CN110894785A - Epithermal neutron porosity logging method and equipment - Google Patents
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- 229910052805 deuterium Inorganic materials 0.000 claims abstract description 20
- YZCKVEUIGOORGS-NJFSPNSNSA-N Tritium Chemical compound [3H] YZCKVEUIGOORGS-NJFSPNSNSA-N 0.000 claims abstract description 17
- 238000009792 diffusion process Methods 0.000 claims abstract description 17
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 9
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- VGIBGUSAECPPNB-UHFFFAOYSA-L nonaaluminum;magnesium;tripotassium;1,3-dioxido-2,4,5-trioxa-1,3-disilabicyclo[1.1.1]pentane;iron(2+);oxygen(2-);fluoride;hydroxide Chemical compound [OH-].[O-2].[O-2].[O-2].[O-2].[O-2].[F-].[Mg+2].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[Al+3].[K+].[K+].[K+].[Fe+2].O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2.O1[Si]2([O-])O[Si]1([O-])O2 VGIBGUSAECPPNB-UHFFFAOYSA-L 0.000 description 2
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- E21B47/00—Survey of boreholes or wells
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- E—FIXED CONSTRUCTIONS
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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Abstract
The embodiment of the invention provides a method and equipment for logging porosity of epithermal neutrons, wherein the method comprises the following steps: for pulsed neutron porosity logging of deuterium-tritium D-T sources, the neutron moderation distances are split into neutron moderation distances of two energy segments that are summed, where the two energy segments include neutron fast neutrons E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef(ii) a The method comprises the following steps of (1) expressing the count ratio of the epithermal neutrons of a preset neutron source by using a neutron diffusion theory; converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio; improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain improved neutron porosity; based on the volume model, the improved neutron porosity is used for calculating the formation apparent porosity, the accuracy of formation porosity logging is improved, and the sensitivity of neutron counting to porosity is improvedAnd (4) sensitivity.
Description
Technical Field
The embodiment of the invention relates to the technical field of epithermal neutron porosity logging, in particular to an epithermal neutron porosity logging method and equipment.
Background
The logging is also called geophysical logging, is a method for measuring geophysical parameters by utilizing the geophysical characteristics such as electrochemical characteristics, conductive characteristics, acoustic characteristics, radioactivity and the like of rock strata, and belongs to one of the applied geophysical methods. One of the main methods for measuring the porosity of the formation during neutron logging is epithermal neutron porosity strategy prize, which is the simplest method for measuring the porosity of the formation in all the commercial neutron logs at present.
The traditional epithermal neutron porosity logging uses an americium beryllium (Am-be) neutron source, and due to the fact that the source intensity is low, the epithermal neutron counting statistical error recorded by a detector is large, and the wide application of the epithermal neutron porosity logging is limited. The deuterium-tritium (D-T) neutron generator is used for replacing an americium-beryllium (Am-be) neutron source, so that potential hazards such as stratum pollution are avoided, the source intensity of the deuterium-tritium (D-T) neutron generator is higher than that of the Am-be source by one order of magnitude, and the problem that the counting error of the epithermal neutrons recorded by the detector is large is well solved.
However, the high energy of the neutrons emitted by the deuterium-tritium (D-T) neutron generator can result in a decrease in neutron count ratio sensitivity to porosity.
Disclosure of Invention
The embodiment of the invention provides a epithermal neutron porosity logging method and device, which are used for solving the problem that the neutron energy emitted by a deuterium-tritium (D-T) neutron generator is high, so that the sensitivity of neutron counting ratio to porosity is reduced.
