CN111335886A - Neutron gamma density logging measurement device and method - Google Patents
Neutron gamma density logging measurement device and method Download PDFInfo
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- CN111335886A CN111335886A CN202010081298.9A CN202010081298A CN111335886A CN 111335886 A CN111335886 A CN 111335886A CN 202010081298 A CN202010081298 A CN 202010081298A CN 111335886 A CN111335886 A CN 111335886A
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- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005259 measurement Methods 0.000 title claims description 20
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 74
- 229910052796 boron Inorganic materials 0.000 claims abstract description 74
- 238000001514 detection method Methods 0.000 claims abstract description 43
- 229910052580 B4C Inorganic materials 0.000 claims abstract description 25
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229920001971 elastomer Polymers 0.000 claims abstract description 25
- 238000001739 density measurement Methods 0.000 claims abstract description 14
- 238000005553 drilling Methods 0.000 claims abstract description 13
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 12
- 238000001228 spectrum Methods 0.000 claims description 27
- 239000013078 crystal Substances 0.000 claims description 24
- 229910000838 Al alloy Inorganic materials 0.000 claims description 13
- 238000000691 measurement method Methods 0.000 claims description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 241001637516 Polygonia c-album Species 0.000 claims 2
- 229910001026 inconel Inorganic materials 0.000 claims 1
- 238000012937 correction Methods 0.000 abstract description 15
- 230000033558 biomineral tissue development Effects 0.000 abstract description 7
- 238000013461 design Methods 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 230000005251 gamma ray Effects 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- OWUGOENUEKACGV-UHFFFAOYSA-N [Fe].[Ni].[W] Chemical compound [Fe].[Ni].[W] OWUGOENUEKACGV-UHFFFAOYSA-N 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000008398 formation water Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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Abstract
The invention discloses a neutron gamma density logging measuring device and a method, wherein the neutron gamma density logging measuring device comprises a shell, a main shield, an auxiliary shield, a controllable neutron source, a near detection assembly and a far detection assembly, wherein the near detection assembly comprises a near gamma detector and a first boron carbide rubber sleeve; the far detection assembly comprises a far gamma detector and a second boron carbide rubber sleeve. The neutron gamma density logging method comprises the steps of density logging coefficient calibration and formation density measurement while drilling logging. The technical scheme provided by the invention has the beneficial effects that: the gamma detector is modified by adopting the design of wrapping the boron sleeve, the boron sleeve can absorb thermal neutrons and emit boron capture gamma rays, the boron capture gamma information is detected by the gamma detector, and then the boron capture gamma is used for replacing the total capture gamma to carry out HI correction, so that the neutron gamma density logging method based on the boron capture gamma correction is obtained, and the influence of the mineralization degree on the density measurement result is greatly reduced.
Description
Technical Field
The invention relates to the technical field of well logging, in particular to a neutron gamma density well logging measuring device and method.
Background
Neutron Gamma Density (NGD) logging adopts a controllable source to replace a chemical source Cs-137 for density measurement, is safe and environment-friendly, and has important significance for development of logging while drilling technology and oil and gas exploration and development. Existing NGD logs use inelastic scattering gamma-ray count ratios for density measurements and require fast neutron, thermal neutron, or capture gamma information for Hydrogen Index (HI) correction. The NGD method based on capture gamma correction adopts a measurement system consisting of double gamma detectors, does not need additional neutrons or gamma detectors, and has important significance for the optimized design and cost control of the NGD instrument.
Currently, the capture gamma correction-based NGD method generally adopts total capture gamma energy spectrum information to perform HI correction; because the capture gamma energy spectrum recorded in the logging is greatly influenced by the water mineralization of the stratum, the NGD density logging result has larger error in the saline stratum, and the application and popularization of the NGD density logging result in the complex stratum are seriously limited.
Disclosure of Invention
Accordingly, there is a need for a neutron-gamma density device and a corresponding measurement method for reducing errors in neutron-gamma density log results in a saline formation.
