CN106646642B - A kind of scan-type radioactivity caliper logging device and method - Google Patents
A kind of scan-type radioactivity caliper logging device and method Download PDFInfo
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- CN106646642B CN106646642B CN201611243076.2A CN201611243076A CN106646642B CN 106646642 B CN106646642 B CN 106646642B CN 201611243076 A CN201611243076 A CN 201611243076A CN 106646642 B CN106646642 B CN 106646642B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V5/00—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity
- G01V5/04—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
Abstract
The invention discloses a kind of scan-type radioactivity caliper logging method and apparatus, select a gamma radiation source, and multiple collimating apertures, corresponding multiple close, remote gamma detector record scattering Gama Counts are arranged at gamma radiation source；It is mud density and the effect of density of earth formations weighted average as a result, the size contributed detector Gama Count based on mud is related with mud gap according to Gama Count, there are non-linear relations for the two；Each orientation Gama Count along wellbore different depth recorded using gamma detector, and then form the method that quantitative assessment is carried out to hole diameter size.By the way that the combination of multiple groups collimating aperture-detector is arranged, Gama Count statistical error is reduced, the accuracy of orientation hole diameter data is improved；Equipment is measured in underground with rotary scanning mode, has recorded each orientation hole diameter data at the different depth of underground, for hole diameter imaging display.
Description
Technical field
The present invention relates to a kind of logging equipments using core evaporation process measurement hole diameter, and the well based on the measuring device
Diameter measurement method belongs to field geophysics logging technique field.
Background technique
With deepening continuously for oilfield prospecting developing, the accurate description of oil-gas reservoir and reservoir parameter is to formulate oil gas field to open
Originating party case improves the key of recovery ratio and oil and gas production, and geophysical log is to directly determine the main skill of each parameter in stratum
Art, wherein calliper log data are ground stress analysis, real-time drilling monitoring, well completion cement volume estimation, log curve correction, well
Wall washes away the important evidence of evaluation and storage division etc..
Currently, caliper logging method and apparatus mainly has mechanical arm Caliper Log and contactless sound wave hole diameter to survey
Well.When wherein logging well using contact type mechanical measurement multi-arm borehole measuring instrument, generate the measurement arm of all directions according to the variation of hole diameter
Mechanical displacement, hole diameter data pass to ground by cable and are recorded, and realize multi-faceted caliper logging, and the instruments weight is big,
Structure is relative complex.Contactless sound wave caliper logging method mainly passes through measurement sound wave pulse and reaches the borehole wall again by mud
The time parameter of return course, in conjunction with sound wave in mud spread speed, to obtain hole diameter data, therefore contactless sound wave
The measurement accuracy of caliper logging method depends on mud velocity of sound parameter and subsurface environment, such as mud impedance, bubble, temperature, pressure
Deng.
Summary of the invention
Based on above-mentioned technical problem, the present invention provides a kind of scan-type radioactivity caliper logging equipment, and is set based on this
Standby caliper logging method.
The adopted technical solution is that:
A kind of scan-type radioactivity caliper logging equipment, including 1 gamma radiation source, multiple nearly gamma detectors and multiple
The number of remote gamma detector, nearly gamma detector and remote gamma detector is equal, and nearly gamma detector is apart from gamma radiation source
Distance be less than distance of the remote gamma detector apart from gamma radiation source；Multiple gamma collimations are offered at gamma radiation source
The number of hole, the number of the gamma collimating aperture and nearly gamma detector or remote gamma detector is equal, each gamma collimating aperture
Gamma detector close with one and a remote gamma detector match, and the outlet port of the gamma collimating aperture and the nearly gal to match
Horse detector and remote gamma detector are in same perpendicular.
Preferably, the multiple nearly gamma detector is respectively positioned in the same cross section of apparatus subject, nearly gamma detector
Number be set as 2,3 or 4, and when nearly gamma detector is arranged 2, nearly gamma detector be spaced apart from each other for
180 °, when nearly gamma detector is arranged 3, it is 120 ° that adjoining gamma detector, which is spaced apart from each other, when nearly gamma detector is set
When setting 4, it is 90 ° that adjoining gamma detector, which is spaced apart from each other,；The multiple remote gamma detector is also respectively positioned on apparatus subject
In same cross section, the number of corresponding remote gamma detector is set as 2,3 or 4, and when remote gamma detector setting 2
When a, it is 180 ° that remote gamma detector, which is spaced apart from each other, and when remote gamma detector is arranged 3, adjacent remote gamma detector is mutual
Between be divided into 120 °, when remote gamma detector be arranged 4 when, it is 90 ° that adjacent remote gamma detector, which is spaced apart from each other,.
