A sand body configuration description method based on seismic wave trough and wave crest amplitude characteristics

Abstract

The application discloses a sand body configuration depiction method based on seismic wave trough and wave crest amplitude characteristics, which comprises the following steps: firstly, based on the existing research results of sedimentary microfacies, seven different order configuration interfaces are divided; according to single configuration unit and vertical combination sequence, eight types of configuration unit combinations are divided; based on sandstone ratio, GR curve dentification degree and physical property characteristics, the configuration unit combinations are divided into three categories; then, wave trough and wave crest seismic attribute characteristic parameters are optimized to analyze the seismic response differences of the three categories of configuration unit combinations, construct seismic response modes of different configurations, and determine the plane distribution characteristics of wave trough and wave crest ratio; the size of seismic root mean square amplitude and the size of wave trough and wave crest ratio are comprehensively considered to establish seismic identification standards of the three categories of configuration unit combinations; finally, the plane distribution prediction of the sand body configuration is completed based on the geological and seismic response characteristics. The application constructs the geological and seismic response identification standards of different configurations, and carries out quantitative prediction of the sand body configuration.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas exploration, and particularly relates to a sand body configuration description method based on seismic wave trough and wave peak amplitude characteristics. BACKGROUND

[0002] As unconventional gas reservoirs, tight sandstone gas has huge resource prospects worldwide. The total reserves and annual total production of tight sandstone gas fields in China have accounted for about 1 / 3 and 1 / 4 of the total reserves and annual total production of natural gas in China respectively, and have become the most important and realistic source for replacing conventional oil and gas resources in the next ten to twenty years.

[0003] At present, a large amount of research work has been carried out on sand body configuration, but the research is basically carried out by using the traditional configuration research idea, mainly based on sedimentary microfacies, different order single sand body configuration units are divided, and the size, shape, direction and superimposed relationship of the configuration unit are analyzed. With the continuous advancement of tight gas reservoir exploration and development, the scale of the rich and high-yield area of the research area is limited, the single well production and reserves of the same set of channel sand bodies are quite different, and the sand body configuration distribution prediction research is mainly carried out from the qualitative-semiquantitative angle based on the geological response characteristics. The sand body configuration is not quantitatively described in combination with the seismic response characteristics, and the well site deployment work in the later exploration and development process cannot be well guided.

[0004] The existing patent CN201910793343.0 discloses a sand body configuration quantitative analysis method, which mainly identifies the cycle interface of the research area, determines the sand body configuration interface according to the cycle interface, analyzes the sand body configuration interface, obtains the single well sand body configuration elements and contact relationship, combines the single well sand body configuration elements and contact relationship, obtains the longitudinal sand body splicing relationship, predicts the transverse sand body splicing relationship according to the longitudinal sand body splicing relationship, and obtains the sand body plane distribution map according to the longitudinal sand body splicing relationship and the transverse sand body splicing relationship. The sand body shape and size are finely described by using the Monte Carlo simulation numerical simulation method. However, the existing patent uses the traditional configuration research idea to carry out related research, mainly based on sedimentary microfacies, different order single sand body configuration units are divided, and the size, shape, direction and superimposed relationship of the configuration unit are analyzed. The shape and size of the sand body have not been described in combination with the seismic response characteristics. SUMMARY

[0005] The main purpose of the present application is to solve the problem that the shape and size of the sand body are not described in combination with the seismic response characteristics in the prior art.

[0006] To achieve the above purpose, the present application provides a sand body configuration description method based on seismic wave trough and wave peak amplitude characteristics, which comprises:

[0007] S1, based on the existing research results of sedimentary microfacies, the study area is divided into 8 types of configuration unit combination geological response characteristics, and the three types of configuration unit combination of the study area are clear;

[0008] S2, based on the wave trough, wave peak seismic attribute characteristic parameters to analyze the three types of configuration unit combination of the seismic response difference, the three types of configuration unit combination of the seismic response mode is constructed;

[0009] S3, based on the seismic response characteristic analysis and mode construction, according to the size of the seismic root mean square amplitude and the size of the wave trough P2 / wave peak P3 ratio, the difference of the three types of configuration unit combination of the seismic response is clear, so as to determine the seismic response identification standard of the three types of configuration combination unit;

[0010] S4, through the single well point sand body configuration geological response characteristic analysis, combining with the root mean square amplitude and the wave trough / wave peak ratio of the seismic response identification standard of different configuration sand body, the sand body configuration plane distribution prediction is completed.