The invention provides a neutron gamma density logging measuring device, comprising: a shell, a main shield, an auxiliary shield, a controllable neutron source, a near detection component and a far detection component,
the housing has an equipment cavity;
the main shielding body is arranged in the equipment cavity and divides the equipment cavity into a transmitting cavity and a receiving cavity;
the secondary shielding body is arranged in the receiving cavity and divides the receiving cavity into a near receiving cavity and a far receiving cavity;
the controllable neutron source is arranged in the emission cavity and is used for emitting neutrons;
the near detection assembly is arranged in the near receiving cavity and comprises a near gamma detector and a first boron carbide rubber sleeve, and the first boron carbide rubber sleeve is sleeved on the near gamma detector;
the far detection assembly is arranged in the far receiving cavity and comprises a far gamma detector and a second boron carbide rubber sleeve, and the second boron carbide rubber sleeve is sleeved on the far gamma detector.
The invention also provides a neutron gamma density logging measurement method, which comprises a density logging coefficient calibration method and a logging while drilling stratum density measurement method, wherein,
the density logging coefficient calibration method comprises the following steps:
s11, installing the neutron-gamma density logging measurement device as claimed in any one of claims 1-7 on a drill collar and descending the drill collar into a graduated well with known density;
s12, periodically emitting neutrons through the controllable neutron source, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector and the far gamma detector;
s13, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, determining an energy window corresponding to the boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, making a ratio on the inelastic scattering gamma counts corresponding to the near gamma detector and the far gamma detector, acquiring a first inelastic scattering gamma count ratio, and making a ratio on the boron capture gamma counts corresponding to the near gamma detector and the far gamma detector, and acquiring a first boron capture gamma count ratio;
s14, changing the hydrogen index of the graduated well, and repeating the steps S11-S13;
s15, replacing the scale wells with different densities, and repeating the steps S11-S14;
s16, substituting each first inelastic scattering gamma count ratio, each first boron capture gamma count ratio and the density of each graduated well into a density formula to determine the value of each coefficient in the density formula;
the logging while drilling formation density measurement method comprises the following steps:
s21, mounting the neutron gamma density logging measurement device as set forth in any one of claims 1-7 on a drill collar;
s22, keeping the shell attached to the well wall in the drilling process, periodically emitting neutrons through the controllable neutron source, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector and the far gamma detector;
s23, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, determining an energy window corresponding to the boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, making a ratio on the inelastic scattering gamma counts corresponding to the near gamma detector and the far gamma detector, acquiring a second inelastic scattering gamma count ratio, and making a ratio on the boron capture gamma counts corresponding to the near gamma detector and the far gamma detector, and acquiring a second boron capture gamma count ratio;
and S24, substituting the second inelastic scattering gamma count ratio and the second boron capture gamma count ratio into the density formula to determine the density of the stratum.
Compared with the prior art, the technical scheme provided by the invention has the beneficial effects that: the gamma detector is modified by adopting the design of wrapping a boron sleeve, the boron sleeve can absorb thermal neutrons and emit boron capture gamma rays, the boron capture gamma information is detected by the gamma detector, and then the boron capture gamma is used for replacing the total capture gamma to carry out HI correction, so that the neutron gamma density logging method based on the boron capture gamma correction is obtained, and the influence of the mineralization on the density measurement result is greatly reduced; in addition, the boron capture gamma information has little influence on the total capture gamma energy spectrum, can work simultaneously with the neutron gamma density method based on the total capture gamma, and has important significance on the popularization and application of neutron gamma density logging.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of a neutron-gamma density logging measurement device provided by the present invention;
FIG. 2 is a schematic structural view of the proximity detection assembly of FIG. 1;
FIG. 3 is a schematic view of a neutron gamma density logging measurement device measurement under while drilling conditions;
FIG. 4 is a schematic flow chart of a density logging coefficient calibration method of the neutron-gamma density logging measurement method provided by the invention;
FIG. 5 is a schematic flow chart of formation density measurement while drilling of a neutron gamma density logging measurement method provided by the invention;
FIG. 6 is a capture gamma energy spectrum recorded by the neutron gamma density logging measurement device of FIG. 1;
in the figure: the device comprises a shell 1, a main shield 2, a secondary shield 3, a controllable neutron source 4, a near detection component 5, a far detection component 6, a drill collar 7, a graduated well 8, a near gamma detector 51, a first aluminum alloy shell 511, a first NaI detection crystal 512, a first photomultiplier 513, a first boron carbide rubber sleeve 52, a far gamma detector 61, a second aluminum alloy shell 611, a second NaI detection crystal 612, a second photomultiplier 613, and a second boron carbide rubber sleeve 62.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, the present invention provides a neutron-gamma density logging measurement device, which includes a housing 1, a main shield 2, a secondary shield 3, a controllable neutron source 4, a near detection assembly 5, and a far detection assembly 6.
