oil shale and shale gas (abdallah)

Unconventional Oil Shale & Shale Gas

By

Abdallah Khames Ibrahim Geology Department, Faculty of Science, Alexandria University

Supervised by

Prof.Dr.Magdi Elghamri Professor of petroleum Geology

2015

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Acknowledgement

After thanking ALLAH, thanks for every one helped me to finish my

graduation project

Especially:

Professors who supported and supervised me at the expense of their precious time;

Dr. Magdi Elghamri (professor of petroleum Geology) and Prof. Dr. Mohamed

Abdel-Aziz Younes (professor of petroleum Geology), also professor who helped me

in my project; Prof. Dr. Tharwat Ahmed Abdel Fattah (professor of Geophysics)

and a very special thanks for all doctors in the department of geology who helped me

to be a real geologist.

Abdallah khames

abdallah [email protected]

Unconventional oil shale and shale gas 2015

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Contents

Chapter page no.

Chapter I: introduction of Oil shale …………………………….......... 5

1.1 Definition of oil shale ……………………….………………………… 11

1.2 Origin of oil shale ……………………………………………………... 12

1.3 Origin of Organic Matter ………………………………………….….. 12

1.4 Thermal Maturity of Organic Matter ……….……………………........ 14

1.5 Classification of oil shale ....………………………………………..…. 14

1.6 Composition and properties ………………………………………........ 21

1.6.1 Mineral Components ………………………………………... 21 Chapter II: Exploration of oil shale ……………………..…………….. 24

2.1 Geological investigation ……………………………………………..... 25

2.2 GEOPHYSICAL investigation …........................................................... 25

2.2.1 Seismic characteristics of oil shale………………………...… 27

2.2.2 Log characteristics of oil shale……………………………..... 29

2.2.3 Single-well evaluation of oil shale………………………...… 31

2.2.4 Analysis of log-seismic multi-attributes………………...…… 35

2.2.5 Seismic quantitative evaluation of oil shale…………………. 37

2.2.5.1 The log-constrained seismic inversion………………........ 37

2.2.5.2 Prediction of the inversion volume of TOC ……………... 38

2.2.5.3 Prediction of the inversion volume of oil yield …………. 40

2.3 Geochemical investigation ………………………………..…………... 45

2.3.1 Rock Eval pyrolysis ……………………………………….... 46


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2.3.1 Fischer Assay…………………………………………....…… 47

2.3.3 Hydrous Pyrolysis Oil Yields ……………………………….. 48

Chapter III: Extraction of oil shale ……………………………………. 49

3.1 Ex-Situ Processing ……………………………………...…………….… 49

3.2 Ex situ technologies…………………………………………………….. 52

3.2.1 Internal combustion…………………………………………… 53

3.2.2 Hot recycled solids……………………………………………. 54

3.2.3 Conduction through a wall…………………………………..... 56

3.3 In-situ processing……………………………………………………….. 56

3.4 In-Situ Technologies……………………………………………………. 57

3.4.1 Shell In Situ Conversion Process (ICP)……………….. 57

3.4.2 American shale oil process………………………..…… 58

Chapter IV: Evaluation of Oil-Shale Resources, production….... 59

4.1 global oil shale resources…………………………………….......……. 59

4.2 global oil shale production ………………………………….……….... 60

4.3 oil shale in Egypt …………………………………….………………... 62

Chapter V: Introduction of shale gas...................................................... 71

5.1 Different between shale gas and natural gas ……………………...…… 72

5.2 Types of shale gas ……………………………..………..…….………... 73

5.3 Basic Characteristics of Shale Gas ……………………………………... 74

5.4 Characteristics of Shale reservoir ………………………………………. 76


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Chapter VI: Shale gas exploration……………………………………… 77

6.1 Geological investigation…………………………………………….... 77

6.2 RESERVOIR EVALUATION TECHNIQUE ………………………. 78

6.2.1 Seismic characteristics of oil shale…………..……………… 79

6.2.2 Log characteristics of oil shale…………………………..….. 80

6.2.3 Experimental analysis tech technique...................................... 81

Chapter VII: Shale gas extraction ……………………………………… 82

7.1 shale gas extraction …........................................................................... 82

Chapter VIII:Evaluation of Shale-Gas Resources, production... 84

8.1 global shale gas resources……………………………………....……. 84

8.3 shale gas in Egypt …………………………………….…………..….. 84

References ……………………………………………………………………….…... 86


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Chapter I

Introduction Oil shale is commonly defined as a fine-grained sedimentary rock

containing organic matter that yields substantial amounts of oil and

combustible gas upon destructive distillation. Most of the organic

matter is insoluble in ordinary organic solvents; therefore, it must be

decomposed by heating to release such materials. Underlying most

definitions of oil shale is its potential for the economic recovery of

energy, including shale oil and combustible gas, as well as a number

of byproducts. A deposit of oil shale having economic potential is

generally one that is at or near enough to the surface to be developed

by open-pit or conventional underground mining or by in-situ

methods.

Oil shales range widely in organic content and oil yield.A

commercial grade of oil shale, as determined by their yield of shale

oil, ranges from about 100 to 200 liters per metric ton (l/t) of rock.


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The U.S. Geological Survey has used a lower limit of about 40 l/t for

classification of Federal oil-shale lands. Others have suggested a

limit as low as 25 l/t.

Deposits of oil shale are in many parts of the world. These

deposits, which range from Cambrian to Tertiary age, may occur as

minor accumulations of little or no economic value or giant deposits

that occupy thousands of square kilometers and reach thicknesses of

700 m or more.

Oil shales were deposited in a variety of depositional

environments, including fresh-water to highly saline lakes,

epicontinental marine basins and subtidal shelves, and in limnic and

coastal swamps, commonly in association with deposits of coal.

In terms of mineral and elemental content, oil shale differs from

coal in several distinct ways. Oil shales typically contain much larger


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amounts of inert mineral matter (60–90 percent) than coals, which

have been defined as containing less than 40 percent mineral matter.

The organic matter of oil shale, which is the source of liquid and

gaseous hydrocarbons, typically has a higher hydrogen and lower

oxygen content than that of lignite and bituminous coal.

In general, the precursors of the organic matter in oil shale and

coal also differ. Much of the organic matter in oil shale is of algal

origin, but may also include remains of vascular land plants that more

commonly compose much of the organic matter in coal.

The origin of some of the organic matter in oil shale is obscure

because of the lack of recognizable biologic structures that would

help identify the precursor organisms. Such materials may be of

bacterial origin or the product of bacterial degradation of algae or

other organic matter.


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The mineral component of some oil shales is composed of

carbonates including calcite, dolomite, and siderite, with lesser

amounts of aluminosilicates. For other oil shales, the reverse is

true—silicates including quartz, feldspar, and clay minerals are

dominant and carbonates are a minor component. Many oil-shale

deposits contain small, but ubiquitous, amounts of sulfides including

pyrite and marcasite, indicating that the sediments probably

accumulated in dysaerobic to anoxic waters that prevented the

destruction of the organic matter by burrowing organisms and

oxidation.

Although shale oil in today’s world market is not competitive

with petroleum, natural gas, or coal, it is used in several countries

that possess easily exploitable deposits of oil shale but lack other

fossil fuel resources. Some oil-shale deposits contain minerals and

metals that add byproduct value such as alum [KAl(SO4)2•12H2O],


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nahcolite (NaHCO3),dawsonite [NaAl(OH)2CO3], sulfur,

ammonium sulfate, vanadium, zinc, copper, and uranium.

