This is an integrated analysis of the La Luna Formation in the Chuira pop-up structure, located in the Middle Magdalena Basin (MMVB). A structural trap originally mapped with 2D seismic and later with a 3D seismic volume, was interpreted using a conventional time structure maps and depth conversion methods. In 2009, the first well drilled a sequence of calcareous rocks which produce oil in stable natural flow but with a low rate. In order to understand this potential discovery, multidisciplinary studies were conducted including a detailed geology of the La Luna Formation information from outcrops, the integration of seismic attributes, log analysis, and an exhaustive reservoir research from existing samples.

1. Copyright 2008, ACGGP.
This paper was selected for presentation by an ACGGP Technical Committee following review
of information contained in an abstract submitted by the author(s).
Abstract
This is an integrated analysis of the La Luna
Formation in the Chuira pop-up structure, located in the
Middle Magdalena Basin (MMVB). A structural trap
originally mapped with 2D seismic and later with a 3D
seismic volume, was interpreted using a conventional time
structure maps and depth conversion methods. In 2009, the
first well drilled a sequence of calcareous rocks which produce
oil in stable natural flow but with a low rate. In order to
understand this potential discovery, multidisciplinary studies
were conducted including a detailed geology of the La Luna
Formation information from outcrops, the integration of
seismic attributes, log analysis, and an exhaustive reservoir
research from existing samples.
Stratigraphic studies of this Upper Cretaceous
sediments show differences on their depositional environment
regarding variations inside a carbonate platform, water
column, oxygen content and an anoxic event of long extent
and maximum depth of Coniacian age. A structural evaluation
conducted on near outcrops, defines the orientation of
fractures. These features were compared with subsurface
information including crossed dipole sonic, nuclear magnetic
resonance, and microresistivity image logs.
Geophysical studies on the seismic volume, including
AVO, Seismic inversion, and interpretations on seismic
attributes like coherence, and curvature incorporated to this
study the regional orientation and intensity of fractures and
faults patterns, all of them tied to existing logs. All
information was integrated to define well locations ranked by
the best fracture productive zones obtained from this proposed
method. This approach illustrates a methodology that will
represent an increment of production and reserves in this kind
of natural fractured reservoirs.
Introduction
The analysis of fracture reservoirs has been a
challenge around the world, moreover it is important when
reservoir quality, hydrocarbon and water properties and flow
characteristics are required or a development plan is needed to
increase the recovery factor based on the understanding of
natural fracture reservoirs. The La Luna formation of the
Middle Magdalena basin, Colombia, is a reservoir that can be
considered the future reservoir of the basin for both
unconventional and conventional resources. The current
production of the La Luna formation is restricted to a few
wells in the basin, primarily from anticline structures
discovered with low coverage seismic data and very little
knowledge of fractures patterns (Prince et al, 2010)
In this article, we present an approach of a way to understand
the La Luna formation as a natural fractured reservoir by
integrating different subsurface and surface data.
Project Location
The area of study is the Midas exploration Block,
located in the Middle Magdalena basin, in the North Central
part of Colombia, South America (figure 1). The area is close
to San Alberto, San Martin and Aguachica municipalities at
the Cesar department.
Figure 1. Geographic location of the area of study (yellow
polygon), structural limits and project location.
Geological Setting
The Middle Magdalena Basin (MMVB) is an
intermontane basin, flanked by the Central Cordillera on the
west and the eastern cordillera on the east, in the Colombian
Andes. The structural boundaries are defined in the west by
the Palestina fault, a dextral strike-slip system, and in the east
by the Bucaramanga-Santa Marta fault system, a sinistral
strike-slip system that juxtaposes the basin against the
Santander Massif (figure 1). Northwards, the sedimentary
sequence thins out and finishes against a paleohigh probably
formed by the Espiritu Santo fault system, Barrero D., et al
2007. Southwards, the basin ends at the Ibague fault system
Rolon L., 2004
The west side of the basin is a homocline dipping
eastwards, constituted by a Jurassic-Cretaceous sedimentary
An Integrated Approach to the Exploration of Fractured Reservoirs: A Challenge in
the Cretaceous Rocks of the Middle Magdalena Valley Basin, Colombia.
