Modelagem e previsão da perda de injetividade em poços canhoneados

Waterflooding is a technique largely applied in the oil industry. The injected water displaces oil to the producer wells and avoid reservoir pressure decline. However, suspended particles in the injected water may cause plugging of pore throats causing formation damage (permeability reduction) and injectivity decline during waterflooding. When injectivity decline occurs it is necessary to increase the injection pressure in order to maintain water flow injection. Therefore, a reliable prediction of injectivity decline is essential in waterflooding projects. In this dissertation, a simulator based on the traditional porous medium filtration model (including deep bed filtration and external filter cake formation) was developed and applied to predict injectivity decline in perforated wells (this prediction was made from history data). Experimental modeling and injectivity decline in open-hole wells is also discussed. The injectivity of modeling showed good agreement with field data, which can be used to support plan stimulation injection wells

Análise da modelagem experimental da perda de injetividade

Injectivity decline, which can be caused by particle retention, generally occurs during water injection or reinjection in oil fields. Several mechanisms, including straining, are responsible for particle retention and pore blocking causing formation damage and injectivity decline. Predicting formation damage and injectivity decline is essential in waterflooding projects. The Classic Model (CM), which incorporates filtration coefficients and formation damage functions, has been widely used to predict injectivity decline. However, various authors have reported significant discrepancies between Classical Model and experimental results, motivating the development of deep bed filtration models considering multiple particle retention mechanisms (Santos & Barros, 2010; SBM). In this dissertation, inverse problem solution was studied and a software for experimental data treatment was developed. Finally, experimental data were fitted using both the CM and SBM. The results showed that, depending on the formation damage function, the predictions for injectivity decline using CM and SBM models can be significantly different

Modelo Estocástico para bloqueio de poros e redução de permeabilidade

Modeling transport of particulate suspensions in porous media is essential for understanding various processes of industrial and scientific interest. During these processes, particles are retained due to mechanisms like size exclusion (straining), adsorption, sedimentation and diffusion. In this thesis, a mathematical model is proposed and analytical solutions are obtained. The obtained analytic solutions for the proposed model, which takes pore and particle size distributions into account, were applied to predict the particle retention, pore blocking and permeability reduction during dead-end microfiltration in membranes. Various scenarios, considering different particle and pore size distributions were studied. The obtained results showed that pore blocking and permeability reduction are highly influenced by the initial pore and particle size distributions. This feature was observed even when different initial pore and particle size distributions with the same average pore size and injected particle size were considered. Finally, a mathematical model for predicting equivalent permeability in porous media during particle retention (and pore blocking) is proposed and the obtained solutions were applied to study permeability decline in different scenarios

Modelagem matemática para o transporte de partículas sujeitas a múltiplos mecanismos de retenção

Discrepancies between classical model predictions and experimental data for deep bed filtration have been reported by various authors. In order to understand these discrepancies, an analytic continuum model for deep bed filtration is proposed. In this model, a filter coefficient is attributed to each distinct retention mechanism (straining, diffusion, gravity interception, etc.). It was shown that these coefficients generally cannot be merged into an effective filter coefficient, as considered in the classical model. Furthermore, the derived analytic solutions for the proposed model were applied for fitting experimental data, and a very good agreement between experimental data and proposed model predictions were obtained. Comparison of the obtained results with empirical correlations allowed identifying the dominant retention mechanisms. In addition, it was shown that the larger the ratio of particle to pore sizes, the more intensive the straining mechanism and the larger the discrepancies between experimental data and classical model predictions. The classical model and proposed model were compared via statistical analysis. The obtained p values allow concluding that the proposed model should be preferred especially when straining plays an important role. In addition, deep bed filtration with finite retention capacity was studied. This work also involves the study of filtration of particles through porous media with a finite capacity of filtration. It was observed, in this case, that is necessary to consider changes in the boundary conditions through time evolution. It was obtained a solution for such a model using different functions of filtration coefficients. Besides that, it was shown how to build a solution for any filtration coefficient. It was seen that, even considering the same filtration coefficient, the classic model and the one here propposed, show different predictions for the concentration of particles retained in the porous media and for the suspended particles at the exit of the media

Renal and antibacterial effects induced by myotoxin I and II isolated from Bothrops jararacussu venom

