principles of petroleum geology m.m.badawy

3 Petroleum Geology, (M.M.Badawy)

Petroleum Geology


PETROLEUM GEOLOGY

Petroleum geology is the branch of economic geology that relates to theOrigin, Migration and Accumulation of oil and gas and to the Discovery ofcommercial deposits.

WHAT IS PETROLEUM?

• Legally, petroleum has been called a Mineral, but this usage does Not satisfythe common geologic definition of a mineral as an Inorganic substance.• It has also been called a Mineraloid, a term also applied to chalcedony andamber, on the ground that it is not definite enough in Chemical Composition.• It is frequently called Mineral Fuel, along with peat and coal.• Petroleum is a Fossil Fuel.

THE DEVELOPMENT OF PETROLEUM GEOLOGY:

• The Oil Seepages• The Anticlinal Theory• Subsurface Geology• Geophysics• New Methods


THE OIL SEEPAGES:

• The first petroleum fields were discovered Near oil seepages.• A petroleum seep Is a place where liquid or gaseous hydrocarbons escape

to the surface through fractures and fissures in the rock and betweengeological layers. Petroleum seeps Are quite common: California hasthousands of them. Much of the petroleum discovered in California during the19th century was from observations of seeps.

HOW OIL SEEP WAS FORMED?


THE ANTICLINAL THEORY:

• The theory was that because Oil is lighter than Water it would Seek theHighest part of an underground structural fold. Thus, an Anticline is amore Favorable place to Drill for oil than Syncline.

THE ANTICLINE TRAP:


SUBSURFACE GEOLOGY:

• The study of the information Revealed by the Boreholes already drilled andfrom the Study of the Sedimentary story as revealed in well and surfacesections showed that Oil Accumulations could be found by tracing Lateralchanges in rock composition, Locating breaks in deposition and other ways.Techniques for the presentation of structural and stratigraphical informationimproved greatly during this time.

GEOPHYSICS:

• The Torsion balance for gravity measurements had been introduced in 1920and the seismograph in 1923.• The Chief Advantage of the Geophysical Tools is that they Allow the

operator to “look” below breaks in the geological sequence, which Masksthe formations at depth from surface geological inspection.NEW METHODS:

BRIGHT SPOT:

• Since 1972, the application of Direct Hydrocarbon Detection by geophysicalmeans has forced geologists and geophysicists into each other disciplines.• It is one of the pattern classes in a seismic section and the indicators of Gas

(hydrocarbon) accumulation.

• Gas charged sand reservoirs gave High amplitude reflection or bright spot

• Because of the High reflection coefficient of the shale-gas sand-shalesequence, the limits of the gas field are Beautifully Described.


SEISMIC STRATIGRAPHY:

• It is the study of Stratigraphy and Depositional Facies as interpreted fromSeismic Data.

• The primary exploration Objectives in the Use of Seismic Stratigraphy is itsAssistance in the tracing of facies across wide areas.


WHAT IS PETROLEUM

Petro= Rock Oleum= Oil

Petroleum= Rock Oil

Petroleum is a complex mixture of Hydrocarbon (H, C) compound with minoramounts of Nitrogen, Oxygen and sulfur as impurities.Petroleum is a general term for all naturally occurring hydrocarbons present

in (liquid, Gaseous and Solid or Semisolid forms)

LIQUID PETROLEUM – Crude Oil

GASEOUS PETROLEUM – Natural gas or Light hydrocarbon (Methane,

Ethane, Butane...etc)

SOLID OR SEMISOLID PETROLEUM – Tar, Pitch, Asphalt


LIQUID PETROLEUM:

It is called crude oil to distinguish it from refined oil. Is the most important commercially. It consists of the liquid hydrocarbon with varying amount of dissolved gases,bitumen and impurities. Crude Oil is measured by:American Barrel = 42 American Gallons = 158.9 Liters Measured in France and Germany By:Cubic meters m3 = 6.28 Barrels

GASEOUS PETROLEUM:

It is called Natural Gas to distinguish it from Manufactured gas. It consists of the lighter paraffin hydrocarbon with the most abundant is the

Methane Gas (CH4).

Natural Gas is measured by:Cubic Feet or Thousand Cubic Feet


SOLID OR SEMISOLID PETROLEUM:

It is called Asphalt, Tar, and Pitch or by any one of many other termsdepending on their individual characteristics and local usage. Consists of heavy hydrocarbons and Bitumen(Liquid & Solid form of

Hydrocarbon)(Soluble Organic Matter)

Combustible Rocks Non-combustible Rocks Ex: Oil, Natural Gas, Coal, Oil Shale Ex: Shale Type of rocks which havea high amount of hydrocarbons

CAUSTOBIOLITHES

Caustic= Hot Bio= Life Litho= Stone

CAUSTOBIOLITHES & ACAUSTOBIOLITHES

CAUSTOBIOLITHES ACAUSTOBIOLITHES


Petroleum called a hydrocarbon is a Wrong name because it has anothercomponent like Oxygen, Nitrogen and sulfur.SAPROPEL OIL:

Generally like ose or slutch composed of plant remains where most ofalgae or petrifying in an aerobic environment on the shallow bottom oflakes and sea may be a source of petroleum and natural gas.

Mud rich with organic matter.


Element Crude Oil Asphalt Natural Gas KerogenCarbon 82-87 80-85 65-80 79

Hydrogen 11 - 14.0 8-11.0 1-25.0 6Sulfur 0.1-5.5 2-8.0 Trace-0.2 5

Nitrgen 0.1-1.5 0-2 1-15.0 2Oxygen 0.1-4.5 0-2 -- 8

CHEMICAL PROPERTIES OF PETROLEUM

1) Elemental composition2) Molecular size variation3) Hydrocarbon series4) The isotopes of some elements of petroleum5) The Correlation Index (C.I)6) Other constituents7) Miscellaneous substances

ELEMENTAL COMPOSITION

Petroleum is composed of C : H ( 1 : 1.85 ) (represented by~ 97%) The minor elements as Sulfur, Nitrogen, Oxygen (less than 3% of mostpetroleum) Traces of phosphorus and heavy metals such as: Vanadium and Nickel.

ELEMENTAL COMPOSITION OF NATURAL MATERIAL INPERCENTAGE:


With increasing the percentages of hydrogen, the specific gravity of the oil isdecrease.

Kerogen: Organic matter in sediments with insoluble in organic solvent. Bitumen: soluble organic matter.