Acevedo R., Daza D., Prince M., Rojas. D., and Sanchez C., Petróleos del Norte S.A.- Petrolatina Energy Plc.

2. 2 ACEVEDO R., DAZA D., PRINCE M., ROJAS. D., AND SANCHEZ C.
wedge overlying the Paleozoic Precambrian rocks, which
gradually onlaps westwards. The east margin shows structural
complexity, with anticlines and synclines product of
transpressive and compressive tectonics including a west-
verging thrust belt and a group of high-to-low angle inverted
normal faults generally dipping eastwards, Rolon L., 2004.
The current sedimentary wedge was progressively eroded
by a succession of unconformities ranging in age from the
Paleocene to the Pleistocene.
From the tectonic and stratigraphic point of view, the
main characteristics of this sedimentary sequence have been
identified by many authors and can be summarized as follows
(figure 2).
The Jurassic and Lower Cretaceous (Berriasian)
volcano-sedimentary rocks were deposited in a tectonically
controlled fluvial system, starting by the accumulation of a
syn-rift megasequence which includes the Girón or Norean
Formation (Clavijo, J., 1996), and the Arcabuco-Los Santos
formations. These units are overlaid by Early Cretaceous
calcareous and siliciclastic sedimentary rocks deposited on a
marine environment at a shallow platform, which comprises
the Basal Calcareous Group.
Shallow to deep marine sedimentary deposits from
Albian through Campanian age were deposited on a platform
influenced by important world sea level changes represented
by the Simití and the La Luna formations.
A sequence of upper Cretaceous Maastrichtian to
Paleocene age deep marine siliciclastic to transitional
sediments, recorded by the Umir and the Lisama formations,
was deposited during the first phases of the compressional
deformation in a transgressive-regressive cycle environment.
The La Paz, Esmeraldas, Mugrosa, Colorado and Real
formations, from Eocene to Miocene age, were deposited in a
fluvial and lacustrian clastic environment, formed during the
progressive uplift of the Central and Eastern cordilleras. Then
the Mesa formation of late Pliocene or more probably early
Pleistocene age, was deposited unconformably on the Real
Group and older strata. The latter formed on a environment of
coalescing alluvial fans that were deposited in the Magdalena
River Valley
Multidisciplinary Studies and Methodology.
The compiled and examined information included
geological and geophysical data: initially the focus was the
seismic interpretation of the main Cretaceous, Paleogene and
Neogene events over 207 km of 2D seismic, 24 square Km of
3D seismic, both pre and post stacked time migrated. Based on
this interpretation, the exploratory Chuira well was drilled in
2009 targeting the La Luna formation (figure 3), unfortunately
by mechanical problems and the presence of “gilsonite” or
bitumen the well could not reach the total planned thickness
for the calcareous formation (Acevedo R., et al 2012).
Regardless, it has been producing at natural flow with a low
rate and up to now, it has cumulated a production of 30.000
Barrels of 22,4° API.
Figure 2. Stratigraphy of the Chuira field and outcrops at
the northeast of Middle Magdalena basin.
At the beginning, the 2D interpretation showed a four
dip closure limited by reverse faults, and later the acquisition
of 3D seismic volume allowed a better interpretation the lower
cretaceous sequence geometry.
The Chuira structure can be described now as a narrow
north to south anticline limited by high angle reverse faults,
with an average throw over 150 ft at both flanks. The dips to
these flanks are low (10° to 17°) and at the main axis the south
dip higher that the north. This anticline is part of wider fold
that can be classified as a compartmentalized “pop-up”
structure (McClay, K.R., 1992.) limited at north by a strike-
slip fault system (figures 3A and 3C).
As part of the subsurface data acquisition a full set of logs
acquired at the well, plus a corridor-stack velocity survey help
to evaluate and characterize the La Luna as a fractured
reservoir and to obtain velocity information, table 1 shows the
minimum set of tools required to perform an appropriate
formation evaluation for this kind of reservoir.