In a first aspect, an embodiment of the present invention provides a epithermal neutron porosity logging method, including:
for pulsed neutron porosity logging of deuterium-tritium D-T sources, the neutron moderation distances are split into neutron moderation distances of two energy segments that are summed, where the two energy segments include neutron fast neutrons E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef；
Expressing the count ratio of the epithermal neutrons of a preset neutron source by the neutron deceleration distance by adopting a neutron diffusion theory, wherein the count ratio of the epithermal neutrons of the preset neutron source comprises the count ratio of the epithermal neutrons under the condition of a deuterium-tritium D-T neutron source;
converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio;
improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain improved neutron porosity;
and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
In a second aspect, an embodiment of the present invention provides epithermal neutron porosity logging equipment, including:
a deceleration distance analysis module for summing neutron deceleration distances of the neutron deceleration distance split into two energy segments for pulsed neutron porosity logging of the deuterium-tritium D-T source, wherein the two energy segments include neutron fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef；
The count ratio determining module is used for expressing the count ratio of the epithermal neutrons of the preset neutron source by the neutron deceleration distance by adopting a neutron diffusion theory, wherein the count ratio of the epithermal neutrons of the preset neutron source comprises the count ratio of the epithermal neutrons under the condition of a deuterium tritium D-T neutron source;
the count ratio conversion module is used for converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio;
the porosity determination module is used for improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain improved neutron porosity; and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
In a third aspect, an embodiment of the present invention provides a computer-readable storage medium, where computer-executable instructions are stored, and when a processor executes the computer-executable instructions, the epithermal neutron porosity logging method according to the first aspect and various possible designs of the first aspect is implemented.
The method and the device for logging the porosity of the epithermal neutrons provided by the embodiment of the invention are realized by the porosity of the pulsed neutrons of a deuterium-tritium D-T sourceLogging, wherein the neutron deceleration distance is divided into two energy sections and the neutron deceleration distance is added, wherein the two energy sections comprise neutron fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef(ii) a The method comprises the following steps of (1) expressing the count ratio of the epithermal neutrons of a preset neutron source by using a neutron diffusion theory; converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio; improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain improved neutron porosity; based on the volume model, the improved neutron porosity is used for calculating the formation apparent porosity, the accuracy of formation porosity logging is improved, and the sensitivity of neutron counting to porosity can be improved. According to the embodiment of the invention, the neutron porosity logging based on the deuterium-tritium neutron source is solved by converting the count ratio of the epithermal neutrons under the condition of the deuterium-tritium D-T neutron source into the count ratio of the epithermal neutrons under the condition of the deuterium-tritium D-D neutron source, so that the problems that the energy of the deuterium-tritium neutron source is high, the sensitivity of the neutron count ratio to the porosity is low, and the neutron porosity is greatly influenced by lithology and fluid are solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic flow chart of a epithermal neutron porosity logging method according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of a neutron pulse sequence used in a simulation of an MCNP according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a simulation model of an MCNP program according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a epithermal neutron porosity logging device according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a hardware structure of an epithermal neutron porosity logging device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic flow chart of a epithermal neutron porosity logging method according to an embodiment of the present invention, where an execution subject of the embodiment may be a terminal in the embodiment shown in fig. 1, or may be a server in the embodiment shown in fig. 1, and the embodiment is not limited herein. As shown in fig. 2, the method includes:
s101: for pulsed neutron porosity logging of deuterium-tritium D-T sources, the neutron moderation distances are split into neutron moderation distances of two energy segments that are summed, where the two energy segments include neutron fast neutrons E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef。
Here, the deceleration distance of a neutron is defined as a fast neutron (E ═ E) injected into the formation0) Moderated to thermal neutrons (E ═ E)f) The linear distance moved. For epithermal neutron logging EfIs 0.025 eV.
If the medium is a substance consisting of light nuclei, the deceleration distance R of the neutronsfCan be expressed as shown in equation 1.
If the medium is composed of a nuclide having a large mass number, the mean square value of the deceleration distance is shown in equation 2.
Wherein: sigmasMacroscopic scattering cross section of rock, A mass number, ξ is the average logarithmic energy loss of rock, related to mass number.
Whether the stratum is composed of light nuclear or nuclide with larger mass number, the deceleration distance R of the neutron is the same stratumfCan be expressed as shown in equation 3.
