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

Soft adsorption of densely packed layers of DNA-plasmid * 1,3-diaminopropane complexes onto highly oriented pyrolytic graphite designed to erode in water

International audienceIn this Article, we report a simple and effective method to build up self-assembled and well-calibrated layers of plasmid DNA*1,3-diaminopropane complexes onto highly oriented pyrolitic graphite (HOPG). The method is based on the self-assembly of the poly electrolytes onto HOPG in an excess of positively charged protonated diamines (Dap2+) in comparison to the negatively charged phosphate moieties of the DNA backbone in solution. Although short distortions in the helical parameters of DNA (maximum 12% hypochromicity) are revealed by UV-vis absorption spectrometry, the native B form of the plasmids is conserved. By fixing the excess of positive charges arising from Dap2+ cations, it is possible to construct assemblies of a well-defined thickness ranging typically from 1 monolayer (ML) of DNA to 10 ML; 1 ML has a thickness of 2.2 ± 0.5 nm. Adding TRIS-EDTA (TE) buffer lowers considerably the damage rate observed when plasmids are mixed with Dap2+ in pure water. The thickness of the first dense monolayer matches well the DNA cross-sectional dimensions, indicating that this layer is strongly anchored to the surface; it is insoluble in water. Conversely, thicker layers can be released in aqueous media, and the plasmids do not undergo dramatic damage. In the presence of TE buffer, condensation of the plasmids on the HOPG surface and a further release of the deposits in water yields a loss of supercoiling that ranges typically from 10% to 20% when the layer thickness varies from 22 to 12 nm. Such densely packed and releasable DNA plasmid layers with a very well-characterized and constant thickness constitute a substantial progress for biochemical and radiochemical experiments

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, 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

Relationships between porosity and permeability of calcarenite rocks based on laboratory measurements

International audienceFluid transport into porous materials is an area of study relevant to many scientific and engineering fields such as hydrogeology, geoenvironmental engineering, petroleum engineering, chemical engineering and physics. Permeability and porosity are two of the primary properties that control the movement and storage of fluids in rocks. They represent important characteristics of materials. In the present study, basic petrophysical properties of calcarenite rocks were measured, and their relationships are discussed.Permeability and mercury intrusion porosity ,and pore size distribution were determined. Furthermore, bulk and particle densities of rocks were determined. Permeability and porosity are closely related to each other in very good direct proportional relationship, 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, as well as pore size, and distribution. From this point of view, it is necessary to study these petrophysical properties of calcarenite rocks that are commonly used for historical monuments, because this enables an overall analysis of rocks and its possible use for engineering constructions and renovation of historical monuments

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

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