Geophysically, a set of seismic attributes analysis is
proposed in order to identify rock properties. Furthermore, the
integration of such geophysical studies generated a model of
fracture patterns for the Luna formation at the main structure
identified.

3. 3
AN INTEGRATED APPROACH TO THE EXPLORATION OF FRACTURED RESERVOIRS: A CHALLENGE IN THE CRETACEOUS ROCKS OF
THE MIDDLE MAGDALENA VALLEY BASIN, COLOMBIA.
Table 1. Electric logs minimum recommended for natural
fracture reservoir evaluation.
A. B.
C. D.
Figure 3. A) Previous 2D structure in time map, (from
Prince M. & Ordonez M 2007), B) 3D image of Chuira
structure (PSTM time slice at 1828) msec. C) Structure in
depth map top the La Luna formation. D) Seismic inline
showing Chuira Anticline.
Simultaneously to the subsurface analysis, stratigraphycal
and structural studies went carried out over a The La Luna
formation outcrop in the same geographical area. Gathering
important information and sampling for several analysis
including geochemical, biostratigraphical, and petrographical
analysis, incorporating the results in the geological model to
recognize the reservoir.
Finally a geochemical evaluation from the La Luna both at
the well and outcrops and from the oil produced was
integrated in this study.
Geological features of The La Luna Formation at
Chuira area.
Its original name comes from Garner, 1926; being
described in detail later by Hedberg and Sass, 1937, who gave
it the rank of Formation. According to these authors, in its
type locality in Venezuela, the La Luna Formation consists of
thin bedded and laminated, dense, dark gray to black colored
limestones and calcareous shales, with abundant laminated
and finely disseminated organic matter, with ellipsoidal
concretions that allow to recognize the formation in any
outcrop. Due to these so particular characteristics, the term
”La Luna Formation” is applied to a large part of limestones
of the Cenomanian - Campanian interval of the MMVB.
In Colombia, Morales et al. 1958 divided the the La Luna
Formation into three members named as Salada, Pujamana and
Galembo, which range in age from early Turonian to
Santonian.
Trying to differentiate the formation cartographically in
outcrops located northwards of the Chuira-1 well was not
viable , since the topographic and geomorphologic differences
for each of its members are not enough to follow a contact.
In two outcropping, sections (figure 4), the Aguablanca
and El Salto Creeks, detailed stratigraphic columns of the unit
were surveyed. There, the La Luna Formation is composed
mainly of black mudstones (Figure 5), marls and calcareous
shales with abundant organic matter and forams in which the
sparite concretions are frequent. The limestones exhibit fine
lamination, medium and thin beds, and in outcrops more
exposed to weathering, it is common to find a great amount of
ammonites, bivalves and fragments of fish. Thin beds of black
chert with parallel uneven incipient lamination are present in
the upper part of the unit.
The maximum thickness measured in the stratigraphic
sections reaches 383 meters; the top and base are not clearly
observed.
The upper contact of the La Luna formation with the Umir
Formation does not crop out in the area of interest, but in other
localities the authors of the present work have observed it as
transitional (Daza D. 2010, and Acevedo R., et al 2011). The
lower contact with the Simití formation is sharp, planar and
may represent a reworking surface or condensation,
sometimes marked by limestones with pelecypods fragments.
WELL SECTION ELECTRIC LOGS MNEMONICS
12.25"
Quad Combo Induction-
Neutron-Density-Sonic-
Gamma Ray
HRI-MSFL-SP-SDL-DSN-LSS-
GR
Dual Laterolog
Resistivity
DLL-MSFL-SP
Neutron-Density SDL-DSN-PEF
Spectral Gamma Ray CSNG
Cross-Dipole Sonic WSXD
Microrresistivity Image
Log
XRMI-GR
Magnetic Resonance MRIL-GR
Vertical Seismic Profile VSP-GR
CHUIRA-1
8.5"

4. 4 ACEVEDO R., DAZA D., PRINCE M., ROJAS. D., AND SANCHEZ C.
Figure 4. Location of the two main stratigraphic sections.
The yellow line is the Midas block limit.
