Potencial energético e alternativas para o aproveitamento do biogás e lodo de reatores UASB: estudo de caso Estação de tratamento de efluentes Laboreaux (Itabira)

RESUMO: Este trabalho estuda o potencial de aproveitamento energético dos subprodutos biogás e lodo gerados na estação de tratamento de efluentes (ETE) Laboreaux em Itabira (MG), composta de reatores UASB, filtros biológicos percoladores e unidade de desaguamento do lodo por filtro prensa. Os subprodutos biogás e lodo foram caracterizados em termos quantitativos (produção) e qualitativos (composição e poder calorífico) durante 12 meses de monitoramento. Foram estudados dois cenários de aproveitamento energético dos subprodutos: (i) uso prioritário do biogás para a secagem térmica do lodo e o excedente de biogás para geração de eletricidade em motor de combustão interna; e (ii) uso prioritário do biogás visando à geração de eletricidade e ao aproveitamento do calor dos gases de exaustão para a secagem térmica de lodo. Para a análise desses cenários, utilizou-se o software CHEMCAD(r) a fim de determinar as condições de queima do biogás em câmara de combustão e em motor de combustão interna, assim como na determinação dos balanços de massa e energia. O estudo analisou o potencial de aproveitamento dos subprodutos do tratamento como fonte de energia renovável para uso na própria ETE e para fornecimento a terceiros. No cenário 1, a geração de eletricidade é menor (atendendo 22,2% da demanda de energia da ETE), mas a secagem térmica possibilita maior redução no volume final de lodo a ser disposto ou a eliminação completa de disposição final se o lodo seco final (com 10% de umidade) for utilizado como combustível por terceiros. No cenário 2, a geração de eletricidade é capaz de suprir 57,6% da demanda de energia da ETE, todavia o calor contido nos gases de exaustão não é suficiente para a secagem de todo o lodo desaguado, configurando uma menor redução na quantidade de lodo a ser disposto (13,5 ou 24,9% de redução em massa, conforme a alternativa de remoção de umidade selecionada)

Investigation of Pressure Losses in Eccentric Inclined Annuli

Accurate pressure drop estimation is vital in the hydraulic design of annular drillholes in Petroleum Industry. The present study investigates the effects of fluid velocity, fluid type, fluid rheology, drillpipe rotation speed, drillpipe eccentricity and drillhole inclinationon on pressure losses with the presence of cuttings using both experiments and computational fluid dynamics (CFD). The eccentricity of the drillpipe is varied in the range of 0 – 100% and it rotates about its own axis at 0 – 150 rpm. The diameter ratio of the simulated drillhole is 0.56 and it is inclined in the range of 0 – 15°. The effects of fluid rheology are addressed by testing power law and yield power law fluids. Both of the laminar and turbulent conditions are experimentally tested and numerically simulated. Experimental data confirmed the validity of current CFD model developed using ANSYS 16.2 platform. The goal of the current work is to develop a comprehensive CFD tool that can be used for modeling the hydraulic conditions associated with hole cleaning in extended reach drilling.</jats:p

Nanoparticle-Based Drilling Fluids for Minimizing Formation Damage in HP/HT Applications

Abstract Drilling fluid must fulfill various functions with a great impact on the drilling performance. Drilling fluid invasion can cause formation damage. Good quality mudcakes can prevent such damage. This research focuses on the lab techniques and performance results of testing innovative water-based drilling fluids containing nanoparticles (NPs) for minimizing formation damage at high-pressure/high-temperature (HP/HT) conditions. A couette type viscometer was used to examine the rheological properties of the drilling fluids tested in this research. Zeta potential measurements were conducted at different temperatures and concentrations to assess their stability and to investigate the role of charge potential. Indiana limestone outcrops were examined as the filter media for both static and dynamic filtration (up to 350°F and 500 psi) using a HP/HT dynamic filter press. The mudcakes were investigated using a computed-tomography (CT) scan, and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) was used to measure the concentrations of key ions in the filtrate fluids. A significant reduction in the filtrate fluid volume was achieved when using ferric oxide NPs (-43% for 0.5 wt%) compared to that of the base fluid. However, adding silica NPs led to an increase in the filtrate volume and mudcake thickness. Increasing the NP concentration resulted in an increase in the fluid loss and mudcake thickness. The mudcakes consisted of two layers, as indicated by the CT scan analysis. 0.5 wt% was found to be the optimal NP concentration, which provides less agglomeration and a reduction in the mudcake permeability by −76.4%. At this concentration, the ICP-OES analysis showed a higher cation dissociation, which promoted the formation of a different clay platelet microstructure. At a higher NP concentration, a new layer of NPs was formed in the mudcake, which adversely affects the mudcake characteristics, as demonstrated by CT scan analysis and SEM-EDS elemental mapping. The rheological measurements indicated a good rheology at different temperatures and NP concentrations. Moreover, the NPs helped to stabilize the viscosity and yield stress at high temperatures (up to 200°F). Aging at 350°F for 16 hours showed that NP-based drilling fluids remain stable with minor changes in rheological properties. The obtained rheological data for various NPs is fitted to the classical drilling fluid rheological models to determine the best fit-model, which can then be applied to an efficient design. This research provides a comprehensive evaluation of improved water-based drilling fluids, using ferric oxide and silica NPs for HP/HT applications. The examined NPs have the potential to enhance drilling fluid properties, which provides more efficient drilling operations and less formation damage.</jats:p

