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Petroleum systems of the Upper Magdalena Valley, Colombia

L.F. Sarmiento, A. Rangel*

ECOPETROL, Instituto Colombiano del Petroleo (ICP), km 7 Autopista Piedecuesta, Bucaramanga AA P.B.X. 4185, Colombia

Received 17 March 2003; received in revised form 10 November 2003; accepted 20 November 2003

Abstract

In the Upper Magdalena Valley, Colombia, four petroleum systems were identified. Two petroleum systems are located in the

Girardot sub-basin and the other two in the Neiva sub-basin. Limestones laterally changing to shales of the lower part of the Villeta

Gp, deposited during Albian and Turonian marine flooding events, constitutes the main source rocks of the oil families. These rocks

contain 1 4% TOC and type II kerogen. The littoral quartz arenites of the Caballos (Albian) and Monserrate (Maastrichtian) Fms.

are the main reservoir rocks. Seal rocks are Cretaceous and Paleocene shales. Overburden includes the Cretaceous rocks and the

Tertiary molasse deposited simultaneously with development of two opposite verging thrust systems during Cenozoic time. These

deformation events were responsible for trap creation. Except for the Villarrica area, where the source rock reached maturity during

the Paleocene, generation occurred during Miocene. Two oil families are identified, each in both sub-basins: One derived from a

clay-rich source and the second from a carbonate-rich source rock lithofacies of the lower part of Villeta Gp. Geochemical source-

rock to oil correlations are demonstrated for the three of the petroleum systems. Up-dip lateral migration distances are relatively short

and faults served as vertical migration pathways. A huge amount of oil was probably degraded at surface, as a result of Miocene

deformation and erosion.q 2004 Elsevier Ltd. All rights reserved.

Keywords:Petroleum systems; Upper Magdalena Valley; Colombia; Petroleum source rock; Oil families

1. Introduction

The Upper Magdalena Valley (UMV) is a narrow

intermontane basin located along the southern upstream

portion of the Magdalena River Valley, between the Central

and Eastern Cordilleras of the Colombian Andes. Precam-

brian to Jurassic igneous and metamorphic rocks and locally

Paleozoic sedimentary rocks crop out on the Central and

Eastern Cordilleras on both sides of the basin. The

Natagaima structural high, where Triassic and Jurassic

economic basement rocks crop out, divides the UMV into

the northern Girardot sub-basin and the southern Neiva

subbasin (Fig. 1).

The UMV contains a number of commercial accumu-

lations of oil and gas. Between 1962 and 1982 several

oil fields were discovered just north of Neiva in the

uppermost Cretaceous Monserrate Fm. Beginning in 1984

oil was discovered along the Dina-San Jacinto fault in

the Aptian-Albian Caballos Fm. By 1994 542.1 MMbbl

of recoverable oil and 91.9 BCF of gas had been

discovered in more than 30 accumulations and

287.5 MMbbl of oil had been produced. A total of 191

exploration wells and more than 300 appraisal and

development wells have been drilled in the basin. In

spite of the basinss petroliferous character, the existing

knowledge about the petroleum systems in this basin is

minimal.

Buitrago (1994) defined two petroleum systems in the

southern Neiva subbasin, both related to the same source

rock of the Villeta Gp. Ecopetrol-Icp (1994) and Cordoba

(1998) have also proposed petroleum systems schemes for

the UMV.

This paper (1) Describes the sedimentary record of the

UMV making emphasis on the sedimentary processes

controlling distribution and quality of the petroleum system

elements. (2) Discusses a geochemical approach for source

rock-oil correlation. (3) Identifies and describes the

petroleum systems of the UMV applying concepts and

terminology discussed byMagoon (1992) and Magoon andDow (1994).

0264-8172/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.marpetgeo.2003.11.019

Marine and Petroleum Geology 21 (2004) 373391www.elsevier.com/locate/marpetgeo

* Corresponding author. Tel.: 57-674-01-49; fax: 57-644-5444.

E-mail address:[email protected] (A. Rangel).
http://www.elsevier.com/locate/marpetgeohttp://www.elsevier.com/locate/marpetgeo


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2. History of the Cretaceous and Cenozoic sedimentaryand deformation processes as controlling mechanisms

for petroleum elements distribution and quality

Triassic and Jurassic sedimentation and volcanism occur

in a narrow rift, which define economic basement rock

(Mojica & Bayer, 1987; Mojica & Dorado, 1987).

The Aptian to Paleocene sedimentary rocks constitute a

major dominantly marine megasequence (Fig. 2). This

megasequence includes a lower transgressive part that

records the onset of continental deposition (Yav and

Alpujarra Fms.), and transition to marine environments

(El Ocal and Caballos fms.). A medial portion recorded a

dominantly muddy to limy oxygen deficient marine shelfdeposition (Villeta Gp.), and an upper regressive and

progradational part recorded by the change from marine to

continental environments (Monserrate and Guaduala Fms.,

Etayo-Serna 1994).

The Aptian Paleocene megasequence was formed by five

major sequences (Fig. 2). The source rocks and the main

reservoir rocks are part of this megasequence.

Sequence 1. Aptian-Lower? to Middle? Albian (Fig. 2).

After a period of non-deposition represented by the Jurassic-

Aptian unconformity, Aptian sedimentation started with

gravels and red muds of the Yav Fm deposited as alluvial

fans coming from the elevated borders of rift grabens. Then

the quartzitic sands of the Alpujarra Fm. (Reservoir rock)were deposited by a fluvial system on a valley along the

central part of the basin (Etayo Serna, 1994; Florez &

Carrillo, 1994). Dark gray mudstones of the overlying El

Ocal Fm. (Source rock) recorded a southward marine

transgression, which reached its maximum flooding surface

(MFS) at the beginning of Albian time during deposition of

organic rich muds (average TOC from 0.5 to 2%) containing

mixed marine and continental organic matter.

Sequence 2.Middle Albian-Cenomanian(Fig. 2). A local

unconformity exists at the bottom of the Caballos Fm.

(Etayo-Serna, 1994, Fig. 2) and was probably caused by a

slight tectonic uplift of the area. This sequence begins with

quartzitic sandstone of the Caballos Fm. (Reservoir rock)

interpreted as fluvial influenced littoral, beach or deltaic

deposits (Etayo-Serna, 1994; Florez & Carrillo, 1994).

Succeeding black shale and limestone facies of the Villeta

Gp. (seal rock) record marine deposition on a shelf. Thisrecorded a new marine flooding event, which was more

intense toward the north. Maximum water depth was deeper

than normal weather wave base. Maximum flooding of the

shelf was reached during deposition of planktonic derived

fine-grained limestones and organic rich muds (TOC 14%)

of the Tetuan Limestone (Source rock). The upper part of

the sequence, transitional from Tetuan Limestone to

Bambuca Shale, records deposition in shallower water and

an increase of coastal influence with increasing detrital clay

input from the land and bioclastic lime beds deposited

during storms.Sequence 3. Cenomanian-late Coniacian (Fig. 2). This

sequence is represented in its lower part by the transitionfrom gray shale (proximal shelf facies of the Bambuca

Shale) to black fine-grained pelagic limestone (distal shelf

facies of the La Luna Limestone) as a deepening upward

trend. The La Luna Limestone (source rock) records water

deepening during the end of Cenomanian and beginning of

Turonian. During deposition of La Luna Limestone (Iateral

equivalent of La Luna Fm.), the Cretaceous maximum

marine flooding event (MFS) occurred over an area

extending from Venezuela to Peru (Fabre, 1985). This

planktonic derived micritic limestone unit contains abun-

dant marine organic matter (Type II kerogen, average TOC 1

to 4%,Fig. 3a and b). After the maximum flooding event

there was a water shallowing and a decrease of distancefrom the coastline, evident from a relative increase of fine

grained detrital sediment during deposition of the upper-

most part of the Villeta Gp. From middle Turonian to late

Coniacian this gradual progradation and shallowing upward

is interpreted to be related to a relative tectono-eustatic sea

level fall (Villamil, 1994).

