- Email: [email protected]
Petroleum systems modeling in tectonically complex areas — A 2D migration study from the Neuquen Basin, Argentina
Journal of Geochemical Exploration 89 (2006) 201 – 204 www.elsevier.com/locate/jgeoexp
Petroleum systems modeling in tectonically complex areas — A 2D migration study from the Neuquen Basin, Argentina Carolyn Lampe a,⁎, Kristijan Kornpihl a , Simone Sciamanna b , Tomás Zapata b , Gonzalo Zamora b , Roberto Varadé b a
IES, Integrated Exploration Systems, Ritterstr. 23, 52072 Aachen, Germany b Repsol-YPF, Esmeralda 255, C1035ABE Buenos Aires, Argentina Received 21 August 2005; accepted 10 November 2005 Available online 15 March 2006
Abstract A roughly 30 km 2D section across the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina, is the basis for a petroleum systems study, including structural restoration through time, deposition and erosion, pressure, temperature and migration modeling. Integrating tectonic and petroleum systems modeling proved critical to properly evaluate sub-thrust plays. Multidimensional modeling of dynamic processes allows accurate assessment and prediction of the potential of petroleum systems in tectonically complex areas such as the Neuquen Basin. © 2006 Elsevier B.V. All rights reserved. Keywords: Neuquen Basin; Petroleum systems modeling; Petroleum migration; TecLink
1. Introduction Two-dimensional petroleum systems modeling was performed along an east–west cross section, located in the external zone of the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina (Fig. 1). The Neuquen Basin is a triangular-shaped basin covering more than 160,000 km2. It contains an Upper Triassic– Cenozoic sedimentary succession more than 7 km in thickness with several petroleum source rock units and Jurassic–Cretaceous reservoir intervals (Vergani et al., 1995). ⁎ Corresponding author. E-mail addresses: [email protected] (C. Lampe), [email protected] (S. Sciamanna). 0375-6742/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2005.11.041
While the basin has been the focus of petroleum exploration, a comprehensive understanding of the thrustbelt petroleum systems, including estimates of volumetric and preserved reserves, is still not in place (Zapata et al., 2002). A first attempt to better understand the basin was made by Sciamanna and Sassi (2004) applying 2D forward structural and thermal modeling. The purpose of this paper is to investigate tectonic and petroleum systems modeling to allow a better understanding of what drives migration and accumulation in highly complex thrustbelt areas. In this study, a two-dimensional, PVT-controlled, multi-component, 3-phase petroleum migration model demonstrates the integration of geometry changes, pressure evolution, thermal history, maturation, migration and accumulation
202
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
compare the effects on source rock maturity and reservoir charging mechanisms. 2. Geology
Fig. 1. Map of the Neuquen Basin, Argentina. The study area is indicated by the rectangle. The dashed line outlines the basin edge.
through time to understand the petroleum distribution in the study area. Two models with different erosional evolution and varying heatflow histories are used to
The Neuquen Basin consists of a thick succession of mainly Mesozoic and Cenozoic sedimentary rocks, overlaying volcanic Permian basement. The Jurassic and Cretaceous succession consists of alternating continental sandstones and marine platform sediments with intercalated sandy formations, ranging upward to shallow marine to terrestrial evaporites. These are unconformably overlain by terrigenous sediments of the Upper Cretaceous Neuquen Group. The mainly clastic and often conglomeratic Mesozoic rocks have various andesitic intrusions (Zapata et al., 2002). In the model, only the Permian basement and the Mesozoic strata are represented. The most prolific source-rock interval in the study area is the Upper Jurassic Vaca Muerta Formation, a thick marine shale sequence containing mainly Type-II kerogen. Urien and Zambrano (1994) indicate Vaca Muerta strata to typically have 2–3 wt.% TOC with maxima N 8 wt.% and HI from 200 to 675 mg hydrocarbon/g total organic carbon (mg HC/g TOC). The Lower Cretaceous Agrio Formation is also considered to be an important regional source rock, containing up to 5 wt.% TOC with HI up to 700 mg HC/g TOC (Cruz et al., 1998). The study area is characterized by a combination of both fault-bend and fault-propagation structures, later deformed by reverse basement-involved faults (Zapata et al., 2002). Detailed cross-cutting relationship analysis
Fig. 2. Present-day model input geometry for both Model A and Model B with stratigraphic units and main source-rock and reservoir intervals. The white dots depict the position of the data extraction in Fig. 4.