Macrofossils biostratigraphic analysis, essentially
ammonites, was carried out at samples in the Agua Blanca and
the El Salto Creek, indicate the occurrence of the lower
Turonian and Coniacian in the sequences of the La Luna
Formation (Etayo-Serna report, in Salazar A. 2011.).
Figure 5. Outcrop of the La Luna formation at el Salto
Creek section, note the tabular beds of thin laminated
mudstones intercalated with beds of dark gray wackestones.
Microfossils biostratigraphic analysis of the stratigraphic
sections indicate that the analyzed foraminifers includes
biozones of planctonic foraminifers (ZFP) Whiteinella
archaeocretacea, Helvetoglobotruncana helvetica, Dicarinella
primitiva, Dicarinella concavata y Dicarinella asymetrica
(lower part only) of early Turonian to low early Santonian
ages.
Supported on the stratigraphy of the La Luna formation on
the outcrops plus the distribution, relative abundance,
frequency, size and mode of preservation of the foraminifers
indicate that the sedimentation took place in an marine
environment of inner shelf to outer shelf with anoxic to
disaerobic organic matter rich muddy bottoms.
At the well location, only the upper part of the La Luna
formation was drilled 533 ft (162.4m), it corresponds to the
Galembo member, which is comprised of glauconitic
limestones, greenish packstones, brown chert at the top, and
brownish marls and micrititic limestones at the bottom.
The biostratigraphic analysis of Chuira-1 ditch samples,
the upper member of The La Luna Formation suggests a
Santonian to Coniacian age. The Santonian is supported by
the microfossils Heterohelix reussi, Whiteinella inornata y
Marginotruncana sinuosa association and the Coniacian by
the presence of Dicarinella concavata, D. canaliculata,
Marginotruncana coronata, Whiteinella archaeocretacea,
Sporobulimina stainforthi, Buliminella colonensis y
Buliminella d´orbignyi, Navarrete R, Sarmiento G & Salazar
A., 2011.
According to the biostratigraphic paleoenvironment of
samples at Chuira-1 well, an anoxic event is registered by the
abundance of Bolivina explicate and open sea plactonic
foraminifera at the upper member of the La Luna Formation
(figure 6).
Figure 6. Summary of planctonic and benthonic
foraminifera main event at the Chuira well biostratigraphy.
A petrographic analysis from the ditch samples was carried
out over 11 samples, the Galembo member at the well from
petrography shows four types of rocks in different
proportions: bioclastic calcareous mudstones (78.0%)
phospatic and bioclastic wackestone/packstones (15.8%),
recrystallized mudstones (15.5%) and Mudstones (4.05%).
The depositional environment based on petrologic
interpretation shows from the foraminifera and algae observed
at the bioclastic wackestone/packstones rock type the
environment is related to anoxic conditions in an inner shelf
environment (figures 6 and 7).
Similar studies on 15 outcrop samples from the the La
Luna Formation in the Agua Blanca y El Salto outcrops for
thin sections. Results of these studies point out the
predominant occurrence of three main types of rocks
fossiliferous mudstones, biomicrite wackstones and biomicrite
packstones.
SUMMARY
DRILLED FORMATION PLANTONIC AND BENThONIC FORAMINIFERA MAIN EVENTS
INNER
MIDDLE
OUTER
Maastrichtian LOWER UMIR R. subcircumnodifer H. excavata S. bramletti S. brevispinosa
& Campanian
LOWER UMIR
A. cretacea R. rugosa P. clavata S. cretacea A. involuta S.
americana
Santonian UPPER LUNA H reussi W. inornata
UPPER LUNA M. sinuosa B. explicata S. revoluta
Coniasian UPPER LUNA Marginotruncana renzi
REWORKED UPPER LUNA P. rudita P. prolixa
Coniasian UPPER LUNA
Explosion of globotruncánidos: D. concavata, D. canaliculata,
M. coronata, S. stainforthi B. colonensis B.
d´orbignyi
UPPER LUNA Explosion of small bulimínido
UPPER LUNA W. archaeocretacea
SHELFBIOSTRATIGRAPHY
SALT
MARCH
INFLUX
Continental
CHUIRA WELL

5. 5
AN INTEGRATED APPROACH TO THE EXPLORATION OF FRACTURED RESERVOIRS: A CHALLENGE IN THE CRETACEOUS ROCKS OF
THE MIDDLE MAGDALENA VALLEY BASIN, COLOMBIA.
