MODELO ANALÍTICO PARA INYECCIÓN CONTINUA DE VAPOR EN YACIMIENTOS ESTRATIFICADOS DE CRUDO PESADO

RESUMENEl uso de  los modelos analíticos para predecir el comportamiento de un yacimiento, está sujeto a  la similitud existente entre el sistema modelado matemáticamente y el yacimiento. Por ello, se establece que  en  la  actualidad  no  se  dispone  de  un modelo  analítico  que  prediga  el  comportamiento  de  la inyección continua de vapor en yacimientos estratifcados, con las características de los yacimientos del Magdalena Medio Colombiano. Por esta razón, surge la necesidad de plantear un nuevo modelo que tenga en cuenta la presencia de intercalaciones de arcilla, en formaciones que están siendo sometidas a inyección continua de vapor.El  desarrollo  del modelo  propuesto  parte  de modelos  analíticos  existentes,  de  los  cuales  se  toman los principios físicos que gobiernan el fujo de calor y fuidos en el medio poroso. Posteriormente, el modelo es estructurado en tres etapas que comprenden la defnición del sistema modelado, el desarrollo matemático y  la evaluación de  las expresiones obtenidas para el volumen de  la zona calentada,  las pérdidas de calor instantáneas y acumuladas, la tasa de producción y factor de recobro de aceite. Los resultados obtenidos a partir del modelo analítico para la tasa de producción y el factor de recobro de  aceite  son  comparados  con  los  obtenidos  mediante  la  simulación  numérica  de  un  yacimiento estratifcado, lográndose una buena representatividad entre ambas respuestas. Con base en la anterior, se establece que el nuevo modelo analítico propuesto  representa el comportamiento de  la  inyección continua de vapor en yacimientos estratifcados de crudo pesado. Palabras  clave:  Inyección  continua  de  vapor,  modelo  analítico,  recobro  mejorado,  yacimientos estratifcados.ABSTRACTThe use of analytical models to predict the behaviour of a reservoir depends of to the similarity between the system modelling mathematically and reservoir. Currently there is not an analytical model to predict the behaviour of steamfood in stratifed reservoirs, with the characteristics of the Colombian reservoirs of Magdalena Medio. For this reason, there is a need to raise a new model that takes into account the presence of interbedded clay, in formations that are being subjected to steamfood.The development of the proposed model takes as its starting point existing analytical models, of which are taken the physical principles that govern the fow of heat and fuids in the porous media. The structuring of the model was conducted in three stages that include the defnition of system modelling, mathematical development and evaluation of expressions obtained for the volume of the heated zone, heat losses and accumulated snapshots, the rate of production and oil recovery factor.The  results  from  the  analytical model  for  the  production  rate  and  oil  recovery  factor  are  compared with  those obtained by the numerical simulation of a stratifed reservoir, achieving a good representation between them. Based on  the above,  the new analytical model represents  the behavior of  the steamfood  in stratifed reservoir of heavy oil. Keywords: Steamfood, analytical model, enhanced oil recovery, stratifed reservoir. 

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Pseudokinetic model for field-scale simulation of in-situ combustion

