CN103135139A - Method for measuring stratum resistivity outside drivepipe through metal drivepipe - Google Patents

Abstract

Provided is a method for measuring stratum resistivity outside a drivepipe through a metal drivepipe. The method for measuring stratum resistivity outside the drivepipe through the metal drivepipe comprises the following steps: adopting to measure two groups of independent excitation current sources with different frequencies, one group of current source which is used for injecting current to the stratum is exerted on the ground between a well opening drivepipe and a return circuit electrode, and measuring the resistivity of the stratum outside the drivepipe; the other group of current source which is used for measuring uniformity of the drivepipe and eliminating influence while measuring the stratum resistivity is exerted under a well on a measuring drivepipe, the two groups signal sources adopt two signals with different frequencies between 0-15 Hz, simultaneously exert on the drivepipe to measure, and finally utilizes the following formula to calculate a visual resistivity of an objective stratum. By using a double power supply incentive method, the method for measuring stratum resistivity outside the drivepipe through the metal drivepipe avoids transmitting drive signals to the well through well-measuring cables, avoids power damage caused by large current while flowing through the well-measuring cables, and eliminates the influence of measuring signals caused by the drive signals and also caused by mutual connection in a coupling mode between cable cores.

Description

A kind of method that sees through the nonlocal layer resistivity of metal sleeve measurement sleeve pipe

Technical field

The present invention relates to the In Oil Field Exploration And Development well logging, particularly a kind of method that sees through the nonlocal layer resistivity of metal sleeve measurement sleeve pipe.

Background technology

Formation resistivity is the important parameter of oil field prospecting difference oil-water-layer, for oil reservoir identification, and crude oil reserve, remaining oil saturation, the oil reservoir dynamic evaluation is significant.The layer resistivity surveying instrument adopts the electrical log instrument in the bore hole borehole measurement traditionally, in cased well because the shielding action electrical log of metal sleeve to electric field is difficult to implement.The resistivity that adopts electric measuring method to measure metal sleeve outer stratum is an important research field of resistivity logging in recent years.

Nineteen thirty-nine, USSR (Union of Soviet Socialist Republics) Alpin has proposed to measure differential voltage with three electrodes in sleeve pipe, thereby estimates to leak into the electric current on stratum, calculates formation resistivity, realizes the purpose of metal sleeve well logging.Yet fail to drop into concrete enforcement because there is following defective in this patent: 1) on principle, this scheme only can obtain the relative conductivity on stratum, and can not record the absolute value of formation conductivity; 2) this scheme can not determine out that the variation of casing thickness and sleeve pipe conductivity is on the impact of measurement result; 3) the spread of electrodes selection is improper, and is very large with desirable spread of electrodes difference, can produce significant impact to measurement result; 4) Alpin does not recognize, in order to eliminate electric field distortion to the impact of voltage measurements, must maintain a certain distance between galvanic electrode and mud stone electrode.

The fundamental measurement principle that proposes in patent document US2459196 is that an electric current is flowed along sleeve pipe under certain condition, causes current leakage in the stratum, by measuring current leakage, can determine the resistivity on stratum.And current leakage can be estimated by the voltage drop that mensuration is placed between each electrode at the place of different depth in oil well.

Patent document US2729784 has illustrated that a kind of mensuration leaks into the method for the electric current on stratum.Lay 3 potential electrode a along the sleeve pipe equidistant intervals, b, c, on opposite both direction electric current the galvanic electrode sprue bushing of the both sides by being placed in potential electrode, numerical value at central electrode b position leakage current is by measuring electrode a, between b and electrode b, the voltage drop between c, and calculate that difference between two voltage drops obtains.

Patent document FR2207278 proposes to use three even potential electrode spaced apart to be used for measuring leakage current, but also a kind of method that comprises two steps has been described: a first step, emitting electrode and return electrode nearby form the loop, be used for measuring the resistance of the casing section that is limited by each externally measured electrode, electric current can be ignored along the mobile electric current that consequently leaks into the stratum of sleeve pipe; And a second step, emitting electrode and at a distance return electrode form the loop, electric current can leak to the stratum.

