Oriente Basin Research Articles

Earning community trust in Ecuador

Land seismic crews have to adapt to working in every kind of environment around the world. In this illustrated article Gehrig Schultz and Norberto Soto describe how one PGS Onshore operation found the solution to carrying out seismic acquisition in a jungle region of Ecuador in the face of objections, local and international. At the edge of the Amazon jungle a short flight east of the cool mountain valley where the Andean capital, Quito, sits surrounded by high snow capped peaks and a smoking volcano, PGS Onshore’s Crew 360 has been busy meeting the challenge of seismic acquisition in the jungle and the special local conditions that govern such surveys. The crew is acquiring its second 3D survey in Ecuador’s oil rich Oriente Basin for state oil company, PetroProduccion, as part of a project to redevelop the mature Sacha Field. Discovery of the Sacha Field and other nearby giant fields attracted immigration to the area by poor peasants called ‘colonos’ pursuing economic opportunities and free land. The colonization, in turn, led to commercial development, including logging, mining and agriculture. In Ecuador, as in any developing nation, forested lands were cleared to support this growing population. Today, the oil boom’s economic opportunities have been replaced by increasing poverty as the ‘colonos’ can now only operate marginal cattle ranches and small struggling coffee, cocoa and oil palm plantations. The poor jungle soils only produced profitable crop yields for three or fours years, until minerals were depleted from the thin jungle soils. The worldwide collapse of coffee prices has eliminated the main source of income for many small farmers. Small groups of traditional indigenous tribes still inhabit the remote, undisturbed jungle areas, living very much in the way they have for centuries. Environmental damage during the early years of oil field development has led local farmers and indigenous groups to distrust the petroleum industry. This distrust led local stakeholders and international non-governmental organizations (NGOs) to actively challenge oil exploration activity in the area, with demands for reclamation of damaged areas and a share in the benefits from the production. The biggest challenge in executing a 3D survey in Ecuador’s Oriente region is operating a high quality seismic crew safely and efficiently in this complex and turbulent social environment. Evidence of the complex social environment is demonstrated by recent job delays and cancellations in the area. One major international seismic company finally declared force majeure on a project and closed its Ecuadorian operation after repeated protests and even temporary confinement of its field crews. Six months of standby due to constant permit problems and conflicts with NGOs on the block adjacent to Sacha, where PGS Onshore is present, caused another competitor to cease operations. Other contractors have been delayed months and reportedly have had thousands of dollars of seismic recording equipment destroyed by sabotage.

Tide-dominated estuarine facies in the Hollin and Napo (T and U) formations (Cretaceous), Sacha field, Oriente Basin, Ecuador: Reply

Tide-dominated estuarine facies in the Hollin and Napo (T and U) formations (Cretaceous), Sacha field, Oriente Basin, Ecuador: Reply

Tide-dominated estuarine facies in the Hollin and Napo ("T" and "U") formations (Cretaceous), Sacha field, Oriente Basin, Ecuador: Reply

Tide-dominated estuarine facies in the Hollin and Napo ("T" and "U") formations (Cretaceous), Sacha field, Oriente Basin, Ecuador: Reply

Stratigraphic responses to a major tectonic event in a foreland basin: the Ecuadorian Oriente Basin from Eocene to Oligocene times

The Eocene to Oligocene sediments of the Ecuadorian Oriente Basin record two kinds of second-order stratigraphic response to the tectonic evolution. Lower Eocene shows evidences of local scale syntectonic deposits. This tectonic activity can be related to right lateral convergent movements inverting pre-cretaceous extensional structures. Upper Eocene and Oligocene sediments are integrated as the expression of an isostatic rebound characterizing a basin scale syntectonic deposition. This response is evidenced by a reciprocal architecture of the depositional sequences identified in the sedimentary formations. These data have allowed us to propose a new geodynamic model for the Paleogene evolution of the Oriente Basin.

