CN114414027A - Method for calculating sound velocity of supporting conglomerate and non-supporting conglomerate - Google Patents
Method for calculating sound velocity of supporting conglomerate and non-supporting conglomerate Download PDFInfo
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Abstract
The invention discloses a method for calculating the sound velocity of supported and unsupported conglomerates. Compared with the prior art, the calculation method can calculate the acoustic velocity of the gravels with more complicated lithology, has good accuracy, and provides a basis for accurately forward predicting the acoustic velocity of the supported gravels and the acoustic velocity of the unsupported gravels and applying earthquake and logging to invert parameters such as porosity and the like.
Description
Technical Field
The invention belongs to the technical field of petroleum and gas exploration, and relates to a method for calculating the sound velocity of supported conglomerates and unsupported conglomerates.
Background
Conglomerate reservoirs are one of the most important. The sound velocity is one of the most important rock physical characteristic parameters of the conglomerate, can reflect the properties of a framework and pore fluid, and is an important physical property for evaluating parameters such as the porosity and the saturation of a reservoir by earthquake and well logging.
The conglomerates are divided into two types, namely supported conglomerates mainly based on line contact and contact type cementing and unsupported conglomerates mainly based on non-contact and substrate type cementing according to different contact relations and cementing modes between the conglomerates, and the difference of mechanical properties between the supported conglomerates and the unsupported conglomerates has different influences on the acoustic properties of the conglomerates and needs to be distinguished when the acoustic properties of the conglomerates are researched.
Due to poor homogeneity and complex acoustic properties of the conglomerate, the existing conglomerate sound velocity model mainly takes an empirical formula, only influences of lithology and physical properties on the conglomerate sound velocity are considered, influences of contact relation among the gravels and cementing action on the conglomerate sound velocity are ignored, and a certain physical basis is lacked. In addition, the previous researches find that the difference of contact relation and cementing mode between gravels is an important reason for the dispersion of the conglomerate sound velocity-porosity intersection map data, the existing conglomerate sound velocity model does not distinguish the supported conglomerate from the non-supported conglomerate from the mechanical angle, and cannot explain the phenomenon that the conglomerate sound velocity is seriously dispersed under the condition of the same porosity, so that the existing conglomerate sound velocity model is not suitable for calculating the conglomerate sound velocity with more complicated lithology.
Therefore, a conglomerate sound velocity calculation method for systematically investigating the contact relation and the cementing action among gravels is needed to be established so as to accurately forward predict the sound velocity of the supporting conglomerate and the non-supporting conglomerate and provide a basis for applying earthquake and logging sound velocity to invert parameters such as porosity and the like. Through retrieval, no report of a literature on a method for calculating the sound velocity of the supported conglomerate and the non-supported conglomerate is found in the prior art.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for calculating the sound velocity of the gravel rocks supported and gravel rocks unsupported, the method for calculating the sound velocity of the gravel rocks divides the gravel rocks into the gravel rocks supported and the gravel rocks unsupported, and the method for calculating the sound velocity of the gravel rocks is used for establishing a system to investigate the contact relation and the cementation between the gravels through the equivalent modulus of the gravel rocks supported and the equivalent modulus of the gravel rocks unsupported. The calculation method can calculate the acoustic velocity of the gravels with more complicated lithology, has good accuracy, provides a basis for accurately forward predicting the acoustic velocity of the supported gravels and the acoustic velocity of the unsupported gravels, and inversing parameters such as porosity and the like by applying earthquake and logging acoustic velocity.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for calculating the sound velocity of the supported and unsupported conglomerates is characterized in that the conglomerates are used as the supported conglomerates and the unsupported conglomerates, and the sound velocity of the supported conglomerates and the unsupported conglomerates is calculated by utilizing the equivalent modulus of the filler, the equivalent modulus of the supported conglomerates and the equivalent modulus of the unsupported conglomerates.