The gross heating value of oil shales on a dry-weight basis ranges

from about 500 to 4,000 kilocalories per kilogram (kcal/kg) of rock.

The high-grade kukersite oil shale of Estonia, which fuels several

electric power plants, has a heating value of about 2,000 to 2,200

kcal/kg. By comparison, the heating value of lignitic coal ranges

from 3,500 to 4,600 kcal/kg on a dry, mineral-free basis (American

Society for Testing Materials, 1966).

Tectonic events and volcanism have altered some deposits.

Structural deformation may impair the mining of an oil-shale deposit,

whereas igneous intrusions may have thermally degraded the organic

matter. Thermal alteration of this type may be restricted to a small

part of the deposit, or it may be widespread making most of the

deposit unfit for recovery of shale oil.


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The grade of oil shale can be determined by measuring the yield

of oil of a shale sample in a laboratory retort. This is perhaps the

most common type of analysis that is currently used to evaluate an

oil-shale resource. The method commonly used in the United States

is called the “modified Fischer assay,” first developed in Germany,

then adapted by the U.S. Bureau of Mines for analyzing oil shale of

the Green River Formation in the western United States (Stanfield

and Frost, 1949).


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1.1 Definition of oil shale

OIL SHALE: Rock That Turns into Oil

Oil Shale is an organic-rich, fine-grained sedimentary rock that

contains a solid organic compound known as kerogen. Oil shale

generally contains enough oil that it will burn, earning it the

nickname, “the rock that burns”. Kerogen is one of the first stages of

organic matter processing into petroleum, and all oil and gas are

ultimately derived from kerogen. Oil shale contains the remains of

algae and plankto deposited millions of years ago that have not been

buried deep enough to become hot enough to break down into the

hydrocarbons targeted in conventional oil projects.


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1.2 Origin of oil shale Oil shale represents a large and mostly untapped hydrocarbon

resource. Like tar sand (oil sand in Canada) and coal, oil shale is

considered unconventional because oil cannot be produced directly

from the resource by sinking a well and pumping. Oil has to be

produced thermally from the shale. The organic material contained in

the shale is called kerogen, a solid material intimately bound within

the mineral matrix Oil shale is distributed widely throughout the

world with known deposition every continent.

1.3 Origin of Organic Matter

Organic matter in oil shale includes the remains of algae spores,

pollen, plant cuticle and corky fragments of herb-ceous and woody

plants, and other cellular remains of lacu-trine, marine, and land

plants. These materials are composed chiefly of carbon, hydrogen,

oxygen, nitrogen, and sulfur. Some organic matter retains enough

biological structures so that specific types can be identified as to


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genus and even species. In some oil shale, the organic matter is

unstructured and is best described as amorphous (bituminite). The

origin of this amorphous material is not well known, but it is likely a

mixture of degraded algal or bacterial remains. Small amounts of

plant resins and waxes also contribute to the organic matter. Fossil

shell and bone fragments composed of phosphate and carbonate

minerals, although of organic origin, are excluded from the definition

of organic matter used herein and are considered to be part of the

mineral matrix of the oil shale. Most of the organic matter in oil shale

is derived from various types of marine and lacustrine algae. It may

also include varied admixtures of biologically higher forms of plant

debris that depend on the depositional environment and geographic

position. Bacterial remains can be volumetrically important in many

oil shale, but they are difficult to identify. Most of the organic matter

in oil shale is insoluble in ordinary organic solvents, whereas some is

bitumen that is soluble in certain organic solvents.


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1.4 Thermal Maturity of Organic Matter

The thermal maturity of an oil shale refers to the degree to which

the organic matter has been altered by geothermal heating. If the oil

shale is heated to a high enough temperature, as may be the case if

the oil shale were deeply buried, the organic matter may thermally

decompose to form oil and gas. Under such circumstances, oil shale

can be source rocks for petroleum and natural gas.

1.5 Classification of oil shale

Mixed with a variety of sediments over a lengthy geological time

period, shale forms a tough, dense rock ranging in color from lighten

to black. Based on its apparent colors, shale may be referred to as

black shale or brown shale.

Oil shale has also been given various names in different regions.

For example, the Ute Indians, on observing outcroppings burst into


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flames after being hit by lightning, referred to it as the rock that

burns. Oil shale has received many different names over the years,

such as cannel coal, bog head coal, alum shale, stellarite, albertite,

kerogenshale, bituminite, gas coal, algal coal, wollongite, schistes

bitumineux, torbanite, and kukersite. Oil shale divided into three

groups based upon their environments of deposition—terrestrial,

lacustrine, and marine (fig.1.1).

(fig1.1) classification of oil shale


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Terrestrial oil shale include those composed of lipid-rich organic

matter such as resin spores, waxy cuticles, and corky tissue of roots,

and stems of vascular terrestrial plants commonly found in coal-

forming swamps and bogs.

Lacustrine oil shale includes lipid-rich organic matter derived

from algae that lived in freshwater, brackish, or saline lakes. The

lacustrine oil shale of the Green River Formation, which was

discussed above, is among the most extensively studied sediments.

However, their strongly basic depositional environment is certainly

unusual, if not unique.

Marine oil shale are composed of lipid-rich organic matter

derived from marine algae, acritarchs (unicellular organisms of

questionable origin), and marine dinoflagellates. Marine oil shale is

usually associated with one of two settings (Figure 1.2). The anoxic

silled basin shown (Figure 1.2a) can occur in the shallow water of a


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continental shelf. High phytoplankton growth rates near the surface

will give a high deposition rate. The sill shields the trough from the

circulation of oxygen-laden water. Under these conditions, the

decomposition of organic sedimentary matter will rapidly deplete

oxygen within the confines of the basin, thereby providing the

strongly anoxic (reducing, low-Eh) environment that is needed for

efficient preservation.

Fig (1.2)


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The anoxic zone in an upwelling area (Figure 1.2b) arises from

circulation of an open-ocean current over a cold, oxygen-depleted

bottom layer. Mixing of a nutrient-rich current, such as the Gulf

Stream, into the carbon dioxide-rich and light-rich eutrophic zone

gives an environment capable of sustaining very high rates of organic

production.

The black marine shale formed in shallow seas has been

extensively studied as they occur in many places. These shale were

deposited on broad, nearly flat sea bottoms and therefore usually

occur in thin deposits (10–50m thick), which may extend over

thousands of square miles.

Cannel coal is brown to black oil shale composed of resins,

spores, waxes, and coriaceous and corky materials derived from

terrestrial vascular plants together with varied amounts of vitrinite

and inertinite. Cannel coals originate in oxygen-deficient ponds or


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shallow lakes in peat-forming swamps and bogs. This type of shale is

usually rich inoil-generating lipid-rich organic matter derived from

plant resins, pollen, spores, plant waxes, and the corky tissues of

vascular plants.

Lamosite is pale-and grayish-brown and dark gray to black oil

shale in which the chief organic constituent is lamalginite derived

from lacustrine planktonic algae. Other minor components in

lamosite include vitrinite, inertinite, telalginite, and bitumen.