Referring to fig. 1, the housing 1 has an equipment chamber. The main shielding body 2 is arranged in the equipment cavity and divides the equipment cavity into a transmitting cavity and a receiving cavity. The auxiliary shielding body 3 is arranged in the receiving cavity and divides the receiving cavity into a near receiving cavity and a far receiving cavity; the controllable neutron source 4 is arranged in the emission cavity and is used for emitting neutrons.
Referring to fig. 1 and 2, the near detection assembly 5 is disposed in the near receiving cavity, the near detection assembly 5 includes a near gamma detector 51 and a first boron carbide rubber sleeve 52, and the first boron carbide rubber sleeve 52 is sleeved on the near gamma detector 51. The far detection assembly 6 is arranged in the far receiving cavity, the far detection assembly 6 comprises a far gamma detector 61 and a second boron carbide rubber sleeve 62, and the second boron carbide rubber sleeve 62 is sleeved on the far gamma detector 61.
It should be noted that the first boron carbide rubber sleeve 52 and the second boron carbide rubber sleeve 62 can absorb thermal neutrons and emit boron capture gamma rays, so that the detector can receive the boron capture gamma rays, and therefore, the device does not affect the distribution of neutrons and gamma fluxes in the formation, and only absorbs and converts the thermal neutrons reaching the detector into boron capture gamma information for recording.
Preferably, referring to fig. 1, the controllable neutron source 4 is a D-T neutron source, the pulse width of the controllable neutron source 4 is 20 μ s, the duty cycle of the controllable neutron source 4 is 400 μ s, the number of neutrons emitted by the controllable neutron source 4 per second is 1 × 108n, and the neutron energy of the controllable neutron source 4 is 14.2 MeV.
Preferably, referring to fig. 1, the thicknesses of the first boron carbide rubber sleeve 52 and the second boron carbide rubber sleeve 62 are both 5 mm.
Preferably, referring to fig. 1, the main shield 2 and the auxiliary shield 3 are made of tungsten nickel iron, and the thicknesses of the main shield 2 and the auxiliary shield 3 are both 5 cm.
Specifically, referring to fig. 1 and fig. 2, the near gamma detector 51 includes a first aluminum alloy casing 511, a first NaI detection crystal 512, and a first photomultiplier 513, wherein the first aluminum alloy casing 511 has a first closed accommodating cavity; the first NaI probe crystal 512 is disposed in the first accommodating cavity; the first photomultiplier 513 is disposed in the first accommodating cavity and connected to the first NaI detection crystal 512; the first boron carbide rubber sleeve 52 is sleeved on the first aluminum alloy shell 511. The far gamma detector 61 comprises a second aluminum alloy shell 611, a second NaI detection crystal 612 and a second photomultiplier 613, wherein the second aluminum alloy shell 611 has a closed second accommodating cavity; the second NaI probe crystal 612 is disposed in the second receiving cavity; the second photomultiplier tube 613 is disposed in the second accommodating cavity and connected to the second NaI detection crystal 612; the second boron carbide rubber sleeve 62 is sleeved on the second aluminum alloy shell 611.
