Elastic properties of continental carbonates: From controlling factors to an applicable model for acoustic-velocity predictions

We have provided new insights into the controlling factors of elastic properties in continental carbonate rocks and introduced an applicable model for acoustic-velocity predictions in such a medium. Petrophysical properties (porosity, permeability, P- and S-wave velocities) from laboratory measurements have been coupled with thin-section observations and characterizations, and X-ray diffraction (XRD) analyses. A major achievement is the establishment of the link between the mineralogical composition and the P- and S-wave velocity dispersion at a given porosity. This reflects the subtle interplay between physicochemical and biological precipitation of continental carbonates, which can also be associated with a strong influence of detrital mineralogical inputs. The result is a mineralogical commixture, coupled to a wide array of pore types inherited from the strong ability of carbonate rocks to undergo diagenetic alteration. The proposed model takes into account the elastic moduli of the minerals, porosity, and pore shape, and it is based on the effective medium theory. We have considered the case in which the medium contained randomly oriented pores with different aspect ratios. Overall, the fit between the predicted trends and the experimental data is fairly good, especially for calcite and quartz matrix mineralogy. The results are even better when considering mineralogy inferred from XRD data, although in some case, and despite the aspect ratio variation in both simulations, the model fails to accurately predict the P-wave velocities. This probably means that another factor is at stake beside mineralogy. This can be explained by the limitation of the effective medium approach, which oversimplifies the reality and fails to account for the variability of some aspect ratio from one inclusion to another.

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Predicting acoustic-wave velocities and fluid sensitivity to elastic properties in fractured carbonate formation

Interpretation ◽

10.1190/int-2016-0067.1 ◽

2017 ◽

Vol 5 (1) ◽

pp. SB69-SB80 ◽

Cited By ~ 3

Author(s):

Jingjing Xu ◽

Maojin Tan ◽

Xiaochang Wang ◽

Chunping Wu

Keyword(s):

Elastic Properties ◽

Carbonate Rocks ◽

Seismic Inversion ◽

Carbonate Reservoir ◽

S Wave ◽

Mineral Concentration ◽

Fracture Porosity ◽

Wave Velocities ◽

Carbonate Formation ◽

Fractured Carbonate

Estimation of S-wave velocity is one of the most critical steps for prestack seismic inversion. Based on the petrophysical model of fractured carbonate rocks, theoretical methods are firstly investigated for estimating P- and S-wave velocities in the presence of fractures. Then, the methods of calculating elastic properties in fractured carbonate rocks are discussed. The mineral concentration, total porosity, and fracture porosity from core X-ray diffraction and routine core measurements or log interpretation results are used to estimate the P- and S-wave velocities. In the given carbonate rock model, the elastic properties of carbonate rocks with different porosity and fractures are calculated. Two field tests prove that the proposed new method is effective and accurate. Furthermore, the model is useful for fluid identification, which is one of the most outstanding problems for carbonate reservoir description. The simulation results suggest that the larger the fracture porosity is, the easier fluid typing. In Tahe Oilfield, the elastic properties of different fluid zones indicate that bulk modulus and Young’s modulus are more sensitive to fluid than shear modulus, the Lamé constant, and Poisson’s ratio.

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Prediction of Dynamic Elastic Properties for Mishrif formation in West Qurna-1 oil field: an experimental work

10.21203/rs.3.rs-1148988/v1 ◽

2021 ◽

Author(s):

ahmed wattan ◽

Mohammed AL‑Jawad

Keyword(s):

