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Third HGS and EAGE Conference on Latin America
- Conference date: November 8-10, 2021
- Location: Online
- Published: 08 November 2021
1 - 20 of 25 results
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Column Height Guidelines for Undrilled Prospects in the Southern Gulf of Mexico (GoM)
By M. ShannSummaryPelagic shale seals of the Gulf of Mexico are known to form excellent seals but how do you estimate a range in column height assumptions for a high relief undrilled prospect in the GoM?
The underlying principle of top seal integrity is related to Effective Stress and hydrocarbon buoyancy and seal capacity can be estimated from a knowledge of expected hydrocarbon phase and reservoir pressure conditions.
In the absence of this type of constraining data, a study of field analogues is revealing in terms of separating column heights that are due to topseal integrity versus fill-to-spill trap geometries. Plotting column height versus overburden depth is also surprising in how the largest column heights are related to traps that lie only 1000 – 1500 meters below mudline. These observations and their likely reasons are discussed in relation to key fields of the Southern GoM and conclusions are drawn for predicting column height in undrilled prospects plus some pitfalls to watch out for.
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Exploring an Active Transform Margin South of the Cayman Trough and the Karstified Miocene Carbonate "Akna Play Test.”
More LessSummaryChortis is a major continental tectonic block in the Western Caribbean. Its offshore component stretches some 750 kms between the coasts of Honduras and Nicaragua to western Jamaica. Some 50 wells were drilled across this terrain up to the early 1980’s with 73% of the wells recording hydrocarbon shows and five (5) wells flowed hydrocarbons plus several significant source rock penetrations. Seeps, shows and source data indicate two key and robust source units are present.
By contrast the deep-water basins along the southern edge of the Cayman Trough transform margin remain undrilled and modern seismic has revealed a buried Miocene carbonate platform play that is represented by a set of eight (8) structural prospects, some of which show evidence for karstified reservoir enhancement with seismic karst geometries like the carbonate plays in Mexico.
The Akna play fairway test will drill the largest of this series of Miocene carbonate prospects, where it is located over an intra-basinal high and sealed by deep water pelagic shales. Seismic studies have revealed positive DHI anomalies both across the crest of the Akna Miocene primary target and shallower in the overburden section. These DHI events may correlate to hydrocarbons found in seabed drop cores over Akna and in turn be related to the two source intervals present in this region.
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Rediscovering Main Cape after 47 Years, Offshore Honduras in the Mosquitia Basin
Authors V. Winifred and J. CorcoranSummaryThe Mosquitia Basin located on the Chortis Block offshore Honduras and Nicaragua was an active exploration area in the 1970’s with over 30 exploration wells drilled, 75% of which recorded hydrocarbon shows. Exploration stopped for global political reasons in 1980 and only one offshore well has been drilled since.
Several wells flowed oil in the basin and Main Cape 1 was drilled by Unocal in 1973 and found oil in Middle Eocene carbonate reservoirs. Seismic mapping and a detailed integration of paleo-depositional environments with petrophysics and DST test analysis now illuminates the hydrocarbon potential of the Main Cape structure and points to the necessary appraisal steps and key challenges to making this a commercial oil development to the benefit of Honduras.
The petroleum system of the Mosquitia Basin is inextricably linked to the evolution of the Caribbean plate. The targeted reservoirs are in the Middle Eocene, these carbonates seem to be influenced by local climatic and environmental condition. The high percentage of Miliolina fauna, the absence of planktonic foraminifera and Nannofossils reveal that these carbonates was deposited on a restricted carbonate platform in a very shallow marine hypersaline environment on a gently sloping ramp (inner ramp to mid ramp) with local reef patches. The upper part of the reservoir appears to have been deposited in a middle ramp setting where abundant Nummulites have been reported. The absence of Nummulites in the major portion of the Eocene sequence could indicate very warm (greater than approximately 31 °C) or warm-temperate (less than approximately 20°C) shallow-water environments that is exposed to salinity fluctuations.
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Geologic Framework for Critical Risk Factors Analysis of a Tertiary Carbonate Play in Colombian-Venezuelan Sedimentary Basins Along the Caribbean Margin of South America
Authors J.F. Arminio, C. Giraldo and M. SanchezSummaryHydrocarbon accumulations in a Tertiary carbonate play in sedimentary basins of northern South America range from small to medium to giant. The fields are located both onshore and in shallow waters of the southern Caribbean Sea. The play has proven to be commercial in both marine and terrestrial environments. Onshore, economic development is profitable with modest sizes of the accumulations. Recent drilling results along the margin call for a revision of our understanding of the development and geologic controls on this prolific play to better delineate critical risk segments. This collaborative study offers an updated framework for exploration plans in northwest South America. The play is mainly associated with isolated basement highs with reservoirs found in Late Oligocene to Early Miocene limestones and associated slope sands sourced and capped by massive Miocene shales. To date, eight commercial accumulations and three discoveries have been registered with approximately 21 TCF of gas in place distributed between five clustered Neogene basins: Lower Magdalena, Lower Guajira and Upper Guajira in Colombia and Golfo de Venezuela, Urumaco, and La Vela in western Venezuela. Play analogues have been documented in the exhumed Falcon basin of west Venezuela and in the Guajira peninsula in Colombia. The Neogene basins are genetically related and likely formed by transtensional collapse of Paleogene orogens. Basin subsidence was initiated by pervasive normal faulting of igneous-metamorphic substrate and continued in the Miocene when subsiding basins were filled with marine shales.