[0011] Further, step S1 specifically includes:

[0012] S11, based on the traditional configuration interface classification scheme, the 7-level configuration interface in the study area is clear; the internal structure of the single channel under the 7-level configuration interface is described, based on the existing research understanding of sedimentary microfacies, the development of 6 types of 5-level single configuration unit of the target sand group single sand body in the study area is clear;

[0013] S12, according to the single configuration unit and its vertical combination sequence, 8 types of configuration unit combination are clear;

[0014] S13, based on the geological and geometric parameter range of different configuration unit combination, and according to the sand ratio, the degree of GR curve dentification and physical property characteristics, the 8 types of configuration unit combination are divided into three categories.

[0015] Further, the 7-level configuration interface in step S11 is: laminated, micro bottom shape, medium bottom shape, large bottom shape, large bottom shape, single channel and composite channel.

[0016] Further, the vertical combination sequence in step S12 is to identify the 5-level single configuration unit by sand body thickness, porosity and sedimentary microfacies characteristics, and analyze the combination characteristics of the 5-level single configuration unit in the vertical direction, so as to clear the vertical combination sequence.

[0017] Further, the 8 types of configuration unit combination in step S12 are: main channel sand+main channel sand, secondary channel sand+secondary channel sand, main channel sand+estuary dam sand, secondary channel sand+estuary dam sand, main channel sand+crevasse splay+natural levee, secondary channel sand+abandoned channel+crevasse splay+natural levee, estuary dam sand+secondary channel sand+abandoned channel, secondary channel sand+abandoned channel.

[0018] Further, the specific implementation in step S13 is:

[0019] The geological and geometric parameters of different configuration unit combinations are analyzed by clustering using SPSS, and cross-plot charts are drawn two by two to obtain the range of geological and geometric parameters of different configuration unit combinations, and the eight types of configuration unit combinations are further divided into three categories according to the sandstone ratio, the degree of GR curve dentification, and the physical property difference.

[0020] Further, the three categories of configuration combination units are: the sandstone ratio of the A type configuration is between 0.34 and 0.63, the dentification rate is less than 12%, and the porosity is between 9% and 11%; the sandstone ratio of the B type configuration is between 0.36 and 0.41, the dentification rate is between 12% and 15%, and the porosity is between 7% and 9%; and the sandstone ratio of the C type configuration is between 0.11 and 0.24, the dentification rate is greater than 15%, and the porosity is between 3% and 6%.

[0021] Further, step S2 specifically includes:

[0022] S21, taking the wave trough and wave peak response parameters as the basis for identifying different sand body types;

[0023] S22, based on the wave trough P2 and wave peak P3 seismic response parameters, constructing the seismic response mode of the three categories of configuration unit combinations.

[0024] Further, the seismic response mode of the three categories of configuration unit combinations in step S22 is specifically: the A type is wide wave trough and strong reflection, P2≥P3; the B type is medium-weak wave trough and medium-weak wave peak reflection, P2≤P3; and the C type is strong wave peak reflection, P2<P3.

[0025] Further, the seismic response identification standard of the three categories of configuration combination units in step S3 is: the A type wave peak is less than the wave trough, strong amplitude, and the wave trough / wave peak ratio is between 1 and 2; the B type wave peak is greater than the wave trough, medium amplitude, and the wave trough / wave peak ratio is between 0 and 1; and the C type wave peak is greater than the wave trough, strong amplitude, and the wave trough / wave peak ratio is between 0 and 1.

