Changes

The history of the discovery and development of the Vaca Muerta play dances for more than a decade with an intense series of events, such as the international search of new unconventional resources, the nationalization of the main operator, dramatic shifts in fiscal regime, a quick evolution of the play concepts (from vertical to horizontal wells) and of technology (from 500 to 3000 m laterals), and the Covid-19 pandemic. Nevertheless, the situation allowed conditions for economic success.

The history of the discovery and development of the Vaca Muerta play dances for more than a decade with an intense series of events, such as the international search of new unconventional resources, the nationalization of the main operator, dramatic shifts in fiscal regime, a quick evolution of the play concepts (from vertical to horizontal wells) and of technology (from 500 to 3000 m laterals), and the Covid-19 pandemic. Nevertheless, the situation allowed conditions for economic success.

The geological knowledge of the Vaca Muerta play derives from (1) data gathered during the last decade, related to the search and discovery of the Giant Field Vaca Muerta, and (2) the legacy of 100 years of activity of the O&G industry in the Neuquén Super Basin. The integration of the geological disciplines, at different scales, presents a unique unconventional play, exceptionally thick (100–400 m), vast (30,000 km2), and porous (10%–20%), with a prograding clinoform hosting up to eight landing zones, and all types of fluid segments (from black oil to dry gas).

The geological knowledge of the Vaca Muerta play derives from (1) data gathered during the last decade, related to the search and discovery of the Giant Field Vaca Muerta, and (2) the legacy of 100 years of activity of the O&G industry in the Neuquén Super Basin. The integration of the geological disciplines, at different scales, presents a unique unconventional play, exceptionally thick (100–400 m), vast (30,000 km²), and porous (10%–20%), with a prograding clinoform hosting up to eight landing zones, and all types of fluid segments (from black oil to dry gas).

The current play concept consists in landing the horizontal wells in the proximal bottomsets and lower foresets of the clinoform, sectors with higher hydrocarbon potential and easier fracture growth. The rocks in these sectors show the best reservoir characteristics (averages: TOC 5%; porosity 12%; clay 10%–20%; water saturation 20%), the most adequate geomechanical properties (homogeneous rock with Young’s Modulus <4 Mpsi, low Poisson Ratio ~0.25, and interfaces with weak geomechanical contrasts), and a thick vertical stack (30–40 m) of lithofacies with the aforementioned characteristics. With this concept in mind, at least two landing zones have been fully de-risked, and other six have been confirmed.

The current play concept consists in landing the horizontal wells in the proximal bottomsets and lower foresets of the clinoform, sectors with higher hydrocarbon potential and easier fracture growth. The rocks in these sectors show the best reservoir characteristics (averages: TOC 5%; porosity 12%; clay 10%–20%; water saturation 20%), the most adequate geomechanical properties (homogeneous rock with Young’s Modulus <4 Mpsi, low Poisson Ratio ~0.25, and interfaces with weak geomechanical contrasts), and a thick vertical stack (30–40 m) of lithofacies with the aforementioned characteristics. With this concept in mind, at least two landing zones have been fully de-risked, and other six have been confirmed.

==Conditions for Economic Success==

==Conditions for Economic Success==

The Vaca Muerta play has continued to progress lowering the breakeven to US$40/bbl for oil and US$2.0 MMBtu for wet gas. As activity ramps up these values will continue to fall, placing the Vaca Muerta play squarely on its way to be a disrupter in Argentina’s O&G industry, the economy of Argentina and of the Southern Cone. The operators in the development phase believe that the combination of costs, well performance, and product prices are earning a return in their investments. In other words, the combination of below ground factors (geology) and above ground factors (e.g., contract terms, regulations, supply chain, security, market access) are allowing the development to be profitable. Although several other organic-rich formations around the world (in China, Australia, Russia, Saudi Arabia, Oman, Mexico, Indonesia) may have comparable potential to the Vaca Muerta play, the presence of several critical factors has allowed the latter to become the first competitive unconventional self-sourced play outside of North America (see [[:file:M125-VacaMuerta-Table1.jpeg|Table 1]]).

