Klie, Hector (DeepCast.ai) | Klie, Arturo (DeepCast.ai) | Rodriguez, Adolfo (OpenSim Technology) | Monteagudo, Jorge (OpenSim Technology) | Primera, Alejandro (Primera Resources) | Quesada, Maria (Primera Resources)
The Vaca Muerta formation in Argentina is emerging as one of the most promising resources of shale oil/gas plays in the world. At the current well drilling pace, challenges in streamlining data acquisition, production analysis and forecasting for executing timely and reliable reserves and resource estimations will be an overarching theme in the forthcoming years. In this work, we demonstrate that field operation decision cycles can be improved by establishing a workflow that automatically integrates the gathering of reservoir and production data with fast forecasting AI models.
We created a data platform that regularly extracts geological, drilling, completion and production data from multiple open data sources in Argentina. Data cleansing and consolidation are done via the integration of fast cross-platform database services and natural language processing algorithms. A set of AI algorithms adapted to best capture engineering judgment are employed for identifying multiple flow regimes and selecting the most suitable decline curve models to perform production forecasting and EUR estimation. Based on conceptual models generated from minimum available data, a coupled flow-geomechanics simulator is used to forecast production in other field areas where no well information is available. New data is assimilated as it becomes available improving the reliability of the fast forecasting algorithm.
In a matter of minutes, we are able to achieve high forecasting accuracy and reserves estimation in the Vaca Muerta formation for over eight hundred wells. This workflow can be executed on a regular basis or as soon as new data becomes available. A moderate number of high-fidelity simulations based on coupled flow and geomechanics allows for inferring production scenarios where there is an absence of data capturing space and time. With this approach, engineers and managers are able to quickly examine a feasible set of viable in-fill scenarios. The autonomous integration of data and proper combination of AI approaches with high-resolution physics-based models enable opportunities to reduce operational costs and improving production efficiencies.
The integration of physics-based simulations with AI as a cost/effective workflow on a business relevant shale formation such as Vaca Muerta seems to be lacking in current literature. With the proposed solution, engineers should be able to focus more on business strategy rather than on manually performing time-consuming data wrangling and modeling tasks.
Tomassini, Federico Gonzalez (YPF SA) | Smith, Langhorne (Taury) (SmithStrata) | Rodriguez, Maria Gimena (YPF SA) | Kietzmann, Diego (University of Buenos Aires - CONICET) | Jausoro, Ignacio (YPF Tecnología SA [Y-TEC]) | Floridia, Maria Alejandra (YPF Tecnología SA [Y-TEC]) | Cipollone, Mariano (YPF Tecnología SA [Y-TEC]) | Caneiro, Alberto (YPF Tecnología SA [Y-TEC]) | Epele, Bernarda (YPF Tecnología SA [Y-TEC]) | Santillan, Nicolas (YPF Tecnología SA [Y-TEC]) | Medina, Federico (YPF Tecnología SA [Y-TEC]) | Sagasti, Guillermina (YPF SA)
The objective of this work is to present the pore types and their relationship to the main core facies from the Vaca Muerta Formation, Neuquén Basin, Argentina. With an in-house methodology for focused Ion Beam scanning electron microscope (SEM) images and petrographic analysis, a linked to increase the understanding of the pore systems, mineralogy, diagenetic features, grain types and facies variations is carried out. Long continuous cores from two wells were described in detail by standard facies analysis and SEM for semi-quantitatively estimating total porosity, relative abundance of pore types and pore sizes, mineralogy, relative abundance of kerogen and migrated bitumen, type and origin of different clays, and diagenetic quartz abundance among other features. The SEM porosity, organic matter content and mineral distribution correlates favorably with independent measurements obtained by other labs methods. The findings were linked to the core descriptions and the regional sequence stratigraphic framework to predict best reservoir facies. This prediction is done with the production results for each horizontal well in the different landing zones. Finally, the understanding of the pore system can be used to define the best areas and intervals where horizontal wells can be geosteered during the development stage of a block.
