3D Geophysics exams

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Greetings,I have attached three files which are two old exams and they are the same exam and My pics of the project which I did them and they are same in old exams. I would like to redo a new exam by using my own pics and the old exams. through to use the same words from the old exams, but paraphrasing the word to not be plagiarism. Then to use my own pics instead of the pics in the old exams. Anyways, my exam is the same in the two old exam, but some steps may not be in my instructions exam which I am going to attach it as soon as possible. REMEBER IT IS WORTH 45% OF OVERALL and my goal is to get an A which is everything, old exams and pics are offered.Regards,

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GEOL 556
Gullfaks, North Sea
3 D Seismic Interpretation
Final Report
Joseph J. Filchock
December 14, 2015
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Table of Contents
Abstract ……………………………………………………………………………………………………………………………3
Objective and Research Methods …………………………………………………………………………………………..6
Seismic Expression of the Unconformity ………………………………………………………………………………….6
Structural Style …………………………………………………………………………………………………………………..8
Potential Hydrocarbon Traps and Migration Pathways ………………………………………………………………..9
Potential Prospects…………………………………………………………………………………………………………… 11
Conclusion ……………………………………………………………………………………………………………………… 13
References ……………………………………………………………………………………………………………………… 14
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Abstract
The Gullfaks oil and gas field, in the northern part of the Norwegian North Sea off the coast of
Norway the main Gullfaks field is located in block 34/10 of the above mentioned sea. The
Gullfaks field is in a large rift basin and as such a graben system as expected from the
extensional history of the basin, this graben system can be seen in the 3D seismic da ta
processed in this assignment.
Figure 1: Faults and graben system shown from 3D seismic in PETREL at inline 270, base cretaceous is approximated by the yellow line.
This field is a prolific producer of hydrocarbon that was discovered in 1978 and began
production in 1986. Production from this field is from Jurassic to Cretaceous age geological
formations.
The field consists of three smaller fields: Gullfaks South, Rimfaks, and Gullveig which have
produced 2.6 * 10^8 barrels of oil and or condensate through phase one. A production rate of
about 100,000 barrels per day is achieved through three offshore platforms: Gullfaks A, B, and
C.
Seismic data was made available for the project in order to complete the assignment. 3 D
seismic data will be analyzed using PETREL software that was developed by Schlumberger. The
geological structures and complexities can be analyzed and understood by the reservoir
engineers, and petrophysicists through the use of the PETREL software.
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Potential hydrocarbon traps and plays are can be found easier and more efficiently using RMS
amplitude and other functions of the software. The software will allow seismic complexities to
be analyzed and separated into components to apply classification techniques to both the
seismic attribute data and associated reservoir structural styles.
The determination of many parameters will be accomplished using many attribute analysis
completed through the PETREL software using the techniques learned throughout the semester
in lab assignments and lectures. This includes breaking down the seismic response data into
horizons of similar amplitude at a given response time. As the horizons are being interpreted
through inline and cross-line of the seismic volume the fault network may become visible as
well which can be interpreted at this time as well.
Figure 2: Location of the Gullfaks field (Statoil)
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Figure 3: A diagram showing the production platform Gullfaks A and the three sub fields of the Gullfaks field (Statoil)
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Objective and Research Methods
The objective of this assignment was the subsurface representation and visualization of the
many and complex structural variation of the Gullfaks petroleum system in the North Sea. We
would also like to gain an understanding of the architecture of the basin. In gaining a better
understanding of the basin and its geological structures we should come to a better
understanding as to possible hydrocarbon traps, migration pathways, and further areas that are
possible future recommendation for exploration and further well planning.
3D seismic data was manipulated in the software to prepare and interpret the respective
horizons. Structural contour maps were used to illustrate the thicknesses of potential prospects
and isopach maps were also prepared for the formations. Structural contour and isopach maps
were studied to interpret style of the major structural elements present there. Geobodies were
extracted from RMS seismic volume to further study the play for and to gain an understanding
of volumetrics of basin/reservoir lithofacies.
Seismic Expression of the Unconformity
The following images show the unconformity which separates the overlying shallow-dipping
formations from underlying steeper-dipping formations. This unconformity also delineates the
younger shallower facies from the older rock formations and usually results from subsidence,
and erosion of the surface of the older bed, before deposition of the younger sedimentary
formations. From the study of Geoblobs create from RMS amplitude volumes there appears to
be a large volume of sand that can be produced from.
Figure 4: inline 290 showing “base cretaceous” and horizon place above and below it also on power point
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It can be seen in these time slices that reflectivity and amplitude remain pretty constant above
the unconformity but below things get chaotic.
