Fluxes between fractured-karstified and detritic aquifers are commonly poorly understood in many environments. These two types of aquifers are in contact in the southeastern Pampean region in the ...Argentine Buenos Aires province, and the aim of this work is to analyze their relationship contributing to improve the hydrological model. A joint application of hydrochemical and multi-isotope (δ
2
H, δ
18
O, δ
13
C-TDIC, δ
18
O-TDIC,
87
Sr/
86
Sr) tools was used. TDIC, δ
2
H, δ
18
O and δ
13
C-TDIC allowed differentiating two main end members. Water in the Pampeano aquifer (PA) which is transferred from the fractured-karstic aquifer (F-KA) is characterised by high TDIC around 500-700 mg/L, isotopically depleted in
18
O (about −5.5 ‰) and high δ
13
C-TDIC (around −10.0 ‰). The other end member is direct recharge water infiltrated into the PA with TDIC ranging from 400 to 500 mg/L, slightly enriched in
18
O (δ
18
O = −4.8 ‰), and δ
13
C-TDIC in the range of soil CO
2
as a result of reactions with calcrete concretions (from −20.0 to −9.0 ‰). Dolomite dissolution is the main process controlling the chemistry of the low-mineralized (Mg-Ca-HCO
3
) waters, whereas high-mineralized (Na-HCO
3
) waters are strongly influenced by ion-exchange reactions with adsorbed Ca
2+
and Mg
2+
and by evaporation.
Los Molles Formation (Lower to Middle Jurassic), deposited under the first marine event above the synrift continental deposits of the Precuyo, is the second most important source rock of the Neuquén ...Basin after Vaca Muerta Formation. Los Molles Formation extends over more than 45,000 km2 and can be recognized in different geographic areas within the basin.
Los Molles Formation, with a thickness that varies from 100 to 800 m, has a total organic content (TOC) ranging from 1 to 5%, vitrinite reflectance (%Ro) 0.8 to 2, Hydrogen Index 300–500 mg HC/gTOC, SPI of 6 t HC/m2, kerogen type II-III and a VKA of algal amorphous with variable terrestrial contribution. In the studied area, the unit is subdivided into three members, with different characteristics that reflect distinctive sedimentary environments from shallow marine to deltaic.
In addition to its condition of source rock, conventional and unconventional shale and tight reservoirs are currently being developed mainly within the vicinity of the depocenter of the basin, mostly related to gas prone basin centered gas systems. Volume estimation assigns 190 to 270 TCF of gas to this formation and 3.7 BBO.
Outcrops, three cores and fifteen wells with open hole logs consist of the database for this study. Deductive methodologies were used to characterize the formation with standard log analysis that consist of differentiating reservoir to non-reservoir rocks, sandstones, silt, tuff, clay, porosity, water saturation, permeability, TOC, Young's modulus, Poisson's ratio and brittleness index. Inductive methodologies (clustering) were used for determining electrofacies that correspond to: Sp, sand, medium to very coarse, may be pebbly, solitary or grouped; Sh, sand very fine to very coarse, may be pebbly, horizontal lamination; Fm, mud, silt, massive; and Gm, massive or crudely bedded gravel, horizontal bedding, imbrication.
The results of this study demonstrate the importance of taking advantage of different techniques when studying elements of the petroleum system related to Los Molles Formation.
•Source rocks and unconventional shale reservoirs represent an extremely interesting target due to the volume of resources.•Deductive and inductive methodologies together with geomechanics and electrofacies provided to be particularly useful.•Data integration from outcrops, cores and open hole logs are crucial to characterize rocks and petrophysical parameters.•The described workflow can be easily adapted to be applied in similar formations.
A new Triassic tetrapod track assemblage recorded from levels of the Cuyana Basin (west-central Argentina) is described. The tracks came from multiple track-bearing horizons of the Upper Triassic ...(Carnian) Portezuelo Formation that indicate recurrent playa to mudflat conditions in a marginal lacustrine succession. This footprint assemblage is the most important one described up to now for the lower Mesozoic of South America, and forms a significant estimate of the fauna represented during that time in the region. Therefore, in order to understand the faunal significance of the assemblage, the track-makers were identified within a phylogenetic context. Although at a coarse taxonomic level, this analysis indicates the presence of non-mammalian therapsids (small cynodonts and large dicynodonts) and a quite diverse archosaur fauna that includes members of both crurotarsal archosaurs and dinosaurs (sauropodomorphs and theropods). Comparisons between the studied assemblage and other Early Mesozoic tetrapod track records from Gondwana suggest close relationships with those described from the Upper Triassic of the Karoo Basin in South Africa. In addition, the presence of putative basal sauropodomorph dinosaur tracks in the Portezuelo levels suggests that the stratigraphic range of the group extends back into the Carnian, farther than that documented by the known body-fossil record of the group in western Gondwana.
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.
The decarbonization of the energy sector is a major global challenge, requiring the transformation and improvement of energy production systems to reduce greenhouse gas emissions. The hydrocarbon ...industry offers a potential pathway for transition, as many productive hydrocarbon deposits with a high water cut are increasing over time. The geothermal energy contained in the co-produced water, which is transported to the surface by pumping, can be harnessed for a wide range of applications, depending on the temperature of the extracted fluid.