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
203
The modeled cross section is shown in Fig. 2, together with the major stratigraphic elements. 3. Methodology The study was performed using the PetroMod 2D PetroFlow package, including the TecLink® tool developed by IES (Integrated Exploration Systems GmbH, Hantschel and Broichhausen, 2002). This tool allows a direct link between existing tools for tectonic modeling and PetroMod's petroleum systems modeling technology. Several balanced paleo-sections were used in two different models to forward-model the pressure, temperature, and maturity history of the section, including fully PVT-controlled multi-component migration. Fig. 3 shows the palinpastic reconstructions that served as the basis for the models. These reconstructions were generated by Sciamanna and Sassi (2004) using Thrustpack®, a tool developed by IFP (Institut Français du Pétrole, Sassi et al., 1998) to perform forward structural and thermal modeling. 3.1. Model input Each model comprises thirteen original layers (Fig. 2) that were further subdivided to account for thin (50 m) reservoir intervals at the base of both the Trancoso and the Upper Agrio formations, respectively. Two
Fig. 3. Palinpastic reconstruction of the 2D section used for the petroleum systems models (after Sciamanna and Sassi, 2004).
and radiometric dating of volcanics suggest that initiation of deformation started during the late Mesozoic time (Zamora et al., in press).
Fig. 4. Transformation ratio of kerogen to petroleum through time for the two source-rock units. Solid lines: Vaca Muerta Formation; dashed lines: Agrio Formation. Thick lines: constant heatflow of 60 mW/m2; medium lines: Cretaceous heatflow peak; thin lines: Miocene heatflow peak. For position of data extraction see Fig. 2.
204
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
stratigraphic units, the Vaca Muerta and Agrio formations, are considered to be source rocks. The Vaca Muerta formation was assigned an initial TOC of 4 wt.% and an HI of 500 mg HC/g TOC, and the Lower Agrio formation was assigned 2 wt.% TOC with an HI of 500 mg HC/g TOC. A generic Type-II kinetic model for conversion of kerogen to petroleum after Burnham (1989) was assigned to both source rocks. 3.2. Model geometry Two models were constructed that incorporate different erosion scenarios. Both models use the same geometry until the deposition of the Neuquen Group (70 Ma). From there on, two different erosional histories were assumed. Model A applied progressive erosion during four thrusting phases between 70 and 40 Ma (Fig. 3), as well as additional erosion after the last thrusting phase (40 Ma) until present-day. In Model B, a single post-folding erosional event was assumed from 40 Ma onward.
of hydrocarbons available for trap charge. For the Agrio source-rock, on the other hand, the erosion history seems to be the driving mechanism for determining the amount and quality of generated hydrocarbons, regardless of the heatflow history. Numerical models inherently imply significant uncertainties due to the extensive number of required input parameters, model resolution or simply lack of information, e.g. with regard to the source-rock units (where, how thick, how rich, which kinetics, etc.), the seal and/or reservoir quality, or fault parameters (a conduit for flow, sealing, timing). Additional sensitivity runs, including risking of key parameters, would enhance the quality of predictions that can be made for the presented models. Acknowledgements The authors thank Repsol-YPF (Buenos Aires) for permission to publish the data.
3.3. Boundary conditions
References
In order to test various thermal scenarios three different basal heat flow histories were assumed, partially based on the tectonic and volcanic evolution of the study area: (1) a constant heatflow of 60 mW/m2 through time, (2) an increasing basal heat flow with an Upper Cretaceous heatflow peak of 75 mW/m2 at 60 Ma, and (3) an increasing basal heat flow with a Miocene heatflow peak of 80 mW/m2 at 15 Ma.