Marinite is a gray to dark gray to black oil shale of marine origin

in which the chief organic components are lamalginite and bituminite

derived chiefly from marine phytoplankton. Marinite may also

contain small amounts of bitumen, telalginite, and vitrinite.Torbanite,

tasmanite, and kukersite are related to specific kinds of algae from

which the organic matter was derived; the names are based on local

geographic features.


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Is a black oil shale whose organic matter is composed mainly of

telalginite derived largely from lipid-rich Botryococcus and related

algal forms found in fresh- to brackish-water lakes. It also contains

small amounts of vitrinite and inertinite.

Tasmanite, named from oil-shale deposits in Tasmania, is a

brown to black oil shale. The organic matter consists of telalginite

derived chiefly from unicellular tasmanitid algae of marine origin

and lesser amounts of vitrinite, lamalginite, and inertinite.

Kukersite, is a light brown marine oil shale. Its principal organic

component is telalginite derived from the green alga,

Gloeocapsomorphaprisca.

Fig(1.3) Fossils in Ordovician kukersite oil shale. Fig(1.4) Cannel coal from the Pennsylvanian of NE Ohio

https://en.wikipedia.org/wiki/Pennsylvanian_(geology)

https://en.wikipedia.org/wiki/Ohio


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1.6 Composition and properties

It is a fact the term oil shale describes an organic-rich rock from

which little carbonaceous material can be removed by extraction

(with common petroleum-based solvents) but which produces

variable quantities of distillate (shale oil) when raised to temperatures

greater than 350°C(660°F). Thus, oil shale is assessed by the ability

of the mineral to produce shale oil in terms of gallons per ton by

means of a test method(Fischer assay) in which the oil shale is heated

to 500°(930°F).

1.6.1 Mineral Components

Oil shale has often been termed as (incorrectly and for various

illogical reasons) high-mineral coal. Nothing could be further from

the truth than this misleading terminology. Coal and oil shale are

fraught with considerable differences and such terminology should be

frowned upon. Furthermore, the precursors of the organic matter in


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oil shale and coal also differ. Much of the organic matter in oil shale

is of algal origin, but may also include remains of the vascular land

plants that more commonly compose much of the organic matter in.

In addition, the lack of recognizable biological structures in oil shale

that would help identify the precursor organisms makes it difficult to

identify the origin of the organic matter.

In terms of mineral and elemental content, oil shale differs from

coal in several distinct ways. Oil shale typically contains much larger

amounts of inert mineral matter (60–90%) than coal, which has been

defined as containing less than 40% mineral matter. The organic

matter of oil shale, which is the source of liquid and gaseous

hydrocarbons, typically has higher hydrogen and lower oxygen

content than that of lignit or bituminous coal. The mineral component

of some oil shale deposits is composed of carbonates including

calcite (CaCO3), dolomite (CaCO3 · MgCO3), siderite (FeCO3),


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nahcolite (NaHCO3), dawsonite [NaAl(OH)2CO3], with lesser

amounts of alumino-silicates—such as alum [KAl(SO4)2 12H2O]—

and sulfur, ammonium sulfate, vanadium, zinc, copper, and uranium,

which add by-product value.

Table (1.2) General composition of oil shales

General composition of oil shales

Inorganic matrix Bitumens Kerogens

quartz; feldspars; clays (mainly illite and chlorite; carbonates (calciteand dolomite); pyrite and others

soluble inCS2

insoluble in CS2; containing uranium, iron, vanadium,nickel, molybdenum, etc.

https://en.wikipedia.org/wiki/Quartz

https://en.wikipedia.org/wiki/Feldspar

https://en.wikipedia.org/wiki/Clay

https://en.wikipedia.org/wiki/Illite

https://en.wikipedia.org/wiki/Chlorite_group

https://en.wikipedia.org/wiki/Chlorite_group

https://en.wikipedia.org/wiki/Calcite

https://en.wikipedia.org/wiki/Dolomite

https://en.wikipedia.org/wiki/Pyrite

https://en.wikipedia.org/wiki/Carbon_disulfide

https://en.wikipedia.org/wiki/Uranium

https://en.wikipedia.org/wiki/Iron

https://en.wikipedia.org/wiki/Vanadium

https://en.wikipedia.org/wiki/Nickel

https://en.wikipedia.org/wiki/Molybdenum

https://en.wikipedia.org/wiki/Molybdenum


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Chapter II

Exploration of oil shale

Successful oil shale exploration and development generally

progresses through three basic operational phases include:

2.1 Geological investigation.

2.2 Geophysical investigation.

2.3 Geochemical investigation.

Exploration of oil shale depending on the oil shale deposit;

I- In-situ deposits (under layers)[geological, geophysical,

Palynological and geochemical investigation]

II- Ex-situ deposits (outcrop) [geological, Palynological and

geochemical investigation]


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2.1 Geological investigation: The geological investigation method

depends mainly on remote sensing, aerial and satellite photographs

and the mapping of outcrop rocks and the geologic section.

Fig (2.1) geologic section

2.2 Geophysical investigation: Seismic Reflection Survey is the

most common indirect method used for locating subsurface

structures that may contain oil shale. And well logging.


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Geophysical characteristics of oil shale. This paper analyzes

log and seismic response characteristics based on the petrologic

characteristics of high organic matter of the oil shale. This constructs

a theoretical base to estimate oil shale.

Single-well evaluation of oil shale. This paper analyzes the

ΔlogR technique based on the log response characteristics of oil

shale, and constructs the ΔlogR-TOC relational model., we mainly

adopt the method of log-seismic multi-attributes reconstruction to

predict the TOC of single wells.

Seismic quantitative evaluation of oil shale. In this paper 3-

D seismic data is used. The inversion volume of wave impedance is

obtained through the sequence-log constrained seismic inversion

method and the inversion volume of TOC. The relationship between

TOC and oil yield (measured by the BGMR Fischer Assay method of

Royal Dutch Shell Plc) is used to obtain the inversion volume of oil

yield and realize the quantitative evaluation of oil shale.


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On the basis of above key steps, a technical flowchart for the

quantitative evaluation of oil shale with geophysical technique is

provided, as shown in fig (2.2)

Fig 2.2. Evaluation flowchart of geophysical technique of oil shale.

2.2.1 Seismic characteristics of oil shale

The oil shale Basin has the following seismic sedimentary

characteristics: (1) The oil shale presents the features of higher

frequency, better continuity, and medium-strong amplitude; (2) the

seismic reflection structure of oil shale is parallel to sub parallel

having mainly parallel sedimentation of lacustrine strata in deep


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(Fig. 2.3) illustrates the seismic reflection profile across the wells.

water environments. (Fig. 2.3) illustrates the seismic reflection

profile across the wells. The profile has four groups of strong

reflectors: (1) the seismic event above T2 shows low-frequency and

high-amplitude seismic reflection features. Affected by tectonic fault,

the seismic event has low continuity; (2) the seismic event about

1100 ms of well side shows low-frequency, good-continuity and

high-amplitude seismic reflection features; (3) the seismic event

above T1 shows double-track seismic reflection features with low


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frequency, good continuity, and medium-high amplitude; (4) the

seismic event above T07 corresponds to the maximum transgressive

period, and shows seismic reflection features with high frequency,

medium– high amplitude and good continuity.