[0026] Beneficial effects:

[0027] The application provides a sand body configuration description technology based on seismic wave trough and wave crest amplitude characteristics, and can more efficiently and accurately evaluate the sand body configuration. In the prior art, the sand body configuration distribution prediction research is mainly carried out based on geological response characteristics from the qualitative-semiquantitative angle, and the sand body configuration quantitative description is not combined with the seismic response characteristics, and the well site deployment work in the later exploration and development process cannot be well guided. The patent mainly combines the seismic response characteristics such as the seismic wave trough and wave crest amplitude based on the geological response characteristics, constructs the geological-seismic response identification standard of different configurations, and carries out the quantitative prediction of the sand body configuration, which not only provides a theoretical basis for the prediction of the sand body configuration, but also has important guiding significance for the next exploration and development of the tight sand gas. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flow chart of the sand body configuration description method provided by the application;

[0029] Figure 2 is a five-level configuration unit feature chart provided by the application;

[0030] Figure 3 is a seismic response mode of different types of sand bodies provided by the application;

[0031] Figure 4 is a J3 seismic reflection single well profile provided by the application;

[0032] Figure 5 is a T1 well seismic reflection single well profile provided by the application;

[0033] Figure 6 is a X1 well single well seismic profile provided by the application;

[0034] Figure 7 is a seismic response characteristic and mode chart of different configurations provided by the application;

[0035] Figure 8 is a wave trough and wave crest amplitude crossplot chart of different configurations provided by the application;

[0036] Figure 9 is a wave trough / wave crest ratio stock price chart of different configurations provided by the application;

[0037] Figure 10 is a TF gas field Shaximiao Formation No. 1 sand group channel wave trough / wave crest plane distribution chart provided by the application;

[0038] Figure 11 is a TF gas field Shaximiao Formation No. 2 sand group channel wave trough / wave crest plane distribution chart provided by the application;

[0039] Figure 12 is a sand body configuration plane distribution chart of the TF gas field Shaximiao Formation No. 1 sand group provided by the application;

[0040] Figure 13 is a sand body configuration planar distribution map of No. 2 sand group of Shaximiao group of TF gas field provided by the application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0042] The application principle of the application is further described below in combination with the drawings and specific examples.

[0043] Example 1

[0044] The present study takes the channel sandstone of Shaximiao group of TF gas field as the object, and carries out the sand body configuration research by means of well-seismic combination. The specific research idea is referred to Figure 1 . Firstly, based on the existing research results of sedimentary microfacies, 7 different level configuration interfaces are divided; according to the vertical combination sequence of single configuration unit, 8 types of configuration unit combinations are divided, and based on the sand ratio, the degree of GR curve dentification and the physical property characteristics, the configuration unit combination is divided into three categories; then the wave trough and wave peak seismic attribute characteristic parameters are optimized to analyze the seismic response difference of the three categories of configuration unit combinations, the seismic response mode of different configurations is constructed, and the wave trough and wave peak ratio planar distribution characteristics of Shaximiao group of TF gas field are determined, the seismic identification standard of three categories of configuration unit combinations is established by comprehensively considering the size of seismic root mean square amplitude and the size of wave trough and wave peak ratio; finally, the planar distribution prediction of sand body configuration is completed based on the geological-seismic response characteristics.

[0045] S1, based on the geological response characteristics of 8 types of configuration unit combinations, the research area is divided into three categories of configuration unit combinations.

[0046] Based on the traditional configuration interface classification scheme, it is clear that 7 levels of configuration interfaces are mainly developed in the study area, which are laminations, micro bottom shapes (wave marks, internal accretion bodies of dunes), medium bottom shapes (dunes), internal accretion bodies of large bottom shapes (lateral accretion bodies), large bottom shapes (point bars, crevasse splay, natural levee), single channel and composite channel. This study mainly describes the internal structure of single channel under 7 levels of configuration interfaces. Based on the existing research understanding of sedimentary microfacies, it is determined that 6 types of 5 levels of single configuration units are developed in the single sand body of the target sand group in the study area. The 6 types are main channel sand, secondary channel sand, river mouth bar sand, crevasse splay sand, natural levee and abandoned channel. Among them, the well logging curve shape of the main channel sand is high amplitude box type, the single sand body thickness is between 9.87m~36.88m, the porosity (POR) is between 11%~14%, and the permeability (PERM) is between 0.64×10 -3 μm 24.57×10 -3 μm 2 ; the secondary channel sand logging curve shape is high amplitude clock, single sand body thickness is between 8.40m~48.84m, porosity is between 9%~12%, permeability is between 0.42×10 -3 μm 2 ~2.00×10 -3 μm 2 ; the estuary dam sand logging curve shape is medium-high amplitude funnel, single sand body thickness is between 5.16m~9.10m, porosity is between 9%~12%, permeability is between 0.03×10 -3 μm 2 ~1.10×10 -3 μm 2 ; the cutoff fan sand logging curve shape is medium amplitude finger, single sand body thickness is between 2.10m~8.28m, porosity is between 3%~5%, permeability is between 0.018×10 -3 μm 2 ~0.384×10 -3 μm 2 ; the natural dam logging curve shape is medium-low amplitude finger, single sand body thickness is between 3.68m~8.75m, porosity is between 5%~8%, permeability is between 0.001×10 -3 μm 2 ~0.231×10 -3 μm 2 ; the abandoned channel logging curve shape is low amplitude sawtooth, single sand body thickness is between 2.94m~9.76m, porosity is between 5%~8%, permeability is between 0.023×10 -3 μm 2 ~0.382×10 -3 μm 2 ; and the geological characteristics of different configuration units are determined Figure 2 .