Wherein b is the macroscopic scattering cross section Σ of the rocksMass number A and average log energy loss of rock ξ for pulsed neutron porosity log for D-T source, the deceleration distance of the neutrons Rf14MeVCan be expressed by equation 4.
The deceleration distances of neutrons in different energy sections simulated by the MCNP are shown in table 1, and it can be seen that the sum of the neutron deceleration distances in different energy sections is close to the neutron deceleration distance in the total energy section, and the estimated formation deceleration length is also close to the real formation deceleration length. Thus, the deceleration distance R of the neutronf14MeVThe neutron moderation distances that can be split into two energy segments are summed as shown in equation 5.
Wherein R isfkMeVNeutron deceleration distance, R, for fast neutrons to 1MeVf1MeVIs the deceleration of neutrons with energy of 1MeV to EfNeutron moderation distance.
TABLE 1 neutron moderation distances for different materials
S102: and expressing the count ratio of the epithermal neutrons of the preset neutron source by the neutron deceleration distance by adopting a neutron diffusion theory, wherein the count ratio of the epithermal neutrons of the preset neutron source comprises the count ratio of the epithermal neutrons under the condition of a deuterium tritium D-T neutron source.
Specifically, S1021: a near detector and a far detector are respectively arranged on two observation points at different distances relative to a neutron source, if the near detector and the far detector only record epithermal neutrons, and an epithermal neutron counting ratio formula is obtained according to a two-component diffusion theory.
The epithermal neutron porosity logging is characterized in that two epithermal neutron detectors, namely a near detector and a far detector, are respectively arranged on two observation points which are at different distances relative to a neutron source. The formation porosity is measured by using the ratio of the near detector counting to the far detector counting, but in actual logging, fast neutrons are not easy to measure, and the error is large. If the detector only records epithermal neutrons, the epithermal neutron count ratio R can be expressed by formula 6 (i.e., neutron diffusion theory formula) according to the two-component diffusion theory.
Wherein phit(r1) Is the epithermal neutron count of a near detector, phit(r2) Is the epithermal neutron count, r, of a far detector1Is the source distance of the proximity detector, r2Is the far detector source distance, LsNeutron moderation length. Length of deceleration LsRefers to the distance that a fast neutron travels from the emission of the neutron source to the energy reduction to the lower energy limit of the epithermal neutron.
S1022: and expressing the neutron deceleration length by using the neutron deceleration distance to obtain a deceleration length expression.
From equation 6, it can be seen that the epithermal neutron count ratio is primarily reflective of the formation deceleration length, however for neutron sources of different energies, the deceleration length of the formation is not the same because the deceleration length is related to the energy at which the particle was emitted and the energy at which it was detected. The deceleration length expression is shown in equation 7.
S1023: and according to the epithermal neutron count ratio formula and the deceleration length expression, simultaneously taking logarithm to obtain the epithermal neutron count ratio under the condition of the low-energy neutron source.
According to equation 6 and equation 7, the epithermal neutron count ratio can be expressed in terms of neutron moderation distance, as shown in equation 8.
Logarithm is taken on two sides, and the count ratio of the epithermal neutrons under the condition of the low-energy neutron source can be represented by formula 9.
Wherein R islIs the epithermal neutron count ratio under the condition of a low-energy neutron source,
the neutron deceleration distance when fast neutrons of energy hMeV decelerate to lMeV,
is the deceleration distance when fast neutrons of the energy lMeV decelerate to epithermal neutrons,
the deceleration distance when fast neutrons of energy hMeV decelerate to epithermal neutrons, and a and c are coefficients related to the source distance.
S1024: and expressing the count ratio of the epithermal neutrons under the condition of the low-energy neutron source by recording the count ratio of the epithermal neutrons under the condition of the high-energy neutron source and the count ratio of the fast neutrons with the energy between h-lMeV to obtain an epithermal neutron count ratio formula under the condition of the deuterium-tritium D-T neutron source.