The Tithonian-Valanginian (Upper Jurassic-Lower Cretaceous) Vaca Muerta Formation is the main source rock of the Neuquén Basin (Figure 1). The Vaca Muerta Fm. is a lower slope and basinal facies equivalent to the updip Quintuco and Loma Montosa Formations. This formation is a very appealing target for unconventional development due to its vast lateral extent, great thickness (up to 500 m – 1640 ft), relatively high values of total organic carbon (TOC 2-10 %), thermal maturity (oil to dry gas windows), mineralogical composition (less than 30% clay), overpressure and relatively simple structural setting. The study area is located in the center of the Neuquén Basin (Figure 1), north of the Huincul high and mainly in the Añelo depocenter where major activity is taking place. More than 600 horizontal wells have been drilled in the basin in different landing zones resulting in different hydrocarbon production. The EIA (2013) estimated that the technically recoverable resources estimated for this formation are in the order of 300 Tcf of gas and 16 Bbbl of oil and these numbers may be low.
The thermal maturity of organic-rich mudstones is one of the main parameters to evaluate, when appraising a new area in an unconventional shale play project, to decide on the best field development strategy and to define the landing zones. Conventionally, thermal maturity is derived from optical vitrinite reflectance measurements, but this technique has some limitations in marine sediments with lack of terrestrial material. Other techniques, such as Rock-Eval pyrolysis, are destructive and the results can be biased if oil-based mud is used to drill the well. In this contribution, a fast, easy and non-destructive method known as Raman spectroscopy is proposed to estimate the maturity of mudstone samples from the Argentinian Vaca Muerta formation, collected from a wide range of maturities.
Raman spectroscopic measurements were executed on a variety of Vaca Muerta shale samples. A complete maturity depth profile was acquired for one well over the entire Vaca Muerta organic shale sequence. Additionally, samples from eight further wells, presenting a wide range in the expected maturity, were examined with the Raman technique. Using a correlation between the Raman spectroscopic signal and vitrinite reflectance, established earlier based on a set of reference samples, containing organic-rich mudstones from a variety of paleo-marine sedimentary basins in North America, thermal maturities were derived for the Argentinian shale samples. For certain samples kerogen was extracted and properties of the isolated kerogen were measured. The Raman results were not only compared to standard maturity indicators such as vitrinite reflectance or Rock-Eval pyrolysis, but also with other non-standard techniques like DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) or results derived from the kerogen properties.
This case study in the Vaca Muerta shows a good correlation between the maturity values derived from the Raman measurements and maturities inferred from other methods. The depth profile shows a trend of increasing maturity with depth as expected for such a thick unconventional reservoir.
In contrast to other techniques that require isolation of kerogen, polishing of the sample surfaces, or even crushing of the samples in addition to excessive cleaning, the Raman technique utilized here was applied directly on core chips with minimal sample preparation. This non-destructive technique is fast and easy, while the accuracy is comparable to other techniques like infrared spectroscopy, kerogen skeletal density, or optical vitrinite reflectance measurements. The simplicity and accuracy of the Raman technique can provide critical information about vertical and lateral variability of thermal maturity at basin scale in a short period of time, helping to understand the burial history and its relationship with the variability of hydrocarbon properties.
Mandler, Holger (Shell International Exploration and Production) | Gonzalez, Yvonne (Shell International Exploration and Production) | Kruijs, Ed (Shell International Exploration and Production) | Fita, Patricio (Shell International Exploration and Production)
This paper is a current case study from the Vaca Muerta play (Neuquen basin, Argentina) in Shell1‘s shales portfolio. It describes the interdisciplinary approach taken, to efficiently de-risk the play and progress three blocks to Final Investment Decision (FID), discussing key types of data and analyses, as well as the requirement to drive cost improvements during the early appraisal stages, which is paramount to achieve competitive project economics. In addition, an overview of remaining technical uncertainties and challenges for development is provided, together with the ongoing efforts to optimize the field development plan in the coming years.