MOLECULAR SIZE VARIATION

The elements Carbon and Hydrogen are combined as hydrocarbons that vary bothin:

The Size The Type of Molecules

Hydrocarbon form: Homologous Series, which about a family of molecules whosemembers have similar properties and different in size by a CH2 group.HYDROCARBON SERIES

There are four main hydrocarbon series differing in chemical properties andrelationships: Normal Paraffin (or, Alkenes) series Isoparaffin series (or, Branched Chain Paraffin) Naphthene (or, Cycloparaffin) series Aromatic (or, Benzene) series


PARAFFIN (ALKANE) SERIES:

They are the second most common constituents of crude oil next tonaphthenes. Paraffin’s dominate the gasoline fraction of crude oil. They are the principle hydrocarbons in the oldest, most deeply reservoirsParaffins increase in the oldest reservoirsParaffins decrease in the youngest reservoirs The paraffin series of hydrocarbon is a saturated straight chain (Aliphatic) General Composition (CnH2n+2)

NAPHTHENE (CYCLOPARAFFIN) SERIES:

The most common molecular structure in petroleum. The cycloparaffin formed by joining the carbon atoms in a ring. The napthene of hydrocarbon series is a saturated (single covalent bond)homologous, closed-ring series. General Composition (formula) (CnH2n) Cyclopentane (C5H10) and cyclohexane (C6H12) are the chief member of thenaphthene series found in petroleum. Cyclopropane (C3H6) and methyl cyclopropane (C4H8) are gases at ordinaryTemperature and Pressure, But All the other monocyclic are Liquid.


AROMATIC (BENZENE) SERIES:

The aromatic series of hydrocarbon named with this name because many ofthis members have a strong aromatic odor. Is an unsaturated closed ring (carboxylic) series. General Formula (CnH2n-6). Benzene (C6H6): a colorless and volatile liquid, the paint and most commonmember of this series. Aromatic are present in all petroleum but the percentage is small.

Graphical methods of representation the constituents of crude oil:

Decrease According To Abundant

Naphthenic

Paraffin’s

AsphalticAromatic

Petroleum

Aromatic (small %)Paraffinic (secondmost common)

Naphthenic

(Most common)


THE ISOTOPES OF SOME ELEMENTS OF PETROLEUM

• Isotopes have the same atomic number, but they have different atomicweight. It is distinguished stable and unstable isotopes. Non-stable isotopescan spontaneously disintegrate with formation of new atoms with anothernumbers of protons.

• In petroleum geology, it is widely using data of studies of isotopes of carbon,hydrogen, sulfur and other elements to solve problems of genesis of oil andgas.

THE CARBON ISOTOPES:

• Carbon has three isotopes 12C, 13C and 14C. All carbon atoms have six protonsbut there are three carbon isotopes containing six, seven and eightneutrons, giving atomic masses 12, 13 and 14 respectively.

• 12C and 13C are stable isotopes and the original forms of carbon in the earth.Stable isotopes are useful, because the proportion of two isotopes of eachelement vary from sample to sample as a result of isotope effects.


THE CARBON ISOTOPES:

• The distribution of these three isotopes in the biosphere is as follows:

14C AGE DATING:

• 14C is an unstable isotope and is formed from the bombardment ofatmospheric nitrogen with neutrons produced by cosmic radiation andenters the biosphere as CO2.

• The 14C decays to 14N. One neutron in a 14C atom spontaneously decays,giving off an electron (β-particle) and leaving a new proton (p).

• This produces 14N, since nitrogen atoms have seven protons in their nuclei.The reaction is:• 14C (6p + 8n) - β→14N (7p + 7n)


14C AND AGE DATING:

• A mass of 14C atoms disintegrates at a fixed rate such that half of the mass ischanged from carbon to nitrogen in 5,570 years (the half-life period of14C). Consequently, the age of a carbon containing substance can bedetermined by measuring its output of β – particles.

• The technique is only good for about five half live periods (30,000 years),because β – particle emission becomes too low in older materials todistinguish from background noise.

13C CAN SOLVE MANY GEOCHEMICAL PROBLEMS:

• The 13C isotope is distributed through sediments of all geologic ages, incontrast to 14C, which is limited to very young sediments.

• The difference in mass of 13C relative to 12C result in fractionation bybiological and physical processes.

• The heavy isotopes form stronger bonds than light isotopes. Thispreference causes separation of heavy and light isotopes at equilibrium.• For example, in the oceans CO2 is in equilibrium with various carbonate

species.


HOW CAN 13C SOLVE MANY GEOCHEMICAL PROBLEMS?

• CO2 + H2O →CO2-- + 2H+

ENRICHED IN 12C ENRICHED IN 13C

• The ratio of 13C (heavy isotope) to 12C(light isotope) is determined on anisotope ratio mass spectrometer.

• The ratio difference δ 13C = [(13C /12C sample)/ (13C /12C standard) - 1] x1000 in 0/00 relative to standard

• The standard that has been used most widely in the literature over the yearsis a belemnite from the Pedee Formation in South Carolina (PDB).THE FOLLOWING TABLE SHOWS THE VARIATION IN 13C IN SOME NATURALMATERIAL:


THE ISOTOPES OF OTHER ELEMENTS:


CORRELATION INDEX

This correlation index is useful in classifying the oil as a qualitative. The correlation index: Is a number of a magnitude indicates certaincharacteristics of the crude oil distillation fraction. The paraffin give a C.I of Zero & benzene is about 100

The lowr C.I value of analysis fraction, the greater concentration of paraffinhydrocarbon in fraction. The higher C.I value, the greater concentration of Naphthenic and

Aromatic hydrocarbon.Smith Equation:C.I = (48640/K) + (473.7G)-456.8Where:K = the average Boiling Point of the fraction in 0KG = Specific Gravity of the fraction at 600F

المضاھاهدلیل

...عبارة عن نسبة وتناسب بین مكونات البترول حسب اكبر نسبة للتواجد حسب الترتیب


OTHER CONSTITUENTS

Sulfur:

(0.1-5.5)% in crude oil. The presence of sulfur and sulfur compounds in gasoline causes: (corrosion –bad odor – poor explosion)

تواجد السلفر یقلل من جودة البترول ویعتبر من المواد غیر الرغوب فیھا

The percentage of Sulfur:Sulfur, Low Crude Oil called: SweatSulfur, High Crude Oil called: Sour

Note:- With increasing of Sulfur, specific gravity of oil increase (Bad Thing)- With increasing of Hydrogen, specific gravity decrease (Good Thing)Nitrogen:

(0.1-1.5)% in crude oil. All crude oil contain small quantities of nitrogen. Nitrogen is a common constituents of natural gas (1-15)%

Nitrogen which exists in crude oil may be existing in dissolved gases. Nitrogen is an unwanted component of both crude oil & Natural Gas.