Preferably, referring to fig. 1 and 2, the distance between the first NaI detection crystal 512 and the controllable neutron source 4 is 30-40cm, and the distance between the second NaI detection crystal 612 and the controllable neutron source 4 is 60-70 cm. In this embodiment, the distance between the first NaI detection crystal 512 and the controllable neutron source 4 is 35cm, and the distance between the second NaI detection crystal 612 and the controllable neutron source 4 is 65 cm.
Preferably, referring to fig. 1 and 2, the first NaI detection crystal 512 has a length of 8cm, and the second NaI detection crystal 612 has a length of 14 cm.
The invention also provides a neutron gamma density logging measurement method, which comprises a density logging coefficient calibration method and a logging while drilling stratum density measurement method, wherein,
referring to fig. 3 and 4, the method for calibrating a density logging coefficient includes:
s11, mounting the neutron gamma density logging measuring device on a drill collar 7 and descending the device into a calibration well 8 with known density along with the drill collar 7, wherein the stratum simulated by the calibration well 8 is a limestone stratum in the embodiment;
s12, periodically emitting neutrons through the controllable neutron source 4, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector 51 and the far gamma detector 61;
s13, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector 51, obtaining an inelastic scattering gamma count and a boron capture gamma count, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector 61, obtaining an inelastic scattering gamma count and a boron capture gamma count, making a ratio between the inelastic scattering gamma counts corresponding to the near gamma detector 51 and the far gamma detector 61, obtaining a first inelastic scattering gamma count ratio, and making a ratio between the boron capture gamma counts corresponding to the near gamma detector 51 and the far gamma detector 61, obtaining a first boron capture gamma count ratio;
s14, changing the hydrogen index of the graduated well 8, and repeating the steps S11-S13;
s15, replacing the scale wells 8 with different densities, and repeating the steps S11-S14;
s16, substituting the first inelastic scattering gamma count ratios, the first boron capture gamma count ratios and the density of the calibration wells into a density formula, and performing a density algorithm calibration by using a multivariate nonlinear fitting method to determine the value of each coefficient in the density formula, wherein the density formula is as follows:
ρ＝Aln(Rin-BRc)+C
where ρ is the formation density, RinIs an inelastic scattering gamma ratio, RcA, B, C are coefficients, which are the boron capture gamma count ratio;
referring to fig. 5, the method for measuring formation density while drilling includes:
s21, mounting the neutron gamma density logging measuring device on a drill collar 7;
s22, keeping the shell 1 attached to the well wall in the drilling process, periodically emitting neutrons through the controllable neutron source 4, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector 51 and the far gamma detector 61;
s23, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector 51, obtaining an inelastic scattering gamma count and a boron capture gamma count, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector 61, obtaining an inelastic scattering gamma count and a boron capture gamma count, making a ratio between the inelastic scattering gamma counts corresponding to the near gamma detector 51 and the far gamma detector 61, obtaining a second inelastic scattering gamma count ratio, making a ratio between the boron capture gamma counts corresponding to the near gamma detector 51 and the far gamma detector 61, and obtaining a second boron capture gamma count ratio; in this embodiment, referring to fig. 6, the energy peak of the boron capture gamma is about 0.5MeV, and the energy window is set to 0.45-0.55MeV, so that the energy of the boron capture gamma ray is low and concentrated, and the influence on the total capture gamma spectrum information is small, and the total capture gamma spectrum which is not interfered by the boron gamma ray can be obtained by deducting the corresponding energy window count of the boron capture gamma ray information, so that the method can work simultaneously with the neutron gamma density method based on the total capture gamma correction;
and S24, substituting the second inelastic scattering gamma count ratio and the corresponding second boron capture gamma count ratio into the density formula to determine the density of the stratum.
