Fieldwork II Geology

8/17/2019 Fieldwork II Geology

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BEng Petroleum Engineering

Year 3

EART30442 – Fieldwork II

Professor: Kevin Taylor

Cathy Hollis

Fieldwork Practical Report - Northeast England Field

Trip (April 13 th to April 16 th, 2015)

Maximiano Kanda Ferraz (SwB UG) – ID 9568640

Manchester, April 2015


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EART30442 – Kevin Taylor BEng Petroleum Engineering ID 9568640Fieldwork Practical Report - Northeast England Field Trip (April 13 th to April 16 th, 2015)

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SUMMARY

1 INTRODUCTION ............................................................................................ 3

1.1 Learning Outcomes & Objectives ..................................................... 3

1.2 Locations .............................................................................................. 3

1.3 Relevance ............................................................................................. 5

2 WORK METHODS .......................................................................................... 6

2.1 Equipment ........................................................................................... 6

2.2 Procedures ........................................................................................... 6

2.3 Hazards & Safety ................................................................................. 8

3 RESULTS & DISCUSSIONS ......................................................................... 9

Staithes and Port Mulgrave Mudstones ........................................................ 9

Whitby ............................................................................................................ 13

Staithes Sandstones ....................................................................................... 16

Flamborough ................................................................................................. 19

4 CONCLUSIONS ........................................................................................... 21

5 REFERENCES ............................................................................................... 21


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1. INTRODUCTION

In this section, a brief overview of the practical is given, such as learning outcomes, objectives

(section 1.1), information on the visited areas (section 1.2) and the relevance regarding the

petroleum engineering.

1.1 Learning Outcomes & Objectives

The main objectives of the Fieldwork course were:

Observe actual geological outcrops, comparing rock lithology, identifie beds, fracture

matrix and density, traces of hydrocarbon presence, etc.

Take notes of any information found relevant, such as trends of grain size, sedimentary

structures, contacts between units and/or fossil presence, to input in the report.

Take photographs, along with drawing pictures, sketches and schematics in scale to

improve the quality of the report.

Draw conclusions on a petroleum engineering point of view, based on the topics

above, geology knowledge and the literature.

The learning outcomes are an extension of the objectives, in a way that it was possible to

obtain knowledge and experience from the field, thus felling of how a petroleum

engineer/geologist would work in a real life basis. Not only that, but the observance of health &

safety issues, correct work equipment and attention to details were important values learned. The

overall experience helped to develop skills in sedimentology and stratigraphy.

1.2 Locations

The fieldwork was realized at the Yorkshire coast, northeast of the United Kingdom. Five

specific locations were visited: Staithes, Port Mulgrave, Whitby Harbour, Scarborough and

Flamborough, as show in Figure 1 below.


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Figure 1 – Locations visited in Yorkshire Coast-UK. Source: [2]

These locations were picked, as they contain Jurassic and Cretaceous sediment outcrops,

and involved a range of depositional environments from fluvial, to deltaic and shallow/deep

marine, as well as varying lithology. Based on these differences, the areas were divided in

sections, as shown in Table 1 and Figure 2 (Source: [6]):

Table 1 – Summary of the Formations visitedLOCALITY PERIOD STAGE AGE MYA* LITHOLOGY FORMATION DETAIL

Staithes & PortMulgrave Lower Jurassic Toarcian 174-183 Mudstones

ClevelandIronstone

Whitby Middle Jurassic Aalenian/Toarcian 170-175 Sandstones Saltwick/Dogger Fluvio-deltaicStaithes Lower Jurassic Pleinsbachian 183-191 Sandstones Staithes Shallow MarineScarborough Middle Jurassic Bajocian 168-170 Variable CloughtonFlamborough Upper Cretaceous Santonian 83.6-86.3 Chalk Burham Highly Fractured

* Source: [9]


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Figure 2 - Geological map of the UK and Ireland with the marked location of the field. Source: [1]

1.3 Relevance

One of the most critical problems in the oil industry is the estimation of petrophysical

properties due to the heterogeneity of rocks, as the interpretation of subsurface seismograms and

wireline logs may not identify. This problem is more pronounced when dealing with the

permeability, which is one of the most sensitive parameters of the morphology of the rock.