Oxygen:

(0.1-4)% in crude oil Oxygen occur in various forms:- Free oxygen- Phenols (C6H5OH)- Fatty acids- Naphthenic acids (CnH2n-1.CooH)- Asphalt Substances

MISCELLANEOUS SUBSTANCES

Crude oil contains minute amount of a wide variety of miscellaneouscomponents. Some organic and some of inorganic

Organic materials:

Are seen under microscope Includes:- Siliceous skeletal test- Petrified wood fragments- Spores – coal- Lignite fragments (Coal type)- Algae and unicellular organism


Inorganic materials:

May observe in the ash (Oil burning) Elements that have been identified in crude oil ash include:

(Si – Fe – Al – Ca – Mg – Cu – Pb – Tin – Arsenic – Antimony – Zn – Ag – Cr –Molybdenum – Ni – V)

Nickel and Vanadium: are concentrated in porphyrins and replace themagnesium in chlorophyll. Ni & V: are very important, because the Ni/V ration in crude oil is greater

than in the earth’s crust, so they are using to correlate crude oils and the

oil to source rock place.

Porphyrins: large complex of N, S, O compounds derived from chlorophyll,which used as a biomarker in the indication of the origin of the oil and thesource rock.


PHYSICAL PROPERTIES OF PETROLEUM

• They allow determining their commercial quality. Some parameters areusing for estimating and planning of the exploitation of oil fields, thetransporting and others.

• Many problems of the geological history of petroleum are determined withdata obtained from measuring the physical parameters of oils and itsvariations with depths in the sections and along the area of oil province.

THE DENSITY AND SPECIFIC GRAVITY:

• The density of substance is the weight of a given volume.• A convenient method of expressing the same physical property is the

specific gravity in which no units of measurements need to specify.• Specific gravity is the ratio of the weights of equal volumes of the

substance and pure water at certain temperature and pressure.( Unitless)

Weight per volume

Unit: (gm/cm3)


The API GRAVITY:

• The API gravity scale is an arbitrary one, which has the advantage thesimplifying the construction of (hydrometers), because it enables the stemsto be calibrated linearly.

• API gravity does not have a straight-line relationship with specific gravity,nor with the other physical properties correlated with specific gravity such asviscosity.

• High values of API gravity correspond to low specific gravity. A similar scaleis the European Baume´ gravity scale.

HOW TO CALCULATE DEGREES API?

American Petroleum Institute (Degreesof Gravity)

specific gravityجھاز بیقیس ال


• 10° API is equivalent to a specific gravity of one.• The specific gravity of crude petroleum ranges from 0.7 (API 70.6°) for very

light crude oils, up to more than one (API 10°) for some solid bitumen.

• Most crude oils are being in range of 0.82 (API 41°) to 0.87 (API 31°).• The gravity of two crude oils may differ considerably even though the oilsseem related closely.• There may be a difference in gravity between oils in adjacent reservoirswithin the same field or geologic environment, between oils in the same

reservoir rocks but in separate traps, and between oils within the same

reservoir but of differing structural position.

BOILING POINT:

• Oil consists of a closely related series of complex hydrocarbon compoundsthat range from gasoline to heavy solids. The various mixtures thatconstitute crude oil can be separated by distillation under increasing

temperature into such components as (from light to heavy) gasoline,

kerosene, gas oil, lubricating oil, residual fuel oil, bitumen, and paraffin.

High (API) ….. Low (Specific gravity) …. (Good Type) High Paraffin

Low (API) …… High Specific gravity …. (Less Type) High Naphthenic & Aromatic


BOILING POINT:

• The boiling points of hydrocarbons are depending on their compositions. Themore carbon atoms in the molecular structures of hydrocarbons are thehigher boiling temperature. The naphthenic and aromatic hydrocarbons,in which carbon atoms are linking in rings, have boiling temperatures higherthan paraffinic hydrocarbons with the same numbers of carbon atoms.

CLOUD AND POUR POINTS OF PETROLEUM:

• The cloud point is the temperature at which the first cloud appears in oil. Itis due to the settling out of solid paraffin wax; wax-free naphthenic oilsshow no cloud point.

• The pour point—the temperature below which crude oil becomes plasticand will not flow—is important to recovery and transport and is alwaysdetermined. Pour points range from 32° C to below -57° C.

ي المواسیردرجة االنسكاب او التعكر ویت حسابھا حتي ال یتجمد البترول في نقلة ف


VISCOSITY:

• It is an inverse measure of the ability of a substance to flow, the greaterthe viscosity of a fluid, the less readily it flows.• Crude oils vary greatly in viscosity. Some, such as natural gas and light oils

are very mobile. Others are highly viscous and these grade into thesemisolid petroleum, although the latter are more strictly speaking plastic.

• Viscosities vary directly with the composition. the greater the number ofcarbon atoms in a member of a hydrocarbon series, the greater will be itsviscosity

SURFACE TENSION:

• It is the force necessary to increase the free surface of certain liquid byone square centimeter, without changing temperature of the liquid(Unit dyne /cm2).

• Surface tension results from the action of molecular force, which differsfrom one liquid to another. The force of cohesion of molecules of liquid withhard body may exceed the force of cohesion between the molecules ofliquid.


OPTICAL ACTIVITY:

• It is the power to rotate the plane of polarized light. This is measured witha polariscope in degrees per millimeter, and the average range is from 0 to1.2 degrees (almost to the right i.e. dextrorotary).

• All crudes either are optically active or contain optically active distillationfractions, particularly in the intermediate range (250-300° ).

WHY THE ORGANIC SUBSTANCES HAVE OPTICAL ACTIVITY?

• It is thought that optical rotary power is confined to organic substance.Cholestrin (cholesterol), which is alcohol with the formula (C26 H45 OH), isfound in both vegetable and animal matter and it is a constituent of newmilk from fresh cattle.

• Optical activity is commonly given as an argument for the origin ofpetroleum from plant or animal remains, because as far as we know,optical active oils cannot be synthesized inorganically.


COLOR:

• The color of petroleum by transmitted light varies from light yellow to red;some very dark or black oils are opaque. The higher the specific gravity (or

low the API gravity), is the darker the oil.• The cause of the color is not known, but it is thought to be related to the

aromatic series of compounds. By reflected light, the crude oil is usuallygreen because of its fluorescence.

LUMINESCENCE AND FLUORESCENCE:

• Luminescence is the emission of light by some oils that have receivedenergy.

• Fluorescence is a type of luminescence. All oils exhibit more or lessfluorescence, the aromatic oils being the most fluorescent. The fluorescentcolors of crude oils range continuously from yellow through green to blue.This property is used in the logging of wells to locate oil showing in the coreand cutting samples and drilling mud.