Young’S Modulus ◽

Elastic Properties ◽

Carbonate Rocks ◽

Young's Modulus ◽

Compressional Wave ◽

Oil Field ◽

S Wave ◽

Wave Velocities ◽

The Relationship ◽

Elastic Characteristics

Abstract Shear and compressional wave velocities are useful for drilling operations, the exploration of reservoirs, stimulation processes, and hydraulic fracturing. An ultrasonic device will be used in this investigation to anticipate and analyze the elastic characteristics of carbonate rocks. At the summit of the field, the well WQ1-20 obtained samples of the Mishrif formation from a variety of various depths. The number of samples taken from the well is nine from different units whereas the number of samples taken from the main unit (MB2) was five. The relations between the elastic properties for the carbonate rocks with P-and S-waves were defined. The relations between Vp and Vs with elastic properties were defined by applied Regression analysis. The results showed that a linear relationship between P-and S-wave velocities with the elastic properties of the carbonate rocks. It is found that the relationship between Vp and Young's modulus (E) is R2 equal to 0.979 while the relationship between Vs and Young's modulus (E) is R2 equal to 0.925. The relationship between shear modulus and Vs is good in comparison with Vp where the values of R2 were 0.985 and 0.94 respectively. R2 values for the Bulk modulus and Lame's constant of Vp are 0.925 and 0.6, respectively, while the values for Vs are 0.925 and 0.6 for the latter. The relation between Vp/Vs ratio with Poisson’s ratio showed a good R2 with a value of 0.97. When it comes to predicting the dynamic elastic characteristics of a material, the ultrasonic approach may be regarded as a cost-effective, easy, and non-destructive method.

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Effective medium modeling of diagenesis impact on the petroacoustic properties of carbonate rocks

Geophysics ◽

10.1190/geo2018-0559.1 ◽

2019 ◽

Vol 84 (4) ◽

pp. WA43-WA57 ◽

Cited By ~ 2

Author(s):

Mathilde Adelinet ◽

Jean-François Barthélémy ◽

Elisabeth Bemer ◽

Youri Hamon

Keyword(s):

Elastic Properties ◽

Carbonate Rocks ◽

Effective Medium ◽

Petrographic Analysis ◽

Permeability Evolution ◽

Data Set ◽

Microstructural Parameters ◽

Acoustic Signature ◽

Extensive Experimental Data ◽

The Impact

Carbonate formations are highly heterogeneous, and the velocity-porosity relationships are controlled by various microstructural parameters, such as the types of pores and their distribution. Because diagenesis is responsible for important changes in the microstructure of carbonate rocks, we have extended the standard effective medium approach to model the impact of diagenesis on the carbonate elastic properties through a step-by-step effective medium modeling. Two different carbonate rocks deposited, respectively, in lacustrine and marine environments are considered in this study. The first key step is the characterization of the diagenesis, which affected the two studied carbonate sample sets. Effective medium models integrating all of the geologic information accessible from petrographic analysis are then built. The evolution of the microstructural parameters during diagenesis is thoroughly constrained based on an extensive experimental data set, including X-ray diffraction analysis, different porosimetry methods, and ultrasonic velocity measurements. A new theoretical approach including two sources of compliance is developed to model the specific behavior of carbonates. A compliant interface is introduced around the main carbonate grains to represent grain contacts and the different pore scales are taken into account through multiscale modeling. Finally, direct calculations with the model provide elastic wave velocities representative of the different diagenetic stages. An extrapolation to permeability evolution is also introduced. This approach allows the identification of the acoustic signature of specific diagenetic events, such as dolomitization, dissolution, or cementation, and the assessment of their impact on the elastic properties of carbonates.

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Optimization of Rock Physics Models by Combining the Differential Effective Medium (DEM) and Adaptive Batzle-Wang Methods in “R” Field, East Java

Scientia Bruneiana ◽

10.46537/scibru.v17i2.78 ◽

2019 ◽

Vol 17 (2) ◽

Author(s):

M. Wahdanadi Haidar ◽

Reza Wardhana ◽

M. Iskan ◽

M. Syamsu Rosid

Keyword(s):