In the same way, ifThe method is characterized in that the same detector is used for recording the epithermal neutron count ratio under the condition of a high-energy neutron source and the fast neutron count ratio with the energy between h-lMeV, and then the epithermal neutron count ratio can be expressed as
The fast neutron count ratio between h-lMeV can be expressed as
The epithermal neutron count ratio under low energy neutron source conditions can be represented by equation 10:
s103: and converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio.
Fig. 2 is a schematic diagram of a neutron pulse sequence used in a simulation of mcnp (monte Carlo N Particle transport code) according to an embodiment of the present invention; fig. 3 is a schematic diagram of a simulation model of an MCNP program according to an embodiment of the present invention.
In actual logging, fast neutrons are not easy to measure, but the neutrons and elements in the stratum generate non-elastic scattering reaction, the gamma detector is used for replacing the fast neutron detector, and the count ratio of the epithermal neutrons is improved through the non-elastic gamma counting ratio. To meet the requirements of practical application, the data scale is performed by using the epithermal neutron count ratio under the condition of deuterium D-D neutron source. The energy emitted by deuterium D-D neutron source is 2.5MeV fast neutron, because the energy emitted by the deuterium D-D neutron source is lower, the sensitivity of neutron counting ratio to porosity is higher, and the D-D neutron source is a controllable neutron source which is more suitable for neutron porosity logging than a D-T neutron source only in view of the emitted neutron energy, however, the source strength of the D-D source is only 1 x [ (10) 6n/s, the source strength of americium beryllium source is 2-4 x [ (10) 7n/s, and the source strength of the D-T source is 1 x [ (10) 8 n/s. The D-D neutron source can not meet the requirement of logging and speed measurement and is only suitable for static measurement. Therefore, the advantage of low source intensity of the D-D source is made up and the advantage of high porosity sensitivity of the D-D source is fully utilized by using the epithermal neutron counting ratio under the D-D source condition to perform data calibration. And replacing the neutron generator with a D-D neutron source to obtain the epithermal neutron count ratio under the condition of the D-D neutron source, and improving and scaling the relation of the epithermal neutron count ratio conversion under different neutron source conditions.
Specifically, S1031: by setting parameters related to source distance, the epithermal neutron count ratio formula under the condition of the D-D neutron source is obtained by only improving the epithermal neutron count ratio formula under the condition of the deuterium-tritium D-T neutron source.
S1032: the numerical value of the parameter related to the source distance is obtained by calibrating an improved D-D neutron source ratio formula for setting the parameter related to the source distance by simulating pure strata with different lithologies and different porosities and saturated water.
S1033: and substituting the numerical value of the parameter related to the source distance into an improved epithermal neutron counting ratio formula under the D-D neutron source condition to obtain the epithermal neutron counting ratio under the D-D neutron source condition.
In the formula 10, the coefficients a and c are parameters related to the source distance, and only the energy of neutrons is changed during the calibration, so that the coefficients a and c under the condition of the D-D neutron source are the same as those under the condition of the D-T source, and the formula 10 is improved as shown in a formula 11.
Wherein R isiIs a non-elastic gamma ratio, RicFor epithermal neutron count ratios constructed based on non-bomb-gamma ratios, a1, c1, a2, c2 are coefficients. Equation 11 is scaled by simulating pure formations of different lithology and different porosity saturated with water. Wherein c1 is 3.98, a1 is 0.177, c2 is 1.289, and a2 is-1.0472.
S104: improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain the improved neutron porosity: and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
Generally, on the premise of ensuring that the statistical error of neutron counting is small, the sensitivity of counting comparison to porosity is higher, and the accuracy of porosity calculation is higher. Generally, the sensitivity of the count ratio to the porosity is reduced along with the increase of the energy of a neutron source, and the method converts the count ratio under the condition of a high-energy neutron source into the count ratio under the condition of a low-energy neutron source, so that the sensitivity of the count ratio to the porosity is obviously increased after correction.
To fully account for the change in the sensitivity of the count to porosity before and after correction, the sensitivity of the count to porosity before and after improvement was calculated using equation 12, as shown in table 2.
