Artículos de publicaciones periódicas

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Relationship between fissility, composition, rock fabric and reservoir properties in Vaca Muerta Formation (Neuquén Basin, Argentina): from outcrop to subsurface core data
(2022-05) Martín, Lucía Inés; Marchal, Denis; Barredo, Silvia; Naides, Claudio; Blanco Ibáñez, Silvia
"The fissility is the ability of some rocks to split along relatively smooth surfaces parallel to the bedding. This property observed mostly in fine-grained rocks is particularly expressed in outcrops, where rocks are subjected to weathering processes. Most authors associate the fissility to the abundance of clay minerals and their orientation parallel to the bedding. The horizontal fabric can be promoted by depositional conditions such as sediment composition, quantity of total organic carbon content (TOC) and depositional mechanisms, giving rise to a primary fissility. Alternatively, the alignment of platy minerals can be linked to the burial history of the rock, by processes such as mechanical compaction or secondary mineral growth, resulting in a secondary fissility. The present study aims to identify the main controls of fissility development at the micro- and macroscopic scale in rocks of the Vaca Muerta Formation exposed in the Cerro Mulichinco area and in a 121-meter-long core extracted from a well within the Neuquén Basin. In outcrops, fissility is related to fine-grained laminated facies with low carbonate content, revealing the strong control exerted by lithology. The TOC measurements allow establishing a positive correlation between organic matter content and fissility intensity. Moreover, the analysis of the transgressive-regressive cycles shows that fissility is higher around the maximum flooding surfaces. Regarding their mechanical characteristics, the different interfaces observed in core are classified into first and second-order, the last one including fissility planes. Some of these interfaces evolve from potential (partially open) to effective (totally open) discontinuities in response to changes of stress conditions during the core extraction and due to the stress relaxation through time: weeks (T1), months (T2) and years (T3) after extraction. The time evolution of the effective core discontinuities points out rock intervals that are variably broken and core segments that remain intact. The Drying Alcohol Discontinuities (DAD) methodology reveals potential discontinuities within apparently intact core segments. By using this technique, a 4-class index is established as a proxy for fissility degree. When integrated with geological, petrophysical and geomechanical data, this index enables characterizing the main mechanisms controlling rock fissility that express through discontinuities promoting the loss of competence of a rock. Consequently, this mechanical property is considered to influence the efficiency of hydraulic fracture in shale reservoir completion."
Evaluation of silicone fluids and resins as CO2 thickeners for enhanced oil recovery using a computational and experimental approach
(2021-09) Gallo Jiménez, Gonzalo Augusto; Erdmann, Eleonora; Cavasotto, Claudio N.
"CO2 thickeners have the potential to be a game changer for enhanced oil recovery, carbon capture utilization and storage, and hydraulic fracturing. Thickener design is challenging due to polymers’ low solubility in supercritical CO2(scCO2) and the difficulty of substantially increasing the viscosity of CO2. In this contribution, we present a framework to design CO2 soluble thickeners, combining calculations using a quantum mechanical solvation model with direct laboratory viscosity testing. The conductor-like polarizable continuum model for solvation free-energy calculations was used to determine functional silicone and silsesquioxane solubilities in scCO2. This method allowed for a fast and efficient identification of CO2-soluble compounds, revealing silsesquioxanes as more CO2-philic than linear polydimethylsiloxane (PDMS), the most efficient non-fluorinated thickener know to date. The rolling ball apparatus was used to measure the viscosity of scCO2 with both PDMS and silicone resins with added silica nanoparticles. Methyl silicone resins were found to be stable and fast to disperse in scCO2 while having a significant thickening effect. They have a larger effect on the solution viscosity than higher-molecular-weight PDMS and are able to thicken CO2 even at high temperatures. Silicone resins are thus shown to be promising scCO2 thickeners, exhibiting enhanced solubility and good rheological properties, while also having a moderate cost and being easily commercially attainable."