Sequence 4.late Coniacian-earliest Campanian(Fig. 2).

During the late Coniacian to Santonian the transition from

the uppermost Villeta Gp., deposited in an inner shelf, to the

lower chert unit of the Olini Gp, deposited on a deeper

middle shelf (Jaramillo & Yepez, 1994; Ramirez &

Ramirez, 1994), points to a deepening of the basin and a

relative tectono-eustatic level rise (cf Etayo-Serna, 1994).Maximum flooding was reached during deposition of

Fig. 1. Location map of the Upper Magdalena Valley (UMV), Colombia.

L.F. Sarmiento, A. Rangel / Marine and Petroleum Geology 21 (2004) 373391374


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Fig. 2. Generalized stratigraphic column of the UMV (modified afterGeotec, 1994and Etayo-Serna, 1994).

L.F. Sarmiento, A. Rangel / Marine and Petroleum Geology 21 (2004) 373391 375


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the lower chert unit of the Olini Gp. During Santonian to

earliest Campanian, regression and progradation was

recorded by the middle shale unit of the Olini Gp,

Sequence 5.Earliest Campanian-Maastrichtian(Fig. 2).

The lower sequence boundary occurs at the base of the

middle shale unit of the Olini Gp. and the shallow water El

Cobre sandstones described by Barrio and Coffield (1992)

and Villamil (1994). The upper part of the sequence

represented by the Monserrate and La Tabla fms. (Reservoir

rock) records depositional environments shallowing from

marine shelf to beach, and a progradation of the coast line as

indicated by a coarsening upward deposits from terrigenous

silt to quartz sand in the upper part of the sequence.The Guaduala Fm. mudstones (seal rock) record sea

withdrawal, and then paralic and fluvial sedimentation.

(Diaz Poveda, 1994a,b; Ramirez & Ramirez, 1994;

Etayo-Serna, 1994; Rodriguez & Castro, l994).

The Cenozoic sedimentary record forms the third

megasequence, its understanding is important because it

recorded (1) sedimentary and tectonic burial responsible

for petroleum generation and (2) deformation events

responsible for petroleum traps. Its lower boundary is a

regional unconformity, which represents an Early Eocene

hiatus (Fig. 2), probably caused by an uplift of the basinal

area. During this time in some places (e.g. Natagaima

high, Fig. 1) Cretaceous and Paleocene sediments were

totally or partially eroded (cf. Anderson, 1972; Caicedo &Roncancio, 1994). Erosion of uplifted fault blocks

Fig. 3. (a). Lithofacies distribution of Tetuan Limestone and the La Luna Limestone (lower part of Villeta Gp.). (b). TOC l, HI and Tmax of the lower part of

Villeta Gp. (includes Tetuan Limestone, Bambuca Shale and Luna Limestone).



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Table 1

Petroleum systems elements and oil reserves in the Upper Magdalena Valley

Petroleum systemand sub-basin

Main source rock Oil family Main reservoir rock Seal Trap Oil field Reservoir rock Oil in(MM

Villeta-Tertiary Lower Villeta Oil Family I Honda- Tertiary Estructural Toqui-Toqui Doima 29Girardot Sub-basin Monserrate Claystones Pul Monserrate 29

Pacande Caballos 6Totare Honda 29

Subtotal 93Villeta-Caballos Lower Villeta Oil Family II Caballos Villeta Fm. Estructural Chenche Monserrate 5Girardot Sub-basin Ortega-Tetuan Caballos 155

Toy Caballos 38Toldado Caballos 50Quimbaya Caballos 17Pauta Caballos 9Ro Saldana Caballos 27Purificacion Monserrate 57Montanuelo Monserrate 28Olini Caballos 5Monserrate Monserrate 1Revancha Monserrate 14Venganza Monserrate 51

Subtotal 458Villeta-Caballos Lower Villeta Oil Family I Caballos Villeta Fm. Estructural Balcon-Colombia Caballos 44Neiva Sub-basin Hatonuevo-Loma Larga Caballos 6

Tenay Caballos 20San Francisco Caballos 675Andaluca Honda 80

Subtotal 825Villeta-Monserrate Lower Villeta Oil Family II Monserrate Guaduala Fm. Estructural Dina Terciario Honda 182Neiva Sub-basin (4) Dina Cretacico Monserrate 125

Cebu Monserrate 126Pijao Monserrate 18Tello Monserrate 230Palogrande Monserrate 214

Brisas Monserrate 28Gigante Monserrate 175Los Mangos-Yaguara Caballos 100La Canada Monserrate 12La Jagua Honda 2Santa Clara Caballos 11Santa Clara Sur Caballos 5Rio Ceibas Honda 42

Subtotal 1272Total 2649


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and anticline crests occurred during structural deformation

starting at the end of the Cretaceous and increasing during

Early Eocene.

The Cenozoic megasequence of the UMV was deposited

in dominantly continental environments. Two thrust and fold

systems are present in the UMV (Butler & Schamel, 1988):

the Central Cordillera system, with eastward tectonic

transport active during Eocene to Oligocene time, and the

Eastern Cordillera system, with westward tectonic transport

active during the Miocene (Butler & Schamel, 1988). During

the Eocene to Oligocene the basin has been interpreted as a

foreland with sediments derived from uplifted and deformed

thrust fault blocks of the paleo-Central Cordillera (Cooper

et al., 1995). However, there is evidence of local deformation

and uplift in the area of the Eastern Cordillera since the

Paleogene (Gomez, 2001; Sarmiento-Rojas, 2001). Duringthe Miocene, sediments were derived from uplifted thrust

blocks of both the Central and Eastern Cordilleras, and basin

became intermontane (Sarmiento-Rojas, 2001).

3. Petroleum systems of the Upper Magdalena Valley

3.1. Petroleum source rock

The Villeta Gp. contains two main source rock strati-

graphic intervals responsible for most of the commercial oil

found in the UMV (Fig. 2,Tables 1 and 2). A minor amount

of oil could have been generated by the EI Ocal Fm. andpossibly from some Lower Cretaceous stratigraphic inter-

vals in the northeastern part of the basin (evident in the

Suarez1 and Villarrica1 wells).

Strata deposited during maximum marine flooding events

of the lower part of Villeta Gp. have oil-generating potential.

The lower part of Villeta Gp. is 305518 m (10001700 ft

gross thickness) thick. The main source rock intervals within

the lower Villeta Gp. are the Tetuan Limestone and the La

Luna Limestone, which are, respectively, 135 and 100 m

thick. They contain on average of 1 4% TOC, and its

hydrogen index varies between 100 and 650 mg HC/gC. with

most values exceding 200 mg. HC/gC. They contain mixed

kerogen with a predominance of algal marine organic matter

over terrigenous organic matter. Maximum TOC and

hydrogen index values occur in the distal calcareous pelagic

rocks of the western part of the area (Figs. 3b and 4).

Lithofacies maps of Tetuan Limestone and La Luna

Limestone (Fig. 3a) aresimilar,they show a predominance of

pelagic micritic limestone (western distal shelf facies) and

some detrital clays recording sediment input from an

eastward detrital source area (eastern proximal shelf facies).