Figure 5: Amplitude time slice above the unconformity, there isn’t a whole lot of variation time 1450 ms
Figure 6: Below the “base Cretaceous” amplitude and reflectivity changes drastically as the formation is dipping more steeply time 1750ms
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Structural Style
As stated earlier the basin in which this field is located is a rift basin and as such the structures
are of an extensional nature. Further proof of the extensional nature of the geology of the basin
can be seen in the formation of graben, or domino style fault blocks as shown below.
Figure 7: With domino style faults and subsiding hanging walls typical of a graben structure form during extensional stress
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Potential Hydrocarbon Traps and Migration Pathways
This field shows both structural traps and stratigraphic traps I will provide examples and
illustrations of each. The illustration below shows some trap that have the potential for
hydrocarbon production if we were to take the time to identify them all would be present
except salt dome traps, and reef traps.
Figure 8: Example of petroleum traps (source http://www.gly.uga.edu/railsback/PGSG/PGSGmain.html)
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Figure 8: Structural trap created by the fault sealing the sandstone formation
Figure 9: Possible stratapghic trap blue arrow, and migration pathways red arrows
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Potential Prospects
The following figures will show some potential good geobodies for future exploration, all are
sands some have been sealed by the faulting, some stratigraphically as they are bounded by
shale.
Figure 10: Potential prospects the ones above the unconformity are stratigraphic in nature, and the ones below structural inline 232
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After incorporation with well logs some of these geobodies will be deemed unproductive but
some areas have had no drilling activity to speak of and may be targets for further exploration.
Figure 11: An overview of potential prospects as interpreted from RMS amplitude volume
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Conclusion
The included PowerPoint slides present more of the deliverables as required for this
assignment.
Structural contour along with isopach maps indicate much structural variation of the Gullfaks
field. The base cretaceous unconformity which; is the most prominent structural feature has
divided the basin into two parts a highly faulted, steep dipping, lower older sequence and a
post-rift sequence that is shallower dipping and less faulted. The sequences below the
unconformity mostly form structural petroleum traps, while those above seem to have some
stratigraphic trap features. Of course whether or not oil will migrate above the unconformity is
questionable, some migration pathway seem to exist to charge the potential reservoirs. What I
find extremely interesting is the stark difference between the formation above and below the
unconformity, these differences allow the presence of many differing styles of petroleum traps.
After doing this project it is no wonder why the North Sea field and the Gullfaks field have been
such prolific producers, I feel exploration may still be needed.
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References
Dr. Gao, D West Virginia University Geology 556 lectures and course notes Fall 2015
Petrel software by Schlumberger
http://www.statoil.com (Accessed 14th December, 2015)
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2014
3D Seismic Visualization
and interpretation
GEOLOGY 556
FUAD ALBAYATI
WEST VIRGINA UNIVERSITY | INCTRUCTUR: DR. DENGLIANG GAO
Table of Contents
Introduction……………………………………………………………………………………………………………………3
Methodology ………………………………………………………………………………………………………………….4
Smoothing the Seismic Data: ………………………………………………….. Error! Bookmark not defined.
Recognizing Unconformity at Base Cretaceous …………………………………………………………………..4
Generating the Horizons ………………………………………………………………………………………………..5
Generating Surfaces for the Horizons………………………………………………………………………………..6
Generating Thickness Maps ……………………………………………………………………………………………8
Extracting RMS Amplitude …………………………………………………………………………………………….9
Generating RMS Amplitude Volume and Variance Volume …………… Error! Bookmark not defined.
Generating Seismic Geobodies by using RMS Amplitude data. ……………………………………………. 11
Generating Major Faults below the Base Cretaceous (unconformity)……………………………………… 13
Interpretations and conclusions ………………………………………………………………………………………… 14
Seismic Expression of the unconformity …………………………………………………………………………. 14
The Structure Style …………………………………………………………………………………………………….. 15
Potential Hydrocarbon Traps Structure Vs. Stratigraphic…………………………………………………….. 16
Potential Migration Pathways ……………………………………………………………………………………….. 17
Potential Prospect to Drill ……………………………………………………………………………………………. 19
1
Figures
Figure (1) Seismic Data before and after smoothing (inline 252) ……………. Error! Bookmark not defined.