Elastic Modulus ◽

Wave Velocity ◽

Carbonate Rocks ◽

Effective Medium ◽

Carbonate Reservoir ◽

P Wave ◽

S Wave ◽

P Wave Velocity ◽

Reservoir Conditions ◽

Pore Types

The pore systems in carbonate reservoirs are more complex than the pore systems in clastic rocks. There are three types of pores in carbonate rocks: interparticle pores, stiff pores and cracks. The complexity of the pore types can lead to changes in the P-wave velocity by up to 40%, and carbonate reservoir characterization becomes difficult when the S-wave velocity is estimated using the dominant interparticle pore type only. In addition, the geometry of the pores affects the permeability of the reservoir. Therefore, when modelling the elastic modulus of the rock it is important to take into account the complexity of the pore types in carbonate rocks. The Differential Effective Medium (DEM) is a method for modelling the elastic modulus of the rock that takes into account the heterogeneity in the types of pores in carbonate rocks by adding pore-type inclusions little by little into the host material until the required proportion of the material is reached. In addition, the model is optimized by calculating the bulk modulus of the fluid filler porous rock under reservoir conditions using the Adaptive Batzle-Wang method. Once a fluid model has been constructed under reservoir conditions, the model is entered as input for the P-wave velocity model, which is then used to estimate the velocity of the S-wave and the proportion of primary and secondary pore types in the rock. Changes in the characteristics of the P-wave which are sensitive to the presence of fluid lead to improvements in the accuracy of the P-wave model, so the estimated S-wave velocity and the calculated ratio of primary and secondary pores in the reservoir are more reliable.

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Using laboratory data to understand how pore aspect ratio influences elastic parameters and AVO

Geophysics ◽

10.1190/geo2020-0454.1 ◽

2021 ◽

pp. 1-50

Author(s):

Kamal Moravej ◽

Alison Malcolm

Keyword(s):

Aspect Ratio ◽

Elastic Properties ◽

Wave Velocity ◽

Selective Laser Sintering ◽

Laboratory Data ◽

Physical Models ◽

P Wave ◽

S Wave ◽

Water Saturated ◽

The Impact

Pore geometry is an important parameter in reservoir characterization that affects the permeability of reservoirs and can also be a controlling factor on the impact of pressure and saturation on reservoirs elastic properties. We use SLS (Selective Laser Sintering) 3D printing technology to build physical models to experimentally investigate the impacts of pore aspect ratio on P-, and S- wave velocities and amplitude variation with offset (AVO). We printed six models to study the effects of the pore aspect ratio of prolate and oblate pore structures on elastic properties and AVO signatures. We find that the P-wave velocity is reduced by decreasing the pore aspect ratio (flatter pore structure), whereas the shear wave velocity is less sensitive to the pore aspect ratio. This effect is reduced when the samples are water saturated. We present new experimental and processing techniques to extract realistic AVO signatures from our experimental data and show that the pore aspect ratio has similar effects on AVO as fluid compressibility. This shows that not considering the pore aspect ratio in AVO analysis can lead to misleading interpretations. We further show that these effects are reduced in water-saturated samples.

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Elastic anisotropy of the Middle Bakken Formation

Geophysics ◽

10.1190/geo2014-0219.1 ◽

2015 ◽

Vol 80 (1) ◽

pp. D23-D29 ◽

Cited By ~ 8

Author(s):

Colin M. Sayers ◽

Sagnik Dasgupta

Keyword(s):

Aspect Ratio ◽

Elastic Anisotropy ◽

Organic Content ◽

Bakken Formation ◽

S Wave ◽

Low Aspect Ratio ◽

Wave Velocities ◽

Porosity And Permeability ◽

Seismic Measurements ◽

High Organic Content

The Bakken Formation consists of three members: The Upper Bakken and Lower Bakken are dark marine shales with high organic content, whereas the Middle Bakken consists of mixed carbonates and clastics and is the main reservoir unit, despite having low porosity and permeability. Dipole S-wave data acquired in a lateral well in the Middle Bakken Formation revealed this formation to be anisotropic. Backus upscaling of logs acquired in a nearby vertical pilot well in the same layers sampled by the lateral well gave estimates of the anisotropy that were too small to explain the S-wave anisotropy measured in the lateral well. The observed anisotropy was interpreted in terms of bedding-parallel compliant discontinuities such as microcracks and low-aspect-ratio pores. The presence of bedding-parallel microcracks and low-aspect-ratio pores may contribute to the permeability of the tight Middle Bakken reservoir, and the sensitivity of P- and S-wave velocities to the presence of microcracks and low aspect ratio pores suggested the use of sonic and seismic measurements for identifying the productive zones in the low-permeability Middle Bakken reservoir.

