Llanos Basin Research Articles

Water flow, oil biodegradation, and hydrodynamic traps in the Llanos Basin, Colombia

In this study, we provide new data to understand the groundwater flow patterns in the Llanos Basin and their impact on oil biodegradation and the geothermal regimes as well as how the structural styles and anthropogenic activities impact these patterns. Previous studies suggest an active flow of groundwater and variable salinities whose spatial pattern is apparently unrelated to topographically driven groundwater flow. These observations have led to different hypotheses regarding the influence of groundwater flow on Llanos Basin geothermal gradients and oil biodegradation. In this contribution, we present data regarding the hydraulic heads, salinities, geothermal gradients, and structural styles of the Llanos Basin to propose hypotheses explaining these observations. Structural cross sections and subsurface stratigraphic correlations allow us to suggest that the pattern of flow is best explained by a correlation between groundwater flow and structural styles. A basement map of the Llanos Basin confirms that the most important factor controlling geothermal gradients is the type of basement, whereas the factor of groundwater flow appears to be of secondary importance. The evolution of the basin and the frequent absence of correlation between fresh water and the more biodegraded oils support the interpretation that biodegradation is controlled by an older flow of water that started as early as the Oligocene. Finally, mass balances suggest that the temporal scales and volumes of groundwater flow are much larger than the scales observed during the development of the oil fields.

Tectonic evolution of petroleum systems within the onshore Llanos Basin: Insights on the presence of Orinoco heavy oil analogs in Colombia and a comparison with other heavy oil provinces worldwide

Economic accumulations of hydrocarbons in the onshore Llanos Basin of Colombia are characterized by a central zone (Casanare province) with greater than 20° API gravity oils and a southern province with biodegraded, less than 15° API gravity oils. To date, no conceptual model successfully explains this spatial zonation. In this paper, we employ multiple one-dimensional time–temperature models to map the kitchens for three different source rocks and compare maturity levels through the Cenozoic with the presence or absence of reservoir, seal, overburden, and traps in paleogeographic maps of the Llanos Basin. We find that the Llanos Basin Cenozoic petroleum migration and charge may have been governed by a sedimentary–structural evolution tied to the adjacent orogenic belt in which (1) Paleogene stratigraphic traps developed in the south, as favored by a more segmented basement and potentially transpressional stresses; (2) a subsequent Neogene phase with more pervasive east-dipping low-displacement normal fault traps was discovered; and (3) a final Pliocene–present day phase of contractional traps was found in the easternmost foothill areas. When compared with the evolution of several potential kitchens, we suggest that Upper Cretaceous rocks from the Eastern Cordillera are the primary hydrocarbon source in the zone of heavy biodegraded oils to the south, whereas Lower Cretaceous and selected terrigenous Upper Cretaceous source rocks are largely responsible for the younger Neogene contractional traps of the foothills. This evolutionary pattern for the Llanos Basin favors the presence of smaller but numerous hydrocarbon accumulations rather than the broader zones of heavy oils, as found in the Orinoco belt of Venezuela.

Hydraulic fracturing considerations: Insights from analogue models, and its viability in Colombia

Fracking is being considered around the world as a potential method in the hydrocarbons extraction given the increase of production in USA and Canada during the last years with its implementation. The most criticized feature of the technique of fracking is the contamination of underground waters by fluids connected through the generated and/or pre-existing fractures. This work evaluates the viability of fracking in Colombian territory based in the study of the analogue models, considering the elastic properties of the reservoir rocks using gelatin, sand and clay that apply scaled pressure (lithostatic pressure to scale). The gelatin is used to simulate the reservoir zone, the clay will simulate one sail and the sand will simulate reservoir rocks of underground water. As a result seven different models were generated. There were simulated as 1) the anisotropy presence, 2) the rock sail presence, and 3) the injection groove of fluids in the pipeline. The completed models show that the required distance between the unconventional reservoir and underground waters to avoid contamination by fluids is ~200 m, also between the hydraulic fracturing point and the faults that connect with the shallows area is ~350 m, and it is suggested to study in detail the permeability of both: nearby faults and the rock sail. Two Colombian basins (Magdalena Midland Valley and Llanos) were taken as the main base to analyze the assessment of fracking according to the previously mentioned results, concluding that it is viable particularly in areas like Llanos Basin and with some precautions in similar zones to Magdalena Midland Valley Basin.