Specifically, the method for calculating the sound velocity of the supporting conglomerate and the non-supporting conglomerate comprises the following steps:
s1, measuring the content of medium gravel and the content of gap filler in the conglomerate sample by adopting particle size analysis;
s2, based on the core picture and the slice identification result of the conglomerate sample, dividing the conglomerate sample into a supporting conglomerate and a non-supporting conglomerate according to the contact relation and the cementing mode between the gravels;
s3, calculating the equivalent modulus of the supporting conglomerate obtained in the step S2:
for the supporting conglomerate, determining the distribution mode of the gap filler according to the identification result of the supporting conglomerate sample slice, and calculating to obtain the equivalent modulus of the supporting conglomerate according to the concepts of cementing the gap filler, dispersing the gap filler to fill pores and replacing a neutral framework by a structural gap filler;
s4, calculating the equivalent modulus of the unsupported conglomerate obtained in the step S2;
and for the non-support conglomerate, discontinuously, unevenly and randomly filling medium gravels into the gap filler by using a differential equivalent medium model, and calculating to obtain the equivalent modulus of the non-support conglomerate.
S5, calculating the sound velocity of the supporting conglomerate and the non-supporting conglomerate;
for the gap filler, taking gravel and sand in the gap filler as a skeleton, taking clay as a cementing material, taking the porosity of the gap filler as the existing porosity of the gap filler, and calculating to obtain the equivalent modulus of the gap filler based on an expanded second-stage contact cementing theory;
and substituting the obtained filler equivalent modulus into the supported conglomerate equivalent modulus obtained in the step S3 and the non-supported conglomerate equivalent modulus obtained in the step S4, and calculating to obtain the sound velocity of the supported conglomerate and the non-supported conglomerate.
The invention also provides application of the sound velocity calculation method in forward prediction of the sound velocities of the supported conglomerate and the non-supported conglomerate or in inversion estimation of the porosity of the supported conglomerate and the non-supported conglomerate through earthquake and well logging.
The invention has the beneficial effects that:
the method for calculating the sound velocity of the gravels divides the gravels into the supporting gravels and the non-supporting gravels, and establishes a system for investigating the contact relation and the cementation between the gravels through the equivalent modulus of the supporting gravels and the equivalent modulus of the non-supporting gravels. Compared with the prior art, the calculation method can calculate the acoustic velocity of the gravels with more complicated lithology, has good accuracy, and provides a basis for accurately forward predicting the acoustic velocity of the supported gravels and the acoustic velocity of the unsupported gravels and applying earthquake and logging to invert parameters such as porosity and the like.
Drawings
FIG. 1 is a photograph of a conglomerate-bearing core and a slice identification chart thereof;
FIG. 2 is a photograph of an unsupported conglomerate core and a slice identification chart thereof;
wherein, a is a core photo, b is a sheet under a mirror, 1 is a medium gravel framework, 2 is a gap filler of fine gravel and silt, and the boundary line is a medium gravel boundary.
FIG. 3 is a schematic view of supporting pebble under-mirror lamellae and shim distribution (red for mid-pebble boundaries);
wherein 1 is a cementitious filler, 2 is a structural filler, and 3 is a dispersion filler, wherein the boundary line is a midgravel boundary.
FIG. 4 is a flow chart of the method of the present invention.
FIG. 5 is a graphical representation of the identification of the cementitious filler content in the supporting conglomerate using IPP software, wherein 4 is a cementitious filler.
FIG. 6 is a graph of identifying interblade porosity in a supporting conglomerate using IPP software; wherein 5 is the inter-gravel pore space.
FIG. 7 is a schematic diagram of two cement distribution forms in an expanded CCT model; wherein c is that the cementing material is only distributed among the particles, and d is that the cementing material is uniformly distributed on the surfaces of the particles.
FIG. 8 is a graphical illustration of the solution process for the equivalent modulus of the supporting conglomerate and the non-supporting conglomerate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention are further described below with reference to the accompanying drawings and specific embodiments.
The method for calculating the acoustic velocity of the supported conglomerates and the non-supported conglomerates comprises the steps of firstly dividing the conglomerates into two types, namely a supported conglomerate (shown in figure 1) and a non-supported conglomerate (shown in figure 2) according to the contact relation and the cementing mode between the gravels, wherein the gravels of the supported conglomerates are in close contact and have strong cementing action, and the gravels of the non-supported conglomerates are not in contact and have no cementing action.
