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.
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.
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.
The initial high cost of exploitation of the sustained, increasingly growing development of unconventional resources in Argentina has resulted in concentrating all efforts to increase well productivity while reducing construction and completion costs. The optimization of hydraulic fracture (HF) treatments is vitally important. It is the primary strategy used to achieve an optimal reservoir drainage area, consequently characterizing the fracture geometry, including the height, for the continuous improvement of HF treatment and planning.
Several types of technologies and methodologies are used to estimate fracture height during and after a hydraulic stimulation treatment. These technologies can provide information about the fracture geometry and extension in the near-wellbore (NWB) and far-field areas. The determination of a reliable correlation between those methodologies represents a challenge as a result of formation complexity, heterogeneity, and limitations of evaluation technologies. It is well-known that some areas in the Vaca Muerta formation contain layers that can act as fracture barriers and are responsible for fracture containment.
This paper presents a fast and simple methodology that uses conventional well logs [gamma ray (GR), sonic, and density] from pilot wells to identify potential fracture barriers. This approach establishes a means to evaluate the degree to which the rock will have the ability to control fracture height growth. This methodology was determined useful for planning perforation intervals or clusters placement, particularly in those formations with stress profile showing reduced stress contrast and, when complemented with geological information, this method also provides useful information for horizontal well trajectory. Case studies are provided to illustrate examples of the proposed fracture barrier index (FBI) being calibrated or compared to other fracture height assessment. Additionally, the benefits of adding this new approach to current methodologies and technologies to aid completion design optimization and decision making is discussed.
In March 2018, an electric wireline (e-line) milling solution was deployed to remove a composite plug in an unconventional well in Argentina. This abstract details the planning and execution of the first composite plug removal with an e-line milling solution in Argentina.
Plug and perf hydraulic fracturing operations were halted when a composite plug became stuck in the in 5" × 21.4 lb/ft casing at 2,442 m MD in the vertical section of an unconventional well. The operator initially considered mobilizing coil tubing (CT) to mill the plug, however time constraints drove them to explore more efficient alternative options. The availability, short mobilization time, efficient rig up, and past successes of an e-line tractor and milling assembly demonstrated a clear advantage versus CT for this application.
The objective for the milling operation was to remove the composite plug and confirm unrestricted access to the next perf stage at 4,252 m MD. The successful plug milling operation on the 1st run required approximately 9.5 hours of milling. Over the next 11 hours, two additional runs with heavy milling at different depths were required to clear a path to the target depth. The use of this solution allowed the operation to continue as per the program without further interventions.
An e-line milling solution for composite plugs and other wellbore hardware is an efficient and cost- effective alternative to conventional methods. Additional benefits include a substantial decrease in HSE risk exposure by minimizing the operational footprint through a reduction of personnel and equipment.
Lage, Antonio Carlos Vieira Martins (Petrobras) | Arduino, Edgard Gurgel do Amaral (Petrobras) | Loureiro, Sebastião de Andrade (Petrobras) | Vanni, Guilherme Siqueira (Petrobras) | Filho, Hercilio Pereira da Silva (Petrobras)
The present paper describes performance improvements and well safety achieved with the use of Managed Pressure Drilling (MPD) in the exploratory block of Parva Negra Este, in Neuquén Basin. Petrobras Argentina S.A (PESA), with the technical support from the Petrobras’ headquarters, in Brazil, drilled two exploratory wells applying MPD and targeting Vaca Muerta shale oil & gas play.
High-pressure zones characterized the drilling scenario, reaching, usually, pore pressures higher than 18 lbm/gal in unconventional reservoirs, composed of tight sand and shale. The use of MPD in both well constructions was quite efficient, including well control and plug and abandonment (P&A) operational applications. Those operations proved that MPD can effectively replace the Under-Balanced Drilling (UBD) system, which is standard practice in that area.
In the first well, PESA reported significant gains in drilling performance when compared to other wells previously drilled. Drilling with MPD did not record non-productive time (NPT), differing substantially from the previous wells constructed in the surroundings of Parva Negra Este with an average NPT of 20 days. A considerably larger recovery of coring samples was achieved, being also possible to eliminate one well section, by drilling two zones of interest in a singlesection. Additionally, lessons learned were implemented, resulting on higher rate of penetration (ROP) with the support of MPD.
In the second well, a high overpressurized pore zone was reached, leading to a very complex well control event followed by a permanent P&A operation. The formation pore pressure was much higher than the expected for the area. Instead of using an 18 lbm/gal drilling fluid, it was necessary to weight the fluid up to 21.3 lbm/gal, adding hematite as weighting material. In that scenario, the use of MPD made the operations of circulation and well cementing safer than with the conventional drilling approach utilized in that vicinity.
The application of Dynamic Formation Integrity Tests (DFIT) and Dynamic Pore Pressure Tests (DPPT) ensured a more precise operational window, helping to formulate risk matrices for safely pulling the drilling string out of the hole. In addition, the precise definition of the operational window was a valuable information to plan the best approach for P&A. Besides performing those tests, the MPD system was very useful to evaluate operational parameters and verify how effective was the settlement of the abandonment cement plugs.
In summary, MPD supported safer drilling and P&A jobs, better drilling performance and greater information achievement through more efficient well logging and sample coring.
