Efeito da incorporação de diatomita na estabilidade e permeabilidade de compósitos cimentíceos espumados aplicados a poços de petróleo

Lightweight oilwell cement slurries have been recently studied as a mean to improve zonal isolation and sheath-porous formation adherence. Foamed slurries consisting of Portland cement and air-entraining admixtures have become an interesting option for this application. The loss in hydrostatic pressure as a consequence of cement hydration results in the expansion of the air bubbles entrapped in the cement matrix, thus improving the sheath-porous formation contact. Consequently, slurries are able to better retain their water to complete the hydration process. The main objective of the present study was to evaluate the effect of the addition of an air-entraining admixture on the density, stability and permeability of composite slurries containing Portland cement and diatomite as light mineral load. Successful formulations are potential cementing materials for low fracture gradient oilwells. The experimental procedures used for slurry preparation and characterization were based on the American Petroleum Institute and ABNT guidelines Slurries containing a pre-established concentration of the air-entraining admixture and different contents of diatomite were prepared aiming at final densities of 13 to 15 lb/gal. The results revealed that the reduction of 15 to 25% of the density of the slurries did not significantly affect their strength. The addition of both diatomite and the air-entraining admixture increased the viscosity of the slurry providing better air-bubble retention in the volume of the slurry. Stable slurries depicted bottom to top density variation of less than 1.0 lb/gal and length reduction of the stability sample of 5.86 mm. Finally, permeability coefficient values between 0.617 and 0.406 mD were obtained. Therefore, lightweight oilwell cement slurries depicting a satisfactory set of physicochemical and mechanical properties can be formulated using a combination of diatomite and air-entraining admixtures for low fracture gradient oilwells

The history of the introduction of the giant river prawn, Macrobrachium cf. rosenbergii (Decapoda, Palaemonidae), in Brazil: new insights from molecular data

The giant river prawn, Macrobrachium cf. rosenbergii, is one of the most cultivated freshwater prawns in the world and has been introduced into more than 40 countries. In some countries, this prawn is considered an invasive species that requires close monitoring. Recent changes in the taxonomy of this species (separation of M. rosenbergii and M. dacqueti) require a re-evaluation of introduced taxa. In this work, molecular analyses were used to determine which of these two species was introduced into Brazil and to establish the geographic origin of the introduced populations that have invaded Amazonian coastal waters. The species introduced into Brazil was M. dacqueti through two introduction events involving prawns originating from Vietnam and either Bangladesh or Thailand. These origins differ from historical reports of the introductions and underline the need to confirm the origin of other exotic populations around the world. The invading populations in Amazonia require monitoring not only because the biodiversity of this region may be affected by the introduction, but also because admixture of different native haplotypes can increase the genetic variability and the likelihood of persistence of the invading species in new habitats.

Estratégias de fitorremediação de duas minas abandonadas - Tinoca e Mostardeira

O presente trabalho teve como objectivo a implementação de estratégias de remediação de duas minas abandonadas na região do Alto Alentejo, a mina da Tinoca e a mina da Mostardeira. Neste trabalho foram realizados ensaios de fitoremediação com as espécies Brassica juncea (L.) Czern, Solanum nigrum L., Piptatherum miliaceum (L.)Coss. e Spergularia purpurea (Persoon)G. Don fil. As misturas utilizadas como suporte para desenvolvimento das plantas resultaram da mistura (1:1) de resíduos de escombreira e solo. Estas misturas foram realizadas para as duas minas independentemente. A estas misturas foram adicionados correctivos minerais e um correctivo orgânico. Dos estudos realizados observou-se que medidas de atenuação/diluição não se mostraram suficientemente eficazes para permitir uma estabilização da zona superficial em causa, pelas espécies de plantas estudadas. Por outro lado, a adição de um correctivo orgânico, juntamente com a subida do pH do solo, conduziu a um melhoramento das características físicas e químicas das misturas originais facilitando a sua revegetação. ABSTRACT: This study was designed to implement remediation strategies in two abandoned mines in the region of Alto Alentejo, the Tinoca mine and Mostradeira mine. Phytoremediation tests were carried out with the species Brassica juncea (L.) Czern, Solanum nigrum L., Piptatherum miliaceum (L.) Coss. and Spergularia purpurea (Persoon) G. Don fil. The mixtures used to support plant growth resulted from the admixture (1:1) of waste tailings and soil and were performed independently for the two mines. Soil mineral correctives and organic fertilizers were added to these mixtures. The study showed that mitigation/dilution measures were not sufficiently effective to allow the stabilization of the area with the plant species studied. However, the addition of an organic corrective, along with the rise of soil pH, led to an improvement in the physical and chemical properties of the original amendment soil mixtures, hence facilitating its phytorestoration.