The Neuquén basin is located in northern Patagonia region, immediately East of the Andean Cordillera. It covers roughly 30,000km2 and is the most prolific onshore basin in Argentina. Significant hydrocarbon volumes have been produced from conventional fields since first oil discovery a century ago. The Vaca Muerta shale is the major source rock within the basin, which has been recognized by the AAPG as one of 25 “Global Super Basins”. The Vaca Muerta Formation represents the distal sector (bottomset and foresets) of the Quintuco-Vaca Muerta system which is part of the Lower Mendoza Group. The Lower Mendoza group represents a rapid and widespread transgression, following the deposition of the continental Tordillo Formation, from mid Tithonian to Early Berriasian (Legarreta and Gulisano, 1989). It consists of alternating black shales and limestones, ranging in thickness across the basin from roughly 25 meters in the south to 500 meters in the north. Based on regional seismic, the system can be sub-divided into seven third-order, prograding depositional sequences. The play fairway is located within the lower slope to basinal environment of each of these sequences, where the optimum combination of preserved organic content and clastic input produces a world class shale oil reservoir. Over a large play area, sweet spots for multiple sequences are stacked, resulting in double digit average porosities, high Total Organic Content (TOC) and low water saturation over vertical intervals of hundreds of meters. The play is self-sourced and, across the play fairway, hydrocarbon maturities range from the black oil window, in the East and South, to dry gas, in the West and North. Significant overpressures are present over the entire maturity range.
Drilling multiple horizontal wells from a single pad has become a common approach in many shale plays in response to the economic, real estate, water management, regulations challenges the operators face while developing such plays. The challenge of optimizing the landing zones of those wells depends, in part, on the knowledge of the Stimulated Rock Volume (SRV) created during the fracturing jobs and the ability to predict its evolution during production. The objective of this work is to show how to get this understanding through a multidisciplinary workflow and how this helps to optimize a multi-landing zone development in a field case in Vaca Muerta.
The first part of this work presents a sensitivity study in a single-well, focusing on the key geological and geomechanical factors with ranges based on data collected from well logs and field observations. These include characteristics of the natural fracture network, facies, laminations, variations on petroelastic properties and principal stresses, and anisotropy. The impact of these parameters upon the geometry of the SRV and well productivity is presented using pseudo-3D fracture model and fluid flow-geomechanics simulation coupling technique. Once the key parameters affecting SRV geometry and productivity are determined, the second part of this work shows the results of multi realization (multiple scenarios and well landings) on green and brown field stimulations.
Analysis of the SRV geometry under undepleted and depleted conditions suggests that the stress change associated to production does impact the overall SRV generation and must be considered for multi-well multi-layer strategy. Horizontal Stress Anisotropy, preexisting fractures and laminations are the static properties which have the most important control on the Stimulate Rock Volume (SRV) dimensions and complexity. The SRV is dynamic, changes during time. Addressing these changes allows us to better plan a multi-landing zone design (sequence, landing depth, well spacing, etc.) at a given period of time for this field case. The presented work goes beyond an ordinary investigation of SRV creation driving properties: it allows for a better understanding of uncertainties related to these properties and ultimately depicts the static and dynamic impact on production in order to guide the optimization of well placement on the field case development.
The results of an investigative research study on the impact of the in-situ stress, shale matrix composition, maturity, amount of organic matter and clay composition affecting the anisotropy level of the geomechanical properties have been discussed in this paper. These parameters are among the key factors known to control the geomechanical properties in organic-rich shale formations. Organic-rich shale formations with different mineralogical compositions and organic matter maturity have been measured under uniaxial and triaxial stress state along with the field data from limited number of the wells in these shale basins where the core samples are obtained to investigate the role of each factor on the level of geomechanical anisotropy.
The field data has been analyzed to compare the trends obtained from the laboratory data collected under customized controlled field conditions to the field data trends. Artificial Neural Network (ANN) analysis was used in wells without full log suits to obtain the anisotropic geomechanical parameters. The results highlight the maturation, organic richness and clay composition effect on the recorded field data as well as the geomechanical properties obtained from the laboratory measurements.
The stress and fluid sensitivity of shale formations have been well recognized since the early days of conventional reservoir drilling, completion and production operations as they typically require special attention for minimizing wellbore instability during drilling and maintaining high integrity wells throughout the life cycle of these wells. Shales are highly heterogeneous and anisotropic formations and their source rock characteristics also have introduced further complexities with the organic matter and compositional variations throughout the areal extent of the reservoirs. These variations and their alterations as a function of the level of maturity of the organic matter require further study for better understanding of the differences and similarities between the seal shales and reservoir shales and the role of the organic matter and its maturity level in these differences. One of the critical aspects of the organic matter presence is in quantification of shale mechanical properties and strength and their direction dependence for successful field development. The level of maturity of the organic matter also influences the mechanical, acoustic, petrophysical and failure properties of organic rich shale formations. The mineralogical composition typically deviates from carbonate rich to quartz rich in the rock matrix with clay and organic matter amount and distribution heterogeneity in the reservoir. The layered structure introduced by the depositional history of the formation along with the heterogeneity in the distribution of organic matter result in various degree of anisotropy in reservoir properties (Sondergeld and Rai, 2011; Vernik and Milovac, 2011). A better understanding on the anisotropic characteristics of the shale formations and key parameters impacting the anisotropy is essential for field operational success from exploration studies for seismic attributes to reservoir characterization, drilling and hydraulic fracture design and production optimization.