The main observed digenetic processes on subsurface
petrography are crystallization of calcium carbonate as
dolomite, dissolution of foraminifera shells and partially open
fractures filled with calcite and bitumen, and dissolution of
micro conduits. Under the microscope, they reach over 5% of
visual porosity of a fragment’s total volume).
From the log Analysis, the petrophysical characterization
of the upper member at the La Luna formation points out
important aspects of this potential reservoir. The logs: gamma
ray, dual laterolog, neutron-density and sonic logs, suggested
the presence of calcareous intervals exhibiting unexpected
high values of effective porosity and oil saturation (figure 8).
Figure7. Microphotography of bioclastic wackestone rock
type, note the allochemical grains (foraminifera and algae
around 40%).
Figure 8. Petrophysical profile (Scale 1/400) of the The La
Luna Fm. in Chuira-1 well. Tracks 1-4 (left to right) display
the conventional electric logs run, while tracks 5-9 display the
calculations performed.
The microresistivity image logs revealed that the Galembo
member in this area is naturally fractured, especially at the
intervals with highest hydrocarbon saturations, where they can
reach densities up to 0.75 fractures per foot (Figure 9). These
fractures are partially open, dip 50º-85º and their strikes are
preferentially NNW-SSE oriented. A Cross Dipole Sonic log
run along with image logs, shows an 8-20% of anisotropy,
which is related to intervals of high density of partial fractures.
Figure 9. Fracture density estimated from Image logs of
the Galembo Member (1/1000 Scale) in the Chuira-1 well.
The detailed intervals on the right (1/20 Scale) show the
orientation of the partial fractures identified.
The magnetic resonance log (NMR) detected mobile oil at
the flushed zone and allowed a more precise estimation of
properties such as the effective porosity (up to 16%), and the
saturation of irreducible water (20%), as seen in Figure 10.
Geochemistry lab analysis over 39 samples that came from
outcrops previously presented of The La Luna Formation
show a sequence with high hydrocarbon potential, where over
70% of the samples show content of organic matter (% TOC)
higher than 2%, with a large number of samples with values
even higher than 4%. All samples with TOC higher than 2%
were selected for Pyrolysis analysis. The Tmax from Pyrolysis
indicate that surface samples from the La Luna formation are
immature and in early generation, instead of the data from the
Chuira 1 well all are in an early mature range.
0 110 X
0.25 mm

6. 6 ACEVEDO R., DAZA D., PRINCE M., ROJAS. D., AND SANCHEZ C.
Furthermore, form Ro analysis all samples are at the
beginning of oil window generation (0.66 to 0.7%), and based
on organic petrography and Hydrogen index high percentage
of samples are Kerogen type II. Biomarkers from the oil
recover of the La Luna formation extracts confirms a shelf
marine environment with high carbonatic influx during it
formation.
Figure 10. Interpretation of the magnetic resonance log
run in the Galembo Member (1/1000 Scale), in the Chuira-1
well. The detailed intervals on the right (1/20 Scale) show the
estimation of petrophysical parameters.
Geophysical characteristics of the La Luna
Formation at Chuira area.
From geophysical viewpoint, The La Luna formation was
studied using the velocity survey from the wells, and the
PSTM seismic volume. In addition, several methods for
Seismic attributes were evaluated and its results are presented.
Horizon calibration is the link between seismic and
logging data, and it is the basis of seismic interpretation.
Synthetic seismogram is generated by statistic wavelet and
reflectivity coefficient from DT and Density curve, also
making full use of all geology and seismic data, and taking
VSP data as a reference. The well was tied to the seismic to
generate the structural time maps from seismic horizons
corresponding to the top and base the La Luna Formation
defined by the lithological, biostratigraphycal and
petrophysical work (figure 11).
The first method of Seismic attribute analysis was using
azimuthal seismic data; theory says that fracture development
can cause amplitude variation with offset and azimuth (Feng
Shen et al., 2002).