CFD Simulation of Three Phase Gas-Liquid-Solid Flow in Horizontal Pipes

The objective of this work is to analyze fluid flow in horizontal pipes with three phase gas-liquid-solid Newtonian fluid by our developed CFD simulation model and validate the simulation with experimental works. Air as gas, water as liquid and silica sand as solid particle is used for this work. ANSYS fluent version 16.2 is used to do the simulation. Eulerian model with Reynolds Stress Model (RSM) turbulence closure is adopted to analyze multiphase fluid flow. Length of pipe is 2.9 m and diameter is 0.0416 m, which are selected from experimental works to validate the simulation and after a good agreement with experimental data, sensitivity analysis is conducted to observe the three phase fluid flow characteristics through horizontal flow. Pressure gradient (pressure drop per unit length) is used as primary parameter to analyze. Effect of in situ concentration of solid in slurry, diameter of pipeline, roughness of wall material and viscosity of water in slurry are analyzed throughout this paper. This article provides validity of our proposed model. After that we tried to perform some parametric studies, changing variables of three phase fluid flow through horizontal pipeline with ours validated model. The main approach here is to demonstrate our CFD model in different ways to researchers and industries related to multiphase pipeline flow fields and make it acceptable to them. Also, Fluid Structure Interaction (FSI) is introduced at the end of this study to explain the goal of this project.</jats:p

Characterization of Filter Cake Generated by Nanoparticle-Based Drilling Fluid for HP/HT Applications

Abstract As high-pressure/high-temperature (HP/HT) drilling is inherently expensive, drilling fluids and technologies should be carefully selected to successfully handle the associated challenges. Over the past few years, nanoparticles (NPs), among other additives, have been investigated to address these challenges. The objective of this study is to investigate the potential of using ferric oxide NPs on the filter cake properties in downhle drilling environments. Having an efficient filter cake is an important property of the drilling fluid and can affect the success of drilling operations. This research focuses oncharacterizatingthe filter cakes produced by Ca-bentonite-based drilling fluid contains ferric oxide NPs at downhle conditions. A combination of computed-tomography (CT) scan and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used in filter cake characterization. The effect of NP concentration, fluid preparation method, and filtration condition were studied. A HP/HT filter press was used to perform the filtration process at conditions up to 350°F and 500 psi. Indiana limestone core disks were used to simulate the filter media. The experimental results showed that the ferric oxide NPs improve the filter cake and filtration properties of Ca-bentonite-based drilling fluid in the presence of polymer and other additives. Low NP concentration is preferred for obtaining a good cake quality with the best characteristics obtained at 0.3–0.5 wt% NPs. Furthermore, this drilling fluid can withstand conditions up to 500 psi and 350°F. Cake properties of 0.151 in. thickness, 6.9 ml filtrate volume, and 0.428 µd permeability was obtained at such conditions. The addition of NPs to the drilling fluid improved the filter cake properties under both static and dynamic filtration. SEM-EDS analysis confirmed the efficiency of using NPs to form a smoother/less porous filter cake morphology. Moreover, sonication for one hour and hydration for 16 hours are recommendedfor better preparation of these fluids. This research provides an experimental evaluation of using ferric oxide NPs with Ca-bentonite-based drilling fluid to produce high-quality filter cake at downhole conditions. The characteristics of the filter cake gererated confirmed the efficiency of such fluids.</jats:p

CFD Simulation of Pressure Losses in Eccentric Horizontal Wells

Abstract In the oil and gas industry, various methods involving Computation Fluid Dynamics (CFD) are used to predict pressure losses while cleaning/operating horizontal drilling facilities with non-Newtonian fluids. Studies on the factors which influence such predictions are important to the successful design, development and operation of wellbores. The effects of hydrodynamic roughness along with eccentricity and rotational speed of a drill pipe are evaluated in the present study. Simulations are conducted using the commercial CFD code, ANSYS CFX 16.2 and the results are validated using experimental data. The current research shows that the pressure losses are strongly dependent on the equivalent roughness of a drilling annulus and, eccentricity and rotational speed of the drill pipe. The knowledge gained from this project is beneficial for designing, operating and troubleshooting drilling facilities.</jats:p