The field test confirms the prognosis of the location of giant oil and gas fields in the Andes of South America made in 1986

1986 saw the publication of a prognostic map for discovering giant oil and gas fields in the Andes in South America based on the recent block structure of the Earth’s crust. The model assumes that petroleum moves to the traps through permeable channels created at the intersection of deep faults. The technology of creation that the prognostic maps use involves (1) maps of morphostructural zoning, which outline the morphostructural knots (intersections of faults), and (2) a pattern recognition program that identifies knot-containing giant oil/gas fields. It was forecasted that, in the Andes of South America 11 knots, which had not been developed at that time, contain giant oil or gas fields. These 11 sites covered only 15% of the total area of all the Andes basins. Since then, six giant oil/gas fields have been discovered in the Andes region: Cano-Limon, Cusiana, Capiagua, and Volcanera (Llanos basin, Colombia), Camisea (Ukayali basin, Peru), and Incahuasi (Chaco basin, Bolivia). All these discoveries were made in places shown on the 1986 prognostic map as promising areas.

GEOCHEMICAL EVALUATION OF CRUDE OILS FROM THE CARACARA AND TIPLE AREAS, EASTERN LLANOS BASIN, COLOMBIA: PALAEO BIODEGRADATION AND OIL MIXING

This study presents an organic geochemical characterization of heavy and liquid oils from Cretaceous and Cenozoic reservoir rocks in the Tiple and Caracara blocks in the eastern Llanos Basin, Colombia. Samples of heavy oil were recovered from the Upper Eocene Mirador Formation and the C7 interval of the Oligocene – Miocene Carbonera Formation; the liquid oils came from these intervals and from the Cretaceous Guadalupe, Une and Gachetá Formations. The heavy oil and most of the liquid oils probably originated from multiple source rocks or source facies, and showed evidence of biodegradation as suggested by the coexistence of n‐alkanes and 25‐norhopanes. The results indicate a close genetic relationship between the samples in the Carbonera (C7 interval), Mirador and Guadalupe Formation reservoirs. These petroleums are interpreted to result from at least two separate oil charges. An early charge (Oligocene to Early Miocene) was derived from marine carbonate and transitional siliciclastic Cretaceous source rocks as indicated by biomarker analysis using GC/MS. This initial oil charge was biodegraded in the reservoir, and was mixed with a later charge (or charges) of fresh oil during the Late Miocene to Pliocene. A relatively high proportion of the unaltered oil charge was recorded for heavy oil samples from the Melero‐1 well in the Tiple block, and is inferred to originate from Cenozoic carbonaceous shale or coaly source rocks. Geochemical parameters suggest that oils from the Gachetá and Une Formations are similar and that they originated from a source different to that of the other oil samples. These two oils do not correlate well with extracts from transitional siliciclastic source rock from the Upper Cretaceous Gachetá Formation in the Ramiriqui‐1 well, located in the LLA 22 block to the north. By contrast, one or more organofacies of the Gachetá Formation may have generated the heavy oil and most of the liquid oil samples. The results suggest that the heavy oils may have formed as a result of biodegradation at the palaeo oil‐water contact, although deasphalting cannot entirely be dismissed.

Stratigraphic architecture of incised valleys and unincised channel systems in the Carbonera Formation (C6-C1 members: Upper Oligocene – Lower Miocene), Llanos basin, Colombia