Orientador: Osvair Vidal TrevisaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de GeociênciasResumo: A combustão in-situ é um processo multiescala, multifísico que envolve simultaneamente o escoamento de fluidos no meio poroso, o equilíbrio de fases e a cinética das reações químicas. A simulação desse processo tem alcançado um elevado grau de desenvolvimento, no entanto, mecanismos básicos ainda são representados de maneira incompleta, impondo inúmeros desafios na modelagem. A dificuldade de modelar fenômenos relacionados com a combustão tem a ver com a representação do efeito da frente de combustão e a modelagem do consumo de combustível. Na combustão in-situ as reações químicas acontecem em uma zona delgada de menos de um metro de espessura, que é pequena quando comparada com a escala do reservatório de centenas ou milhares de metros. Na simulação na escala de campo, o uso de células de tamanho maior do que a zona de reação leva a erros na distribuição da temperatura. Consequentemente, a velocidade das reações não pode ser bem representada. De outro lado, os simuladores não permitem controlar a ocorrência das reações a partir da energia de ativação. Como resultado, o início das reações se torna independente da temperatura. O objetivo desta tese é desenvolver um modelo pseudocinético para a simulação numérica da combustão in-situ na escala de campo. Com o modelo pseudocinético pretende-se representar os fenômenos na zona de combustão, reduzindo o efeito do tamanho de célula. O trabalho foi desenvolvido em etapas. Primeiro foram estabelecidas as condições que o simulador deveria atender e definida a estratégia de abordagem, que foi a de desenvolver um modelo pseudocinético. Depois foi definida a metodologia de obtenção do modelo pseudocinético. Após o modelo pseudocinético concluído, este foi utilizado para a simulação de um campo de óleo pesado brasileiro submetido à combustão in-situ. O modelo pseudocinético proposto consiste em expressar a energia de ativação das reações em função da temperatura. Através do modelo, é possível restringir a ocorrência da reação de craqueamento, de modo que o início da formação do coque aconteça somente para temperaturas acima dos valores observados na zona de craqueamento. Note-se que neste cenário a quantidade de coque depositado pode ser modelada usando a reação de craqueamento, o que se constitui numa das principais contribuições do trabalho. O modelo permite manter a dependência da taxa de reação com a temperatura mediante o uso de valores de energia de ativação apropriados. Além disso, consegue-se reduzir o efeito da distribuição de temperatura mediante o controle da taxa de reação em função dos valores médios de temperatura observados nas células do modelo de simulação na escala de campo. Na simulação do piloto de combustão in-situ, o modelo pseudocinético foi obtido do ajuste progressivo dos parâmetros cinéticos das reações químicas, partindo da simulação do processo na escala de laboratório até a escala de campo. Os dados experimentais utilizados na simulação na escala de laboratório foram obtidos de um ensaio em tubo de combustão seca realizado no Laboratório de Métodos Térmicos de Recuperação do Departamento de Energia da UNICAMP. O fluido utilizado foi um óleo pesado de 15,3 °API proveniente da Bacia do Espírito SantoAbstract: The in-situ combustion is a multi-scale, multi-physics process, involving fluid flow in porous media, thermodynamic equilibrium of the phases involved and chemical kinetics of reactions. The simulation of this process has achieved a high degree of development, however basic mechanisms are still represented incompletely, imposing numerous challenges in modeling. The issues in the combustion modeling are related with the representation of the combustion front effect and the fuel consumption modeling. Chemical reactions of the in-situ combustion process take place in a thin zone of less than a meter thick, which is small compared to the field scale of hundreds or thousands of meters. Numerical simulations at the field scale typically use grid blocks that are at least two orders of magnitude greater than that. Such divergence leads to improper representations of key aspects of the process, as the temperature distribution and the reaction kinetics. In accordance with that the reaction occurrence is not controlled by the activation energy in the simulation models. The major shortcome is on fuel deposition, a key issue in in-situ combustion, which will happen from the start, since the cracking reaction may proceed even at reservoir temperature. The objective of this thesis is to develop a new pseudokinetic model for field-scale simulation of in-situ combustion. With the pseudokinetic model meant to improve the representation of the combustion zone effects reducing the gridblock size effect. The work was carried out in stages. First establishes the conditions that the simulator should meet and defined the strategy to develop a pseudokinetic model. Then a methodology was defined for obtaining the pseudokinetic model. After the pseudokinetic model is completed, it is applied to the in-situ combustion modeling of a Brazilian heavy oil field. The models pursue the idea of making the activation energy a function of the grid block temperature. The model allows restricting the cracking reaction occurrence by the temperature, so that the beginning of the coke deposition occurs at temperatures greater than the temperature observed in the cracking zone. Note that in this scenario the cracking reaction can be used to represent the coke deposition, which constitutes one of the main contributions of this work. The model allows maintaining the dependence of reaction rate with temperature through the use of appropriate activation energy values. Furthermore, the model reduces the temperature distribution effect by controlling the reaction rate based on average temperature values observed in the field simulation model. In the simulation of the in-situ combustion pilot, the pseudokinetic model was obtained from the progressive tuning of the kinetic parameters of chemical reactions, based on the simulation of the process from the laboratory to field scale. The experimental data used in the laboratory scale simulation were obtained from a dry combustion tube test carried out at the Thermal Recovery Methods Laboratory of the Energy Department at UNICAMP. The fluid used was a 15.3 ° API heavy oil from the Espírito Santo BasinDoutoradoReservatórios e GestãoDoutora em Ciências e Engenharia de PetróleoPETROBRA

Modelo analítico para inyección continua de vapor en yacimientos estratificados de crudo pesado