Discovery of a Jurassic Porphyry Copper Belt, Pangui Area, Southern Ecuador

ABSTRACT Grassroots exploration has led to discovery of 10 porphyry copper prospects in the previously unexplored Jurassic arc of southeastern Ecuador. The prospects are located in steep, wet, jungle-covered terrain in the Pangui area, part of the Cordillera del Cóndor. The exploration program, initially mounted in search of gold in the Oriente foreland basin, employed panned-concentrate drainage sampling. Follow-up of the resulting anomalies utilized soil sampling combined with rock-chip sampling and geologic mapping of the restricted creek outcrops. Scout and infill drilling of two of the prospects, San Carlos and Panantza, has shown hypogene mineralization averaging 0.5 to 0.7 percent Cu overlain by thin (averaging <30 m) zones of chalcocite enrichment or oxidized copper mineralization. The prospects are centered on small, composite granocliorite to monzogranite porphyry stocks that cut the Zamora batholith or, in one case, a satellite pluton. The batholith is emplaced into Jurassic volcanosedimentary formations, which concealed Triassic extensional half-grabens before being incorporated into the Subandean fold-thrust belt along the western margin of the Oriente basin. North- and northwest-striking normal faults in the hanging wall of a major north-striking fault zone controlled the locations of most of the porphyry centers. K silicate and variably overprinted intermediate argillic alteration, containing chalcopyrite as the principal sulfide mineral, characterize the central parts of most of the porphyry prospects and grade outward to pyrite-dominated propylitic halos. Overprinted sericitic alteration is generally less widely developed, although apparently shallower erosion at the Warintza and Wawame prospects resulted in preservation of extensive pyrite-rich sericitic zones. All the prospects contain appreciable (60–250 ppm) molybdenum, but gold tenors are low except at Panantza and Wawame (~0.15 and 0.2 g/t, respectively). Supergene oxidation and chalcocite enrichment zones are immature because of inhibition by the rapid erosion prevalent in the Pangui area. Supergene profiles attain their maximum development on ridge crests but are essentially absent along major creeks. Discovery of the Pangui belt, along with other recently defined porphyry copper systems in northern Perú, Indonesia, and the Philippines, underscores yet again the efficacy of drainage geochemistry as an exploration technique in tropical and subtropical arc terranes as well as the outstanding potential for additional exposed deposits in poorly explored parts of the circum-Pacific region.

Tide-Dominated Estuarine Facies in the Hollin and Napo (T"and "U") Formations (Cretaceous), Sacha Field, Oriente Basin, Ecuador"

The article by Shanmugam et al. (2000) is a welcome addition to the scant sedimentological literature on the Oriente Basin and its continuation in Colombia, the Putumayo Basin (Higgs, 1997a). Shanmugam et al. (2000) reinterpreted the Hollin and Napo T-U sands as tide-dominated estuarine deposits, rejecting a previous deltaic model. Neither model, however, accords with the stated lack of evidence for subaerial emergence. An alternative, tidal shelf interpretation is promoted here, and petroleum reservoir implications discussed. Also, although Shanmugam et al. (2000) did not report any sequence boundaries, their data suggest that angular (tectonic) sequence boundaries occur at the base of the A and B limestones, signifying possible incised valleys cutting into the U and T sands, again important for oil exploration. ### Lack of Emergence Indicators The 516 ft (157 m) of cores from seven wells examined by Shanmugam et al. (2000) show a simple facies association of shales, heterolithics, and cross-bedded sands. [N]o evidence for subaerial exposure exists (Shanmugam et al., 2000, p. 674); for example, rooting is lacking (Shanmugam et al., 2000, p. 660) and no coal beds, paleosoils, or desiccation cracks were reported. Sparse interpreted marsh deposits (<1% of one 58 ft core) (Shanmugam et al., 2000, table 2) are based on nondiagnostic interpretation criteria, that is, sandstone with intervals of concentrated carbonaceous fragments … may be interpreted as a marsh environment (Shanmugam et al., 2000, p. 660). Alternatively, such plant-flake concentrations could occur on a shelf because of tidal-current segregation of particles. An interpreted fluvial channel is based solely on cross-stratification and basal lags (Shanmugam et al., 2000, p. 656), both of which can also apply to submarine tidal bars (e.g., Stride et al., 1982, figure 5.22; Dalrymple, 1992, figure 29C). The same facies association and absence or scarcity of emergence indicators characterizes the Hollin and Napo T-U …