Preferably, the time windows of the near gamma detector 51 and the far gamma detector 61 for recording inelastic scattering gamma are both 0-20 μ s, and the time windows for recording capture gamma are both 30-400 μ s, wherein the inelastic scattering gamma and the capture gamma are both recorded in 255 channels, and the energy recording range of each gamma detector is 0.01-8.5 MeV.
In order to test the effect of the neutron gamma density logging measuring device and the neutron gamma density logging measuring method, the calibration wells under the conditions of different porosities and mineralization degrees are actually tested. Referring to table 1, density logging experiments were performed on 15 graduated wells having a porosity of 1p.u., 10p.u., 20p.u., 30p.u., and 40p.u., respectively, and a mineralization (Cw) of 0kppm, 100kppm, and 200kppm, respectively, for which the reference density is known, HI correction was performed through total capture gamma energy spectrum information and boron capture gamma energy spectrum information, density obtained through the two methods was calculated, and finally, the density error between the density calculated by the two methods and the reference density was calculated, and the test results are shown in table 1.
TABLE 1 Effect of application under different porosity and mineralization conditions
As can be seen from Table 1, under the condition that the salinity of the formation water is high, the neutron gamma density measurement method based on boron capture gamma correction can obtain more accurate formation density, and the influence of the salinity on the density measurement result is greatly reduced. For example, a 30p.u. water-saturated formation (Cw 200kppm), the neutron-gamma density log error based on boron capture gamma correction is 0.0374g/cm3While the neutron-gamma density logging error based on total capture gamma correction is up to 0.0947g/cm3。
It should be understood that although the steps in the flowcharts of fig. 4 and 5 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise.
In conclusion, the invention modifies the gamma detector by adopting the design of wrapping the boron sleeve, the boron sleeve can absorb thermal neutrons and emit boron capture gamma rays, the boron capture gamma information is detected by the gamma detector, and then the boron capture gamma is used for replacing the total capture gamma to carry out HI correction, so that the neutron gamma density logging method based on the boron capture gamma correction is obtained, and the influence of the mineralization degree on the density measurement result is greatly reduced; in addition, the boron capture gamma information has little influence on the total capture gamma energy spectrum, can work simultaneously with the neutron gamma density method based on the total capture gamma, and has important significance on the popularization and application of neutron gamma density logging.
The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A neutron-gamma density logging measurement device, comprising: a shell, a main shield, an auxiliary shield, a controllable neutron source, a near detection component and a far detection component,
the housing has an equipment cavity;
the main shielding body is arranged in the equipment cavity and divides the equipment cavity into a transmitting cavity and a receiving cavity;
the secondary shielding body is arranged in the receiving cavity and divides the receiving cavity into a near receiving cavity and a far receiving cavity;
the controllable neutron source is arranged in the emission cavity and is used for emitting neutrons;
the near detection assembly is arranged in the near receiving cavity and comprises a near gamma detector and a first boron carbide rubber sleeve, and the first boron carbide rubber sleeve is sleeved on the near gamma detector;
the far detection assembly is arranged in the far receiving cavity and comprises a far gamma detector and a second boron carbide rubber sleeve, and the second boron carbide rubber sleeve is sleeved on the far gamma detector.
2. The neutron-gamma density logging measurement device of claim 1, wherein the controllable neutron source is a D-T neutron source, the controllable neutron source has a pulse width of 20 μ s, and the controllable neutron source has a duty cycle of 400 μ s.
3. The neutron-gamma density logging measurement device of claim 1, wherein the first and second boron carbide rubber sleeves are each 5mm thick.
4. The neutron-gamma density logging measurement device of claim 1, wherein the primary shield and the secondary shield are both inconel, and the primary shield and the secondary shield are both 5cm thick.
