summer project-university of manchester

8/17/2019 Summer Project-University of Manchester

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BEng Petroleum Engineering

Professors: Dr. Stefan Schroeder

Dr. Cathy Hollis

Science without Borders Summer Project

Practical Report – Geological Core Description

Maximiano Kanda Ferraz (SwB UG) – ID 9568640

Manchester, August 2015


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Maximiano Kanda Ferraz – BEng Petroleum Engineering ID 9568640Science without Borders Summer Project Practical Report

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SUMMARY

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

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

1.2 Information about the Cores ........................................................... 4

1.3

Relevance ......................................................................................... 6

2 WORK METHODS ...................................................................................... 7

2.1 Equipment ....................................................................................... 7

2.2 Procedures ....................................................................................... 7

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

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

2.1 Carbonate Section ............................................................................ 9

2.2 Transition and Clastic Sections ..................................................... 15

2.3 Petroleum System Analogue .......................................................... 21

4 CONCLUSIONS ....................................................................................... 23

5 REFERENCES ........................................................................................... 24


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1. INTRODUCTION

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

(next section), information on the cores sorted and described (section 1.2) and the relevance

regarding the petroleum engineering work (section 1.3).

The project was divided in two parts. The first one was to sort out the core material received at

The University of Manchester (detailed in section 2. Work Methods). The second part of the

project was the actual core description, and the focus of the present report (section 3. Results and

Discussions).

1.1 Learning Outcomes & Objectives

The main objectives of this summer placement were:

Observe actual geological cores, comparing rock lithology, identifying beds,

lithofacies and depositional packages. Take notes of any information found relevant, such as trends of grain size, sedimentary

structures, contacts between units and fossil presence, to input in the logging sheets

(detailed in section 2. Work Methods).

Provide an accurate description of the selected cores, which will be part of the

University’s teaching library.

Develop an analogy of the cores (which came from a quarry), to a petroleum

play/prospect point of view, based on the topics above, geology knowledge and

literature.

The learning outcomes, as expected in the projects guideline (Source: [6], Schroeder,

2015) are “Make appropriate observations and measurements in the laboratory and/or collate

information from published sources pertinent to stated aims and objectives”, employing technical

knowledge and comparing the results with the literature. The overall experience helped to develop

skills in geological core evaluation, sedimentology and stratigraphy.


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1.2 Information about the Cores

The cores were collected from the Ketton and Thistleton quarries, with its approximate location

inside the United Kingdom, between Nottingham and Cambridge, shown in Figure 1 below.

Figure 1 – Locations from where the cores were extracted (Source: [3], Google Maps)

Figure 2 is an illustrated geological map of the UK, by the British Geological Survey, with

the marked square being the location of Ketton and Thistleton. It is possible to observe that the

main depositional packages are from the Jurassic period (around 170 million years ago. Source:

[9]).


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

Geological Survey)

Table 1 is a summary of all the cores that were sorted out to compose the teaching library

of The University of Manchester, detailing the core name, number of boxes (that contain around 3

meters of core each, 1 meter for each division inside of it), and the top/bottom depths of which the

core was collected. The section described was from core ER 01/07, from depth 8.10 to 18.10 (10

meters), which covers box 3, box 4, box 5 and part of box 6 of the core.


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Table 1 – Summary of the Cores Sorted

Ketton

Borehole Number of Boxes Top (meters) Bottom (meters)

ER 01/07 14 1,00 44,60

16W 6 0,75 19,50

01-07 6 0,60 17,75

28 8 1,50 24,80

ER 02/07 13 0,00 42,50

14 7 0,00 26,90

21 8 1,20 21,90

2W-07 3 1,40 10,25

18 14 2,20 51,00

Thistleton

Borehole Number of Boxes Top (meters) Bottom (meters)

01 5 0,00 15,00

1.3 Relevance

The relevance of the core description is huge to the petroleum engineering section of

work, since studying the rocks of a basin may yield important information regarding the

subsurface through correlation of data.

Also, the description of this section of the core can be added to the teaching core library

as an interpretation made with focus on a petroleum play. Also of essence were the organic matter

content in shale and the transition of rock types (carbonate to clastic), indicating a change in the

depositional system.


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2. WORK METHODS

This section describes the materials and apparatus used to perform the tasks (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

Gloves

Magnifying glass

Ruler

Camera

Notebook

Grain-Size/Sorting Reference Geology Sheet (Source: [5], Geological Field Book)

Sedimentary Structures/Lithology Reference Geology Sheet (Source: [4], Hollis, 2015)

Logging Sheets

Solution of hydrochloric acid (HCl) Water

2.2 Procedures

The first part was to sort out the core material received at The University of

Manchester from wooden boxes into proper geological core trays, improving upon the

cores state (cleaning dust and discarding small rock pieces), correcting eventual errorson the cores information and further labeling the trays with the correct top/bottom

depths.