• Fluorescence is rapidly reduced by aging, so that fresh oil is easilydistinguished from oil previously caught in the drilling mud. Fluorescence isobserved under ultraviolet radiation


ELECTRICAL PROPERTIES:

• Oils are dielectric, so the electrical methods are using for discovering oil-bearing beds in the well.COMBUSTION HEAT:

• Oils have exceptionally high combustion heat. The data of combustion heat ofcoal, oil and gas are as follows in joules/kg• Coal 33600• Oil 43250-45500• Natural gas 37700-56600

FLASH AND BURNING POINTS:

• The flash point is the temperature at which the vapors rising off thesurface of the heated oil will ignite with a flash of very short durationwhen a flame is passed over the surface. When the oil is heated to a highertemperature, it will ignite and burn with a steady flame at the surface.

• The lowest temperature at which this will occur is known as (the burningpoint). These measurements are a measure of the risk involved in handlingand storing petroleum and petroleum products, and state law generally fixestheir limits.


REFRACTIVE INDEX:

• The absolute Refractive Index (RI) of a substance is the inverse ratio of thespeed of light in that substance to its speed in a vacuum.

• The refractive index is defined as the ratio of the sine of the angle ofincidence to the sine of angle of refraction; both angles are beingdetermined with respect to a normal to the surface.


THE ORIGIN OF PETROLEUM

• This problem has puzzled geologists for a long time.• Many theories have been proposed to explain the origin of petroleum, but nonehas proved to be convincing.• In general, the (Early theories) were based on laboratory experiments thatattempt to simulate field conditions.• The more (Recent theories) are based on modern analytical method,especially carbon isotope geochemistry.• Theories of the origin of petroleum may be divided into two groups accordingto their view of the primary source material as (organic) or as (inorganic).• Early ideas have tendency toward the inorganic source, where as the

modern theories assume that the primary source material was organic.

• The theory of origin has a bearing on the method of exploration.


THE GEOLOGIC FENCE OF ORIGIN OF PETROLEUM

LIMITING CONDITION OF ORIGIN OF PETROLEUM

All hydrocarbons occur in sediments of marine and continental origin. Petroleum is extremely complex mixture of many hydrocarbons. No twocrudes are similar; however the elemental chemical analyses are similar. Petroleum is formed in rocks from the Precambrian to the Pleistocene,although the occurrences in some ages are anomalous.

Upper Jurassic shale's dominate as a source rock in the Northwest Europeansedimentary basins and as much as 25% of the world’s hydrocarbons may comefrom this interval.The type locality of the Kimmeridge Clay Formation is along the Dorset coast ofEngland.

Until the advent of chromatographic and similar tools, no bitumen had beenfound in (shale's and carbonates). Insoluble organic matter (kerogen) wasfound in the sediments. The temperatures of petroleum reservoirs range from 1070C in some deeperreservoirs. The presence of porphyrins in some hydrocarbons indicates thatsuch crude oils have never exceeded 2000C, for porphyrins are destroyed atlower temperature.


Porphyrins: Large, complex N,S,O compounds derived from chlorophyll andrelated molecules. There exist several homologous series of porphyrins thatcan be useful as biomarkers.

Biomarkers (Chemo fossils): Chemical compounds derived from specificbiological precursors. They used as environmental and maturity indicators. Anaerobes: They are organisms (esp. bacteria) that can live in the absence offree oxygen OR they are sediments that exist only in the absence of freeoxygen. The origin of petroleum is within an anaerobic and reducing e environment.The presence of porphyrins means anaerobic conditions developed early inlife of petroleum. No differences have been observed between oil pools formed due to

migration and that have not affected by migration. The time required to form petroleum and concentrate it into pools is probablyless than one million years.


INORGANIC OR ABIOGENIC PETROLEUM ORIGIN

A small number of geologists adhere to the A biogenic petroleum originhypothesis and maintain that hydrocarbons of purely inorganic origin existwithin Earth's interior. Chemists Marceline Berthelot and Dmitri Mendeleev, as well asastronomer Thomas Gold championed the theory of a biogenic origin. Carbide Hypothesis: It assumes that deep in the earth exist metal carbidesthat form hydrocarbons on contact with hydrothermal solutions.Fe C2 + 2H2O →HC CH + Fe (OH)2Iron Carbide AcetyleneAt elevated temperatures, the acetylene polymerizes to form benzene. Cosomic Hypothesis: Hydrocarbons were present in the earth’satmosphere when it was in molten form. As a result of solidification of theearth, the hydrocarbons were condensed and accumulated in the earthcrust.


Really methane is proved to exist in the atmosphere of some planets, butthe existence of more complex hydrocarbons in thermodynamic conditionsof firely liquid substance is impossible.

The Abiogenic origin hypothesis has not yet been ruled out. Its advocatesconsider that it is "still an open question”. Extensive research into the chemical structure of kerogen has identified

algae as the primary source of oil. The lack association of petroleum with volcanism. The Abiogenic origin hypothesis fails to explain the presence of thesemarkers in kerogen and oil, as well as failing to explain how inorganic

origin could be achieved at temperatures and pressures sufficient toconvert kerogen to graphite.

It has not been successfully used in uncovering oil deposits by geologists, asthe hypothesis lacks any mechanism for determining where the processmay occur. More recently scientists have found that ethane and heavier hydrocarbonscan be synthesized under conditions of the upper mantle.


ORGANIC OR BIOGENIC ORIGIN OF PETROLEUM

According to generally accepted theory, petroleum is derived from ancientbiomass.

It is a fossil fuel derived from ancient fossilized organic materials. Thetheory was initially based on the isolation of molecules from petroleum thatclosely resemble known bio molecules. Structure of vanadium porphyrin compound extracted from petroleum byAlfred Treibs, father of organic geochemistry. Treibs noted the closestructural similarity of this molecule and chlorophyll a


MOLECULAR STRUCTURES OF LIVING ORGANISMS:

All living things are formed from a few simple, molecular building blocks that havechanged relatively over geologic time.• Carbohydrates: (They are not the important sources of the petroleum,collective name for sugars and their polymers)• Proteins: (They are high order polymers from individual amino acids andaccount for the most of N,S components in organisms)• Lipids: (Are one of the main sources of petroleum, These cover all organismsproduced substances that are insoluble in water, as: Fats, Vegetable Oil,Waxes)• Lignin and Tannin:

(Both are characterized by aromatic structures. They are common in planttissues).(The aromatic content of petroleum is derived from Lignin and Tannin)

(Characterized by their aromatic structure, (Phenol))


THE RATIO OF CARBON ATOM TO THE N, S, AND O ATOMS:

AVERAGE CHEMICAL COMPOSITION OF LIFE SUBSTANCES:


COMPOSITION OF LIVING MATTER:

WHAT IS THE MOST IMPORTANT PROGENITOR OF PETROLEUM?

