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GEO 2010
- Conference date: 07 Mar 2010 - 10 Mar 2010
- Location: Manama, Bahrain
- Published: 07 March 2010
81 - 100 of 457 results
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Arabian Plate Sequence Stratigraphy: 10 Years On
Authors Michael Simmons, Stephen Cain, David Casey, Roger Davies, Alexis Godet, Peter Sharland and Owen SutcliffeAlmost 10 years have passed since Sharland et al. (2001) published Arabian Plate Sequence
Stratigraphy. This work correlated 63 maximum flooding surfaces across Arabia and, for the first time,
placed the complex lithostratigraphy of the Middle East into a sequence stratigraphic framework. We
will illustrate that:
- Since its publication we have developed the sequence stratigraphic model by further investigations in
the Middle East coupled with an analysis of the validity of the sequence stratigraphic model worldwide.
We now know that with some minor modifications, the Arabian Plate Sequences can be seen globally
and are thus eustatically driven. We have also been able to further develop the model with additional surfaces.
- It is interesting to speculate on the causes this eustasy throughout the Phanerozoic. The pace and
amplitude of the changes points strongly to a glacio-eustatic origin for our sequences this is supported
by a growing body of direct and proxy evidence that points to a coincidence of climatic fluctuation and
eustasy, suggesting that melting and creation of ephemeral polar ice may be a causal mechanism,
even in what is commonly regarded as a “greenhouse” times.
- A robust 3rd order sequence stratigraphic model for the Arabian Plate is a valuable tool for region
correlation and mapping, and the recognition of exploration analogues, as well as placing existing
reservoirs and source rocks in regional context.
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Controls from the Hydrocarbon Entrapment in Burgan and Wara Formations in Kuwait Offshore
Authors Fida Hussain, Riyasat Husain, Abdul Aziz H. Sajer and Ahmad Al-KandaryKuwait Offshore lies to the east of Kuwait with an aerial extent of about 10,000 Km2. It is not
comprehensively explored and only a few wells have been drilled to explore Cretaceous structural
prospects. The objective of the study is to bring out the depositional environments, distribution of
lithofacies and their control on hydrocarbon entrapment for Burgan and Wara Formations.
Burgan Formation of Lower to Middle Albian age is a thick clastic sequence, which is deposited in a
fluvial to marginal marine environment. The formation is broadly divided into two major sand packages
separated by a major shale unit. The lower sand package corresponds to lowstand systems tract while
the upper package corresponds to the highstand systems tract as well as lowstand clastics of the
overlying sequence. In upper Burgan, the fluvial and tidal sands that filled incised valleys are prolific oil
producers in the onshore. Reservoir quality deteriorates in the seaward direction as the valley systems
thin and become mud prone. Wara Formation of Cenomanian age is also a clastic sequence and
comprises of sandstone with interbedded shales deposited in an inner to middle shelf environment. The
formation corresponds to highstand systems tract of the sequence initiated in Upper Burgan. The thin
sandstone beds in Wara Formation are also known commercial producers in onshore.
Prospectivity analysis of the Burgan and Wara formations in Offshore Kuwait has indicated that
hydrocarbon occurrences are controlled by temporal and spatial variations of lithofacies. The study has
indicated that the Kuwait Bay appears to be the most prospective for exploration of these reservoirs in
terms of development of favourable lithofacies associations occurring in favourable structural setting.
High resolution sequence stratigraphy and depositional modeling is key to exploration of these
formations.
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Seismic Source Parameters Optimization in Shallow Water Area Offshore Abu Dhabi, U.A.E
Authors Tomohide Ishiyama, Derrick Painter, Kamel Belaid and Tamer SalehSeismic source parameters are one of the important specifications for a seismic survey. Conventional
thinking is that larger sources produce higher energy, and thereby improve data quality.
In shallow water areas offshore Abu Dhabi, U.A.E, OBC seismic survey is commonly acquired with airgun
array as the primary seismic source. However, the source size is limited due to operational
constraints such as shallow water depth and scattered production facilities. Although several seismic
surveys have been acquired in the region, the impact of source size on data quality is still open for
discussion. In this regards, a 2D-2C OBC pilot seismic survey was acquired in a shallow water area in
the region.
