Estimating porosity and density of calcarenite rocks from P-wave velocity

Petrophysical proprieties such as porosity, density, saturation have a marked impact on acoustic proprieties of rocks. Hence, there has been recently a strong incentive to use new geophysical techniques to invert such properties from seismic or sonic measurements for rocks characterization. The P-wave velocity, is non-destructive and easy method to apply in both field and laboratory conditions, has increasingly been conducted to determine the geotechnical properties of rock materials. The P-wave velocity of a rock is closely related to the intact rock properties and measuring the velocity in rock masses describes the rock structure and texture. The present work deals with the use of simple and non destructive technique, ultrasonic velocity to predict the porosity and density of calcarenite rocks that is characteristic in historical monument. The ultrasonic test is based on measuring the propagation time of a P-wave in the longitudinal direction. Good correlations between P-wave velocity, porosity and density were found, which indicate them as appropriate technique for estimating the porosity and density

Spatial variation of coda wave attenuation in the AL Hoceima region (Earthquakes of 24 Frebruary 2004), Morocco

On 24th February 2004 a significant earthquake (Md = 6.4) occurred in the north of Morocco causing great damage in the vicinity of Al Hoceima region. This area is characterized by a complex faulting system as a result of compressional tectonic forces. Three short period stations are set in this area of interest and recordings from these stations were used in this study. In order to complete our knowledge of attenuation, 60 local earthquakes are recorded a few days after the great earthquake with magnitude Ml 2.6-5.0 to estimate seismic attenuation. For this purpose, we applied the single backscattering model of Aki & Chouet 1975 in the frequency range for 1 to 4 Hz. The study of coda waves was limited to a relatively short lapse time (10 Seconds) in order to sample the earth’s crust only .The values of Qc estimated for all the three stations show a strong frequency dependent relationship of the form Qc=Q0fn, where Q0 is Qc at 1Hz , and n represents the degree of frequency dependence , and reflect the level of crustal heterogeneities to varying degrees. The average frequency dependent attenuation relationship has been obtained which indicates that the attenuation is high in this region. Finally to conclude our work, the values of Q0 suggest that Al Hoceima area is highly heterogeneous and the n parameter indicates a meaning frequency dependence of Qc

Quality factor of seismic coda waves from earthquakes in northern Morocco

The main objective of this work is to analyze seismic attenuation (1/Qc) using a single backscattering model hypothesis of Aki and Chouet (1975). For this purpose, the recordings of 66 local earthquakes (epicentre distance < 100 km) during 2008 in Northern Morocco have been used with a magnitude (Ml ) less than 4. The Qc quality factor values have been computed at four central frequencies 0.75, 1.5, 3, 6 and 12 Hz and analyzed for two horizontal and vertical components for performing the average values. Four lapse time windows seconds from 30 to 60 duration with a difference of 10 seconds have been analyzed to study the lapse time dependence of Qc. We obtained a strong average frequency dependence follow a power law Qn=Q0fn where Q0 is Qc at 1Hz and n is the power of frequency dependent .The frequency dependent relationships obtained are Qc=(143.75±1.09)f(0.864±0.006) for the vertical component , Qc=(149.12±1.08)f(0.85±0.05) and  for the N component , and Qc=(140.42±1.81)f(0.902±0.04) for the E component. The values estimated of coda Q shows independent on the component of wave motion consistent with (Jen-Kuang Chung 2009 and Priyamvada Singh 2012 ), thus only one component sufficient to treat the attenuation in this region. The mean values of the estimated Qc of the vertical component vary from 76 (at 0.75) to 1147.6 (at 12 Hz) for 30  seconds coda window length, for 40 seconds coda window length Qc vary from 122.48 (at 0.75) to 1255 (at 12 Hz ) while for 50 seconds coda window length Qc vary from 141.4 (0.75) to 1420.8 (at 12 Hz ) . Similarly for 60 seconds coda window length Qc vary from 173.89 to 1495. The increase in Qc values with lapse time shows the depth dependence which agree with many studies. The results obtained with this model are presented and then compared to results from the literature

Permeability and porosity of rocks and their relationship based on laboratory measurements

Petrophysical properties of rocks were measured, and their relationships are discussed in this paper. Based on permeability and mercury intrusion porosimetry methods, porosity, and pore size distribution were determined. Furthermore, bulk and particle densities of rocks were determined. The morphology of the porous medium has been approached by mercury porosimetry gives an appearance of the pore distribution of the material. Permeability and porosity are in close relation, and it could be assumed that its relationship is linear, i.e., with increasing porosity, permeability increases as well. This relationship is influenced by other rock properties, such as the amount of open and closed pores within the rock sample, size, and distribution of pores. From this point of view, it is necessary to study these physical properties of rocks as well, because this enables an overall analysis of rocks and its possible use for geotechnical engineering

Porosity and mineralogy evolution during the decay process involved in the Chellah monument stones

