GNGTS 2021 - Atti del 39° Convegno Nazionale

505 GNGTS 2021 S essione 3.3 CONTROL ON PETROPHYSICS PARAMETERS AND SEISMIC PROPERTIES IN SYNTHETIC SEISMIC FORWARD MODELING OF NON-ISOTROPIC CARBONATE SYSTEMS: INSIGHTS FROM FACIES HETEROGENEITY AND FAULT ZONES SEISMIC RESPONSES A. Tomassi 1* , F. Trippetta 1 , R. Ruggieri 1 1 Department of Earth Sciences, Sapienza University of Rome, Italy Forward modeling is a fundamental prospecting method to understand reservoirs structure and architecture in the subsurface. Carbonate reservoirs result in complicated seismic response caused by facies changes, petrophysical properties heterogeneity and to the possible presence of faults and infilling fluids. Synthetic seismic forward modeling is a powerful tool to quantifying the control exercised by such features. In this study, field and laboratory measurements are used to carry out 1D and 2D forward seismic models of a carbonate reservoir in Central Italy. In particular, we focused on the carbonate ramp outcropping in the Majella Massif since it represents an excellent surface analogue of buried carbonate reservoirs worldwide. It offers the opportunity to directly analyze facies and petrophysical properties on the involved rocks. Moreover, natural heavy-hydrocarbon-impregnations occurrences and outcropping faults allow to quantify the induced petrophysical variations. After an accurate sampling phase, density and porosity of samples were measured through a helium pycnometer on both hydrocarbon-saturated and not-saturated natural samples and seismic velocities were derived. We thus developed a workflow which from field sampling and laboratory measurement through Petrel modeling build a realistic property distribution model for the involved lithologies. Then a low-frequency (40Hz) synthetic 1D seismogram was carried out based on the Petrel property model. The presence of hydrocarbon causes an increase in acoustics impedance by 16,2% and it increases the amplitudes by 13,6% at the reservoir boundaries. A 2D (12 km long) synthetic profile from the platform top to the basin, oriented SSE-NNW, was then carried out simulating the outcropping architecture and spatial distribution of the facies. The synthetic 2D model demonstrates that Vp variations are related to facies association and distribution increasing the amplitude of reflectors. Furthermore, Vp variation generates large diffractions which often lead to a chaotic appearance within the seismic facies. To characterize the seismic response of faults, the porosity along the damage zones (DZ) was also modified. Higher porosity DZ, corresponding to lower seismic velocity, resulted to be more visible in seismic imaging with respect to lower porosity DZ. Ongoing laboratory measurements and simulations are expected to help in validating facies interpretation of real seismic profiles and fault behavior. The presented workflow establishes a closer link between forward modeling and actual seismic imaging with large implications for hydrocarbon-reservoir characterization and the identification of potential CO 2 or hydrogen storage sites. References Anselmetti, F. S., Eberli, G. P., & Bernoulli, D. (1997). Seismic modeling of a carbonate platform margin (Montagna della Maiella, Italy): Variations in seismic facies and implications for sequence stratigraphy. In Carbonate seismology, 373-406. Society of Exploration Geophysicists. https://doi. org/10.1190/1.9781560802099.ch15. Biot, M. A. (1941). General theory of three‐dimensional consolidation. Journal of applied physics, 12(2), 155-164. https://doi.org/10.1063/1.1712886.