This work presents a sequence stratigraphic framework for the Upper Oligocene – Lower Miocene C6-C1 members of the Carbonera Formation in the Llanos basin, Colombia. In the interval corresponding to the C5 member, facies associations that comprise middle shoreface, tidal channels and bars, tidal flat deposits, brackish bay, tidal-fluvial channels and central estuary have been identified through the integration of core descriptions and wireline logs. The vertical assemblage of the recognized facies associations permits the definition of several cycles of transgression and regression, as well as episodes of relative sea-level fall and their consequent fluvial incision. Basinward shifts of facies, lateral changes in well-log motifs and seismic amplitude anomalies allow the interpretation of incised-valley systems overlying deposits associated with marginal and shallow marine environments, which also present channelized sand bodies. Consequently, the sedimentary and stratigraphic architecture is composed of an interspersed set of channels with different genetic origins and contrasting potentials in terms of petroleum production. Maximum flooding surfaces, subaerial unconformities and transgressive ravinement surfaces are the significant stratigraphic surfaces identified, which separate progradational and retrogradational stages and define sequence boundaries.In addition to the C5 member, a sequence stratigraphic model for the interval corresponding to the C6-C1 members of the Carbonera formation is presented based on cuttings, well-log stacking patterns and interpretation of 3D seismic horizon and time slices. In total, nine regressive-transgressive cycles (i.e., genetic stratigraphic sequences) are interpreted for the interval studied. The proposed stratigraphic framework relates oil occurrences and currently producing intervals with stratigraphic surfaces and permits a consistent classification of the petrophysical properties, establishing several families that are genetically related.The sedimentological descriptions of the Carbonera C5 member and the proposed sequence stratigraphic model highlight the marine influence in the deposition of the Carbonera Formation. Furthermore, this work emphasizes the role of relative sea-level fluctuations in deposition and erosion in coastal areas during tectonically active periods in the foreland Llanos basin.

Application of spectral inversion and fuzzy logic interpolation in post-stack resolution enhancement on a seismic volume of the Colombian llanos basin

espanolRESUMEN Para mejorar la interpretacion estratigrafica de datos sismicos 3D se procuro aumentar la resolucion vertical mediante una inversion espectral (Puryear & Castagna, 2008; Qiu, Junhua, Xiaohui, Hu, & Lei, 2016) y la resolucion lateral usando una interpolacion de logica difusa (Souverville et al., 2015). La inversion espectral mediante algoritmo genetico y la interpolacion se implementaron en Matlab®, y se probaron en datos sinteticos asi como en una imagen digital de alta resolucion, donde ambos algoritmos demostraron un buen desempeno. Finalmente, al aplicarse a un volumen sismico de la Cuenca Llanos en el intervalo C7 de la Formacion Carbonera (Colombia), se consiguio un cubo sismico de mayor resolucion en espacio y tiempo. Se estimaron los atributos sismicos varianza y antes y despues de aplicar la inversion espectral y la interpolacion, observando que la aplicacion de ambos daba mayor interpretabilidad a las facies estratigraficas. La interpretacion de tres mapas sismicos a diferentes tiempos (time slices) permitio inferir ambientes de formacion que fueron validados con informacion de pozo. EnglishABSTRACT To improve the stratigraphic interpretation of 3D seismic data it is pursued to increase the vertical resolution by means of a Spectral Inversion (Puryear & Castagna, 2008; Qiu, Junhua, Xiaohui, Hu, & Lei, 2016) and the lateral resolution using a fuzzy logic interpolation (Souverville et al., 2015). Both the Spectral Inversion using a genetic algorithm and the interpolation are implemented in Matlab®, and tested in synthetic data and in a high resolution digital image, where both algorithms showed good performance. Finally, when applied to the C7 unit of the Carbonera formation in a seismic volume of the Llanos Basin (Colombia), a seismic cube of greater resolution in space and time was obtained. The seismic attributes variance and sweetness were estimated before and after applying the Spectral Inversion and interpolation, noting that applying both gave higher interpretability to the stratigraphic facies. The interpretation of three different time slices allowed inferring formation environments that were validated with well information. portuguesRESUMO Visando melhorar a interpretacao estratigrafica de dados sismicos 3D procuramos aumentar a resolucao vertical mediante uma inversao espectral (Puryear & Castagna, 2008; Qiu, Junhua, Xiaohui, Hu, & Lei, 2016) e a resolucao lateral empregando uma interpolacao de logica difusa (Souverville et al., 2015). A inversao espectral mediante algoritmo genetico e a interpolacao foram implementadas em Matlab®, sendo testadas em dados sinteticos, bem como na imagem digital de alta resolucao, onde ambos algoritmos demostraram um bom desempenho. Finalmente, ao ser aplicado a um volume sismico da Bacia Llanos no intervalo C7 da Formacao Carbonifera (Colombia), conseguimos um cubo sismico de maior resolucao em espaco e tempo. Foram calculados os atributos sismicos variância e antes e depois da aplicacao da inversao espectral e a interpolacao, observando que a aplicacao de ambos resultava em maior interpretabilidade as facies estratigraficas. A interpretacao de tres mapas sismicos a diferentes tempos (time slices) permitiu inferir ambientes de formacao que foram validados com informacao de poco.

