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EAPG/AAPG Special Conference on Chalk
- Conference date: 07 Sep 1994 - 09 Sep 1994
- Location: Copenhagen, Denmark
- ISBN: 978-94-6282-130-9
- Published: 09 September 1994
36 results
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Self-sea chalk deposits - A global perspective
By D. E. HattinIn 1822, d'Omalius d'Halloy proposed the formal name "Cretaceous" for northwest European
strata previously known as the chalk formation. Had rock of this age first been studied in either the
Southem or Western Hemisphere another name would undoubtedly have been established because chalky
facies neither dominate the Cretaceous System nor are restricted to it.
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Sequence biostratigraphy of European chalks
Authors H. W. Bailey, L. T. Gallagher and F. J. GregoryStratigraphic studies of Late Cretaceous sequences in northwest Europe frequently fail to
identify subtIe changes in both lithofacies and biofacies due to the apparent monotonous nature
of chalk sediments. This results in the non-recognition of many major factors affecting the
stratigraphic succession, well geohistories and the mis-interpretation of regional sequentiaI
history.
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The role of stylolites in the formation of reservoir potential of the upper Cretaceous deposits of North Precaucasian
More LessCarbonate formation of the Upper Cretaceous (Turonian -
Maastrichtian, in some places Danian) made up of the chalk,
chalk-like limestones and micrices limestones formed in the
diagenesis is widely spread in North Precaucasian.
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Improved chalk reservoir characterization
Authors I. E. I. Øxnevad, L. Bonnell and J-E. NordtvedtA key exercise for planning aspects associated with production of petroleum reservoirs is
modelling and simulation. The adequacy of such simulations depends on good reservoir
characterisations, i.e. good estimates of geological, petrophysical and multiphase flow
properties of reservoir rocks and the reservoir structure as a whole.
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Correlation of laboratory petrophysical measurements to chalk lithofacies and reservoir quality in the Greater Ekofisk Area
Authors J. J. Howard, B. J. Crabtree, D. E. Langley, W. T. Siemers and C. D. CaldwellThe application of results from new petrophysical techniques combined with standard
laboratory petrophysical results, such as porosity and permeability, provides the necessary
information to reveal the origin of differences in reservoir quality between various chalk
lithofacies and to provide additional means to discriminate among them.
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An integrated biostratigraphical approach to the monitoring of horizontal wells through chalk
Authors L. T. Gallagher and H. W. BaileyBiostratigraphical studies of the Late Cretaceous Chalks in North
West European onshore sections have traditionally concentrated
on inception and extinction events and the age dating of
individual outcrop localities.
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A study of the geological and flow characteristics of Gouge-filled fractures and stylolites in a North Sea chalk
Authors H. E. Farrell, D. P. Tobola and B. A. BaldwinCore descriptions of Shetland Group chalks from naturally fractured reservoirs in
the Greater Ekofisk area of the Central Graben, North Sea indicate that the
reservoirs contain a number of discontinuities.
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Correlation structure of porosity and permeability in on- and offshore chalk
By P. FrykmanFor carrying out stochastic modelling of reservoir sequences, information on the
correlation structure of the properties modelled is needed. The correlation structure
is usually quantified with variograms describing the correlation ranges in different
directions.
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Mechanics of fracturing and faulting in the Austin chalk - Evidence for natural hydrofracturing from the First Shot field, Texas
Authors K. P. Corbett, J. D. Edman and E. M. Hundley-GoffAll economic production from the Austin Chalk depends on natural fractures to
provide a well connected permeability network and allow effective drainage of
the surrounding low-permeability reservoir rock.
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Influence of in situ stress on permeability of naturally fractured chalk reservoirs
By L. W. TeufelFractures are present in almost all chalk reservoirs, but it is only
when these fractures from an interconnectrd network that their affect on
fluid flow becomes important. Fractures not only enhance the overall
permeability of many reservoirs, they create significant permeability anisotropy.
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Niobrara chalk production, Silo Field, Denver Basin, Wyoming, USA - A wrench-fault fractured reservoir
Authors R. J. Weimer, S. A. Sonnenberg, J-M. Coates and D. ThornSilo field, discovered in 1980 and located in the northem part of the Denver basin,
Wyoming (Figure 1), produces from the fractured Niobrara Formation (Upper Cretaceous) at
depths ranging from 7,600 to 8,500 ft (2,318 to 2,593 m). Cumulative production from 40
vertical wells at Silo is in excess of 1.3 million BO.
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3D Seismic fractured reservoir characterization, Silo Field, Wyoming
By T. L. DavisSilo field, Wyoming, was the original site of research by the Reservoir Characterization Project
(RCP) at Colorado School of Mines into the application of multicomponent 3-D seismic surveys to
characterize the fractured chalk reservoir. These surveys, the first of their kind, resulted in the
accurate prediction of the dominant open fracture direction and the location of enhanced fracture
permeability zones in the reservoir. Results of the multicomponent 3-D seismic program at Silo field
led to horizontal drilling in the field which has confirmed the seismic characterization (Figure 1).