Renewed compression in Miocene–Pliocene caused tectonic inversion throughout the region. We estimate that an East-West right-lateral active strike-slip Oca fault is responsible for 30 to 40 km of total offset since Middle Miocene.
The primary source for thermogenic hydrocarbons is marine Oligo-Miocene shales with important terrestrial influence, controlled by the proximity to the continent. In Lower Guajira and Lower Magdalena basins of Colombia, there are also proven effective petroleum systems that involve biogenic gas in commercial quantities.
Recent discoveries and wide variation in the play's field sizes generate renewed interest in the exploration in the region onshore and offshore. The exploratory risk could be reduced by a better understanding of controls on the field size distribution and reservoir presence and/or quality.
Published large-scale structural models do not explain details revealed by recent drilling of the carbonate play along the edge of northern South America. Our integrated analysis from onshore to deep-water settings honours drilling results and updates the framework for analysing critical risks of petroleum systems impacted by complex Caribbean plate geodynamics.
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Cretaceous-Cenozoic Tectonostratigraphic Evolution and Hydrocarbon Prospectivity of the Sandino Forearc Basin, Offshore Nicaragua
More LessSummaryIn map view, the Central American forearc basin extends 1730 km along the Middle America trench and the western edge of the Caribbean plate and overlies the actively subducting Cocos plate. The entire forearc basin can be divided into three, structurally and stratigraphically distinct segments: 1) the 800-km-long northern segment that is submarine, undeformed, and extends from northern Guatemala to northern Nicaragua; 2) the 630-km-long, central segment of the Sandino forearc basin (SFB) is submarine, moderately deformed, and extends along the Nicaraguan margin to northernmost Costa Rica; and 3) the 300-km-long southern segment in Costa Rica is partially inverted by shallow subduction of the Cocos Ridge and includes the onshore Tempisque and Terraba deformed forearc belts of Costa Rica.
This study uses 5,582 line-km of 2D seismic reflection data with an average line spacing of 10 km tied to 6 wells to describe the central segment of the forearc of Nicaragua and northernmost Costa Rica. The offshore study area covers the forearc area from the shelf edge of Nicaragua to the slope of the Middle America trench in the dip direction and from the Gulf of Fonseca in northern Nicaragua to the northwestern margin of the Nicoya Peninsula in northern Costa Rica in the strike direction.
Our seismic and well data define three distinctive structural domains within the SFB: 1) the northwestern outer arc high that was uplifted during the Eocene and subaerially exposed during the early Miocene that resulted in significant erosion into the Eocene and lower section; structural inversion and persistent reactivation of the forearc high throughout the Miocene resulted in syn-depositional wedging onto the northwestern forearc high and extensional faults at the crest of the structure; 2) the forearc high bounding the central basin of the SFB was active during the Late Cretaceous-late Miocene and buried from late Miocene-Present as the SFB was overfilled and began to spill its clastic sediments into the Middle America trench; thick-skinned structural inversion of earlier normal faults of the Paleogene forearc depocenter and adjacent forearc high begins in the late Miocene and subjected the forearc high and main depocenter of the SFB to its most intensive periods of folding and erosion from the Pliocene to the present-day; and 3) the southwestern part of the SFB is significantly eroded with the Cretaceous oceanic plateau and island arc basement rocks of the Nicoya and Osa Peninsulas of Costa Rica representing the exhumed basement of the inverted SFB. Using 2D seismic data, this study maps the anticlinal trace of at 12, northwest-trending, offshore fold axes which result from Miocene to Recent inversion of Paleogene normal faults. This interpretation differs from the previous interpretations of these structures as transpressional flower structures that formed during Eocene time. This partially inverted, submarine fold-thrust belt is inferred to be an incipient stage in the structural evolution of the Central American forearc basin that is seen in its more advanced stage in the topographically-elevated and inverted forearc basins of southern Costa Rica.
Within this regional structural framework, the 2D seismic and well database were used to better understand the stratigraphy and hydrocarbon prospectivity of the SFB. We mapped the Miocene-Recent shelf rollover point of eight clinoforms to understand this period of basin infilling of the SFB that led to its eventual overfilling and spillover into the Middle America trench. Generally, shelf margins of the SFB trend to the northwest and prograde seaward to the southwest towards the forearc high to transversely fill the SFB. This study identifies an orthogonal Pliocene shift in shelf margin orientation that prograde to the northwest, axially filling the SFB.
We infer this shift in infilling is a response to the uplift and erosion of the more advanced inversion area of the Nicoya Peninsula that bounds the SFB to the southeast. The majority of the older Miocene, southwest-prograding SFB clinoforms are sigmoidal and shingled indicative of a low energy depositional environment. The younger northeast-prograding Pliocene shelf margins contain oblique clinoforms. These deposits occur within the shallow Pliocene section and may form favorable reservoir intervals but are too shallow to have hydrocarbon prospectivity.
