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The growing global energy demand has been faced with increasing concerns about climate change over recent decades. In order to cover the additional demand and to mitigate CO2 emissions, one option is to utilize renewable energies such as solar and wind power. These energy sources are, however, intermittent by nature. Therefore, it is inevitable that a quick balancing and back-up power should be available to maintain grid stability at a certain level. Gas turbine (GT) technology could certainly be one alternative for back-up/balancing power and could be utilized to complement renewable energy in the energy market. However, the GT industry needs to consider innovative cycle configurations to attain higher system performance and lower emissions and to cope with renewable powers. In this regard, the humid air turbine (HAT) cycle and the exhaust gas recirculation (EGR) cycle are amongst the promising GT cycles. In the current study a micro gas turbine (MGT), a Turbec T100, has been selected as the base case for further investigation. A thermodynamic model for the base case has been developed in IPSEpro software and validated using experimental data obtained from an existing test facility in Stavanger, Norway. Based on this validated model, system performance calculations for other alternative cycles, i.e. EGR and HAT cycles, have been carried out. Results confirm that the performance improvement potential is significant for the HAT cycle with only minor modifications to the baseline MGT cycle. The EGR cycle, with a maximum attainable recirculation ratio of 50%, shows a slightly lower level of performance compared to the base case. However, its potential for future CO2 capture is greater compared to the base case and the HAT cycle. The overall cycle efficiencies for the base case, the HAT, and the EGR cycles at full load operation, i.e. 100kW power, are 31.1%, 32.8%, and 30.4%, respectively.

Today's practice on the Norwegian Continental Shelf when designing solutions for permanent plug and abandonment (P&A) complies with NORSOK Standard D-010. This is a prescriptive approach to P&A, as opposed to a "fit for purpose" risk-based approach. A risk-based approach means that any given P&A solution is expressed in terms of the leakage risk, which can be formulated in terms of the following quantities; the probability that the (permanent) barrier system will fail in a given time period and the corresponding consequence in terms of leakage to the environment. As a part of building a leakage risk model for permanently plugged and abandoned wells, a simple leakage rate calculator has been developed for quick evaluation of the leakage potential from a given (permanent) well barrier solution. The leakage potential from the well can then be quantitatively assessed taking into account different leakage pathways including leakage through bulk cement, through cement cracks and through micro-annuli along cement interfaces. In the paper, we will provide models to estimate leakage rate for each leakage pathway and show how to integrate them in an overall leakage calculator, to obtain a description of leakage flow from the reservoir through failed barriers to the environment. The information and input parameters needed to achieve this will be discussed, and uncertain parameters will be treated probabilistically, thus allowing for expressing uncertainty in the leakage rate estimate. Results from the leakage calculator will be demonstrated on a synthetic case, showing variants of a permanently plugged and abandoned well.