The Vaca Muerta play has continued to progress lowering the breakeven to US$40/bbl for oil and US$2.0 MMBtu for wet gas. As activity ramps up these values will continue to fall, placing the Vaca Muerta play squarely on its way to be a disrupter in Argentina’s O&G industry, the economy of Argentina and of the Southern Cone. The operators in the development phase believe that the combination of costs, well performance, and product prices are earning a return in their investments. In other words, the combination of below ground factors (geology) and above ground factors (e.g., contract terms, regulations, supply chain, security, market access) are allowing the development to be profitable. Although several other organic-rich formations around the world (in China, Australia, Russia, Saudi Arabia, Oman, Mexico, Indonesia) may have comparable potential to the Vaca Muerta play, the presence of several critical factors has allowed the latter to become the first competitive unconventional self-sourced play outside of North America (see [[:file:M125-VacaMuerta-Table1.jpeg|Table 1]]).

[[file:M125-VacaMuerta-Table1.jpeg|center|framed|’’Table 1.’’ Conditions for Economic Success. Main Critical Factors That Allowed the Vaca Muerta to Become the First Competitive Unconventional Self-Sourced Play Outside of North America.]]

 

[[file:M125-VacaMuerta-Table1.jpeg|center|framed|'''Table 1.''' Conditions for Economic Success. Main Critical Factors That Allowed the Vaca Muerta to Become the First Competitive Unconventional Self-Sourced Play Outside of North America.]]

Repsol-YPF fractured the initial Vaca Muerta vertical wells in 2010, hence it has taken the O&G industry some 10 years and 1000 wells, to prove the play’s competitiveness with North American resources. And it has taken 3–7 years for major O&G companies to become confident enough in its commerciality, to sanction large developments. With time, willingness to invest and good geology, the Unconventional Revolution will not remain a North American story and Vaca Muerta will be just the first example of economically successful unconventional development, among other petroleum-rich provinces endowed with infrastructure (known as [[Super Basin]]s).

Repsol-YPF fractured the initial Vaca Muerta vertical wells in 2010, hence it has taken the O&G industry some 10 years and 1000 wells, to prove the play’s competitiveness with North American resources. And it has taken 3–7 years for major O&G companies to become confident enough in its commerciality, to sanction large developments. With time, willingness to invest and good geology, the Unconventional Revolution will not remain a North American story and Vaca Muerta will be just the first example of economically successful unconventional development, among other petroleum-rich provinces endowed with infrastructure (known as [[Super Basin]]s).

===Stratigraphic Setting===

===Stratigraphic Setting===

The Vaca Muerta Formation corresponds to the distal facies of a clinoform system developed during a shallowing-upward sedimentary cycle, lasting approximately 11 My, known as the Vaca Muerta–Quintuco system<ref>Mitchum, R. M., and M. A. Uliana, 1982, Estratigrafía sísmica de las formaciones Loma Montosa, Quintuco y Vaca Muerta, Jurásico Superior y Cretácico Inferior de la Cuenca Neuquina, República Argentina: 1° Congreso Nacional de Hidrocarburos, Petróleo y Gas: Buenos Aires, Argentina, Actas, p. 439–484.</ref><ref> Spalletti, L., and G. Veiga, 2007, Variability of continental depositional systems during lowstand sedimentation: An example from the Kimmeridgian of the Neuquén Basin, Argentina: Latin American Journal of Sedimentology and Basin Analysis, v. 14, p. 85–104.</ref>. The Vaca Muerta is associated with the bottomsets and foresets of the clinoforms, consisting of organic-rich mudstones and marlstones. The Quintuco Formation represents the topsets, and consist of grainstones, wackestones, and dolostones. The progradation of the clinoforms created a thickening of the Vaca Muerta toward the northwest. It is in this vertical stack of organic-rich units where industry is landing the unconventional horizontal wells (e.g., Vittore et al.<ref name=Vttor2020 />; [[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]).