[0047] According to single configuration unit and vertical combination sequence, 8 types of configuration unit combinations are determined, including main channel sand+main channel sand, secondary channel sand+secondary channel sand, main channel sand+estuary dam sand, secondary channel sand+estuary dam sand, main channel sand+cutoff fan+natural dam, secondary channel sand+abandoned channel+cutoff fan+natural dam, estuary dam sand+secondary channel sand+abandoned channel, secondary channel sand+abandoned channel. The vertical combination sequence is mainly identified by sand body thickness, porosity, sedimentary microfacies characteristics and other 5-level configuration units of single well, and the combination characteristics of 5-level configuration units in single well are analyzed, so that the vertical combination sequence is determined.

[0048] The geological and geometric parameters of different configuration unit combinations are analyzed by using SPSS, and the intersection chart is drawn between each other, the range of geological and geometric parameters of different configuration unit combinations is obtained, and according to the sandstone ratio, the degree of GR curve dentification and the physical property difference, the eight types of configuration unit combinations are further divided into three types of configuration combination units. The sandstone ratio of the A type configuration is between 0.34 and 0.63, the dentification rate is less than 12%, and the porosity is between 9% and 11%; the sandstone ratio of the B type configuration is between 0.36 and 0.41, the dentification rate is between 12% and 15%, and the porosity is between 7% and 9%; the sandstone ratio of the C type configuration is between 0.11 and 0.24, the dentification rate is greater than 15%, and the porosity is between 3% and 6%.

[0049] S2, based on the wave trough and wave peak seismic attribute characteristic parameters, the seismic response difference of the three types of configuration unit combinations is analyzed, and the seismic response mode of different configurations is constructed.

[0050] S21, the wave trough and wave peak response parameters are preferred as the basis for identifying different sand body types

[0051] According to the difference between the sand body and different lithology on the seismic reflection profile, the high porosity thick layer sandstone presents a top negative reflection and a symmetrical wave shape; the mudstone with high porosity sandstone presents a top positive reflection and a symmetrical wave shape; the mudstone with high speed layer is h<λ / 4, the top and bottom surfaces have opposite polarities, a differential wave shape, and a right downward symmetrical wave shape; the mudstone with dense sandstone is a high speed layer, the top surface has opposite polarity, a differential wave shape, and a left downward symmetrical wave shape; the transition layer is a transition type with a sudden change in the bottom surface and a decrease in the upward velocity, h<λ / 2, and an integral wave shape; the thin interbedded layer is a transition type with a sudden change in the top surface and an increase in the upward velocity, h<λ / 2, and an integral wave shape; wherein h is the thickness of the sand body, and λ is the wavelength. The present technology mainly researches the seismic reflection wave shape of the mudstone with high speed sandstone and the mudstone with high speed layer. The determination method of the seismic reflection wave shape is: when the double travel time interval of two reflection interfaces is greater than the length of a wavelet, the reflection waves of the two interfaces are not interfered and can be completely separated; when the double travel time interval is less than the length of a wavelet, interference will occur, forming a compound wave. When the wavelength is greater than λ / 4, no superposition occurs, and when the wavelength is less than λ / 4, the wave shape is superimposed, and with the thickness being smaller, the interference causes the top and bottom reflections to be offset, and the amplitude gradually weakens.