Petroleum systems modeling was applied to the northwest and southeast deeper, depocenters of the SFB and created a basin model using the Corvina-2 wellbore and three pseudowell locations. This study improves on a previous basin model by previous workers that was based on a single seismic reflection line with more limited depth penetration. We also used lower heat flow than the previous basin model of 31 mW/m2 which is based on improved constraints from vitrinite reflectance calibration, bottom hole temperature, and BSR heat flow studies.
Results from our basin modeling indicates generation, migration, and accumulation from: 1) high-quality source rocks of the Coniacian-Upper Campanian Loma Chumico Formation from the deepest basin during the period of Eocene to middle Miocene; 2) from source rocks in the Brito formation during the period of early Miocene to present; and 3) from source rocks in the Masachapa formation during the period from late Miocene to Present. A new, untested conventional play type is inferred from AVO from the comparison of near-angle and far-angle stacks along with traditional DHI identification using the full-angle stacks. Uplift of the forearc high has led to updip horizontal migration along bedding planes with trapping mechanisms along crestal extensional faults that parallel the axis of the forearc high. Other play types include structural conformance within large anticlines.
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Deepwater Hydrocarbon Migration and Focus Challenges Explored in the Suriname-Guyana Basin
More LessSummaryThe Suriname-Guyana Basin emerged as a key exploration hub after the 2015 discovery of the Upper Cretaceous, deepwater Liza Field. To date, 19 additional discoveries have exploited the Liza play analog, targeting stratigraphically trapped basin floor submarine fans immediately outboard of the paleo shelf-slope break. The basin’s recent success has revitalized the industry’s interest in improving our understanding of the petroleum systems elements and how they lead to commercial accumulations. Recent exploration efforts provide new insights into the complex regional hydrocarbon migration and charge mechanisms. World class Albian-Turonian aged oil-prone source rocks are present throughout the basin. The better constrained Cenomanian-Turonian organically enriched interval is thought to be laterally extensive and present throughout the distal basin with a favorable maturation history for Mesozoic reservoirs. However, migration patterns remain poorly understood. The majority of the >7 km of post-source deposition lacks significant faulting and trapping structures. This overburden configuration presents significant challenges for the vertical migration and focusing of hydrocarbons, a critical component of Coniacian to Maastrichtian hydrocarbon charge. Regional 2D migration models utilizing calibrated seismic facies from well control were constructed over known fields and discoveries to investigate the primary drivers for vertical hydrocarbon movement and focus. These drivers include: 1) increased driving force where basement structure influences overlying stratal geometries, 2) changes in buoyancy caused by lateral baffling at facies boundaries, and 3) abnormal formation pressure variation associated with facies changes. We report here deductions made from this analysis paired with results from synthetic testing of lithologic and low amplitude structural controls on capillary resistance, buoyancy, and formation pressure to improve our understanding of the primary controlling factors on hydrocarbon migration and entrapment in this region.
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Analysis of the Poly-Phase Plate-Margin Processes of Primary Influence on Jurassic and Cretaceous Basin Development in Guyana-Demerara and Conjugate Guinea Plateau Basins
By K. CaseySummaryDemerara and Guinea plateaus are plate-margin conjugate structures in South America and Africa, respectively. They have experienced at least two phases of non-orthogonal extension punctuated by a phase of transpressional deformation in the Early Cretaceous prior to the opened connection between Central and Equatorial Atlantic was established. Jurassic-age rifting formed the Central Atlantic, and the Plateaus were located at the leading edge of the plate boundaries separating the incipient North American, South American, and African Plates. This rifting period is recorded by the tectonostratigraphic relationships observed at the western edge of the Plateaus. During rifting, the outer parts of the Plateaus experienced a phase of transtensional deformation that preceded the establishment of shallow-water carbonate deposition during Jurassic and Early Cretaceous times. Demerara and Guinea Plateaus became a structural accommodation zone between Central and Equatorial Atlantic opening in Early Cretaceous times. Poles of rotation necessitate transpressional deformation of both Plateaus that accommodated differential plate-margin extension with most compressional deformation accommodated by the South American plate-margin. The Albian unconformity regionally correlated on seismic lines across Demerara, Guinea and Florida is interpreted to be evidence for a contemporaneous exhumation of Jurassic and Early Cretaceous carbonate facies. Oceanic spreading has progressed, and separation of the plateaus continued with the marine connection between Central and Equatorial Atlantic established during Cenomanian times. Different parts of the Plateaus responded to the stress regimes differentially during these times.
In this work, we consider stratigraphic relationships and propose a spatially asymmetric structural evolution model that accounts for empirical seismic, gravity, and well data observations.
Recent authors postulate a volcanic origin for the Demerara and Guinea plateaus. Voluminous extrusive Jurassic magmatism from the Sierra Leone hot-spot is supported by the seismic observation of SDRs on deep seismic profiles. These SDRs are interpreted by recent authors to be of volcanic origin and associated with extrusive basaltic lava flows during the CAMP event in the Jurassic. In addition, the recovery from two sites of three dredged basalt samples of the Early Jurassic age confirms the presence of extrusive volcanism. The sites are located on the northeastern side of the Demerara Plateau, with local gradients up to 60 deg. The origin of these fault-related slopes we believe to be more consistent with high-angle strike-slip deformation. Additional evidence for rift-related magmatism of a younger age in the area comes from Demerara Plateau well FG2–1. Dating of recovered basalt samples of 125 MA and 120 MA have been linked recently to a sequence of SDRs.