• The lipids content of all forms of organic matter is more than enough toaccount for the origin of petroleum.• It is shown that less than 1% of the organic matter in sediments is required toform all the known petroleum.• Lipids are more resistant to degradation in a reducing environment than

proteins and carbohydrates.• Lipids may be the most important progenitors of petroleum


Diagenesis Catagenesis Metagenesis

MATURATION OF ORGANIC MATTER

DIAGENESIS OF ORGANIC MATTER:

It is the process of biological, physical and chemical alteration of the organicmatter before a pronounced effect of temperature. Covering the temperature range from surface (250c) to about (500c). When organisms die, their organic matter undergoes a variety of reactions.

Some micro biological: such as the formation by anaerobes.Some physical and chemical: such as dehydration and oxidation.

The combined attack of weathering and microbes convert much of organicmatter either to gases that escape into atmosphere or to soluble products thatare carried by ground water.Note: Environments that preserve large amount of organic matter in the sedimentsare stagnant lakes and sill basins where the bottom waters are strongly reducing.Examples:

Black sea (organic content of the sediment exceeds 15%. Red clay of oceanic abyssal plaints (where slow rates of deposition, aerobicwaters so little organic matter result in sedimentary organic contents of lessthan 0.1%


Oil is formed from organic matter deposited in the aerobic waters ofsedimentary basins, where the water occasionally may be anaerobic but thesediments are nearly always anaerobic. As (the formed in aerobic conditionand reducing environment) The more resistant organic matter including: (humid materials, resins, waxes,lipids) The organic content of such sediments with mean source beds of petroleum.(ranges between (0.5 – 5) % with mean around 1.5%

Note:Major source rock in age of Cretaceous (organic rich mud sediments)Organic matter occurs with burial at depth range where temperatures are too low forcracking of large molecule to occur.The organic matter deposited in sediments consists primarily of the biopolymers ofliving organisms. (As, carbohydrates, protein, lipids, lignin and subgroups such aswaxes, fats ….. etc)

If we will say the source rock it must has an organic matter percentage of (0.1 to 1.5)% so, Red sea or Red clay does not called a source rock


Notes:

Polymers: A large molecule consists of many small subunits. Biopolymers: polymers created by enzymes, they have very regular

structure. Geopolymers: polymers formed in the geosphere as the result of chemicalcombination of small molecules, they have irregular structure, and they arenot susceptible to microbe attack.


CATAGENESIS OF ORGANIC MTTER

It is the process by which organic matter is altered due to the effect ofincreasing temperature (50-200)0c.

The compaction of sedimentary basins causes the organic matrix to besubjected to increase at higher temperature with greater depth of burial. In a reducing environment: This increasing the temperature causes thethermal degradation of kerogen and associated organic compound to formpetroleum range hydrocarbons. The Term of catagenesis was proposed by (Vassoevich 1959) Temperature may range from (50-200)0c Geostatic pressure due to overburden may vary from (300-1500) bars. Depth of oil window (1.5-7.5) Km.


During catagenesis composition and texture of the mineral phases are conservedwith some changes mostly in clay fraction, the main inorganic modification stillconcerns the compaction of the rock:

Water continues to expel. Porosity and permeability decreases. Salinity of interstitial water increases and may come close to saturation.

Changes of organic matter:

Through progressive evolution the kerogen produces first liquid petroleumthen in later stage (wet gas) and condensate, are accompanied by significantamount of methane. The end of catagenesis is reached in the range where the disappearance ofaliphatic carbon chains in kerogen completed and where the development ofan ordering of basic kerogen units begins. This corresponds to (Vitrinite Reflectance of about 2), which according tovarious coal classifications is approximately the beginning of anthracite ranks.(Vitrinite is a type of coal which can detect the paleotemperature by

knowing the temperature)


METAGENESIS OF ORGANIC MATTER:

The last stage of the evolution of sediments with is known as metamorphismand is reached in deep troughs and in geosynclinals zones. Petroleum geology is only concerned with this stage as metagenesis of organicmatter. Minerals are transformed under those conditions and lose their interlayerwater and gain a higher stage of crystalline:(Iron oxide with water ----------- Iron oxide without water)(Goethite) (Hematite) The rock reaches temperature conditions that leads to the metagenesis oforganic matter, (organic matter is composed only of methane and a carbon

residue) Temperature range (200-300)0c


TIME AND TEMPERATURE IN ORIGIN OF PETROLEUM

The rates of chemical reaction are affected by temperature(Temp-increase …………… Reaction rate-increase) Increases in temperature of 100c can double the reaction rate. The relation between temperature and reaction rate is expressed by:(Arrhenius equation)Where: K = A e-(Ea/RT)

K = the reaction rate constant related to change in concentration of parentsubstance with change in time;A = frequency factor;Ea = activation energyR = gas constant;T = temperature in degrees KelvinThe A factor is a constant representing the frequency with which moleculescollide in a proper orientation to enable a reaction to occur. The activation energy(Ea) is the amount of energy that must be absorbed by a molecule or molecularcomplex to break the bonds and form new products. Maturation of organic matter depends on Time and Temperature. There are limits for time and temperature at petroleum is formed in economicquantities. Each source rock forms oil and gas at different rate with increasingtemperature is depending on:

o It’s content of the various types of kerogen.o The possible catalytic of its mineral constituents.


OIL WINDOW OR THE PRINCIPLE PHASE OF OIL GENERATION

Oil Window: (Interval)

The depth interval in which a petroleum source rock generates and expelsmost of its oil. OR, it’s a vertical representation of the generative interval.

Hydrocarbon Kitchen: (Area)

The area that supplied the hydrocarbon for these respective structure, andconceder the deepest place in the basin (source rock) (Pod of active source)(center of the basin).SIGNIFICANCE OF OIL WINDOW:

Exploration geologists can predict the probability of oil and gas in sedimentarybasin. Oil is not generated in young-cold basin, because temperature are not highenough to indicate the threshold of intense oil generation (limit interval

between Dia and Cata, Cannon 1974). No hydrocarbons are being generated in old-hot basins, because they are

destroyed. The places to prospect are the (young-hot) or (old-cold) basins


SOME MOLECULES STRUCTURES:


FORMS OF HYDROCARBONS:

Dry gas- contains largely from >99.9% methane gas. Wet gas- contains methane with contributions from ethane propane, butanewith minor constituents from pentane gas. Condesates- Hydrocarbon with a molecular weight such that they are gas inthe subsurface where temperatures are high, but condence to liquid whenreach cooler to the surface temperatures. Liquid hydrocarbons- commonly known as oil or crude oil. Plastic hydrocarbons- asphalt Solid hydrocarbons- coal and kerogen- (kerogen strictly defined isdisseminated organic matter in sediments that is insoluble in organic solvents. Gas hydrates- Solids composed of water molecules surrounding gasmolecules, usually methane, but also H2S, CO2, and other less common gases.