Hao, Zhang (Baker Hughes, a GE Company) | Nora, Alarcon (Baker Hughes, a GE Company) | Julio, Arro (Baker Hughes, a GE Company) | Guillermo, Crespo (Baker Hughes, a GE Company) | Diego, Licitra (YPF) | Carlos, Hernandez (Chevron LC YPF-CVX JV)
The estimation of fluid properties and rock composition is an integral part of formation evaluation. Unconventional resources such as organic-rich shales are geologically complex, due to great variability in rock composition and post-depositional diagenetic processes. In addition, low porosities, such as those usually encountered in unconventional reservoirs, are not well defined from conventional logs due to the large influence of the rock lithological components and high uncertainties of the log measurements. The errors in estimated porosity not only relate to measurement errors, but also to the incomplete knowledge of matrix parameters. Consequently, a reliable method that integrates mineral and fluid petrophysical models is needed to determine the key formation properties in whole-rock characterization.
It is well known that the most important petrophysical parameter obtained from nuclear magnetic resonance (NMR) logging data is a lithology independent porosity. The ill-defined problem in NMR inversion requires proper regularization methods to stabilize the inversion results. The incorporation of conventional logs as penalty constraints in the NMR inversion process can lead to an improved quantification of fluid typing and formation porosity. However, the accuracy of the fluid model is also influenced by the quality of the estimated matrix properties. Geochemical logs based on pulsed neutron technology have been successfully applied to determine elements for identifying lithology and mineralogy. A probabilistic method incorporating geochemical and conventional log measurements can reliably estimate the matrix mineral composition and porosity. However, a good understanding of the fluid properties is also important for accurate results from the mineral model. The fluid and the mineral model complement each other. Consequently the integration of the two models using NMR, geochemical, and conventional logs can provide an improved whole-rock characterization.
In this work, a unified workflow that includes petrophysical relations and rock physics models is proposed. Probabilistic mineralogy inversion using geochemical and conventional logs solves for matrix properties that are used as inputs for the fluid inversion model. Simultaneous inversion using NMR echo trains and conventional logs determines pore fluid composition and formation porosity that are used as fluid parameters to improve the results in the mineral model. By using both inversion models jointly, a set of petrophysical properties that account for all available log measurements can be determined for the whole rock, and the integrated workflow can potentially reduce the uncertainty in the well log interpretation that usually applies a limited set of logs. A field example from an Argentina well in the Vaca Muerta unconventional play is presented and discussed to show the superior interpretation proficiency of the proposed methodology.
Also a fixed window size is used for each pass. Argentina case study To illustrate the suitability of EI to exploration seismic data, the method outlined above is applied to data from offshore Argentina. The dataset was acquired in 2017, having a total survey size of 19,500 km. A dip line in the northern part of the survey will be used will be used in this abstract to illustrate some of the challenges typical of frontier exploration. The line varies in water-depth from less than 100 m at the western end to over 2000 m at the eastern end.
Ramirez, Oscar (Spectrum Geo Inc.) | Chen, Genmeng (Spectrum Geo Inc.) | Saunders, Mike (Spectrum Geo Inc.) | Geiger, Laurie (Spectrum Geo Inc.) | Cvetkovic, Milos (Spectrum Geo Inc.) | Roberts, Mark (Spectrum Geo Inc.) | Clarke, Richard (Spectrum Geo Inc.)
Imaging sedimentary basins in the context of oil and gas exploration entails different but complementary objectives. Understanding the tectonic architecture of a basin requires acquisition and processing strategies that differ from those strategies that are required to understand play fairways and prospects. In this paper we demonstrate effective processing strategies that produce clear and consistent images of the Moho discontinuity and elements of the crystalline basement, with equally clear images of the sedimentary section showing amplitude anomalies consistent with the presence of hydrocarbons.
Presentation Date: Tuesday, October 16, 2018
Start Time: 1:50:00 PM
Location: 210C (Anaheim Convention Center)
Presentation Type: Oral
Guarracino, Luis (CONICET & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Amaya, Macarena (Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Perdomo, Santiago (CONICET & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Juarez, Amilcar (Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Gelpi, Gabriel (CONICET & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Pendiuk, Jonatan (CONICET & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Lagos, Soledad (CONICET & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Gómez, José (Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Tocho, Claudia (CICBA & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina) | Ainchil, Jerónimo (UNSADA & Facultad de Cs. Astronómicas y Geofísicas, UNLP, Argentina)
In this work the main results of the first humanitarian geophysical project founded by GWB in Argentina are presented. The objective of the project is the search of groundwater resources for small rural and aboriginal communities in Miraflores (Chaco) using electrical prospecting methods. The study site faces serious water scarcity and quality problems. It is located on one of the poorest regions of the country with high child malnutrition and infant mortality rates. From a hydrogeological point of view, the only sources of freshwater are small shallow-buried paleochannels which have sandy textures and therefore capacity for storing water. In order to identify these paleochannels, Vertical Electrical Soundings and Electrical Resistivity Tomographies were performed in priority areas. Based on the analysis of geoelectrical data, 10 new wells were drilled and hand-operated pumps were installed to protect and facilitate water extraction. The results of the project have a direct impact on the quality of life of local communities and also provides solid basis for replicating this type of study in other critical areas of Chaco.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: 204A (Anaheim Convention Center)
Presentation Type: Oral