TABLE 2 sensitivity of counts to porosity before and after improvement
Wherein S is the sensitivity of the count to porosity, SRSensitivity of the count to porosity for no improvement, SRicSensitivity to porosity for improved counts. It can be seen from table 2 that the sensitivity to porosity is significantly improved from the improved count ratio, especially in highly porous formations.
The neutron porosity can be influenced by lithology, and in order to research the influence of the lithology on the improved neutron porosity, the logging response of strata with different porosities under three lithologies of dolomite, limestone and sandstone is simulated and is compared with the uncorrected neutron porosity to the greatest extent.
Neutron porosity logs reflect primarily the hydrogen content of the formation. Due to the fact that the hydrogen content of the argillaceous materials is high, when the argillaceous materials exist in the stratum, the neutron porosity is high, and the argillaceous materials generally contain more chemical elements and can have certain influence on well logging response. To investigate the effect of the shale on the modified neutron porosity response, formations of different porosities were simulated at shale contents of 20% and 40%. Wherein the argillaceous material is illite, the rock skeleton is CaCO3, and the fluid in the pores is fresh water. And most contrasted with uncorrected neutron porosity.
The neutron porosity under different argillaceous conditions was compared to the saturated water pure limestone line. As the argillaceous content increases, the neutron porosity deviates from the saturated water pure limestone line. Corrected neutron porosity is relatively less affected by the mudiness, especially in highly porous formations.
The fluid in the pores is also one of the important factors affecting the neutron porosity response. Particularly gas-saturated formations, even if the hydrogen content in the formation increases with increasing porosity, the neutron porosity even increases inversely due to the excavation effect caused by the lower gas density. To investigate the effect of the fluid in the pores on the modified neutron porosity response, a pure limestone formation saturated with oil and gas in the pores was simulated, where oil has the chemical formula CH1.8Density of 0.89g/cm3The chemical formula of gas is CH4Density of 0.15g/cm3The rock skeleton is CaCO3. In contrast to uncorrected neutron porosity.
The influence of the fluid on the neutron porosity is more complex, the influence of the oil on the neutron porosity depends on the hydrogen index of the oil, if the hydrogen index of the oil is higher than that of fresh water, the neutron porosity before and after improvement is higher than the formation porosity, but for the gas-saturated formation, due to the influence of the excavation effect, the neutron porosity which is not improved is increased and then reduced along with the increase of the porosity. The improved neutron porosity is less affected by the excavation effect, and increases with increasing porosity.
In this embodiment, the obtaining of the improved neutron porosity by improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition includes:
obtaining a formation hydrogen index according to the count ratio of the epithermal neutrons under the condition of a D-D neutron source;
and obtaining the improved neutron porosity according to the hydrogen index of the stratum.
In this embodiment, the calculating the formation apparent porosity using the modified neutron porosity based on the volume model includes:
wherein phiaTo the apparent porosity, phinIs neutron porosity, phimaIs the value of the neutron porosity of the skeleton, VshIs a muddy content ofshNeutron porosity value, phi, of argillaceous materialfIs the neutron porosity value of the fluid.
The neutron porosity logging response can be influenced by factors such as rock cores and fluids, especially the D-T neutron source is used for logging, the D-T neutron source is high in energy, so that the logging response is greatly influenced by factors such as lithology and fluids, and the porosity calculated based on the volume model can deviate from the formation porosity to a certain extent. And porosity is calculated using the modified neutron porosity based on the volume model, as shown in equation 14. In contrast to porosity calculated for uncorrected neutron porosity. The rock skeleton is limestone and the argillaceous is illite.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
Referring to fig. 4, fig. 4 is a schematic structural diagram of an epithermal neutron porosity logging apparatus according to an embodiment of the present invention. As shown in fig. 4, the epithermal neutron porosity logging apparatus 40 includes: a deceleration distance analysis module 401, a count ratio determination module 402, a count ratio conversion module 403, and a porosity determination module 404.