Burnham, A.K., 1989. A simple kinetic model of petroleum formation and cracking. Lawrence Livermore National Laboratory Report UCID-21665. 11 p. Cruz, C.E., Kozlowski, E., Villar, H.J., 1998. Agrio (Neocomian) petroleum systems: main target in the Neuquén Basin Thrust Belt, Argentina. Presented at the ABGP/American Association of Petroleum Geologists International Conference and Exhibition. November 8–11, 1998, Rio de Janeiro, Brazil. Hantschel, T., Broichhausen, H., 2002. IES Integrated Exploration Systems, PetroMod 2D TecLink, Technical Information Brochure (http://www.ies.de/Company/pdf/IES-2DTecLink-Info.pdf). Sassi, W., Rudkiewicz, J.L., Divies, R., 1998. New methods for integrated modeling of deformation and petroleum generation in fold and thrust belts. American Association of Petroleum Geologists, Annual meeting, Salt Lake City. Sciamanna, S., Sassi, W., 2004. Thrustbelt petroleum systems: 2D modeling, a minimum requirement. Case study from Neuquen basin, Argentina. Extended Abstract Book — ALAGO Conference, Mérida, Mexico, pp. 4–6. Urien, C.M., Zambrano, J.J., 1994. Petroleum systems in the Neuquén Basin, Argentina. In: Magoon, L.B., Dow, W.G. (Eds.), The Petroleum System — From Source to Trap, American Association of Petroleum Geologists Memoir, vol. 60, pp. 513–534. Vergani, G.D., Tankard, A.J., Belotti, H.J., Welsink, H.J., 1995. Tectonic evolution and paleogeography of the Neuquen basin, Argentina. In: Tankard, A.J., Suarez, R., Welsink, H. (Eds.), Petroleum Basins of South America, American Association of Petroleum Geologists Memoir, vol. 62, pp. 383–402. Zamora, G., Zapata, T., del Pino, D., Ansa A., in press. Structural evolution of the Agrio fold and thrust belt. Geological Society of America, Special Publication. Zapata, T., Córsico, S., Dzelalija, F., Zamora, G., 2002. La faja plegada y corrida del Agrio: análisis structural y su relación con los estratos terciarios de la cuenca Neuquina, Argentina. V Congreso de Exploración y Desarrollo de Hidrocarburos, IAPG. extended abstract.
4. Results As expected, the maturation, expulsion and accumulation history of the basin depends greatly on changing geometries through time, as well as on the changing basal heat flow conditions. The applied basal heat flow histories seem to be the key factor in defining the prospectivity of the area in terms of volume available for charge at the time of trap formation, as well as the quality of the potentially trapped hydrocarbons. Fig. 4 shows the transformation ratio for the Agrio and Vaca Muerta source-rock intervals for each heat flow scenario, for models A and B. Looking at Vaca Muerta (the main source of petroleum) for the constant basal heatflow scenario, both models show that timing of hydrocarbon generation versus timing of trap formation (assumed to occur between 60 and 40 Ma) is a major risk factor, regardless of the erosion history. However, the variable heatflow scenarios show that the erosion rates do have a significant impact on the amount
Petroleum systems modeling in tectonically complex areas — A 2D migration study from the Neuquen Basin, Argentina Carolyn Lampe a,⁎, Kristijan Kornpihl a , Simone Sciamanna b , Tomás Zapata b , Gonzalo Zamora b , Roberto Varadé b a
IES, Integrated Exploration Systems, Ritterstr. 23, 52072 Aachen, Germany b Repsol-YPF, Esmeralda 255, C1035ABE Buenos Aires, Argentina Received 21 August 2005; accepted 10 November 2005 Available online 15 March 2006
Abstract A roughly 30 km 2D section across the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina, is the basis for a petroleum systems study, including structural restoration through time, deposition and erosion, pressure, temperature and migration modeling. Integrating tectonic and petroleum systems modeling proved critical to properly evaluate sub-thrust plays. Multidimensional modeling of dynamic processes allows accurate assessment and prediction of the potential of petroleum systems in tectonically complex areas such as the Neuquen Basin. © 2006 Elsevier B.V. All rights reserved. Keywords: Neuquen Basin; Petroleum systems modeling; Petroleum migration; TecLink
1. Introduction Two-dimensional petroleum systems modeling was performed along an east–west cross section, located in the external zone of the Faja Plegada y Corrida del Agrio in the Neuquen Basin, Argentina (Fig. 1). The Neuquen Basin is a triangular-shaped basin covering more than 160,000 km2. It contains an Upper Triassic– Cenozoic sedimentary succession more than 7 km in thickness with several petroleum source rock units and Jurassic–Cretaceous reservoir intervals (Vergani et al., 1995). ⁎ Corresponding author. E-mail addresses: [email protected] (C. Lampe), [email protected] (S. Sciamanna). 0375-6742/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gexplo.2005.11.041
While the basin has been the focus of petroleum exploration, a comprehensive understanding of the thrustbelt petroleum systems, including estimates of volumetric and preserved reserves, is still not in place (Zapata et al., 2002). A first attempt to better understand the basin was made by Sciamanna and Sassi (2004) applying 2D forward structural and thermal modeling. The purpose of this paper is to investigate tectonic and petroleum systems modeling to allow a better understanding of what drives migration and accumulation in highly complex thrustbelt areas. In this study, a two-dimensional, PVT-controlled, multi-component, 3-phase petroleum migration model demonstrates the integration of geometry changes, pressure evolution, thermal history, maturation, migration and accumulation
202
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
compare the effects on source rock maturity and reservoir charging mechanisms. 2. Geology
Fig. 1. Map of the Neuquen Basin, Argentina. The study area is indicated by the rectangle. The dashed line outlines the basin edge.