Español

The Llanos Basin had been studied by their hydrocarbon potential. However, it has been based on lithostratigraphy. And that is completely descriptive and no interpretative. This paper will give a chronostratigraphy interpretation for Oligocene sequences, based on well log information, seismic data and biostratigraphy, integrated with sequential tools. The main target is continuity and paleo-environmental relationships of sandstone bodies. Keywords : seismic-stratigraphy, sequential stratigraphy, chronostratigraphic.

The distribution of thermogenic, bacterial and inorganic fluid sources in the petroleum systems of the Llanos Basin (Colombia) – Insights from the noble gases and carbon stable isotopes

The Colombian Andean foreland is a rich petroleum province, where various source rocks and an active circulation of fresh water are present in the subsurface, resulting in a complex fluid mixture within the reservoirs. Moreover, some of the traps are shallow, and low °API gravity oils are found. Massive meteoric water infiltration and local biodegradation have been proposed to explain these observations, but require some in-depth investigation to be confirmed. In order to provide some new insights into the Llanos Basin petroleum system, we performed a natural gas geochemical survey over different areas of the basin, including stable isotopes of hydrocarbon, non-hydrocarbon and noble gases. Results show that the influence of meteoric water infiltration is dominant in the shallow area eastward, but decreases towards the deepest part of the basin westward. A general gas/oil phase separation differentiates gas-depleted biodegraded, shallow reservoirs from deep gas-rich less-altered reservoirs. Data suggest that there is a shallow biodegradation associated with meteoric water circulation in the Carbonera Fm, while some of the deeper heavy oils (Mirador, Une fms) were more likely produced by an early mature source rock. However, biodegraded oil later mixed with less altered oil and associated gas are plausible. This study also indicates a contribution of mantle fluids in the deepest parts of the basin near the contact with the Guaycaramo Fault System. There, older rift sequences may have recorded mantle fluid fluxes, or alternately the presence of diffuse mantle fluxing along the deep-rooted thrust front during the formation of the Llanos Basin.

Sclerites and possible mouthparts of Wiwaxia from the temperate palaeolatitudes of Colombia, South America

The problematic mollusc Wiwaxia is perhaps the most widely distributed non-mineralized Cambrian metazoan, but has only been reported from palaeotropical latitudes. Here, we describe mid-Cambrian (Drumian, c. 504 Ma) sclerites and possible tooth arrays from the northern Llanos Basin, Colombia, recovered from drilled ditch cuttings by palynological processing – demonstrating that pristine material and low-manipulation processing are not essential to the recovery of Small Carbonaceous Fossils. This, the first report of Wiwaxia from South America, substantially expands Wiwaxia's geographic range into the high palaeolatitudes.

A minute ostracod (Crustacea: Cytheromatidae) from the Miocene Solimões Formation (western Amazonia, Brazil): evidence for marine incursions?