Because of seismic resolution constraints, the identification of oil

shale on a regular seismic profile can be conducted based only on the

drilling calibration result. The seismic reflection feature with strong

amplitude is possibly the comprehensive response of the interbedding

of mudstone and oil shale. Accurate calibration of the oil shale on the

seismic profile is difficult; thus, it is identified by using other seismic

methods.

2.2.2 Log characteristics of oil shale

The log response characteristics of oil shale depend mainly on the log

response to organic matter and rock matrix. The oil shale with high

organic matter content has the following characteristics: (1) organic

matter has strong radioactivity, and its natural gamma value is higher


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than that of rock matrix; hence, the oil shale has a high gamma log

value; (2) the organic matter is a non-conducting material and its

occurrence worsens the conducting property of the rock.

Fig (2.4) Log response characteristics of oil shale

Its resistivity is greater than that of rock matrix; thus, the oil shale has

a high resistivity log value; (3) the organic matter is the light-weight

medium that is not conducive to acoustic wave transmission. The

acoustic travel time is greater than that of rock matrix, endowing the

oil shale with a log value of high acoustic travel time log value; (4)

the organic matter has low density and its density is much lower than


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that of rock matrix, so the oil shale has a low-density log value; (5)

the organic matter has low density, and its hydrocarbon content is

considerably higher than that of rock matrix, presenting high-neutron

porosity values. Therefore, the log response of oil shale exhibits the

“four-high and one-low characteristics”: high-natural gamma, high

resistivity, high acoustic travel time, high-neutron porosity, and low

density.

2.2.3 Single-well evaluation of oil shale

I- Analysis of ΔlogR technique

During the logR analysis, three-porosity log curves (acoustic, density

and neutron) generally overlay with the resistivity curve. In this study

area, the natural gamma response and resistivity curve have good

overlay and the oil shale layer has prominent characteristics. Thereby

we take gamma/resistivity as the type of curve overlay for ΔlogR

analysis and assign physical meaning to it. In ΔlogR analysis, the

combination of log curves reflects the lithology of undisturbed


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formation correctly and the overlay of log and resistivity curves

corresponds to the most prominent log response of oil shale. Only

one type of curve cannot be applied blindly. Figure 7 shows the

gamma/resistivity overlay for ΔlogR analysis of oil shale. The natural

gamma response at this well has the most prominent response to oil

shale. Although the density curve exhibits good log response at the

oil shale layer, it is prone to wall collapse.

Fig. 2.5 Analysis of ΔlogR of well

Hence, ΔlogR analysis is carried out through gamma/resistivity

overlay. Assume that the natural gamma response and resistivity

overlay equation for the calculation of ΔlogR is: Δlog R = log10 (R /

Rbaseline ) + 0.02 × (GR −GRbaseline ),


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where ΔlogR is the curve separation measured in logarithmic

resistivity cycles; R, Rbaseline present the resistivity log value and

the baseline of the overlaid resistivity in Ω·m, respectively; GR

GRbaseline denote the gamma log value and the baseline of the

overlaid gamma response in API, respectively; 0.02 is based on the

ratio of 50 API per one resistivity cycle mentioned above, an

empirical parameter. According to the baseline of curve overlay,

GRbaseline is 62.03 API and Rbaseline is 5.02 Ω·m. These are

introduced into equation (1) to obtain ΔlogR curve, combined with

the measured TOC for linear regression analysis (Fig. 2.5) and the

relational model between the TOC and ΔlogR ,

TOC = 7.3211× Δlog R + 0.2771, (2) where TOC is the total organic

carbon content measured in wt%; ΔlogR is the curve separation

measured in logarithmic resistivity cycles; 0.2771 is the baseline

value of TOC. The “0.2771” is very important to compensate the

background value of TOC, and it means that the TOC value is not

zero when the ΔlogR is zero, which can be proved by measuring

TOC from Fig. 8. The TOC and ΔlogR show an apparent positive


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correlation, with a correlation coefficient (R2) of 0.913, indicating

that TOC and ΔlogR have good correlation and TOC can be

predicted by using this relational model.

Fig.2.6. Correlation diagram of

ΔlogR vs. measured TOC

The following two aspects are being paid much attention to during

the application of ΔlogR technique: (1) the log curve is always

influenced by the well environment and cannot reflect the

information on undisturbed formation accurately. The accuracy of the

log response was monitored before application; (2) the baseline of the

ΔlogR method represents non source rocks, and the baseline TOC

value is defined as zero value of TOC. However, the TOC of “non-


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source rock” is not zero, but just lower than the defined value of

source rock. Hence, the background value of the TOC curve

predicted by the ΔlogR method is lower. Generally, a fixed

background value is directly added to compensate the baseline value

of TOC (e.g. equation (2)). However, in practice the background

value may be changed vertically depending on lithology of

formation.

2.2.4 Analysis of log-seismic multi-attributes

Regarding to potential issues in the application of ΔlogR

technique, log seismic multi-attributes are used to predict TOC. By

analyzing the oil shale log and seismic response features, a

comprehensive geophysical response is obtained. In this study the

TOC is predicted by choosing the prominent log seismic attributes

among the response multi-attributes of oil shale. Additional

information regarding the undisturbed formation is incorporated to

lay the foundation for improving the precision of TOC prediction.


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Using log seismic multi-attributes, the TOC from ΔlogR technique is

taken as the target curve and carefully chosen log-seismic multi-

attributes are integrated to obtain the predicted TOC.

The widespread application of the log-seismic multi-attributes

method is limited by data constraints in the study area. However, this

method still presents certain advantages: (1) the introduction of

seismic attributes of the well site that are not influenced by the well

environment to avoid the quality of the log curve to become

influenced by the environmental factor of the well; and (2) the good

usage of the log-seismic multi-attributes to determine that the shale

has better geophysical response, and the adoption of convolution

factor algorithm to predict TOC, so that the predictive result responds

more accurately to the strata information and allows for a vertically

compensated background value of TOC. This conforms to the

vertical geological variations of strata in the TOC.


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2.2.5 Seismic quantitative evaluation of oil shale

2.2.5.1 The log-constrained seismic inversion

Seismic inversion is a common and effective method for

interpreting lithology. No report on the interpretation of oil shale

using the inversion method has been published because the

realization process is subject to numerous constraints, such as the

seismic response and seismic resolution of oil shale.

The marking of seismic geological horizon is taken as the

sequence constraint. The initial inversion model is constructed by

interpolating and extrapolating the log data in the 3-D seismic

volume.

Fig.2.7 Inversion profile

of wave impedance

along a cross section of

wells


38 | P a g e

The inversion volume of wave impedance is used to predict the

spatial distribution of oil shale by displaying relatively low velocity

through the adjustment of color marks, continuity and vertical change

in thickness; this does not achieve the target of quantitative

assessment of the spatial distribution of oil shale. To achieve the

seismic quantitative evaluation of oil shale, the quantitative

parameters like TOC and oil yield of oil shale must be predicted.

2.2.5.2 Prediction of the inversion volume of TOC

In combining the TOC curves of single-well obtained through

log-seismic Multi-attributes method and the inversion volume of

seismic inversion, we calculate the relationship between the TOC of

well site and seismic wave impedance from well side, and then use

above relationship to extrapolate from the well to the entire 3-D

study area. Finally we obtained the inversion volume of TOC to

realize the seismic quantitative evaluation of oil shale. Spatial

quantitative evaluation based on the inversion volume of TOC allows


39 | P a g e

predicting the spatial distribution of oil shale and also enables the

quantitative evaluation of oil shale quality.