The popularity of SDR interpretations from the Demerara Plateau are based on the similarity of the seismic character of deep reflectors from Pelotas basin regional 2D-seismic lines.
These seismic observations are further linked to the interpretations of SDRs on the Guinea Plateau, where existing seismic interpretations are equivocal, especially beneath the Top Jurassic reflector. Hence, we contend that the model-driven interpretations of SDR presence and significance are subject to the variable quality of the seismic data used. Could the significance of a primary SDR origin for the plateau areas be better explained by the structural solution proposed by this paper? If so, then heat-flow, maturity models, and basin models would require important modification. Recent drilling offshore Guyana has now shown mixed results. Some wells illustrate charge challenges as well as the predictability of the type of hydrocarbon that has ranged from immature heavy sulfur oil to gas condensate. The depositional environment plays a critical role in the type of organic matter that is deposited. The type of organic matter (oil or gas prone) and thermal maturity can be better constrained by basement development history in light of tectonic dynamics. Better understanding across the basin is needed for which prospects have the best volume and quality of charge to reservoirs.
Recent gravity, seismic data, well penetration records and dating of recovered material offer us an opportunity to fully integrate these data and to consider alternative models for the formation of the Demerara and Guinea marginal plateaus. We believe that the poly-phase structural origin of basement evolution better describes the primary origin and consequent subsidence patterns observed in time and space. The implication for this new structural model is critical to better explain temporal accommodation space development (subsidence patterns and driving mechanisms) for key Jurassic and Cretaceous SR and reservoir facies development, distribution, and sequence preservation.
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Distinguishing Petroleum Source Rock Acmes Across Northern South America: Application to Evaluate the Potential of the Albian to Maastrichtian Guyana Basin
More LessSummaryThis chronostratigraphic study focuses on distinguishing the unique intervals (acmes) of Cretaceous deposition, to evaluate their lateral variation from the Magdalena Basin (Colombia) to the areas of recent petroleum discoveries in the Guyana Basin and Demerara Plateau.
The current focus on lithostratigraphic formations, lumping entire depositional intervals, has led to confusion surrounding even one of the most referenced source rocks in the Southern Caribbean, the La Luna Formation.
The focus on this formation can lead to unintentionally disregarding other potential source acmes including the underlying Machiques Member of the Apon Formation in the Western Maracaibo basin, which is widely correlated to the first Oceanic Anoxic Event (OAE-1a), has a thickness of 30 meters, and an average of 1–1.5 wt.% TOC1. Additionally, while La Luna is one of many productive source rocks in the southwestern Mérida Andes, its productivity seems to be replaced by the La Morita Sandstone and slightly younger Navay Formation (corrected TOC 2.59 wt.%; 185 m thickness)2,3 in the neighboring Barinas-Apure Basin without a published explanation for the latter.
We constructed a chronostratigraphic column through Colombia to offshore Suriname by the combination and rationalization of multiple local stratigraphic columns, well log data, and paleoenvironmental information.
This integrated approach allows for a time-equivalent correlation of units to one another throughout the Caribbean and the ability to describe type localities of individual source rock deposition acmes. Using this methodology, the identification of numerous productivity acmes both younger and older than Cenomanian-Turonian (e.g. 85, 87 and 101) throughout northern South America as far as the Demerara Plateau, has allowed for an extrapolation of potential source rocks into current exploration areas of the Guyana Basin. This extrapolation has increased our understanding of source rock potential, correlation to OAE events, and continuity of lithologic units throughout the Guyana Basin. The upper acmes of the Demerara Rise condensed section can be correlated with lithostratigraphic units (Canje Formation) on the Guyana-Suriname shelf but are replaced by time-equivalent basin turbidite deposits in the deep basin. This methodology has also revealed the upper Albian as a potential source rock in basinal areas unaffected by the mid-Albian unconformity. Lastly, this identification of organic-rich acme timings provides the foundation for more accurate Ultimate Expellable Potential (UEP) modeling in future work.
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The Quest from Shallow Shelf to Deepwater in Latin America: How We Got Where We Are, Where We Are Going
Authors R. Hardy, G. Fergeson and J. PeckSummaryThe first exploration foray into open ocean was in the late 1940’s on Louisiana’s shallow shelf extending prolific onshore and marsh discoveries, enabled by a booming US post-War economy and a wealth of former military ocean engineering talent. As exploration and production innovations progressed in the ‘50’s and early ‘60’s Mexico’s nearby ‘Tampico and Salina Basin shelfs, plus Trinidad’s Gulf of Paria and Columbus Basin soon benefited, also extensions of geologically contiguous major onshore trends.
This initial trendology, enabled by early seismic and seabed gravity, continued to garner success and gradually gave way in the 1960’s to use of large digital multiclient surveys to expand beyond the basins immediately adjacent onshore production. As the ‘60’s to the 80’s progressed, however, production technology limited exploration to the shelf where failure or marginal success was achieved in basins such as Brazil’s Santos, Peru’s Talara, Agrentina’s Malvinas, and Guyana-Suriname Basins.
