Seismic images are the most powerful and used tool in understanding the geological structures in the subsurface. Much of this methodology and expertise has been developed for siliciclastic environments, while for carbonates still a lot remains to be cleared. This is particularly true for faulted carbonates realms where seismic attributes variations are very difficult to be interpreted. The aim of this project is thus to identify and delineate the seismic signature of carbonate-bearing faults. To this aim we will INTEGRATE detailed laboratory-scale rock physics measurements on carbonate fault rocks and larger scale geophysical and borehole measurements to be used as input for the construction of a data-based seismic forward model of carbonate-bearing faults. We will sample fault rocks from three key locations where important regional carbonate faults crop out juxtaposing different carbonate host rocks (from very low to very high porosity and from pure to marly carbonates). Samples will be collected at increasing distance respect to the principal slip surfaces in order to investigate different developed fault rocks. After a preliminary characterization of pristine carbonate rocks, tests on fault rock samples will be run with the experimental deformation apparatus (BRAVA2) to perform laboratory measurements of Vp, Vs and to fully characterize the slip behavior (seismic-velocity weakening or aseismic-velocity strengthening) of these rocks. Derived elastic moduli will be used as input parameters for the seismic forward model that will be built by using Matlab. The obtained seismic images of the different faults, merged with the frictional properties derived from experiments will permit to identify a potentially seismogenic fault with a huge potential for both seismological and reservoir studies.
The results of the project will have significant implications for research in many fields. In fact, the study of the petrophysical and seismic properties of actual fault rocks will be extremely useful for the characterization of faulted reservoirs and sealing horizons in oil and gas exploration, for fault-hosted mineralization and for the identification of good geological site for a safe geological sequestration of CO2 or Hydrogen and storage of radioactive waste. Moreover, the acquired laboratory dataset will be a self-standing contribution to the scientific community due the lack of such data.
The project is expected to provide tools to link the seismic interpretation more properly to a real geological model in similar faulted carbonate geological context: the project will in fact investigate the seismic sensitivity to fault-related properties variation. This will help to increase the contribution of the geological interpretations of seismic lines and to reduce uncertainties in carbonate realm.
With the proposed project, we can test the overall seismic interpretation (which is the base of E&P activities involving geologists in the industry) and seismological prediction of fault slip behaviour. Indeed, realistic synthetic seismic data back-interpreted to produce a geological interpretation can be compared with the known geometries/characteristics of the outcropping faults architecture. Moreover, an Acoustic/Elastic Impedance model can be also back-generated as comparison, allowing a final assessment of the level of uncertainty within a specific seismic data, also to be compared with real datasets in the area, for a better more complete learning.
The project is expected to contribute to model and verify, in the outcrops and in the subsurface nearby analogue, the carbonate rock deformation behaviour when different types of carbonates are involved.
For the first time in literature the project will assign to different carbonate rocks a characteristic seismic signature based on the elastic and frictional properties for both diffuse (marly limestones) and localized (pure limestone) deformation mechanisms and for both high and low porosity carbonates. The scientific importance of such a contribution is to support more robust assessment and monitoring of areas where possible impact is generated by human related activities, such as Oil & Gas or CO2/Hydrogen sequestration, especially in proximity of potential earthquake-generating faults. This will have an indirect social impact on a sensible subject that requires nowadays robust quantitative contributions from the scientific community.
Economically, the project could provide benefits to any seismic acquisition project on carbonate targets especially in the planning of the survey, either on/off shore: this could have a potential benefit in reducing costs and make the seismic acquisition more efficient and targeted. Moreover, the aim of this integrated project is to provide additional tools to geoscientists in interpreting seismic data of the subsurface, to increase the geological value and predictivity of their interpretation and reduce uncertainties: this will result in a direct economic benefit permitting to better plan and carry on expensive standard activities linked to Exploration, Development and Production and Storage.