1,721,010 research outputs found
Temperature effects on acoustic measurements conducted on bitumen-saturated carbonate rocks of the Majella reservoir (Central Italy)
No full textPetrophysical properties variation of bitumen-bearing carbonates at increasing temperatures from laboratory to model
No full textVariations in reservoir seismic properties can be correlated to changes in saturated-fluid properties. Thus, the determination of variation in petrophysical properties of carbonate-bearing rocks is of interest to the oil exploration industry because unconventional oils, such as bitumen (HHC), are emerging as an alternative hydrocarbon reserve. We have investigated the temperature effects on laboratory seismic wave velocities of HHC-bearing carbonate rocks belonging to the Bolognano Formation (Majella Mountain, central Italy), which can be defined as a natural laboratory to study carbonate reservoir properties. We conduct an initial characterization in terms of porosity and density for the carbonate-bearing samples and then density and viscosity measurements for the residual HHC, extracted by HCl dissolution of the hosting rock. Acoustic wave velocities are recorded from ambient temperature to 90°C. Our acoustic velocity data point out an inverse relationship with temperature, and compressional (P) and shear (S) wave velocities show a distinct trend with increasing temperature depending on the amount of HHC content. Indeed, samples with the highest HHC content show a larger gradient of velocity changes in the temperature range of approximately 50°C-60°C, suggesting that the bitumen can be in a fluid state. Conversely, below approximately 50°C, the velocity gradient is lower because, at this temperature, bitumen can change its phase in a solid state. We also propose a theoretical model to predict the P-wave velocity change at different initial porosities for HHC-saturated samples suggesting that the velocity change mainly is related to the absolute volume of HHC
A Slip Tendency Analysis to Test Mechanical and Structural Control on Aftershock Rupture Planes. Riunione Annuale, Gruppo Nazionale Geofisica della Terra Solida
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The seismic signature of heavy oil on carbonate reservoir through laboratory experiments and AVA modelling
No full textThe influence of unconventional oil on the petrophysical properties of carbonate rocks is of primary interest in petroleum science. In this work, we first provided a thorough petrophysical characterization in laboratory by measuring density, porosity, VP and VS of a bitumen carbonate reservoir rock outcropping in the Majella Mountain (Central Italy). The presence of bitumen stiffens the rock and causes an increases of the acoustic impedance (AI) and a strong decrease of the VP/VS ratio respect to brine saturation. On the contrary, lighter oil causes a decrease of the AI and a slight decrease of the VP/VS ratio in comparison with a saturation in brine. Then, we performed a Synthetic Amplitude vs Angles (AVA) modelling showing that through the AVA ana- lysis, it is possible to recognize the type of fluid that saturates the analyzed carbonate reservoir rocks. We also observed that the increasing porosity plays a key role in the AVA response, by decreasing the bulk density and seismic waves velocities and increasing the amount of fluids that saturate the rocks. By applying our laboratory and modelling results to a public stacked seismic line we show that our results may help in recognize heavy oil directly from seismic data
Evaporites Bearing Faults as a Tool to Understand the Deformation Processes into the Seismogenic zone of the Northern Apennines (Italy). American Geophysical Union
No full textZone di faglia in rocce evaporitiche ed interpretazione dei processi deformativi nella zona sismogenetica dell’Appennino Settentrionale.
No full textEvaporites bearing faults as a tool to understand the deformation processes into the seismogenic zone of the Northern Apennines. Tectonic Studies Group
No full textA slip tendency analysis to test mechanical and structural control on aftershock rupture planes
No full textLarge portions of intraplate regions are characterised by relatively uniform stress fields with moderate to large main shock fault-ruptures nucleating on planes successfully predicted by 2D frictional fault reactivation theory. Here we use a slip tendency analysis, based on the notion that slip on a fault is controlled by the ratio of shear stress to normal stress acting on the plane of weakness, to test whether aftershock sequences are also governed by fault reactivation theory within the regional stress field. We observe that aftershocks for two well-documented seismic sequences occurring in extensional and compressional environments, the 1997 M(w)=6.0 Colfiorito sequence (Central Italy) and the 1999 M(w)=7.5 Chi-Chi sequence (Taiwan), respectively, nucleate on planes favourably oriented for frictional fault reactivation. In particular, 89% of 329 and 81% of 121 events for the Colfiorito and Chi-Chi sequences respectively, are the result of fault reactivation processes on geological structures that represent well oriented planes within the regional stress field. This suggests that stress rotations induced by the main shock for these two intracontinental sequences are unlikely. In addition, the percentage of well oriented aftershock rupture planes reaches 100% for Colfiorito and 86% for Chi-Chi if we consider a magnitude threshold above M(w)=3.7 and M(w)=5.0, respectively. We interpret this as the fact that stress heterogeneities if present are generally localised and can influence only small structures capable of generating small magnitude aftershocks. (c) 2007 Elsevier B.V. All rights reserved
From petrophysical properties to forward-seismic modeling of facies heterogeneity in the carbonate realm (Majella Massif, central Italy)
No full textForward modeling is a fundamental support to study the seismic response of reservoirs structure and subsurface architectures. Carbonate reservoirs result in non-univocal seismic response caused by the facies heterogeneity and due to the possible presence of infilling fluids. The carbonate ramp outcropping in the Majella Massif (Central Italy) is an excellent surface analogue of buried heterogeneous structures. It offers the opportunity to directly analyze a carbonate reservoir which clearly shows facies variations and natural hydrocarbon-impregnations allowing to quantify the induced petrophysical changes. In this study, we integrated original field and laboratory measurements with 3D facies modeling to carry out 1D and 2D forward seismic models of a carbonate reservoir following a structured workflow. A careful petrophysical characterization measuring density porosity and seismic wave velocities has been performed in all the sampled facies and then used as input for the 3D velocity model. The “Sequential Gaussian Simulation Co-Kriging” (SGS-CK) results to be the best algorithm to build the seismic velocity model, consequently a low-frequency (40 Hz) synthetic 1D seismogram was carried out simulating facies and hydrocarbon-saturation variations. Thus, a 9 km long synthetic profile from the platform top to the basin, SE-NW oriented, was carried out simulating the outcropping architecture and spatial distribution of the facies. The obtained synthetic seismic outputs are closer to real geophysical surveys with respect to classical forward modeling. Perturbations of the seismic signal derived from the modeled facies heterogeneity without introducing artificial noises made the synthetic results more realistic preserving the horizons architecture. We also quantitatively show that variations in the signal related to the hydrocarbon saturation can result in an increase or decrease in reflectivity depending on the seismic properties of the surrounding layers. The presented results give new insights about reservoir architectures and can be useful to better process as well as to interpret the field seismic data and the resulting seismic sections acquired in carbonate realms
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