So, the relevance of the field course is huge to the petroleum engineering section of

work, since studying the geology of outcrops of a basin may yield important information

regarding the subsurface through correlation of data. This could be done in the field, by makingcomparisons as which facies are more permeable, which rocks are more related to a petroleum

play, identifying a source, reservoir or seal and which area is more stable. Also, the analysis of

depositional system, grain-sorting and grain-size in clastic rocks is possible, along with linking

fractures as migration paths, permeability increasing device or neither in carbonates. The locations

studied are relevant as they are within the North Sea basin, a major basin of oil and gas fields/

reservoirs in Europe.

2. WORK METHODS


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This section describes the materials and apparatus used to perform the tasks in the field

(section 2.1), as well as the procedures utilized to successfully complete these tasks (section 2.2).

Section 2.3 describes the hazards and safety mechanisms.

2.1 Equipment

To perform the field work in a satisfactory manner, several equipment and instruments are

needed:

Notebook ([4])

Magnifying glass Measuring tape Ruler Camera Compass Clinometer Grain-Size/Sorting Reference Geology Sheet

Sedimentary Structures/Lithology Reference Geology Sheet Logging Sheet Hard Hat/Plastic Helmet Appropriate footwear

The methods of how these instruments were used are detailed in the next sections.

2.2 Procedures

Below, is a list of the procedures followed for each of the areas:

Staithes Mudstones

I. First, there was observation of the outcrop at a distance.

II. Through it, the effort was to identify main rock types, units, layers and sedimentary structures.

III. Then, a scaled-diagram was sketched, containing everything in step II.

IV. Using the camera, pictures were taken at long, medium and close range.V. Next, the outcrop was observed at close-up, using the magnifying glass and ruler.


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VI. Notes were taken of fracture preferred orientation, grain size/sorting, heterogeneities using the

geology information sheets.

VII. More notes taken regarding description and interpretation of the rock.

VIII. Consultation and wrap-up with the professors were made eventually.

IX. To conclude, the report sheet (Presented at section 3. RESULTS ) was filled, summarizing all

data.

Port Mulgrave Mudstones

*Same procedures as above.

Whitby Sandstones*Same procedures as above.

Staithes Sandstones

I. The outcrop was observed at close-up, using the magnifying glass and ruler, measuring a

vertical section of 2 meters.

II. Next, the logging sheet was filled (Presented at section 3. RESULTS ), containing the lithology

division.III. Notes were taken of diagenetic features, grain size/sorting, heterogeneities, trend, with aid of

the geology information sheets.

IV. Using the camera, pictures were taken

IV. Then, another outcrop was analyzed, only at a distance.

V. Through it, the effort was to identify main rock types, units, layers and sedimentary structures.

VI. Then, a scaled-diagram was sketched, containing everything in step V.

VII. Using the camera, pictures were taken.

VIII. Consultation and wrap-up with the professors were made eventually.


data.

Scarborough Sandstones

*Same procedures as the first 3 locations, less the close-up bit, since it was a cliff impossible to

examine at close range.


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Flamborough Carbonates

I. First, there was observation of one section of the outcrop.

II. Through it, the effort was to identify main rock types, units, fossils and sedimentary structures.

III. Using the measuring tape, fracture density was calculated (number of vertical fractures per

horizontal meter)

IV. Using the compass and clinometer, major faults and fractures preferred orientations were

defined.

V. Then, a scaled-diagram was sketched, containing everything in steps II, III and IV.

VI. Using the camera, pictures were taken at long, medium and close range.

VII. Next, another section of the outcrop was observed at long distance and close-up, (to compare

results), repeating steps I to VI.VIII. Consultation and wrap-up with the professors were made eventually.


data.

2.3 Hazards & Safety

The health & safety aspects must be followed during a work in the field. Hazards and risks

encountered are listed below, with the precautions taken to avoid any problems:

Correct handling of the materials. Avoid roadside exposure, as it provides risk from traffic. Taking care when working on top of steep slopes and terraces, watching out for drop-offs. Avoid work near cliffs or overhanging rocks. Wearing a hard hat all the time in the field. Wear appropriate footwear all the time in the field, as the environments are sandy, stony

and slippery.

