Droplet fragmentation: 3D imaging of a previously unidentified pore-scale process during multiphase flow in porous media

Using X-ray computed microtomography, we have visualized and quantified the in situ structure of a trapped nonwetting phase (oil) in a highly heterogeneous carbonate rock after injecting a wetting phase (brine) at low and high capillary numbers. We imaged the process of capillary desaturation in 3D and demonstrated its impacts on the trapped nonwetting phase cluster size distribution. We have identified a previously unidentified pore-scale event during capillary desaturation. This pore-scale event, described as droplet fragmentation of the nonwetting phase, occurs in larger pores. It increases volumetric production of the nonwetting phase after capillary trapping and enlarges the fluid−fluid interface, which can enhance mass transfer between the phases. Droplet fragmentation therefore has implications for a range of multiphase flow processes in natural and engineered porous media with complex heterogeneous pore spaces

Políticas públicas para a formação de professores e contextos emergentes na educação superior

This text refers to training policies for teachers and the rebound in emerging contexts in higher education, from the development of programs such as Fellowship Program Introduction to Teaching (PIBID) Training Program of Municipal Directors of Education (PRO -Board) and Centre of Education (OBEDUC). The objective is, in this sense, analyzing the policies of teacher training (initial and ongoing), developed by the Education Center of the Federal University of Santa Maria, and emerging contexts in higher education. It is a qualitative research from the case study, and the data analysis is grounded in the collection and building data from regulatory frameworks and allusive reports to Government programs already mentioned implemented by the Education Center the Federal University of Santa Maria (CE / UFSM). The study has contributed to the understanding of public policies for teacher training (initial / continuous) in close interrelation with emerging contexts in higher education; recognition and understanding of the organizational culture and management processes of the programs analyzed from the experiences developed by CE / UFSM and its impact on quality of initial and continuing teacher training; a critical reflection on the understanding and involvement of teachers / managers on emerging contexts in higher education.Este texto refere-se a políticas de formação de professores e a repercussão em contextos emergentes na educação superior, a partir do desenvolvimento de programas como o Programa de Bolsas de Iniciação à Docência (PIBID), Programa de Capacitação de Conselheiros Municipais de Educação (PRÓ-CONSELHO) e Observatório de Educação (OBEDUC). Objetiva-se, nesse sentido, analisar as políticas públicas de formação de professores (inicial e permanente), desenvolvidas pelo Centro de Educação da Universidade Federal de Santa Maria, e os contextos emergentes na educação superior. Trata-se de uma pesquisa de natureza qualitativa, a partir do estudo de caso, sendo que a análise de dados está embasada na coleta e construção de dados a partir de marcos regulatórios e relatórios alusivos a Programas de Governo já mencionados implementados pelo Centro de Educação da Universidade Federal de Santa Maria (CE/UFSM). Os estudos vem contribuindo para a compreensão das políticas públicas voltadas para a formação de professores (inicial/permanente) em íntima inter-relação com contextos emergentes na educação superior; o reconhecimento e a compreensão da cultura organizacional e dos processos de gestão dos programas analisados a partir das experiências desenvolvidas pelo CE/UFSM e sua repercussão na qualidade da formação inicial e permanente de professores; uma reflexão crítica acerca da compreensão e o envolvimento dos professores/gestores sobre contextos emergentes na educação superior.Este texto se refiere a políticas de formación de profesores y la repercusión en contextos emergentes en la educación superior, a partir del desarrollo de programas como el Programa de Becas de Iniciación a la Docencia (PIBID), Programa de Capacitación de Consejeros Municipales de Educación (PRÓ-CONSELHO) y Observatorio de Educación (OBEDUC). Se objetiva, en ese sentido, analizar las políticas públicas de formación de profesores (inicial y permanente), desarrolladas por lo Centro de Educación de la Universidad Federal de Santa Maria, y los contextos emergentes en la educación superior. Se trata de una investigación de naturaleza cualitativa, a partir del estudio de caso, siendo que el análisis de datos se basa en la colecta y construcción de datos a partir de marcos regulatorios e informes alusivos a Programas de Gobierno ya mencionados implementados por el Centro de Educación de la Universidad Federal de Santa Maria (CE/UFSM). Los estudios vienen contribuyendo a la comprensión de las políticas públicas vueltas a la formación de profesores (inicial/permanente) en íntima interrelación con contextos emergentes en la educación superior; el reconocimiento y la comprensión de la cultura organizacional y de los procesos de gestión de los programas analizados a partir de las experiencias desarrolladas por lo CE/UFSM y su repercusión en la calidad de la formación inicial y permanente de profesores; una reflexión crítica acerca de la comprensión y el envolvimiento de los profesores/gestores sobre contextos emergentes en la educación superior