The use of analytical models to predict the behaviour of a reservoir depends of to the similarity between the system modelling mathematically and reservoir. Currently there is not an analytical model to predict the behaviour of steamfood in stratifed reservoirs, with the characteristics of the Colombian reservoirs of Magdalena Medio. For this reason, there is a need to raise a new model that takes into account the presence of interbedded clay, in formations that are being subjected to steamfood.The development of the proposed model takes as its starting point existing analytical models, of which are taken the physical principles that govern the fow of heat and fuids in the porous media. The structuring of the model was conducted in three stages that include the defnition of system modelling, mathematical development and evaluation of expressions obtained for the volume of the heated zone, heat losses and accumulated snapshots, the rate of production and oil recovery factor.The results from the analytical model for the production rate and oil recovery factor are compared with those obtained by the numerical simulation of a stratifed reservoir, achieving a good representation between them. Based on the above, the new analytical model represents the behavior of the steamfood in stratifed reservoir of heavy oil.El uso de  los modelos analíticos para predecir el comportamiento de un yacimiento, está sujeto a  la similitud existente entre el sistema modelado matemáticamente y el yacimiento. Por ello, se establece que  en  la  actualidad  no  se  dispone  de  un modelo  analítico  que  prediga  el  comportamiento  de  la inyección continua de vapor en yacimientos estratifcados, con las características de los yacimientos del Magdalena Medio Colombiano. Por esta razón, surge la necesidad de plantear un nuevo modelo que tenga en cuenta la presencia de intercalaciones de arcilla, en formaciones que están siendo sometidas a inyección continua de vapor. El  desarrollo  del modelo  propuesto  parte  de modelos  analíticos  existentes,  de  los  cuales  se  toman los principios físicos que gobiernan el fujo de calor y fuidos en el medio poroso. Posteriormente, el modelo es estructurado en tres etapas que comprenden la defnición del sistema modelado, el desarrollo matemático y  la evaluación de  las expresiones obtenidas para el volumen de  la zona calentada,  las pérdidas de calor instantáneas y acumuladas, la tasa de producción y factor de recobro de aceite. Los resultados obtenidos a partir del modelo analítico para la tasa de producción y el factor de recobro de  aceite  son  comparados  con  los  obtenidos  mediante  la  simulación  numérica  de  un  yacimiento estratifcado, lográndose una buena representatividad entre ambas respuestas. Con base en la anterior, se establece que el nuevo modelo analítico propuesto  representa el comportamiento de  la  inyección continua de vapor en yacimientos estratifcados de crudo pesado

SIMULACIÓN DE UN PILOTO DE INYECCIÓN CONTINUA DE VAPOR USANDO POZOS HORIZONTALES

 RESUMEN El uso de pozos horizontales en procesos de inyección continua de vapor es una práctica que en los últimos años ha llamado la atención de quienes están involucrados en la recuperación de crudos pesados. El interés en la utilización de los pozos horizontales se debe principalmente al aumento que se genera en el área de contacto entre el pozo y la zona productora, lo cual se refleja en una mayor eficiencia de la inyección de vapor. Una forma de establecer si el uso de pozos horizontales mejora el desempeño de la inyección continua de vapor es la simulación numérica del proceso. Por ello se diseñó un estudio de simulación con el objetivo de analizar el comportamiento de la inyección continua de vapor para un patrón de cinco puntos invertido. Para el piloto simulado se emplearon diferentes configuraciones que involucran el uso de pozos productores horizontales y verticales. Las diferentes corridas de simulación fueron realizadas en el simulador de procesos térmicos Steam, Tbermal and Advanced Processes ReservoirSimulator (STARS) de la compañía canadiense Computer Modelling Group (CMG). Palabras clave: Inyección continúa de vapor, pozos horizontales, simulación de yacimientos.    ABSTRACT The use of horizontal wells in processes of steamflood is a practice that in the last years has called the attention of those who is involved in the recovery of heavy oil. The interest in the utilization of the horizontal wells owes principally to the increase that is generated in the area of contact between the well and the producting zone, which is reflected in a major efficiency of the steam injection. A way to confirm if the use of horizontal wells improves the performance of the steamflood is the numerical simulation of the process. Therefore a simulation study was effectuated to analyze the behavior of the continuous steam injection for an inverted five-spot pattern. Different configurations for the simulated pilot were used that involve the use the horizontal and vertical well. The different cases from simulation were prepared in the simulator from thermal processes Steam, Thermal and Advanced Processes Reservoir Simulator (STARS) of the Canadian company Computer Modelling Group (CMG). Keywords: horizontal well, reservoir simulation, continuos steamflouding 

Development of an analytical model for steamflood in stratified reservoirs of heavy oil