Abstract: Predictability of Reservoir Facies within a Sequence Stratigraphic Framework, Oriente Basin, Ecuador&amp;nbsp;

Abstract: Predictability of Reservoir Facies within a Sequence Stratigraphic Framework, Oriente Basin, Ecuador&amp;nbsp;

Abstract: Tectono-Sedimentary Evolution of the Late Cretaceous Napo Formation, Ecuadorian Oriente Basin, South America&amp;nbsp;

Abstract: Tectono-Sedimentary Evolution of the Late Cretaceous Napo Formation, Ecuadorian Oriente Basin, South America&amp;nbsp;

Sediment accumulation on top of the Andean orogenic wedge: Oligocene to late Miocene basins of the Eastern Cordillera, southern Bolivia

Research Article| September 01, 1998 Sediment accumulation on top of the Andean orogenic wedge: Oligocene to late Miocene basins of the Eastern Cordillera, southern Bolivia Brian K. Horton Brian K. Horton 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1998) 110 (9): 1174–1192. https://doi.org/10.1130/0016-7606(1998)110<1174:SAOTOT>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brian K. Horton; Sediment accumulation on top of the Andean orogenic wedge: Oligocene to late Miocene basins of the Eastern Cordillera, southern Bolivia. GSA Bulletin 1998;; 110 (9): 1174–1192. doi: https://doi.org/10.1130/0016-7606(1998)110<1174:SAOTOT>2.3.CO;2 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 A large volume of Tertiary synorogenic sediment accumulated on top of the Eastern Cordillera of southern Bolivia as the Andean orogenic wedge was shortened, thickened, and uplifted. Oligocene to upper Miocene strata were deposited in five basins that were separated by active, north-trending, fold-thrust structures of the then-frontal part of the orogenic wedge. These coarse-grained deposits recorded accumulation in the most proximal sector of the Andean foreland basin system, the wedge-top depozone.Analyses of depositional systems, sediment dispersal patterns, and clast provenance of 0.6–2.3-km-thick, Oligocene to upper Miocene wedge-top successions demonstrate that fault-propagation and fault-bend folds commonly isolated individual basins while serving as primary sediment sources. Growth strata which formed by progressive fold-limb rotation indicate thrust-fault displacement and related folding concurrent with deposition. Alluvial fans defined most basin margins, whereas braided streams or small lakes occupied basin axes. Diagnostic stratigraphic units confined to individual basins suggest that streams were rarely able to cut across growing folds to connect adjacent basins.Growth strata and crosscutting and onlapping relationships between contractional structures and wedge-top strata delineate the chronology of fold-thrust deformation in the Eastern Cordillera. Five new 40Ar/39Ar dates and previously published K-Ar dates, ranging from 30 to 8 Ma, define an Oligocene phase of west-vergent backthrusting followed by primarily east-vergent thrusting during Miocene time. Timing of displacement on two east-vergent thrusts is determined by 40Ar/39Ar ages of tuffs within adjacent growth strata sequences of the Tupiza Formation conglomerate (16.14 ± 0.06 Ma) and Oploca Formation (13.33 ± 0.15 Ma, 15.7 ± 2.4 Ma). These ages, combined with basin depositional histories, demonstrate synchronous and out-of-sequence thrust displacement during Miocene shortening.Upper-crustal contractional deformation and wedge-top deposition terminated in the Eastern Cordillera during late Miocene time as the thrust front propagated eastward into the Subandean Zone. Continued thrust-front migration produced the present-day configuration in which Eastern Cordillera wedge-top basins, originally developed above the toe of the orogenic wedge at relatively low elevations, are now >250 km west of the active thrust front and at ∼3 km elevation. The modern wedge-top depozone overlies the active frontal part of the orogenic wedge and consists of strata in thrust-bounded, Subandean Zone basins and sediment overlying blind structures beneath the westernmost Chaco Plain.In general, wedge-top deposits become highly susceptible to erosional recycling as the orogenic wedge propagates forward and the wedge surface is uplifted. Nevertheless, Eastern Cordillera wedge-top deposits have been preserved for ∼10–30 m.y. in southern Bolivia. Such long-term preservation may reflect the inability of drainage systems to remove sediment mass from this low-precipitation region of the central Andes. Retention of sediment mass within the orogenic belt may promote critical thrust-wedge conditions in which propagation of the thrust front is favored. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Abstract: Tide-Dominated Estuarine Facies in the Hollin and Napo (T"and "U") Formations (Cretaceous), Sacha Field, Oriente Basin, Ecuador"