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Simultaneous Acquisition of Near Surface Geophysical Data
By Tom NicolsThis paper seeks to define the problems and solutions developed to enable the simultaneous
deployment and use of multiple geophysics instrumentation from a common platform using the GEEP
technology (Geophysical Exploration Equipment Platform) developed by Geomatrix Earth Science.
For the purposes of this paper the Geophysical boundary is set at the first 100M.
It may be argued that for basic Geophysical exploration tasks such as foundation studies that a single
geophysical tool might suffice. However when addressing more challenging tasks such as
Archaeological research, UXO detection, Karst location, waste location, mineral mapping etc it soon
becomes clear that more than one geophysical tool is not only desirable but is essential to a valid
survey outcome.
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Deepwater West Coast India - Pre-Basalt and Other Mesozoic Petroleum Plays
Authors Glyn Roberts, Charles Harmer, Ken Rutherford and Colin O‘BrienTo date, the main deep (>400m water depth) offshore exploration efforts offshore India has
concentrated on the East Coast where a number of large discoveries have recently been made in the
Krishna Godvari and other basins.
Now attention is turning to the deep offshore area of the West Coast of India where outside the
petroliferous (shallow water) province of the Mumbai High, exploration to date has been frontier in
nature with very few wells drilled.
Using recently re-processed seismic data (from a 12,000 km regional 2D seismic survey collected for
the DGH in 2002) we show how the application of modern seismic techniques (Radon Demultipe, PSTM
and PSDM) has upgraded the petroleum potential of the area - showing plays both in the Tertiary and
in the deeper Mesozoic section where a potential petroleum province can now be recognised below the
Deccan basalts. Our interpretation of this dataset shows that this Mesozoic province extends over
200km offshore and into waterdepths of up to 3500m - covering a large number of open blocks in
Indian territorial waters.
The paper draws on the geology of wells drilled in the Seychelles (and also refers to those in the Kutch
Graben) in order to build up a stratigraphic framework for the Mesozoic off the West Coast of India. It
is illustrated with numerous seismic examples (including data in depth)showing the petroleum potential
of the Mesozoic.
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The Applicability of Gravity Gradiometry as from Exploration Tool in East Dubai, U.A.E
Authors John Alfred P. Protacio, Jonathan Watson, Frank van Kleef and Georgeta PopaThe east of the Emirate of Dubai is dominated by the geologically complex western thrust front of the
northern Omani Mountains. This deformation front is the boundary between the western foredeep basin
and the eastern Omani fold-and-thrust belt.
Complex geology makes conventional exploration challenging. The reservoir (Thamama Group)
structures are thrusted anticlines with the overlying Tertiary units showing large-scale thrusting as well.
The Lower Cretaceous Thamama Group limestone is one of the main hydrocarbon reservoirs in the
Middle East. It forms a major hydrocarbon-producing reservoir in the U.A.E., Iraq, Bahrain and Oman
and has a high hydrocarbon potential in southeast Iraq, offshore Oman and offshore northeast Saudi Arabia.
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Application of C7 Hydrocarbons Technique to Geochemical Evaluation of Asmari and Bangestan Reservoir Oils in Marun Oilfield
Authors Farid Tezheh and Bahram AlizadehThe purpose of this study was to examine the potential of C7 light hydrocarbons as biomarkers for
petroleum exploration to geochemical evaluation of Asmari and Bangestan Reservoir Oils in Marun
oilfield. The Oils from Asmari and Bangestan reservoirs with a variable δ13C‰ ratio -27.10 to -
26.77‰ PDB, and Pristane/Phytane ratio from 0.78 to 0.91 shows the source rock of this oils should
be marine Marl-carbonate. The isomeric parameters of C7 included single-branched and multiplebranched
heptanes and isomeric pairs, such as nC7/Methylcyclohexane ratio vs. Toluene/nC7 ratio, 2-
MH+2, 3-DMP vs. 3-MH+2, 4-DMP, n-Heptane ratio vs. iso-Heptane ratio. The ratios for
nC7/Methylcyclohexane and Toluene/nC7 ranged from 1.5 to 1.8 and 0.53 to 1.23, respectively. The n-
Heptane value and iso-Heptane value ranged from 30.5 to 39.3 and 1.55 to 1.95 respectively and the
iso-alkanes (3RP), cyclopentanes (5RP), cyclohexanes (6RP) ratios ranged from 20 to 47.5%, 10 to
15% and 41 to 70% respectively. The use of this technique as a qualitative tool shows that all the oils
from the Asmari and Bangestan Reservoirs were Super mature, free of biodegradation and generated
from marine Marl-carbonate source.
