Group1 Geology

7/29/2019 Group1 Geology

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GEOLOGIC MAP INTERPRETATION

RELATIVE AGE:

Shale

Sandstone

Unconformity

DYKE And SILL

Igneous rock intrusion and accompanying regional metamorphism

Sandstone

This was achieved by applying classical stratigraphic principles. These are the principles of (1) OriginalHoriz(2) Superposition, (3) Lateralcontinuity, (4) Cross-cuttingrelationships.

Youngest

Oldest


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Features and Sequence of events

X is sandstone

B is an Igneous Rock intrusion

Z shows a relationship to the igneous body and can bebest described as a region of metamorphism (changes in

mineral assemblage and texture that result from subjecting

a rock to conditions such as pressures, temperatures, and

chemical environments)

C is a Dyke and D is a sill

T is Sandstone A is a non-conformity

Y is shale

Sandstone was deposited first- earth forces acted on this layer causing a deformation of the layer (tilting

and folding) Igneous rock intrusion accompanied by Z which can be best described as a zone of metamorphism

Applying the principle of cross-cutting relationship, after the intrusion the dyke C cut across the igneous

formation (country rock) followed by D which is a Sill

After this there was a break in deposition accompanied by weathering and erosion which gave rise to an

unconformity (non-conformity)and subsequent deposition and erosion of the sandstone which tapers to

the right.

Finally, shale was deposited on the sandstone making it the youngest layer (principle of superposition).

SEQUENCE OF EVENTS


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TITLE

THE ROCKS SEEN

Sandstone A, Conglomarate B,Limestone D, Shale C, Salt dome G

THE RELATIVE AGES OF THE ROCK

The geological feature salt-dome is the youngest rock form secondly

D,C,B,A and G which is the oldest to the youngest rock


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THE GEOLOGICAL FEATURES

Anticline fold is indicated in green and the syncline fold is in red, fault is F

There was a deposition of limestone originally D

then erosion of the limestone occurs and also deposition of shale and

conglomerate and sandstones occurred

The red and green fold were created as a result of compression acting onthe joint formation and this created the fault F

We have the dyke formed as a result of intrusion at the surface due to

surface erosion


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MAJOR SUBDIVISIONS AND BRIEF GEOLOGICAL HISTORYOF THE NIGERIAN NIGER DELTA BASIN

Major subdivisions of

the Nigerian Niger Delta

are;

Benin formation Agbada formation

Akata formation

GEOLOGICHISTORY

Separation of the continental crust of the South America and Africa plates in the late Jurassic

rift, the event followed by early cretaceous subsidence of the African continental margin. . The

most important linked events in the chain of geologic episodes that built the Niger delta wasthe initiation of the Benue trough and its sequential filling up of marine sediments following

the cretaceous transgression (Reyment, 1955; Reyment and Tait, 1972)

The coastal sedimentary basin of Nigeria has been the scene of three depositional cycles.

The first began with a marine incursion in the middle Cretaceous and was terminated by a mild

folding phase in Santonian time.

The second included the growth of a proto-Niger delta during the late Cretaceous and ended in a

major Paleocene marine transgression.

The third cycle, from Eocene to Recent, marked the continuous growth of the main Niger delta.


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BENIN AGBADA AKATA

Environment of

Deposition

Continental

environmentTransitional

environmentMarine

environmentThickness >6000feet >10,000feet >4,000feetShale content 20% 40% 80%

Sand content 80% 60% 20%Age Miocene-recent Eocene-

OligoceneEocene-recent

Hydrocarbon

content

Very little

hydrocarbon

accumulation has been

associated with this

formation

Major

hydrocarbon

accumulations are found

in this formation

Source rock

Composition/Na

ture of deposits

Coarse grained,

poorly sorted, sub angular

to well-rounded and bears

wood fragments

Rich in micro-

fauna at the base

decreasing upward, poor

sorting and coarse grains

Presence of

Benthonic assemblages,

thin sandstone lenses

occur near the contact

with the overlying Agbada

formation

BENIN AGBADA AKATA

Environment

of Deposition

Continental

environment Transitionalenvironment MarineenvironmentThickness >6000feet >10,000feet >4,000feetShale content 20% 40% 80%Sand content 80% 60% 20%Age Miocene-