Near to the San Francisco1 well there is a clayrich lobeprobably pro-deltaic in origin and in the northwest part of the

Girardot sub-basin a smaller clay or sand rich lobe recording

turbiditie deposition. TOC and hydrogen index maps

(Fig. 3b) of the lower part of the Villeta Gp. resemble

paleogeography indicated on the lithofacies maps (Fig. 3a):

Toward the northwest planktonic derived carbonates are

present with abundant organic matter, TOC values (between

1 and 4%). Hydrogen index values increases in this direction

reflecting that the distal pelagic part of the basin is

characterized by oxygen deficient condition at the sea floor

(distal shelf facies, cf. Sarmiento Rojas, 1989). Eastward

there is a decrease of organic matterrichness, hydrogen index

and planktonic carbonate and a relative increase of claydetritus input suggesting: proximity to a littoral zone

shallowing water and more oxygen at the sea bottom

probably due to bottom and surface water mixing produced

by storms (proximal shelf facies; cf. Etayo-Serna, 1994;

Sarmiento-Rojas, l989). In conclusion, strata deposited

during maximum flooding events within the lower part of

Table 2

Average source rock data for Lower Villeta Formation (Tetuan and The La Luna Limestone)

Petroleum system Main source rock Studied well Average TOC

(%)

Average Tmax

(8C)

Average HI

(mgHC/gC)

Average S1

(mgHC/gR)

Average S2

(mgHC/gR)

Villeta-Tertiary Lower Villeta Rosita-1 2.2 429 374 0.73 8.4

Girardot Sub-basin Pacande-1 3.1 424 531 0.99 16.6

Suarez-1 1.8 465 100 1.10 2.0

Villeta-Caballos Lower Villeta Chenche-1 1.6 426 495 0.62 8.1

Girardot Sub-basin Toy-1 3.1 416 652 1.42 20.4

Toldado-1 3.0 421 547 1.56 16.5

Pauto-1 3.2 418 538 1.54 17.4

Olini-1 3.7 419 563 1.27 20.6

Boreal-1 3.2 424 441 0.67 13.9

Tolima-1 2.9 420 566 0.60 16.0

Coyaima-1 3.5 427 581 1.72 20.2

Villeta-Caballos Lower Villeta Balcon-1 2.5 428 437 0.85 10.9

Neiva Sub-basin San Francisco-1 2.1 425 419 0.77 8.7

Villeta-Monserrate Lower Villeta Los Mangos-1 2.1 425 434 0.51 9.0

Neiva Sub-basin Nilo-1 2.0 432 436 0.49 8.6

Santa Clara Sur-1 1.9 430 392 0.28 7.4Tarqui-1 1.2 432 200 0.15 2.5



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Villeta Gp. (Tetuan Limestone and La Luna Limestone) are

rich in marine organic matter (kerogen type II.). In the UMV,

organic rich strata tend to be deposited close to maximum

flooding events (e.g.Curiale, 1992; Pasley et al., 1991).

3.2. Crude oil geochemistry

Seventy oil samples from different reservoirs of the basin

(Table 3), were characterized. The API gravity of these oils

ranges from 19.1 to 36.48, the heavier of them showing

partial removal ofn-alkanes and isoprenoids but absence or

scarce presence of 25-norhopane (norhopane/hopane ratio

,0.05), indicative of moderate biodegradation, generallytoward the western part of the basin.

The sulfur varies from 0.31 to 2.81%. The sulfur content

is commonly used to support oiloil correlation. According

toPeters and Moldowan (1993), many high sulfur kerogen

and oils originate from clay poor marine rocks (e.g.

carbonates) deposited under highly reducing conditions.

Conversely in marine siliclastics rock, metals may out-

compete organic matter for reduced sulfur, leading to low-

sulfur kerogen and oil.

Certain biomarker ratios of UMV oils are characteristic of

VSM oils(Table 3). For example, hopanes predominate over

tricyclic terpanes, signifying according to Ourisson et al.

(1982) an important bacterial input on the kerogen. Thegammacerane/C30 hopane ratios reach values up to 0.25,

indicating a marine-saline depositional environment (Mol-

dowanet al., 1985). Oleanane, an Upper Cretaceous/Tertiary

indicator derived from upper plants (Peters & Moldowan,

1993; Ten Haven et al., 1988), is present in very low

concentration (oleanane/hopane ratio less than 0.02). The

C34/C35hopane ratios are higher than 0.5 and the diasterane/

regular sterane ratios lower than 1.25. Both biomarker ratio

values indicate a depositional environment with carbonate

input/and anoxic conditions (Peters and Moldowan, 1991;

Mello et al., 1988; Peters and Moldowan, 1993).

3.2.1. Oil familiesAn approach to the grouping of oils was achieved by

statistical methods of hierarchical cluster analysis (HCA),

crossplots (Fig. 5), GC fingerprint, hopane and sterane

fragmentograms (Fig. 6). The HCA dendogram was

constructed using source related biomarker ratio averages

converted to indexes (Table 2). According to the cluster

analyses (Fig. 5a), two oil families were identified. The oil

Family I constituted by the oils from the Andaluca-1,

Balcon-1, Providencia-1, Hato Nuevo-1, Pacande-1, Totare-

7 and San Francisco 114 wells; and the oil Family II

composed by the oils from the Chenche-1, Purificacion-2,

Dina K-15, La Jagua-1, Toldado-1, Santa Clara-1, Dina T-

12, Los Mangos-1, La Canada-6 and Gigante-1 wells andthe oil seep La Canada.Fig. 5bshows the oil family II as

Fig. 4. Pyrolysis geochemical well profiles Coyaima-1 well modified from Ecopetrol-Icp (2000).



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Table 3

Bulk geochemical parameters and some biomarker ratios and indexes for oils

Well/seepage Interval Formation 8API

gravity

Sulphur

(%)

Pristane/

Phytane

Diasterane/

Esterane

Tm/Tm

Ts

C28Bisnor-

hopane/

C28Bis C30Hopane

Oleanane/

Olea C30Hopane

Gamma-

cerane/Gam

C30Hopane

C35/C35 C34

Hopanes

C23Tricyclic/

C23Tri C30Hopane

Andaluca-34 1806-1829 Doima 33 0.38 2.4 1.12 0.64 0.03 0.01 0.10 0.36 0.21

Balcon-1 9631-9716 Caballos 33.7 0.34 1.7 1.25 0.01 0.03 0.01 0.09 0.36 0.25

Hato Nuevo-1 6204-6691 Caballos 36.4 0.31 2.19 1.06 0.42 0.02 0.01 0.09 0.33 0.17

Pacande-1 5930-6490 Villeta 27.9 0.86 1.17 1.18 0.52 0.08 0.01 0.08 0.40 0.29

Providencia-1 5380-5700 Villeta-

Caballos

28 0.42 1.66 0.91 0.44 0.02 0.02 0.10 0.30 0.28

San Francisco

114

1835-1845 Tetuan 26.6 0.51 1.63 0.81 0.49 0.03 0.01 0.09 0.34 0.23

Totare-7 Honda 21.9 0.83 1.59 1.21 0.49 0.07 0.02 0.07 0.38 0.32

Chenche-1 4557-4678 Doima 32.1 0.75 1.16 0.41 0.55 0.15 0.03 0.14 0.43 0.29

Dina K-15 6000-6405 Monserrate 21.3 1.07 1.17 0.6 0.58 0.05 0.02 0.11 0.43 0.31

Dina T-12 1890-2568 Honda 20.3 1.8 1.2 0.55 0.62 0.07 0.03 0.12 0.44 0.42

Gigante-1 13140-13306 Monserrate 23.5 1.32 1.36 nd 0.59 0.09 0.04 0.12 0.46 0.46

La Canada-6 Caballos 21 2.22 1.1 0.59 0.66 0.13 0.02 0.11 0.45 0.46

La Jagua-1 5262-5320 Honda 21.2 0.82 1.7 0.68 0.58 0.03 0.01 0.11 0.41 0.30

Los Mangos-1 2500-3000 Caballos 21 1.89 1.1 0.45 0.65 0.09 0.02 0.11 0.46 0.40

Man Bloque

Colombia

Oil seep Caballos nd 2.55 Biode. nd 0.57 0.15 0.06 0.06 0.49 0.48

Man Hda El

Darien

Oil seep nd nd 2.51 Biode. nd 0.59 0.08 0.02 0.05 0.45 0.57

Man La Canada Oil seep Bas-Villeta nd 1.57 Biode. 0.72 0.49 0.07 0.01 0.20 0.39 0.25