In the ‘90’s and 2000’s production technology advances in the US GOM enabled exploration in deeper waters, focused by more data sets, integration of DSDP and ODP drilling data, seismic stratigraphy, AVO, and plate tectonics (especially in the South Atlantic linking up Africa’s successes with South American target areas). Major deepwater joy followed in Brazil’s Campos-Santos, and more recently Mexico’s Perdido Foldbelt plus Guyana. Not all deepwater expansion has been roses, however, with in failures including Cuba, Barbados, Suriname, northeast Brazil, and Uruguay, plus relatively marginal or gas-only success in Colombia, Venezuela, Trinidad, French Guiana, north central Brazil and the Malvinas – Falklands regions.
We informally lump the successes of the last sixty years into ‘closed’ and ‘open’ productive systems. ‘Closed’ systems are highly structured with super seals and/or readily definable edges on seismic data - Mexico’s Sureste Basin and Brazil’s Campos-Santos, plus to a lesser extent the US-Mexico Perdido and Brazil’s Sergipe Alagoas. ‘Closed’ systems are very rich with major reserves now found primarily by drilling in-between existing discoveries in Brazil, plus some step-out in Mexico. Their heyday has decades to come, but will probably see a production decline before we move to a post-carbon world. ‘Open’ systems, conversely, are usually subtly structured or purely stratigraphic with undefinable boundaries on seismic – like Guyana. Vast regions with possible major accumulations in ‘open’ systems remain barely touched by the bit, from deepwater Barbados to Argentina on the Atlantic side, and higher risk Mexico to Chile on the Pacific side. A major effort is underway to identify more Guyanas resulting in new producing provinces, but at the present industry pace some large productive complexes may go undiscovered before we move to that post-carbon world.
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Regional Source Rock Maturity Modeling along the Campeche Salt Basin, Southern Gulf of Mexico
More LessSummaryExtending over 700 km along the southern Gulf of Mexico (GOM), the Callovian-Bajocian Campeche salt basin remains one of the least explored and drilled areas of the GOM basin. The objectives of this study include: 1) to image and structurally restore the top surface of the top of Paleozoic crystalline basement; 2) to understand the role of Paleozoic orogenic basement architecture and Triassic-Jurassic rift structures on total Mesozoic-Cenozoic sedimentary thickness; and 3) to use gravity data to determine crustal thickness and its related heat flow variations for the thermal maturity of source rocks within the basin. We integrate a grid of 23,600 line-km of 2D seismic reflection profiles with published wells and potential fields data. The potential fields data were processed to provide an improved image of the subsalt top basement surface at a depth of 6–15 km. The top basement morphology is a northward-dipping, subsalt surface in the depth range of 6–15 km. The top basement map reveals the 40–55-km-wide Campeche segment of the 670-km long GOM outer marginal trough, formed by necking of continental crust prior to the formation of late Jurassic oceanic crust. The elongate and fault-bounded basement depression of the outer marginal trough combined with the presence of "step-up fault" on its seaward edge onto more elevated Jurassic oceanic crust is imaged in high resolution using the tilt derivative of the Bouguer anomaly. We can also resolve the triangular terminus of the edge of late Jurassic oceanic crust that underlies the coastal area near San Andres Tuxtla. Mapping of 2D seismic lines reveals approximately 2–7 km of total sediment thickness along the slope of the Yucatan carbonate platform, which thickens up to 15 km along the axis of the outer marginal trough. Gravity inversion reveals an attenuated continental crustal thickness of ~10–20 km beneath the outer marginal trough and ~20–35 km beneath the less extended Yucatan block. Using this framework of crustal and sedimentary thickness, we present basin models to test hydrocarbon maturity based on Tithonian source rocks. We support our proposed areas of maturity with a compilation of direct hydrocarbon indicators from these sub-basins.
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Atlantic Margin Unexplored Play Fairway Sweet Spot with Significant Hydrocarbon Potential
Authors N. Hodgson and K. RodriguezSummarySummary is not available.
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Regional Source Rock Maturity and Petroleum Play Overview of the Deep-Water Yucatan Margin, Southern Gulf of Mexico
Authors J. Kenning and P. ManSummaryThe deep-water Yucatan margin remains one of the most underexplored areas of the Gulf of Mexico and due to a lack of well penetrations and systematic mapping, one of the least understood. Widespread oil slicks can be observed near salt structures positioned along the continent-ocean boundary, yet the maturity and distribution of hydrocarbon kitchen areas remains poorly constrained. In this study we use a grid of 2D post-stack depth migration (PSDM) seismic profiles tied to DSDP wells to map and analyze the stratigraphy, structure, and thermal maturity of potential source rock intervals across an area of >120,000 km². Six pseudo wells were positioned along dip and incorporate estimates of lithology, lithospheric thickness, and lithospheric heat-flow to help constrain a 3D maturity model based on regional mapping key intervals using the seismic data.