Preferably, the nearly gamma detector or remote gamma detector are respectively placed in the lateral fluting of apparatus subject, and
It is sealed using beryllium, nearly gamma detector and remote gamma detector are all made of NaI crystal.
Preferably, the gamma radiation source is Cs-137 gamma ray source, gamma energy 662KeV, 1~2Ci of source strength；
Gamma radiation source is shielded using high desnity metal.
Preferably, the gamma collimation bore dia is 1.2~2.0cm；The nearly gamma detector length be 1.1~
2.2cm, diameter is 1.5~2.4cm, apart from 15~22cm of gamma radiation source；Remote gamma detector length is 3.3~5.2cm, directly
Diameter is 2.9~3.3cm, apart from 35~45cm of gamma radiation source.
Preferably, the apparatus subject is connected with the power device for driving its axial-rotation.
The method for being scanned formula radioactivity caliper logging using above equipment, comprising the following steps:
A establishes mud gap between scan-type radioactivity caliper logging equipment and the borehole wall and remote gamma detector counts and
The quantitative calculation formula that nearly gamma detector counts:
A1 when between scan-type radioactivity caliper logging equipment and the borehole wall there are when mud gap, according to gamma ray and object
Matter interaction theory and ray attenuation law, consider single remote gamma detector, and remote gamma detector counting is expressed as
In formula (1), μaFor mass attentuation coefficient, ρLFor remote gamma detector apparent density, N is remote gamma detector photon meter
Number, N0For radiation intensity, d is the distance between remote gamma detector and gamma radiation source；
A2 obtains remote gamma detector apparent density calculation formula by formula (1) transformation
A3 is when measuring device is placed in wellbore, since there are mud gap, remote gamma detections between measuring device and the borehole wall
Device photon counting is obtained that apparent density is related with mud density and density of earth formations by mud influence, the remote gamma detector view of acquisition
Density value can be expressed from the next:
ρL=ρb(1-R)+ρmR (3)
In formula (3), ρmFor mud density, ρbFor density of earth formations；Defining R is mud to remote gamma detector apparent density value
Contribution rate:
A4 density of earth formations ρbCalculating is indicated using nearly gamma detector apparent density, remote gamma detector apparent density are as follows:
ρb=ρL+k1(ρL-ρS)+k2(ρL-ρS)2 (5)
In formula, ρLFor remote gamma detector apparent density, ρSFor nearly gamma detector apparent density, k1、k2For with device-dependent
Calibration constant；Formula (5) are substituted into formula (4) to obtain:
A5 establishes calliper log computation model, changes mud gap length, mud density and density of earth formations, utilizes formula (6)
Mud is calculated separately to the contribution rate of remote gamma detector apparent density；
A6 takes the average value of the corresponding apparent density contribution rate R of each mud gap respectively, by mud gap to apparent density tribute
It offers rate R to be fitted with mud gap size variation, obtains mud gap between the contribution rate R and mud of far detector apparent density
The variation relation of gap, is indicated using non-linear formula are as follows:
R=1-e-aS (7)
In formula (7), a is the calibration constant with device-dependent, and S is mud gap size；
Formula (6) are substituted into formula (7) by a7, obtain the mud gap length S for quantitatively determining each orientationiFormula be
B calculates equipment center position to borehole wall distance
The apparent density generation that remote gamma detector in measuring device and nearly gamma detector are calculated b1 in each orientation
Enter in formula (8), each orientation mud gap length is calculated；
B2 equipment center is to borehole wall distance calculation formula
Di=Si+RT (9)
In formula (9), DiFor equipment center position to borehole wall distance, RTFor equipment radius；
According to equipment center position to borehole wall distance value, further calculates and obtain hole diameter numerical value.
In step a5: changing mud gap length is respectively 1cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7cm, 8cm；Mud is close
Degree takes 1.0g/cm respectively3、1.2g/cm3、1.6g/cm3；Density of earth formations takes 1.684g/cm respectively3、1.8208g/cm3、2.026g/
cm3、2.197g/cm3、2.368g/cm3、2.539g/cm3、2.6758g/cm3、2.8558g/cm3The rock for being full of fresh water.