We studied the Vaca Muerta (VM) Play (Neuquén Basin, Argentina) focusing on an oil window mature well (VR ~0.9-1.1%) to determine 1) zones of enrichment and depletion, 2) correlation/allocation to produced fluids, and 3) in-situ GOR and PVT characteristics.
Zones of saturation versus depletion, total in-place liquids, oil quality and bitumen enrichment throughout the Upper (U-), Middle (M-), and Lower (L-) VM were documented using screening methods such as Rock-Eval, TOC, thermovaporisation and pyrolysis gas chromatography on 24 original whole rock samples as well as solvent extracted aliquots. For production allocation and API prediction produced fluids were analysed in comparison to extracts from the shale units using whole oil chromatography and stable carbon isotope as well as high resolution mass spectrometry (FT-ICR MS). For prediction of GOR and PVT characteristics a combination of MSSV-pyrolysis and PVT modelling was used in the PhaseKinetics approach (di Primio and Horsfield, 2006) for immature samples and in the PhaseSnapShot approach (Kuske et al., 2019) for matured samples.
Especially the methods and experimental protocols used for the predictive assessments (FT-ICR MS; MSSV) are novel, unique, and strongly improve our ability to correctly describe the effects of production fractionation on bulk fluid properties and hence to formulate appropriate production strategies. In general, this study excels by combining results from organic geochemistry with those of PVT modeling and analysis.
The Vaca Muerta Formation (Neuquén Basin) is a world class Shale reservoir that covers oil, condensate and gas windows, with more than 300 horizontal wells drilled in the whole basin. This case study is located in the Shale Oil window that includes 30 horizontal wells on production, in a zone characterized by a huge areal and lithological variability due to the nature of the mix carbonate-siliciclastic depositional system. The main objective of this work is to characterize petrophysical and sedimentological properties of Vaca Muerta Fm. at log resolution to visualize and adjust the landing zones, relate to well productivity and extrapolate this information to a static model.
Logs and core integration workflows allowed to obtain 11 electrofacies honoring the composition and texture of the formation. The electrofacies composition is calculated from the basic electrical logs (Gamma Ray, Density, Photoelectric Factor and Compression Sonic) and interpreted kerogen volume, while the textural component was imposed by working the supervised electrofacies models with the sedimentological description of the rock. Subsequently, each electrofacies was assigned petrophysical properties such as porosity and water saturation from well logs calibrated with laboratory data.
The Vaca Muerta Formation consists primarily of a mixed carbonate-siliciclastic basinal facies in the largely progradational Quintuco-Vaca Muerta system. There are between 150-450 meters of organic-rich strata, all of which have the potential to produce, but there is also significant vertical and lateral heterogeneity related to the intercalation of different lithologies, the clinoform geometry and areal position. A better understanding of the reservoir characteristics of each of these facies, their distribution and their link to petrophysical properties is a key variable to select the best landing zones to develop the area.
The main findings of this study are: i) electrofacies model shows that organic content (electrofacies E7-E11) and porosity increases north and northwestwards for all LZ, ii) the mineral proportion for each electrofacies varies within the depositional system position (e.g. carbonate content increases southeastward, iii) in general, best productive wells are related to better electrofacies, iv) Electrofacies E1 & E2 (low TOC) show higher Sw and low TOC, while E7-E11 exhibits lower Sw, v) the model highlights new upside opportunities with additional hydrocarbon potential, vi) the geological and electrofacies model allowed to improve the understanding on the depositional system that will help to build robust paleoenvironmental maps.
Padin, Anton (Total Exploration and Production) | Pijaudier-Cabot, Gilles (Université de Pau et des Pays de l'Adour) | Lejay, Alain (Total Exploration and Production) | Pourpak, Hamid (Total Exploration and Production) | Mathieu, Jean-Philippe (Total Exploration and Production) | Onaisi, Atef (Total Exploration and Production) | Boitnott, Gregory (New England Research, Inc.) | Louis, Laurent (New England Research, Inc.)