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Minjur Sandstone Revisited: New Advances in Sequence Stratigraphy and Modeling in the Khashm-Al-Khalta Reference Area (Central Saudi Arabia)
Authors Benoît H. Issautier, Yves-Michel Le Nindre, Abdullah Memesh and Saleh DiniIn connection with the issues of CO2 geological storage in complex reservoirs, the Minjur Sandstone, in
outcrop in Central Saudi Arabia, was selected as a case study for modeling and simulating the spatial
distribution of sand bodies in a fluvial-deltaic system. As a first step, detailed sedimentologic mapping,
sequence stratigraphy and 3D geological modeling were performed in the area of inlet/outlet maximum
activity of the deltaic system.
Compared to the reference studies by Vaslet et al.(1983) and Le Nindre et al., (1987, 1990), the
vertical and lateral variations around the type section were studied in detail, and interpreted with
greater accuracy in terms of depositional features and sequence stratigraphy. This new survey was
specifically designed to collect 3D information for numerical modeling.
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3D Localized Prestack Depth Migration from Workstations
Authors Xiaomin Zhao, Jianming Sheng, Ying Hu and Chengbin PengWe have recently developed a localized prestack depth migration workflow based on proprietary
technology that is equivalent to Gaussian Beam migration. This workflow enables the 3D prestack
seismic depth imaging of a target volume within a few hours or even minutes. The work flow can be
performed on a single workstation or a cluster of compute nodes, and the quality of the results is very
good, consistently better than Kirchhoff, WEM, and beam migrations. In contrast to conventional
workflows that typically require weeks or even months for an updated prestack seismic depth
migration volume to be produced, the new toolkit provides a near real-time solution to prestack depth
imaging. The migration works for both isotropic and anisotropic velocity models (VTI and TTI), and
handles data acquired with narrow or wide azimuth acquisition geometries. Real data examples are
presented here to demonstrate the new workflow.
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Accurate Conversion between Offset Image Gathers and Angle Image Gathers
Authors Jianming Sheng and Chengbin PengMost migration methods produce either common-offset-gathers (COG) or common-angle-gathers
(CAG) gathers. But none produce both, that is until now. We have developed an accurate and efficient
method that converts common offset image gathers to common angle image gathers, or vice versa.
The practical uses of the method are for velocity analysis or AVO studies using existing commercial
toolkits.
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Non-Hyperbolic Reflection Tomography for Better Imaging and Interpretation
Authors Zhaobo Meng and Chengbin PengIn this abstract we will demonstrate that the application of non-hyperbolic reflection tomography can
produce a 3D subsurface velocity model that is smooth for prestack depth migration and at the same
time geological for accurate subsurface pore pressure prediction and lithology interpretation. Our nonhyperbolic
reflection tomography workflow is very different from the conventional reflection
tomography workflow: no automatic volume picking of residual moveout is used. Instead a set of
prestack events are interpreted on prestack seismic image volumes. The prestack events carry detailed
moveout information that is more accurate than a single parameter fit to the common image gathers.
In addition the prestack events carry structure dip information that is needed for accurate 3D ray
tracing offset by offset. Examples will be given for both compaction driven and lithology controlled
geological environments.
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Gaussian Beam De-Migration and Re-Migration
Authors Jianming Sheng and Chengbin PengIn this abstract we will present a theoretical framework for demigration of seismic image data under
the frame work of Gaussian Beam theory. The underlying methodology has no dip limitation and
handles multi-valued arrivals well. The practical use of this technology is to perform prestack
demigration of existing image volumes (CIG gathers) followed by prestack depth remigration using a
replacement velocity and/or anisotropy model. The result is a fast, accurate, and cost effective way to
improved seismic imaging as compared to proprietary reprocessing from field tapes.