Man San

Francisco

Oil seep Villeta Ir. nd 0.98 Biode. nd 0.52 0.03 0.01 0.09 0.40 0.29

Purificacion-2 Guadalupe 34.2 0.63 1.25 0.36 0.57 0.15 0.03 0.15 0.40 0.34

Santa Clara-1 2714-2747 Caballos 19.1 1.43 1.5 0.68 0.55 0.04 0.03 0.14 0.32 0.28

Toldado-1 5360-5789 Caballos 17.4 2.81 1.39 0.74 0.68 0.11 0.01 0.07 0.45 0.32 nd: no data


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derived from a source rock deposited in more marine-anoxic

conditions than the oil Family I.

Oil Family Iis characterized by a higher pristane/phytane

ratio (1.17 to 2.4), lower content of sulfur (0.310.83%),

relatively more abundant diasteranes (diasteranes/steranes

ratio from 0.81 to 1.25), presence of diahopane and low

C29/C30 hopane ratio. This oil family originated from a

source rock largely argillaceous with some minor carbonate,

deposited in a dysoxic marine environment. Crude oils of

this family are located on areas where source rock intervalsof the Villeta Gp. are clay-rich (Figs. 3 and 7).

Oil Family IIhas a rather lower pristane/phytane ratio

(less than 1.7), higher content of sulfur (0.63 2.81%),

relatively lower diasteranes/steranes ratio (0.41 0.74),

higher steranes/hopane ratios and more amounts of

gammacerane and bisnorhopane than oil Family I. These

features suggest an origin from a more calcareous source

rock than oil Family I, deposited in anoxic marine

environment.

3.2.2. Source rock to oil correlation

The terpane and sterane data (Tables 3 and 4andFig. 5c)

indicate a good correlation among the two oil Families andsome Tetuan unit extracts. The similarities are associated to

the lithological character of the source rock, the type of

kerogen and the interpreted depositional environment. A

good match is not observed between the data from La Luna

unit bitumens and the identified oil families (Fig. 5c).

Regarding the maturity deduced from sterane isomeriza-

tion (Fig. 5d), the bitumens from La Luna and Tetuan rock

units have not reached the peak of oil generation (Fig. 5d).

However, it is important to point out that five samples from

the Tetuan unit show the same maturity level as the oils

indicating good correlation in terms of maturity rank. Theoils in general appear to be moderately mature, indicating a

possible correlation with early mature source rock.

Tetuan unit extracts from the Rosita-1 and Balcon-1

wells correlate with oil family I (Fig. 5c), and show the same

maturity level of these oils (Fig. 5d). Tetuan unit extract

from the Nilo-1 well correlates with oil family II (Fig. 5c)

and shows a maturity level close to that of the oils ( Fig. 5d)

3.3. Pods of active source rock and petroleum systems

Source rock maturity measurements are on samples

recovered from wells drilled on structural highs and

outcrops, where the Villeta Gp is dominantly immature(pyrolysis Tmax Iess than 435 8C). Mature source rock is

Fig. 5. Crude oil geochemistry. (a) Cluster analysis for oil families based on biomarker indicators of depositional environment, (b) Oil oil correlation based onindicators of depositional environment. (c) Oil-source rock correlation based on indicators of depositional environment. (d) Oil to source rock correlation based

on maturity parameters.



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only indicated in a few wells (e.g. Apicala-1, Suarez1, and

Villarrica1) located in the northeastern and eastern part of

the basin toward the Eastern Cordillera. Although in most of

the UMV the source rock intervals are predominantly

immature Tmax data indicate mature samples in local

depocenters or below thrust sheets mainly in the lowermost

part of the Villeta Gp. (Fig. 4). These data and maturity

modeling using the BASINMOD software suggest that theUMV oil source rocks reached maturity by Sediment and/or

tectonic burial.

3.4. Burial due to normal sediment accumulation

This mechanism was responsible for organic maturation

in depocenters where sediment thickness reached a

maximum prior to any tectonic burial. We identified the

following pods of active source rock in this category (Figs. 7

and 8):

(1)Villarrica active source rock pod. (Fig. 7). Located in

the most northeastern part of the study area in the present

day Eastern Cordillera near the Villarrica1 well, mainly eastof the Magdalena thrust fault. The northern part of this area

was a significant Cretaceous depocenter. Subsidence in this

part of the basin was driven by Early Cretaceous rifting

(Sarmiento-Rojas, 2001). The highest measured maturity

levels on the northern part (468 506 8C Tmax values in the

Villarrica-1 well), and lowest porosity values measured on

Lower Cretaceous sandstones, are evidence of a more

intense organic and inorganic diagenesis here compared to

other parts of the basin. The burial history chart for theSuarez-1 well (Fig. 9a) shows that in this kitchen, source

rocks reached the oil window during the Paleocene, and that

a significant thickness of overburden rock

(.3048 m 10.000 ft) has been eroded since the Miocene

as indicated by mature rocks very close to the surface.

According to lithofacies distribution maps of the lower

part of Villeta Gp. (Fig. 3a) the active source rock is clay-

rich in the northern part of this pod. Oils from the Totare,

Pul, Toqui-toqui and Pacande oil fields present biomarker

characteristics of oils derived from siliclastic source rock,

indicating that these Family I oils were probably derived

from this clay-rich northern part of the Villarrica pod.

Tetuan unit extracts from the Rosita-1 well geochemicallycorrelate to the oil family I and has the same maturity

Fig. 6. Gas chromatograms (GC), m=z191 and m=z217 mass chromatograms from oils representatives of Family I and Family II.



11/19

Fig. 7. Petroleum systems map of the UMV.



12/19

level as the oils. However, the Tetuan unit in this well is

early mature and could not have generated an important

volume of oil. Oils of the Family I probably originated

from a similar but more mature facies eastward in the

Villarrica pod.

Lithofacies maps also show carbonate-rich source rock in

the southern part of this pod. Oils from the near

Purificacion-2, Chenche-1 and Toldado-1 wells correlatewith carbonate-rich source-rock as indicated by biomarker

analyses, (oil Family II). These oils probably were derived

from the southern carbonate-rich part of the Villarrica pod.

(2) Neiva syncline active source rock pod (Fig. 7).

This pod is located in the Tertiary depocenter where

Miocene sediments reach their maximum thickness.

These Miocene sediments were deposited when the

basin acquired an intermontane character. Tmax pyrolysisdata from the Libano-1, Nilo-1, Tarqui-1 and Altamira-1

wells near this area indicate intervals of early mature

source rock in the lower part of the Villeta Gp. ( Fig. 7).

Oil generation modeling (Fig. 9d) indicate that the lower

part of Villeta Gp. reached the top of the main oil

window at 3505 m (11,500 ft) depth during the beginning

of the Miocene, and the top of the late oil window at

3962 m (13,000 ft) depth, during the Middle Miocene.

The bottom of the late oil window was reached at

4572 m (15,000 ft) depth at the end of Miocene.