Integrated model results suggest that the primary Tithonian-age source rock interval reached oil maturity in the diapiric salt province near the continent-ocean boundary during the Oligo-Miocene. Inherent model uncertainty from lack of direct well penetration data in the local area was addressed by using analog well data, seismic observations, and by modeling multiple possible thermal scenarios. These alternate model scenarios were combined to create maturity risk maps for the area. Results suggest that the deeply buried, salt-involved minibasins along the outer marginal trough are low-risk and the upper slope high-risk for hydrocarbon generation and migration. Large, salt-related structural traps are located directly adjacent to oil kitchen areas within the deeply buried minibasins and require only vertical migration to charge. Normal faults bounding the salt minibasins provide possible migration pathways directly into the overlying salt-related structures, evidence for which is provided by clustering of oil slicks at the sea surface overlying these trends. To the southeast, gravitational sliding and collapse formed a series of salt-roller structures containing potential Norphlet equivalent reservoirs into which hydrocarbons may have migrated laterally up-dip from the deeper kitchen areas. Another potential play type includes Triassic-Jurassic rift structures in the sub-salt section; however, the analysis suggests that any potential reservoirs in this section would likely require a pre-Late Jurassic source rock to provide charge and would be associated with a higher risk of over maturity.
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Vaca Muerta - Stratigraphic Similitude to U.S. Shale
More LessSummaryThe Vaca Muerta shale in Argentina’s Neuquén Basin is at the forefront of shale plays being developed outside of North America. Production from the play has increased 600% over the past 5 years, a result of ramping investment from not only YPF and supermajors, but also small- to mid-cap and private operators. While single-well results are highly competitive with North American shale plays, the Vaca Muerta has struggled to achieve the same scale of activity seen in the U.S., partly reflecting economic and political headwinds. To propel themselves against these headwinds, Vaca Muerta operators look to improve well performance and economics by leveraging optimized completion design insights from North American shale plays.
We analyzed multidisciplinary datasets from all major North American shale plays and the Vaca Muerta. To perform subtle and objective geologic comparisons between the Argentine and North American plays, we performed electrofacies and clustering analyses using principal component analysis (PCA) with geologic features such as depth, gamma ray, resistivity, neutron porosity, bulk density, photoelectric factor and sonic. Using this to identify geologic analogues to the Vaca Muerta, we then investigated completion and production trends in comparable North American rock types. The analysis allows us to draw parallels between the shale plays that will drive insights into optimal completion technologies and methodologies in the continued development of the Argentine play.
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Thermal and Petroleum Systems Evolution in the Outboard Campos and Santos Basins, Offshore Brazil: Insights from 3D Basin Modelling
Authors A. Martín-Monge, Á. Carrasco, M. Masini, A. J. Olaiz, K. Buck, J. G. De Castilho and A. VayssaireSummaryOur knowledge of the evolution of passive margins has greatly improved over the last two decades. Field studies and observations from new seismic and well data have led to the development of new concepts on crustal architecture and rifting mechanisms in many continental margins. The continual search for new or overlooked petroleum domains has led exploration efforts towards more distal regions and consequently broadened our range of petroleum exploration.
The prolific Atlantic margins of the Campos and Santos Basins, offshore Brazil, are prominent areas where these new concepts were crafted and led to exploration success. Recent drilling activities offshore Campos and Santos, focused mainly on exploration leases acquired during recent ANP licensing rounds, illustrate the push towards more distal exploration. Although results have been mixed, some recent exploration wells have confirmed the presence of working petroleum systems in the outer basins and potential for liquid accumulations.
Here we present a regional 3D petroleum systems model constructed and calculated for an extensive area across Campos and Santos Basins ( Fig. 1 ).
The model integrates regional interpretation of seismic data with a meticulous mapping of crustal domains along the margin. A comprehensive compilation of present-day temperature and thermal maturity data was used for calibration purposes.
To assess the impact of the new models of margin development on the evolution of petroleum systems in the outer reaches of the Brazilian continental margins, the entire lithosphere was considered in temperature computations. The effect of radiogenic heat production is poised to be very different with respect to more proximal domains, but we can also anticipate a significant thermal imprint related to extreme crustal thinning (hyperextension) and various igneous events associated with attenuation and break-up. Special care was thus taken to properly define the thermal basement of our model. Thorough mapping of crustal domains along the area of interest was performed integrating seismic and potential fields data.
Sensitivity of several input parameters was tested, including different thermal scenarios and variations in source distribution, organic richness, and petroleum generation kinetics. This modelling exercise allowed us to move forward and become predictive in the assessment of the petroleum prospectivity of the study area. Model predictions highlight the potential for liquid petroleum in the outboard pre-salt play and have allowed us to identify new exploration opportunities in the area.
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Rift-Associated Magmatism in the Sergipe-Alagoas Basin and its Influence on Local Petroleum System
Authors M. Meirelles, C. Jardim, F. Mendonça and D. MachadoSummarySergipe-Alagoas Basin is located in Brazil’s northeast region and is one of many basins formed as a result of West Gondwana break-up. It has a well-known onshore portion that have being drilled since 1939 and contains an exposed and complete geological record since Jurassic’s pre-rift sequences (Souza-Lima et al. 2002 and Campos Neto et al. 2007 ). The shallow water region is also well described, being a pioneer in hydrocarbons discoveries at Brazil’s offshore in 1968. The constitution of ultra-deep-water sequences that occurs below the drift sequences, however, is extensively debated since 90’s works and will be the focus of this work. It was already interpreted as containing (i) a continuation of the pre-rift + berriasian-aptian rift sequences ( Pontes et al. 1991 ) and as (ii) thinning of the rift sequences with seaward dipping reflectors (SDR) marking the emplacement of oceanic crust ( Mohriak et al. 1997 , 1998 , 2000 ).