Bothrops jararacussu myotoxin I (BthTx-I; Lys 49) and II (BthTX-II; Asp 49) were purified by ion-exchange chromatography and reverse phase HPLC. In this work we used the isolated perfused rat kidney method to evaluate the renal effects of B. jararacussu myotoxins I (Lys49 PLA(2)) and II (Asp49 PLA(2)) and their possible blockage by indomethacin. BthTX-1 (5 mu g/ml) and BthTX-II (5 mu g/ml) increased perfusion pressure (PP; ct(120) = 110.28+/-3.70 mmHg; BthTX I = 171.28+/-6.30* mmHg; BthTX II = 175.50+/-7.20* mmHg), renal vascular resistance (RVR; ct(120) = 5.49+/-0.54 mmHg/ml.g(-1) min(-1); BthTX I = 8.62+/-0.37* mmHg/ml g(-1) min(-1); BthTX II=8.9+/-0.36* mmHg/ml g(-1) min(-1)), urinary flow (UF; ct(120)= 0.14+/-0.01 ml g(-1) min(-1); BthTX I=0.32+/-0.05* ml g(-1) min(-1); BthTX II=0.37+/-0.01* ml g(-1) min(-1)) and glomerular filtration rate (GFR; ct(120)=0.72+/-0.10 ml g(-1) min(-1); BthTX I=0.85+/-0.13* ml g(-1) min(-1); BthTX II=1.22+/-0.28* ml g(-1) min(-1)). In contrast decreased the percent of sodium tubular transport (%TNa+; ct(120)=79,76+/-0.56; BthTX I=62.23+/-4.12*; BthTX II=70.96+/-2.93*) and percent of potassium tubular transport (%TK+;ct(120)=66.80+/-3.69; BthTX I=55.76+/-5.57*; BthTX II=50.86+/-6.16*). Indomethacin antagonized the vascular, glomerular and tubular effects promoted by BthTX I and it's partially blocked the effects of BthTX II. In this work also evaluated the antibacterial effects of BthTx-I and BthTx-II against Xanthomonas axonopodis. pv. passiflorae (Gram-negative bacteria) and we observed that both PLA2 showed antibacterial activity. Also we observed that proteins Also we observed that proteins chemically modified with 4-bromophenacyl bromide (rho-BPB) decrease significantly the antibacterial effect of both PLA(2). In conclusion, BthTx I and BthTX II caused renal alteration and presented activity antimicrobial. The indomethacin was able to antagonize totally the renal effects induced by BthTx I and partially the effects promoted by BthTx II, suggesting involvement of inflammatory mediators in the renal effects caused by myotoxins. In the other hand, other effects could be independently of the enzymatic activity of the BthTX II and the C-terminal domain could be involved in both effects promoted for PLA(2). (C) 2005 Elsevier Ltd. All rights reserved.

Renal effects and vascular reactivity induced by Tityus serrulatus venom

Tityus serrulatus, popularly known as yellow scorpion, is one of the most studied scorpion species in South America and its venom has supplied some highly active molecules. The effects of T. serrulatus venom upon the renal physiology in human showed increased renal parameters, urea and creatinine. However, in perfused rat kidney the effects were not tested until now. Isolated kidneys from Wistar rats, weighing 240-280 g, were perfused with Krebs-Henseleit solution containing 6% (g weight) of previously dialysed bovine serum albumin. The effects of T. serrulatus venom were studied on the perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF), glomerular filtration rate (GFR), sodium tubular transport (%TNa+), potassium tubular transport (%TK+) and chloride tubular transport (%TCl-). Tityus serrulatus venom (TsV; 10 mu g/mL) was added to the system 30 min after the beginning of each experiment (n = 6). This 30 min period was used as an internal control. The mesenteric bed was perfused with Krebs solution kept warm at 37 T by a constant flow (4 mL/min), while the variable perfusion pressure was measured by means of a pressure transducer. The direct vascular effects of TsV (10 mu g/mL/min; n=6), infused at a constant rate (0.1 mL/min), were examined and compared to the infusion of the vehicle alone at the same rate. TsV increased PP (PP30'= 127.8 +/- 0.69 vs PP60' = 154.2 +/- 14 mmHg*, *p < 0.05) and RVR (RVR30' = 6.29 +/- 0.25 vs RVR60' = 8.03 +/- 0.82 mmHg/mL g(-1) min(-1)*, *p < 0.05), decreased GFR (GFR(30') =0.58 +/- 0.02 vs GFR(60') = 0.46 +/- 0.01 mL g(-1) min(-1)*, *p < 0.05) and UF (UF30' = 0.135 +/- 0.001 vs UF60' = 0.114 +/- 0.003 mL g(-1)min(-1)*, *p < 0.05). Tubular transport was not affected during the whole experimental period (120 min). on the other hand, the infusion of TsV (10 mu g/mL/min) increased the basal perfusion pressure of isolated arteriolar mesenteric bed (basal pressure: 74.17 +/- 3.42 vs TsV 151.8 +/- 17.82 mmHg*, *p < 0.05). TsV affects renal haemodynamics probably by a direct vasoconstrictor action leading to decreased renal flow. (c) 2005 Elsevier Ltd. All rights reserved.