Abstract: Tide-Dominated Estuarine Facies in the Hollin and Napo (T"and "U") Formations (Cretaceous), Sacha Field, Oriente Basin, Ecuador"

Abstract: Diachroneity of Early Cretaceous (Aptian-Albian) Reservoir Rocks in the Oriente Basin, Ecuador: Implications for Oil Exploration

Abstract: Diachroneity of Early Cretaceous (Aptian-Albian) Reservoir Rocks in the Oriente Basin, Ecuador: Implications for Oil Exploration

Abstract: Structural Style and Timing of Hydrocarbon Entrapments in the Ecuadorian Oriente Basin

Abstract: Structural Style and Timing of Hydrocarbon Entrapments in the Ecuadorian Oriente Basin

Abstract :Outcrop Description Results in Formulating Ground-truth"Input Variables for Simulation of Hollin Formation, Oriente Basin, Ecuador"

Abstract :Outcrop Description Results in Formulating Ground-truth"Input Variables for Simulation of Hollin Formation, Oriente Basin, Ecuador"

Bogi and Capiron fields, Oriente Basin, Ecuador: Similar Reservoirs but Contrasting Drive Mechanisms and Recoveries: ABSTRACT

Bogi and Capiron fields are being developed under a unit agreement with Petroecuador. These adjoining fields straddle Block 16 in the Oriente Basin and probably share a common oil water contact. Both fields are simple four-way-dip closures which produce heavy oil from Campanian sandstones of similar quality. However, the two fields are remarkably different in terms of oil production and projected recovery as a result of differing structural closures, reservoir distributions and, hence, differing drive mechanisms. The main reservoir at Bogi field is an amalgamation of two fluvial sheet sandstones thought to be low-stand deposits associated with two falls in relative sea level. The reservoir is thick (56-78 ft) and, with an observed oil column of only 38 feet, a bottom-water drive mechanism is ubiquitous. The oil is heavy (18 API) and mobility ratios unfavorable; water production is high and oil recovery from conventional drilling is expected to be 3-5%. In contrast, only the upper fluvial sheet sandstone is present in Capiron field and a reservoir thickness of 32-48 ft combined with an oil column of 99 ft ensures an edge-water drive mechanism over most of the field with concomitant initial low water production and oil recoveries of approximately 30%.more » The contrast between Bogi and Capiron fields highlights the problems and challenges in the Block 16 area. Small structural closures filled with heavy oil are abundant and an accurate seismic depth map coupled with an understanding of reservoir distribution are vital to economic success.« less

Basin Development and Tectonic History of the Llanos Basin, Eastern Cordillera, and Middle Magdalena Valley, Colombia