recent Eocene-Oligocene Eocene-recentHydrocarbon

content

Very little

hydrocarbon

accumulation has

been associated

with this formation

Major

hydrocarbon

accumulations are

found in this

formation

Source rock

Composition/

Nature

Coarse

grained, poorly

sorted, sub angular

to well-rounded and

bears wood

fragments

Rich in micro-

fauna at the base

decreasing upward,

poor sorting and

coarse grains

Presence of

Benthonic

assemblages, thin

sandstone lenses

occur near the

contact with theoverlying Agbada

formation


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A sedimentary rock is the second great rock class. Whereas

igneous rocks are born hot, sedimentary rocks are born cool

at the Earth's surface, mostly under water. They usually

consist of layers or strata; hence they are also called

stratified rocks. Depending on what they're made of,

sedimentary rocks fall into one of three types.

There are three type of sedimentary rock:

Clastic sedimentary rocks which are formed as a result of

eroded sediment.

Biogenic sedimentary rock which are formed from the

remains of living things.Evaporates which are formed by minerals precipitating out

of a solution.


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ARABIAN PENINSULASIMPLIFIED MAP OF THE ARABIAN PENINSULA

Geologically it lies on a tectonic plate of its own.

it consist of two distinctively different geological regions; (Western and Eastern region).

The Eastern Region is made up of mostly sedimentary limestone rock which deposited

in layers by expanding and receding ancient seas. These sedimentary layers where then

folded by tectonic pressure from east that resulted in the formation of mountains.

The large deposition of oil is found in the sedimentary folds anticline of the peninsula.

The original sediments of the peninsula are clarbonates, clastics and everporites

followed by marine sandstones and variegated shales.


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A MAP SHOWING OIL AND GAS FIELD OF THE PENISULA

PRODUCTION PROFILE OF OIL AND GAS IN THE PENINSULA

it has the largest oil field reserves in the world, especially the GHAWAR field, with

estimated remaining reserve of 70million bbls.

The arabian peninsula contains alone two third of the entire world estimated reserves.

As at 2010 saudi arabia has an estimated 260bbbl of crude reserves and 1.8mbbl ofNGL, of which 12mbbl/d is produced daily.

Also as at 2007, saudi arabia has 275trillion cubic feet of gas reserver of which 2.7 TCf

is produced daily.

Finally there ongoing and completed projects to improve the production capacity of

arabian peninsula, it is analyzed that production figures will more than double present

figures once these projects come on stream.


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North Sea Basin

North Sea

Netherlands, UK, Germany, Denmark, Norway

Major Subdivisions:

Northern / Central (80% of UK fields are under

development or on production).

Southern North Sea SNS (50% of UK fields are

under development or on production).Worldoil.com

E&P Companoes:

BG Group, BP, Chevron, Eni, ExxonMobil, Gaz de

France, Shell, Statoil

Geological History.

Pre-Devonian

Later Paleozoic Mesozoic.

Cenozoic

Tectonic Process:

Plate-margin effects (subduction).

Deformation

Almost all of the hydrocarbon fields in the southern partof the North Sea are gasfields


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NORTH SEA (FD & PROD)

FIELD DEVELOPMENT

PRODUCTION

Exploratorary of DutchGas field took

exploration offshore

leading to investigation

into the North Sea.

Formed through a period

of sequential

sedimentation , TheNorth Sea basin is

characterised by a rift

drift sequence.

Production has peaked twice but steadily declines

now. The earlier peak was during the mid 80s whentechnology and demand grew and production was

from 32 fields.

The second peak was 1999 when production was

from 136 fields.

The dip in between is due to fall in oil price and the

fitting of safety equipment post Piper Alpha.

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Group1 Geology