The Vaca Muerta Formation corresponds to the distal facies of a clinoform system developed during a shallowing-upward sedimentary cycle, lasting approximately 11 My, known as the Vaca Muerta–Quintuco system<ref>Mitchum, R. M., and M. A. Uliana, 1982, Estratigrafía sísmica de las formaciones Loma Montosa, Quintuco y Vaca Muerta, Jurásico Superior y Cretácico Inferior de la Cuenca Neuquina, República Argentina: 1° Congreso Nacional de Hidrocarburos, Petróleo y Gas: Buenos Aires, Argentina, Actas, p. 439–484.</ref><ref> Spalletti, L., and G. Veiga, 2007, Variability of continental depositional systems during lowstand sedimentation: An example from the Kimmeridgian of the Neuquén Basin, Argentina: Latin American Journal of Sedimentology and Basin Analysis, v. 14, p. 85–104.</ref>. The Vaca Muerta is associated with the bottomsets and foresets of the clinoforms, consisting of organic-rich [[mudstones]] and marlstones. The Quintuco Formation represents the topsets, and consist of grainstones, wackestones, and dolostones. The progradation of the clinoforms created a thickening of the Vaca Muerta toward the northwest. It is in this vertical stack of organic-rich units where industry is landing the unconventional horizontal wells (e.g., Vittore et al.<ref name=Vttor2020 />; [[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]).

The prograding clinoforms are here subdivided into six units<ref name=Mnsni2020a /> ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). Each unit represents a transgressive-regressive sedimentary cycle of third order. The sedimentary cycles show that the highest total organic carbon (TOC) is recorded during the late transgressive systems tract (TST) and early highstand systems tract (HST), when organic matter accumulated both in the bottomset and along the foresets, forming condensed sections. During the falling stage systems tract (FSST), sediment bypassed the topsets increasing the sediment accumulation rate in the foresets, which resulted thicker and diluted in TOC. During the lowstand systems tract (LST), organic-rich intervals accumulated only in the distal bottomsets ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). The maximum thickness of the organic-rich intervals results parallel to (and basinward of) the shelf break, and the maximum area covered by the organic-rich intervals is associated with the least steep foresets<ref name=Dmngz2020 />. These observations suggest that the organic matter distribution is controlled by the construction of the clinoform and may be predicted through the sequence stratigraphy ([[:file:M125-VacaMuerta-Figure9.jpeg|Figure 9]]). Because thick units with high TOC (and associated high porosity) are fundamental elements for a landing zone, the proximal bottomsets and the lower foresets were soon indicated as zones with high hydrocarbon prospectivity ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]).

The prograding clinoforms are here subdivided into six units<ref name=Mnsni2020a /> ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). Each unit represents a transgressive-regressive sedimentary cycle of third order. The sedimentary cycles show that the highest total organic carbon (TOC) is recorded during the late transgressive systems tract (TST) and early highstand systems tract (HST), when organic matter accumulated both in the bottomset and along the foresets, forming condensed sections. During the falling stage systems tract (FSST), sediment bypassed the topsets increasing the sediment accumulation rate in the foresets, which resulted thicker and diluted in TOC. During the lowstand systems tract (LST), organic-rich intervals accumulated only in the distal bottomsets ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). The maximum thickness of the organic-rich intervals results parallel to (and basinward of) the shelf break, and the maximum area covered by the organic-rich intervals is associated with the least steep foresets<ref name=Dmngz2020 />. These observations suggest that the organic matter distribution is controlled by the construction of the clinoform and may be predicted through the sequence stratigraphy ([[:file:M125-VacaMuerta-Figure9.jpeg|Figure 9]]). Because thick units with high TOC (and associated high porosity) are fundamental elements for a landing zone, the proximal bottomsets and the lower foresets were soon indicated as zones with high hydrocarbon prospectivity ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]).