According to real condition of CMP gathers in study area,
where there is a low fold number and medium offset as is the
case of Midas Centro 3D program. The CMP gathers only
could be divided into three different azimuth gathers (0~65°,
60~120°, 120~180°) in offset range of 150 m. ~ 2800 m.,
trying to unify the energy of each azimuth gather.
Figure 11, Well Chuira-1 correlated to the poststack
seismic data
Energy uniformity is another very important factor to
verify the azimuthal seismic data processing, because the
essential of fracture prediction is just to detect the energy
variation between different azimuthal seismic data. As seen in
figure 13, the amplitude energy of each azimuth seismic data
is in the same range (-40~40). There are no empty traces
through the whole study area. The quality of azimuth seismic
data is relative good enough to do anisotropy detection.
In the fracture prediction based on 3D P-wave seismic
dataset, the most sensitive attribute has to be selected
optimally on the foundation of reliable azimuthal seismic data.
As to this project, the relative impedance was selected as
“dynamic parameter” to detect fracture development. In order
to describe and understand dynamic parameter’s variation of
different azimuthal seismic volumes directly and visually, an
anisotropy ellipse as a vector, which can presents fracture
orientation and intensity, can fitted by different values of each
azimuth in same incidence angle.
An elaboration of a 3D map of fracture orientation using
Land Ocean software, was carried out for prediction result at
the top The La Luna Formation (figure 14). The orientation of
little bars represents fracture orientation, and color represents
fracture intensity. The rose diagram is statistic result of
fracture orientation. It illustrates that there are two main
orientations developed in The La Luna Formation, NE~SW is
the primary one and the second one is NW~SE, figure 15.

7. 7
AN INTEGRATED APPROACH TO THE EXPLORATION OF FRACTURED RESERVOIRS: A CHALLENGE IN THE CRETACEOUS ROCKS OF
THE MIDDLE MAGDALENA VALLEY BASIN, COLOMBIA.
Figure 12. Geometric properties comparison with different
azimuth seismic data. A) PSTM volume, B) 0~65° azimuth
seismic data, C) 60~120° azimuth seismic data, D) 120~180°
azimuth seismic data (From Yan Li, Prince M. & Rojas D.
2012)
Figure 13. Anisotropy vector calculated by ellipse fitting,
the axis: orientation of anisotropy; the ratio of major and
minor axis: intensity of anisotropy. (From Yan Li, Prince M.
& Rojas D. 2012)
Figure 14. 3D map of fracture orientation for The La Luna
Formation
Figure 15. Fracture orientation statistical result, main ,
NE~SW
The second explored method of seismic attributes was
using the computed Coherence and Curvature volumes using
software tool at Arcis Corporation. As Chopra, S. and K.
Marfurt, 2005 describe, coherence computes a measure of
similarity between adjacent traces, and curvature attributes
measure the degree of curvature of a surface or in a volume.
These computed attributes helped to improve interpretation
and structural understanding of 3D seismic data volumes at
Chuira area. The 3D seismic coherence volume facilitates the
interpretation of discontinuities such as fractures and faults, as
seen in figures 16 and 17 at the top and base of the La Luna
formation. The main faults that are very well delineated and
easy to visualize, show compartments at the Chuira “pop-up”
structure and the orientations pattern of present faults. Black
color represents non similarity and white similarity, and then
the east part of the volume is highly affected by low
coherence.
Curvature volume makes very clear that the perspective of
interpretation depends on the wavelength which is visualized
as mention by Bergbauer et al., 2003.
Figure 16 Horizon slice from the coherence volume along
Upper the La Luna Mb. Top.

8. 8 ACEVEDO R., DAZA D., PRINCE M., ROJAS. D., AND SANCHEZ C.
Figure 17 Horizon slice from the coherence volume along
Upper the La Luna Mb. base.
At the studied area, the main anticlines are clearly
observed with the long-wavelength volume and the main
closure limits are easily outlined, figures 18 and 19. The tight
folds and intense fracturing are clear with very much detail at
the short-wave curvature. As detected in the Chuira structure
fracture intensity is frequent near to the faults and at the sides
if the main anticline, this also intense to the east of the seismic
volume, figures 18 and 19.