Fig.2.8 Inversion profile of TOC along a cross section of well

The TOC inside the oil shale layer changes both transversely and

vertically. In this Fig, the curves of well-points are the prediction

TOC of single-well. Comparing the single-well TOC and inversion

TOC of well site shows that the two have good correspondence

which indicates that the seismic method enables the rational

prediction of TOC.


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2.2.5.3 Prediction of the inversion volume of oil yield

Oil yield is a direct parameter for quantitative evaluation of the

oil shale and the inversion volume of oil yield must be obtained for

the seismic quantitative evaluation of oil shale. By determining the

relationship between the TOC and oil yield, the inversion volume of

oil yield is obtained through the inversion volume of TOC. To obtain

the reliable quantitative relationship between the TOC and oil yield,

the data should satisfy the following conditions: (1) to avoid the

influence of tectonic factors on oil shale formation, collecting data

from wells at different positions of the study area is a more favorable

approach; (2) to eliminate model instability resulting from

incomplete rules in the section disclosed by the data, collecting data

from the continuously cored well is a better technique.

OY = 0.8015×TOC −0.6645

Where OY is the oil yield measured in wt% and TOC is the total

organic carbon measured in wt%.


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Fig.2.9 Correlation diagram of TOC vs. oil yield

Shows a good linear relationship between the TOC and oil yield, and

the correlation (R2) is as high as 0.968. When the TOC is 5.0 wt%,

the oil yield is about 3.5 wt%. Hence, OY>3.5 wt% and TOC >5.0

wt% are taken as the criteria for the quantitative evaluation of oil

shale.


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Fig.2.10 Inversion profile of oil yield along a cross section The inversion profile of oil yield the black layer is the section with an

oil yield greater than 3.5 wt%. It can be directly and quantitatively

assessed as oil shale. The spatial distribution of oil shale has features

similar to the inversion result for the wave impedance and TOC. It is

continuous in trans-verse extension and has the distribution features

of multi-layers at the vertical direction. The inversion results of oil

yield can provide more accurate evaluation. The oil yield curve of

well and inversion oil yield of well site show better consistency;

hence, the inversion result for oil yield is quite rational.


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Fig.2.11 3-D diagram for spatial quantitative evaluation of oil shale

This figure show the 3-D diagram for the spatial quantitative

evaluation of oil shale the layer with oil yield greater than 3.5 wt% is

marked as the oil shale. According to the evaluation result, the

spatial distribution of oil shale has multi-layers and good continuity.

However, the spatial distribution varies among different oil shale


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layers. Indicates that continuity, oil yield, quality, horizontal and

vertical distribution. The higher value of oil yield in transverse

upward inversion appears at the edges of basin with smaller

variations and faults in the secondary tectonic unit. The inversion

result for oil yield enables quantitative evaluation not only of the

spatial distribution of oil shale, but also of the grade of oil shale.


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2.3 Geochemical exploration: Evaluate and compare petroleum

yield from pyrolysis methods

2.3.1 Rock Eval pyrolysis

2.3.2 Fischer Assay

2.3.3 Hydrous Pyrolysis Oil Yields


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2.3.1 Rock Eval pyrolysis: heating of organic matter in the

absence of oxygen to yield organic compounds,

• Programmed Pyrolysis: – Pulverized samples are gradually

heated under an inert atmosphere – Heating distills the free organic

compounds (bitumen), and then cracks pyrolyti products from the

insoluble organic matter (kerogen).

Pyrolysis to measure: • Hydrocarbon Content – S1 • Remaining Hydrocarbon Generation Potential – S2 • Organic richness – TOC • Maturation, type, environment • Thermal Maturity – Tmax


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2.3.2 Fisher Assay (fig2.14): The Fischer assay is a standardize

laboratory test for determining the oil yield from oil shale to be

expected from a conventional shale oil extraction. A 100 gram oil

shale sample crushed to <2.38 mm is heated in a small aluminum

retort to 500 °C (930 °F) at a rate of 12°C/min (22°F/min), and held

at that temperature for 40 minutes. The distilled vapors of oil, gas,

and water are passed through a condenser

and cooled with ice water into a

graduated centrifuge tube. The oil yields

achieved by other technologies are often

reported as a percentage of the Fischer

Assay oil yield.

Oil product yield and composition is

comparable to surface retorting methods.

Fig 2.14


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2.3.4 Hydrous Pyrolysis

Heating in the presence of liquid water

Estimating yield from TOC is not optimal, Rock Eval S2 and Fischer

Assay yields are comparable


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Chapter III

Extraction of oil shale

Fig 3.1 oil shale extraction

3.1 Ex-Situ Processing:

Oil shale is crushed into smaller pieces, increasing surface area for

better extraction. The temperature at which decomposition of oil shale

occurs depends on the time-scale of the process.


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In ex situ retorting processes, it begins at 300 °C (570 °F) and

proceeds more rapidly and completely at higher temperatures. The

amount of oil produced is the highest when the temperature ranges

between 480 and 520 °C (900 and 970 °F). The ratio of oil shale gas

to shale oil generally increases along with retorting temperatures.

Hydrogenation and thermal dissolution (reactive fluid processes)

extract the oil using hydrogen donors, solvents, or a combination of

these. Thermal dissolution involves the application of solvents at

elevated temperatures and pressures, increasing oil output

by cracking the dissolved organic matter. Different methods produce

shale oil with different properties.

In ex situ processing, also known as above-ground retorting, the

oil shale is mined either underground or at the surface and then

transported to a processing facility. In contrast, in situ processing

converts the kerogen while it is still in the form of an oil shale

https://en.wikipedia.org/wiki/Hydrogen_donor

https://en.wikipedia.org/wiki/Solvent

https://en.wikipedia.org/wiki/Cracking_(chemistry)

https://en.wikipedia.org/wiki/Retorting

https://en.wikipedia.org/wiki/Underground_mining_(soft_rock)

https://en.wikipedia.org/wiki/Surface_mining


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deposit, following which it is then extracted via oil wells, where it

rises in the same way as conventional crude oil. Unlike ex

situ processing, it does not involve mining or spent oil shale disposal

aboveground as spent oil shale stays underground.

By heating method: The method of transferring heat from

combustion products to the oil shale may be classified as direct or

indirect. While methods that allow combustion products to contact

the oil shale within the retort are classified as direct, methods that

burn materials external to the retort to heat another material that

contacts the oil shale are described as indirect

Fig 3.2 oil shale retorting

https://en.wikipedia.org/wiki/Oil_well

https://en.wikipedia.org/wiki/Retort


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3.2 Ex situ technologies

"Ex-situ" technologies are sometimes classified as vertical or

horizontal. Vertical retorts are usually shaft kilns where a bed of

shale moves from top to bottom by gravity. Horizontal retorts are

usually horizontal rotating drums or screws where shale moves from

one end to the other. As a general rule, vertical retorts process lumps

using a gas heat carrier, while horizontal retorts process fines using

solid heat carrier.

Fig 3.4 Ex situ technologies

The spent shale from the separation processes could be used in road filling or it could be returned to the mine area.