The Vaca Muerta Formation with dominant organic-rich lithofacies (>2% TOC) may be up to 270 m thick. Median values within this organic-rich Vaca Muerta are 11% total porosity, 44% water saturation, 5% TOC, 28% carbonate, 30% QFP, 21% clay<ref name=Ortz />. However, the median values need to be scrutinized with accuracy because reservoir properties and fluid types vary significantly both among the six units of the Vaca Muerta-Quintuco system and within each unit ([[:file:M125-VacaMuerta-Figure12.jpeg|Figure 12]]). These variations suggest that each stratigraphic interval of interest must be addressed and analyzed as a different play type, with potentially different hydrocarbon storage, response to stimulation, and productivity ([[:file:M125-VacaMuerta-Figure13.jpeg|Figure 13]]).

The Vaca Muerta Formation with dominant organic-rich lithofacies (>2% TOC) may be up to 270 m thick. Median values within this organic-rich Vaca Muerta are 11% total porosity, 44% water saturation, 5% TOC, 28% carbonate, 30% QFP, 21% clay<ref name=Ortz />. However, the median values need to be scrutinized with accuracy because reservoir properties and fluid types vary significantly both among the six units of the Vaca Muerta-Quintuco system and within each unit ([[:file:M125-VacaMuerta-Figure12.jpeg|Figure 12]]). These variations suggest that each stratigraphic interval of interest must be addressed and analyzed as a different play type, with potentially different hydrocarbon storage, response to stimulation, and productivity ([[:file:M125-VacaMuerta-Figure13.jpeg|Figure 13]]).

[[file:M125-VacaMuerta-Figure12.jpeg|center|framed|{{figure number|12}}Petrophysical properties of the organic-rich Vaca Muerta (TOC >2 %) per stratigraphic unit, per morpho-structural domain. Inside dashed green line maturity is above 0.8 (R° %). Horizontal scale is linear and left edge. (-) represent null values. PHIT = total porosity; SWT = total water saturation; VCARB = volume of carbonate; VCL = volume of clay; VKER = volume of kerogen; VQFP = volume of quartz, feldspar, and plagioclase (modified from Ortiz et al.<ref name=Ortz />).

[[file:M125-VacaMuerta-Figure12.jpeg|center|framed|{{figure number|12}}Petrophysical properties of the organic-rich Vaca Muerta (TOC >2 %) per stratigraphic unit, per morpho-structural domain. Inside dashed green line maturity is above 0.8 (R° %). Horizontal scale is linear and left edge. (-) represent null values. PHIT = total porosity; SWT = total water saturation; VCARB = volume of carbonate; VCL = volume of clay; VKER = volume of kerogen; VQFP = volume of quartz, feldspar, and plagioclase (modified from Ortiz et al.<ref name=Ortz />).]]

[[file:M125-VacaMuerta-Figure13.jpeg|center|framed|{{figure number|13}}Vaca Muerta petrophysical model from wells in the morpho-structural domain Eastern Basin Center 2 (left) and Southern Flank (right), see domains in [[:file:M125-VacaMuerta-Figure12.jpeg|Figure 12]]. Tracks (from left to right): stratigraphic Units; gamma ray; thickness reference with dotted lines every 50 m; Passey filter; TOC (light green >2 %, dark green >4 %); total porosity (yellow >5%, v/v); volume compound of minerals and fluids; total water saturation (%, blue represents water, green represents hydrocarbon) (from Ortiz et al.<ref name=Ortz />).]]