A huge wetland (the ‘Pebas system’) covered western Amazonia during the Miocene, hosting a highly diverse and endemic aquatic fauna. One of the most contentious issues concerns the existence, potential pathways and effects of marine incursions on this ecosystem. Palaeontological evidences (body fossils) are rare. The finding of a new, presumably marine ostracod species (Pellucistoma curupira sp. nov.) in the upper middle Miocene Solimões Formation initiated a taxonomic, ecological and biogeographical review of the genus Pellucistoma. We demonstrate that this marine (sublittoral, euhaline), subtropical–tropical taxon is biogeographically confined to the Americas. The biogeographical distribution of Pellucistoma largely depends on geographical, thermal and osmotic barriers (e.g. land bridges, deep and/or cold waters, sea currents, salinity). We assume an Oligocene/early Miocene, Caribbean origin for Pellucistoma and outline the dispersal of hitherto known species up to the Holocene. Pellucistoma curupira sp. nov. is dwarfed in comparison to all other species of this genus and extremely thin-shelled. This is probably related to poorly oxygenated waters and, in particular, to strongly reduced salinity. The associated ostracod fauna (dominated by the eurypotent Cyprideis and a few, also stunted ostracods of possibly marine ancestry) supports this claim. Geochemical analyses (δ18O, δ13C) on co-occurring ostracod valves (Cyprideis spp.) yielded very light values, indicative of a freshwater setting. These observations point to a successful adaptation of P. curupira sp. nov. to freshwater conditions and therefore do not signify the presence of marine water. Pellucistoma curupira sp. nov. shows closest affinities to Caribbean species. We hypothesize that Pellucistoma reached northern South America (Llanos Basin) during marine incursions in the early Miocene. While larger animals of marine origin (e.g. fishes, dolphins, manatees) migrated actively into the Pebas wetland via fluvial connections, small biota (e.g. P. curupira sp. nov.) were phoretically freighted and developed freshwater tolerance over long timescales.http://zoobank.org/urn:lsid:zoobank.org:pub:886C6476-393D-4323-8C0E-06BB8BD02FD9

Stress field estimation based on focal mechanisms and back projected imaging in the Eastern Llanos Basin (Colombia)

At least 156 earthquakes (Mw 2.8–4.4) were detected in Puerto Gaitán, Colombia (Eastern Llanos Basin) between April 2013 and December 2014. Out of context, this figure is not surprising. However, from its inception in 1993, the Colombian National Seismological Network (CNSN) found no evidence of significant seismic events in this region. In this study, we used CNSN data to model the rupture front and orientation of the highest-energy events. For these earthquakes, we relied on a joint inversion method to estimate focal mechanisms and, in turn, determine the area's fault trends and stress tensor. While the stress tensor defines maximum stress with normal tendency, focal mechanisms generally represent normal faults with NW orientation, an orientation which lines up with the tracking rupture achieved via Back Projection Imaging for the study area. We ought to bear in mind that this anomalous earthquake activity has taken place within oil fields. In short, the present paper argues that, based on the spatiotemporal distribution of seismic events, hydrocarbon operations may induce the study area's seismicity.

Combined Petroleum System Modeling and Comprehensive Two-Dimensional Gas Chromatography To Improve Understanding of the Crude Oil Chemistry in the Llanos Basin, Colombia

Important properties of a crude oil, such as viscosity, are determined by the crude oil’s chemical constituents. In particular, viscosity is highly dependent on the asphaltene content. Various processes that act on reservoir crude oils can alter chemical composition, such as aspahltene content, and therefore impact important crude oil properties. In many basins, such as the Llanos basin in Colombia, processes such as biodegradation, water washing, and multiple charging can contribute to asphaltene and viscosity variations. The considerable complexity of the problem requires a multidisciplinary workflow to understand the main factors that influence the quality of reservoir crude oils and their gradients. Here, we perform comprehensive two-dimensional gas chromatography with flame ionization detection and with mass spectrometry on samples of known provenance, combined with petroleum system modeling, to develop an understanding of the primary factors controlling asphaltene content and viscosity in a reservoi...