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Direct detection of fracture swarms in chalk reservoirs
More LessIt is now possible to identify fracture swarms in chalk reservoirs, by using surface seismic
data, in particular by utilizing the properties of shear-waves travelling in anisotropic
rocks.
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Modelling the seismic response of highly porous chalk
Authors A. Uldall and M. R. ØdumIn the late 1980'ies it was discovered on seismic data and
synthetic seismograms that the seismic phase of the Top Chalk
reflection response changed from the crestal gas zone to the waterbearing
flanks.
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3D Reservoir modelling of the flank areas of the Ekofisk Field
Authors G. Skotte and A. FritsenThe Ekofisk field has been producing from high porosity, low permeability, fractured chalk for
more than twenty years. About 180 MSm³ of oil has been produced, and current forecasts
estimate more than 150 MSm³ of remaining recoverable oil within the field.
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Reservoir characterization and management studies of the Tor Field, Norway
Authors H. Hermansen, D. B. Neff, H. Wedege and D. J. Ebbs jr.The Tor Field was discovered in late 1970. First production commenced in June, 1978 with 5 wells drilled from
a fixed 18 slot platform (Figure 1). After additional development drilling, peak oil production of 100,000 BOPD
was achieved in 1980, but has since declined to the current rate of 6,000 BOPD.
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Reservoir compaction and surface subsidence during hydrocarbon production from the chalk
Authors M. Jones, E. Mathiesen and C. MagnusProduction of hydrocarbon fluids from the Ekofisk and Valhall oil fields has resulted in substantial
subsidence of the sea floor immediately above the reservoirs which has been caused by compaction of
the weak chalks that constitute the reservoir rock (Figure 1).
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The Austin Chalk of Brookeland Field (East Texas, USA) - Importance of an integrated interdisciplinary approach in exploiting a classic fractured reservoir
Authors D. J. Hooks and S. S. HubbardThe Upper Cretaceous Austin Chalk produces along the Gulf of Mexico coast, United
States, from secondary porosity and permeability created through fracturing. Several large fields,
including Giddings (222 MMBO, 76 BCF) and Pearsall (104 MMBO, 15 BCF) were developed
utilizing mostly vertical wells.
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Mechanical properties of chalk in laboratory and field scale
By A. KrogsbøllIn many geological and engineering problems we need to transform information from one scale to
another. It is often data collected from cores (laboratory scale) which are used to evaluate various
problems in field scale or geological scale.
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On chalk fabrics and their influence on deformation behaviour
Authors N. M. Kageson-Loe, R. N. Mortimore, M. E. Jones and S. WillisThe deformation of high porosity chalks has become a major factor in understanding their performance as
hydrocarbon reservoirs. Chalks with porosities in excess of 30% readily undergo large volumetric strains when
subject to fluid production and pore pressure depletion in many cases passing through a phase transition from
elastic to ductile compaction behaviour with commensurate large increases in compressibility.
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Imaging immiscible two phase flow in low permeability chalk - Emphasis on recovery mechanisms and scaling
Authors A. Graue and B. G. ViksundA nuclear tracer imaging technique, ref. 1,2, is used to study in-situ local saturation developments
in spontaneous imbibition and waterflood experiments in chalk. Due to lack of reservoir material
outcrop chalk from the Dania outcrop near Älborg, Denmark, has been used.
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The East Hod Chalks - A new play or played out?
Authors R. D‘Angelo, M. Brandal, K. Rorvik, N. Gravdal, A. Alasker and S. CampbellEast Hod Field is one of two small oil accumulations located in Block 2/11, in the Central Trough
of the Norwegian North Sea. Although exploratory drilling was initiated in 1969, the East Hod
discovery weIl, 2/11-3a, was not drilled until 1977. Disappointing appraisal and delineation drilling
merely confirmed that the Hod Fields with a combined recoverable reserve of 25 mmstb. oil
equivalent, were of marginal economic value.
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Shallow upper Cretaceous Niobrara Gas Fields in the Eastern Denver Basin, Colorado, USA
More LessThe discovery of gas from the Cretaceous Niobrara chalk in
eastern Colorado's Yuma County was made by a local rancher in
about 1919. A weIl drilled with cable tools in what was to become
the Beecher Island field was completed for a reported flow of
2,000 MCFGPD.
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Porosity modelling of Danish chalk
Authors O. Nykjær and M. R. ØdumPorosity models have been generated for a number of Danish North
Sea chalk fields in order to improve the porosity mapping for
resource evaluation and reservoir simulation models in conjunction
with field development planning.