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Measuring ultrasonic characterisation to determine the impact of TOC and the stress field on shale gas anisotropy

The APPEA Journal ◽

10.1071/aj12021 ◽

2013 ◽

Vol 53 (1) ◽

pp. 245 ◽

Cited By ~ 3

Author(s):

Yazeed Altowairqi ◽

Reza Rezaee ◽

Milovan Urosevic ◽

Claudio Delle Piane

Keyword(s):

Elastic Properties ◽

Shale Gas ◽

Ultrasonic Transducers ◽

S Wave ◽

Gas Reservoirs ◽

Wave Velocities ◽

Degree Of Anisotropy ◽

The Impact ◽

The Relationship ◽

Dynamic Elastic Properties

While the majority of natural gas is produced from conventional sources, there is significant growth from unconventional sources, including shale-gas reservoirs. To produce gas economically, candidate shale typically requires a range of characteristics, including a relatively high total organic carbon (TOC) content, and it must be gas mature. Mechanical and dynamic elastic properties are also important shale characteristics that are not well understood as there have been a limited number of investigations of well-preserved samples. In this study, the elastic properties of shale samples are determined by measuring wave velocities. An array of ultrasonic transducers are used to measure five independent wave velocities, which are used to calculate the elastic properties of the shale. The results indicated that for the shale examined in this research, P- and S-wave velocities vary depending on the isotropic stress conditions with respect to the fabric and TOC content. It was shown that the isotropic stress significantly impacts velocity. In addition, S-wave anisotropy was significantly affected by increasing stress anisotropy. Stress orientation, with respect to fabric orientation, was found to be an important influence on the degree of anisotropy of the dynamic elastic properties in the shale. Furthermore, the relationship between acoustic impedance (AI) and TOC was established for all the samples.

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Predicting subsurface CO2 movement: From laboratory to field scale

Geophysics ◽

10.1190/geo2011-0224.1 ◽

2012 ◽

Vol 77 (3) ◽

pp. M27-M37 ◽

Cited By ~ 17

Author(s):

Ranjana Ghosh ◽

Mrinal K. Sen

Keyword(s):

Elastic Properties ◽

Carbonate Rocks ◽

Water Saturation ◽

Time Lapse ◽

Carbonate Reservoir ◽

S Wave ◽

Permeability Enhancement ◽

Proposed Model ◽

Porosity And Permeability ◽

Frequency Dependent Model

Finding an appropriate model for time-lapse seismic monitoring of [Formula: see text]-sequestered carbonate reservoir poses a great challenge because carbonate-rocks have varying textures and highly reactive rock-fluid system. We introduced a frequency-dependent model based on Eshelby’s inclusion and differential effective medium (DEM) theory that can account for heterogeneity in microstructure of rocks and squirt flow. We showed that the estimated velocities from the modified DEM theory match well with the laboratory measurements (ultrasonic) of velocities of carbonate rocks saturated with [Formula: see text]-rich water. The theory predicts significant decrease in saturated P- and S-wave velocities in the seismic frequency band as a consequence of porosity and permeability enhancement by the process of chemical dissolution of carbonates with the saturating fluid. The study also showed the combined effect of chemical reaction and free [Formula: see text] saturation on the elastic properties of rock. We observed that the velocity dispersion and attenuation increased from complete gas saturation to water saturation. The proposed model can be used to invert geophysical measurements to detect changes in elastic properties of a carbonate reservoir and interpret the extent of [Formula: see text] movement with time. These are the key elements to ensure that sequestration will not damage underground geologic formation and [Formula: see text] storage is secure and environmentally acceptable.

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Improved granular medium model for unconsolidated sands using coordination number, porosity, and pressure relations

Geophysics ◽

10.1190/1.3333539 ◽

2010 ◽

Vol 75 (2) ◽

pp. E91-E99 ◽

Cited By ~ 29

Author(s):

Tanima Dutta ◽

Gary Mavko ◽

Tapan Mukerji

Keyword(s):