Analyzing a suitable elastic geomechanical model for Vaca Muerta Formation
(2017-11) Sosa Massaro, Agustín; Espinoza, D. Nicolas; Frydman, Marcelo; Barredo, Silvia; Cuervo, Sergio
"Accurate geomechanical evaluation of oil and gas reservoir rocks is important to provide design parameters for drilling, completion and predict production rates. In particular, shale reservoir rocks are geologically complex and heterogeneous. Wells need to be hydraulically fractured for stimulation and, in complex tectonic environments, it is to consider that rock fabric and in situ stress, strongly influence fracture propagation geometry. This article presents a combined wellbore-laboratory characterization of the geomechanical properties of a well in El Trapial/Curamched Field, over the Vaca Muerta Formation, located in the Neuquen Basin in Argentina. The study shows the results of triaxial tests with acoustic measurements in rock plugs from outcrops and field cores, and corresponding dynamic to static correlations considering various elastic models. The models, with increasing complexity, include the Isotropic Elastic Model (IEM), the Anisotropic Elastic Model (AEM) and the Detailed Anisotropic Elastic Model (DAEM). Each model shows advantages over the others. An IEM offers a quick overview, being easy to run without much detailed data for heterogeneous and anisotropic rocks. The DAEM requires significant amounts of data, time and a multidisciplinary team to arrive to a detailed model. Finally, an AEM suits well to an anisotropic and realistic rock without the need of massive amounts of data."
Facies volcaniclásticas del ciclo precuyano en el sector norte de la sierra de la Cara Cura, Mendoza
(2017) Drosina, Marina del Valle; Barredo, Silvia; Martínez, Amancay; Giambiagi, Laura
"Las rocas correspondientes al ciclo Precuyano, afloran en la sierra de la Cara Cura, sur de la provincia de Mendoza. Es una secuencia volcano-sedimentaria de 419 m de espesor, constituidos por rocas volcánicas y piroclásticas de composición andesítica que se intercalan con conglomerados, areniscas y pelitas moradas. En esta contribución se presentó una sección estratigráfica del ciclo Precuyano y se realizó un análisis de facies de la unidad. En el área de estudio, el relleno de la misma se caracterizó por el desarrollo de sistemas volcánicos integrados por depósitos de flujos piroclásticos, flujos de bloques y cenizas y coladas lávicas y en menor proporción por depósitos de abanicos aluviales. Los rasgos estructurales de la serranía son controlados por la existencia de anisotropías preexistentes en el basamento que controlaron el desarrollo de las estructuras del rift."
Petrofísica básica de los depósitos del ciclo precuyano, sierra de la Cara Cura, Mendoza
(2017) Drosina, Marina del Valle; Barredo, Silvia; Stinco, Luis; Giambiagi, Laura; Migliavacca, Osvaldo
"En este trabajo se analiza la sucesión aflorante en el sector norte de la Sierra de la Cara Cura conformada por rocas volcaniclásticas pertenecientes al Ciclo Precuyano. Estos depósitos se caracterizan por la presencia de niveles de brechas masivas monomícticas de hasta 15 m de espesor que intercalan niveles de rocas volcánicas de entre 5 y 8 m de espesor. El análisis integral de las muestras recolectadas, permitió obtener los valores de porosidad y permeabilidad de depósitos de bloques y cenizas y flujos lávicos de composición andesítica para determinar su potencial como roca reservorio de yacimientos convencionales. La porosidad total observada al microscopio es pobre, menor al 5% para las rocas ígneas y de un 7 % para las rocas volcaniclásticas. De los estudios de laboratorio se pudieron obtener valores de porosidad efectiva y permeabilidad al gas, comprendidos entre 9,7 y 21,46% y 0,288 y 1,339 mD en los depósitos volcaniclásticos y de entre 8,6 y 19,5% y 0,009 y 0,014 mD en los flujos lávicos. En función de estos resultados se pudo caracterizar la porosidad, analizar su origen e interpretar los factores que la pudieron modificar. Se comprobó que el espacio poral para muestras de afloramiento de los niveles ígneos resulta fundamentalmente de los procesos que afectaron a estas rocas durante su emplazamiento y posterior diagénesis (primeramente fracturación y alteración de minerales). Se estimó que un 70% del volumen total de porosidad en la roca ígnea corresponde a poros secundarios, mientras que el 30% restante son primarios. La porosidad secundaria está dada por la presencia de