Secondly, medium gravel (with the particle size larger than 2mm) is used as a framework, fine gravel and mud sand (with the particle size smaller than or equal to 2mm) are used as fillers to be filled between the medium gravel frameworks for the supporting conglomerate, the fillers are divided into three parts, namely cementing fillers, dispersion fillers and structural fillers according to the distribution form of the fillers in the supporting conglomerate (as shown in figure 3), and the concept that the cementing fillers play a cementing role, the dispersion fillers play a pore filling role, and the structural fillers replace the neutral framework is introduced into the calculation of the equivalent modulus of the supporting conglomerate on the basis of the expanded first-stage Contact Cementing Theory (CCT), a differential equivalent medium model (DEM) and an unconsolidated rock model, so that the equivalent modulus of the supporting conglomerate is obtained.
Then, the medium gravel is used as a wrapping body for the non-support conglomerate, the gap filler is used as a main component of the rock, the medium gravel is discontinuously, unevenly and randomly filled into the gap filler by utilizing a differential equivalent medium model, and the equivalent modulus of the non-support conglomerate is further obtained.
Finally, as for the gap filler, due to the fact that the property of the gap filler is close to that of the argillaceous sandstone, fine gravel and medium sand in the gap filler can be used as a framework, clay is used as a cementing material, the gap filler porosity is used as the existing porosity of the gap filler, the equivalent modulus of the gap filler is calculated based on an expanded second-stage contact cementing theory, the equivalent modulus of the gap filler is brought into the calculation process of the equivalent modulus of the supporting conglomerate and the non-supporting conglomerate, and finally, a method for calculating the sound velocity of the supporting conglomerate and the non-supporting conglomerate (dry sample) by means of system investigation of contact relation between gravels and cementing effect is established.
Specifically, the method for calculating the sound velocity of the supported conglomerates and the unsupported conglomerates (as shown in fig. 4) comprises the following steps:
and S1, determining the content of medium gravel and the content of gap fillers such as fine gravel, silt and the like according to the result of particle size analysis.
And S2, based on the conglomerate core picture and the slice identification result, dividing the conglomerate into supporting conglomerate and non-supporting conglomerate according to the contact relation between the conglomerate and the cementing mode.
S3, calculating the equivalent modulus of the supporting conglomerate:
for supporting conglomerates:
1. determining the distribution mode of the gap filler according to the identification result of the supporting conglomerate sample slice (as shown in figure 3): wherein, the gap filler is cemented and mainly plays a cementing role when being distributed between the medium gravel and the medium gravel framework; the gap filler is dispersed, and the gap filler mainly plays a role of filling the gap when being distributed in the gaps among the gravels; the structural filler is mainly used for replacing the skeleton when the filler is distributed inside the gravel skeleton.
2. At the same time, it is assumed that the conglomerate-supporting framework to be cemented is of porosity phi0Equivalent spherical particles with the coordination number C ═ 7 and the average 0.4 are closely and randomly arranged, and the structural filler content V is calculated according to a material balance equationstructureThe specific calculation formula is as follows:
Vg+Vstructure+Φ0＝1 (1)
wherein, VgIs the content of medium gravel skeleton, VstructureFor structural filler content, phi0Is the critical porosity.
3. Quantitative discrimination of cementitious interstitial content V using a dye-mark-pixel pickup method based on support conglomerate slice identification resultscement(As shown in FIG. 5, the green part is glueJunction interstitials) and the degree of intergranular porosity Φ1(the blue portion is inter-pebble porosity, as shown in FIG. 6). The dispersion gap filler content VdispersedAnd the porosity of the filler phi2The calculation formula of (a) is as follows:
Vdispersed＝Φ0-Φ1-Vcement (2)
Φ2＝Φ-Φ1 (3)
where Φ is the total porosity of the conglomerate.