Check for incoming tides and avoid wondering off to not be cut-off.


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3. RESULTS & DISCUSSIONS

Petroleum Engineering EART30442 Name: Maximiano Kanda Ferraz

Yorkshire Coast Field Course 2015 Student Number: 9568640

Staithes and Port Mulgrave Mudstones

Exercise 1: Cleveland Ironstone Formation. Go up to the cliff and examine closely the rock types. Makenotes on the lithology, major contacts between units and any sedimentary structures, fossil content,diagenetic features. Take care not to go under dangerous sections and always wear your hard hat.Interpret the environment of deposition and reservoir properties.

Description: UNIT A UNIT B

COLOR: Grey (White trace) Beige COMPOSITION: Mud/Clay Iron GRAIN-SIZE: Clastic Silt - GRAIN-SORTING: - - TRENDING: Upward Fining - SEDIMENTARY STRUCTURES: Parallel Lamination - HARDNESS: Soft Sheets Harder than A ICHNOFAUNA: Yes Yes CEMENTATION: No Yes FRACTURES: Yes Yes HYDROCARBON/ORGANIC MATTER STAIN: Yes No LITHOLOGY: Mudstone Ironstone HETEROGENEITIES: Beds of Sand-rich muds Carbonate Concretions DIAGENETIC FEATURES: - Oolitic DEPOSITIONAL ENVIRONMENT: Marine Marine

Interpretation:

Vertical fractures may be due to outcrop uplift, which resulted in pressure relief and appearanceof fractures. This has to be taken in account, since in the original deposition (if the system werelocated in the subsurface); the lack of faults may yield different interpretations concerninganalogues with source rock quality.

The Ichnofauna present can support the evidence of rock-age (Jurassic) and depositionalenvironments, as Belemnites (squid-like animals) were found, an indication of near-shore to mid-shelf oceans (Source: [5]), therefore, a marine environment.

The different Units are due to cycles of sea-level. Unit A (mudstone) was deposited in deep sea-level and Unit B (ironstone) in low sea-level.

Ironstone was present in 2 thick and 5 thin observable layers. Figure 3 shows these layers ofironstone marked with arrows. Fig. 3 also shows fractures found in the mudstones:


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Figure 3 – a) Layers of ironstone (Unit B) among mudstone (Unit A). b) Vertical Fractures

Exercise 2: Make a summary sketch log of the succession that you observe, noting any cycles present, thescale of these cycles and the nature of these cycles. What are the implications of these cycles on thereservoir properties and rock mechanics if this were a shale gas reservoir?

If this were a shale gas reservoir, hypothetically reaching kerogen maturity in the subsurface(since the coastal rock are immature), the ironstone layers would serve as sealing mechanism, anddissipators of artificially created fractures. The presence of vertical fractures could point to the preferredorientation of the fractures when the hydraulic fracking production method were in effect. The fracking is

necessary because shale, although friable and with fair porosity (5-10%), has extremely low permeability(around µD) and pore size in nanometers. Fractures would form vertically, as overburden pressure (δ 1) isthe principal stress.

The colorization indicates organic matter content, with light grey layers being around 1,5-2% TOC(total organic carbon) and darker layers, more. So, the ‘goldlock’ spot would be in the darker, morefractured layer. A gamma ray log and neutron/density logs after a well is drilled may help identify gasareas, with the former indicating clay-rich, organic-rich layers and the latter indicating gas presence whenthe logs cross and separate. Vertical permeability would increase with the hidro-frac, so, a horizontal wellplaced within the cycles could yield a better production rate than a vertical well that goes through all the

cycles (since there is reservoir compartmentalization) .


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Figure 4 – Sketch log of Exercise 2, showing the cycles of mudstone (A) and ironstone (B)

Exercise 3: Jet Rock, Port Mulgrave

Go up to the cliff and examine closely the rock types. Make notes on the lithology, any sedimentarystructures, fossil content and diagenetic features. Take care not to go under dangerous sections andalways wear your hard hat. ? What do you think the potential is for this rock to be a source rock or a shale

reservoir?