A moderation distance analysis module 401 for, for pulsed neutron porosity logging of a deuterium-tritium D-T source, summing neutron moderation distances split into two energy segments, wherein the two energy segments include neutron-fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef；
A count ratio determining module 402, configured to use a neutron diffusion theory to represent a count ratio of epithermal neutrons of a preset neutron source by the neutron deceleration distance, where the count ratio of epithermal neutrons of the preset neutron source includes the count ratio of epithermal neutrons under a deuterium tritium D-T neutron source condition;
a count ratio conversion module 403, configured to convert the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by using a non-bomb gamma count ratio;
a porosity determination module 404, configured to improve a count ratio of the epithermal neutrons under the D-D neutron source condition with respect to a count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain an improved neutron porosity; and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
The device provided in this embodiment may be used to implement the technical solution of the above method embodiment, and the implementation principle and technical effect are similar, which are not described herein again.
In one embodiment of the invention, the deceleration distance analysis module is used for adding the neutron deceleration distance obtained by splitting the neutron deceleration distance into two energy segments, wherein the two energy segments comprise neutron fast neutrons E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron EfThe method comprises the following steps:
wherein R isfkNeutron deceleration distance, R, for fast neutrons to 1MeVf1Is the deceleration of neutrons with energy of 1MeV to EfNeutron moderation distance.
In an embodiment of the present invention, the count ratio determining module is configured to represent, by using a neutron diffusion theory, a count ratio of epithermal neutrons of a preset neutron source by the neutron deceleration distance, where the count ratio of epithermal neutrons of the preset neutron source includes a count ratio of epithermal neutrons under a condition of a deuterium tritium D-T neutron source, and includes:
respectively arranging a near detector and a far detector on two observation points at different distances relative to a neutron source, and if the near detector and the far detector only record epithermal neutrons, obtaining an epithermal neutron counting ratio formula according to a two-component diffusion theory;
expressing the neutron deceleration length by using the neutron deceleration distance to obtain a deceleration length expression;
according to the epithermal neutron count ratio formula and the deceleration length expression, taking logarithm in a simultaneous manner to obtain the epithermal neutron count ratio under the condition of a low-energy neutron source;
and expressing the count ratio of the epithermal neutrons under the condition of the low-energy neutron source by recording the count ratio of the epithermal neutrons under the condition of the high-energy neutron source and the count ratio of the fast neutrons with the energy between h-lMeV to obtain an epithermal neutron count ratio formula under the condition of the deuterium-tritium D-T neutron source.
The device provided in this embodiment may be used to implement the technical solution of the above method embodiment, and the implementation principle and technical effect are similar, which are not described herein again.
Referring to the drawings, fig. 5 is a schematic diagram of a hardware structure of an epithermal neutron porosity logging device according to an embodiment of the present invention. As shown in fig. 5, the epithermal neutron porosity logging apparatus 50 of the present embodiment includes: a processor 501 and a memory 502; wherein
A memory 502 for storing computer-executable instructions;
the processor 501 is configured to execute the computer-executable instructions stored in the memory to implement the steps performed by the terminal or the server in the above embodiments. Reference may be made in particular to the description relating to the method embodiments described above.
Alternatively, the memory 502 may be separate or integrated with the processor 501.
When the memory 502 is separately provided, the epithermal neutron porosity logging device further comprises a bus 503 for connecting the memory 502 and the processor 501.
An embodiment of the present invention further provides a computer-readable storage medium, where computer-executable instructions are stored in the computer-readable storage medium, and when a processor executes the computer-executable instructions, the epithermal neutron porosity logging method as described above is implemented.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described device embodiments are merely illustrative, and for example, the division of the modules is only one logical division, and other divisions may be realized in practice, for example, a plurality of modules may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or modules, and may be in an electrical, mechanical or other form.
The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to implement the solution of the present embodiment.