The second part was the core interpretation. After a briefing done by the supervisor, the

section of core ER01/07 was selected and the interpretation was carried out using the

majority of the equipment cited in Section 2.1 (magnifying glass, ruler, reference

sheets and etc.). Using the camera, pictures were taken (shown in the next section).


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Sometimes, to better observe the core features, a solution of hydrochloric acid was

used to test the presence of carbonates (which reacts, if it is present). Water was also

used to test porosity and better observe fossils/bioturbation.

OBS.: A post-graduate student, Mr. Frederic was consulted, helping on the first day of

the core description.

2.3 Hazards & Safety

The risks associated with the work, with precautions taken to avoid any problems, were:

The correct handling of the materials to not cause damage in university property or hurt

anyone. With focus on:

o Correct handling of the core boxes, being the wooden box or the definitive plastic

tray.

o Gloves used to clean the dust of the cores.

o Care with the use of the HCl solution to not cause marks to the core or hurt

anyone.


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3. RESULTS & DISCUSSIONS

The description of core ER01/07 took place between the depths of 8.10 meters to 18.10 meters

(Boxes 3, 4, 5 and 6. The main reason of choice of this interval of core was the presence of

different rock types, yielding different depositional packages and numerous lithofacies.

In summary, from bottom to top (older to newer rocks), it was observed a succession of

carbonate-type rocks, limestone of different classification in the ‘Dunham Classification’ (Source:

[2], Dunham, 1962), followed by a transition zone to an upward fining clastic section with traces

of iron. Finally, going up to the top of the core (more recent in the geological time scale), a shale

section with varying amount of organic matter content. Each section is detailed below.

3.1 Carbonate Section

Using the work methods described at Section 2 of the present report, various lithofacies were

identified. The methods to identify and describe this carbonate package were: visual observation

(lack of lamination, ooid presence), texture, acid testing (reacting with acid), check for fossil

presence and type, grain and porosity type, saturation, cementation, hardness, etc. Tables were

made for each lithofacie to sum up its characteristics.

Figure 3 shows box 6, and the plug that was taken at 18.0 meters. The base of the arrow at the

right indicates where the description began, at 18.10 meters. Figure 4 shows box 5, which

comprises 14.3 to 17.4 meters. Plugs nº 26, 27, 28 and 29 were taken at 17.0, 16.0, 15.0 and 14.35

meters respectively. Figure 5 show these plugs (with the exception of plug nº 29, present in Figure

6) in a closer view.

The section from 17.4 to 18.1 meters (top of box 6, Figure 3) comprises a single lithofacie (A).

Lithofacie B extends from 15.1 to 17.4 meters, with some core gaps in between (Figure 4). Table

2 details the lithofacies A and B (referenced as Units A and B).


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Figure 3 – Box 6 (left) and plug nº 25 (right)

Figure 4 – Box 5 (17.40 to 14.30 meters)


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Figure 5 – Plugs nº 26, 27 and 28

Table 2 – Summary of Lithofacies A and B

Characteristic UNIT A UNIT B

COLOR: Light Beige Beige

COMPOSITION: Calcite Calcite

TRENDING: Porosity decreases upward -

HARDNESS: More consolidated Some Foliation

ICHNOFAUNA: No Yes (Oyster Bioclact, Figure 6)

CEMENTATION: Yes Yes

FRACTURES: Yes No

HYDROCARBON/ORGANIC MATTER: No No

LITHOLOGY: Limestone (Grainstone) Limestone (Packstone)

HETEROGENEITIES: Visual Vertical Fracture -

DIAGENETIC FEATURES: Oolitic Oolitic

DEPOSITIONAL ENVIRONMENT: Marine Marine

Lithofacie A repeats between 14.4 to 14.7 meters. Lithofacies C and D are also present in

Box 5, with the former present between 14.7-15.1 meters and the latter above 14.4 (where plug 29

is located, Figure 6). Figure 6 shows fossils, with the first photograph being from lithofacie B.

Table 3 compares units C and D.


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Figure 6 – Fossil found at and Plug nº 29

Table 3 – Summary of Lithofacies C and D

Characteristic UNIT C UNIT D

COLOR: Beige Dark Beige

COMPOSITION: Calcite Calcite

TRENDING: Porosity increases upward -

HARDNESS: More consolidated Some Foliation

ICHNOFAUNA: No Yes (See Figure 6)

CEMENTATION: Yes Yes

FRACTURES: Yes No

HYDROCARBON/ORGANIC MATTER: No NoLITHOLOGY: Limestone (Grainstone) Limestone (Packstone)

HETEROGENEITIES: Vugs (Secondary Porosity) Friable/Very Brittle

DIAGENETIC FEATURES: Oolitic Oolitic

DEPOSITIONAL ENVIRONMENT: Marine Marine

Interpretation:

The vertical fracture observed on Unit A may have appeared due to core uplift, which

resulted in pressure relief and appearance of fractures. This has to be taken in account, as


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the lack of fractures on carbonates may yield different interpretations concerning

analogues with reservoir rock quality.