The use of the energy contained in produced water is considered one of the most promising proposals for extending the economic life of hydrocarbon reservoirs with low enthalpy geothermal resources, characterized by temperatures below 90 °C. This is facilitated by the existing infrastructure in the fields, which enables the installation of heat extraction equipment, thereby reducing the high costs associated with the drilling and completion stages of the wells and eliminating the related risks.
This work aims to evaluate the potential for generating electrical energy using an “Organic Rankine Cycle” (ORC) system from the heat contained in the produced water of Bandurria Centro and Bajo del Toro Norte hydrocarbon reservoirs, situated on the Eastern Flank of the Neuquén Basin. According to the results, the produced water temperatures in the aforementioned areas are deemed suitable for the application of an ORC system, enabling the transfer of thermal energy to generate electricity and thus be used within the field. Maximum power outputs of up to 6.611 kW were observed for produced water temperature of 62.55 °C with an ambient temperature of 5.5 °C. However, the extreme ambient temperatures of 39 °C made it impossible for the ideal ORC system to remain operational. Therefore, the use of energy contained in the produced water through the implementation of an ORC system is a promising approach for extending the economic life of hydrocarbon deposits and contributing to decarbonization efforts.
•Global decarbonization requires transforming energy production to reduce emissions.•Hydrocarbon industry has transition potential as high water cut deposits increase.•Produced water can yield geothermal energy for various uses based on temperatures.•ORC systems effectively harness produced water energy, generating up to 6.611 kW.•Ambient temperature plays key role in power production.
The lithostratigraphic units that conform the Sorocayense Group and fill the Sorocayense-Hilario sub-basin represent an alluvial-fluvial-lacustrine succession with significant volcanic supply during ...its deposition. They are namely the Cerro Colorado del Cementerio, Agua de los Pajaritos, Monina, Hilario and El Alcázar formations and present several carbonate levels. The genesis, diagenesis, and main controlling factors on continental carbonates present a means to understand basin evolution through the study of their petrography and chemical elemental composition through cathodoluminescence techniques. We have identified six microfacies: a) homogeneous micrite, b) bioclastic micrite, c) dolomicrite, d) laminated micrite, e) oncolitic packstone, and f) sparitic carbonate. Among these microfacies, six cementation and alteration phases have been identified: a) micritization, b) mechanical compaction, c) calcitic cementation, d) sparitic cementation, e) microsparitic cementation, and f) chemical compaction. This analysis allowed establishing a chronology of the diagenetic modifications undergone by the carbonates. Results support diagenesis was controlled mainly by tectonics showing major impact in carbonate facies identified at the flexural margin of the rift. The effect would have been linked to exertion of a paleohydrological effect favoring lateral meteoric water migration through faulting. The presence of dolomite in some of the microfacies is linked to the presence of montmorillonite as the dominant Mg-rich-phyllosilicate in clay assemblages most likely acting as the potential source. In turn, Mg is more likely to be replaced by Mn leading to luminescent carbonate microfacies.
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.
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.
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 Neuquén 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.
•Different workflows have been presented to perform isotropic and anisotropic geomechanical models.•A strict comparison between elastic models is proposed.•The (DAEM) proves to be an adequate tool to perform a geomechanical model, but still requires calibration points to be more precise.•The (AEM) gives a good approximation for the entire Vaca Muerta Formation, without lithology discrimination.•The (IEM) should be taken carefully, as a simple quick view.
Extensional processes that followed the Gondwanan Orogeny rise to the development of a series of rift basins along the continental margin over older accreted Eopaleozoic terranes. Stratigraphic, ...structural, paleontological, and isotopic studies are presented in this work in order to constrain the ages of the sedimentary infilling and to analyze the tectosedimentary evolution of one of the Cuyo basin depocenters, known as Rincón Blanco. This asymmetrical half-graben was filled by continental sediments under a strong tectonic control. The infilling was strongly controlled by tectonics which in term produced distinctive features along the whole sedimentary sequence. Using a combination of lithological and structural data the infilling was subdivided into packages of genetically linked units bounded by regional extended surfaces. Several tuffs and acid volcanic rocks have been collected across the whole section of the Rincon Blanco sub-basin for SHRIMP and LA-MC-ICPMS U–Pb zircon dating. The ages obtained range from 246.4±1.1Ma to 230.3±1.5Ma which is the time elapsed for the deposition of three tectono-sequence units separated by regional unconformities and mainly constrained to the Middle Triassic. They are interpreted as a result of a reactivation of the extensional system that has evolved along strike as segments of faults that linked together and/or as laterally propagating faults. Regional correlation with coeval rift basins permits to establish north-south propagation in the extensional regime along the western margin of SW Gondwana. This trending started in the lowermost Triassic and extended until the latest Triassic. Two of them were precisely correlated with Cerro Puntudo and Cacheuta half-graben systems. The new data indicate that the three sequences were mostly deposited during the Middle Triassic (246 to 230Ma), with no evidence of sedimentation during Norian and Rhaetian, which is in conflict with some previous biostratigraphic studies.
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► The Rincón Blanco depocenter is a Triassic rift basin associated with the Pangea breakup. ► SHRIMP and LA-MC-ICPMS U–Pb zircon dating of different levels of the sequence constrain sedimentation to the Middle Triassic. ► A new temporal framework for the basin questions previous ages assigned to regional stratigraphic correlations among different basins based on fossil floras.