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3.2.1 Internal combustion

Internal combustion technologies burn materials (typically char

and oil shale gas) within a vertical shaft retort to supply heat for

pyrolysis. Typically raw oil shale particles between 12 millimeters

(0.5 in) and 75 millimeters (3.0 in) in size are fed into the top of the

retort and are heated by the rising hot gases, which pass through the

descending oil shale, thereby causing decomposition of the kerogen

at about 500 °C (932 °F) . Shale oil mist evolved gases and cooled

combustion gases are removed from the top of the retort then moved

to separation equipment. Condensed shale oil is collected, while non-

condensable gas is recycled and used to carry heat up the retort. In

the lower part of the retort, air is injected for the combustion which

heats the spent oil shale and gases to between 700 °C (1,292 °F) and

900 °C (1,650 °F). Cold recycled gas may enter the bottom of the

retort to cool the shale ash. The Union A and Superior Direct


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processes depart from this pattern. In the Union A process, oil shale

is fed through the bottom of the retort and a pump moves it upward.

In the Superior Direct process, oil shale is processed in a horizontal,

segmented, doughnut-shaped traveling-grate retort.

3.2.2 Hot recycled solids

Hot recycled solids technologies deliver heat to the oil shale by

recycling hot solid particles—typically oil shale ash. These technologies

usually employ rotating kiln or fluidized bed retorts, fed by fine oil shale

particles generally having a diameter of less than 10 millimeters (0.4 in);

some technologies use particles even smaller than 2.5 millimeters

(0.10 in). The recycled particles are heated in a separate chamber or

vessel to about 800 °C (1,470 °F) and then mixed with the raw oil shale

to cause the shale to decompose at about 500 °C (932 °F). Oil vapor and

shale oil gas are separated from the solids and cooled to condense and

collect the oil. Heat recovered from the combustion gases and shale ash

https://en.wikipedia.org/wiki/Traveling-grate_retort

https://en.wikipedia.org/wiki/Rotary_kiln

https://en.wikipedia.org/wiki/Fluidized_bed


55 | P a g e

may be used to dry and preheat the raw oil shale before it is mixed

with the hot recycle solids.

In the Galoter and Enefit processes, the spent oil shale is burnt in a

separate furnace and the resulting hot ash is separated from the

combustion gas and mixed with oil shale particles in a rotating kiln.

Combustion gases from the furnace are used to dry the oil shale in a dryer

before mixing with hot ash. The TOSCO II process uses ceramic balls

instead of shale ash as the hot recycled solids. The distinguishing feature

of the Alberta Taciuk Process (ATP) is that the entire process occurs in a

single rotating multi–chamber horizontal vessel.

Fig 3.5 Alberta Taciuk Process (ATP)

https://en.wikipedia.org/wiki/Galoter_process

https://en.wikipedia.org/wiki/Enefit_process

https://en.wikipedia.org/wiki/TOSCO_II_process

https://en.wikipedia.org/wiki/Ceramic

https://en.wikipedia.org/wiki/Alberta_Taciuk_Process


56 | P a g e

3.23 Conduction through a wall

These technologies transfer heat to the oil shale by conducting it

through the retort wall. The shale feed usually consists of fine particles.

Their advantage lies in the fact that retort vapors are not combined with

combustion exhaust. The Combustion Resources process uses a

hydrogen–fired rotating kiln, where hot gas is circulated through an

outer annulus. The Oil-Tech staged electrically heated retort consists of

individual inter-connected heating chambers, stacked atop each other. Its

principal advantage lies in its modular design, which enhances its

portability and adaptability.

3.3 In-situ processing

In situ processing converts the kerogen while it is still in the form of

an oil shale deposit, following which it is then extracted via oil wells,

where it rises in the same way as conventional crude oil unlike ex

situ processing, it does not involve mining or spent oil shale disposal

aboveground as spent oil shale stays underground.

https://en.wikipedia.org/wiki/Combustion_Resources

https://en.wikipedia.org/wiki/Annulus_(oil_well)

https://en.wikipedia.org/wiki/Ambre_Energy

https://en.wikipedia.org/wiki/Modular_design

https://en.wikipedia.org/wiki/Oil_well


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3.4 In-Situ Technologies:

3.4.1 Shell In Situ Conversion Process (ICP).

3.4.2 American Shale Oil Process.

3.4.1 Shell In Situ Conversion Process (ICP)

• Deep vertical holes are drilled through a section of oil shale.

• Heating underground oil shale using electric heaters placed in the

deep vertical holes.

• The entire oil shale is heated over a period of two to three years

until it reaches 650–700 °F (340 and 370 °C).

Fig 3.6 Shell In Situ Conversion Process (ICP)

http://en.wikipedia.org/wiki/Environmental_impact_of_the_oil_shale_industry






58 | P a g e

3.4.2 American Shale Oil Process Conduction, Convection, Reflux (CCR) Process

• Horizontal wells are drilled beneath the oil shale layer.

• Superheated steam or another heat transfer medium is circulated through the

horizontal pipes

• As the organic matter within the rocks boils, it will break the rocks apart and

free the oil and gas to be collected.

Fig 3.7 (CCR) Process



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Chapter IV

Evaluation of Oil-Shale Resources, production

Fig4.1 global oil shale sources

Resource Estimates Vary in Quality Fig 4.2 quality of oil shale


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How Much Has Been Produced (Fig 4.3)

Fig 4.3

4.2 Projected Global Oil Shale Production (Fig 4.4)

Fig 4.4


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How Aggressively Can it Grow? (Fig 4.5)

Fig 4.5 Grow carve with year of oil shale


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4.3 oil shale in Egypt

Oil shale was discovered in 1940s during phosphate mining (Fig 4.6)

Researches in 1970s showed that Egypt has plenty of Oil shale with shale oil

reserves at:

• Western Desert: Abu Tartor

• Eastern Desert: Red Sea (Quiser , Safaga)

• Nile of valley: Edfu

Safaga

Quiser

Abu Tartor Area

Edfu


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Evaluation and Analysis of Oil Shale in Quseir-Safaga eastern Desert,

Egypt:

Qusier phosphate mine in the Red Sea coast (Cretaceous -

Eocene) The Qusier and Safaga areas are part of the Eastern Desert of

Egypt at the Red Sea Coast, and gained importance since five decades

when the phosphate deposits of the Gebel Duwi RangeDuwi

Formation U. Campanian - L. Maastrichtian.

Geological settings of the Duwi Formation:

The Precambrian granite and metamorphic rocks (gneiss, schist)

compose the basement complex in Egypt. They form a rough terrain

at the Eastern Desert of Egypt along the Red Sea coast and Sinai.

The Upper Cretaceous to Lower Cenozoic sedimentary rocks cover

the basement complex in some areas.

The Duwi Formation is a part of the Upper Cretaceous– Lower

Cenozoic sedimentary sequence and is widely distributed in the


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Eastern Desert, Nile Valley and Western Desert areas. The Duwi

Formation unconformably overlies the fluvial shale sequence of the

mid Campanian Qusseir Formation, and conformably underlies the

deep marine shales and marls of themid Maastrichtian Dakhla

Formation. Thus, deposition of the Duwi Formation represents an

initial stage of the Late Cretaceous marine transgression in Egypt.