COLOR: Grey Beige COMPOSITION: Mud/Clay Iron GRAIN-SIZE: Clastic Silt - GRAIN-SORTING: - - TRENDING: - - SEDIMENTARY STRUCTURES: Parallel Lamination -

HARDNESS: Soft Sheets Harder than A ICHNOFAUNA: Yes Yes CEMENTATION: No Yes FRACTURES: Yes No HYDROCARBON/ORGANIC MATTER STAIN: Yes No LITHOLOGY: Mudstone Ironstone HETEROGENEITIES: Beds of Sand-rich muds Carbonate Concretions DIAGENETIC FEATURES: - Oolitic DEPOSITIONAL ENVIRONMENT: Marine Marine

Interpretation:


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Similar to the Cleveland Formation, but with the units being more homogeneous (harder toidentify) and with more fractures and faults (fractures with movement/separation) noted.

The Ichnofauna present can support the evidence of rock-age (Jurassic) and depositionalenvironments, Ammonite (cephalopod-molluscs-like animals) was found in the mudstone sectionon the floor of the outcrop, an indication of near-shore to mid-shelf oceans (Source: [5]),therefore, a marine environment.

Ironstone was present in brittled pebbles/boulders among the layers of mudstone. Thecementation of the ironstone occurred in a reducing environment. Some of these boulders wereorange colored in the edges, being a result of oxidation due to water action (iron sulfide) after theuplift.

The formation is quite ductile, explaining the diverse fractures and the hardness for identifyingclear visible lithology units.

The different Units are due to cycles of sea-level. Unit A (mudstone) being deposited in deep sea-

level and Unit B (ironstone) in low sea-level. The difference with the Cleveland formation may betha t the environment was more agitated, don’t allowing the layers of to deposit plainly, resultingin a more complicated lithofacies division.

The colorization of mudstone indicates organic matter content, with dark grey layers beingaround 4% TOC (total organic carbon), a good number for a potential source rock (better than theStaithes mudstone). The marine depositional environment yields a Type II kerogen, which maygenerate good quality liquid hydrocarbons. For a shale reservoir, the rock is worse than the Staithesmudstones, as there are more heterogeneities, incrustations and compartmentalization that maycause instability in the hydraulic fracking.

Figure 5 – a) Fossil of Ammonite b) Photo showing iron incrustations, fractures and oxidation


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Petroleum Engineering EART30442 Name: Maximiano Kanda Ferraz


WhitbyExercise 1: Go up to the cliff and examine closely the rock types. Make notes on the reservoir lithology,major contacts between units and any sedimentary structures, fossil content, diagenetic features. Takecare not to go under dangerous sections and always wear your hard hat. Interpret the environment ofdeposition and reservoir properties. West Cliff


COLOR: Light Brown Dark Brown COMPOSITION: Sand Sand GRAIN-SIZE: Coarse Fine GRAIN-SORTING: Well Sorted Medium Sorted TRENDING: Upward fining - SEDIMENTARY STRUCTURES: Cross-bed stratification - HARDNESS: - - ICHNOFAUNA: No No CEMENTATION: No No FRACTURES: No No HYDROCARBON/ORGANIC MATTER STAIN: No No

LITHOLOGY: Sandstone Sandstone HETEROGENEITIES: - Clay lamination/Iron DIAGENETIC FEATURES: - - DEPOSITIONAL ENVIRONMENT: Fluvio-Deltaic Fluvio-Deltaic

Interpretation:

The depositional environment is a truncation (Fluvial/Deltaic/Coastal), with input of terrestrialand marine sediments and organisms (although no fossil was found).

Sandstones with black areas show erosion and oxidation of iron sediments.

There is a 20º dip in the structural stratigraphy, showed in (Figure 6). A sedimentary structure noted was cross-bedding stratification (Figure7).