Petroleum systems of the Eastern Cordillera, foothill basins, and associated Llanos basin: Impacts on the prediction of large scale foreland and foothill petroleum accumulations

Colombia’s recent oil boom, which began in about 2003, features the notable achievement of making Colombia one of the few countries in the world to surpass past oil peaks (i.e., maximum historical oil production), a phenomenon that among the western countries only the United States has approached with the shale/tight oil boom. In the 1990s, after the discoveries of Cusiana, Cupiagua (Cazier et al., 1995; Cooper et al., 1995) and other oil fields, Colombia reached a maximum daily production of about 830,000 BOPD in 1999, but soon afterwards started a steep decline. However, after 2003 daily production reached a minimum of 541,000 BOPD and started to grow steeply again in 2007 until past peaks in oil production were surpassed in 2011. During the 1990s peak as well as the current maximum the key component of Colombia’s oil production has come from the Llanos basin and associated eastern foothills, which ranked as the fourth most favorable basin in the world in terms of exploration success rate (IHS, 2010). However, until now there has been no comprehensive published study that explains this success or predicts the potential for finding future accumulations. In this special issue, we intend to provide the first comprehensive view of the Llanos basin and the adjacent hinterland of the Eastern Cordillera with the ultimate goal of explaining the existing accumulations and predicting the potential for new ones, to the extent allowed by the confidentiality of the organizations involved. Reyes-Harker et al. (2015, this issue) present the first paleogeographic reconstruction of the Llanos and Eastern Cordillera, including for the first time the most detailed and recent data regarding the uplift history of the Eastern Cordillera (i.e., Mora et al., 2008, 2010, 2013a, b; Parra et al., 2009a, b, 2010, 2012; Horton et al., 2010a, b …

Hyperspectral imaging for the determination of bitumen content in Athabasca oil sands core samples

New biostratigraphic zonations, core descriptions, sandstone petrography, facies analysis, and seismic information are compared with published detrital and bedrock geo- and thermochronology to build a Cenozoic paleogeographic reconstruction of the Andean retroarc region of Colombia, encompassing the ancestral Central Cordillera, Middle Magdalena Valley, Eastern Cordillera, and Llanos basin. We identify uplifted sediment source areas, provenance domains, depositional environments, and thickness changes to propose a refined paleogeographic evolution of eastern Colombia. We conclude that Cenozoic evolution of the northernmost Andes includes (1) a period of contractional deformation focused in the Central Cordillera and Middle Magdalena Valley that may have started by the Late Cretaceous, although thermochronological data points to maximum shortening and exhumation during the late Paleocene; (2) a period of slower deformation rates or even tectonic quiescence during the middle Eocene; and (3) a renewed phase of contractional deformation from the late Eocene to the Pleistocene/Holocene expressed in provenance, bedrock thermochronology, and increased subsidence rates in the Llanos foreland. The sedimentary response in the Llanos foreland basin is controlled by source area proximity, exhumation and shortening rates, relationships between accommodation and sediment supply, as well as potential paleoclimate forcing. This new reconstruction changes the picture of Cenozoic basin evolution offered by previous reconstructions, providing an updated chronology of deformation, which is tied to a more precise understanding of basin evolution.

Controls on petroleum composition in the Llanos basin, Colombia: Implications for exploration

Physical and geochemical characteristics of produced petroleum from the central region of the Llanos basin, Colombia, were analyzed to understand the petroleum charge history and alteration processes. Petroleum properties in the study area are the result of the complex charge history of the oil fields. The amount of gas in fluids is controlled by the migration distance from the late or, possibly, the current generation kitchen located beneath the foothill deformation zone. Gas influx decreases toward the foreland domain, as indicated by lower values of the gas–oil ratio and saturation pressure. The API gravity of the oil samples is mainly controlled by the intensity of biodegradation. Marine-sourced oils accumulated in shallow reservoirs of the foreland prior to the onset of Andean deformation. Those fluids were subjected to different levels of biodegradation, depending on the time they remained at reservoir temperatures lower than 80°C (176°F) and before being buried to their maximum depth. Geochemical data suggest multiple charge pulses from different source kitchens of two main types of source rocks, as well as different biodegradation levels. The proposed petroleum charge and alteration model allows prediction of the temperature history of a reservoir and the most likely physical properties of the petroleum at a specific location. The model can be used as an exploration tool to assess the risk of charge prior to drilling in unexplored areas of the basin.