Coordination Number ◽

Granular Media ◽

Effective Medium ◽

Unconsolidated Sediments ◽

Data Sets ◽

S Wave ◽

Unconsolidated Sands ◽

Wave Velocities ◽

Effective Medium Model ◽

Medium Model

We have developed a recipe for using closed-form expressions of effective-medium models to predict velocities in unconsolidated sandstones. The commonly used Hertz-Mindlin effective-medium model for granular media often predicts elastic wave velocities that are higher, and [Formula: see text] ratios that are lower, than those observed in laboratory and well log measurements in unconsolidated sediments. We use the extended Walton model, which introduces a parameter [Formula: see text] to represent the fraction of grain contacts that are perfectly adhered. Using the extended Walton model with [Formula: see text] ranging from 0.3 to 1, we obtain new empirical relations between the coordination number (C), porosity, and pressure for P- and S-wave velocities by inverting dynamic measurements on dry, unconsolidated sands. We propose using the extended Walton model [Formula: see text] along with these new C-porosity and C-pressure relations to study the mechanical compaction of unconsolidated sandstones. The model has been tested on two experimental data sets. It provides a reasonable fit to observed P- and S-wave velocities and specifically improves shear-wave predictions.

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STUDY OF ELASTIC PROPERTIES AS FUNCTION OF TEMPERATURE IN ANISOTROPIC CRACKED MEDIA: AN ULTRASONIC APPROACH

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v36i3.1955 ◽

2018 ◽

Vol 36 (3) ◽

pp. 1

Author(s):

José Jésus Silva Sobrinho ◽

José J. S. de Figueiredo ◽

Rafael L. Lima ◽

Léo Kirchhof Santos ◽

Murillo J. Nascimento

Keyword(s):

Elastic Properties ◽

Steam Injection ◽

Good Alternative ◽

Seismic Velocities ◽

S Wave ◽

Wave Velocities ◽

Heating And Cooling ◽

Secondary Cracks ◽

Anisotropy Parameters ◽

The Difference

ABSTRACT. The study of seismic wave velocities and their related anisotropy parameters provides important tools to the study of Earth’s subsurface. The analysis of temperature’s influence in the elastic properties of synthetic rocks, e.g., may be a good alternative for modelling the response of elastic properties of rocks surrounding deep wells and/or that are submitted to the process of steam injection. In order to understand the effects of temperature on the elastic parameters, in this work we constructed four porous synthetic sandstones, one representing an uncracked medium and three cracked samples. They were submitted to variable temperatures, while their elastic properties were calculated during heating and cooling processes. It was noted that P- and S-wave velocities decreased with increasing temperature. This behavior may be caused by changes in the background stiffness and by the generation of secondary cracks inside the samples. However, P- and S- anisotropy parameters were not affected by the changes in temperature. This can be an indicative that randomly distributed secondary cracks were created. Other indicative of secondary cracking formation can be associated to the difference between seismic velocities during the heating and cooling processes.Keywords: Cracked media, Anisotropy, Temperature dependence, Elastic parameters.RESUMO. O estudo das ondas sísmicas e de seus parâmetros anisotrópicos associados fornece ferramentas importantes para o estudo da subsuperfície da Terra. A análise da influência da temperatura nos parâmetros elásticos de rochas sintéticas, por exemplo, pode ser uma boa alternativa para modelar a resposta das propriedades elásticas de rochas circundando poços profundos e/ou que são submetidas a processos de injeção de vapor. Para entender os efeitos da temperatura nos parâmetros elásticos, neste trabalho construímos quatro arenitos sintéticos porosos, um representando um meio não-fissurado e três amostras fissuradas. As amostras foram submetidas a temperaturas variadas, enquanto suas propriedades elásticas foram calculadas ao longo dos processos de aquecimento e resfriamento. Notou-se que as velocidades das ondas P e S diminuíram com o aumento da temperatura. Esse comportamento talvez seja causado por variações na rigidez do background e pela formação de fissuras secundárias nas amostras. Entretanto, os parâmetros anisotrópicos P e S não foram afetados pelas mudanças de temperatura. Isso pode ser considerado um indicativo de que fissuras secundárias distribuídas aleatoriamente foram formadas. Outro indicador da formação de fissuras secundárias pode ser associado à diferença entre as velocidades sísmicas durante os processos de aquecimento e resfriamento.Palavras-chave: Meios fissurados, aniostropia, dependência de temperatura, parâmetros elásticos.

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