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Figure 6 – Dip observed in Whitby Sandstone

Figure 7 – Cross-bedding in Whitby Sandstone


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Exercise 2: Sketch (in landscape format) from a distance, the cliff section, noting the main lithological units (facies),

nature of contacts, faults and major fractures and architecture of the system .

Figure 8 – Sketch of Whitby Cliffs formations

Exercise 3: Reservoir Distribution

Discuss the reservoir properties, lateral connectivity and distribution of reservoir units, and implicationsfor a subsurface development. Is there any information you could use to predict lateral extent of thereservoir?

The coarser sandstone is a bad quality reservoir, as there is poor grain selection, morecementation and not much lateral connectivity.

The finer sandstone is a better quality reservoir, with more porosity and permeability. As there iscompaction of the sand, the favorable production direction is horizontal (Kh>Kv).


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Petroleum Geoscience EART30442 Name: Maximiano Kanda Ferraz


Staithes Sandstone

Exercise 1: On the log paper provided, log the section from the beach to about 2 m up the cliff. Take careof the cliff and falling rocks. Wear you hard hat. Note the lithology, grain size, sedimentary structure,ichnofauna, surface (erosional or gradational, and cementation. Extra marks allotted for good notes andobservations. Divide the section into a number of Facies / Facies Associations which have similarproperties

Figure 9 – Logging of 2 meters section Staithes Sandstone


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Exercise 2: Sketch some characteristic sedimentary structures you have observed.

Figure 10 – Sedimentary Structures found in Staithes Sandstone

What is the Depositional Environment? Shallow Marine

Exercise 3: Discuss the reservoir properties of the Staithes Sandstone. Note porosity/permeability,heterogeneity, vertical versus horizontal flow properties. Use observations from both sides of theharbour.

The Staithes sandstone Formation is a good reservoir as it is composed mainly (as seen in thelogged section) by well sorted medium-grained sand, without huge amounts of clay particles toreduce permeability and without calcite cementation to reduce porosity. The ironstone layer above itprovides a good seal and trap (this can be better seen on the right side of the harbor) for thehydrocarbon.

The preferred flow orientation would be horizontally, as parallel laminations were found. So, avertical well drilled in the formation would take advantage of that. A certain dip (12º) in the left sidecould be good in a way that the lighter oil and gas would accumulate at the top of the reservoir


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easier, and the water-oil contact would be located in a higher depth. This situation allows theproposed vertical well proposed above to continue producing longer.

The left side of the harbor has better quality reservoir rock material. The right side of the harbor

was observed at a distance, but it was possible to note that the sandstone was grey in color,indicating shaly beds. It was also possible to see sandstones with black areas that show erosion andoxidation of iron sediments. Heterogeneities were found, and seen in the logged section, with a~80cm extent pinch out shell inside the sandstone. The depositional environment is a shallow marineambient, the same as the Cleveland Ironstone Formation, and confirmed with the fossils found. Figure11 is a sketch of the both sides of the harbor.

Figure 11 – Drawing of the Staithes Sandstone Fm. and others in the Staithes Harbour


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Petroleum Geoscience EART30442 Name: Maximiano Kanda Ferraz


Flamborough Head

Exercise 1: Go up to the cliff and examine closely the rock types. Make notes on the lithology,and anysedimentary structures, fossil content, diagenetic features. Take care not to go under dangerous sectionsand always wear your hard hat. Interpret the environment of deposition.

Description:

COLOR: White COMPOSITION: Calcite SKELETAL ASSEMBLAGES: Stylolites

CEMENTATION: Yes FRACTURES: Yes HYDROCARBON/ORGANIC MATTER STAIN: No LITHOLOGY: Chalk HETEROGENEITIES: Faults DIAGENETIC FEATURES: Cementation DEPOSITIONAL ENVIRONMENT: Calm waters (marine shelf)

Interpretation:

Like any carbonate, the deposition of chalk took place in medium-deep calm water, in a non-tropical environment and, with the collision of the African and Eurasian tectonic plates, thedeposits were raised to the surface.

Horizontal Stylolites (removal of mineral due to pressure dissolution) were identified. Thrustfaults are also present, both result of these movements. Figure 12 show these.