Ross Hill published seminal works in common offset Gaussian Beam prestack depth migration (Hill,
1991 and 2001). Chevron has been largely the only beneficiary of the Gaussian beam technology. To
the best of our knowledge there have been no published work on Gaussian beam prestack demigration.
For example, in prestack demigration, one can start with an individual common offset image volume
(Kirchhoff migration volume, Gaussian beam migration volume, or fast beam migration volume). The
single fold image is demigrated to reconstruct the corresponding input unmigrated seismic data. In
Gaussian Beam prestack demigration, we actually reconstruct the individual beams used as input to
the original Gaussian Beam migration. The individual beams are then synthesized to form an
unmigrated seismic volume.
There are many uses of Gausian Beam prestack demigration technology. For example, it can be used
as a fast forward modeling tool to generate synthetic data for migration and inversion. Another use of
this technology is to perform prestack demigration of existing image data, followed by prestack depth
(re)migration with a replacement velocity and/or anisotropy model. This is a faster, more accurate and
cost effective way of seismic imaging over proprietary reprocessing from field tapes. Both synthetic
and field data examples of this will be shown.
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Plays and Prospectivity Offshore Lebanon, Syria and Cyprus: New Insights from Depth Imaged Seismic Data
Authors Glyn Roberts, Charles Harmer and Dave PeaceThis paper illustrates the nature of the Levantine Basin and adjacent areas based on an analysis of
modern seismic data. It shows that the Basin is comprised of a substantial thickness (> 10,000
metres) of Mesozoic to Cenozoic sediments above a rifted terrain of probably Triassic- Lower Jurassic age.
Depth imaged sections are used to show the nature of the Basin including its relationship to the
Eratosthenes Seamount and the Larnaca Thrust Zone.
Depth imaged sections (with Time Migration comparisons) are also used to illustrate some of the
numerous plays seen in the area. These consist of:
1)Jurassic and older: faulted structures, rollovers and basin margin plays.
2)Upper Jurassic to Middle Cretaceous: mounds, reefs, progrades, drape structures,
structural/stratigraphic plays and unconformity plays.
3)Middle Cretaceous to Paleogene: anticlines, fault blocks, rollovers, mounds, drapes,
structural/stratigraphic plays and basin margin pinch-outs.
4)Sub-Salt (with salt as the seal) and Intra-Salt (Messinian): pinchouts, bright spots, channels and mounds.
5)Post Salt (Pliocene to Recent): channels and mounds.
Depth imaging of the seismic data is shown to aid the evaluation of many of these plays and to
highlight the prospectivity of offshore Lebanon, Syria and Cyprus.
Reference will also be made to both the ongoing and future bid rounds; and to some of the issues
involved in producing velocity models for Pre Stack Depth Migration including the subsequent time
conversion of depth migrated data.
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Undepleted Pockets of Gas Detected Using Coupled Modeling of Subsidence and Reservoir Depletion Processes
More LessAn important cause of subsidence is the withdrawal of large volumes of natural gas, oil and water from
hydrocarbon reservoirs. Every point of depletion in the subsurface causes a subsidence bowl with a
radius corresponding to the depth of the depletion point. The depletion of a large volume in the
subsurface leads to a subsidence bowl of which the shape and the size are directly related to the
subsurface properties and processes. Besides the amount of hydrocarbons produced and the geometry
of the reservoir, relevant features include the subsurface elasticity profile, the compaction coefficient
and the strength of the aquifer.
Surface subsidence measurements (e.g. Interferometric Synthetic Aperture Radar (InSAR), leveling
measurements, or GPS) can be used to better quantify the subsurface parameters and processes.
Simple inversion approaches do not usually provide a sensible solution due to non-uniqueness of the
solution and the sensitivity of the inverse problem to small fluctuations in the data. We have developed
a time-integrated inversion scheme for resolving the spatial and temporal reservoir pressure drop from
surface subsidence observations. This inversion procedure is unique because it utilizes all the available
prior knowledge including the uncertainty and the correlations within it. Elements of this prior
knowledge are the geological model, the reservoir model, the sealing properties of faults, and the acquifer activity.