The impact of vapor/liquid-equilibria calculations on scale-prediction modeling

Vapor/liquid-equilibria (VLE) calculations, particularly involving the phase behavior of carbon dioxide (CO) and hydrogen sulfide (HS), are used in scale-prediction modeling. In this work, the impact of VLE calculations for CO- and HS-rich gas phases and for acid- and sour-gas mixtures on scale-prediction calculations is evaluated. Three equations of state (EOSs) - Soave-Redlich-Kwong (SRK) (Soave 1972), Peng-Robinson (PR) (Peng and Robinson 1976), and Valderrama-Patel-Teja (VPT) (Valderrama 1990)- are implemented in the Heriot-Watt model and used in VLE calculations. The solubility of single-component CO and HS in water and the solubility of a gas mixture in water were compared with experimental data in terms of the absolute relative deviation (ARD). The solubility data were then used in PHREEQC (USGS 2016) to calculate the impact of using different EOSs on carbonate and sulfide scales, particularly on calcium carbonate (CaCO) and iron sulfide (FeS). Average ARDs of 6.04, 4.10, and 3.77% between experimental and calculated values for CO solubility in water were obtained for the SRK, PR, and VPT EOSs, respectively. Similarly, for HS solubility in water, average ARDs of 6.49, 6.66, and 6.48% were obtained for each EOS, respectively. For the solubility of sourand acid-gas mixtures in water, average ARDs of 13.92, 13.25, and 10.78% were obtained, respectively. It has thus been concluded that the VPT EOS performs better than the SRK and PR EOSs in VLE calculations for the analyzed data. The errors introduced in VLE calculations have been found to impact the calculation of the amount of CaCO precipitated, with consequences for scale-inhibitor selection. Higher deviations were found in the amount of CaCO precipitation for gas mixtures when compared with a single-component, CO-rich phase. Furthermore, the large errors occurring in VLE calculations for HS solubility have not been found to impact the calculation of the amount of FeS precipitated when HS is in excess with respect to Fe. In addition to this, a case study that was performed by use of formation-water data from the Brazilian presalt revealed that the choice of EOS can cause errors of 6 kg of precipitate during each day of production. Scale-prediction calculations carried out with PHREEQC demonstrate that VLE calculations can have a high impact on mineral precipitation. Thus, it is recommended that the best VLE model available should always be used for scale-prediction modeling, particularly when mixtures of gases are present