During the latest exploratory phase taking place in the basin, the wildcat well 1-SES-158 (1-BRSA-851-SES, as named by regulatory agency - ANP) brought more clarity to this matter, when a sequence of eoalbian pillow basalts (104Ma) was drilled and indicated alkaline composition ( Caixeta et al. 2015 ). Recent works incorporating this data proposed that Sergipe-Alagoas basin has been affected by multi-phased rifting processes at least until Albian ( Caixeta et al. 2015 ). Whereas in onshore and shallow water portion no evidence of magmatism was identified and salt deposition occurred, in ultra-deep water there are evidence of vulcanism covering a hyperextended continental crust ( Caixeta et al. 2015 ). This model proposes that the region where magmatism occurred at first corresponded to a basement high, caused by the rise of mantle material that limited the transitional sequences deposition in the proximal portion. This region was submitted then to hyperextension and volcanic and volcano-sedimentary sequences filled generated depocenters. Syn-depositional tectonism during transitional sequences deposition (aptian-albian sequences) was also described in both onshore and offshore portions, especially close to the basin faulted border and along aptian hinge line ( Cruz, 2008 ).
The crustal hyperextension resulted in a variety of volcanic geometries whose development culminated on the oceanic crust formation. These geometries include the earlier identified SDR ( Mohriak et al. 1997 , 1998 , 2000 ), lava-deltas, submarine mounts and volcanoes that provide interesting information about the final rifting dynamic as well as the environment conditions they were formed. The resulting relief has an important role in recently exploration of ultradeep portion of this basin since it has a strong influence in its petroleum system: either by forming depocentres for marine source rocks deposition or traps development for hydrocarbon in turbidites through differential compaction process. This subtle resulting structuration might have played an important role in oil and gas discoveries in offshore of Sergipe-Alagoas basin and is an key analogue for post-salt opportunities in basins without any type of strong tectonism forming traps.
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The Utility of Full Tensor Gradiometry in Geothermal Resource Mapping: An Example from the Basin and Range Province of Nevada
Authors A. Morgan, C. Murphy and J. BrewsterSummaryFaults play a key role in heat transport and permeability within extensional setting convective type geothermal plays. While faults can act as seals or conduits to fluid flow, their identification is paramount to the evaluation and assessment of geothermal resources.
Identification of faults relies heavily on surface expression or seismic reflection and/or refraction methods. Gravity data is also utilized to identify basin geometry, which will often indicate location of faults with high displacement if density contrast of a sufficient magnitude is present. Full Tensor Gradiometry measures the directional gradients of the gravity field, allowing the interpreter to quantify subtle changes in density contrast associated with faulting, provided sufficient magnitude and offset are present.
Full Tensor (Gravity) Gradiometry (FTG) data acquired over the Crescent Valley geothermal field in Nevada reveals previously unmapped faults and identifies their relationship to the regional structural framework. Intersections of faults are additionally identified through lineament extraction methodologies, which in turn contribute to the identification of favourable geothermal prospects. Additionally, 2D modelling of FTG and seismic reflection data can be used quantitatively to assess permeability of shallow sedimentary units.
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Early Post-Rift Dynamo-Thermal Subsidence and Stratigraphic Architecture as Magma-Rich Rifted Margins Move off Plumes
Authors J. Pindell, T. Heyn and K. ReuberSummaryMagma-rich rifting and breakup generally occur over rising mantle plumes; magma-poor rifting and breakup do not. Plumes generate up to 2km dynamic elevation at magma-rich rifts, outcompeting synrift subsidence in both active and ancient magma-rich margins, evidenced by top-rift unconformities. Magma-rich margins also show anomalously fast/large early post-rift subsidence, evidenced by thick, short-lived sag/salt sections with limited faulting. Syn-depositional thermal subsidence cannot be responsible for the rapid subsidence alone, and the paucity of faulting suggests it is not tectonic. Dissipation of dynamic topography (dynamic subsidence) is the additional parameter responsible, acting together with thermal subsidence. We depict the magma-rich central South Atlantic and Gulf of Mexico salt-bearing margins relative to former plumes, showing sag/salt deposition occurs as the margins migrate off plume flanks while rifting continues immediately over the plumes. However, the sub-sag/salt basement must first be extended/eroded during dynamic elevation to fall below its pre-uplift elevation. We propose new terms: "dynamo-thermal subsidence" creates "dynamo-thermal accommodation", the sum and combined result of dynamic plus thermal subsidence, respectively. It is fast enough to negate the need for deep, sub-sea level, subaerial depressions for accumulation of thick sag/salt sections. Differences in dynamic elevation during salt deposition also explains differences in autochthonous salt thickness.