Figure (2) Unconformity at Base Cretaceous …………………………………………………………………………….4
Figure (3) Horizon Picking……………………………………………………………………………………………………5
Figure (4) Surface 1 from Horizon 1 ……………………………………………………………………………………….6
Figure (5) Surface 2 from Horizon 2 ……………………………………………………………………………………….6
Figure (6) Surface 3 from Horizon 3 ……………………………………………………………………………………….7
Figure (7) Surface 4 from Horizon 4 ……………………………………………………………………………………….7
Figure (8) Thickness Map between Surface 1 and Surface 2 …………………………………………………………8
Figure (9) Thickness Map between Surface 3 and Surface 4 …………………………………………………………8
Figure (10) RMS amplitude – surface 1 ……………………………………………………………………………………9
Figure (11) RMS amplitude – surface 2 ……………………………………………………………………………………9
Figure (12) RMS amplitude – surface 3 …………………………………………………………………………………. 10
Figure (13) RMS amplitude – surface 4 …………………………………………………………………………………. 10
Figure (14) RMS Amplitude Volume ………………………………………………. Error! Bookmark not defined.
Figure (15) Variance Volume ………………………………………………………… Error! Bookmark not defined.
Figure (16) Generating the Box Probe from RMS amplitude volume……………………………………………. 11
Figure (17) Geobody extracted in 26 way ………………………………………………………………………………. 12
Figure (18) Geobody’s potential sand Volumes ………………………………………………………………………. 13
Figure (19) Major Faults in interpretation window-inline 228 …………………………………………………….. 14
Figure (20) Major Faults in 3D Window………………………………………………………………………………… 14
Figure (21) seismic expiration above and below the unconformity ………………………………………………. 15
Figure (22) Structure Style …………………………………………………………………………………………………. 16
Figure (23) Potential migration pathways ………………………………………………………………………………. 18
Figure 24 Possible migration pathways along the fault (leakage) ………………………………………………… 19
Figure (25) Potential prospects to drill ………………………………………………………………………………….. 20
2
Introduction
The Gullfaks Field is located in the Norwegian Sector of the North Sea, block 34/10, and it used
to produce more than 440,000 STB/Day Oil from three concrete platforms. The reservoir unites
are sand witch represent shallow marine to fluvial sediments of the Cook Formation, Statfiord
Formation and Brent Group(Tollefsen et al,1992) . The geological age is ranging from Early to
Middle Jurassic.
The Gullfaks Field is characterized by two structurally distinct partitions “Domino Area’ with
rotated fault blocks in the west, and a Horst area in the east; in between is a complex ‘Adaptation
Zone’, characterized by folding structures” (Hesjedal, Arild).
In this report we are going to use multiple seismic attributes, visualization and interpretation
methods to study Gullfaks seismic data, this include making surfaces, extracting amplitude
variation, generate geobodies and interpreting potential major faults. The purpose of the project
is to understand the structure and stratigraphy of the field and find potential migration pathways
for hydrocarbons, also to find potential traps and prospects to drill wells based on the analysis.
3
Methodology
Recognizing Unconformity at Base Cretaceous
The unconformity surface witch is separating the underlying step dipping from overlaying
shallow dipping formation could be seen clearly at inline 212.
Unconformity
Figure (1) Unconformity at Base Cretaceous
4
Generating the Horizons
Interpretation window is used to pick the horizons by depending on the inline and cross line
slicing. Two horizons are picked above the unconformity (almost flat) and two horizons below
the unconformity (more difficult to pick).
Horizon 1
Horizon 2
Unconformity
Horizon 3
Horizon 4
Figure (2) Horizon Picking
5
Generating Surfaces for the Horizons
The surfaces are generated for each horizon and smoothed with surface width of 3. Following are
each surface showing the contour lines and color bar:
Surface 1 at ~ 1450ms is almost flat and it is above the unconformity.
Figure (3) Surface 1 from Horizon 1
Surface 2 at ~ 1650ms is almost flat with dipping a bit at the northwest and it is above the
unconformity.
Figure (4) Surface 2 from Horizon 2
6
Surface 3 below the unconformity and many faults cutting it and makes it difficult to pick.
Figure (5) Surface 3 from Horizon 3
Surface 4 also below the unconformity and many faults are cutting and parting it.
Figure (6) Surface 4 from Horizon 4
7
Generating Thickness Maps
Thickness maps are generated between surface 1 and surface 2 and between surface 3 and
surface 4. It helps to understand the deposition environment and potential faults.
Figure (7) Thickness Map between Surface 1 and Surface 2
Figure (8) Thickness Map between Surface 3 and Surface 4
8
Extracting RMS Amplitude
By using surface attributes RMS Amplitude are extracted for each surface with search windows
5 ms. above and below the surface.