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The regional compaction pattern for the North Sea Chalk Group estimated from a normal velocity-depth trend
By P. JapsenThe Late Cretaceous-Danian Chalk Group is buried at depths varying from 0 to more than 3 km in the
North Sea Basin. Nature has thus conducted a dramatic experiment that allows us to study the effect of this
large depth variation on the seismic velocity and hence on the compaction of the chalk.
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A neural network application in integrated biostratigraphy of the Norwegian Sector, North Sea
Authors J. Yang-Logan, J. M. Hornell and C. R. YoungA neural network developed at Phillips Petroleum Company helps to characterize chalk
reservoirs to support chalk exploration, production, and modeling. The neural network is trained
trom samples for which fossil counts, age, zonation, paleoenvironment, biofacies, and mode of
deposition have already heen determined. The neural network training is used to identify
inconsistencies and possible finer zonations for the training examples. The trained neural network
is used to make determinations for new weIl biostratigraphic data.
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Synchronous variations in nannofossils assemblages and petrophysical parameters of North Sea chalks
Authors C. R. Young and E. A. SpinlerThe correlation between the ratio of reworked nannoplankton / total
nannoplankton population and chalk porosity has been routinely documented, in North
Sea wells, by Phillips biostratigraphers since the early 1980's.
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Well inflow phenomena in chalk gas condensate reservoirs - Effect of fluid sampling
Authors H. F. Fabricius and J. ReffstrupFluid flow and thermodynamic processes in saturated gas condensate reservoirs is complicated because
the composition of the saturated gas flowing to the weIl in the reservoir is altered during the production.
The pressure draw down at the well will cause heavy components to drop out of solution. When producing
from low permeability reservoirs as the chalk reservoirs in the Danish sector of the North Sea,
thermodynamic processes at the weIl are especially pronounced, because of the large pressure draw down
required to maintain production.
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A multidisciplinary approach to reservoir subdivision
Authors L. Kristensen, T. Dons, K. Maver and P. SchiølerCorrelation of wireline log data from North Sea chalk reservoirs is frequently hampered by
rather subtle log patterns in the chalk section. The present study deals with a correlation
technique based on an integration of biostratigraphic dating, seismic interpretation and
wireline log correlation.
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Porosity, permeability and specific surface of chalk from the Gorm Field, Danish North Sea
Authors J. Mortensen and I. LindThe Gorm Field of the Danish North Sea is an oil field with a reservoir In Danian and
Maastrichtian chalk. Core porosity and permeability data show that the chalk can be divided
into intervals with different relations between porosity and permeability.
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Chalk lithofacies, fractures, petrophysics and paleontology - An interactive study of chalk reservoirs
Authors W. T. Siemers, C. D. Caldwell, H. E. Farrel, C. R. Young, J. Yang-Logan and J. J. HowardInterpretation and integration of multidisciplinary data sets are essential for a better
interpretation of the internal geometry and architecture of the North Sea chalk reservoirs to better
support chalk exploration, production, and subsidence modeling.
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The mechanics of time-dependant strain in high porosity North Sea chalk
By D. W. RhettThe Ekofisk Field is a giant oil and gas field located in the southern region of the
Norwegian Sector of the North Sea. Since the Field went on production in 1971 it has produced
more than 1 boe.
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Nuclear magnetic resonance measurements of wettability and fluid saturations in chalk
By J. J. HowardThe surface-sensitive nature of proton NuclearMagnetic Resonance (NMR) relaxation makes it
an ideal probe to determine changes in wettability and fluid saturations of both experimentally altered
outcrop chalk and preserved-state reservoir chalk. The transformation of standard
NMR inversion-recovery data into a distribution of relaxation times clearly indicates the effect
of altering original wettability by significant shifts in the populations of relaxation times
observed in samples saturated with either water or hydrocarbon phases. Population densities
for the relaxation time components associated with both fluids correlate quantitatively with more
traditional volume displacement measures of fluid saturation.
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Modelling of fracture systems and fluid flow from analogue field studies
More LessPredicting fluid transport and mechanical properties of fractured formations is difficult because
of the complex spatial, geometrical and mechanical properties of three-dimensional fracture
networks, all of which must be inferred from well bore data or geophysical surveys.
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Fault patterns in the Eldfisk Field, central North Sea
Authors E. Rykkelid, A. Fritsen, P. Henriksen, D. C. Kitson, B. O. Korsfur and M. MartinesThe productivity of oil fields in the Central Graben depends on
an open fracture network: which enhances the effective
permeability of the chalk reservoirs.
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Chalks and chalk reservoirs of Tunisia with specific reference to the fractured reservoir of Sidi el Kilani
Authors A. B. Brahim and R. T. J. MoodyChalks and chalky limestones are recorded from the Upper Cretaceous and Lower Eocene of
Tunisia. The Cretaceous chalks are referred to the Abiod Formation and are of Campanian-
Lower Maastrichtian age (Figure 1).
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