Lithofacies distribution maps (Fig. 3a) show a dom-

inantly carbonate source rock in the southern part of this

pod. Geographic proximity of the Gigante, Los Mangos,Yaguara and La Canada oil fields to this pod, and the

existence in these fields of oils derived from a

dominantly calcareous source rock, as indicated by

biomarker studies (oil family II) suggest that these oils

were generated from the Neiva syncline pod. Tetuan unit

extracts from the Nilo-1 well geochemically correlate to

the oil family II and show maturity level close to that of

the oils (Fig. 5c and d).

3.5. Paleo-normal sedimentation burial and burial due to

Tectonic stacking of thrust sheets

Volumetrically most of the oil discovered in the UMVis derived from carbonate rich source rocks (oil Family II,

Table 1), which are mainly distributed in the western part

of the basin (Fig. 3a). Maturity data in this western area

indicates that normal sediment accumulation burial was

not enough to generate oil. In order to explain the

significant volumes of oil derived from carbonate rich

source rocks in this area, we propose that generation

probably occurred below thrust sheets in the western part

of the basin (Fig. 4). Burial due to tectonic thrust sheet

stacking has been demonstrated in the Coyaima area.

There, rock samples from the hanging wall of thrust faults

(Cucuana back thrust, samples collected in Tetuan,

Toldado and Coyaima wells) are immature, whereasoutcrop samples (collected along Coyaima-Ataco road)T

able

4

Biomarkerindexesforextracts

Well

Formation

Pristane/

Phytane

Diasterane/

Sterane

C27Sterane/

C27

C29

Sterane

C23Tricyclic/

C23Tri

C24

Tetracyclic

Tm/Tm

Ts

C28Bisnorho-

pa

ne/C28Bis

C30Hopane

Oleanane/

Olea

C30

Hopane

Gammacerane/

Gam

C30

Hopane

C35/C35

C34

Hopanes

C23Tricyclic/

C23Tri

C30

Hopane

C29S/S

R

C29

aa/aa

bb

Mangos-1

Tetuan

1.2

5

0.3

4

0.9

3

0.9

0

0.6

7

0.33

0.0

1

0.1

2

0.4

8

0.2

8

0.1

5

0.1

6

Nilo-1

Tetuan

1.2

7

0.6

4

0.7

7

0.9

1

0.5

7

0.01

0.0

1

0.1

0

0.4

1

0.3

4

0.3

2

0.2

3

Rosita

-1

Tetuan

1.4

0

1.2

5

0.6

8

0.7

2

0.3

3

0.02

0.0

2

0.0

4

0.3

2

0.2

2

0.4

2

0.3

5

Tolim

a-1

Tetuan

1.0

4

0.3

3

0.9

1

0.7

9

0.8

9

0.16

0.0

1

0.0

9

0.5

3

0.1

7

0.1

2

0.2

0

Balcon-1

Tetuan

1.7

2

1.3

1

0.7

2

0.6

0

0.5

1

0.02

0.0

1

0.0

8

0.3

7

0.1

4

0.3

5

0.3

0

Borea

l-1

Tetuan

1.0

8

0.3

7

0.9

0

0.7

8

0.6

6

0.24

0.0

1

0.0

9

0.4

6

0.1

8

0.1

4

0.1

9

Camb

ulos-1

Tetuan

1.5

1

1.5

9

0.6

8

0.8

5

0.4

3

0.01

0.0

1

0.0

6

0.3

8

0.2

9

0.4

1

0.3

5

Coyai

ma-1

Tetuan

0.9

7

1.3

8

0.7

3

0.8

4

0.5

3

0.06

0.0

1

0.0

7

0.4

4

0.3

3

0.4

4

0.3

2

Chanc

he-1

Tet-Bamb

1.6

9

0.4

0

0.8

1

0.6

1

0.5

3

0.12

0.0

3

0.0

9

0.3

3

0.1

3

0.2

3

0.2

2

Tarqu

i-1

Tet-Bamb

2.4

9

0.7

1

0.6

6

0.8

6

0.6

4

0.05

0.0

2

0.0

8

0.4

7

0.3

6

0.4

2

0.3

5

Mirav

alle-1

Bambuca

1.5

1

0.3

8

0.9

2

0.7

3

0.8

4

0.06

0.0

1

0.1

2

0.5

0

0.2

4

0.1

5

0.1

8

Balcon-1

LaLuna

1.3

0

0.1

8

0.9

4

0.8

6

0.6

9

0.31

0.0

5

0.0

7

0.5

4

0.3

3

0.1

2

0.1

8

Balcon-1

LaLuna

0.8

1

0.5

9

0.7

7

0.8

0

0.5

8

0.01

0.0

1

0.0

8

0.4

2

0.2

1

0.3

0

0.2

1

Coyai

ma-1

LaLuna

0.8

2

0.4

5

0.8

0

0.8

6

0.7

1

0.23

0.0

1

0.1

1

0.5

2

0.2

7

0.2

4

0.2

0

Tarqu

i-1

LaLuna

1.3

1

1.9

6

0.7

0

0.5

1

0.6

4

0.01

0.0

3

0.0

7

0.2

9

0.1

5

0.4

0

0.3

4



13/19

from the footwall of the same thrust faults are mature.

Vergara (1994) also reported mature footwall outcrop

samples from this area. The presence of mature source rock

at surface (Fig. 4) indicates erosion of important thicknesses

of overburden, probably as a result of local uplift and

exhumation on the crest of growing structures. Taking intoaccount that most wells have not penetrated the footwall

block of thrust faults, there are few samples available to

demonstrate pods of active source rock in the most of the

UMV. However, biomarker data from source rock extracts

mainly from the lowermost part of the Villeta Gp. (i.e.

Rosita-1, Coyaima-1, Ilona-1, Balcon-1, Libano-1, Nilo-1,

Tarqui-1 and Alltamira-1 wells) show the same maturitylevel of correlatable oils (Fig. 5) demonstrating at least local

Fig. 8. Schematic structural cross-sections of the UMV Petroleum systems at their critical moment. The structural interpretation from seismic lines has been

taken fromEcopetrol et al. (1998).



14/19

generation of hydrocarbons. Based on these local data and on

structural seismic interpretationand maturity modeling using

the fault option of BASlNMOD, we predict the existence of

pods of mature source rock where source rock reached

maturity due to thrust sheet stacking in the following places(Figs. 6 and 7).

(3) Coyaima active source rock pod(Figs. 7 and 8). This

effective source rock pod is located in the footwall block of

the Cucuana thrust fault, near Coyaima, where the analysis

of outcrop samples indicated mature source rock. A source

rock extract from the lowermost part of the Villeta Gp.below the thrust sheets shows the same maturity level as

Fig. 9. Burial history charts of the petroleum systems of the UMV. (a) Villeta-Honda(!) petroleum system associated with the Villarrica kitchen, (b) Villeta-

Caballos(!) and Villeta-Monserrate (!) petroleum systems associated with the Neiva syncline kitchen, (c) Villeta-Caballos (.) petroleum system associated with

the Coyaima kitchen, (d) Villeta-Caballos (!) petroleum system associated with the San Francisco kitchen and Villeta-Monserrate (!) petroleum system

associated with the Chusma kitchen.



15/19

the oils as indicated by biomarker data (Fig. 5d). Maturity

and oil generation modeling of a representative section of

this area (Fig. 9b), with a structural repetition of all

Cretaceous and Tertiary stratigraphic units up to Potrerillo

Fm. indicates that the lower part of Villeta Gp. reached the

top of the oil window at 2926 m (9600 ft) depth, during the

Miocene. Lithofacies distribution maps (Fig. 3a) indicate

relatively calcareous source rocks in the pod that may havegenerated some oil.

(4) San Francisco active source rock pod(Figs. 7 and 8).