Calculating the equivalent modulus of the supporting conglomerate according to the distribution mode of the filler and an applicable theory (as shown in figure 8), wherein the specific calculation steps are as follows:
(1) for supporting conglomerates, the cementing action of the conglomerate skeleton and the cementing filler is first considered, i.e. the addition of the cementing filler to the conglomerate skeleton acts to reduce the porosity and increase the equivalent modulus of the assembly of particles (skeleton). Therefore, the equivalent skeleton modulus K after the medium gravel cemented filler is cemented is calculated by utilizing an expanded first-stage continuous cementation theory (a first-stage expanded CCT model)cct、GcctThe specific calculation formula is shown as follows;
cement distribution mode 1:
cement distribution mode 2:
in the formula, alpha1The ratio of the radius of the cementing plane to the radius of the medium gravel particles is the normalized cementing radius; ε is the ratio of the center thickness of the cement to the radius of the particles, i.e., the normalized center thickness of the cement; phi0Critical porosity for the supporting conglomerate; phi is the total voidage of the supporting conglomerate; gc(i.e., mu in this context)cct2) And G (i.e., μ in this context)C) Shear modulus of the cement filler and the gravel skeleton particles respectively; v. ofcAnd v is the poisson's ratio of the cementitious filler and the gravel skeleton particles, respectively.
(2) Utilizing differential equivalent medium theory (DEM model) to carry out skeleton replacement, and calculating equivalent modulus K after the structure filler replaces the medium gravel skeletoncctdem、GcctdemThe specific calculation formula is as follows:
in the formula K*(0)＝K1，μ*(0)＝μ1As an initial condition for the coupled differential equation; k1，μ1Bulk and shear moduli of the background Medium (first phase, i.e., K)cct、Gcct)；K2，μ2Gradual addition of inclusions bulk modulus and shear dieAmount (bulk modulus K of the second phase, i.e. structural intersticecct2And shear modulus mucct2) (ii) a y-volume fraction of phase 2 (i.e., volume fraction of structural interstitials); p and Q are geometric factors used to characterize the filler geometry (assuming a structural interstice aspect ratio of 1.0 instead of pebbles as the skeleton), and the superscript 2 of P and Q means that this geometric factor is for a structural interstice with an equivalent modulus K*And mu*(i.e. K)cctdemAnd Gcctdem) The main phase background medium of (2).
(3) The equivalent modulus of elasticity of the supporting conglomerate (dry sample) after filling of the dispersion filler is calculated by using an unconsolidated rock model. The calculation formula is as follows:
in the formula, KeffAnd GeffRespectively equivalent bulk modulus and equivalent shear modulus of the supporting conglomerate under specific porosity; phi is the existing porosity, phi1The porosity between gravels. KcctdemAnd GcctdemAnd respectively calculating the equivalent bulk modulus and the shear modulus obtained by using the expanded first-stage CCT model and the DEM model. KsAnd GsThe equivalent framework bulk modulus and shear modulus of the medium gravel and the structural filler are respectively calculated by a Voigt-reus-Hill model.
S4, calculating the equivalent modulus of the unsupported conglomerate;
for unsupported conglomerates: the contact between the medium gravel frameworks is lost, the cementation effect is weak, and the equivalent modulus of the non-support gravel rock can not be calculated by continuously using a contact cementation theory. When the gap filler is used as the main component of the rock, and the medium gravel is unevenly, discontinuously and isolated suspended in the gap filler, the DEM model can be applied to randomly fill the medium gravel into the gap filler as inclusions, and further obtain the equivalent modulus of the non-support conglomerate (as shown in figure 8). The calculation formula of the equivalent bulk modulus and the equivalent shear modulus of the non-support conglomerate is as follows:
wherein K (0) is Kcct2，μ*(0)＝μcct2As initial conditions for coupled differential equations, where Kcct2，μcct2Calculating the equivalent bulk modulus and shear modulus (namely the first phase, the gap filler such as pebbles and the like) of the background medium by using a second-stage expanded CCT model; kC，μCThe equivalent bulk modulus and shear modulus for the progressively added inclusions of medium gravel (i.e., second phase, medium gravel); vCThe content of medium gravel; p and Q are geometric factors used to characterize the inclusion geometry, and the superscript 2 of P and Q means that this geometric factor is for inclusion material in a primary phase background medium with equivalent moduli K and μ.
S5, calculating the sound velocity of the supporting conglomerate and the non-supporting conglomerate:
because the properties of the filler are closer to those of argillaceous sandstone, the fine gravel and sand in the filler can be regarded as quartz skeleton, the clay as cement, and the porosity of the filler as the existing porosity of the filler itself; and assuming that the framework of the initially cemented argillaceous sandstone is of porosity phi0Equivalent spherical particles with the coordination number C of 0.36 and the average coordination number C of 9 are closely and randomly arranged, and the equivalent modulus K of the gap filler is calculated by adopting a second-stage expanded CCT modelcct2、μcct2；
And sequentially bringing the obtained equivalent modulus of the gap filler into the equivalent modulus calculation process of the supported conglomerate and the non-supported conglomerate, and further establishing a method for calculating the sound velocity of the supported conglomerate and the non-supported conglomerate by observing the contact relation and the cementation between the gravels through a system.