Precambrian–Pleistocene tectno-stratigraphic evolution of the southern Llanos basin, Colombia

The Llanos basin, located in the eastern region of Colombia, northwestern South America, is an Andean foreland basin between the Eastern Cordillera (Colombian Andes) and the Guyana Precambrian shield. The basin is the latest stage of a complex multiphase evolution that began in the Paleozoic at the latest. A Paleozoic–Pleistocene basin evolution model is presented based on a regional, two-dimensional, industry seismic data set and well-log observations for the southern part of the basin. Five tectono-stratigraphic sequences were identified: (1) lower Paleozoic depocenters preserved along inverted Neoproterozoic basement blocks; (2) an upper Paleozoic marine sequence folded and faulted in the late Paleozoic during assembly of Pangea; (3) Upper Cretaceous–Paleocene shallow marine sediments deposited in a distal foreland basin related to uplift of the Western and Central Cordilleras of Colombia, the sequence pinches out against a Paleozoic hinge or foreland bulge area; (4) an Eocene–Miocene foreland basin related to uplift of the Eastern Cordillera resulting in a wedge geometry; and (5) Pliocene–Pleistocene fluvial deltaic rocks overfilling the foreland basin. Reactivation of Paleozoic structures occurs at the top of this sequence with the development of anticlinal structures. Present-day stress fields indicate that subduction of the Nazca plate beneath South America may be responsible for reactivation of Paleozoic structures. Inversion of north–south structures with the Neoproterozoic basement is interpreted to be responsible for the Paleozoic and Pleistocene deformation, whereas Cenozoic deformation is related to the two main stages of foreland development of the basin. To the east, where the Paleoproterozoic basement is present, no deformation is interpreted.

Petroleum system modeling in the Eastern Cordillera of Colombia using geochemistry and timing of thrusting and deformation

In the present study, stratigraphic data from cores and outcrop sections are integrated with data on thermal maturity, organic facies, and thermochronometric information to reconstruct the tectonic and associated petroleum system evolution of the eastern foothills thrust belt along the Colombian Eastern Cordillera, one of the most prolific hydrocarbon provinces in northern South America. Sedimentary and tectonic burial of the foreland autochthon caused maturation of the Coniacian to Santonian shallow marine Chipaque Formation, resulting in successive and diachronous episodes of hydrocarbon migration and trapping. One-dimensional and two-dimensional maturation modeling indicates that oil generation from the Chipaque Formation began at the Paleocene-Eocene boundary (55 Ma) in the southern parts of what is now the Eastern Cordillera and progressed to the north. By the late Oligocene, tectonic inversion of the Eastern Cordillera exhumed most of these kitchens, terminating the oil generation from the Chipaque Formation. Kitchens migrated northward and eastward during the Oligocene and early Miocene. Because of the absence or subsequent erosion of traps, it is likely that the southernmost source rocks expelled most of their oil without any appreciable accumulation. Our modeling indicates that there were two important kitchens during the Cenozoic. The larger of the two was located in the present-day Eastern Cordillera, and it was most productive in the late Eocene–early Oligocene. The second kitchen, which generated oil throughout the Neogene, was located in the foredeep of the Llanos basin, adjacent to the mountain front. Considerable amounts of oil from this recent pulse have accumulated in both deep and shallow reservoirs along the eastern foothills. The modeled reservoir charge history also explains the substantial biodegradation of oils in reservoirs that are today much too deep to support the process. Biodegradation must have occurred when the reservoirs were shallower and at cooler temperatures, and they remained active until the reservoirs were buried to depths where temperatures were high enough to prevent further bacterial activity.

Temporal and spatial distribution of tectonic events as deduced from reworked palynomorphs in the eastern Northern Andes

In Colombia, palynology has been widely used as a biostratigraphic tool in oil exploration over the last two decades and, as a result of these efforts, an understanding of the chronostratigraphic range of thousands of palynomorph species is now available. Furthermore, because of their relative resistance to physical and chemical degradation, palynomorphs can often survive several tectonic-erosive cycles, allowing them to be used as unique tracers of long-term sedimentological changes. In this work, we use the palynological record from wells and outcrops in the Llanos foothills and the Llanos basin of Colombia to establish the intensity of Cenozoic reworking and its relationship to the tectonic evolution of the Colombian Andes. Using this approach, we were able to discern several tectonic episodes associated with the uplift of the Eastern Cordillera. We documented three periods of either faster erosion in the hinterland or more widespread areas being eroded in the catchment areas (late Paleocene–early Eocene, early to mid Miocene and Pliocene) and two periods of tectonic quiescence (mid-Eocene and mid–late Miocene). These periods correlate well with the deposition of different elements of the petroleum systems in the Llanos basin of Colombia (seals and reservoirs).