The Gebel Duwi region extends in a northwest direction along the

western coast of the Red Sea from south of Al-Qusseir to Safaga,

between latitude 25500 and 26670N and longitude 33450 and

34250E, covering an area of about 500 km2

The general lithological compositions of the Duwi Formation

The Duwi Formation is usually subdivided into three members by

Said and Temraz .In, Said extended the use of the term Duwi

Formation to laminated gray clays and chert phosphatic bands at

Safaga and subdivided the whole section in the Red Sea area into


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three members, which are Atshan or ‘‘A’’, middle Duwi or ‘‘B’’

member and lower Abu Shegela or ‘‘C’’ member. The Atshan or

‘‘A’’ member is separated from the middle Duwi or ‘‘B’’ member by

an Oyster limestone bed 6–16 m in thickness; while the lower Abu

Shegela, or ‘‘C’’ member, is separated from the middle member by a

shale unit of variable thickness (6–10 m). In the present time, the

Duwi Formation is subdivided into four members, which are the

lower, the middle, the upper and the uppermost members by Baioumy

and Tada and Baioumy et al. The oil shale beds are concentrated in

the Atshan or ‘‘A’’ and middle Duwi or ‘‘B’’ members.


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Fig 4.7 Image showing the locations of the mines where the studied materials were collected.


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Table 4.1 Guidelines for pyrolysis parameters of quality, quantity and thermal maturity (adapted and modified after both Tyson, Peters and Cassa .

Table 4.2 Geochemical parameters that measured by the rock eval pyrolysis for the studied oil shale samples. The sample numbers referred to the palynological samples. The samples without indicative numbers are omitted from the palynological investigations.


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Geochemical analyses

Fig 4.9 HI versus Tmax diagram (modified from Tyson)

Fig 4.8 Van Krevelen-type diagram

Fig 4.10 Production index versus the Tmax (C)

adapted after, adopted after GeoMark sheet.


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The thermal maturity is shown in Figs. 4.8 – 4.10 respectively. All the

samples that were geochemically analyzed from the different locations varied

between poor and excellent production potential according to the standard

guidelines of Peters and Cassa (Table 4.1). The samples from El-Nakheil

(19.18–22.23 wt%) have the highest TOC values and they are considered as

excellent producers. The samples from El-Beida (11.45–11.61 wt%),

Mohamed Rabah (9.66 wt%) and Wasif (8.39 wt%) are much lower than El-

Nakheil however still excellent producers. The samples from Umm Hueitat

(2.6– 5.18 wt%) have a lower potentiality as it is ranging from very good to

excellent. The samples from Younis mine (0.04– 1.77 wt%) have the lowest

production potentiality of all samples and are considered as poor to good. The

(S1) values are generally low in the samples of Mohamed Rabah (1.30 mg

HC/grock), Wasif (0.10–0.98 mg HC/grock), Umm Hueitat (0.23–0.39 mg

HC/grock) and are mainly related to low maturity of these samples despite

their high content of TOC. Whereas, the sample from Younis (0.14 mg

HC/grock) is mainly related to low maturity of the rock samples and low TOC

Content. The low values of (S1) should reduce production potentiality (S1 +

S2). The values of S1 of the samples from El-Nakheil (4.05–4.18 mg


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HC/grock) and El-Beida (1.97–2.01 mg HC/grock) are relatively high, which

in turn indicate that they are very good to excellent producers. The values of

Hydrogen index (HI) in the samples from El-Nakheil (679–716 mg HC/g

TOC), Mohamed Rabah (603 mg HC/ g TOC) and El-Beida (566 mg HC/g

TOC) indicated high quality oil prone kerogen type I. The other samples are

oil prone as well; however, type II kerogen was detected. Two samples from

Wasif (38 mg HC/g TOC) and Younis (94 mg HC/g TOC) indicated gas prone

type IV kerogen. The measured Tmax (409–427 _C) in all samples indicated

immature kerogens to yield hydrocarbons (Figs. 4.9 and 4.10).

Reserves in Egypt • Safaga and Quiser

• Contain 9.1 Billion tons

• Geological reserves: 2.3 Billion bbls

• Nile Valley

• Very large amounts compared to Safaga & Quiser


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Chapter V

Introduction of shale gas

Shale gas is defined as unconventional gas that is trapped within

shale formation, usually in organic-rich shale with ultra-low porosity and

permeability. Shale gas is not new, but only recently has it become so

important. The formation and distribution of shale gas were special, and

were characterized by large resources potential and long development

history. Shale gas reservoirs are complicated, including organic rich shale

and interbedded silts. Diversity is obvious among different shale gas

reservoirs. The targets for shale gas exploration are organic-rich shale

that was deposited in such a manner as to preserve a significant fraction.

Shale gas reservoirs are characterized by ultra-low porosity and

permeability, leading to no natural productivity or low productivity.

Large multistage hydraulic fracturing and horizontal well techniques are

needed in economic recovery, leading to a long production period in a

single well.


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5.1 Different between shale gas and natural gas

Conventional and unconventional gases are the same thing in that they

are both natural gas and are chemically the same. Where they differ is in the

geological characteristics of the rocks in which they are found, referred to as

the reservoir rock. Although we might think of a reservoir a continuous body

or pool of fluid (or in this case gas) this is not the case with a gas reservoir

which is made up of small amounts of gas trapped with the spaces between

the fine grains that make up the reservoir rock with the characteristics of the

reservoir rock being determined by its porosity and its permeability.

Figure 5.1: Schematic showing the geometry of conventional and unconventional natural gas

resources Source: U.S. Energy Information Administration


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The growth in maturity of many conventional gas fields and concerns

over declining production has prompted greater investment in the exploration

and exploitation of unconventional gas resources. By combining new drilling

technologies, especially horizontal drilling, with hydraulic fracturing it has

been possible to tap into huge volumes of natural gas within deep seated shale

beds that had previously been considered unrecoverable. The result has been a

significant increase in estimates in natural gas reserves with some estimates

suggesting that unconventional gas may be as, or even more abundant, and

with a much wider geographical distribution than conventional gas sources.

5.2 Types and characteristics of shale gas

Typically, shale types include black shale, carbonaceous shale, siliceous

shale, ferruginous shale, and calcareous shale. When sandy components are

mixed in with shale, it can form sandy shale. According to the size of the sand

grains, sandy shale can be divided into silty shale and sandy shale. Organic-

rich shale is the major rock type for the formation of shale gas, which includes

black shale and carbonaceous shale. Black shale includes large amounts of

organic matter, fine and scattered pyrite, and siderite, where TOC is usually


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3%-15% or more with extremely laminated bedding. Carbonaceous shale

contains large amount of fine and scattered carbonaceous organic matter

(usually TOC is 10%-20%), which is characterized by black color staining

and large amounts of fossil plant. Regardless of the kind of shale, their anti-

weathering capacity is weak, where low mountains and valleys were usually

formed in natural topography

5.3 Basic Characteristics of Shale Gas (Table 5.1 )

Shale gas can be formed when the organic-rich shale is developed and

enters into the gas-generation period in sedimentary basins. Therefore, if gas

source rock is dark organic-rich shale, shale gas can be found in basins with

conventional gas. Only source rock with good quality can form shale gas with

commercial value for development. Based on evaluation of geological

characteristics, potential commercial value for shale gas exploration and

development can be confirmed. Now, shale or core area for commercial

development of shale gas usually refers to the effective shale, where the TOC

is more than 2% in the gas generation window and brittleness mineral content

is over 40%. Requirements for commercial development can be met when the


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thickness of effective shale is more than 30-50m (more than 30 m when

effective shale was continuously developed, cumulative thickness is more

than 50 m when effective shale was discontinuously developed or TOC was

less than 2%). The minimum effective thickness of gas-generation shale in

North America is 6 m (Fayetteville), and the maximum is 304 m (Marcellus).