In the above method, measuring device is measured in underground with rotary scanning mode.
In the above method, wellbore periphery equivalent is divided into 16 orientation or 32 orientation and is measured.
The method have the benefit that:
1, the method for the present invention obtains mud to the size of detector Gama Count contribution rate by establishing analysis of calculation models
It is related with mud gap and at non-linear relation, and quantitatively determine based on the above analysis mud gap length computation in each orientation
Formula records each orientation Gama Count at different borehole depths in conjunction with close, remote gamma detector, hole diameter model is calculated
It encloses, there are the advantages such as high, the non-contact, broad applicability of measurement accuracy, fine evaluation can be carried out to wellbore.
2, present device, which uses, opens up multiple collimating apertures, while multiple close, remote gammas corresponding with collimating aperture are arranged
Detector, Gama Count statistics error is smaller, and cooperating equipment is measured in underground with rotary scanning mode, and hole diameter is at image quality
Amount is high, can determine expanding or shrinkage section and erosion borehole position and orientation by hole diameter image, while can quantify
Determine expanding or undergauge and erosion size.
3, hole diameter is determined using far detector Gama Count in the method for the present invention, calculate hole diameter range and accuracy than close
Detector also will correspondingly increase the precision of caliper logging greatly.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of measuring device of the present invention.In figure: 1 is apparatus subject, and 2 be gamma collimating aperture, and 4 be remote
Gamma detector seals substance, and 5 be remote gamma detector, and 6 be gamma radiation source, and 7 be nearly gamma detector, and 8 be wellbore, and 9 are
Stratum, 10 be power device, and 11 be the first shield, and 12 seal substance for nearly gamma detector, and 13 be secondary shielding body, and 14 are
Ground control system；
Fig. 2 be in Fig. 1 equipment A to cutaway enlargement diagram at nearly gamma radiation source；
Fig. 3 is that equipment B is to cutaway enlargement diagram at remote gamma detector in Fig. 1, and 3 is outside gamma detector crystal in figure
Shell.Equally, setting is similar to remote gamma detector at nearly gamma detector, and only detector size is different；
Fig. 4 is instrument with rotary scanning measurement method and data acquisition unit schematic diagram, by taking 16 azimuthal measuremenies as an example；
Fig. 5 is the Monte Carlo numerical computation model established using Fig. 1, by changing design conditions, obtained mud pair
Remote gamma detector apparent density contribution rate changing rule figure.Design conditions are as follows: the gap changed between instrument and the borehole wall is respectively
1cm,2cm,3cm,4cm,5cm,6cm,7cm,8cm；Mud density takes 1.0g/cm respectively3、1.2g/cm3、1.6g/cm3；Stratum
Density takes 1.684g/cm respectively3、1.8208g/cm3、2.026g/cm3、2.197g/cm3、2.368g/cm3、2.539g/cm3、
2.6758g/cm3、2.8558g/cm3The limestone for being full of fresh water, R indicate mud to remote gamma detector apparent density contribution rate.
Fig. 6 is to take the corresponding R average value of each mud gap in Fig. 5 respectively, obtains the pass between R and mud gap
System；
Fig. 7 is the comparison that non-linear fitting method and linear fit method calculate error；
Fig. 8 depicts that hole diameter is expanding and erosion model, and in figure: 15 be borehole washout well section, and 16 be the expanding well section of wellbore；
Fig. 9 be in Fig. 8 C to borehole washout cross-sectional view；
Figure 10 be in Fig. 8 D to the expanding cross-sectional view of wellbore；
Figure 11 is to calculate single orientation using the method for the present invention by establishing different degrees of hole shrinkage and expanding model
The variation of well curve；
Figure 12 is the expanding model of wellbore shown in Fig. 8 established, and is construed to using the orientation hole diameter that the method for the present invention obtains
Fruit two-dimensional surface spread schematic diagram；
Figure 13 is the borehole washout model shown in Fig. 8 established, and is construed to using the orientation hole diameter that the method for the present invention obtains
Fruit two-dimensional surface spread schematic diagram.
Figure 14 is the three-dimensional wellbore shape image drawn using the present invention.