Active mountain building along the eastern Colombian Subandes: A folding history from deformed terraces across the Tame anticline, Llanos Basin

Research Article| September 01, 2015 Active mountain building along the eastern Colombian Subandes: A folding history from deformed terraces across the Tame anticline, Llanos Basin Gabriel Veloza; Gabriel Veloza † 1Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA †E-mail: gvelozaf@ku.edu. Search for other works by this author on: GSW Google Scholar Michael Taylor; Michael Taylor 1Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA Search for other works by this author on: GSW Google Scholar Andrés Mora; Andrés Mora 2Ecopetrol–Instituto Colombiano Del Petroleo, Km7 Via Bucaramanga-Piedecuesta, Piedecuesta-Santander, Colombia Search for other works by this author on: GSW Google Scholar John Gosse John Gosse 3Department of Earth Sciences, Dalhousie University, Halifax B3H 4R2, Canada Search for other works by this author on: GSW Google Scholar GSA Bulletin (2015) 127 (9-10): 1155–1173. https://doi.org/10.1130/B31168.1 Article history received: 18 Jul 2014 rev-recd: 18 Dec 2014 accepted: 26 Jan 2015 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Gabriel Veloza, Michael Taylor, Andrés Mora, John Gosse; Active mountain building along the eastern Colombian Subandes: A folding history from deformed terraces across the Tame anticline, Llanos Basin. GSA Bulletin 2015;; 127 (9-10): 1155–1173. doi: https://doi.org/10.1130/B31168.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Active crustal shortening and surface uplift are vividly expressed in the foothills of the Eastern Cordillera of Colombia. Quaternary alluvial-fan and terrace deposits are folded and uplifted tens to hundreds of meters above the local base level, recording deformation and incision of the landscape. We used geomorphic observations and structural analysis from a 300 km2 three-dimensional seismic-reflection survey over an actively growing anticline to investigate the relationship between finite shortening and surface uplift, and its effects on landscape evolution. A quantitative description of finite shortening of the pregrowth strata from excess-area and line-length calculations were compared with uplift and shortening estimates obtained from geomorphic strain markers dated using in situ 10Be cosmogenic nuclide depth profiles. This combined approach provides the first estimates of Quaternary surface uplift and horizontal shortening rates along the foothills of the northeastern Colombian Andes. Finite shortening for the Tame anticline was calculated using two different approaches. Excess-area shortening varies from 530 ± 36 m (2σ) at its southern end, decreasing northward to 404 ± 72 m (2σ), whereas line-length shortening is typically an order of magnitude smaller. Using the maximum horizontal shortening, our results for the Tame anticline reveal a Quaternary uplift rate of 2.8 ± 1.5 mm/yr, and a shortening rate of 2.1 ± 1.2 mm/yr (2σ), with the older terraces located at the highest elevations and recording the highest rotation from the horizontal, indicating growth by limb rotation. Based on these rates, the initiation of folding is estimated to be 0.25 +0.09/–0.05 Ma (2σ). We hypothesize that the discrepancy between shortening estimates from line-length and excess-area calculations can be reconciled by accounting for internal deformation, likely developed during the initial stages of folding, which can be represented by strain hardening, for example. The shortening rates we obtain are comparable to geodetically derived shortening rates but are slightly lower than long-term geologic shortening rates. Slower shortening rates and the presence of a youthful structure at the thrust front suggest that the orogen has been migrating eastward since the late Pleistocene, probably due to reorganization of a supercritical thrust wedge farther west in the hinterland, to attain critical taper. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.