive electrode is connected by a voltage source, the electric current that emitting electrode flows out arrives passive electrode through rock, electric current can be subject to the impact of rock resistivity and specific inductive capacity in the process through rock, thus impedance loop can be caused to change, just can be back-calculated to obtain resistivity and the specific inductive capacity of core to be measured according to the resistance value measured by setting up impedance loop and the relation between rock resistivity and specific inductive capacity.Send laboratory back to because traditional metering system needs to take out core from down-hole, this process causes measuring period long, and cost greatly, and can not the resistivity of Real-time Obtaining core sample and specific inductive capacity.

In down-hole, the real-time acquisition stratum core information of measurement while drilling energy is carried out to core sample, but subsurface environment is different from the measurement environment in laboratory, measurement can be subject to the impact of very many factors, first be that down-hole is filled with conductive drilling mud solution, now because the resistivity of rock is far away higher than mud resistivity, the conduct electricity flowed out from emitting electrode fails to be convened for lack of a quorum directly through conductive drilling mud arrival passive electrode, and seldom have electric current can penetrate mud to enter rock interior, this must cause popping one's head in and cannot measure the electrical quantity of rock.

Electric current due to the outflow of conductive drilling mud meeting blocking electrode enters the rock of high resistant, thus causes the electrical quantity change of instrument to rock insensitive.

Summary of the invention

Technical matters to be solved by this invention is, provides a kind of sensor probe configuration being applicable to subsurface environment.

The present invention for solving the problems of the technologies described above adopted technical scheme is, Rock in Well electric parameter measurement sensor probe, comprise emitting electrode, passive electrode, emitting electrode voltage source, emitting electrode voltage source is connected with passive electrode, emitting electrode respectively by wire, it is characterized in that, also comprises guarded electrode, guarded electrode voltage source, guarded electrode is ring texture, in the ring of the guarded electrode that emitting electrode is arranged on; Guarded electrode voltage source is connected with passive electrode, guarded electrode respectively by wire; Emitting electrode and passive electrode are arranged on the rock both sides of sampling down-hole in opposite directions;

Guarded electrode voltage source loads on the shield electrode, and the electric current that emitting electrode is flowed out can penetrate conductive drilling mud abreast and enter rock interior arrival passive electrode.

The present invention adopts guarded electrode form can penetrate conductive drilling mud to the electric current focusing on conduction current and make emitting electrode flow out and enters rock interior and arrive passive electrode and form loop, avoids conductive drilling mud and blocks the situation of electric current by rock.The galvanic circle of emitting electrode and passive electrode, through rock interior, provides the foundation for obtaining rock electrical quantity by impedance on the galvanic circle of measuring emitting electrode and passive electrode afterwards.

The invention has the beneficial effects as follows, be applicable to the sensor probe of subsurface environment, can measure in real time in down-hole core sample, accurate, efficient, real-time acquisition stratum core information.

Accompanying drawing explanation

Fig. 1 is the vertical view of the transverse section of sensor probe when measuring again.

Fig. 2 is the schematic diagram of emitting electrode and guarded electrode.

Fig. 3 be between emitting electrode and passive electrode loop resistance with the relation schematic diagram of guarded electrode voltage.

Embodiment

The present invention adopts specific measure to guide electric current to penetrate conductive drilling mud and enter into rock interior, thus gathers and take the electrical quantity of rock interior out of.

While powering to emitting electrode, make to be relative noble potential around internal electrode by adding suitable voltage on the shield electrode, thus the electric current that compressing is flowed out from emitting electrode cannot conduct along conductive drilling mud, select suitable voltage and electrode form that electric current can be made to penetrate conductive drilling mud, enter into rock interior, arrive ground connection pole plate by rock.