The use of analytical models to predict reservoir behavior depends on the similarity between the mathematically modeled system and the reservoir. Currently, there are not any models available for the prediction of steamflood behavior in stratified reservoirs based on the characteristics of reservoirs found in the Colombian Middle Magdalena valley, because the existing analytical models describe homogenous or idealized reservoirs. Therefore, it is necessary to propose a new model that includes the presence of clay intercalation in zones submitted to steamflood. The new analytical model is founded on the principles describing heat flow in porous media presented in the models proposed by Marx and Langenheim (1959); Mandl and Volek (1967), and Closmann (1967). Then, a series of assumptions related to the producing and non-producing zones and steamflood were determined, thus defining the system to be modeled. Once the system is defined, the initial and boundary conditions were established to contribute to find specific solutions for the case described. A set of heat balancing procedures were proposed from which a series of integro-differential equations were found. These equations were solved by using the Laplace transform method. The mathematical expressions were defined for the calculation of parameters such as volume of the heated zone, the rate of instantaneous and cumulative heat losses, and the oil rate and recovery factor. We can find differences when comparing the model response with the simulation, because in the mathematical model, we cannot include phenomena such as drop pressure, relative permeability and the change of oil viscosity with temperature. However, the new analytical model describes approximately the steam zone behavior, when the heat flow in the clay intercalations is not in stationary state.uso de modelos analíticos para predizer o comportamento de uma jazida está sujeito à similitude entre o sistema modelado matematicamente e a jazida. Tendo em conta que os modelos analíticos existentes descrevem jazidas homogêneas ou muito idealizados, estabelecese que na atualidade não se dispõe de um modelo que prediga o comportamento da injeção contínua de vapor em jazidas estratificadas, com as características das jazidas do Magdalena Médio Colombiano. Por esta razão, surge a necessidade de propor um novo modelo que tenha em conta a presença de intercalações de argila em zonas que estejam sendo submetidas à injeção contínua de vapor. O novo modelo analítico parte dos princípios que descrevem o fluxo de calor em meios porosos, que são apresentados nos modelos de Marx e Langenheim (1959), Mandl e Volek (1967) e Closmann (1967). Posteriormente, uma série de suposições relacionadas com as zonas produtoras e não produtoras e a injeção contínua de vapor são estabelecidas, definindose assim o sistema a modelar. Uma vez definido o sistema, fixaramse as condições iniciais e de fronteira, com as quais se obteve uma solução particular para o caso descrito. Logo, foi proposto um conjunto de balanços de calor, dos que se obteve uma série de equações íntegro-diferenciais que foram resolvidas mediante o uso de transformadas de Laplace. Posteriormente, definiramse expressões matemáticas para o cálculo de parâmetros como o volume da zona aquecida, a taxa de perdas de calor instantâneas e acumuladas, a taxa e o fator de recuperação de óleo. Ao comparar os resultados obtidos com o modelo analítico e a simulação numérica, evidenciam-se certas diferenças devido a que no modelo matemático não é possível incluir fenômenos tais como a queda de pressão, permeabilidades relativas e a mudança da viscosidade com a temperatura. Entretanto, pôde-se estabelecer que o novo modelo descreve de forma aproximada o comportamento da zona de vapor quando o fluxo de calor nas intercalações de argila se mantém em estado não estacionário.El uso de modelos analíticos para predecir el comportamiento de un yacimiento, está sujeto a la similitud entre el sistema modelado matemáticamente y el yacimiento. Teniendo en cuenta, que los modelos analíticos existentes describen yacimientos homogéneos o muy idealizados se establece que en la actualidad no se dispone de un modelo que prediga el comportamiento de la inyección continua de vapor en yacimientos estratificados, con las características de los yacimientos del Magdalena Medio Colombiano. Por esta razón, surge la necesidad de plantear un nuevo modelo que tenga en cuenta la presencia de intercalaciones de arcilla, en zonas que están siendo sometidas a inyección continua de vapor. El nuevo modelo analítico parte de los principios que describen el flujo de calor en medios porosos, que son presentados en los modelos de Marx y Langenheim (1959), Mandl y Volek (1967) y Closmann (1967). Posteriormente, una serie de suposiciones relacionadas con las zonas productoras y no productoras y la inyección continua de vapor son establecidas, definiéndose así el sistema a modelar. Una vez definido el sistema, se fijaron las condiciones inicial y de frontera, con las cuales se obtuvo una solución particular para el caso descrito. Luego, se plantearon un conjunto de balances de calor, de los que se obtuvo una serie de ecuaciones integrodiferenciales que fueron resueltas mediante el uso de transformadas de Laplace. Posteriormente, se definieron expresiones matemáticas para el cálculo de parámetros como el volumen de la zona calentada, la tasa de pérdidas de calor instantáneas y acumuladas, la tasa y el factor de recobro de aceite. Al comparar los resultados obtenidos con el modelo analítico y la simulación numérica, se evidencian ciertas diferencias debido a que en el modelo matemático no es posible incluir fenómenos tales como la caída de presión, permeabilidades relativas y el cambio de la viscosidad con la temperatura. Sin embargo, se pudo establecer que el nuevo modelo describe de forma aproximada el comportamiento de la zona de vapor cuando el flujo de calor en las intercalaciones de arcilla se mantiene en estado no estacionario