5. The neutron-gamma density logging measurement device of claim 1, wherein the near-gamma detector comprises a first aluminum alloy housing having a first containment chamber that is closed, a first NaI detection crystal, and a first photomultiplier tube; the first NaI detection crystal is arranged in the first accommodating cavity; the first photomultiplier is arranged in the first accommodating cavity and is connected with the first NaI detection crystal; the first boron carbide rubber sleeve is sleeved on the first aluminum alloy shell;
the far gamma detector comprises a second aluminum alloy shell, a second NaI detection crystal and a second photomultiplier, and the second aluminum alloy shell is provided with a closed second containing cavity; the second NaI detection crystal is arranged in the second accommodating cavity; the second photomultiplier is arranged in the second accommodating cavity and is connected with the second NaI detection crystal; the second boron carbide rubber sleeve is sleeved on the second aluminum alloy shell.
6. The neutron-gamma density logging measurement device of claim 5, wherein the first NaI detection crystal is located 30-40cm from the controllable neutron source and the second NaI detection crystal is located 60-70cm from the controllable neutron source.
7. The neutron-gamma density logging measurement device of claim 5, wherein the first NaI detection crystal has a length of 8cm and the second NaI detection crystal has a length of 14 cm.
8. A neutron gamma density logging measurement method is characterized by comprising a density logging coefficient calibration method and a logging while drilling formation density measurement method, wherein,
the density logging coefficient calibration method comprises the following steps:
s11, installing the neutron-gamma density logging measurement device as claimed in any one of claims 1-7 on a drill collar and descending the drill collar into a graduated well with known density;
s12, periodically emitting neutrons through the controllable neutron source, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector and the far gamma detector;
s13, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, determining an energy window corresponding to the boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, making a ratio on the inelastic scattering gamma counts corresponding to the near gamma detector and the far gamma detector, acquiring a first inelastic scattering gamma count ratio, and making a ratio on the boron capture gamma counts corresponding to the near gamma detector and the far gamma detector, and acquiring a first boron capture gamma count ratio;
s14, changing the hydrogen index of the graduated well, and repeating the steps S11-S13;
s15, replacing the scale wells with different densities, and repeating the steps S11-S14;
s16, substituting each first inelastic scattering gamma count ratio, each first boron capture gamma count ratio and the density of each graduated well into a density formula to determine the value of each coefficient in the density formula;
the logging while drilling formation density measurement method comprises the following steps:
s21, mounting the neutron gamma density logging measurement device as set forth in any one of claims 1-7 on a drill collar;
s22, keeping the shell attached to the well wall in the drilling process, periodically emitting neutrons through the controllable neutron source, and continuously receiving inelastic scattering gamma and capturing gamma energy spectrum information through the near gamma detector and the far gamma detector;
s23, determining an energy window corresponding to boron capture gamma information through the capture gamma energy spectrum information received by the near gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, determining an energy window corresponding to the boron capture gamma information through the capture gamma energy spectrum information received by the far gamma detector, acquiring inelastic scattering gamma counts and boron capture gamma counts, making a ratio on the inelastic scattering gamma counts corresponding to the near gamma detector and the far gamma detector, acquiring a second inelastic scattering gamma count ratio, and making a ratio on the boron capture gamma counts corresponding to the near gamma detector and the far gamma detector, and acquiring a second boron capture gamma count ratio;
and S24, substituting the second inelastic scattering gamma count ratio and the second boron capture gamma count ratio into the density formula to determine the density of the stratum.
9. The neutron-gamma density log measurement method of claim 8, wherein the density formula is:
ρ＝A ln(Rin-BRc)+C
where ρ is the formation density, RinIs an inelastic scattering gamma ratio, RcFor the boron capture gamma ratio, A, B, C are all coefficients.
10. The method of neutron-gamma density log measurement as claimed in claim 8, wherein the near gamma detector and the far gamma detector record inelastic scattering gammas in a time window of 0-20 μ s each and capture gammas in a time window of 30-400 μ s each.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112179924A (en) * | 2020-10-23 | 2021-01-05 | 中国石油大学(华东) | Downhole casing damage detection method based on boron neutron capture |
| CN112593923A (en) * | 2020-12-16 | 2021-04-02 | 中国海洋石油集团有限公司 | Method and device for predicting gas saturation based on pulsed neutrons |
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