[[file:M125-VacaMuerta-Figure13.jpeg|center|framed|{{figure number|13}}Vaca Muerta petrophysical model from wells in the morpho-structural domain Eastern Basin Center 2 (left) and Southern Flank (right), see domains in [[:file:M125-VacaMuerta-Figure12.jpeg|Figure 12]]. Tracks (from left to right): stratigraphic Units; gamma ray; thickness reference with dotted lines every 50 m; Passey filter; TOC (light green >2 %, dark green >4 %); total porosity (yellow >5%, v/v); volume compound of minerals and fluids; total water saturation (%, blue represents water, green represents hydrocarbon) (from Ortiz et al.<ref name=Ortz />).]]

===Organic Geochemistry===

===Organic Geochemistry===

The organic material of Vaca Muerta, homogeneous in its composition within the basin, consists of amorphous material of aquatic marine origin, with scarce-to-null terrestrial contributions, and denotes excellent oil-prone quality. A century of activity of the O&G industry in the Neuquén Basin provided an extended database of tens of thousands of samples from cuttings, cores, sidewall cores, and outcrops of the Vaca Muerta Formation, from the entire basin. The evaluation of this data set identified six areas with different hydrocarbon potential ([[:file:M125-VacaMuerta-Figure14.jpeg|Figure 14]]). The areas broadly overlap with the morpho-structural domains ([[:file:M125-VacaMuerta-Figure8.jpeg|Figures 8]], [[file:M125-VacaMuerta-Figure12.jpeg|12]]). The main resources encompassing high-quality low-sulfur oils and gas condensates are in the Embayment area, where stratigraphic units with high TOC are thick. The gases produced in other areas show a thermogenic marine origin (type II kerogen), with a lower contribution of biogenic methane<ref name=Brssn2020>Brisson, I. E., M. E. Fasola, and H. J. Villar, 2020, [https://archives.datapages.com/data/specpubs/memoir121/data/297_aapg-sp2120297.htm Organic geochemical patterns of the Vaca Muerta Formation], in D. Minisini, M. Fantín, I. Lanusse Noguera, and H. A. Leanza, eds., Integrated geology of unconventionals: The case of the Vaca Muerta play, Argentina: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m121.htm AAPG Memoir 121], p. 297–328.</ref> (1%–10%).

The organic material of Vaca Muerta, homogeneous in its composition within the basin, consists of amorphous material of aquatic marine origin, with scarce-to-null terrestrial contributions, and denotes excellent oil-prone quality. A century of activity of the O&G industry in the Neuquén Basin provided an extended database of tens of thousands of samples from cuttings, cores, sidewall cores, and outcrops of the Vaca Muerta Formation, from the entire basin. The evaluation of this data set identified six areas with different hydrocarbon potential ([[:file:M125-VacaMuerta-Figure14.jpeg|Figure 14]]). The areas broadly overlap with the morpho-structural domains ([[:file:M125-VacaMuerta-Figure8.jpeg|Figures 8]], [[:file:M125-VacaMuerta-Figure12.jpeg|12]]). The main resources encompassing high-quality low-sulfur oils and gas condensates are in the Embayment area, where stratigraphic units with high TOC are thick. The gases produced in other areas show a thermogenic marine origin (type II kerogen), with a lower contribution of biogenic methane<ref name=Brssn2020>Brisson, I. E., M. E. Fasola, and H. J. Villar, 2020, [https://archives.datapages.com/data/specpubs/memoir121/data/297_aapg-sp2120297.htm Organic geochemical patterns of the Vaca Muerta Formation], in D. Minisini, M. Fantín, I. Lanusse Noguera, and H. A. Leanza, eds., Integrated geology of unconventionals: The case of the Vaca Muerta play, Argentina: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m121.htm AAPG Memoir 121], p. 297–328.</ref> (1%–10%).

[[file:M125-VacaMuerta-Figure14.jpeg|center|framed|{{figure number|14}}Regional maps and geochemical values of TOC, HI, S1/TOC along the stratigraphy of the Vaca Muerta Formation (each color relates to a specific area). Ma = Malargüe; ChL = Chihuido-Lomita; Em = Embayment; HA = Huincul Arch; PL = Picún Leufú; NEP = Northeastern Platform. Note the red line with triangles indicating the location of the thrust front on the surface (rather than in subsurface). TR = transformation ratio from HI variation (from Brisson et al.<ref name=Brssn2020 />).]]