Brent Crude Oil:Is a major trading classification of sweet, light crude oil that serves as a majorbenchmark price for purchases of oil worldwide. The Brent Crude oil marker is alsoknown as Brent Blend.بیة واألفریقیة, خاصة في األسواق األوروخام برنت ھو خام نفطي یستخدم كمعیار لتسعیر ثلثي إنتاج النفط العالمي

ویعتبر من أنواع النفط الخفیفة الحلوة بسبب وزنھ النوعي بسبب انخفاض نسبة الكبریت فیھ.


Three studies showing the distribution of the world’s oil source rocks in thestratigraphic record:


The distribution of the world’s oil and gas source rocks in the stratigraphicrecord:


OIL & GASACCUMULATION


PETROLEUM SYSTEM ELEMENTS

There are FOUR necessary elements to form an oil and gas accumulations:

GENERATION MIGRATION PATHWAYS ACCUMULATION TRAPPING AND SEALING MECHANISM

RESERVOIR ROCK

Reservoir rock is a rock that can store and transmit the accumulated hydrocarbons.These rocks made mainly of porous and permeable sandstone, limestone ordolomite. The hydrocarbons are situated in the void spaces or the connected poresbetween the grains.RESERVOIR TRAPS

RESERVOIR TRAP consists of an impervious stratum that overlies the reservoir rockthat prohibiting hydrocarbons from escaping upward and laterally. This imperviousstratum is called a roof rock (CAP ROCK). The roof forms a seal, or a barrier, whichcreates the needed conditions for a pool. Trap material must have a lowerpermeability than the existing rock material though which the hydrocarbons areflowing.


SEALING ROCK

A type of rock adjoining the reservoir rock that restricts the leakage of hydrocarbonsfrom a trap after it has been accumulated.


HYDROCARBON RESERVOIR TRAPS

There are three basic types of hydrocarbon traps depending on the elements ofentrapments according to the classification proposed by Levorsen (1967): Structural Reservoir Traps Stratigraphic Reservoir Traps Combination

STRUCTURAL RESERVOIR TRAPS

They are formed by tectonic processes AFTER deposition of the reservoir beds.There are THREE types of structural traps:1. Folded Reservoir Traps: resulted due to bending (deformation) of the rock unitswithout breaking. The simplest form is the domal or anticlinal structure creatinganticlinal traps2. Faulted Reservoir Traps: These are the result of fracturing (breaking down)within the rock units where one side has moved relative to the other side. Faultingmay be the sole cause of the formation of this type of trap.3. Folded - Faulted Reservoir Traps: Faulting may be combined with otherstructural features such as folding.4. Fractured Reservoir Traps: Crystalline carbonate rock (Limestone) with nonrecognizable texture of interlocking crystals of calcite giving fracturing upondolomitization. These fractures increase the original porosity and permeability of thecarbonate rocks (limestone or dolomite) and become an excellent trap for oil and gasaccumulations.


STRATIGRAPHIC RESERVOIR TRAPS

They are created when a change in lithology or lithofacies (which also controlsporosity and permeability), DURING or AFTER the deposition of reservoir beds.1. Primary Stratigraphic Traps :Traps are formed DURING the deposition of the reservoir beds as:(1) Sandstone Lenses (2) Channel Fillings(3) Offshore Sand Bars(4) Coral Reefs (Bioherms and Biostromes)


2. Secondary Stratigraphic Traps :

Traps are formed AFTER the deposition of the reservoir beds (traps associated byUnconformities)• Angular Unconformity• Nonconformity• Disconformities


COMBINATION TRAPS

The geometry of the combined trap is the result of a combination of TECTONICPROCESSES and change in LITHOLOGY (porosity and permeability). An example of acombination trap is a salt dome.The salt dome is a mass of rock salts (Gypsum or Anhydrite) generally of a diameterabout 2 km near the surface. This mass of salt has pushed upward through thesurrounding rock and sediments into its present position. Salt beds were formed bythe natural evaporation of sea water from semi closed to closed basins.Origin of Salt Dome Traps (diapers) :

The origin of salt domes is best explained by NETTLETON (PLASTIC FLOWTHEORY). Salt has a density of 2.2 gm/cm3 under standard conditions. But at a depthof about 12,000 feet, the mass of the overlying sediments exerts a compressive,downward force, density decreases and salt begins to flow like a plastic substance. Asmall fracture in the overlying, higher density sediments (PIERCEMENT SALTDOMES) or a slightly bending of the overlying (NONPIERCEMENT SALT DOMES).


RESERVOIR PETROPHYSICS

The fundamental property of a reservoir rock is its porosity and permeability. BothPOROSITY and PERMEABILITY are geometric properties of a rock and both are theresult of its litho logic composition.POROSITY:

• Total Porosity: is the percent of the total pore spaces between the rock grains(Connected + Unconnected (T %) .• Effective Porosity: is the percent of the connected pore spaces between therock grains (E %) .


Factors Affecting Porosity:

• Grain Size of Rock Materials• Pattern Arrangement1. Cubic Packing (E %)=47.6%2. Rhombohedral Packing(E %)=25.9%• Grain Shape and Sorting

Reservoir classification depending effective porosity:

• Effective Porosity (E) >15% (Reservoir of Great Capacity)• Effective Porosity (E) 5-15% ( Reservoir of Average Capacity)• Effective Porosity (E) <5% (Reservoir of Low Capacity)


PERMEABILITY

• The ability, or measurement of a rock's ability to transmit fluids, typicallymeasured in (darcies or millidarcies). Formations that transmit fluids readily,such as sandstones are described as permeable and tend to have many large,well-connected pores.• Impermeable formations, such as shales and siltstones, tend to be finer grainedor of a mixed grain size, with smaller, fewer, or less interconnected pores.• Good reservoir rocks have both good porosity and good permeability.

Reservoir classification depending Permeability:

• Permeability >1 Darcy (Reservoir of Excellent Permeability)• Permeability 0.1-1 Darcy (Reservoir of Good Permeability)• Permeability 0.01-0.1 Darcy (Reservoir of Average Permeability)• Permeability <0.001 Darcy (Reservoir of Negligible Permeability)

BARREN TRAPS

• Traps are formed after the migration of hydrocarbons• There is no source rocks in the basin• There is no sealing mechanism• Deformation of traps due to the rejuvenation of the tectonic earth movement.


RESERVOIR DYNAMICS

Oil and gas accumulations in the reservoir traps are affected by two importantfactors and considered the most important sources of reservoir energy which makethe reservoir in a dynamic state: Pressure Temperature

RESERVOIR PRESSURE:


SOURCES OF ABNORMAL PRESSURE:

1. Rapid geologic loading (deposition) or unloading (erosion), it means the pressureresulted from the rock overburden.2. Vertical and side sealing of reservoirs.3. Earthquakes.4. Regional compressive (squeezing) or tensile (stretching) tectonic stresses.5. Pressure of ground water flow (Fluid Flow).6. Osmotic Pressure.7. Cementation and Dissolution.