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PETROPHYSICAL, PETROGRAPHICAL AND MINERALOGICAL CHARACTERIZATION OF CALCARENITE ROCK USED FOR MONUMENTAL BUILDING IN MOROCCO

International audienceThis article consists in studying the petrophysical, petrographical, mineralogical and structural properties implemented stones. Our study was conducted on one of the stones most commonly used in building monuments of coastal cities in Morocco, particularly in the Rabat-Sale region: the Plio-Quaternary calcarenite. This work is a first phase of a more overall study taking into account the severe conditions to which these building materials were subjected. At this level of advancement, no expertise can be conducted. A good knowledge of various calcarenite stone characteristics allows to better understanding the alteration mechanisms of this material and to consider solutions limiting their progress. So, we have also chosen to work on unaltered samples taken from the original quarry. Experimental analysis performed on sample fragments of unaltered calcarenite rock using the X-ray diffraction (XRD) and the Scanning Electron Microscopy (SEM) observations, allow characterizing the stone both from the mineralogical and the structural point of views. Moreover, the pore size distribution according to pressure-volume analysis has been established by using the mercury intrusion porosimetry method. We will also present petrophysical results concerning the imbibition kinetics, thermal conductivity and permeability for tests performed on specimens taken parallel and perpendicular to the sediment bedding

POROSITY, PERMEABILITY AND BULK DENSITY OF ROCKS AND THEIR RELATIONSHIPS BASED ON LABORATORY MEASUREMENTS

International audiencePhysical properties of rocks are measured and analyzed, and their relationships are discussed in this paper. Permeability and mercury porosimetty methods, porosity, and pore size distribution are determined. Furthermore, bulk and particle densities of rocks are determined. The morphology of the porous medium has been approached by mercury porosimetry which gives an appearance to the pore distribution of the material. The permeability of a variety of natural materials is characterized using a relatively new laboratory apparatus. Permeability and porosity are in close relation, and it could be assumed that its relationship is linear, Le., with increasing porosity, permeability increases as well. This relationship is influenced by other rock properties, such as the amount of open and closed pores within the rock sample, size, and distribution of pores. From this point of view, it is necessary to study these physical properties of natural materials as well, because this enables an overall analysis of rocks and their possible use for construction

Prediction of elastic and acoustic behaviors of calcarenite used for construction of historical monuments of Rabat, Morocco

Natural materials (e.g. rocks and soils) are porous media, whose microstructures present a wide diversity. They generally consist of a heterogeneous solid phase and a porous phase which may be fully or partially saturated with one or more fluids. The prediction of elastic and acoustic properties of porous materials is very important in many fields, such as physics of rocks, reservoir geophysics, civil engineering, construction field and study of the behavior of historical monuments. The aim of this work is to predict the elastic and acoustic behaviors of isotropic porous materials of a solid matrix containing dry, saturated and partially saturated spherical pores. For this, a homogenization technique based on the Mori–Tanaka model is presented to connect the elastic and acoustic properties to porosity and degree of water saturation. Non-destructive ultrasonic technique is used to determine the elastic properties from measurements of P-wave velocities. The results obtained show the influence of porosity and degree of water saturation on the effective properties. The various predictions of Mori–Tanaka model are then compared with experimental results for the elastic and acoustic properties of calcarenite

Prediction of Porosity and Density of Calcarenite Rocks from P-Wave Velocity Measurements

International audiencePetrophysical proprieties such as porosity, density, permeability and saturation have a marked impact on acoustic pro-prieties of rocks. Hence, there has been recently a strong incentive to use new geophysical techniques to invert such properties from seismic or sonic measurements for rocks characterization. The P-wave velocity, which is non-destruct-tive and easy method to apply in both field and laboratory conditions, has increasingly been conducted to determine the geotechnical properties of rock materials. The P-wave velocity of a rock is closely related to the intact rock properties, and been measuring the velocity in rock masses describes the rock structure and texture. The present work deals with the use of a simple and non-destructive technique, ultrasonic velocity, to predict the porosity and density of calcarenite rocks that are characteristic in historical monument. The ultrasonic test is based on measuring the propagation time of a P-wave in the longitudinal direction. Good correlations between P-wave velocity, porosity and density were found, which indicated them as an appropriate technique for estimating the porosity and density

Determination of Thermal Conductivity and Porosity of Building Stone from Ultrasonic Velocity Measurements

International audienceUltrasonic velocity measurement, a non-destructive and easy method to apply in both field and laboratory conditions, has increasingly been conducted to determine the physical properties of rock materials. This paper presents an experimental study of the measurement of P-wave velocity, thermal conductivity and porosity of several types of sedimentary, metamorphic, and magmatic rocks. The aim of this study is to predict the rocks properties including their thermal conductivity and porosity using P-wave velocity. For this purpose, the physical properties are determined in the laboratory to obtain correlations between P-wave velocity and physical properties. Consequently, good linear relationships are found between all the determined physical properties and the P-wave velocity measurements