Specific embodiment
The invention discloses a kind of scan-type radioactivity caliper logging method and apparatus, select a gamma radiation source,
Multiple collimating apertures, corresponding multiple close, remote gamma detector record scattering Gama Counts are set at gamma radiation source；According to gal
It is mud density and the effect of density of earth formations weighted average as a result, being contributed based on mud detector Gama Count big that horse, which counts,
Small related with mud gap, there are non-linear relations for the two；Utilize each along wellbore different depth of gamma detector record
Orientation Gama Count, and then form the method that quantitative assessment is carried out to hole diameter size.By the way that multiple groups collimating aperture-detector is arranged
Combination, reduces Gama Count statistical error, improves the accuracy of orientation hole diameter data；Equipment is in underground with rotary scanning side
Formula measures, and has recorded each orientation hole diameter data at the different depth of underground, for hole diameter imaging display.
It elaborates with reference to the accompanying drawing to the present invention.
As shown in Figure 1, a kind of scan-type radioactivity caliper logging equipment, including 1 gamma radiation source 6, multiple nearly gammas
The number of detector 7 and multiple remote gamma detectors 5, nearly gamma detector 7 and remote gamma detector 5 is equal, nearly gamma detection
Distance of the device 7 apart from gamma radiation source 6 is less than distance of the remote gamma detector 5 apart from gamma radiation source 6.In gamma radiation source 6
Place offers multiple gamma collimating apertures 2, the number and nearly gamma detector 7 of the gamma collimating aperture 2 or far gamma detector 5
Number is equal.Each gamma collimating aperture 2 gamma detector 7 close with one and a remote gamma detector 5 match, and the gamma collimates
The outlet port in hole 2 is in same perpendicular with the nearly gamma detector 7 and remote gamma detector 5 to match.
Above-mentioned multiple nearly gamma detectors 7 are respectively positioned in the same cross section of apparatus subject 1, of nearly gamma detector 7
Number is set as 2,3 or 4, and when nearly gamma detector 7 is arranged 2, it is 180 ° that nearly gamma detector, which is spaced apart from each other, when
When nearly gamma detector is arranged 3, it is 120 ° that adjoining gamma detector, which is spaced apart from each other, when nearly gamma detector is arranged 4,
It is 90 ° that adjoining gamma detector, which is spaced apart from each other,.The multiple remote gamma detector 5 is also respectively positioned on the same cross of apparatus subject 1
In section, the number of corresponding remote gamma detector is set as 2,3 or 4, and when remote gamma detector is arranged 2,
It is 180 ° that remote gamma detector, which is spaced apart from each other, when remote gamma detector is arranged 3, adjacent remote gamma detector be spaced apart from each other for
120 °, when remote gamma detector is arranged 4, it is 90 ° that adjacent remote gamma detector, which is spaced apart from each other,.It is preferred that nearly gamma detector 7
4 are respectively provided with remote gamma detector 5.
Above-mentioned nearly gamma detector 7 or remote gamma detector 5 are respectively placed in the lateral fluting of apparatus subject 1, and respectively
Substance 12 is sealed using nearly gamma detector and remote gamma detector sealing substance 4 seals, sealer is of fine quality to select beryllium.Nearly gamma is visited
It surveys device 7 and remote gamma detector 5 is all made of NaI crystal.
Above-mentioned gamma radiation source 6 is Cs-137 gamma ray source, gamma energy 662KeV, 1~2Ci of source strength.Gamma is put
It penetrates source to shield using high desnity metal, preferably tungsten nickel iron alloy.
Above-mentioned 2 diameter of gamma collimating aperture is 1.2~2.0cm.Above-mentioned 7 length of nearly gamma detector is 1.1~2.2cm, directly
Diameter is 1.5~2.4cm, apart from 15~22cm of gamma radiation source；Remote 5 length of gamma detector is 3.3~5.2cm, diameter 2.9
~3.3cm, apart from 35~45cm of gamma radiation source.
Above-mentioned apparatus subject 1 is connected with the power device 10 for driving its axial-rotation, and power device 10 and ground control are
14 connection of system.
Secondary shielding body 13, nearly 7 He of gamma detector are provided between above-mentioned nearly gamma detector 7 and gamma radiation source 6
The first shield 11 is provided between remote gamma detector 5.