In addition, functional modules in the embodiments of the present invention may be integrated into one processing unit, or each module may exist alone physically, or two or more modules are integrated into one unit. The unit formed by the modules can be realized in a hardware form, and can also be realized in a form of hardware and a software functional unit.
The integrated module implemented in the form of a software functional module may be stored in a computer-readable storage medium. The software functional module is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) or a processor to execute some steps of the methods described in the embodiments of the present application.
It should be understood that the Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of a method disclosed in connection with the present invention may be embodied directly in a hardware processor, or in a combination of the hardware and software modules within the processor.
The memory may comprise a high-speed RAM memory, and may further comprise a non-volatile storage NVM, such as at least one disk memory, and may also be a usb disk, a removable hard disk, a read-only memory, a magnetic or optical disk, etc.
The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended ISA (Extended Industry Standard Architecture) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, the buses in the figures of the present application are not limited to only one bus or one type of bus.
The storage medium may be implemented by any type or combination of volatile or non-volatile memory devices, such as Static Random Access Memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic or optical disks. A storage media may be any available media that can be accessed by a general purpose or special purpose computer.
An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an Application Specific Integrated Circuits (ASIC). Of course, the processor and the storage medium may reside as discrete components in an electronic device or host device.
Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A epithermal neutron formation porosity logging method, comprising:
for pulsed neutron porosity logging of deuterium-tritium D-T sources, the neutron moderation distances are split into neutron moderation distances of two energy segments that are summed, where the two energy segments include neutron fast neutrons E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef；
Expressing the count ratio of the epithermal neutrons of a preset neutron source by the neutron deceleration distance by adopting a neutron diffusion theory, wherein the count ratio of the epithermal neutrons of the preset neutron source comprises the count ratio of the epithermal neutrons under the condition of a deuterium-tritium D-T neutron source;
converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio;
improving the count ratio of the epithermal neutrons under the D-D neutron source condition to the count ratio of the epithermal neutrons under the deuterium tritium D-T neutron source condition to obtain improved neutron porosity;
and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
2. The method of claim 1, wherein said splitting neutron moderation distanceAdding neutron moderation distances for two energy segments, wherein two energy segments include neutron fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron EfThe method comprises the following steps:
for pulsed neutron porosity logging with a D-T source,
wherein R isfkMeVNeutron deceleration distance, R, for fast neutrons to 1MeVf1MeVIs the deceleration of neutrons with energy of 1MeV to EfNeutron moderation distance.
3. The method of claim 2, wherein the representing a predetermined neutron source epithermal neutron count ratio by the neutron moderating distance using neutron diffusion theory, wherein the predetermined neutron source epithermal neutron count ratio comprises an epithermal neutron count ratio under deuterium tritium D-T neutron source conditions, comprises:
respectively arranging a near detector and a far detector on two observation points at different distances relative to a neutron source, and if the near detector and the far detector only record epithermal neutrons, obtaining an epithermal neutron counting ratio formula according to a two-component diffusion theory;
expressing the neutron deceleration length by using the neutron deceleration distance to obtain a deceleration length expression;
according to the epithermal neutron count ratio formula and the deceleration length expression, taking logarithm in a simultaneous manner to obtain the epithermal neutron count ratio under the condition of a low-energy neutron source;
and (3) expressing the count ratio of the epithermal neutrons under the condition of a low-energy neutron source by recording the count ratio of the epithermal neutrons under the condition of a high-energy neutron source and the count ratio of the fast neutrons with the energy between h-1MeV to obtain an epithermal neutron count ratio formula under the condition of a deuterium-tritium D-T neutron source.
4. The method of claim 3, wherein converting the count ratio of epithermal neutrons under D-T neutron source conditions to the count ratio of epithermal neutrons under D-D neutron source conditions using a non-bomb-gamma ratio comprises:
by setting parameters related to source distance, an epithermal neutron counting ratio formula under the condition of a D-D neutron source is obtained by improving the epithermal neutron counting ratio formula under the condition of a deuterium tritium D-T neutron source;
calibrating an improved D-D neutron source ratio formula for setting parameters related to source distance by simulating pure strata with different lithologies and different porosities and saturated water to obtain numerical values of the parameters related to the source distance;
and substituting the numerical value of the parameter related to the source distance into an improved epithermal neutron counting ratio formula under the D-D neutron source condition to obtain the epithermal neutron counting ratio under the D-D neutron source condition.