Source rock lithofacies distribution maps (Fig. 3a) in the San

Francisco areashow a predominanceof shale. Tmax pyrolysis

data from thelowermost part of Villeta Gp below thrust sheets

in this area (Ilona-1 andBalcon-1 wells)indicate local pods of

early mature sourcerock. An extract from a rock sample from

the Balcon-1 well below a thrust sheet shows the samematuritylevel as geochemically correlated family I oilsin this

area. Oils from the Andaluca, Balcon, Hatonuevo, La Jagua

and San Francisco oil fields as well as San Francisco oil seep

have been classified as oil Family I, derived from a shale,

indicating the existence of a petroleum system related to the

San Francisco pod (Table 1 and Fig. 7). The present-day

source rockdepth as estimated fromseismiclines is shallower

than the calculated top of the oil-generative window,

suggesting that generation occurred in this area below an

overburden rock thickness that latter was eroded. Also, thrust

sheets of the San Francisco and Chusma thrust faults may

have contributed to source rock maturity.

3.6. Reservoir rock

Most of the discovered oil of the UMV is reservoired in

the Caballos Fm., which is the main reservoir rock unit

(Table 1, Fig. 2). The best quality reservoir rock occurs

within the upper part of the formation. Reservoir rock is

dominantly quartz arenite containing more than 95% quartz.

The porosity distribution is normal with an average greater

than 12% (1025%), Except for some sandstone bodies

where dissolution of unstable minerals contributes to a high

percentage of the total porosity, the dominant porosity of the

Caballos Fm. is primary intergranular (Alba Gladys Mesa,

personal communication). Permeability values range from100 mD to 4 Darcies (Houseknecht, 1991).

The second most important reservoir rock unit by volume

of oil in place in the UMV is the Monserrate Fm. ( Fig. 2). It

is the main reservoir rock of the oil generated in the San

Francisco, Neiva syncline and Villarrica (Pul oil field)

active source rock pods. The reservoir rock is quartz arenite

containing more than 96% quartz, dominantly monocrystal-

line. Porosity values range from 13 to 28%. Primary

porosity predominates. Permeability values vary from

10 mD to almost 8 Darcies (Houseknecht, 1991).

Reservoir rocks of the Totare and Toqui-toqui oil fields

containing oils generated from the Villarrica active source

rock pod, are the Honda Fm. and the Doima Fm.respectively. These formations and the Chicoral Fm. are

volumetrically less important reservoir rocks (Fig. 2). These

reservoir rocks are lithic feldspathic sandstones (2434%

quartz, 14 28% feldspar and 38 62% lithic fragments),

with porosity values from 4 to 20%. Those rocks show

secondary porosity, primary porosity and micro-porosity.

The presence of unstable minerals makes these rocks

susceptible to formation damage (Houseknecht, 1991).

3.7. Seal rock

Volumetrically, shales and fine-grained limestones of the

Villeta Gp. are the most important seal rocks for the oil

accumulated within CaballosFm. Mudstones of the Guaduala

Fm.are seal rocks foroils accumulated in theMonserrate Fm.

Other minor important seal rocks are mudstones of theHonda

Fm. and other Tertiary rock units (Fig. 2).Seal rocks of the Villeta Gp., Guaduala Fm. and Tertiary

rock units, in some places have been truncated during

erosion events genetically related to the Lower Eocene and

Miocene unconformities. In addition, the seal capacity of

these rocks has been reduced by faulting, resulting in localbut no regional seals over all the UMV.

3.8. Overburden rock

Overburden rock includes all Cretaceous and Tertiary

stratigraphic units overlying the lower part of the Villeta Gp

(Fig. 2) and thrust sheets locally. Overburden rock thickness

are shown in the burial history charts (Fig. 9c)

3.9. Petroleum traps

Almost all traps are structural or have a strong structural

component Thebiggest oilfield, SanFrancisco,is an anticline;

other oil fields are trapped by faulted anticlines, faults and/or

unconformities. Oil fields with the Honda Gp. as a reservoir

have a stratigraphic component due to the lenticular character

of the reservoir rock. Except for the La Canada field, all oil

fields are full to spill point (Buitrago, 1994).

Structural traps formed by deformation associated with

the development of the fold and thrust belts of the east-

verging Central Cordillera thrust system during Paleogeneand the west-verging Eastern Cordillera thrust system

during several events occurred during Cenozoic time,

although the most intensive deformation seems to have

been in the Miocene. It is possible that Paleogene structures

were been rejuvenated during the Miocene. Traps that store

oils derived from the Neiva sub-basin were formed since

Paleogene or mainly during Miocene depending on their

relation to the Central Cordillera thrust system or to the

Eastern Cordillera thrust system respectively (Butler &

Schamel, 1988).

Traps that store oils generated from the Villarrica active

source rock pod (Totare and Toqui-toqui oil fields), were

formed during the Miocene, as indicated by the presence ofMiocene reservoir and seal rocks (Honda Gp.). If the oil



16/19

generation and migration peak occurred during Paleocene,

as indicated by the maturity modeling results (Fig. 9a),

such oils would have been trapped in structures existing

during the Paleocene and the existing reservoir rock at that

time probably was Monserrate Fm. (e.g. Pul oil field;

Table 1). Later during the Miocene deformation event,

these oils would have re-migrated from their original traps

to the present day traps and the new reservoir rocks were in

the Tertiary units. This hypothesis needs to be tested with

better data from the above mentioned oil fields and from

the oil source rocks of the Eastern Cordillera. However,

this hypothesis is necessary to explain the existence of

these oil fields, otherwise the timing condition would not

be satisfied.

3.10. Petroleum systems and migration pathways

We propose four petroleum systems in the UMV:

1. Villeta (Tetuan-La Luna)-Tertiary (!) petroleum system

in the Girardot sub-basin. Family I oils were derived

from clay-rich source rocks from the Villarrica pod as

suggested by geochemical correlation between extracts

from the Rosita-1 well from this pod and oil family I oils.

2. Villeta (Tetuan-La Luna)-Caballos () petroleum system

in the Girardot sub-basin. Family II oils were possible

derived from carbonate rich source rock from the

Villarrica and Coyaima pods.

3. Villeta (Tetuan-La Luna)-Caballos (!) petroleum systemin the Neiva sub-basin. Family I oils were derived from

clay-rich source rocks from the Neiva syncline and San

Francisco pods, as suggested by geochemical correlation

between oils and source rock extracts from Balcon-1

well.

4. Villeta (Tetuan-La Luna)-Monserrate (!) petroleum

system in the Neiva sub-basin. Family II oils probably

were derived from carbonate-rich source rocks from the

Neiva syncline and San Francisco pods as suggested by

geochemical correlation between oils and source rock

extracts from the Nilo-1 well.

Because there are lateral changes in source rocklithofacies (clay-rich to carbonate-rich) within a single

active source rock pod, different oil families were generated

within the same pod.

Comparison between lithofacies distribution of the lower

part of Villeta Gp., geochemical signature of source rock

extracts, oil family distribution and geochemical signature,

allows a correlation between oils and pods of mature source

rocks for each petroleum system. According to these results

the certainty levels can be recognized as known (!), except

for the petroleum system Villeta (Tetuan-La Luna)-

Caballos which level of certainty can be defined as

hypothetical ().

The stratigraphic extent of the petroleum systems(Figs. 2, 8 and 9) includes from the Caballos Fm. up to

the top of Pleistocene rocks, as overburden rock responsible

for maturity of the source rock (Fig. 2). If at least locally

older rock units (i.e. Saldana Fm.) are included in the thrust

sheets responsible for sub-thrust oil generation, these

units and the Yav Fm. should also be included in

the stratigraphic extent of the petroleum systems. In the

Villarrica area the petroleum system also includes Lower

Cretaceous shales older than the Caballos Fm. The pyrolysisdata from this region demonstrate that some stratigraphic

intervals within these rocks are at least locally active

source rocks.