The method for being scanned formula radioactivity caliper logging using above equipment, comprising the following steps:
When between scan-type radioactivity caliper logging equipment and the borehole wall there are when mud gap, according to gamma ray and substance
Interaction theory and ray attenuation law, consider single remote gamma detector, and explorer count is expressed as
In formula (1), μaFor mass attentuation coefficient；ρLFor remote gamma detector apparent density；N, N0Respectively remote gamma detector
Photon counting and radiation intensity；D is the distance between remote gamma detector and gamma radiation source.
Stratum apparent density, which can be calculated, by formula (1) is
Because of gamma ray and when material effect, the decaying of gamma ray and material density are exponential relationship, therefore according to setting
Standby gamma detector counts the scale relationship between material density, available density of earth formations.When equipment be placed in it is shown in FIG. 1
When measuring environment, since, there are mud gap, detector measurement is counted by mud influence between equipment and the borehole wall, apparent density is obtained
It is the weighted average of mud density and density of earth formations, the detector apparent density value of acquisition can be expressed from the next:
ρL=ρb(1-R)+ρmR (3)
In formula, ρm, ρbRespectively mud, density of earth formations.Definition R is contribution of the mud to remote gamma detector apparent density value:
Density of earth formations ρbCalculating can use close, remote gamma detector and calculate apparent density expression are as follows:
ρb=ρL+k1(ρL-ρS)+k2(ρL-ρS)2 (5)
In formula, ρL、ρSRespectively remote, close gamma detector apparent density, k1、k2For calibration constant related with instrument.By formula
(5) formula (4) are substituted into:
Clearly for one timing of mud and density of earth formations, mud gap is bigger, and mud contributes detector apparent density value will
Become larger；The computation model under the conditions of calliper log shown in Fig. 1 is established using Monte Carlo numerical method, computation of mud is to remote gamma
The changing rule of detector apparent density contribution R.Change mud gap length be respectively 1cm, 2cm, 3cm, 4cm, 5cm, 6cm,
7cm,8cm；Mud density takes 1.0g/cm respectively3、1.2g/cm3、1.6g/cm3；Density of earth formations takes 1.684g/cm respectively3、
1.8208g/cm3、2.026g/cm3、2.197g/cm3、2.368g/cm3、2.539g/cm3、2.6758g/cm3、2.8558g/cm3
The rock for being full of fresh water.Mud is calculated separately to the size of the contribution rate R of remote gamma detector apparent density, knot using formula (6)
Fruit is as shown in Figure 5.
Fig. 5 is shown, under the conditions of identical mud gap, mud is to far detector apparent density value contribution rate size with density of earth formations
It is basically unchanged with mud density, therefore in common density of earth formations and mud density, when one timing of mud gap, mud pair
The contribution rate R of apparent density can be considered a constant substantially.
The average value for taking the corresponding apparent density contribution rate R of each mud gap in Fig. 5 respectively, mud gap is close to regarding
Degree contribution rate R is fitted with mud gap size variation, obtains mud between the contribution rate R and mud of far detector apparent density
The variation relation of gap is as shown in fig. 6, can use non-linear formula expression are as follows:
R=1-e-aS (7)
In formula (7), a is calibration constant related with instrument, and S is mud gap size.Different mud as seen from Figure 6
Under gap condition, mud contribution rate R increases with mud gap and is increased；When mud gap increases to a certain extent, the variation of R value
Gradually slow down, there are certain non-linear relations.Compared to the simple relationship for describing contribution rate R and interval S using linear relationship, i.e.,
Empirical coefficient method, it is above-mentioned to describe both sides relation using formula (7) using the mode of fixed linear graduation coefficient (empirical parameter)
It is more accurate, it is remarkably improved the computational accuracy of hole diameter.Especially when encountering situations such as mud density is excessive, hole diameter seriously expands
When, it can still guarantee preferable computational accuracy.
Fig. 7 shows the comparison of the above method Yu empirical coefficient method computational accuracy, it can be seen from the figure that with mud gap
Increase, the calculating error of empirical coefficient method is increasing；Then, when mud gap increases above 3cm or so, experience system
The calculating error of number method is gradually reduced.From Fig. 7 it is obvious it can be concluded that, the calculating error of this method is smaller, and calculates error base
This is not influenced by mud gap size.
Based on the above analysis, the contribution rate R of mud and the variation relation of mud gap can use, calculate any in wellbore
Equipment and borehole wall gap size at position, and then fine evaluation is carried out to borehole status using hole diameter imaging method.By formula (6) generation
Enter formula (7), obtains the mud gap length S for quantitatively determining each orientationiFormula be
In formula (8), i=1,2 ... 16；It measures orientation with C1 shown in Fig. 4, C2 ... C16 and corresponds.