Figure (9) RMS amplitude – surface 1
Figure (10) RMS amplitude – surface 2
9
Figure (11) RMS amplitude – surface 3
Figure (12) RMS amplitude – surface 4
10
Generating Seismic Geobodies by using RMS Amplitude data.
A Geobody is a 3D object extracted from a seismic volume. Here we used RMS
amplitude seismic volume to extract the Geobody. Extracting higher amplitude areas to
discrete volumes helps to highlight the potential sand reservoir and to decide where to
drill new wells in the reservoir.
Figure (13) Generating the Box Probe from RMS amplitude volume
Extracting the Geobody from the above box probe in 26 ways and by using the default
setting after applying opacity to higher amplitude areas.
11
Figure (14) Geobody extracted in 26 way
From figure (17) we could say that there are two sand volumes in the north east of the
field below the base cretaceous, and it will be a good prospect to drill new wells. Also,
following are the volume of sand that each color represent in the previous figure:
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Figure (15) Geobody’s potential sand Volumes
Generating Major Faults below the Base Cretaceous (unconformity).
There are 5 to 7 major faults that are intersecting the structure and making it a good
hydrocarbon trap.
13
Figure (16) Major Faults in interpretation window-inline 228
Figure (17) Major Faults in 3D Window
Interpretations and conclusions
Seismic Expression of the unconformity
14
The unconformity at base cretaceous is isolating the shallow dipping formation above it from the
step dipping formations below it. See figure (21).
Above Unconformity
Below Unconformity
Figure (18) seismic expiration above and below the unconformity
The shallow dipping formation is younger than the underlying step dipping and not affected with
extensional tectonic movement that formed the below unconformity .Also , seismic data showing
several major faults that intersected and deformed the underlying step dipping formations.
The Structure Style
15
Extensional tectonics and rifting formed the Gullfaks field; the normal major faults direction and
trends help to understand the extensional strains. Also, strike slip faults or transform faults occur
in the structure but have minor effect on deformation comparing with dip slip faults.
Normal faults
formed by
extensional
movements
Figure (19) Structure Style
Potential Hydrocarbon Traps Structure Vs. Stratigraphic
16
The major faults areas consider a potential hydrocarbon traps (Structure traps) and highamplitude reflection are referring to that, see fig (22). On the other hand, there is a potential
stratigraphic trap in the base cretaceous, where the flat formation above the base cretaceous form
a barer and high amplitude in that area refer to the top of the base cretaceous reservoir. From
seismic amplitude data, structure traps are better than the stratigraphic trap in Gullfaks field.
Potential Migration Pathways
17
There are potential vertical migration pathway along the major faults with possible leakage. Most
major faults in the Gullfaks field are very stepping which makes the possibility of vertical
migration very high. Also, by taking a look at the RMS amplitude that we have generated for the
surfaces below base cretaceous, we could see the increasing in amplitude from lower Jurassic
towards base cretaceous, see figure (23).
Figure (20) Potential migration pathways
In addition, the high density of normal faults point to more small fracture that might be shorter
ways for the hydrocarbon to migrate laterally too. We can see that by looking at RMS amplitude
along the fault surfaces with available RMS for horizons.
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Figure (21) possible migration pathways along the fault (leakage)
Potential Prospect to Drill
We can find potential prospects to drill in the reservoir by extracting Geobodies from seismic
volume. The RMS amplitude volume is used to extract geocodes (Fig 16), so according to the
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sand volumes that we get from Geobody interoperation the north east part of the Gullfaks field
has a good prospect to drill. This prospect is under the unconformity, and there are two major
faults that may form this structural trap. However, unconformity considered a cap rock for this
potential reservoir.
In addition, the south-west part of the field also has some potential spots to drill, but the sand
volume that extracted from high amplitude area is smaller than the north eastern part.
North Eastern
prospects
South Western
prospects
Figure (22) Potential prospects to drill
References
20
Fossen, Haakon, and Jonny Hesthammer. “Structural geology of the Gullfaks field, northern
North Sea.” SPECIAL PUBLICATION-GEOLOGICAL SOCIETY OF LONDON 127 (1998):
231-262.
Hesjedal, Arild. “Introduction to the Gullfaks Field.” Norwegian University of Science and
Technology. Statoil, n.d. Web. 12 Dec. 2014.
Tollefsen, Svein, Eirik Graue, and Stein Svinddal. “The Gullfaks Field development: challenges
and perspectives.” European Petroleum Conference. Society of Petroleum Engineers, 1992.
21

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