Example 1
The method of the invention is used for carrying out sound velocity calculation on the supported conglomerate and the non-supported conglomerate, and the operation method comprises the following steps:
s1, respectively selecting 2 supporting conglomerates and 2 non-supporting conglomerate samples (dry samples), and measuring the porosity of the samples
Density rho, longitudinal and transverse wave velocity Vp、Vs；
S2, measuring the content of medium gravel and the content of fillers such as fine gravel, silt and the like in each of the 4 samples by utilizing particle size analysis;
s3, observing the flake supporting the conglomerate sample under the mirror to determine the distribution mode of the gap filler, using Image processing software to dye and label the cementation gap filler and the gravel gap, using Image-pro-plus software to pick up the pixel of the cementation gap filler and the gravel gap, determining the content V of the cementation gap fillercementAnd the size of the inter-gravel porosity phi1；
S4, determining the content V of the structural filler in the conglomerate by using a material balance methodstructureDispersion gap filler content VdispersedAnd the porosity of the filler phi2；
S5, for supporting conglomerates, calculating to obtain the equivalent skeleton modulus K of the medium gravel and cemented gap filler by utilizing an expanded first-stage CCT modelcct、Gcct(ii) a Secondly, calculating the equivalent modulus K after the gravel in the replacement part of the structural filler is used as a framework based on the DEM modelcctdem、Gcctdem(ii) a Finally, according to the unconsolidated rock model, the dispersion gap filler is filled into the gravel pore space, and the equivalent modulus K of the supporting conglomerate (dry sample) is calculatedeff1、Geff1；
S6, directly adopting DEM model to fill the medium gravel serving as inclusion into gap filler such as gravel unevenly, discontinuously and randomly, and calculating to obtain equivalent modulus K of the unsupported conglomerateeff2、Geff2；。
S7, for the gap filler, the fine gravel and the sand are used as the framework, the clay is used as the cementing material, and the porosity of the gap filler is used asCalculating the equivalent modulus K of the filler for its own existing porosity using a second-stage expanded CCT modelcct2、μcct2。
S8, calculating the longitudinal and transverse wave velocities V of the supporting conglomerate and the non-supporting conglomerate respectively by using the obtained equivalent modulus of the supporting conglomerate and the non-supporting conglomeratep1、Vs1，Vp2、Vs2。
The calculation results are shown in table 1:
table 1 example 1 calculation results
Note: 1. sample No. 2 is a supporting conglomerate, and sample nos. 3 and 4 are non-supporting conglomerates.
As shown in Table 1, the longitudinal and transverse wave velocities of the supported conglomerates and the unsupported conglomerates obtained by applying the new model calculation are consistent with the experimental measurement results, wherein the relative prediction error of the longitudinal wave velocity is less than 5%, and the relative prediction error of the transverse wave velocity is less than 11%.
The calculation method can calculate the acoustic velocity of the gravels with more complicated lithology, has good accuracy, and provides a basis for accurately forward predicting the acoustic velocity of the supported gravels and the acoustic velocity of the unsupported gravels and applying earthquake and logging to invert parameters such as porosity and the like.
It should be emphasized that the embodiments described herein are illustrative rather than restrictive, and thus the present invention is not limited to the embodiments described in the detailed description, but also includes other embodiments that can be derived from the technical solutions of the present invention by those skilled in the art.
Claims (10)
1. A method for calculating the sound velocity of the supported and unsupported conglomerates is characterized in that the conglomerates are used as the supported conglomerates and the unsupported conglomerates, and the sound velocity of the supported conglomerates and the unsupported conglomerates is calculated by utilizing the equivalent modulus of the filler, the equivalent modulus of the supported conglomerates and the equivalent modulus of the unsupported conglomerates.