Figure 12 – a) Stylolites b) Major Fault in the Flamborough Chalk


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Exercise 2: In terms of the petroleum system, what potential could this lithology have? What are itscharacteristics that would make it a good reservoir or a seal?

The chalk is a very fine-grained shelly limestones, and it can take places of a reservoir or sealing

rock in a petroleum play system, depending on how faulty or fractured it is. As a carbonate, the chalk hasa complex pore system, and the amount of microporosity may affect how stable the rock is to attainoverburden pressure. More cracks make the rock compact and act as a seal.

Chalk would behave as a good reservoir only with flow paths through uncemented fractures.“Fractures are naturally occurring planar discontinuities that forms as a result of deformation” (Nelson,2001). The fractures create permeability architecture that cross-cuts the matrix pore system. Also, morestiff porosity (moldic, vugular, interparticle) makes the rock more resistant to compaction, stable andcould increase its porosity for it to store economical amounts of hydrocarbon.Exercise 3: Fractures: Examine closely the fracture network. Draw how the fractures are distributed.What implications would this have in the subsurface for productivity, and how would this determine your

development strategy?The chalk analyzed would be a Type 3 carbonate reservoir (low matrix permeability and good

fracture permeability). The fracture density is around 5-7/meter and increases when near faults (10), dueto stress increase. The dip of the stratigraphy also increases for the same reason. Thinner beds generatemore fractures, as they suffer relatively higher amounts of stress than thicker beds, which dissipate thestrain in wider areas. Figure 13 is a drawing of the fractures distribution in the formation.

To determine where to drill the well, it would be necessary to run a wireline borehole image log,as it is good to characterize the matrix/distribution of fractures. Seismic would not show much contrastbetween the formation and it does not have the resolution to identify smaller elements in the system. Adeviated well would be better than a vertical well to optimize production, since the main fracture/flow

orientation is NW/SE, with the main big faults having 270 0W, 260 0W and 315 0NW orientation.The development strategy has to take in account that highly fractured reservoirs have a higher

flow area, but can lose pressure quickly. To calculate this, before beginning full production, it would beinteresting to run a pressure test (open flow for a period of time, then closing the production to observehow the pressure recuperates inside the reservoir). Laboratory analysis of core would provide informationabout the pore system and wettability. The ideal method of production is a low flow rate deviated well,near a fault, with constant downhole pressure monitorance and an elevation technique, such as gas lift.

Figure 13 – Formation sketch, with Fracture and fault network


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4. CONCLUSIONS

The reported practical wok aimed to characterize the geology formations described. Like any

practical, is subject to measurement errors, errors inherent in equipment and even human error.

However, it was obtained satisfactory, suitable and consistent results with the literature and

presented theory.

A way to improve the report would be to add more detailed comparisons between what was

seen and the scientific papers published regarding the Yorkshire coast. In an eventual

circumstance to redo the fieldwork, it would be interesting to obtain samples for further laboratory

analysis, as well as collect more data like logging outcrop sections outside of Whitby.

5. REFERENCES

[1] British Geological Survey . IPR/123-16CT . Available at: http://www.thegeologytrusts.org (Accessed:22/04/2015).

[2] Google Maps. Available at http://www.maps.google.co.uk/ (Accessed: 22/04/2015).

[3] Hollis, Cathy. 2015. Formation Evaluation Class Notes.

[4] Rite in the Rain, 2012. Geological Field Book Nº540F.

[5] Shimmin, Joe, 2008. An introduction to Belemnites, An introduction to Ammonites . . Availableat http://www.ukfossils.co.uk/guides/ (Accessed: 26/04/2015).

[6] Taylor, Kevin, 2015. Fieldwork II Class Notes .

[7] The University of Manchester, 2015. Petroleum Engineering Laboratory .

[8] Thomas, J. E, 2010. Fundamentos de Engenharia do Petróleo . Rio de Janeiro, Interciência.

[9] Walker, J.D., Geissman et al. 2012. Geologic Time Scale v. 4.0 . The Geological Society ofAmerica.

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Fieldwork II Geology