5. The method of claim 4, wherein improving the epithermal neutron count ratio under a D-D neutron source versus a deuterium tritium D-T neutron source to obtain an improved neutron porosity comprises:
obtaining a formation hydrogen index according to the count ratio of the epithermal neutrons under the condition of a D-D neutron source;
and obtaining the improved neutron porosity according to the hydrogen index of the stratum.
6. The method of claim 5, wherein calculating the formation apparent porosity using the refined neutron porosity based on the volumetric model comprises:
wherein phiaTo the apparent porosity, phinIs neutron porosity, phimaIs the value of the neutron porosity of the skeleton, VshIs a muddy content ofshNeutron porosity value, phi, of argillaceous materialfIs the neutron porosity value of the fluid.
7. An epithermal neutron porosity logging device, comprising:
a deceleration distance analysis module for summing neutron deceleration distances of the neutron deceleration distance split into two energy segments for pulsed neutron porosity logging of the deuterium-tritium D-T source, wherein the two energy segments include neutron fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron Ef；
The count ratio determining module is used for expressing the count ratio of the epithermal neutrons of the preset neutron source by the neutron deceleration distance by adopting a neutron diffusion theory, wherein the count ratio of the epithermal neutrons of the preset neutron source comprises the count ratio of the epithermal neutrons under the condition of a deuterium tritium D-T neutron source;
the count ratio conversion module is used for converting the count ratio of the epithermal neutrons under the D-T neutron source condition into the count ratio of the epithermal neutrons under the D-D neutron source condition by utilizing the non-bomb gamma count ratio;
the porosity determination module is used for obtaining improved neutron porosity by utilizing the count ratio of the epithermal neutrons under the condition of a D-D neutron source; and calculating the formation apparent porosity by using the improved neutron porosity based on the volume model.
8. The apparatus of claim 7, wherein the moderation distance analysis module is configured to add neutron moderation distances that split the neutron moderation distance into two energy segments, wherein two energy segments include neutron fast neutron E0Moderation to 1MeV and neutron moderation from 1MeV to epithermal neutron EfThe method comprises the following steps:
wherein R isfkNeutron deceleration distance, R, for fast neutrons to 1MeVf1Is the deceleration of neutrons with energy of 1MeV to EfNeutron moderation distance.
9. The apparatus of claim 8, wherein the count ratio determination module is configured to use neutron diffusion theory to represent a predetermined neutron source epithermal neutron count ratio by the neutron deceleration distance, wherein the predetermined neutron source epithermal neutron count ratio comprises an epithermal neutron count ratio under a deuterium tritium D-T neutron source condition, and comprises:
respectively arranging a near detector and a far detector on two observation points at different distances relative to a neutron source, and if the near detector and the far detector only record epithermal neutrons, obtaining an epithermal neutron counting ratio formula according to a two-component diffusion theory;
expressing the neutron deceleration length by using the neutron deceleration distance to obtain a deceleration length expression;
according to the epithermal neutron count ratio formula and the deceleration length expression, taking logarithm in a simultaneous manner to obtain the epithermal neutron count ratio under the condition of a low-energy neutron source;
and (3) expressing the count ratio of the epithermal neutrons under the condition of a low-energy neutron source by recording the count ratio of the epithermal neutrons under the condition of a high-energy neutron source and the count ratio of the fast neutrons with the energy between h-1MeV to obtain an epithermal neutron count ratio formula under the condition of a deuterium-tritium D-T neutron source.
10. A computer readable storage medium having computer executable instructions stored thereon which, when executed by a processor, implement the epithermal neutron porosity logging method of any of claims 1-6.
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