Gerson Cardoso da Silva

Simulation of Subsurface Multiphase Contaminant Extraction Using a Bioslurping Well Model

Subsurface simulation of multiphase extraction from wells is notoriously difficult. Explicit representation of well geometry requires small grid resolution, potentially leading to large computational demands. To reduce the problem dimensionality, multiphase extraction is mostly modeled using vertically averaged approaches. In this paper, a multiphase well model approach is presented as an alternative to simplify the application. The well model, a multiphase extension of the classic Peaceman model, has been implemented in the STOMP simulator. The numerical solution approach accounts for local conditions and gradients in the exchange of fluids between the well and the aquifer. Advantages of this well model implementation include the option to simulate the effects of well characteristics and operation. Simulations were conducted investigating the effects of extraction location, applied vacuum pressure, and a number of hydraulic properties. The obtained results were all consistent and logical. A major outcome of the test simulations is that, in contrast to common recommendations to extract from either the gas–NAPL or the NAPL–aqueous phase interface, the optimum extraction location should be in between these two levels. The new model implementation was also used to simulate extraction at a field site in Brazil. The simulation shows a good match with the field data, suggesting that the new STOMP well module may correctly represent oil removal. The field simulations depend on the quality of the site conceptual model, including the porous media and contaminant properties and the boundary and extraction conditions adopted. The new module may potentially be used to design field applications and analyze extraction data.

Towards Sustainability and Protection of Threatened Coastal Ecosystems: Management Strategies for a Rare Stone Mangrove in Gorda Beach, Armação dos Búzios, Brazil

Brazil ranks third in total mangrove area around the world, following Indonesia and Australia. Most Brazilian mangroves are poorly studied regarding hydrologic equilibrium mechanisms. Along Mangue de Pedra of Gorda beach, in Armacao dos Buzios, Rio de Janeiro State, Brazil, there is a rare mangrove, which has thrived over a rocky substratum. Of particular interest is the socioenvironmental and historical background of this mangrove amid potential and emerging land use conflicts. A combination of distinct rock units bound together by a geological fault in a semiarid microclimate led to a unique setting in which fresh groundwater from hanging sedimentary rock cliffs mix with seawater creating an unusual small mangrove before a sandy beach. This attractive landscape led to intense property speculation. Sustainable land use by ‘quilombolas’, descendants of ancient black slaves is being threatened by that speculation, leading to conflicts. Considering the factors and aspects reported above, Mangue de Pedra has high environmental, historical-cultural and scientific relevance and, consequently, should be preserved. Public management measures, however, have not being effective to protect it, leading to a gradual loss of local bio and geodiversity. Solution for this issue includes a set of measures such as creation of a comprehensive environmental protection unit, education and environmental awareness, dissemination of knowledge about the importance of the Mangue, social control and mobilization of the population, based on participation in the decision-making forums, the paradigm shift for UC administration, among others.