RESERVOIR TEMPERATURE

It is well known that the oil generation window conditions are usually takes place atdepth ranges between (2.5 to 6.5) km that equivalent to temperature of (60 to160)oC.


SOURCES OF TEMPERATURE:

1. Magmatic eruptions.2. Heat of radioactivity.3. Heat conductivity of minerals and rocks.4. Increasing the depth of burial (Overburden).

Effect of Temperature on Reservoir Dynamics:

Increasing of temperature lead to decreasing the oil viscosity Increasing of temperature lead to increasing the volume of oil and gasaccording to Charl,s Law Vtc= (1/273)Vo Increasing of temperature lead to increasing the pressure of fluids especially(oil and gas) in reservoir. Increasing of temperature lead to decreasing the gas solubility in oils andconsequently the formation of free gas cap. Increasing of temperature lead to increasing the solubility of salts in formationwater lead to good separation of oil and formation water.


CRUDE OIL RECOVERY

Oil Recovery is classified into THREE types:Primary recovery:This type depends ONLY the using of natural energy of reservoirs, typicallyrecovers up to 50% of oil in Place through:

- Free Gas Cap Drive

- Water-Gas drive (Combination Drive)

- Formation Water Drive

- Gas Lift


Secondary Recovery:

Involves ADDING energy to the natural system by injecting water or gas tomaintain pressure and displace oil. Typical recoveries are 25-45% Oil in Place afterprimary recovery through: Injected water or CO2 to displace hydrocarbons. Pumping (Suck erode Pumping or Submericible Pumping)


Tertiary recovery:

Includes all other methods used to increase the amount of oil recovered. Typicalrecoveries are 5-20% of oil in place after primary and secondary recoveryChemical injection (HCl), Thermal injection (steam) and Solvent injectionMaximum Efficient Rate (MER):It is the maximum rate at which a well or field can be produced without loss ofreservoir energy or leaving bypassed oil in the reservoirProductivity Index (PI):It is the number of daily barrels produced every pound/square inch from thepressure of reservoir


STAGES OF PROSPECTION AND EXPLORATION FOR OILAND GAS DEPOSITS

Successful oil and gas exploration and development generally progresses throughFIVE basic operational phases include:(PHASE 1): PRELIMINARY (GEOLOGIC) INVESTIGATIONS:

The geological investigation method depends mainly on remote sensing, aerial andsatellite photographs and the mapping of outcrop rocks in addition to the oil seepagethat can give indications of the presence of subsurface oil and gas accumulations.This phase includes: Reconnaissance Survey by using large scale maps (1:1,000,000) Detailed Survey by using small scale maps (1: 1000)This phase aims to exclude the litho logic basement outcrops or thinsedimentary cover, identifying the target area and the road and buildingconstructions.


(PHASE 2): GEOPHYSICAL INVESTIGATIONS:

Gravity Surveys is used to detect the variations in gravity caused by the differencesin the density between the basement (Igneous and Metamorphic) and sedimentaryrock types.Seismic Reflection Survey is the most common indirect method used for locatingsubsurface structures that may contain oil and gas deposits.Shock waves are induced into the earth using one of several methods. These wavestravel downward and outward encountering various strata, each having a differentseismic velocity. Sensing devices called geophones are placed on the surface to detectthese reflections. The geophones are connected to a data recorder, which stores thedata.


(PHASE 3): EXPLORATION DRILLING:

1. The site of the first exploratory well is determined based on the existing stateof knowledge of underground conditions and the topography of the terrain.This is generally sited vertically above the thickest part of the stratum thoughtto contain hydrocarbons. This narrow-bore hole (with a diameter of 20-50centimeters) is generally sunk to a depth of between 2,000 and 4,000 meters. Itmay go beyond 6,000 meters.2. The presence of suspected oil and gas deposits may be confirmed byexploratory (wildcat) drilling of deep holes.

There are THREE systems for exploration drilling:1: Profile Drilling

2: Triangulation Drilling

3: Radial Drilling


(PHASE 4) FIELD DEVELOPMENT & PRODUCTION DRILLING:

After the completion of the first exploratory well (wildcat well) as a commercialproducer marks the beginning of the development of an oil and gas field.A Field Development Plan consists of a coordinated collection of sufficientinformation about the development of the field. Sufficient information may not beavailable until one or more confirmation wells have been drilled to delineate thecharacteristics of the reservoir. The limits of a field located on a structural trap canbe determined more easily than a stratigraphic field based on the informationobtained from drilled wells and geophysical data.The subsurface information includes:1. Expected depths of gas-oil and oil-water contact zones.2. The anticipated pressures in the formations to be drilled.3. Structure configuration of reservoir and its extension.Production is a combination of operations that includes:1. Bringing the fluids (oil, gas, and water) to the surface2. Maintaining and/or enhancing the productive capacity of the wells3. Treating and separating the fluids4. Purifying, testing, measuring, and preparing the fluids for marketing5. Disposing of produced water6. Transporting oil and gas to market.


(PHASE 5) GEOCHEMICAL EXPLORATION:

1- Before Drilling:

Surface geochemical exploration of soil sediments for hydrocarboninvestigation. Geochemical analysis of oil and gas seeps.

2- After Drilling:

Geochemical analysis of the extracted rock samples either ditch or core forsource rock evaluation and biological marker distributions. Geochemical analysis of crude oils for biomarker characterization. Infer the correlation between crude oils and source rock attributes.


STOCK RESERVE CALCULATIONS

Reserve are the amount of oil and gas that can be produced from a well or field in thefuture under current economic conditions using the current technology.Reserves are always reported in stock tank barrels of oil and standard cubic feet ofgases.

1 Barrel of Oil = 158.99 Liters

Stock Oil Reserves (bbls)

Oil reserve can be computed volumetrically for a single well or an entire oil field asfollow:


Stock Gas Reserves (Cubic Feet)


OIL PROVINCES OF EGYPT


Crude Oil Production and Consumption: In 2007, Egypt produced 664000 barrels of oil per day (bbl/d) continuing itsfall from a high of 950000 bbl/d in 1995. Yet having consumed 653000 b/d in2007. Production was sufficient to prevent Egypt from becoming a net importer of oil(Oil and Gas Journal August, 2008)

Natural Gas Production and Consumption: Egypt's natural gas sector is expanding rapidly with production havingincreased over 30% between 1999 and 2007. In 2007, Egypt produced 1.7

trillion cubic feet (TCF) and consumed 1.1 TCF of natural gas. Egypt’s estimated proven gas reserves stand at 58.5 TCF, or roughly 1% of theworld reserves. Egypt is on its way will become a leading supplier of naturalgas throughout the Mediterranean region.