As shown in Figure 1, the rock 1 of sensor probe of the present invention to sampling is utilized to carry out electric parameter measurement.Rock 1 is wrapped up by conductive drilling mud 2.Sensor probe of the present invention comprises emitting electrode 3, passive electrode 4, emitting electrode voltage source V ₂, guarded electrode 5, guarded electrode voltage source V ₁, guarded electrode 5 is ring texture, as shown in Figure 2, in the ring of the guarded electrode 5 that emitting electrode 3 is arranged on; Emitting electrode voltage source V ₂be connected with passive electrode 4, emitting electrode 3 respectively by wire, guarded electrode voltage source V ₁be connected with passive electrode 4, guarded electrode 5 respectively by wire; Emitting electrode 3 and passive electrode 4 are arranged on rock 1 both sides of sampling down-hole in opposite directions.

When conduction current or displacement current flow through rock 1, equivalence capacitor model can be regarded as between emitting electrode and passive electrode, the resistance value at electric capacity two ends changes along with the electrical quantity of rock, by measuring the resistance value at electric capacity two ends, in conjunction with accurate numerical simulation modeling, inverting the electrical quantity of rock can be obtained.

Need to illustrate, the effect of guarded electrode is the current potential by controlling around emitting electrode, thus restriction internal polar plate flows out the flow direction of electric current.Voltage ratio a=V above guarded electrode and emitting electrode ₁/ V ₂design for sensor probe is extremely important.

In order to the relation in voltage and emitting electrode loop on the effect of guarded electrode and guarded electrode is better described, take frequency of operation as 1KHz, mud resistivity ρ _mud=1.0e2 Ω m, specific inductive capacity are ε _{r_mud}=1.0 and rock resistivity be ρ _rOCK=1.0e8 Ω m, specific inductive capacity are ε _{r_ROCK}the situation of=1.0 is example, as shown in Figure 3:

Because frequency of operation is low frequency operating mode, so the current forms between the emitting electrode of probe and passive electrode is mainly conduction current, displacement current accounts for very little proportion.So only analyze the real part of impedance loop in figure 3, the active component namely in impedance.

As guarded electrode voltage and emitting electrode voltage ratio a=V ₁/ V ₂when=0, be equivalent to only have emitting electrode to power, the electric current of emitting electrode outflow in this case, directly flow into passive electrode along conductive drilling mud, now loop resistance value is close to Z _real=0 Ω, shows electric current not through rock interior.

As guarded electrode voltage and emitting electrode voltage ratio a=V ₁/ V ₂changing to about 0.8 from 0.2, in loop, resistance modulus value increases gradually, cause this is because the interior electrode of voltage compressing on guarded electrode flows out electric current inflow rock, due to the deficiency of voltage on guarded electrode, still have one part of current and flow along mud.This of voltage ratio change is interval, and we are called deficient focal region.

Work as a=V ₁/ V ₂change to this process of 1.0 from 0.8, in emitting electrode loop, resistance modulus value continues to increase, and in this interval the inside, along with increasing of mask voltage, the basic mountain of electric current that interior electrode flows out is all through rock.The now change of instrument to rock electrical quantity to be measured is the most responsive, and this is also the effect that our sensor probe is pursued.The electric current in this interval has reasonably been focused on inside rock, so we are called focal region this interval.

Along with mask voltage continue increase, work as a=V ₁/ V ₂when being greater than 1.01, due to the increase of guarded electrode voltage, the electric current of PARALLEL FLOW there will be interflow originally, is also in rock, there will be a focus exactly.Now interior electrode loop impedance is infinitely great, along with the continuation of peripheral voltage increases, interflow electric current can along interior electrode reversed flow, interior electrode loop resistive impedance value is reduced gradually by minus infinity, but because interior electrode no current flows into rock interior, so can not detect resistivity and the specific inductive capacity of rock.We called focal region this region of voltage.

Deficient focal region, focal region and the separatrix crossed between focal region are not a clear and definite point, but the interval that fuzzy, incomplete same between the focal region that different logging environment is corresponding, but it is identical for scanning for whole interval the curve tendency obtained, those skilled in the art according to different situations, different curves and can require between the focal region that definition is corresponding.