We have applied our inversion method to a highly compartmentalized reservoir in the Netherlands
where we used the observed surface subsidence (leveling), the geological model, the reservoir model,
and the prior knowledge about possibly sealing faults, to obtain insight into undepleted pockets of
natural gas in the reservoir. We used prior models which complied with the measured flux and pressure
measurements of the production profile. With these data, we were able to better quantify the amount
of compaction in the different compartments in the reservoir and the pressure depletion causing it.
The approach followed is essentially a two-step approach: the history match is the first step, and the
inversion of subsidence measurement the second. The risk of this approach is that not the complete
solution space is being searched. We are currently also developing an approach in which the inversion
of production data and subsidence measurements are integrated.
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The Levantine Basin - Prospectivity in a Frontier Basin
Authors Thore Sortemos, Caroline J. Lowrey, Cecilie Skiple and Mark TrayfootThe prolific Nile Delta to the south is an active petroleum province, but exploration activity in the deep
water Levantine Basin offshore Cyprus, Israel and Lebanon has been limited. However, the recent deep
water subsalt gas discoveries offshore Israel, the announced 2nd licensing round offshore Cyprus in
2009 and the planned 1st licensing round offshore Lebanon has spurred a significant increase in
industry interest in the area.
The Levantine Basin is bound to the east by the Levantine margin, to the north by the Latakia Ridge
and to the west by the Erastosthenes Seamount and is interpreted as a Mesozoic transform rift graben.
Our interpretation and the Tamar discovery indicate that much of the pre-Messinian sedimentary
package in the Levantine probably consists of Oligocene to Miocene successions, rather than the Early
Cretaceous/Senonian successions suggested previously.
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Komombo: A New Oil Province in Upper Egypt
Authors Mohamed Fathy, Leonardo Salvadori, Glyn Roberts and Moussa Abu GoudaThe paper discusses some of the geological and geophysical work performed in Centurion’s Block 2
concession area in Upper Egypt; and which lead to the discovery of the Al Baraka field in 2007 -
leading to the opening up of a new petroleum province in the Mesozoic rift basins of Upper Egypt.
The Komombo Block-2 Concession is located on the west bank of the Nile River, about 570 km SSE of
Cairo, and about 260 km east of the Red Sea. It was part of a larger former Repsol concession which
was relinquished in 2001 after the drilling of five wells.
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Reservoir Connectivity and Fluid Uncertainty Analysis Using Fast Geostatistical Seismic Inversion
Authors Ashley M. Francis and Graham HicksStochastic seismic inversion (Haas and Dubrule, 1994; Francis, 2006) enables the uncertainty in
seismic inversion to be explored. Additional information in the well logs is statistically exploited in
accordance with the variogram model. Each stochastic seismic inversion realisation has a spatial
constraint imposed by a variogram, is conditional to the well and stratigraphic horizon data and is
conditional to the seismic data within the bandwidth of the wavelet. Using a frequency domain fast
stochastic seismic inversion algorithm a sufficiently large number of stochastic realisations enables
probability and 3D connectivity volumes corresponding to lithology or fluid indicators to be generated.
Two applications of 3D Connectivity analysis of stochastic seismic inversion realisations are presented.
In the first example using post-stack seismic inversion impedance realisations, the acoustic impedance
is classified by sand and shale discriminators (Francis, 1997). The sand indicator is used to process
each realisation using 3D connectivity to identify geobodies. By selecting realisations containing
geobodies which are consistent with known connectivity criteria between wells, these realisations can
be used as candidates for constraining geostatistical modelling.
In the second example, pre-stack seismic inversion results and a rock physics analysis are used to
identify hydrocarbon fluid effects from the seismic response. Pre-stack inversion using Extended Elastic
Impedance (Whitcombe et al, 2002) is used to generate a large number of joint stochastic impedance
realisation pairs. Based on the rock physics analysis the EEI impedance realisation pairs are rotated to
obtain pairs of optimal fluid and lithology predictor realisations. The rotated realisation pairs are used
to evaluate the probability of new well targets being partially depleted by existing production, to
estimate sand volumetric uncertainty and to perform a risk analysis of a proposed horizontal well trajectory.