It was possible to delineate the fracture pattern and define
a rose diagram for the seismic interval working with
stratigraphic slices, from top to bottom of the La Luna
formation. It was developed integrating the curvature and
coherence volumes with overlays and superposing tools at the
processing center of Arcis Corporation.
Nearby the reference well, the main orientations developed
by the possible open fractures have an orientation measured as
N13°E at the drilled section of the La Luna Formation, in
general for the seismic volume the direction is NE-SW (figure
20).
If we look to the northeast, corner the orientation changes
to NW, which correlates with the presence of faults close to
the Santa Marta-Bucaramanga fault system and it agrees with
the surface geology structural trend observed (figure 4) being
this the north sealing limit of the pop up structure.
Figure 18. Horizon slices from curvatures volumes along
Upper the La Luna Mb. Top. A) the most-positive curvature
(long-wavelength), B) the most-positive curvature (short-
wavelength), C) the most-negative curvature (long-
wavelength, and D) the most-negative curvature (short-
wavelength).
Proposed well trajectories.
The relative good quality of reservoir encounter at Chuira
well, plus the lithofacies and properties defined at the area let
expect continuity of these properties along the area. The
proposed future development should be focused on penetrate
and navigate the upper member of the La Luna formation.
Formation correlation between well and outcrops illustrate
low facies changes which help to define high to horizontal
drilling paths. Although there is only one well, the excellent
relationship between the azimuthal, coherence and curvature
seismic attributes with the fracture orientation at the well let
us define well trajectories perpendicular and semi oblique to
the main trends of fractures. The authors present four initial
choices of well trajectories that have to be evaluated from
drilling engineers to make possible one of the options
presented (figure 21)

9. 9
AN INTEGRATED APPROACH TO THE EXPLORATION OF FRACTURED RESERVOIRS: A CHALLENGE IN THE CRETACEOUS ROCKS OF
THE MIDDLE MAGDALENA VALLEY BASIN, COLOMBIA.
Figure 19. Horizon slices from curvatures volumes along
Upper the La Luna Mb. Base. A) the most-positive curvature
(long-wavelength), B) the most-positive curvature (short-
wavelength), C) the most-negative curvature (long-
wavelength, and D) the most-negative curvature (short-
wavelength),
Figure 20. Horizon slice rose diagram, showing fracture
orientation for the interval known as Galembo member based
on picking lineaments on the overlaying of curvature &
coherence volumes.
Figure 21. Fracture orientation Map at the Upper member of
the La Luna formation and well trajectories.
Conclusions
The Galembo member from the La Luna formation was
characterized using different geological and geophysical
methods, the results will guide future field development.
Good correlation between fracture pattern from XRMI logs
and seismic attributes fracture analysis from two different
techniques azimuthal analysis, curvature with coherence
analysis proved the accuracy of the methods used.
Based on fracture orientation results four well trajectories
proposals for field development and exploration of new zones
at the La Luna formation members.
Geochemical studies show the La Luna formation not only
as an excellent source rock for conventional oil, but also as a
potential unconventional reservoir.
Acknowledgments.
The authors want to express our deepest gratitude to
our Company Petróleos del Norte S.A. subsidiary of
Petrolatina energy Plc for providing valuable information used
for this work. Also to different professionals involved in all
studies from Geostratos Ltda, Paleosedes EU, GEMS, ARCIS
Corporation and Land Ocean. In the same way, we want to
send special thanks to all the subsurface team for the
contributions and comments and everyday hard work.
References.
Acevedo R., et al 2011 “Formación Umir en el sector norte de
la cuenca del Valle Medio del Magdalena: Una nueva frontera
exploratoria en una cuenca madura”, XIV Congreso
Latinoamericano de Geología, XIII congreso colombiano de
Geología, Agosto 31 2011
Acevedo et al 2012. “Presencia de gilsonita y bitumen en la
cuenca del VMM. -un reto para la perforación exploratoria-” .
Memoirs XI Bolivarian Symposium of Petroleum Exploration

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