[0052] The wave impedance structure is mainly established by macro layer division method. The macro layer is a layer or layer series with approximately the same wave impedance and plays a major role in seismic records. There is a significant difference in wave impedance between macro layers, and the internal wave impedance difference can be ignored. Among them, the high porosity and permeability in thick mudstone is the highlight of sandstone seismic response. The permeability sand layer has a lower overall velocity than mudstone, which is characterized as a low-velocity layer. The top surface is a negative reflection, and the bottom surface is a positive reflection. The wave peak and wave trough are obliquely symmetrical waveforms. The sand layer group has a good correspondence with the wave trough-wave peak (the top of the sand layer corresponds to the wave trough, and the bottom corresponds to the wave peak). A number of positive reflections are formed in the clock-shaped structure overlying the channel sand body, and the sidelobe wave trough of the reflection will interfere and superimpose on the sand body top wave trough, causing the strengthening of the wave trough Figure 3 wherein Figure 3 The background color represents mudstone).

[0053] Taking the Shaiximiao Formation single well in the study area as an example, the sidelobe wave trough of the overlying mudstone positive reflection interface superimposes on the sandstone top surface, strengthens the top wave trough, and the sidelobe wave trough of the underlying mudstone positive reflection interface superimposes on the bottom surface, weakens the bottom wave peak Figure 4 . The overlying mudstone and sandstone of T1 well have similar velocities, and the overall reflection amplitude is weak. The top and bottom reflection amplitudes are similar Figure 5 . The sidelobe peak of the overlying negative reflection superimposes on the sandstone top reflection of X1 well, strengthens the sandstone top wave peak, and the underlying positive reflection peak superimposes on the sandstone bottom reflection, weakens the sandstone bottom wave trough Figure 6 .

[0054] S22, Construction of seismic response mode of sand bodies with different configurations

[0055] Based on the above analysis, the wave trough (P2) and the wave peak (P3) are selected as the typical seismic response parameters for the quantitative prediction of sand body configuration in this study, and the seismic response modes of three types of configuration unit combinations are constructed. Type A is wide wave trough and strong reflection, with waveform P2≥P3; Type B is medium-weak wave trough and medium-weak wave peak reflection, with P2≤P3; Type C is strong wave peak reflection, with P2 Figure 7 .

[0056] S3, Establishment of seismic response identification criteria for three types of configuration unit combinations

[0057] Based on the above seismic response characteristic analysis and mode construction, based on statistical analysis, the seismic response characteristics of three types of different configurations are clustered. According to the size of the seismic root mean square amplitude and the ratio of wave trough (P2) to wave peak (P3), the differences in seismic response of three types of configuration unit combinations are further clarified. The wave peak of type A is smaller than the wave trough, the amplitude is strong, and the wave trough / wave peak ratio is between 1 and 2. The wave peak of type B is greater than the wave trough, the amplitude is medium, and the wave trough / wave peak ratio is between 0 and 1. The wave peak of type C is greater than the wave trough, the amplitude is strong, and the wave trough / wave peak ratio is between 0 and 1 Figures 8-11 .

[0058] S4, based on the geological-seismic response characteristics, the sand body configuration plane distribution prediction is completed.

[0059] Through the single well point sand body configuration geological response characteristic analysis, combining the different configuration sand body's root mean square amplitude and wave trough / peak ratio and other seismic quantitative identification standards, the sand body configuration distribution prediction of Shaximiao group in the research area is completed Figure 12 and Figure 13 , and the well-seismic identification coincidence rate reaches 94%.

[0060] Based on the above sand body configuration plane distribution prediction, the prediction results of J1 well and J2 well in the research area are verified, wherein the sand ratio of J1 well is 0.52, the dentification rate of GR curve is 8%, the porosity is 10%, the wave trough and peak ratio is 1.65; the sand ratio of J2 well is 0.61, the dentification rate of GR curve is 3%, the porosity is 11%, the wave trough and peak ratio is 1.72, after verification, the sand body configuration type of the two wells is A type, and the sand body configuration prediction result is reliable.

[0061] The above only for the preferred embodiment of the present application, and not to limit the present application, any modification, equivalent replacement and improvement within the spirit and principles of the present application, etc., should be included in the protection scope of the present application.