The Middle Magdalena Valley, Eastern Cordillera, and Llanos basin constituted a major regional sedimentary basin from the Triassic to the middle Miocene. Basin development began during the Triassic to the earliest Cretaceous with a synrift megasequence related to the separation of North and South America in the proto-Caribbean. The synrift megasequence began with deposition in a continental environment that became paralic and shallow marine in the Early Cretaceous. Basin development continued into the Cretaceous in a back-arc setting east of the Andean subduction zone. The back-arc megasequence was dominated by shallow-marine sedimentation and produced an excellent regional source rock during the Turonian-Coniacian. Marine deposition was abruptly terminated during the ear y Maastrichtian due to the final accretion of the Western Cordillera. Accretion of the Western Cordillera created the early pre-Andean foreland basin megasequence of late Maastrichtian to early Eocene age. This depositional episode consists of coal-rich alluvial plain, coastal plain, and estuarine deposits throughout the Middle Magdalena Valley, Eastern Cordillera, and eastern Llanos basin. The megasequence was terminated by middle Eocene deformation in the Magdalena Valley, which ended sediment deposition throughout Colombia. Loading effects of this deformation reestablished the basin, in which the late pre-Andean foreland basin megasequence was deposited, until the early Miocene. This megasequence also consists of alluvial plain, coastal plain, and estuarine deposits, including the primary reservoir in the Llanos Foothills--the upper Eocene Mirador Fo mation. The megasequence also includes a series of four major grossly coarsening-upward cycles in the Llanos basin; these cycles correspond to changes in sea level, sediment supply, and foreland basin loading. The mudstone in the lowermost of these cycles is the regional seal in the Llanos basin and Foothills. The middle Miocene onset of Andean deformation in the Eastern Cordillera isolated the Middle Magdalena Valley from the Llanos basin. The deformation was dominated by inversion of the basin-controlling faults; the resultant loading of the lithosphere created the accommodation space for the Andean foreland basin megasequence. A major transgression into the Llanos basin coeval with this deformation caused deposition of marine mudstones in the lower part of the megasequence. However, the majority of the Andean foreland basin megasequence consists of the Guayabo Formation, a classic molasse sequence, deposited in a high-energy, coarse-grained, bed-load-dominated fluvial system that was supplied by the developing mountains of the Eastern Cordillera.

Basement Uplifts, Basin Structuration and Fluid Dynamics, Oriente Basin, Ecuador: ABSTRACT

Basement Uplifts, Basin Structuration and Fluid Dynamics, Oriente Basin, Ecuador: ABSTRACT

Comparison of maturity based on steroid and vanadyl porphyrin parameters: A new vanadyl porphyrin maturity parameter for higher maturities

Correlations are demonstrated between steroid maturity parameters and the porphyrin maturity parameter (PMP) which is based on the ratio of specific vanadyl porphyrins C 28E (C 28E + C 32D) measured by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the C 29-sterane 20S/(20S + 20R) and tri/(tri + mono) aromatic steroid ratios, and that all three parameters appear to attain their maximum values at similar maturity levels. The triaromatic steroid side chain cracking parameter, TA I/(I + II), reaches approximately 20% of its maximum value when PMP has reached 100%. These results suggest that PMP is effective in the early to peak portion of the oil window. A new parameter, PMP-2, based on changes in the relative concentrations of two peaks in the HPLC fingerprint (vanadyl “etio” porphyrins), appears effective in assessing the maturity of source rocks beyond peak oil generation. In combination with PMP this parameter extends the effective range of vanadyl porphyrins parameters to higher maturities as demonstrated by a suite of oils from the Oriente Basin, Ecuador, South America.

The Petroleum Geology of the Sub-Andean Maranon-Ucayali Basin, Onshore Peru

The Maranon-Ucayali Basin complex covers seventy five million acres east of the Andes. It trends north to south from the Ecuadorian Border where it is synonymous with the Oriente Basin to within 200 kilometers of the Bolivian border. The stratigraphy of the basin ranges from Ordovician to recent, covering remnants of larger Lower and Upper Paleozoic and Mesozoic basins. The basin is currently the foreland trough of the overthrusting Eastern Cordillera and, in common with many other sub-Andean Basins, is a Miocene to Recent feature. Three main compressional structural events are usually visible on seismic data, a Hercynian (Carboniferous-Permian) episode in the Ucayali Basin or Triassic event in the Maranon Basin, followed by Lowermost Cretaceous uplift and erosion and strong Miocene (Quachua) compressional folding. Oil prone source rocks are recognized mainly in the Devonian, Permian, and Cretaceous, but with significant potential in the Triassic and Jurassic. Four main families of oils have been identified of which three correlate with Cretaceous and Permian source rocks and one with neither. Approximately one billion barrels of oil and five trillion cubic feet of wet gas have been discovered to date, almost exclusively reservoired in Cretaceous deltaic to shallow marine clastics. A variety ofmore » trap types have been identified for which examples will be presented. These range from basement involved and detached thrust faulted anticlines to inversion and combination drape/compression anticlines.« less