2. The sound speed calculation method according to claim 1, characterized by comprising the steps of:
s1, measuring the content of medium gravel and the content of gap filler in the conglomerate by adopting particle size analysis;
s2, based on the core picture and slice identification result of the conglomerate, dividing the conglomerate into a supporting conglomerate and a non-supporting conglomerate according to the contact relation and cementing mode between the conglomerates;
s3, calculating the equivalent modulus of the supporting conglomerate obtained in the step S2:
for the supporting conglomerate, determining the distribution mode of the gap filler according to the identification result of the supporting conglomerate sample slice, and calculating to obtain the equivalent modulus of the supporting conglomerate according to the concepts of cementing the gap filler, dispersing the gap filler to fill pores and replacing a neutral framework by a structural gap filler;
s4, calculating the equivalent modulus of the unsupported conglomerate obtained in the step S2;
for the non-support conglomerate, discontinuously, unevenly and randomly filling medium gravels into the gap filler by utilizing a differential equivalent medium model, and calculating to obtain the equivalent modulus of the non-support conglomerate;
s5, calculating the sound velocity of the supporting conglomerate and the non-supporting conglomerate;
for the gap filler, taking gravel and sand in the gap filler as a skeleton, taking clay as a cementing material, taking the porosity of the gap filler as the existing porosity of the gap filler, and calculating to obtain the equivalent modulus of the gap filler based on an expanded second-stage contact cementing theory;
and substituting the obtained filler equivalent modulus into the supported conglomerate equivalent modulus obtained in the step S3 and the non-supported conglomerate equivalent modulus obtained in the step S4, and calculating to obtain the sound velocity of the supported conglomerate and the non-supported conglomerate.
3. The sound speed calculation method according to claim 2, wherein the medium gravel has a particle size > 2mm in step S1; the filler is fine sand and silt with the grain diameter less than or equal to 2 mm.
4. The sound speed calculation method according to claim 2, wherein a method of determining the distribution of the filler in step S3, specifically;
according to the identification result of the supporting conglomerate sample slice, dividing the gap filler into:
cementing the gap filler: the gap filler is distributed between the medium gravel and the medium gravel framework and mainly plays a role in cementing;
and (3) gap filler dispersion: the filler is distributed in the holes among the gravels and mainly plays a role in filling the holes;
structural filler: the filler is distributed in the gravel skeleton and mainly plays a role of replacing the skeleton.
5. The method of calculating the speed of sound according to claim 2, wherein the equivalent modulus of the supporting conglomerate in step S3 includes an equivalent bulk modulus KeffAnd equivalent shear modulus Geff；
The equivalent bulk modulus KeffThe calculation formula of (2) is as follows:
the equivalent shear modulus GeffThe calculation formula of (2) is as follows:
in the formula (I), the compound is shown in the specification,
Keffand GeffRespectively equivalent bulk modulus and equivalent shear modulus of the supporting conglomerate under specific porosity;
Φ is the total porosity of the conglomerate, also known as the existing porosity; phi1Porosity between gravels;
KCCTDEMand GCCTDEMRespectively calculating an equivalent volume modulus and a shear modulus obtained by using an expanded first-stage CCT model and a DEM model;
Ksand GsThe volume modulus of the equivalent skeleton of the medium gravel and the shear modulus of the structural filler are respectively obtained through calculation of a Voigt-reus-Hill model.
6. The sound speed calculation method according to claim 5, characterized in that the K isCCTDEMAnd GCCTDEMThe specific calculation method comprises the following steps:
the differential equivalent medium theory is utilized to carry out skeleton replacement, and the equivalent volume modulus K after the structural filler replaces the medium gravel skeleton is calculatedCCTDEMAnd equivalent shear modulus GCCTDEMThe calculation formula is as follows:
in the formula, K*＝KCCTDEM；μ*＝GCCTDEM；
K*(0)＝K1，μ*(0)＝μ1As an initial condition for the coupled differential equation, K1And mu1Respectively, the bulk modulus and shear modulus of the background medium, in particular, K1 is the bulk modulus K of the first phasecct、μ1Shear modulus G as first phasecct；
K2And mu2Respectively, the bulk modulus and shear modulus of the gradually added inclusions, in particular, the bulk modulus K of the second phase structure intersticecct2And shear modulus mucct2；
y is the volume fraction of the second phase, i.e., the volume fraction of structural interstitials;
p and Q are geometric factors used to characterize the filler geometry, assuming an aspect ratio of 1.0 for structural shims that replace pebbles as the skeleton;
the superscript 2 of P and Q means that the geometric factor is for having an equivalent modulusQuantity K*And mu*The background medium of (1).