The role of indomethacin and tezosentan on renal effects induced by Bothrops moojeni Lys49 myotoxin I

Renal changes determined by Lys49 myotoxin I (BmTx I), isolated from Bothrops moojeni are well known. The scope of the present study was to investigate the possible mechanisms involved in the production of these effects by using indomethacin (10 mu g/mL), a non-selective inhibitor of cyclooxygenase, and tezosentan (10 mu g/mL), an endothelin antagonist. By means of the method of mesenteric vascular bed, it has been observed that B. moojeni myotoxin (5 mu g/mL) affects neither basal perfusion pressure nor phenylephrine-preconstricted vessels. This fact suggests that the increase in renal perfusion pressure and in renal vascular resistance did not occur by a direct effect on renal vasculature. Isolated kidneys from Wistar rats, weighing 240-280 g, were perfused with Krebs-Henseleit solution. The infusion of BmTx-I increased perfusion pressure, renal vascular resistance, urinary flow and glomerular filtration rate. Sodium, potassium and chloride tubular transport was reduced after addition of BmTx-I. Indomethacin blocked the effects induced by BmTx-I on perfusion pressure and renal vascular resistance, however, it did not revert the effect on urinary flow and sodium, potassium and chloride tubular transport. The alterations of glomerular filtration rate were inhibited only at 90 min of perfusion. The partial blockade exerted by indomethacin treatment showed that prostaglandins could have been important mediators of BmTx-I renal effects, but the participation of other substances cannot be excluded.The blockage of all renal alterations observed after tezosentan treatment support the hypothesis that endothelin is the major substance involved in the renal pathophysiologic alterations promoted by the Lys49 PLA(2) myotoxin I, isolated from B. moojeni. In conclusion, the rather intense renal effects promoted by B. moojeni myotoxin-I were probably caused by the release of renal endothelin, interfering with the renal parameters studied. (c) 2006 Elsevier Ltd. All rights reserved.

Purification and renal effects of phospholipase A(2) isolated from Bothrops insularis venom

Bothrops insularis venom contains a variety of substances presumably responsible for several pharmacological effects. We investigated the biochemical and biological effects of phospholipase A(2) protein isolated from B. insularis venom and the chromatographic profile showed 7 main fractions and the main phospholipase A(2) (PLA(2)) enzymatic activity was detected in fractions IV and V. Fraction IV was submitted to a new chromatographic procedure on ion exchange chromatography, which allowed the elution of 5 main fractions designated as lV-1 to IV-5, from which lV-4 constituted the main fraction. The molecular homogeneity of this fraction was characterized by high-performance liquid chromatography (HPLC) and demonstrated by mass spectrometry (MS), which showed a molecular mass of 13984.20 Da; its N-terminal sequence presented a high amino acid identity (up to 95%) with the PLA(2) of Bothrops jararaca and Bothrops asper. Phospholipase A(2) isolated from B. insularis (Bi PLA(2)) venom (10 mu g/mL) was also studied as to its effect on the renal function of isolated perfused kidneys of Wistar rats (n = 6). Bi PLA(2) increased perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF) and glomerular filtration rate (GFR). Sodium (%TNa+) and chloride tubular reabsorption (%TCl-) decreased at 120 min, without alteration in potassium transport. In conclusion, PLA(2) isolated from B. insularis venom promoted renal alterations in the isolated perfused rat kidney. (c) 2007 Elsevier Ltd. All rights reserved.