fracturas, tanto de origen tectónico como hidrotermal, y a procesos de disolución, mientras que la porosidad primaria se debe a la presencia de disyunciones columnares, vesículas en las coladas lávicas y alteración mineral. Las rocas volcaniclásticas presentan un 80% de porosidad secundaria asociada a fracturas de origen tectónico y a procesos de disolución mientras que el 20 % restante corresponde a porosidad primaria asociada a vesículas y a una incipiente disyunción columnar. Este estudio se enfocó en definir los procesos que posibilitaron a rocas ígneas y volcaniclásticas poseer características de reservorios, como posible herramienta para definir zonas favorables dentro de los cuerpos rocosos para el almacenamiento y vías de migración de los hidrocarburos. Se concluye que las facies piroclásticas asociadas a los flujos de bloques y cenizas presentan las mejores propiedades de reservorio en esta localidad, a la vez que la porosidad que predomina es del tipo secundaria, generada por microfracturación y por la disolución de componentes. En este trabajo se propone la existencia de dos tipos de reservorios en los depósitos estudiados del Precuyano, el primero, constituido por los depósitos de bloques y cenizas, donde este sistema poroso-permeable podría ser comparable a aquellos de origen carbonáticos fracturados, mientras que el segundo está representado por las coladas andesíticas que se comportan como un reservorio fisurado."
Cellulose nanoﬁbrils as a replacement for xanthan gum (XGD) in water based muds (WBMs) to be used in shale formations
(2018-12) Villada, Yurany; Iglesias, María Celeste; Casis, Natalia; Erdmann, Eleonora; Peresin, María Soledad; Estenoz, Diana
"In this work, the potential replacement of xanthan gum (XGD) by cellulose nanofibrils in the composition of water based muds (WBMs) was studied. Bleached (B-CNF) and unbleached (L-CNF) cellulose nanofibrils, mainly differentiated by their lignin content, were tested and their performances were compared with that of XGD. The effects of cellulose nanofibrils on the rheological and filtration properties of WBMs were investigated. Rheometric analysis showed a shear-thinning behavior more noticeable for fluids containing B-CNF and XGD, while filtration properties were improved using L-CNF. The Sisko model was used to determine rheological parameters. Finally, it was found that by replacing XGD by double concentration of L-CNF in a WBM for Argentina shale, similar rheological properties were obtained. Structural changes were assessed by using Scanning Electron Microscopy (SEM). Particles agglomeration and good film formability were observed. Furthermore, WBMs with lignin-containing cellulose nanofibrils exhibited a better thermal stability after aging."
Estratigrafía mecánica de detalle aplicada al modelado geomecánico elástico anisotrópico en la formación Vaca Muerta
(2018) Sosa Massaro, Agustín; Frydman, Marcelo; Barredo, Silvia
"La evaluación geomecánica detallada de las rocas en un yacimiento hidrocarburífero es de suma importancia para proporcionar parámetros elásticos que permitan diseñar estrategias de perforación y terminación, como así también, predecir las tasas de producción de un pozo petrolero, a partir del conocimiento del volumen de roca estimulado. En particular, las secuencias compuestas por pelitas, margas y carbonatos con altos contenidos orgánicos, muestran ser textural y Mineralógicamente heterogéneas. Los pozos que atraviesan estas rocas necesitan ser fracturados hidráulicamente para su estimulación. En entornos tectónicos complejos, la fábrica de la roca y los regímenes de esfuerzos in situ, influirán fuertemente en la geometría de propagación de la fractura. Este trabajo presenta una caracterización combinada entre datos de pozo y laboratorio de las propiedades geomecánicas de la concesión El Trapial, utilizando información de cuatro pozos con interés sobre la Formación Vaca Muerta, de la Cuenca Neuquina, Argentina. El estudio utiliza los resultados de pruebas triaxiales con medidas acústicas en testigos de roca obtenidos de coronas de pozo, generando correlaciones dinámicas a estáticas sobre la base del modelo elástico anisotrópico detallado (MEAD). Tal modelo, muestra ventajas sobre el modelo elástico isotrópico (MEI), ideal para una visión general rápida, y el modelo elástico anisotrópico (MEA), con buena adaptación a rocas heterogéneas y anisotrópicas, pero sin discriminación de las diversas facies de la roca."