7. The sound speed calculation method according to claim 6, characterized in that the K iscctAnd GcctThe calculation method comprises the following steps:
for supporting the conglomerate, firstly, the cementing action of the medium gravel framework and the cementing filler is considered, and the equivalent framework bulk modulus K after the medium gravel is cemented by the cementing filler is calculated by utilizing the expanded first-stage continuous cementation theorycctAnd equivalent skeleton shear modulus GcctThe specific calculation formula is as follows:
cement distribution mode 1:
cement distribution mode 2:
in the formula, alpha1For consolidating plane radius and median particle radiusThe ratio, i.e. the normalized bond radius;
ε is the ratio of the center thickness of the cement to the radius of the particles, i.e., the normalized center thickness of the cement;
Φ0critical porosity for the supporting conglomerate;
Φ is the total porosity of the supporting conglomerate;
Gcand G is the shear modulus of the cement interstice and the gravel skeleton particles, respectively;
Gc＝μcct2，G＝μC；
vcand v is the poisson's ratio of the cementitious filler and the gravel skeleton particles, respectively;
cement distribution mode 1 is a case where the cement content is distributed only between particles;
cement distribution mode 2 is the case when the cement content is uniformly distributed on the particle surface.
8. The method of calculating the speed of sound according to claim 1, wherein the equivalent modulus of unsupported conglomerate in step S3 includes an equivalent bulk modulus Keff2And equivalent shear modulus Geff2；
The calculation formula of the equivalent modulus of the non-support conglomerate is as follows:
in the formula (I), the compound is shown in the specification,
K*(0)＝Kcct2，μ*(0)＝μcct2as initial conditions for coupled differential equations, where Kcct2，μcct2Calculating the equivalent bulk modulus and the equivalent shear modulus of the background medium by using a second-stage expanded CCT model;
KC，μCfor gradual addition of medium-gravel inclusionsEquivalent bulk modulus K ofeff2And equivalent shear modulus Geff2；
VCThe content of medium gravel;
p and Q are geometric factors used to characterize the inclusion geometry;
the superscript 2 of P and Q refers to the inclusion of geometric factors in the background medium with equivalent moduli K and μ.
9. The method of calculating a sound speed according to claim 1, wherein the filler equivalent modulus in step S5 is calculated by:
considering the grit and the middlings in the caulk as the quartz skeleton, the clay as the cement, and the porosity of the caulk as the existing porosity of the caulk itself; and assuming that the framework of the initially cemented argillaceous sandstone is of porosity phi0Equivalent spherical particles with 0.36 and an average coordination number C ═ 9 are closely randomly aligned;
and calculating to obtain the equivalent bulk modulus Kcct2 and the equivalent shear modulus μ CCT2 of the gap filler by adopting a second-stage expanded CCT model.
10. Use of a method of calculating the speed of sound according to any one of claims 1 to 9 in forward prediction of supported and unsupported conglomerate speeds of sound or seismic and well logging inversion estimation of the porosity of supported and unsupported conglomerates.
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| US20190011584A1 (en) * | 2017-07-05 | 2019-01-10 | Petrochina Company Limited | Method and apparatus for identifying low permeable conglomerate diagenetic trap |
| CN112987096A (en) * | 2021-03-15 | 2021-06-18 | 中国石油大学(华东) | Method for calculating sound velocity of high-argillaceous sandstone |
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| CN107315050A (en) * | 2016-04-26 | 2017-11-03 | 中国石油化工股份有限公司 | Based on multi-component sand-conglomerate body velocity reconstruction method |
| US20190011584A1 (en) * | 2017-07-05 | 2019-01-10 | Petrochina Company Limited | Method and apparatus for identifying low permeable conglomerate diagenetic trap |
| CN112987096A (en) * | 2021-03-15 | 2021-06-18 | 中国石油大学(华东) | Method for calculating sound velocity of high-argillaceous sandstone |
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