[[file:M125-VacaMuerta-Figure14.jpeg|center|framed|{{figure number|14}}Regional maps and geochemical values of TOC, HI, S1/TOC along the stratigraphy of the Vaca Muerta Formation (each color relates to a specific area). Ma = Malargüe; ChL = Chihuido-Lomita; Em = Embayment; HA = Huincul Arch; PL = Picún Leufú; NEP = Northeastern Platform. Note the red line with triangles indicating the location of the thrust front on the surface (rather than in subsurface). TR = transformation ratio from HI variation (from Brisson et al.<ref name=Brssn2020 />).]]

The current play concept consists in landing the horizontal wells in the proximal bottomsets and lower foresets, which are the depositional sectors with the highest hydrocarbon storage potential and easiest fracture growth (i.e., larger stimulated rock volume). The rocks in these sectors show the best reservoir characteristics (TOC >2%, av. 5%; porosity >8%, av. 11%; clay <40%, av. 10–20%; water saturation <50%, av. 20%), the most adequate geomechanical properties (Young’s Modulus <4 Mpsi, low Poisson Ratio ~0.25, and homogeneous rock units exhibiting interfaces with weak geomechanical contrasts), and a thick vertical stack (av. 30–40 m) of lithofacies with the aforementioned characteristics ([[:file:M125-VacaMuerta-Figure16.jpeg|16A]] and window I and II in ([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]]). Although the distal bottomsets register the highest TOC, they are not a preferred landing zone because (with respect to proximal bottomsets) porosity is lower, clay is higher, ash beds have the highest recurrence, concretions and sills are more numerous, and landing zones are thinner (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16A]]). With this concept in mind, at least two landing zones have been fully de-risked and are producing in factory mode in the development phase (lower Unit 1 and lower Unit 2), and other six landing zones have been tested with production logging tool (PLT) data showing encouraging results ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). All current successful landing zones are in the Embayment area where hydrocarbon potential is the highest and wells produce high-quality low-sulfur oils and gas condensates.

The current play concept consists in landing the horizontal wells in the proximal bottomsets and lower foresets, which are the depositional sectors with the highest hydrocarbon storage potential and easiest fracture growth (i.e., larger stimulated rock volume). The rocks in these sectors show the best reservoir characteristics (TOC >2%, av. 5%; porosity >8%, av. 11%; clay <40%, av. 10–20%; water saturation <50%, av. 20%), the most adequate geomechanical properties (Young’s Modulus <4 Mpsi, low Poisson Ratio ~0.25, and homogeneous rock units exhibiting interfaces with weak geomechanical contrasts), and a thick vertical stack (av. 30–40 m) of lithofacies with the aforementioned characteristics ([[:file:M125-VacaMuerta-Figure16.jpeg|16A]] and window I and II in ([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]]). Although the distal bottomsets register the highest TOC, they are not a preferred landing zone because (with respect to proximal bottomsets) porosity is lower, clay is higher, ash beds have the highest recurrence, concretions and sills are more numerous, and landing zones are thinner (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16A]]). With this concept in mind, at least two landing zones have been fully de-risked and are producing in factory mode in the development phase (lower Unit 1 and lower Unit 2), and other six landing zones have been tested with production logging tool (PLT) data showing encouraging results ([[:file:M125-VacaMuerta-Figure5.jpeg|Figure 5]]). All current successful landing zones are in the Embayment area where hydrocarbon potential is the highest and wells produce high-quality low-sulfur oils and gas condensates.