By taking the calliper log in 16 orientation as an example, each orientation mud gap length is determined using the above method, in instrument
The heart is to borehole wall distance calculation formula
Di=Si+RT (9)
In formula (9), DiFor centre position to borehole wall distance, i=1,2 ... 16, RTFor instrument radius.
Formula (8), formula (9) are as can be seen that scan-type radioactivity caliper logging method and apparatus of the present invention, using multi-faceted
Far, closely gamma detector apparent density ρLAnd ρSAnd wellbore mud density ρm, form a kind of pair of underground borehole status and finely comment
The method of valence.
Further, establish that wellbore as shown in Figure 8 is expanding and erosion model using Monte-Carlo Numerical Simulation method,
Stratum is to be full of fresh water limestone formation, mud is full of in wellbore, instrument is placed in the middle and measures 16 orientation are divided well week.Work as well
When expanding or undergauge in various degree occurs for eye, the well curve in corresponding orientation is calculated using the above method, reacts the well in the orientation
Diameter is expanding or the size of undergauge degree D is as shown in figure 11.It can be very it can be seen that wellbore curve is calculated using the above method
Reflect stratum wellbore change in size well.
Hole diameter shape is imaged using linear interpolation method using obtained a plurality of well curve.Figure 12 is wellbore
When expanding, the hole diameter imaging transverse expanded view that is calculated, it can be seen that at 50-160cm, wellbore has occurred expanding.
When erosion occurs for a certain orientation of wellbore, each orientation well curve is calculated using identical method, and carry out
Hole diameter imaging is plane outspread drawing as shown in figure 13, it can be seen that at the 4th orientation, borehole washout has occurred.
Three-dimensional wellbore shape imaging can also be carried out as shown in figure 14 to entire measurement well section simultaneously, three-dimensional imaging figure can
Reflect the wellbore shape variation of entire well section very well.
In conclusion the present invention is using mud to the non-linear of the contribution rate R of gamma detector apparent density and mud gap
Multiple close, remote gamma detectors corresponding with collimating aperture are arranged by opening up multiple collimating apertures in relationship, with scanning mode into
Row measurement can carry out fine evaluation to wellbore, improve borehole status and describe precision, widened adaptation range.
Claims (4)
1. a kind of scan-type radioactivity caliper logging method, using scan-type radioactivity caliper logging equipment, which includes 1
Of gamma radiation source, multiple nearly gamma detectors and multiple remote gamma detectors, nearly gamma detector and remote gamma detector
Number is equal, and distance of the nearly gamma detector apart from gamma radiation source is less than distance of the remote gamma detector apart from gamma radiation source；
Multiple gamma collimating apertures, the number of the gamma collimating aperture and nearly gamma detector or remote gamma are offered at gamma radiation source
The number of detector is equal, and each gamma collimating aperture gamma detector close with one and a remote gamma detector match, and the gal
The outlet port of horse collimating aperture is in same perpendicular with the nearly gamma detector and remote gamma detector to match；Its feature
Be the measurement method the following steps are included:
A establishes the mud gap between scan-type radioactivity caliper logging equipment and the borehole wall and remote gamma detector counts and nearly gal
The quantitative calculation formula of horse explorer count:
A1 when between scan-type radioactivity caliper logging equipment and the borehole wall there are when mud gap, according to gamma ray and substance phase
Interaction Theory and ray attenuation law, consider single remote gamma detector, and remote gamma detector counting is expressed as
In formula (1), μaFor mass attentuation coefficient, ρLFor remote gamma detector apparent density, N is remote gamma detector photon counting, N0
For radiation intensity, d is the distance between remote gamma detector and gamma radiation source；
A2 obtains remote gamma detector apparent density calculation formula by formula (1) transformation
A3 is when measuring device is placed in wellbore, since there are mud gap, remote gamma detector light between measuring device and the borehole wall