through time to understand the petroleum distribution in the study area. Two models with different erosional evolution and varying heatflow histories are used to
The Neuquen Basin consists of a thick succession of mainly Mesozoic and Cenozoic sedimentary rocks, overlaying volcanic Permian basement. The Jurassic and Cretaceous succession consists of alternating continental sandstones and marine platform sediments with intercalated sandy formations, ranging upward to shallow marine to terrestrial evaporites. These are unconformably overlain by terrigenous sediments of the Upper Cretaceous Neuquen Group. The mainly clastic and often conglomeratic Mesozoic rocks have various andesitic intrusions (Zapata et al., 2002). In the model, only the Permian basement and the Mesozoic strata are represented. The most prolific source-rock interval in the study area is the Upper Jurassic Vaca Muerta Formation, a thick marine shale sequence containing mainly Type-II kerogen. Urien and Zambrano (1994) indicate Vaca Muerta strata to typically have 2–3 wt.% TOC with maxima N 8 wt.% and HI from 200 to 675 mg hydrocarbon/g total organic carbon (mg HC/g TOC). The Lower Cretaceous Agrio Formation is also considered to be an important regional source rock, containing up to 5 wt.% TOC with HI up to 700 mg HC/g TOC (Cruz et al., 1998). The study area is characterized by a combination of both fault-bend and fault-propagation structures, later deformed by reverse basement-involved faults (Zapata et al., 2002). Detailed cross-cutting relationship analysis
Fig. 2. Present-day model input geometry for both Model A and Model B with stratigraphic units and main source-rock and reservoir intervals. The white dots depict the position of the data extraction in Fig. 4.
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
203
The modeled cross section is shown in Fig. 2, together with the major stratigraphic elements. 3. Methodology The study was performed using the PetroMod 2D PetroFlow package, including the TecLink® tool developed by IES (Integrated Exploration Systems GmbH, Hantschel and Broichhausen, 2002). This tool allows a direct link between existing tools for tectonic modeling and PetroMod's petroleum systems modeling technology. Several balanced paleo-sections were used in two different models to forward-model the pressure, temperature, and maturity history of the section, including fully PVT-controlled multi-component migration. Fig. 3 shows the palinpastic reconstructions that served as the basis for the models. These reconstructions were generated by Sciamanna and Sassi (2004) using Thrustpack®, a tool developed by IFP (Institut Français du Pétrole, Sassi et al., 1998) to perform forward structural and thermal modeling. 3.1. Model input Each model comprises thirteen original layers (Fig. 2) that were further subdivided to account for thin (50 m) reservoir intervals at the base of both the Trancoso and the Upper Agrio formations, respectively. Two
Fig. 3. Palinpastic reconstruction of the 2D section used for the petroleum systems models (after Sciamanna and Sassi, 2004).
and radiometric dating of volcanics suggest that initiation of deformation started during the late Mesozoic time (Zamora et al., in press).
Fig. 4. Transformation ratio of kerogen to petroleum through time for the two source-rock units. Solid lines: Vaca Muerta Formation; dashed lines: Agrio Formation. Thick lines: constant heatflow of 60 mW/m2; medium lines: Cretaceous heatflow peak; thin lines: Miocene heatflow peak. For position of data extraction see Fig. 2.
204
C. Lampe et al. / Journal of Geochemical Exploration 89 (2006) 201–204
stratigraphic units, the Vaca Muerta and Agrio formations, are considered to be source rocks. The Vaca Muerta formation was assigned an initial TOC of 4 wt.% and an HI of 500 mg HC/g TOC, and the Lower Agrio formation was assigned 2 wt.% TOC with an HI of 500 mg HC/g TOC. A generic Type-II kinetic model for conversion of kerogen to petroleum after Burnham (1989) was assigned to both source rocks. 3.2. Model geometry Two models were constructed that incorporate different erosion scenarios. Both models use the same geometry until the deposition of the Neuquen Group (70 Ma). From there on, two different erosional histories were assumed. Model A applied progressive erosion during four thrusting phases between 70 and 40 Ma (Fig. 3), as well as additional erosion after the last thrusting phase (40 Ma) until present-day. In Model B, a single post-folding erosional event was assumed from 40 Ma onward.