Claims

1. A sand body configuration characterization method based on seismic wave trough, wave peak amplitude characteristics, characterized in that, The method comprises the following steps: S1, based on the existing research results of sedimentary microfacies, the research area is divided into 8 types of configuration unit combination geological response characteristics, and three types of configuration unit combination in the research area are determined; Among them, the three types of configuration unit combination are: the sand ratio of A type configuration is between 0.34-0.63, the dentification rate is less than 12%, and the porosity is between 9%-11%; the sand ratio of B type configuration is between 0.36-0.41, the dentification rate is between 12%-15%, and the porosity is between 7%-9%; the sand ratio of C type configuration is between 0.11-0.24, the dentification rate is greater than 15%, and the porosity is between 3%-6%; S2, based on the wave trough and wave peak seismic attribute characteristic parameters, the seismic response difference of the three types of configuration unit combination is analyzed, and the seismic response mode of the three types of configuration unit combination is constructed; Specifically, it comprises: S21, taking the wave trough and wave peak response parameters as the basis for identifying different sand body types; S22, based on the wave trough P2 and wave peak P3 seismic response parameters, the seismic response mode of the three types of configuration unit combination is constructed; The seismic response mode of the three types of configuration unit combination in step S22 is specifically: A type is wide wave trough strong reflection, waveform P2≥P3; B type is medium-weak wave trough and medium-weak wave peak reflection, P2≤P3; C type is strong wave peak reflection, P2 S3, based on the seismic response characteristic analysis and mode construction, according to the size of the seismic root mean square amplitude and the size of the wave trough P2 / wave peak P3 ratio, the seismic response difference of the three types of configuration unit combination is determined, so as to determine the seismic response identification standard of the three types of configuration unit combination; Among them, the seismic response identification standard of the three types of configuration unit combination is: the wave peak of A type is less than the wave trough, the amplitude is strong, and the wave trough / wave peak ratio is between 1-2; the wave peak of B type is greater than the wave trough, the amplitude is medium, and the wave trough / wave peak ratio is between 0-1; the wave peak of C type is greater than the wave trough, the amplitude is strong, and the wave trough / wave peak ratio is between 0-1; S4, through single well point sand body configuration geological response characteristic analysis, combined with the root mean square amplitude and the wave trough / wave peak ratio of the seismic response identification standard of different configurations, the sand body configuration plane distribution prediction is completed.

2. The method according to claim 1, wherein, Step S1 specifically comprises: S11, based on the traditional configuration interface classification scheme, the 7-level configuration interface in the research area is determined; and the internal structure of the single channel under the 7-level configuration interface is depicted, based on the existing research understanding of sedimentary microfacies, 6 types of 5-level single configuration units of the single sand body developed in the research area are determined; S12, according to the single configuration unit and its vertical combination sequence, 8 types of configuration unit combinations are determined; S13, based on the geological and geometric parameter range of different configuration unit combinations, and according to the sand ratio, the dentification degree of GR curve and the physical property characteristics, the 8 types of configuration unit combinations are divided into three types.

3. The method according to claim 2, wherein, The 7-level configuration interface in step S11 is: laminations, micro-forms, medium-forms, large-forms, large-forms, single channels and composite channels.

4. The method according to claim 2, wherein, The vertical combination sequence in step S12 is to identify the 5-level single configuration unit through sand body thickness, porosity and sedimentary microfacies characteristics, and analyze the combination characteristics of the 5-level single configuration unit in the vertical direction, so as to determine the vertical combination sequence.

5. The method according to claim 2, wherein, The combination of the eight types of configuration units in step S12 is specifically: main channel sand + main channel sand, secondary channel sand + secondary channel sand, main channel sand + estuary dam sand, secondary channel sand + estuary dam sand, main channel sand + crevasse splay + natural levee, secondary channel sand + abandoned channel + crevasse splay + natural levee, estuary dam sand + secondary channel sand + abandoned channel, and secondary channel sand + abandoned channel.

6. The method according to claim 2, wherein, The specific steps S13 include: The geological and geometric parameters of different configuration unit combinations are analyzed by using SPSS, and a cross plot is drawn between each two, so as to obtain the range of the geological and geometric parameters of different configuration unit combinations, and the eight types of configuration unit combinations are divided into three categories according to the sand ratio, the degree of GR curve dentation and the physical property difference.

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