Purification and characterization of the biological effects of phospholipase A(2) from sea anemone Bunodosoma caissarum

Sea anemones contain a variety of biologically active substances. Bunodosoma caissarum is a sea anemone from the Cnidaria phylum, found only in Brazilian coastal waters. The aim of the present work was to study the biological effects of PLA(2) isolated from the sea anemone B. caissarum on the isolated perfused kidney, the arteriolar mesenteric bed and on insulin secretion. Specimens of B. caissarum were collected from the Sao Vicente Channel on the southern coast of the State of São Paulo, Brazil. Reverse phase HPLC analysis of the crude extract of B. caissarum detected three PLA(2) proteins (named BcPLA(2)1, BCPLA(2)2 and BcPLA(2)3) found to be active in B. caissarum extracts. MALDI-TOF mass spectrometry of BcPLA(2)1 showed one main peak at 14.7 kDa. The N-terminal amino acid sequence of BcPLA(2)1 showed high amino acid sequence identity with PLA(2) group III protein isolated from the Mexican lizard (PA23 HELSU, HELSU, PA22 HELSU) and with the honey bee Apis mellifera (PLA(2) and 1POC_A). In addition, BcPLA(2)1 also showed significant overall homology to bee PLA(2). The enzymatic activity induced by native BCPLA(2)1 (20 mu g/well) was reduced by chemical treatment with p-bromophenacyl bromide (p-BPB) and with morin. BcPLA(2)1 strongly induced insulin secretion in presence of high glucose concentration. In isolated kidney, the PLA(2) from B. caissarum increased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate, and sodium, potassium and chloride levels of excretion. BcPLA(2)1, however, did not increase the perfusion pressure on the mesenteric vascular bed. In conclusion, PLA(2), a group III phospholipase isolated from the sea anemone B. caissarum, exerted effects on renal function and induced insulin secretion in conditions of high glucose concentration. (C) 2009 Elsevier Ltd. All rights reserved.

Purification and biological effects of a C-type lectin isolated from Bothrops moojeni

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Renal and vascular effects of the natriuretic peptide isolated from Crotalus durissus cascavella venom

Crotalus durissus cascavella is a snake that is usually found in the scrublands of northeast Brazil. The components of its venom may have effects on the vascular and renal systems. Recently, a new bradykinin inhibitory peptide has been identified in the venom of the Crotalinae family. The aim of the present study was to investigate the renal and vascular effects of the natriuretic peptide isolated from the venom of Crotalus durissus cascavella (NP2_Casca). The chromatographic profile showed the fractionation of substances identified as convulxin, gyroxin, crotoxin and crotamine, as well as fractions V and VI. The electrophoretic profile of fraction V consisted of several bands ranging from approximately 6 kDa to 13 kDa, while fraction VI showed only two main electrophoretic bands with molecular weights of approximately 6 and 14 kDa. Reverse-phase chromatography showed that NP2_Casca corresponds to about 18% of fraction VI and that this fraction is the main natriuretic peptide. NP2_Casca was compared to other natriuretic peptides from other sources of snake venom. All amino acid sequences that were compared showed a consensus region of XGCFGX, XLDRIX and XSGLGCX. The group treated with NP2-Casca showed an increase in perfusion pressure, renal vascular resistance, urinary flow and glomerular filtration rate. The percent of total and proximal tubular transport of sodium was reduced significantly after administration of the peptide. The mean arterial pressure showed a dose-dependent decrease after infusion of NP2_Casca, and an increase in nitrite production. In the aortic ring assay, NP2_Casca caused a relaxant effect in endothelium-intact thoracic aortic rings precontracted with phenylephrine in the presence and absence of isatin. NP2_Casca failed to relax the aortic rings precontracted with an isosmotic potassium Krebs-Henseleit solution. In conclusion, the natriuretic peptide isolated from Crotalus durissus cascavella venom produced renal and vascular effects. NP2_Casca reduced total and proximal sodium tubular transport, leading to an increase in sodium excretion, thereby demonstrating a diuretic action. A hypotensive effect was displayed in an arterial pressure assay, with an increase in nitrite production, suggesting a possible vasoactive action. (C) 2008 Elsevier Ltd. All rights reserved.

Renal- and calcium-dependent vascular effects of Polybia paulista wasp venom

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Renal and cardiovascular effects of Bothrops marajoensis venom and phospholipase A(2)

Bothrops marajoensis is found in the savannah of Marajo Island in the State of Par S and regions of Amapa State, Brazil. The aim of the work was to study the renal and cardiovascular effects of the B. marajoensis venom and phospholipase A(2) (PLA(2)). The venom was fractionated by Protein Pack 5PW. N-terminal amino acid sequencing of sPLA(2) showed amino acid identity with other lysine K49sPLA(2)s of snake venom. B. marajoensis venom (30 mu g/mL) decreased the perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate and sodium tubular transport. PLA(2) did not change the renal parameters. The perfusion pressure of the mesenteric bed did not change after infusion of venom. In isolated heart, the venom decreased the force of contraction and increased PP but did not change coronary flow. In the arterial pressure, the venom and PLA(2) decreased mean arterial pressure and cardiac frequency. The presence of atrial flutter and late hyperpolarisation reversed, indicating QRS complex arrhythmia and dysfunction in atrial conduction. In conclusion, B. marajoensis venom and PLA(2) induce hypotension and bradycardia while simultaneously blocking electrical conduction in the heart. Moreover, the decrease in glomerular filtration rate, urinary flow and electrolyte transport demonstrates physiological changes to the renal system. (C) 2009 Elsevier Ltd. All rights reserved.