Having a large number of layers in a reservoir model is computationally time-consuming, hence simulation of hydraulic fracturing in unconventional reservoirs usually rely on simplified, log-based models. In such models, vertical heterogeneities are upscaled to a few, averaged facies with homogeneous stiffness, stress, strength, toughness and natural fracture properties. In reality, however, unconventional reservoirs often contain singular heterogeneities and strong vertical and horizontal anisotropic properties that greatly affect fracture growth. The abundance of heterogeneities is believed to affect vertical hydraulic fracture growth (positively or negatively) due to stress differences, toughening effects at interfaces or the piling of thin lithologies with extreme, opposed stiffness or strength properties. From the simulation point of view, the challenge remains keeping a computationally-efficient but also representative (well-upscaled) model.
In this work, we focused on stiffness characterization, and particularly, on Young’s modulus calibration, and provide a concept-proof example for the Vaca Muerta formation, in Argentina. The current strategy in building stiffness models is to rely on sonic data to generate upscaled models with a few representative layers. A core acquisition program is normally put in place to calibrate the log-based model, and includes triaxial tests, where dynamic and static properties are measured at various stress conditions. Technically, characterization of each relevant lithology using these core measurements is possible, but given the degree of vertical heterogeneity, it would imply a very important logistical and economical effort. In addition, core plug selection is usually biased towards the stiffest rocks, leaving aside other facies, such as weak or ductile layers. As a result of these difficulties, core programs are usually limited to a few core plugs covering the target reservoir, leaving calibration of other units, and particularly of potential fracture barriers, unknown.
To address these difficulties, we concept-proved a core-to-log methodology that provides a fast calibration method for log-based elasticity. We measured rebound hardness in parallel to dynamic measurements of ultrasonic surface wave velocities (P and S) at the milimetric scale, then calibrated the results with discrete triaxial tests performed on plugs, representing all relevant lithological facies, and finally compared the results against log-based parameters. Our work shows that such integration helps at developing robust core-to-log elasticity relationships in the entire core length, eventually providing a proper foundation for better stiffness model prediction, at a fraction of the cost and time of traditional core acquisition programs.
The Early Tithonian – Early Valanginian Vaca Muerta Formation of the Neuquén Basin in Argentina, constitutes a world-class shale play outside the US and Canada, and corresponds to distal marine facies of the Vaca Muerta-Quintuco System. The aim of this work is to present a basin-scale characterization of the vertical and lateral distribution of the organic-rich units (TOC>2% by weight) of the Vaca Muerta Formation, integrating them within a sequence stratigraphic framework. The dataset comprises basin-scale 3D seismic coverage and almost five hundred wells widely distributed over an area of 30,000 km2. The Vaca Muerta Play includes twelve organic-rich units (OVM, Organic-rich Vaca Muerta with TOC ≥ 2% by weight), where the first eight correspond to the up-to-date tested landing zones. These OVM units correspond to transgressive systems tracts and lower section of highstand system tracts of high frequency sequences and were defined considering a well marker framework including chronostratigraphic surfaces and diachronic surfaces (top of organic-rich facies). Multiple regional well correlations were developed and calibrated with well geochemical data and acoustic impedance seismic sections. Finally, the results of this study are presented through eight thickness maps of the main organic-rich units (OVM1-OVM8) and several regional well and seismic interpreted sections. These regional maps allow us to infer stratigraphic controls (e.g. systems tracts, previous clinoform paleo-topography, etc.) and influences of regional tectonic controls (morpho-structural domains). Regional thickness maps presented in this paper allow a detailed understanding of the 3D distribution of the main landing zones of the Vaca Muerta Play in the Neuquén Basin and are very useful in exploration and development subsurface assessments. The methodologies and results in this paper are also applicable to others unconventional resources of marine shales.
The Early Tithonian – Early Valanginian Vaca Muerta Formation (Weaver, 1931, emend. Leanza, 1973) of the Neuquén Basin in Argentina, constitutes a world-class shale play outside the US and Canada. The Vaca Muerta Formation corresponds to distal marine facies (outer ramp to basinal facies in a mixed siliciclastic-carbonate setting) of the Vaca Muerta-Quintuco System.