The Ichnofauna present can support the evidence of rock-age (Jurassic) and depositional

environments, as oysters were found, an indication of near-shore to mid-shelf oceans

therefore, a marine environment. Laminated sections to further investigate these fossils

may date the rock better.

Like any carbonate, the deposition of chalk took place in medium-deep calm water, in a

non-tropical environment, with sunlight and sufficient mineral input.

The different Units may be due to cycles of sea-level, as units B and D have some mud,

putting them in the Packstone classification. Units A and C could have been deposited in

calmer waters, leading to less organic matter input and less mud sediments (more

ooids/carbonate minerals)

The porosity in carbonates depends a lot upon diagenetic processes and secondary porosity

(vuggy, moldic, intra/interparticle pores). Unit C and D have some of this features, as vugswere found.

Figure 7 shows the Logging Sheet 1, made at a 1:20 scale, which covers the carbonate

section (14.1-18.1 meters).


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Figure 7 – Logging Sheet 1 (14.1-18.1 meters)


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3.2 Transition and Clastic Sections

Moving up the core and closer to the surface, a clastic section is reached. The methods to

identify and describe the transition (half of box 4) to the clastic package (boxes 3 and 4) were

mainly visual observation (lamination), texture, acid testing (not reacting with acid), grain size,

sorting, porosity type, saturation, hardness, organic matter content, sedimentary structures, etc.

The shale colorization indicating organic matter content, with light grey layers being around 1.5-

2% TOC (total organic carbon) and darker layers, more. The classification in the tables below of

poor, medium and rich organic matter content refers to less than 1.5% TOC, around 2% and above

2-3% respectively.

Figure 8 shows boxes 3 and 4. Figure 9 is a closer photograph of the iron presence, oxidation

and iron concretions observed. Table 4 below compares lithofacies H and I, with the latter present

between 13.2 to 14.1 meters and the former present between 12.9 to 13.2 meters (first half of box

4).

Table 4 – Summary of Lithofacies H and ICharacteristic UNIT H UNIT I

COLOR: Brown/Orange Light Grey

COMPOSITION: Silt, Iron, Sand Silt, Iron

GRAIN-SIZE: Very Fine Sand (~0.07 mm) Silt (~0.02 mm)

GRAIN-SORTING: Poor Good

TRENDING: Upward fining Upward fining

HARDNESS: Sandy, Friable Stable

SEDIMENTARY STRUCTURES: No No

CEMENTATION: No Yes

FRACTURES: No No

HYDROCARBON/ORGANIC MATTER: No No

LITHOLOGY: Silty Sandstone Siltstone

HETEROGENEITIES: Iron Concretions Some Iron present

DIAGENETIC FEATURES: - -

DEPOSITIONAL ENVIRONMENT: Fluvio-Deltaic Fluvio-Deltaic


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Figure 8 – Box 3 (right) and 4 (left) of core ER01/07 (8.1 to 14.1 meters)


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Figure 9 – Section of 13.7 meters, showing iron concretions in silty sandstone

Table 5 describes the shale/mudstones Lithofacies E (8.1 to 8.8 and 9.3 to 10.8 meters), F (10.8 to

11.4 and 11.9 to 12.4 meters), G (11.4 to 11.9 and 12.4 to 12.9 meters) and J (8.8 to 9.3 meters).

Table 5 – Summary of Lithofacies E, F and G

Characteristic UNIT E UNIT F UNIT G UNIT J

COLOR: Light Grey Dark Grey Grey Light Grey

COMPOSITION: Mud Mud Mud, Iron Mud, Iron

GRAIN-SIZE: Clay (0.01mm) Clay (0.01mm) Clay (0.01mm) Clay (0.01mm)

HARDNESS: Sheets Sheets Sheets Sheets

SEDIMENTARY STRUCTURES: No No No No

CEMENTATION: Calcite No No Calcite

FRACTURES: No No No No

ORGANIC MATTER: Medium Rich Medium Poor

LITHOLOGY: Shale Shale Shale Shale

HETEROGENEITIES: Carbonate Mud No Iron Some Iron Carbonate Mud

DIAGENETIC FEATURES: - - - -

DEPOSITION ENVIRONMENTMedium-Deep

WatersDeep Waters

Medium-Deep

Waters

Medium-Deep

Waters


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Interpretation:

The lithofacies differs in matters of organic matter content, presence or not of iron and

presence or not of carbonate cement.