Sub-count is obtained that apparent density is related with mud density and density of earth formations by mud influence, the remote gamma detector apparent density of acquisition
Value can be expressed from the next:
ρL=ρb(1-R)+ρmR (3)
In formula (3), ρmFor mud density, ρbFor density of earth formations；Definition R is contribution of the mud to remote gamma detector apparent density value
Rate:
A4 density of earth formations ρbCalculating is indicated using nearly gamma detector apparent density, remote gamma detector apparent density are as follows:
ρb=ρL+k1(ρL-ρS)+k2(ρL-ρS)2 (5)
In formula, ρLFor remote gamma detector apparent density, ρSFor nearly gamma detector apparent density, k1、k2For the scale with device-dependent
Constant；Formula (5) are substituted into formula (4) to obtain:
A5 establishes calliper log computation model, changes mud gap length, mud density and density of earth formations, respectively using formula (6)
Contribution rate of the computation of mud to remote gamma detector apparent density；
A6 takes the average value of the corresponding apparent density contribution rate R of each mud gap respectively, by mud gap to apparent density contribution rate R
It is fitted with mud gap size variation, obtains mud gap to the contribution rate R of far detector apparent density and mud gap
Variation relation is indicated using non-linear formula are as follows:
R=1-e-aS (7)
In formula (7), a is the calibration constant with device-dependent, and S is mud gap size；
Formula (6) are substituted into formula (7) by a7, obtain the mud gap length S for quantitatively determining each orientationiFormula be
B calculates equipment center position to borehole wall distance
Remote gamma detector in measuring device and nearly gamma detector are substituted into formula (8) in the apparent density that each orientation calculates by b1
In, each orientation mud gap length is calculated；
B2 equipment center is to borehole wall distance calculation formula
Di=Si+RT (9)
In formula (9), DiFor equipment center position to borehole wall distance, RTFor equipment radius；
According to equipment center position to borehole wall distance value, further calculates and obtain hole diameter numerical value.
2. a kind of scan-type radioactivity caliper logging method according to claim 1, which is characterized in that in step a5: changing
Becoming mud gap length is respectively 1cm, 2cm, 3cm, 4cm, 5cm, 6cm, 7cm, 8cm；Mud density takes 1.0g/cm respectively3、
1.2g/cm3、1.6g/cm3；Density of earth formations takes 1.684g/cm respectively3、1.8208g/cm3、2.026g/cm3、2.197g/cm3、
2.368g/cm3、2.539g/cm3、2.6758g/cm3、2.8558g/cm3The rock for being full of fresh water.
3. a kind of scan-type radioactivity caliper logging method according to claim 1, it is characterised in that: measuring device is in well
Under measured with rotary scanning mode.
4. a kind of scan-type radioactivity caliper logging method according to claim 1, it is characterised in that: by wellbore periphery etc.
Amount is divided into 16 orientation or 32 orientation and measures.
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| CN108509675B (en) * | 2018-02-08 | 2021-10-26 | 中国石油大学(华东) | Method for calculating hole diameter and clearance by density logging while drilling |
| CN108716397B (en) * | 2018-04-03 | 2020-10-30 | 中国石油大学(北京) | Method and device for calculating logging azimuth resolution by gamma imaging while drilling |
| CN108986625B (en) * | 2018-08-23 | 2023-05-16 | 东华理工大学 | Novel small natural gamma logging simulation device and method |
| CN109444972B (en) * | 2018-09-19 | 2020-07-03 | 中国石油大学(华东) | Logging device and method for measuring formation density by dual-energy X-ray |
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| US6552334B2 (en) * | 2001-05-02 | 2003-04-22 | Schlumberger Technology Corporation | Wellbore caliper measurement method using measurements from a gamma-gamma density |
| CN201170095Y (en) * | 2007-11-08 | 2008-12-24 | 中国石化集团胜利石油管理局钻井工艺研究院 | Wing rib telescopic density logger following with drilling |
| CN102518431B (en) * | 2011-12-26 | 2015-04-22 | 中国石油大学(华东) | Multi-parameter logging method while drilling based on controllable neutron source |
| CN102707325B (en) * | 2012-05-28 | 2014-10-15 | 中国石油大学(华东) | Azimuth gamma measuring method and equipment |
| CN203050679U (en) * | 2013-01-20 | 2013-07-10 | 邱世军 | Directivity gamma measuring system |
| CN103352689B (en) * | 2013-07-03 | 2015-10-21 | 中国石油大学(华东) | A kind of method utilizing radioactive tracer logging technology determination hole diameter |
| CN205638450U (en) * | 2016-04-29 | 2016-10-12 | 中国石油天然气股份有限公司 | Logging instrument |
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