Figs. 7 and 8 show the petroleum systems geographic

extent and the pod of active oil source rock of each system.

The map also shows lateral migration pathways, which in

general are short, not greater than 40 km. Within heavily

faulted areas, such as the thrust belts of the UMV, faultssuch as thrusts ramps or strike slip faults, may behave as

vertical oil migration channels inhibiting lateral migration

on long distances (Demaison & Huizinga, 1994). Lateral

up dip migration pathways tends to be normal to structures.

Oils reservoired in Monserrate Fm. or in Tertiary

formations, migrated up from the Villeta Gp. Oils

reservoired in Tertiary rocks migrated following faults on

areas where Guaduala Fm. seal was not eroded. Oils

reservoired in the Caballos Fm., probably migrated from

Villeta Gp. shales in the footwall thrust fault block toward

the Caballos Fm. sandstones in the hanging wall (Figs. 7

and 8). Oil generated in the Neiva syncline laterally

migrated outward from the active source rock pod, thenupward through thrust fault ramps toward traps of the two

thrusts systems of the area (Fig. 8). Oils accumulated in the

Totare and Toqui-toqui oil fields, generated in the

Villarrica kitchen possibly migrated to Paleocene traps

and latter during the Miocene deformation event remi-

grated to their present day traps.

The relatively low gas/oil ratio of the producing fields,

suggests that oil expulsion and migration occurred as soon

as source rock reached the critical oil saturation to expel

without any delay or inhibition.

3.11. Events chart

Petroleum systems events charts (Fig. 10) show elements

and processes responsible for oil field formation, which

occurred during the Cretaceous and Tertiary. Trap for-

mation occurred before or during hydrocarbon generation

satisfying the timing condition. For the Villarrica kitchen

we assume an initial filling of traps during the Paleocene

and remigration to present day traps during Miocene.

Tertiary, largely Miocene to recent deformation and

erosion events have drastically affected the UMV in such

a way that probably a huge amount of hydrocarbons has

been degraded at surface, especially on these areas where

Cretaceous rocks crop out. As an example on the Yaguara

field structure, Monserrate Fm. sandstone at surface issaturated with tar providing evidence of the previous



17/19

existence of an oil accumulation which was destroyed by

erosion (Buitrago, 1994).

4. Conclusions

This study identified four petroleum systems. The main

source rock intervals are the lower Villeta Gp. Tetuan

Limestone and the La Luna Limestone which are,

respectively, 135 and 100 m. thick, their TOC values

range from 1 to 4%, dominantly II type marine kerogen.

The main reservoir rocks are the Caballos Fm. (Albian) and

Monserrate Fm. (Maastrichtian) quartz arenites. The main

seal rocks are the Villeta Gp. (Cretaceous) shales and the

Guaduala Fm. (Paleocene) mudstones. Overburden rock

includes all the Cretaceous and Tertiary sedimentary rocks

overlying the source rock and where burial was due to thrust

sheet stacking also includes the Yav Fm. (Aptian), Saldana

Fm. (Jurassic), or older rock units included in the thrustsheets. Traps are structural, generally faulted, and were

formed during Eocene to Miocene deformation events.

Crude oils samples are classified in two families: (1) Oil

family I derived from clay-rich shales deposited in dysoxic

environments, (2) Oil family II derived from dominantly

calcareous rocks deposited in dominantly anoxic environ-

ments. Lithofacies distribution of the Villeta Gp., oilfamilies distribution and oils-source rock correlation allows

to define their certainty level as known expect for the

petroleum system two which should be defined as

hypothetical. Lateral up dip migration distances are short

and faults could serve as vertical migration channels. Except

for the northeast part of the basin where the critical moment

occurred during the Paleogene, the critical moment of

petroleum generation, expulsion and migration occurred

during the Miocene as soon as source rock reached critical

oil saturation to expulsion. The temporal extent of

petroleum systems is Albian to Recent. Probably huge

volumes of hydrocarbon have been degraded at surface as a

result of deformation and erosion events that occurredduring the Tertiary largely in the Miocene.

Fig. 10. Events chart of the UMV petroleum systems.



18/19

Acknowledgements

Special thanks to the Geologist Blanca Nubia Giraldo for

her contribution to the analytical work. L.F: Sarmiento and

A Rangel would like to thank to Ecopetrol for permission to

publish this work. We are grateful to Dr L. Maggon and

reviewers for helpful suggestions and constructive review.

References

Anderson, T. A. (1972). Paleogene nonmarine Gualanday Group. Neiva

Basin, Colombia and regional development of the Colombian Andes.

Geological Society of America. Bulletin, 83, 24232438.

Barrio, C., & Coffield, D. (1992). Late Cretaceous stratigraphy of the Upper

Magdalena Basin in the Payande-Chaparral segment (western Girardot

Sub-Basin), Colombia. Journal of South America Earth Sciences,5(2),123139.

Buitrago, J. (1994). Petroleum systems of the Neiva area. Upper Magdalena

Valley, Colombia. In L. B. Magoon, & W. G. Dow (Eds.), The

Petroleum System. From Source to Trap (Vol. 60) (pp. 483 497).

American Association of Petroleum Geologist Memoir.

Butler, K., & Schamel, S. (1988). Structure along the eastern margin of the

Central Cordillera, Upper Magdalena Valley, Colombia. Journal of

South America Earth Sciences, 1, 109120.

Caicedo, J. C., & Roncancio, J. H. (1994). El Grupo Gualanday como

ejemplo de acumulacion sintectonicaen el ValleSuperior del Magdalena

durante el Paleogeno. Estudios geologicos del Valle Superior del

Magdalena. In F. En Etayo(Ed.), Estudios geologicos delValle Superior

del Magdalena, Universidad Nacional de Colombia, Facultad de

Ciencias, Departamento de Geociencias(pp. 19, Chapter X.

Cooper, M. A., Addison, F. T., Alvarez, R., Coral, M., Graham, R. H.,Hayward, A. B., Howe, S., Martnez, J., Naar, J., Penas, R., Pulham,

A. J., & Taborda, A. (1995). Basin development and tectonic history of

the Llanos Basin, Eastern Cordillera and Middle Magdalena Valley,

Colombia. American Association of Petroleum Geologist Bulletin,

79(10), 14211443.

Cordoba, F (1998). Sistemas Petrolferos da sub-provincia de Neiva Vale

Superior do Rio Magdalena, Colombia. Tesis de Maestra, Universidad

Federal de Rio de Janeiro,Ro de Janeiro, pp.230.

Curiale, J. A. (1992). Application of organic geochemistry to sequence

stratigraphic analysis; four corners platform area, New Mexico, USA.

In C. B. Eckard (Ed.),Advances in organic geochemistry 1991, part 1.

Advances in applications in energy and the natural environment(Vol.

19) (pp. 5375). Organic Geochemistry.

Demaison, G., & Huizinga, B. J. (1994). Genetic classification of petroleum

systems using three factors: charge, migration and entrapment. In L. B.Magoon, & W. G. Dow (Eds.), The petroleum systemFrom source to

trap, American Association of Petroleum Geologist Memoir, 60 (pp.

7389).

Daz Poveda, L. (1994a). Distribucion de las facies siliciclasticas

correspondientes a la Formacion Arenisca Tierna y Equivalentes en el

Valle Superior del Magdalena. Estudios geologicos del Valle Superior

del Magdalena. In F. Etayo (Ed.), Estudios geologicos del Valle

Superior del Magdalena (pp. 5Universidad Nacional de Colombia,

Facultad de Ciencias, Departamento de Geociencias, Chapter IV.