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Integrated Model for the Tectonic Development of Southern Mexico/Central America and the Chiapas-Campeche Basin: Plate Motions, Geochronology, Thermochronology, Paleomagnetism, Structural Geology and Depositional Source to Sink Models
Authors J. Pindell, D. Villagomez, R. Molina, R. Graham and C. SteffensenSummaryWe integrate refined analyses of plate motions, geochronology, thermochronology, paleomagnetism, structural geology and depositional source to sink models to define the primary and inter-related aspects of the geological evolution of Southern Mexico and Central America. The model is the result of a 10-year research program conducted mainly by Tectonic Analysis Ltd. and UNAM Querétaro, funded largely by industry. Primary Late Cretaceous to Recent evolutionary events are: 1) collision and emplacement of the Greater Antilles Arc (Nicaragua Rise–Jamaica portion) along southern Yucatan (Chiapas to Belize) and east of the continental core of the Chortis Block, in the Maastrichtian; 2) dislocation of the continental core of the Chortis Block from the Oaxaca coastline in the late Maastrichtian, probably due to flat slab Laramide subduction and associated plate-interface traction; 3) Paleocene-Recent eastward migration of the composite Chortis–Nicaragua Rise–Jamaica belt, as part of the Caribbean Plate since the late? Eocene, with strong transpression in the Paleogene which emplaced the Chontal/Chivela nappes onto the former south-facing Pacific margin of Tehuantepec and southern Yucatán; 4) progressively eastward inception of subduction along Southern Mexico in the wake of the migrating Chortis Block, causing uplift and erosion of the Xolapa (Eocene-early Miocene), Guichicovi (Oligocene), and eventually Chiapas Massif (Miocene). The Chiapas Massif rotated clockwise by about 20° in the middle Miocene as shortening ensued in the Chiapas Foldbelt, but the main period of uplift of the massif has been since 10 Ma (Late Miocene), due to the progressive flattening of subduction beneath it. Beginning at about 11 Ma, the northern flank of the Chiapas Foldbelt (Akal High) gravitationally broke away to the NNW from the onshore foldbelt to create the Macuspana Basin, detaching on autochthonous (Bajocian) salt. At about 4 Ma, the same occurred in the Comalcalco Basin; this updip extension manifests itself as downdip compression in more northerly portions of the offshore Campeche Salt Basin. For Paleocene-middle Miocene time, clastic sediment was able to pass from plate boundary source areas to the southern Veracruz and Gulf of Mexico basin, without topographic impedance by the Chiapas Massif. The Nanchital conglomerate of the western Chiapas Foldbelt is the coarsest terrigenous clastic depositional Cenozoic unit of the region, probably comprising more proximal sections of hydrocarbon-rich slope-fan reservoirs found in the more distal Sureste Basin of the southern Gulf of Mexico fringe. Traditionally, the felsic igneous and metamorphic components of this conglomerate were assumed to derive from the Permian basement of the nearby Chiapas Massif. However, zircon U–Pb dating of five Nanchital conglomerate clasts from the Chiapas Foldbelt and also igneous exposures in SW Tehuantepec indicates that the Nanchital conglomerate’s catchment area included the western Isthmus of Tehuantepec up to the end of middle Miocene time, after which the more proximal Chiapas Massif and Chiapas Foldbelt likely became the dominant clastic source areas. We propose a temporal framework for viewing Neogene and Quaternary clastic supply to the southern Gulf of Mexico.
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Assessing the Regional Effects of the Miocene-to-Recent Panama Arc Collision and its Influence on the Maturation and Distribution of Hydrocarbons in Northwestern South America and Southern Central America
More LessSummaryThe northwestern margin of South America has undergone different phases of deformation since the late Paleozoic related to continental and arc collisions, strike-slip events, and subduction of oceanic plateaus. The purpose of this talk is to isolate the effects of the most recent of these superimposed tectonic events - the collision of the Panama arc with the northwestern margin of South America - and to assess its impact on the regional distribution and maturation of hydrocarbons. The precise age of the Panama collision has remained a topic of continuing research. Geologic work that includes onland-based structural mapping, radiometric dating, and paleomagnetism has shown that the Panama area formed as a semi-emergent island chain from the Oligocene (30 Ma) - but the emergent isthmus and barrier separating the Caribbean and Pacific Oceans was not fully established until the Late Pliocene (2.8 Ma). To improve constraints on the timing of the actual collision of the island arc basement rocks of Panama with the previous orogenic belts of northwestern Colombia, we have compiled: 1) previous thermochronological work on the arc and continental basement of both northwestern South America and Panama; 2) thickness and ages of the clastic wedges eroded from this basement areas and summarized this information into burial curves from induvial basins; 3) the ages of known angular unconformities within the deformed sedimentary basins; and 4) compiled and restored the measured lengths of now subducted slabs beneath both northwestern South America and Panama. These data show that: 1) the timing of the collision occurred at least since the late Miocene - about 13 Ma - which resulted in the uplift of the northern Andes, clastic flooding including the Magdalena submarine fan that has accelerated to the present-day and unleashed hydrocarbon generation and expulsion in offshore Caribbean depocenters ; 2) a large basement arch extends eastward from Panama beneath northwestern South America and forms a hydrocarbon-poor zone as few deep basins are present in this area of uplifted basement; and 3) deformational effects have propagated eastward into the Cordillera Oriental and Llanos basins and triggered a pulse of deep burial and maturation of hydrocarbons.
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