لة االستھالك اكبر من االنتاج, وایضا بسبب قیعياالنتاج نتیجة التوجة واالھتمام بالغاز الطب


Egypt is considered among the pioneer countries in which oil was discoveredas (surface seepage in 1886 in Gebel El-Zeit area along the west coast ofthe Gulf of Suez.)

Egypt produced an average of about 594,000 barrels per day (bbl/d) of crudeoil in 2004, down sharply from its peak of 922,000 (bbl/d) in 1996, but onlymodestly below the 618,000 (bbl/d) produced in 2003.Egypt is subdivided into four main petroliferous provinces:

GULF OF SUEZ.

WESTERN DESERT.

NILE DELTA & OFFSHORE MEDITERRANEAN SEA.

NORTHERN SINAI.


GULF OF SUEZ

The Gulf of Suez contributes by 50% of the overall production of oil in Egypt. It isconsidered as NW-SE intracratonic rift basin formed during Pre-Cambrian andrejuvenated during Oligocene and classified into THREE provinces according tothe INCLINATION OF STRATA AND FAULT TRENDS:

1. Northern Province

2. Central Province

3. Southern Province

كامبریان خلیج السویس ناتج عن عملیة الریفتنج في البریة حدث وحدثت اعاده للحركھ في اولیجوسین , اما خلیج العقبن سنة, نتیجھ االستریك سلیب فولت في اواخر خمسة ملیو

ن اتجاه في خلیج السویس متفقیوالجزء الشمالي والجنوبيالفولتات ومیل الطبقات , عكس الجزء االوسط


LITHOSTRATIGRAPIC SUCCESSION OF THE GULF OF SUEZ


SOURCE ROCKSMany workers have dealt with the problem of oil generation in the Gulf of SuezProvince.They concluded that the sedimentary section of the Gulf of Suez contain multipleintervals which exhibit source rock characteristics.These intervals consist of fine clastics and carbonates and represented by thefollowing formations: Nubia-B (Lower Carboniferous) Brown Limestone of Sudr Formation (Upper Cretaceous) Esna Shale (Paleocene) Lower Miocene shale (Rudeis Formation)Their content in total organic carbon contents ranges between 1% to more than

6.5%, which classified the source rock to be good to excellent potential source rocks.OIL BEARING ROCKS & FORMATIONSMost of the Gulf of Suez oil occurs in porous sandstone and fractured limestoneconstituting the following formations:

(Nubia A and C) consists of porous and permeable sandstone (Thebes’s formation) of Middle Eocene age, it is presented by cherty and

flinty limestones. (Nukhul Formation) of the basal Miocene age, represented by reefal

limestone in some areas and clastic sequence in another area from theGulf of Suez.

(Rudeis Formation) of sandstone interbeds with the shale intervalsforming lenses of stratigraphic traps in many of the oilfields.


CAP ROCKS & SEALING MECHANISM

The vertical sealing and cap rocks in the Gulf of Suez province occurs within theevaporite succession constituting the Upper Miocene of Ras Malaab Group in thefollowing formations:

(Belayim Formation) consists mainly from gypsum and anhydrite withshale interbeds.

(South Gharib Formation) consists mainly from rock salts, anhydrite withshale interbeds.

(Zeit Formation) consists mainly from rock salts.


WESTERN DESERT

The Western Desert of Egypt covers two thirds of the whole area of Egypt. The oilexploration activity revealed the discovery of more than 50 oil/or gas fields.Abu Gharadig Basin is an E-W oriented graben separates the coastal basins (Matruh,Shushan, Dahab Mireir and Natrun basins) which formed as a result of single riftduring the Permo-Triassic age than the southern and western basins (Gindi, Diyroutand Assiut and Faghur-Siwa Basin).

The FirstExploredArea


LITHOSTRATIGRAPHY OF THE WESTERN DESERT


POTENTIAL SOURCE ROCK

Potential source rocks for oil and gas generation have been identified in thefollowing stratigraphic intervals:1. Jurassic (Khatatba Formation)

2. Lower Cretaceous (Alam El-Bueib Formation)

3. Upper Cretaceous (Abu Roash E,F &G formations)These formations contain fair to excellent quality oil-gas prone source rock of mixedkerogen types (II-III)

OIL–BEARING ROCKS AND FORMATIONS

Alam El-Bueib Formation contains fine grained sandstone which acts as goodreservoir rocks. These sandstones show porosity values ranging from 10-20%. Thisformation produces oil and gas in Umbarka Field (44oAPI), Hayat Field (41o-50oAPI),Safir Field (45oAPI), and Tut Field (44oAPI).Aptian Alamein Dolomite reservoir of hard, dense vuggy dolomite of porosityvalues from 3-12%. The dolomite is an oil bearing in the following fields; Alamein(22-38oAPI), Yidma (44oAPI) and Razzak (38oAPI).


Kharita Formation reservoir of good potential reservoir rocks (porosity: 12-25%).This formation is oil bearing in the following fields; Salam Field and Abu GharadigField (36o-46oAPI).Bahariya Formation (Cenomanian) contains good sandstone reservoirs withporosity ranging from 18-25%. About 90% from oil and gas fields are produced fromthe Bahariya sandstone such as: Razzak, Khalda, Meleiha, Salam, Amar, Yasser, Zahra,Tut, Horus and Lotus. These fields produce oil of 34o to 50 o API.Abu Roash “G”, “F”, “D”, “C”, “B” members (Late Cenomanian) is considered thesecond main reservoir rocks in the Western Desert. It contains dolomite andlimestone beds “G” with porosity 10-35% and the oil (45o API), while “F” producesheavy crude oils (15 o API). “D” produce oil (36o API). Abu Roash “C” containssandstone and produce oil (32 o API) in Abu Sanan and Abu Gharadig fields.


THE NILE DELTA

The Nile delta area is an emerging major gas province and considered oneof the most promising areas for future exploration in northeastern Africa.In the last decade, exploration in the offshore Mediterranean Sea hasresulted in the discovery of significant proven reserves reached to morethan 68.2 (TCF).The natural gases are frequently accompanied by condensates (41-56°API), such conditions. Are present in the Nile delta and consequentlyrepresent favorable sedimentary environments for microbial gasgeneration.Due to the large thickness of the Neogene overburden, sediments of pre-Miocene age are seldom penetrated in the Nile delta and little is knownabout their source rock potential and qualities.

Messinian Crisis (Upper Miocene), make a large amount of evaporate exist in Nile delta and Gulfof Suez

principles of petroleum geology m.m.badawy

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