Workflow for the Validation of Geomechanical Simulations through Seabed Monitoring for Offshore Underground Activities

Underground fluid storage is gaining increasing attention as a means to balance energy production and consumption, ensure energy supply security, and contribute to greenhouse gas reduction in the atmosphere by CO2 geological sequestration. However, underground fluid storage generates pressure changes, which in turn induce stress variations and rock deformations. Numerical geomechanical models are typically used to predict the response of a given storage to fluid injection and withdrawal, but validation is required for such a model to be considered reliable. This paper focuses on the technology and methodology that we developed to monitor seabed movements and verify the predictions of the impact caused by offshore underground fluid storage. To this end, we put together a measurement system, integrated into an Autonomous Underwater Vehicle, to periodically monitor the seabed bathymetry. Measurements repeated during and after storage activities can be compared with the outcome of numerical simulations and indirectly confirm the existence of safety conditions. To simulate the storage system response to fluid storage, we applied the Virtual Element Method. To illustrate and discuss our methodology, we present a possible application to a depleted gas reservoir in the Adriatic Sea, Italy, where several underground geological formations could be potentially converted into storage in the futur

How underground systems can contribute to meet the challenges of energy transition

The paper provides an overview of the several scientific and technical issues and challenges to be addressed for underground storage of carbon dioxide, hydrogen and mixtures of hydrogen and natural gas. The experience gained on underground energy systems and materials is complemented by new competences to adequately respond to the new needs raised by transition from fossil fuels to renewables. The experimental characterization and modeling of geological formations (including geochemical and microbiological issues), fluids and fluid-flow behavior and mutual interactions of all the systems components at the thermodynamic conditions typical of underground systems as well as the assessment and monitoring of safety conditions of surface facilities and infrastructures require a deeply integrated teamwork and fit-for-purpose laboratories to support theoretical research. The group dealing with large-scale underground energy storage systems of Politecnico di Torino has joined forces with the researchers of the Center for Sustainable Future Technologies of the Italian Institute of Technology, also based in Torino, to meet these new challenges of the energy transition era, and evidence of the ongoing investigations is provided in this paper

DEVELOPMENT OF A FLOW-THROUGH CELL FOR ACCURATE MEASUREMENTS OF LOW ELECTROLYTIC CONDUCTIVITY

Abstract − The present paper focuses on the development of a flow-through cell and a closed circuit that permit to carry out measurements of low electrolytic conductivity of aqueous solutions under flowing condition. The traceability path has been set as follows: samples with conductivity between 200 μS cm-1 and 50 μS cm-1 have been employed for the calibration of the geometric constant of the new cell, by comparison with the primary cell of Istituto Nazionale di Ricerca Metrologica (I.N.Ri.M.). Then the flow-through cell has been used to measure values with decreasing conductivities down to 1 μS cm-1. The measurement system capabilities have been evaluated to be limited by contamination effects

Estimation of skin components for a partially completed damaged well from injection tests

In the last years, alternative methodologies to conventional well tests have been proposed to eliminate gas emissions in the atmosphere. One of the most promising methodologies is injection/fall-off testing since it allows achievement of the main well testing targets, except for fluid sampling, while it complies with environmental constrains. However, the interpretation of an injection test in an oil reservoir is complicated by the presence of a time and space dependent interface between the fluid originally in place and the injected fluid (diesel or brine), which generates an additional bi-phase skin component. Typically, the application of the traditional analytical models only provides the possibility to evaluate the total well skin. Thus the mechanical component due to permeability damage in the near wellbore zone and the geometrical skin (if any) due to partial penetration of the well into the producing formation cannot be isolated from the bi-phase skin. However, the mechanical skin and the geometrical skin are fundamental parameters to estimate the well potential in the case of injection testing, given that the productivity index cannot be determined based on rate and pressure measurements as in conventional tests. An effective relationship was analytically derived to determine the mechanical skin, the geometrical skin and the bi-phase skin in the case of injection tests. The equation expresses the total skin as a linear composition of the three components. Therefore, it can be used to assess the permeability damage; in turn, the well productivity can be calculated. Additionally, this relationship can be applied in well test design to obtain an estimate of the total skin factor and thus the expected pressure increase during injection, or else the maximum rate to be injected during a test without fracturing the formation. The reliability of the relationship was verified against the results obtained with the aid of numerical simulators

Dual Transformer for Power Measurements in the Audio-Frequency Band

A new analog processing unit (APU) with an extended frequency band, which is based on an electromagnetic principle, has been designed and constructed at the Istituto Nazionale di Ricerca Metrologica (INRIM). The unit can be employed in power measurements in the audio-frequency band. The sum and the difference of two waveforms from 20 Hz to 100 kHz are simultaneously performed. The unit has been characterized to evaluate its behavior from power frequencies up to 20 kHz. The output signals of the APU and the phase relation between the sections of the unit have been characterized, and the results of the measurement and the model adopted are reported here. The additional devices that constitute the input structure of the thermal wattmeter acting as a scaling factor (shunts and alternating-current (ac) resistive dividers), as well as the automatic ac/direct-current transfer procedure, have been characterized