Patent document US6765387 proposed a kind of do not need the scale step but can the Fast Measurement sleeve pipe method of outer formation resistivity.Lay respectively two couples of potential electrode C, D and E, F between three galvanic electrode B, M of instrument, A, adjust respectively the electric current on Injection Current electrode B, M, A, make the voltage of potential electrode C, D and E, F reduce to zero, the formation apparent resistivity at measurement point M place is to estimate by the upper electric current that injects of galvanic electrode M.

Patent document US6603314 proposes to measure with two electric currents while sprue bushings the method for the outer formation resistivity of sleeve pipe.at first of instrument, lay between the second galvanic electrode three can with the potential electrode of sleeve pipe good contact, and lay a loop electrode on ground away from sleeve pipe well head place, simultaneously first, add frequency on the second galvanic electrode identical, the electric current that phase place is different, the numerical value of the outer formation resistivity of sleeve pipe is voltage amplitude and the phase place between first and second potential electrode, voltage amplitude and phase place between second and the 3rd potential electrode, amplitude and the phase place of the electric current that first galvanic electrode injects, amplitude and the phase place of the electric current of second galvanic electrode injection, the common decision of the second order difference potential difference (PD) of potential electrode and electrical conductance of cable rate.

Above art methods has solved unevenness, electrode position, the impact of spacing on measuring of measuring the method for formation resistivity outside metal sleeve and having considered metal sleeve, the method of logging efficiency and the computing formula of formation resistivity have been proposed to improve, has important use value, and have commercially produced product to come out, but there are following technical limitation in present technology and product:

1) exciting current is all to be sent to the down-hole by cable, has caused huge power attenuation on cable;

2) for fear of the intercoupling of signal between cable core, exciting signal frequency is unfavorable for the inhibition of low-frequency noise less than 1Hz.

The result of above factor effect makes very difficult raising of effective exciting current on actual injection stratum, and the low-frequency noise impact is larger, and the Detection of Weak Signals precision is difficult to improve, and finally makes effective formation resistivity measurement range less, usually about 0～50 ohm meter.

Summary of the invention

In order to overcome the defective of above-mentioned prior art, the object of the present invention is to provide a kind of method that metal sleeve is measured the nonlocal layer resistivity of sleeve pipe that sees through, adopt the dual power supply inspiring methods to avoid pumping signal is transferred to the down-hole through logging cable, avoided large electric current to flow through power attenuation that logging cable causes has been eliminated pumping signal that intercoupling of signal between cable core cause to the impact of measuring-signal.

In order to achieve the above object, technical scheme of the present invention is:

A kind of method that sees through the nonlocal layer resistivity of metal sleeve measurement sleeve pipe comprises the following steps:

The connection of step 1, parts:

S1 is the ground excitation current source, is connected between exciting electrode E1 and N1, is used for by sleeve pipe to the stratum Injection Current, S2 is the down-hole excitation current source, be connected between exciting electrode E2 and N2, for Injection Current on the sleeve pipe between E2 and N2, this electric current is measured by reometer A; C, D, E are potential electrode, and the voltage drop when flowing through sleeve pipe for the measurement electric current on sleeve pipe is measured by voltage table V1 between C, D, is measured by V2 between D, E; R and G are a pair of casing potential potential electrode, and G is Zero potential reference, and on sleeve pipe, R point current potential is measured by voltage table VR; E1 is positioned at the wellhead casing pipe wall, and if the embedding and underground wet soil layer of N1 and G when in 200 meters, offset well being arranged near the target well, or is placed in offset well muzzle tube wall with N1; E1, N1 and G are fixed electordes, and motionless in whole during well logging after placing, other potential electrode are traveling electrodes, move with subsurface equipment in during well logging, and guarantee reliably to contact with internal surface of sleeve pipe when measuring;

Step 2, open excitation current source S1, by electrode pair E1 and N1 Injection Current in the stratum, this electric current is the sinusoidal ac signal of 0 ~ 15Hz, in the situation that the technical conditions license should make this electric current have larger numerical value as far as possible, and should be greater than 10A;