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Processing Methods for Extracting Subsurface Information from Ambient Seismic Noise
Authors Barbara Schechinger, Alexander V. Goertz and Marc LambertThe ambient seismic wave field carries information about the subsurface in the vicinity of the recording
site. It also carries a lot of less useful information about anthropogenic activities nearby. Potentially
interesting variations in the naturally occurring seismic background wave field happen at extremely low
power spectral density levels (typically between -120 to -180 dB [w.r.t. 1 m/s]), and is oftentimes
masked by noise of anthropogenic origin. In addition, the spatial, temporal and frequency-domain
variability of cultural noise often exceeds the variations of the natural background wave field. It is
therefore critical to remove any influence of cultural noise from the records before an attempt can be
made at analyzing the ambient seismic noise level with respect to any meaningful signatures of
subsurface variations. Here, we present methods to characterize the ambient seismic wave field
recorded with broadband seismometers and propose methods for extracting subsurface-related
information. The analysis includes the characterization of spectral signatures of different types of
sources (both anthropogenic and natural origin), as well as spectral signatures that are indicative of
the subsurface underneath the recording site. The characterization also drives the selection of certain
noise-removal techniques. Due to the typically small amplitude of these subsurface-related variations,
it is critical to remove as much of the surface energy as possible, and to correct for near surface effects
in the recorded data. Analysis of the cleaned data then allows looking for special attributes that may
carry subsurface information. A possibly important tool for achieving these goals is the ratio between
vertical and horizontal components (V/H) in the frequency domain. In this domain, the receiver terms
contain information about the shallow subsurface, but sometimes also information about fluid content
in the deeper subsurface. Both pieces of information can be of use in practical applications. For
illustration, we present examples from low-frequency passive seismic (LFPS) surveys with particularly
strong anthropogenic noise contaminations. We show that, despite remnant contamination of the
records by anthropogenic noise, we observe statistically significant variations of spectral attributes that
can be used for subsurface characterization.
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Seismic Repeatability - Is There a Limit?
The results of a 13-day seismic monitoring experiment are presented. It consists in 2 permanent
piezoelectric sources, one cemented in depth and the other attached to a surface concrete pad and 28
sensors, 14 at the surface and 14 cemented below the weathering zone.
To enhance the signal-to-noise ratio, continuous averaging of the individual SP records is performed
providing an average daily SP. 4D attributes are measured on these daily averages. The best
repeatability is obtained when both sources and sensors are buried with time and amplitude variations
of 6 μs and 0.5% respectively. This extremely high precision level is far above what can be expected
from the most accurate surface acquisition methods currently available.
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Reservoir Facies and Sequence Stratigraphy of the Khasib Formation in Selected Fields from Central Iraq
More LessThe bioturbated chalky limestones of the Khasib Formation (Upper Turonian - Lower Coniacian) furnish
an extensive reservoir rock of several oil fields in central Iraq including: Tikrit, Balad, Samarah, and
East Baghdad oil fields. Investigation of these rocks by means of microfacies analysis and electrofacies
correlation as well as sequence stratigraphic analysis indicate that it had being deposited in a ramp
setting sloping east- southeastwards forming part of the Arabian passive margin.
The inner ramp is characterized by a bioclastic packstone of a carbonate bank with green shale
intercalations of peri-bank sediments. The middle ramp which dominate the Khasib Formation section
is consist of white- beige, porous, bioturbated, chalky and dolomitic bioclastic wackestone. Bioclasts
includes; shelf faunal debris with variable mixture of benthic and planktonic forams. Intensive
Thalasionodes and Palaeophycus bioturbations significantly contributed to the high porosity of this part.
The outer ramp is consists of intercalations of boiturbated bioclastic chalky limestone and basinal
argillaceous limestone. The latter is characterized by the occurrence of planctonic forams, calcispheres,
dwarf rotalids and sponge spicules.
The Khasib section represents a third order cycle with lower sequence boundary of type one separating
Khasib sequence from the underlaying LST of the Kifl Formation. The TST is consist of thin and basinal
facies. The HST is the thickest and represented by the bioturbated chalky limestone of the middle ramp
facies. The maximum flooding surface is idicated by a thin horizon dominated by intensive Paleophycus
bioturbation within the middle ramp facies. The boundary with the overlaying Tanuma Formation is of
type two and represented by the transition to the LST of the next cycle.
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