of hydrocarbons available for trap charge. For the Agrio source-rock, on the other hand, the erosion history seems to be the driving mechanism for determining the amount and quality of generated hydrocarbons, regardless of the heatflow history. Numerical models inherently imply significant uncertainties due to the extensive number of required input parameters, model resolution or simply lack of information, e.g. with regard to the source-rock units (where, how thick, how rich, which kinetics, etc.), the seal and/or reservoir quality, or fault parameters (a conduit for flow, sealing, timing). Additional sensitivity runs, including risking of key parameters, would enhance the quality of predictions that can be made for the presented models. Acknowledgements The authors thank Repsol-YPF (Buenos Aires) for permission to publish the data.
3.3. Boundary conditions
References
In order to test various thermal scenarios three different basal heat flow histories were assumed, partially based on the tectonic and volcanic evolution of the study area: (1) a constant heatflow of 60 mW/m2 through time, (2) an increasing basal heat flow with an Upper Cretaceous heatflow peak of 75 mW/m2 at 60 Ma, and (3) an increasing basal heat flow with a Miocene heatflow peak of 80 mW/m2 at 15 Ma.
Burnham, A.K., 1989. A simple kinetic model of petroleum formation and cracking. Lawrence Livermore National Laboratory Report UCID-21665. 11 p. Cruz, C.E., Kozlowski, E., Villar, H.J., 1998. Agrio (Neocomian) petroleum systems: main target in the Neuquén Basin Thrust Belt, Argentina. Presented at the ABGP/American Association of Petroleum Geologists International Conference and Exhibition. November 8–11, 1998, Rio de Janeiro, Brazil. Hantschel, T., Broichhausen, H., 2002. IES Integrated Exploration Systems, PetroMod 2D TecLink, Technical Information Brochure (http://www.ies.de/Company/pdf/IES-2DTecLink-Info.pdf). Sassi, W., Rudkiewicz, J.L., Divies, R., 1998. New methods for integrated modeling of deformation and petroleum generation in fold and thrust belts. American Association of Petroleum Geologists, Annual meeting, Salt Lake City. Sciamanna, S., Sassi, W., 2004. Thrustbelt petroleum systems: 2D modeling, a minimum requirement. Case study from Neuquen basin, Argentina. Extended Abstract Book — ALAGO Conference, Mérida, Mexico, pp. 4–6. Urien, C.M., Zambrano, J.J., 1994. Petroleum systems in the Neuquén Basin, Argentina. In: Magoon, L.B., Dow, W.G. (Eds.), The Petroleum System — From Source to Trap, American Association of Petroleum Geologists Memoir, vol. 60, pp. 513–534. Vergani, G.D., Tankard, A.J., Belotti, H.J., Welsink, H.J., 1995. Tectonic evolution and paleogeography of the Neuquen basin, Argentina. In: Tankard, A.J., Suarez, R., Welsink, H. (Eds.), Petroleum Basins of South America, American Association of Petroleum Geologists Memoir, vol. 62, pp. 383–402. Zamora, G., Zapata, T., del Pino, D., Ansa A., in press. Structural evolution of the Agrio fold and thrust belt. Geological Society of America, Special Publication. Zapata, T., Córsico, S., Dzelalija, F., Zamora, G., 2002. La faja plegada y corrida del Agrio: análisis structural y su relación con los estratos terciarios de la cuenca Neuquina, Argentina. V Congreso de Exploración y Desarrollo de Hidrocarburos, IAPG. extended abstract.
4. Results As expected, the maturation, expulsion and accumulation history of the basin depends greatly on changing geometries through time, as well as on the changing basal heat flow conditions. The applied basal heat flow histories seem to be the key factor in defining the prospectivity of the area in terms of volume available for charge at the time of trap formation, as well as the quality of the potentially trapped hydrocarbons. Fig. 4 shows the transformation ratio for the Agrio and Vaca Muerta source-rock intervals for each heat flow scenario, for models A and B. Looking at Vaca Muerta (the main source of petroleum) for the constant basal heatflow scenario, both models show that timing of hydrocarbon generation versus timing of trap formation (assumed to occur between 60 and 40 Ma) is a major risk factor, regardless of the erosion history. However, the variable heatflow scenarios show that the erosion rates do have a significant impact on the amount