Laboratory investigation of zinc and lead sulphide inhibition

Abstract The formation of zinc sulphide (ZnS) and/or lead sulphide (PbS) has been a persistent problem, particularly in high temperature high pressure HT/HP fields. ZnS and PbS deposition can pose safety hazards and have serious economic consequences including reduction in well productivity and may require the implementation of an effective scale mitigation and removal strategy. HT/HP fields are prone to critical changes in temperature and pressure and, in addition, they usually have high salinity brines; indeed they are often referred to as HP/HT/HS systems. When these factors (pressue/temperature/salinity) vary together, they tend to trigger the formation of inorganic scales including sulphides. Apart from the role of temperature and salinity in scale formation, these (HT/HS) conditions often negatively impact scale inhibitor performance due to chemical degradation or incompatibility. The objective of this study was to investigate ZnS and PbS formation (as single or combined scales) and inhibition over a range of parameters including pH, temperature, salinity, time and initial Zn, Pb and H2S concentrations. Polymeric and phosphonate scale inhibitors (SIs) were tested using static scale formation experiments, with samples being analysed by inductively coupled plasma (ICP) analysis, Environmental Scanning Electron Microscopy (ESEM), pH and particle size distribution measurements. Of the seven scale inhibitors tested, only two demonstrated inhibitory capacity at active concentrations of 100 ppm or below. SI-2, a high-molecular weight polymer, was remarkably effective in preventing both zinc and lead sulphide deposition regardless of the final supernatant pH. SI-3 showed more limited efficacy compared with SI-2 with its highest inhibition being achieved at low pH values.This information is important to consider when designing scale inhibitor treatments; as carbon dioxide liberates from produced water due to decreasing pressureit causes the pH to increase, which may cause a drop in the inhibition efficiency of some scale inhibitors. Increasing the brine salinity had a detrimental impact on the performance of the tested scale inhibitors. Neither SI-2 nor SI-3 were able to prevent PbS deposition by ionic displacement of Zn from ZnS by Pb2+ despite the fact that both scale inhibitors were effective against PbS under the same conditions using the conventional scale inhibition experiments. The particle size distribution of the partially inhibited ZnS and PbS particulates was found to be dependent on the type and concentration of the scale inhibitor, the final pH and salinity. The difference in particle size could have significant effects on in-line filter blocking tests and produced water quality issues.</jats:p

Carbonate and sulphide scale prediction modelling in auto-scaling processes:Procedure for the calculation of reservoir fluid compositions and scale profiles in production systems using topside data

AbstractCarbonate and sulphide scales can form in CO2 and/or H2S-rich environments in a process which we refer to as "auto-scaling", i.e. these scales form in the produced brine due to a change in conditions such as pressure and temperature, not due to brine mixing. Particularly in production systems, carbonate and sulphide scales can form due to the evolution of CO2 and H2S from the aqueous phase to the gas phase caused by a pressure decrease. Carbonate scale formation in this manner is broadly understood; however, there are details of precisely how this occurs in auto-scaling processes which are not widely appreciated.Measuring the water composition at surface locations (e.g. at the separator) does not give a full indication per se of the amount of scale that has precipitated upstream of the sampling point. However, the composition of the water before precipitation occurs is required for predicting the scaling potential of the system, and this information is seldom available. In this paper, we propose a model that accounts for this issue, and that accurately calculates the carbonate and sulphide scaling profiles in CO2 and/or H2S-rich production systems by knowing only commonly available surface data – i.e. pressure, temperature, and fluid compositions (water, gas, and oil). A rigorous workflow which can do this calculation using any aqueous scale prediction model along with a PVT Model has already been published by the authors (Verri et al, 2017a). The current paper describes a new model to do these calculations which also includes an approach for estimating both the "correct" scaling case within a range of cases up to the "worst case" carbonate scaling scenario.A scale prediction model has been developed to include a three-phase flash algorithm (using the Peng-Robinson Equation of State) coupled with an aqueous electrolyte model (using the Pitzer equations as the activity model). This model is used to run a demonstration example showing the procedure to calculate accurate auto-scaling profiles in CO2 and/or H2S-rich production systems, which is based on building a sensitivity analysis on the ions directly involved in precipitation reactions. We also note that auto-scaling profiles in production systems are commonly obtained by sectioning the production system – either by parameterising depth with pressure and temperature, or by selecting specific locations (e.g. DHSV, wellhead, etc.). Then, established guidelines to treat scale (or not) based on the calculated saturation ratios and precipitated masses of scale can be applied. We show that such an approach is not optimal and that it can lead to under or over-estimation of scale treatments. Furthermore, building on our previous method (Verri et al 2017a) we propose an approach to model the cumulative amount of scale formed under full equilibrium conditions, which is not dependent on how the production system is sectioned. By doing so, the correct amount of scale formed in the production system is always calculated, thus avoiding non-optimum scale treatments.Our approach focuses on calculating the correct auto-scaling profiles in CO2 and/or H2S-rich production systems, and on correctly interpreting the results obtained by thermodynamic modelling and it can be easily integrated with commonly available scale prediction software.</jats:p