[[file:M125-VacaMuerta-Figure16.jpeg|center|framed|{{figure number|16}}Left: conceptual sketch generalizing trends of independent proxies in the bottomsets and foresets of the Vaca Muerta–Quintuco system. Horizontal trends are related to the shaded unit. Vertical trends related to left end of the prograding clinoform. Right: current play concept consisting in landing the horizontal wells in the proximal bottomsets (I) and lower foresets (II), sectors with the best reservoir characteristics. Further play concepts to be proved include: thin carrier beds within high-TOC intervals in the lower foresets (III), tight reservoirs interbedded with transgressive high-TOC intervals in the middle foresets (IV), and stacking of specific foresets with good reservoir characteristics (V).

[[file:M125-VacaMuerta-Figure16.jpeg|center|framed|{{figure number|16}}Left: conceptual sketch generalizing trends of independent proxies in the bottomsets and foresets of the Vaca Muerta–Quintuco system. Horizontal trends are related to the shaded unit. Vertical trends related to left end of the prograding clinoform. Right: current play concept consisting in landing the horizontal wells in the proximal bottomsets (I) and lower foresets (II), sectors with the best reservoir characteristics. Further play concepts to be proved include: thin carrier beds within high-TOC intervals in the lower foresets (III), tight reservoirs interbedded with transgressive high-TOC intervals in the middle foresets (IV), and stacking of specific foresets with good reservoir characteristics (V).]]

In the future, a further play concept may be tested in the foresets, where the number of landing wells has increased since 2019. As evidenced by subtle variations in seismic stacking patterns, the clinoforms did not prograde uniformly, and advanced (as a delta) with discrete steps, recording foresets with variable direction, extent, geometry, lithofacies, and degree of aggradational component. Within this variability, units with appropriate reservoir characteristics and thickness do exist in specific foresets, and represent promising prospects. This new play concept in the foresets consist of a stacking of thin foresets with good reservoir characteristics interbedded with thicker foresets with bad reservoir characteristics, creating a hybrid unconventional play, similar to the Niobrara play in the DJ Basin, the Bazhenov play in Russia, and the Wolfberry and Bone Spring plays in the Permian Basin (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]], window III and V). Another option consists of transgressive units with good reservoir characteristics, typically deposited in the bottomsets, and cyclically deposited in the foresets. The interbedding of (1) muddy, high-TOC, transgressive units, climbing the clinoform from the bottomsets during sea level rise, and (2) coarse and lean foresets enhances the idea of a hybrid play where source rocks and tight reservoirs are interbedded (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]], window IV). Furthermore, in the future, exploration may move beyond the Embayment area into the structural highs, in the fold-and-thrust belt, in sectors affected by igneous intrusions, and in areas where the Vaca Muerta is deeply buried.

In the future, a further play concept may be tested in the foresets, where the number of landing wells has increased since 2019. As evidenced by subtle variations in seismic stacking patterns, the clinoforms did not prograde uniformly, and advanced (as a delta) with discrete steps, recording foresets with variable direction, extent, geometry, lithofacies, and degree of aggradational component. Within this variability, units with appropriate reservoir characteristics and thickness do exist in specific foresets, and represent promising prospects. This new play concept in the foresets consist of a stacking of thin foresets with good reservoir characteristics interbedded with thicker foresets with bad reservoir characteristics, creating a hybrid unconventional play, similar to the Niobrara play in the DJ Basin, the Bazhenov play in Russia, and the Wolfberry and Bone Spring plays in the Permian Basin (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]], window III and V). Another option consists of transgressive units with good reservoir characteristics, typically deposited in the bottomsets, and cyclically deposited in the foresets. The interbedding of (1) muddy, high-TOC, transgressive units, climbing the clinoform from the bottomsets during sea level rise, and (2) coarse and lean foresets enhances the idea of a hybrid play where source rocks and tight reservoirs are interbedded (([[:file:M125-VacaMuerta-Figure16.jpeg|Figure 16B]], window IV). Furthermore, in the future, exploration may move beyond the Embayment area into the structural highs, in the fold-and-thrust belt, in sectors affected by igneous intrusions, and in areas where the Vaca Muerta is deeply buried.