This may occur due to cycles of sea-level. Unit F being deposited in deep sea-level

(anoxic, with no input of iron or carbonates) and Units E, G, J in low sea-level, as the

environment was more agitated, don’t allowing the layers of to deposit plainly, resulting in

a more complicated lithofacies division.

Ironstone was present in small concretions in the transition zone and among the layers of

mudstone. Ironstone was cemented instead of calcite maybe because of the depositional

environment sudden change from marine to shallow water/deltaic one. The cementation of

the ironstone occurred in a reducing environment, the orange color in the edges, being a

result of oxidation due to water action (iron sulfide).

The marine depositional environment yields a Type II kerogen, which may generate good

quality liquid hydrocarbons.

Shales with orange areas show erosion and oxidation of iron sediments.

Figures 10 and 11 below contain the Logging Sheets 2 and 3, which comprise this section.


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Figure 10 – Logging Sheet 2 (10.1 – 14.1 meters)


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Figure 11 – Logging Sheet 3 (8.1 - 10.1 meters)


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3.3 Petroleum System Analogue

As a petroleum engineering student, an interesting job is to make an analogy of the Ketton

quarry core to a real petroleum system. Figure 12 is a sketch of a onshore vertical well drilled at

the position the core was retrieved. Showing the real depths of the would-be reservoir (limestone

section), the shale bedding acting as a sealing rock above it and the middle layer being the silty

sandstone/siltstone. A source rock could not be defined, but it had to be located below the

limestone.

Figure 12 – Petroleum System Analogue


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“Due to the brittle nature of carbonate rocks, fractures are more prevalent than in clastics.

These fracture systems act as conduits for fluid flow and can considerably enhance hydrocarbon

production in low- porosity carbonate rocks or tight gas sands” (Source: [10], Xu & Payne, 2009).

Although fractures were not observed, the limestone analyzed could be a good carbonate reservoir

as it has good matrix permeability. Also, more stiff porosity (moldic, vugular, interparticle) makes

the rock more resistant to compaction, stable and could increase its porosity for it to store

economical amounts of hydrocarbon.

To determine where to drill the well, it would be necessary to run a wireline borehole log, to

better define lithology, fluid presence and permeability. Seismic would not show much, as it does

not have the resolution to identify smaller elements in the system. A vertical well would fulfill the

task of producing oil.

The development strategy has to take in account that the reservoir may be drained quickly

if there is not much lateral connectivity. To calculate this, before beginning full production, it

would be interesting to run a pressure test (open flow for a period of time, then closing the

production to observe how the pressure recuperates inside the reservoir).

The silty sandstone makes a bad quality reservoir, as grain sorting is bad, reducing its permeability and porosity.

In the shale section, if testing for an shale gas reservoir, hypothetically reaching kerogen

maturity in the subsurface (since the shale is immature), the section above the shale should act as

trapping mechanisms. A gamma ray log and neutron/density logs after a well is drilled may help

identify gas areas, with the former indicating clay-rich, organic-rich layers and the latter indicating

gas presence when the logs cross and separate. However, the presence of calcite cementation and

iron could make oil/gas harder to extract, even with hydro-fracking techniques, as that could be

flow barriers.


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4. CONCLUSIONS

The reported practical work aimed to describe a section of the core Ketton ER01/07, extracted

from the Ketton quarry. Like any practical, is subject to measurement errors, errors inherent in

equipment and even human error. However, it was obtained suitable and consistent results. The

section described could relate to a petroleum system better than expected, and the section,

although it had some gaps, was in satisfactory state for analysis.

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

seen and the scientific papers regarding the cores extracted from these Quarries, to confirm the

interpretation. Some plugs were taken that helped interpret the cross-sectional area of the core.

Some cores (not the one analyzed) were submitted to cuts in half, for the same reason.

Nonetheless, it would be interesting to obtain some samples for further laboratory analysis,

such as plugs to perform porosity and permeability measurements, or even laminated sections to

observe fossil types on carbonate sections and grain size, sorting, roundness on the clastic section

(micrograph).


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5. REFERENCES

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

03/08/2015).

[2] Dunham, R. J. (1962). Classification of carbonate rocks according to depositional textures.

AAPG. 108-121.

[3] Google Maps. Available at http://www.maps.google.co.uk/ (Accessed: 03/08/2015).

[4] Hollis, Cathy (2015). Formation Evaluation Class Notes. 46pp.

[5] Rite in the Rain (2012). Geological Field Book Nº540F. 160pp.

[6] Schroeder, Stefan (2015). SwB Projects Guidelines. 3pp.

[7] The University of Manchester (2015). Petroleum Engineering Laboratory. 20pp.

[8] Thomas, J. E (2001). Fundamentos de Engenharia do Petróleo. Interciência, Rio de Janeiro.

272pp.

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

America.

[10] Xu, S., & Payne, M. A. (2009). Modeling elastic properties in carbonate rocks. The Leading

Edge, 28(1), 66-74.

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