Fate and transport of nanohybrids in subsurface media for oil field applications

Interfacially active carbon nanotube hybrids have potential to be used in reservoir development applications. Carbon nanotubes hybrids (CNT) can act as carriers for catalytic nanoparticles into regions far inside the reservoir; they have the ability to stabilize water/oil interface in emulsions or can be used as contrast agents or sensors. One of the main challenges for successful utilization of these nanoparticles is the difficulty associated with stabilizing their dispersions and propagating them through the wellbore rock or deep inside the reservoir in harsh reservoir conditions of salinity and temperature. In this work, CNT were dispersed in high salinity brine using a combination of two polymers Gum Arabic (GA) and hydroxyethyl cellulose (HEC-10) and were propagated through porous media with minimum retention. It was found that GA is able to debundle the nanotubes into individual ones by adsorbing on the surface of nanotube while HEC-10 is thought to generate steric repulsion that keeps the tubes well dispersed and prevent them from agglomeration in the presence of high salt concentration. The combination of these two dispersing polymers was found crucial for successful propagation of nanohybrids through consolidated or unconsolidated porous media. Stable CNT dispersions have been propagated with low retention through 6” Berea cores of permeabilities as low as 200mD in 10% brine (8% NaCl and 2% CaCl2) and a temperature of 65oC. Carbon nanotube adsorption inside the core was found to be ranging between 0.02 and 0.04mg per gram of dry core weight and the overall nanotubes cumulative recovery was more than 80% of the injected nanoparticles with a normalized CNT concentration approaching 97% of the injected concentration. Increased retention of nanohybrids in the presence of oil in an oil pretreated core in comparison to an oil-free core has been observed which suggests adsorption of nanohybrids to the oil/water interface inside the core. The demonstration of the successful propagation of CNT through Berea cores is an important first step in the process of incorporating them into advancing reservoir characterization and/or enhanced oil recovery technologies

Níveis de proteína bruta para juvenis de pirarucu

The objective of this work was to verify the effect of four protein levels on pirarucu, Arapaima gigas, growth performance. One hundred and twenty pirarucu juveniles, with an average weight of 120.6±3.5 g, were stocked into 12 floating cages with 1 m3 (ten fish per cage), in a complete randomized design with four treatments (32.7%, 39.3%, 43.4% and 48.6% crude protein), in three replicates each. After 45 days, results showed that diet with highest protein level (48.6%) produced a better weight gain, specific growth rate, and differentiated body composition. Feed conversion and protein efficiency ratios did not show any differences among treatments. The dietary protein level required to produce maximum growth is 48.6%

Exigência Protéica e Relação Energia/Proteína para Alevinos de Piracanjuba (Brycon orbignyanus) Dietary Protein Requirement and Energy to Protein Ratio for Piracanjuba (Brycon orbignyanus) Fingerlings

O objetivo do presente estudo foi determinar a exigência protéica e correspondente relação energia/proteína em dietas para alevinos de piracanjuba, Brycon orbignyanus. Seis dietas semi-purificadas isocalóricas foram formuladas para conter 3.000 kcal de energia metabolizável (EM)/kg e concentrações de proteína bruta (PB) de 24, 26, 29, 32, 36 e 42%. Para essas concentrações, as relações E/P das dietas foram de 12,3; 11,6; 10,4; 9,2; 8,5 e 7,1 kcal EM/g PB, respectivamente. As fontes de proteína, lipídios e carboidratos digestíveis foram, respectivamente, caseína/gelatina, óleo de fígado de bacalhau/óleo de soja e dextrina. Após condicionamento de cinco dias, as dietas foram fornecidas, até a saciedade, em duas alimentações diárias, a 162 alevinos (27 peixes/dieta), que apresentaram 8,38 ± 0,09 g de peso médio inicial, distribuídos em 18 tanques de fibra-de-vidro de 100 L, conectados a um sistema de recirculação de água. A temperatura média da água foi de 26,3°C, com extremos de 23,7 e 30,2°C. Após 90 dias, a concentração de proteína na dieta que proporcionou ganho em peso máximo aos peixes foi 29% PB, com relação E/P igual a 10,4 kcal EM/g PB. As dietas com concentrações de PB iguais a 32, 36 e 42% não se mostraram superiores para conversão alimentar, taxa de eficiência protéica, valor produtivo da proteína e retenção de energia bruta. A deposição corporal de proteína e gordura não sofreu influência da concentração de PB da dieta<br>The aim of this study was to determine the dietary protein requirement and associated energy to protein (E/P) ratio for "Piracanjuba", Brycon orbignyanus, fingerlings. Casein-gelatin semipurified diets were formulated to contain six crude protein (CP) concentrations: 24, 26, 29, 32, 36 e 42% at one energy level, 3,000 kcal metabolizable energy (ME)/kg. These diets resulted in E/P ratios of 12.3, 11.6, 10.4, 9.2, 8.5 and 7.1 kcal ME/g CP, respectively. The protein, lipid and digestible carbohydrate sources were casein/gelatin, cod liver oil/soybean oil and dextrin, respectively. After an initial 5-day conditioning period, each experimental diet was fed to satiation, twice a day, to 8.38 ± 0.09 g piracanjuba fingerlings (n = 27), housed in eighteen 100-L fiberglass tanks connected to a water recirculating system, and kept at 26.3°C average water temperature (range: 23.7 to 30.2°C). After 90 days, the lowest dietary CP level that produced maximum fish weight gain was 29% CP with associated E/P ratio of 10.4 kcal ME/g CP. Higher dietary CP levels, i.e., 32, 36 and 42% did not improve 29% CP feed conversion, protein efficiency ratio, apparent net protein utilization and gross energy retained. Whole-body fish composition (total lipid and protein concentration) was not affected by the dietary CP leve