Multi-objective optimization of a CO2-EOR process from the sustainability criteria
(2018-01) Gutiérrez, Juan Pablo; Erdmann, Eleonora; Manca, Davide
"Aim of this article is to estimate and discuss the economic and environmental impacts for the obtainment of CO2 in such conditions to be injected as enhanced oil recovery (EOR) fluid. Particularly, this study focuses on the compression sector design needed to process the CO2 coming from an already existing absorption plant. Currently, 18.68 kmol/h of a high-purity CO2 stream may be used for injecting and increasing the production of a pilot crude oil well near the location of the industrial plant. However, it is still necessary to perform an economic evaluation to quantify the investment and the operating costs that the compression involves..."
Steady-state energy optimization and transition assessment in a process of CO2 absorption from natural gas
(2018-09) Gutiérrez, Juan Pablo; Tarifa, Enrique E.; Erdmann, Eleonora
"An industrial-scale MDEA-based CO2 absorption process is considered in this work. Natural gas plant of Aguaragüe Argentina is selected to perform the studies of optimization and dynamics. With the steadystate of the process simulated, the reboiler energy demand of the plant is optimized in Aspen Hysys v8.8. In this optimization study, we analyze the base case (current) conditions of the reference plant and also six disturbance scenarios. According to the results, the main energy requirement can be reduced in more than a 48%, with the current process design. In the second part of our work, the plant is simulated in dynamic mode with the aim of characterizing the transition towards the found optimal conditions. It is proved that the dynamic model can reproduce the specified values after a short-time. In addition, the absence of undesirable states during the stabilization proves that the current control scheme is appropriate to minimize the energy consume in the plant under study."
Evaluación reológica de fluidos de perforación base agua con nanosílice
(2018-07) Gallardo, Felipe Eusebio; Erdmann, Eleonora; Abalos, Roxana
"La creciente demanda hidrocarburífera ha llevado al estudio y producción de reservorios no convencionales de tipo shale en Argentina y el mundo. Este tipo de formaciones sedimentarias de estructura laminar, están conformadas por partículas consolidadas del tamaño de las arcillas, poseen nanoporos y baja permeabilidad. Durante la perforación del shale con WBM se debe garantizar la estabilidad de las paredes del pozo controlando la inhibición de las arcillas presentes y el incremento de la presión poral ocasionado por el ingreso de fluido a la formación. Para este último propósito, en este trabajo, se seleccionó nanosílice de 12 nm, la cual obtura los poros del shale que tienen un tamaño promedio de 30 nm. Se busca de esta forma reducir el ingreso de fluido a la formación, la presión poral, la permeabilidad y minimizar la interacción roca-fluido."
Functional characterization on colloidal suspensions containing xanthan gum (XGD) and polyanionic cellulose (PAC) used in drilling fluids for a shale formation
(2016) Villada, Yurany; Gallardo, Felipe Eusebio; Erdmann, Eleonora; Casis, Natalia; Olivares, Laura; Estenoz, Diana
"Drilling fluids are employed in the operation of hydrocarbon exploitation. Two kinds of drilling fluids are commonly used: water based muds and oil based muds. The oil based muds are characterized by their high performance in unconventional reservoirs due to the very low interaction with the reactive formation. Their environmental impact promotes the design of water based muds that present low toxicity. In this paper a water based mud for shale formation with similar rheological characteristics to the oil based mud used in the oil industry of Argentina was designed and the effect of xanthan gum and polyanionic cellulose on the main functional characteristics was studied. Rheometric analysis showed a shear-thinning behavior with notable effect on the concentration of polymers. After dynamic aging test, fluids with composition of PAC=8.00 g/L and XGD =3.00 g/L exhibited rheological properties very close to oil base mud. Structural changes were assessed from optical microscopy and scanning electron microscopy. Particles agglomeration due to the presence of polymers was observed. Furthermore, mud filtration essays allowed to evaluate the performance of PAC as control agent. The Carreau model and statistical analysis were used to determine rheological parameters."

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