Effective thickness of shale in the core areas is more than 30 m. Based on the

exploration and development of shale gas in North American, statistical

analysis, and critical experiments, it can be concluded that favorable shale gas

and core area are characterized by following geological and development

characteristics.

Table 5.1


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5.4 CHARACTERISTICS OF SHALE RESERVOIR

Shale is the source rock, and also the reservoir, formed by the typical

mechanism of “in-situ saturation reservoiring.” During the biochemical gas

generation phase, natural gas or oil cracking gas initially adsorbed on the

organic matter or rock grain surface or accumulated within the organic pore

space and stayed there until saturation. Then, the oversaturated natural gas

experienced primary migration in free phase or dissolved phase to the pore

space of the overlying inorganic shale interval. Part of it will be stored within

the intergranular and intragranular pores or fractures in free phase. After re-

saturation, part of the natural gas will be migrated to conventional reservoir

rock through secondary migration and will form a conventional gas reservoir.

Fig 5.2 shale gas reservoir


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Chapter VI

Shale gas exploration

Exploration stage: finding depth, thickness and areal extent of promising

shale. Structural and stratigraphic interpretation of seismic data Assessment of

source potential: finding effective source rock. Geochemical,

sedimentological, log evaluation and basin modelling methods. The factors

which make good source rocks (TOC, maturity etc.) also influence the seismic

response and hence can be inferred from seismic attributes.

6.1 GEOLOGICAL EVALUATION TECHNIQUE

The objective of geological evaluation for shale gas is to optimize

favorable accumulation area. Except for the conventional methods (such as

the geological survey, geophysical exploration, drilling of parameter wells,

analysis, and testing), the core is to gain key parameters (such as buried depth

of shale, thickness, rock texture, mineral composition, rock physical

properties, organic geochemistry, geophysics, well drilling, and fracturing) to

make fundamental maps. According to regional geological characteristics,


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each geological evaluation standard can be confirmed to identify, evaluate,

and optimize favorable areas synthetically

6.2 RESERVOIR EVALUATION TECHNIQUE

Reservoir evaluation seeks to describe the spatial distribution

characteristics of shale reservoir both qualitatively and quantitatively and to

simulate the storage and production status of gas in shale. Five major steps are

included in the evaluation flow : (1) Carry out analysis on the physical

properties of cores, basic parameters of geochemistry, rock mineral

composition, and the like in key wells; (2) carry out gas desorption and

adsorption tests of cores in the field and calculate the isothermal adsorption

curves to gain the adsorbed capacity of shale in theory, which can determine

the gas saturation to calculate the content of adsorbed gas; (3) based on well

logging curves (calibrated by core data), an interpretation model can be

established via a core-logging comparison to gain gas saturation, water

saturation, oil saturation, porosity, organic matter abundance, rock types, and

so on; (4) boundaries of gas-bearing shale can be confirmed by sedimentary

facies, characteristics of rock assembly, and interpretation results of well


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logging; (5) economical evaluation can be carried out by 3D seismic data and

various parameters (such as original oil/gas in place, mineral composition,

fluid saturation, relative proportion between adsorbed gas and free gas, buried

depth, temperature, and pressure) to optimize exploration targets and to

determine the distribution scales of “sweet spots.”

6.2.1 Seismic evaluation

The shale gas presents the features of higher frequency, better continuity,

and medium-strong amplitude; (2) the seismic reflection structure of shale gas

is parallel to subparallel having mainly parallel sedimentation.

Fig 6.1 seismic response character


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Seismic sections showing signature of shale layers. a. Thick shales with thin

coal, limestone, silt etc. b. thin shales interbedded with coal, limestone,

sandstone etc. Both sections are flattened at upper sequence boundary.

6.2.2 LOGGING EVALUATION TECHNIQUES

Compared to normal shale, gas-bearing shale is characterized by enriched

organic matter and high gas-bearing

amounts. The development of clay and

organic matters decreases the formation

bulk density. So, the response of gas-

bearing shale in well-logging curves is

characterized by four high and two low

(high GR, high resistivity, high AC,

high neutron porosity, low density

logging, and low photoelectric effect

6.2


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6.2.3 EXPERIMENTAL ANALYSIS TECHNIQUE

Geochemical analysis of gas shale included the following: TOC

content of cores and debris samples;

Rock Eval pyrolysis analysis of cores and debris: measurement

of S1, S2, HI, Tmax; measurement of vitrinite reflectance (Ro) in

cores and debris; analysis on composition and carbon isotope of gas

samples. Testing of gas-bearing amount: First, seal the shale rock

samples in the metal desorption tank; and then heat it to the

formation temperature in a water bath to test the total gas-bearing

amount of the core.

Isotope Geochemistry: Genetic origin of natural gases and Thermal

maturity of natural gases: Maturity of source material, Onset of low-maturity

and high-maturity thermogenic gas generation, Recognition of gas leakage

and gas destruction (“preservation basement”) .Correlation of natural gases

with their sources.


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Chapter VII

Shale gas extraction

The fracturing treatment technique for the shale reservoir can improve the

production of shale gas substantially, which plays a determinative role in

commercial development of shale gas. Fracturing treatment techniques for the

shale reservoir mainly include foam fracturing and hydraulic fracturing

(including repetitive fracturing, multistage continuous tube fracturing, sliding

sleeve completion, and hydro jet fracturing and anhydrous fracturing [N2 and

CO2, liquefied oil and gas].).

An important characteristic of well production for shale gas is that it can

perform repetitive fracturing many times. Generally, after the primary

fracturing, open fractures, which were sustained by proppant, will gradually

close along with the time lapse and pressure release, leading to production

decrease to a large extent. Production can be recovered through repetitive

fracturing, where production after the second fracturing can be close to or

even over the production of primary fracturing. The recovery ratio, which is

estimated after the primary well completion, is usually about 10%. However,


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the recovery ratio can increase by 8%e10% after repetitive fracturing, and the

recoverable reserve can increase by 60%.

Fig 7.1 shale gas extraction


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Chapter VIII

8.1 Evaluation of Shale-Gas Resources, production (fig 8.1)

Fig 8.1

8.2 Shale Gas in EGYPT

Egypt has four basins in the western Desert with potential for shale gas

and shale oil Abu Gharadig, Alamein, Natrun and shoshan-Matruh fig 8.2 The

target horizon is the organic-rich Khatatba shale, sometimes referred to as the

kabrit shale or safa shale, within the large Middle Jurassic Khataba

Formation.


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Reserves in Egypt

Approximately 535 Tcf of Shale Gas in-place

Expected Recovery Factor is 20%

Recoverable Shale Gas is approximately100 Tcf


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https://www.futurelearn.com/profiles/367626

https://www.futurelearn.com/profiles/367553

https://www.futurelearn.com/courses/shale-gas