Daz Poveda,L. (1994b).Reconstruccion dela CuencadelValleSuperiordel

Magdalena, durante el Paleogeno. Estudios geologicos del Valle

Superior del Magdalena. In F. Etayo (Ed.), Estudios geologicos del

Valle Superior del Magdalena. Universidad Nacional de Colombia,

Facultadde Ciencias,Departamentode Geociencias (pp.13,ChapterXI.

Ecopetrol,, Geotec,, & Robertson, (1998) (6 Vols). Seismic Atlas ofColombia. Seismic expression of structural styles in the basins of

Colombia.

Ecopetrol-Icp (1994). Evaluacion geoqumica Cuenca Valle Superior del

Magdalena, Informe Interno, Empresa Colombiana de Petroleos,

Instituto Colombiano del Petroleo, Piedecuesta.Internal Report, 195pp.

Ecopetrol-Icp. (2000). Evaluacion integrada del tren de produccion de laCuenca del VSM, Tolima. Informe interno. Empresa Colombiana de

Petroleos, Instituto Colombiano del Petroleo, Piedecuesta. Internal

report, 253 pp.

Etayo-Serna, F. (1994). Eplogo: a modo de historia geologica del Cretacico

del Valle Superior del Magdalena. Estudios geologicos del Valle

Superior del Magdalena. Universidad Nacional de Colombia, Facultad

de Ciencias, Departamento de Geociencias. In F. Etayo (Ed.), (pp. 6,

Chapter XX.

Fabre, A. (1985). Dinamica de la sedimentacion Cretacica en la region

Sierra Nevada del Cocuy (Cordillera Oriental de Colombia) Proyecto

Cretacico Contribuciones. Publicacion Especial Ingeominas, Chapter

16, XIX, 20pp.

Florez, J., & Carrillo, G. (1994). La sucesion litologica basal del

Cretacico del Valle Superior del Magdalena. Estudios geologicos del

Valle Superior del Magdalena. In F. Etayo (Ed.), Estudios geologicos

del Valle Superior del Magdalena. Universidad Nacional de

Colombia, Facultad de Ciencias, Departamento de Geociencias

(pp. 26, Chapter II.

Geotec (1994). Stratigraphy and tectonic study of the Upper and Middle

Magdalena Basins, Columbia. Report for Maxus, Bogota, 55pp.

Gomez, E (2001). Tectonic controls on the late cretaceous to cenozoic

sedimentary fill of the Middle Magdalena Valley Basin, Eastern

Cordillera and Llanos Basin, Colombia. PhD Dissertation, 5 Appen-

dixes, Cornell University, New York. 618pp.

Houseknecht, D. W. (1991). Stratigraphic variation in petrology, diagenesis

and reservoir potential of Cretaceous and Tertiary sandstones, Upper

Magdalena Valley, Colombia.Internal Report Prepared for Hocol, 100.

Jaramillo, C., & Yepez, O. (1994). Palinoestratigrafa del Grupo Olini

(Coniaciano-Campaniano), Valle Superior del Magdalena, Colombia.

Estudios geologicos del Valle Superior del Magdalena. In F. Etayo

(Ed.), Estudios geologicos del Valle Superior del Magdalena.

Universidad Nacional de Colombia, Facultad de Ciencias, Departa-

mento de Geociencias (pp. 18, Chapter XVII.

Magoon, L. B. (1992). The petroleum systemStatus of research and

methods. US Geological Survey Bulletin 2007, 111pp.

Magoon, L. B., & Dow, W. G. (1994). The petroleum system. In L. B.

Magoon,& W. G.Dow (Eds.),Thepetroleum system. Fromsource totrap

(pp. 3 24).American Association of Petroleum Geologis Memoirt 60.

Mello, M. R., et al. (1988). Geochemical and biological marker assessment

of depositional environment using Brazilian offshore oils. Marine and

Petroleum Geology, 5, 205223.

Mojica, J., & Bayer, K (l987). Caractersticas esenciales del Valle Superior

del Magdalena, una cuenca petrolfera Cretacica interandina de

Colombia. Memoria 3er Simposio. Cretacico de America Latina,

Tucuman, Argentina, Proyecto lnternational Correlation Program,

242, pp. 11l6.Mojica, J., & Dorado, J. (1987). El Jurasico anterior a los movimientos

interrmalmicos en los Andes Colombianos. Bioestratigrafia de los

Sistemas Regionales del Jurasico y Cretacico de America del Sur.

Mendoza, 49 110.

Moldowan, J. M., Seifert, W. K., & Gallegos, E. J. (1985). Relationship

between petroleum composition and the depositional environment of

petroleum source rock. American Association of Petroleum Geologist

Bulletin, 69, 12551268.

Ourisson, G., Albrecht, P., & Rohmer, M. (1982). predictive microbial

biochemistry, from molecular fossil to procaryotic membranes. Trends

in Biochemical Sciences, 7, 236239.

Pasley, H. A., Gregory, W. A., & Hart, G. F. (1991). Organic matter

variations in transgressive and regressive shales.Organic geochemistry,

17, 483509.

Peters, K., & Moldowan, J. M. (1993). The Biomarker Guide: InterpretingMolecular Fossils in Petroleum and Ancient Sediments. New Jersey:

Prentice Hall, 363pp.



19/19

Ramrez Vargas, H., & Ramrez Criollo, N. L. (1994). Estratigrafia y origen

de loscarbonatos delCretaacico Superiordel Magdalena,Departamento

del Huila, Colombia. In F. Etayo (Ed.), Estudios geologicos del Valle

Superior del Magdalena. Universidad Nacional de Colombia, Facultadde Ciencias, Departamento de Geociencias(pp. 15, Chapter V.

Rodrguez, E., & Castro, P. E. (1994). El Maastrichtiano de la region

Honda-Guaduas, lmite N del Valle Superior del Magdalena: Registro

sedimentario de un delta dominado por ros trenzados. Estudios

geologicos del Valle Superior del Magdalena. In F. Etayo (Ed.),

Estudios geologicos del Valle Superior del Magdalena. Universidad

Nacional de Colombia, Facultad de Ciencias, Departamento de

Geociencias (pp. 20, Chapter III.

Sarmiento Rojas, L. F (1989). Stratigraphy of the Cordillera Oriental

west of Bogota Colombia. MSc thesis, University South Carolina,

102pp.

SarmientoRojas, L. F (2001).Mesozoicrifting and Cenozoic basin inversion

history of the Eastern Cordillera, Colombian Andes. Inferences from

tectonic models. PhD thesis, Vrije Universiteit, Amsterdam, 296pp.

Seifert, W. K., & Moldowan, J. M. (1978). Applications of steranes,

terpanes and monoaromatics to the maturation, migration and source of

crude oils. Geochimica et Cosmochimica Acta, 42, 7795.

Ten Haven, H. L., de Leeuw, J. W., & Sinning Damste, J. S. (1988).Application of biological markers in the recognition of paleohypersaline

environments. In A. J. Fleet, K. Kelts, & R. Talbot (Eds.), Lacustrine

petroleum source rocks, Geological Society Special Publication No. 40

(pp. 123130).

Vergara, L. E (1994). Stratigraphic, micropaleontologic and organic

geochemical relations in theCretaceous of theUpper Magdalena Valley,

Colombia. Giessener Geologische Schriften. #50. Giessen, 179pp.

Villamil, T. (1994). Relative sealevel, chronology and a new sequence

stratigraphy model for distal offshore facies. Albian to Santonian,

Colombia. In J. A. Pindell, & C. D. Drake (Eds.), MesozoicCenozoic

stratigraphy and tectonic evolution of the Caribbean region/northern

South America: Implications for eustasy from exposed sections of a

Cretaceous-Eocene passive margin setting(pp. 45Geological Society of

America. Bulletin, Paper C-8.


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