Step 3, open down-hole excitation current source S2, to the sleeve pipe Injection Current between electrode E2 and N2, this electric current is direct current, and the direction of switch current periodically, and this electric current should adopt large as far as possible numerical value, should be greater than 10A;

The output current A of step 4, measurement S2; Voltage V1 between sleeve pipe top electrode C and D, the voltage V2 between electrode D and E, and the electrode R casing potential VR of place, V1 and V2 all comprise two kinds of frequency components, measure respectively the effective value of the response signal of S1 and S2 excitation generation

With

With

Step 5, utilize following formula to calculate the apparent resistivity of formation at target locations

$\mathrm{Ra}=K\·V_{R}A(\frac{\stackrel{\‾}{V}1}{\stackrel{\‾}{V}1}-\frac{\tilde{V}2}{\stackrel{\‾}{V}2})$

In formula, Ra is formation apparent resistivity, and K is the apparent resistivity conversion coefficient of instrument, and A is the output current of excitation current source S2,

For current source S1 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S1 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe;

For current source S2 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S2 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe.

The present invention adopts two groups of separate current source forcings of different frequency to measure, and one group of current source puts between wellhead casing pipe and loop electrode on ground, is used for to the stratum Injection Current, measures the nonlocal layer resistivity of sleeve pipe; Another group current source puts on the measuring section sleeve pipe in the down-hole, and in order to the impact that the unevenness of measuring the elimination sleeve pipe is measured formation resistivity, two groups of signal sources adopt the signal of two different frequencies between 0～15Hz, act on sleeve pipe simultaneously and measure.The present invention has following effect:

1, eliminate the power attenuation of exciting current on logging cable, be conducive to reduce the output power to excitation current source, increased exciting current;

2, eliminate intercoupling of pumping signal and measuring-signal on the cable, can adopt the excitation of 1 ~ 15Hz low frequency signal, be conducive to improve the accuracy of detection of feeble signal;

3 adopt the dual power supply double frequency excitation, and double frequency is measured simultaneously, helps to improve logging operation efficient.

Comprehensive above factor, method provided by the invention is conducive to reduce the demanded power output to excitation current source, the electric current on stratum and the scale electric current on sleeve pipe are injected in increase, improve the signal to noise ratio (S/N ratio) of measuring-signal, increase the effective range of the outer formation resistivity of metal sleeve, improve logging speed and logging efficiency.Using the earth's surface that is limited in of this method should be continuous to the sleeve pipe between measuring section, and good conducting property is arranged, and sleeve pipe and sleeve pipe also should have the good electrical conduction between outer stratum, do not have insulating medium.

Description of drawings

Accompanying drawing is measurement connection diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, of the present invention doing is described in detail.

A kind of method that sees through the nonlocal layer resistivity of metal sleeve measurement sleeve pipe comprises the following steps:

The connection of step 1, parts: with reference to Fig. 1:

S1 is the ground excitation current source, is connected between exciting electrode E1 and N1, is used for by sleeve pipe to the stratum Injection Current, S2 is the down-hole excitation current source, be connected between exciting electrode E2 and N2, for Injection Current on the sleeve pipe between E2 and N2, this electric current is measured by reometer A; C, D, E are potential electrode, and the voltage drop when flowing through sleeve pipe for the measurement electric current on sleeve pipe is measured by voltage table V1 between C, D, is measured by V2 between D, E; R and G are a pair of casing potential potential electrode, and G is Zero potential reference, and on sleeve pipe, R point current potential is measured by voltage table VR; E1 is positioned at the wellhead casing pipe wall, and if the embedding and underground wet soil layer of N1 and G when in 200 meters, offset well being arranged near the target well, or is placed in offset well muzzle tube wall with N1; E1, N1 and G are fixed electordes, and motionless in whole during well logging after placing, other potential electrode are traveling electrodes, move with subsurface equipment in during well logging, and guarantee will reliably contact with internal surface of sleeve pipe when measuring;

Step 2, open excitation current source S1, by electrode pair E1 and N1 Injection Current in the stratum, this electric current is the sinusoidal ac signal of 0～15Hz, the general 10Hz that selects, in the situation that the technical conditions license should make this electric current have larger numerical value as far as possible, should be greater than 1A; The outer stratum measurement range of sleeve pipe and higher measuring accuracy that higher electric current correspondence is higher;

Step 3, open down-hole excitation current source S2, to the sleeve pipe Injection Current between electrode E2 and N2, this electric current is direct current, and the direction of switch current periodically, and the general cycle is adopted 10S, and this electric current should adopt large as far as possible numerical value, should be greater than 10A; Larger numerical value is conducive to accurately measure calculating sleeve pipe resistance, accurately eliminates the cover tube resistor to the impact of the outer formation resistivity measurement of sleeve pipe.