Recent and ancient fluvial deposition systems in the Amazonian foreland basin, Peru

AbstractStill active Sub-Andean foreland deformation is suggested to have syndepositionally modified the fluvial depositional environments in the Peruvian Amazonian foreland basin throughout Neogene-Quaternary time. Modern fluvial aggradation continues to proceed on a large scale (c. 120 000 km2) in two differing depositional systems. Firstly, various multistoried floodbasin deposits are derived from the meandering and anastomosing rivers within the subsiding intraforeland basins. Secondly, in the northern part of the Pastaza-Marañon basin the largest known Holocene alluvial fan-like formation (c. 60 000 km2) composed of reworked, volcaniclastic debris derived from active Ecuadorian volcanoes, has been identified.The widespread, poorly known, dissected surface alluvium (terra firme) which covers the main part of the Peruvian Amazonian foreland basin shows further evidence of long-term foreland deformation, and terraces indicate both the effects of tectonism and Pleistocene climatic oscillations. In northern Peru, the surface alluvium was deposited by a Tertiary fluvial system with palaeocurrents to the west and northwest into the Andean foreland basin. In southern Peru, the respective surficial alluvium was part of a post-Miocene fluvial system flowing northeast into the main Amazon basin. Both systems were gradually abandoned when the eastward migrating Andean foreland deformation led to the more distinctive partitioning of the intraforeland basins, and the modern drainage system was created.

Controls on the composition of fluvial sands from a tropical weathering environment: Sands of the Orinoco River drainage basin, Venezuela and Colombia

Fluvial sands in the Orinoco River drainage basin fall into three main compositional groupings: (1) sands of subarkose and arkose composition, from high-relief parts of the Guayana Shield, where crystalline rocks are exposed; (2) sands of litharenite and sub-litharenite composition from the active orogenic belt at the western and northwestern margins of the drainage basin, and in those parts of the Llanos (Andean foreland basin) proximal to the mountain belt; and (3) sands of quartz-arenite composition, widespread throughout the remainder of the basin. Multicycle sands of quartz-arenite composition are produced from platform cover on parts of the elevated shield and from uplifted foreland-basin fill in the eastern Llanos. First-cycle sands of quartz-arenite composition are produced from granitic rocks on low-relief regions of the Guayana Shield and from reworked Holocene alluvium in parts of the western Llanos distal to the orogenic terranes. Erosion in the Orinoco River drainage basin may be described in terms of transport-limited and weathering-limited denudation regimes. In active orogenic terranes and in parts of the elevated shield, transport processes can remove weathered material as rapidly as it is produced by chemical weathering. Thin soils and short soil-mineral residence time result in sands that are incompletely chemically weathered and accurately reflect source-rock composition. In the orogenic terranes, subtle variations in source-rock lithology are preserved in sand composition. In contrast, in low-relief parts of the Guayana Shield and on flat erosion surfaces of the upland shield, weathering exceeds the rate at which transport processes can remove weathered material. Thick soils accumulate, soil-mineral residence time is long, and detritus is highly altered chemically. On much of the lowland Guayana Shield, upper soil layers consist of nearly pure quartz sand that erodes to produce first-cycle fluvial sand of quartz-arenite composition. Chemically weathered orogenically derived sand enters the Orinoco River on the left bank, while feldspathic shield-derived sand enters on the right bank. This geometry is responsible for the nearly total lack of longitudinal variation in sand composition along the 1,400-km length of the Orinoco River mainstem. Except in the upper 100 km of the Orinoco River mainstem, cross-channel heterogeneity in sand composition is also modest. Nevertheless, a weighted linear least-squares modeling approach suggests that sand moves down the Orinoco River mainstem in distinct pulses, perhaps corresponding to times of accelerated erosion in headwater regions. Because rivers that head in the orogenic terranes and traverse the Llanos contribute more than 99% of the sand in the lower Orinoco River mainstem, the composition of this sand is dominated by chemically weathered sands from the Llanos. The Orinoco River—the third largest river in the world—delivers first-cycle sands of quartz-arenite composition to its delta.