Can find out, when a>>1 time, because high voltage form can cause occurring focusing phenomenon, by current focusing in conducting mud pulp layer, can not better enter rock on the contrary; Deficient focusing phenomenon is there will be again on the contrary when a<<1 time; Only have and can realize Current Control effectively when a gets suitable value time, make electric current pass mud and enter rock, thus ensure that the electrical quantity of sensor probe to rock is the most responsive.Voltage ratio scope can change according to the situation difference measured.Those skilled in the art by controlling the voltage ratio of shielding electrode voltage source and emitting electrode voltage source flexibly, can ensure the adaptive faculty of probe to different test environments.

Sensor probe of the present invention can be operated in multifrequency pattern, and different frequency of operation is different for the susceptibility of different electrical quantitys to be measured, and adopting multifrequency pattern to combine can more accurate inverting rock electrical quantity.Under needing to set up each frequency of operation so before measuring, different resistivity and the lower corresponding impedance response of specific inductive capacity combination.For double frequency pattern:

First, two kinds of frequency f are set up by numerical evaluation ₁=10KHz, f ₂=1MHz is in various electricalresistivityρ=1000 ~ 1000000 Ω m and DIELECTRIC CONSTANT ε _rimpedance response Z (comprising real part and imaginary part) database under=1 ~ 80:

Z_f ₁_r_s(ρ,ε _r),Z_f ₁_i_s(ρ,ε _r),

Z_f ₂_r_s(ρ,ε _r),Z_f ₂_i_s(ρ,ε _r),

Z_f ₁_ r_s (ρ, ε _r) be frequency of operation f ₁certain electricalresistivityρ and DIELECTRIC CONSTANT ε _rthe real part of corresponding impedance response simulation value, Z_f ₁_ i_s (ρ, ε _r) be frequency of operation f ₁certain electricalresistivityρ and DIELECTRIC CONSTANT ε _rthe imaginary part of corresponding impedance response simulation value;

Z_f ₂_ r_s (ρ, ε _r) be frequency of operation f ₂certain electricalresistivityρ and DIELECTRIC CONSTANT ε _rthe real part of corresponding impedance response simulation value, Z_f ₂_ i_s (ρ, ε _r) be frequency of operation f ₂certain electricalresistivityρ and DIELECTRIC CONSTANT ε _rthe imaginary part of corresponding impedance response simulation value;

In detection process afterwards, obtain the impedance response probe value (comprising real part and imaginary part) under 2 kinds of frequencies:

Z_f ₁_r_m(ρ,ε _r),Z_f ₁_i_m(ρ,ε _r),

Z_f ₂_r_m(ρ,ε _r),Z_f ₂_i_m(ρ,ε _r)

Find optimum solution in a database, make following objective function minimum:

$f(\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_r)=\underset{j=1}{\overset{2}{\mathrm{\&Sigma;}}}\left\{\begin{array}{c}{W}_{\mathrm{rj}}\left|\right|Z\_f_j\_r\_m(\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_r)-Z\_f_j\_r\_s(\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_r)\left|\right|+\\ W_{\mathrm{ij}}\left|\right|Z\_f_j\_i\_m(\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_r)-Z\_f_j\_i\_s(\mathrm{\&sigma;},{\mathrm{\&epsiv;}}_r)\left|\right|\end{array}\right\}$

W _rj, W _ijbeing respectively weight coefficient, is empirical value.

By substituting in objective function to the impedance data under 2 kinds of frequencies of recording, ergodic data storehouse, finds the specific inductive capacity and resistivity that make the minimum correspondence of objective function, just can obtain the corresponding electrical quantity of oil-base mud.

Claims (1)

1. Rock in Well electric parameter measurement sensor probe, comprise emitting electrode, passive electrode, emitting electrode voltage source, emitting electrode voltage source is connected with passive electrode, emitting electrode respectively by wire, it is characterized in that, also comprise guarded electrode, guarded electrode voltage source; Guarded electrode is ring texture, in the ring of the guarded electrode that emitting electrode is arranged on; Guarded electrode voltage source is connected with passive electrode, guarded electrode respectively by wire; Emitting electrode and passive electrode are arranged on the rock both sides of sampling down-hole in opposite directions;

Guarded electrode voltage source loads on the shield electrode, and the electric current that emitting electrode is flowed out can penetrate conductive drilling mud abreast and enter rock interior arrival passive electrode.