The output current A of step 4, measurement S2; Voltage V1 between sleeve pipe top electrode C and D, the voltage V2 between electrode D and E, and the electrode R casing potential VR of place, V1 and V2 all comprise two kinds of frequency components, measure respectively the effective value of the response signal of S1 and S2 excitation generation With

With

Step 5, utilize following formula to calculate the apparent resistivity of formation at target locations

$\mathrm{Ra}=K\·V_{R}A(\frac{\stackrel{\‾}{V}1}{\stackrel{\‾}{V}1}-\frac{\tilde{V}2}{\stackrel{\‾}{V}2})$

In formula, Ra is formation apparent resistivity, and K is the apparent resistivity conversion coefficient of instrument, and A is the output current of excitation current source S2,

For current source S1 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S1 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe;

For current source S2 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S2 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe.

Claims (1)

1. one kind sees through the method that metal sleeve is measured the nonlocal layer resistivity of sleeve pipe, it is characterized in that, comprises the following steps:

The connection of step 1, parts:

S1 is the ground excitation current source, is connected between exciting electrode E1 and N1, is used for by sleeve pipe to the stratum Injection Current, S2 is the down-hole excitation current source, be connected between exciting electrode E2 and N2, for Injection Current on the sleeve pipe between E2 and N2, this electric current is measured by reometer A; C, D, E are potential electrode, and the voltage drop when flowing through sleeve pipe for the measurement electric current on sleeve pipe is measured by voltage table V1 between C, D, is measured by V2 between D, E; R and G are a pair of casing potential potential electrode, and G is Zero potential reference, and on sleeve pipe, R point current potential is measured by voltage table VR; E1 is positioned at the wellhead casing pipe wall, and if the embedding and underground wet soil layer of N1 and G when in 200 meters, offset well being arranged near the target well, or is placed in offset well muzzle tube wall with N1; E1, N1 and G are fixed electordes, and motionless in whole during well logging after placing, other potential electrode are traveling electrodes, move with subsurface equipment in during well logging, and guarantee will reliably contact with internal surface of sleeve pipe when measuring;

Step 2, open excitation current source S1, by electrode pair E1 and N1 Injection Current in the stratum, this electric current is the sinusoidal ac signal of 0～15Hz, in the situation that the technical conditions license should make this electric current have larger numerical value as far as possible, and should be greater than 10A;

Step 3, open down-hole excitation current source S2, to the sleeve pipe Injection Current between electrode E2 and N2, this electric current is direct current, and the direction of switch current periodically, and this electric current should adopt large as far as possible numerical value, should be greater than 10A;

The output current A of step 4, measurement S2; Voltage V1 between sleeve pipe top electrode C and D, the voltage V2 between electrode D and E, and the electrode R casing potential VR of place, V1 and V2 all comprise two kinds of frequency components, measure respectively the effective value of the response signal of S1 and S2 excitation generation

With

With

Step 5, utilize following formula to calculate the apparent resistivity of formation at target locations

$\mathrm{Ra}=K\·V_{R}A(\frac{\stackrel{\‾}{V}1}{\stackrel{\‾}{V}1}-\frac{\tilde{V}2}{\stackrel{\‾}{V}2})$

In formula, Ra is formation apparent resistivity, and K is the apparent resistivity conversion coefficient of instrument, and A is the output current of excitation current source S2,

For current source S1 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S1 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe; For current source S2 output current in the pressure drop that produces between potential electrode C, D on sleeve pipe,

For current source S2 output current in the pressure drop that produces between potential electrode D, E on sleeve pipe.

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