Purification, characterization, crystallization and theoretical molecular modeling of gyroxin fraction from Crotalus durissus terrificus venom (Laurenti, 1768)

The venom of Crotalus durissus terrificus snakes presents various substances, including a serine protease with thrombin-like activity, called gyroxin, that clots plasmatic fibrinogen and promote the fibrin formation. The aim of this study was to purify and structurally characterize the gyroxin enzyme from Crotalus durissus terrificus venom. For isolation and purification, the following methods were employed: gel filtration on Sephadex G75 column and affinity chromatography on benzamidine Sepharose 6B; 12% SDS-PAGE under reducing conditions; N-terminal sequence analysis; cDNA cloning and expression through RT-PCR and crystallization tests. Theoretical molecular modeling was performed using bioinformatics tools based on comparative analysis of other serine proteases deposited in the NCBI (National Center for Biotechnology Information) database. Protein N-terminal sequencing produced a single chain with a molecular mass of similar to 30 kDa while its full-length cDNA had 714 bp which encoded a mature protein containing 238 amino acids. Crystals were obtained from the solutions 2 and 5 of the Crystal Screen Kit (R), two and one respectively, that reveal the protein constitution of the sample. For multiple sequence alignments of gyroxin-like B2.1 with six other serine proteases obtained from snake venoms (SVSPs), the preservation of cysteine residues and their main structural elements (alpha-helices, beta-barrel and loops) was indicated. The localization of the catalytic triad in His57, Asp102 and Ser198 as well as S1 and S2 specific activity sites in Thr193 and Gli215 amino acids was pointed. The area of recognition and cleavage of fibrinogen in SVSPs for modeling gyroxin B2.1 sequence was located at Arg60, Arg72, Gln75, Arg81, Arg82, Lis85, Glu86 and Lis87 residues. Theoretical modeling of gyroxin fraction generated a classical structure consisting of two alpha-helices, two beta-barrel structures, five disulfide bridges and loops in positions 37, 60, 70, 99, 148, 174 and 218. These results provided information about the functional structure of gyroxin allowing its application in the design of new drugs.

Extração e pré-tratamento químico de frutanos de Yacon, Polymnia sonchifolia

O processo de desintegração de tubérculos de yacon promove a incorporação de oxigênio que favorece a oxidação de compostos fenólicos e decorrente contaminação do extrato aquoso com cores e odores objetáveis que prejudicam a sua utilização. Este estudo buscou verificar uma metodologia simplificada de extração dos carboidratos presentes nos tubérculos de yacon e efetuar uma primeira remoção de resíduos e compostos originários das cores e odores indesejáveis, utilizando processos de coagulação e precipitação, aplicando tecnologias de baixo custo. Após a etapa de trituração e remoção dos restos celulares, o extrato teve seu pH aumentado para 9,5 e a temperatura para 90ºC, seguido de sedimentação. A remoção deste precipitado foi realizada por filtração em papel após a coagulação com diferentes concentrações de sulfato de alumínio comercial. Verificou-se que a melhor concentração de coagulante no extrato foi de 100ppm, removendo 90,6% dos compostos coloridos. O balanço de massa mostrou uma recuperação de 47,5% dos sólidos totais sendo que 35,6% estão na forma de carboidratos, verificado através da concentrção de carbono orgânico. O processo de pré-tratamento químico causou hidrólise nos oligofrutanos, detectado por um aumento na concentração de açúcares redutores totais, diretamente proporcional à concentração de sulfato de alumínio utilizado no tratamento de coagulação. Análises cromatográficas indicaram o perfil dos açúcares no hidrolisado e a extensão desta hidrólise que foi considerada pequena. A metodologia aplicada mostrou-se fácil, de baixo custo, eficiente e aplicável em agroindústrias nas zonas produtoras desta espécie de raiz tropical.