Petroleum System P1

24/10/2018

Petroleum Geology / 3

Oil & Gas Engineering Dept.

MSc. Hussein A.

Petroleum System ( Part One )

The Source Rocks

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Petroleum System Processes 

Generation - Burial of source rock to temperature and pressure regime sufficient to convert organic matter into hydrocarbon. n.

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Migration - Movement of hydrocarbon out of the source rock toward and into a trap.

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Accumulation - A volume of hydrocarbon migrating into a trap faster than the trap leaks resulting in an accumulation. n.

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Preservation - Hydrocarbon remains in reservoir and is not altered by biodegradation or “water-washing”. ”.

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migrating. g. Timing -Trap forms before and during hydrocarbon  m 2

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Petroleum source beds are fine grained, clay-rich siliclastic rocks (mudstones, shales) or dark coloured carbonate rocks (limestones, marlstones), which have generated and effectively expelled hydrocarbons. Most of the petroleum is sourced from cyclically bedded Jurassic shales and carbonates (Callovian-Oxfordian- Kimmeridgian ages). (n ( n ra!). ra!). Good uality petroleum source rocks can be deposited in marine or lakes environments as organic-matter-rich muds providing that bottom waters are oxygendeficient, i.e. that reducing conditions prevail. 6

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"or the source roc# to be prolific potential ($issot and %elte& '*+ ,unt& '+ and Johnson et al.& //0) they should have the follo1ing peculiars available2 '- Good '- Good uantity of total organic carbon (!"#) more than $.%&. - 'erogen - 'erogen should be mostly from types () and () in chemical analysis and the type of organic matter is amorphous organic matter ("*), and from type () and (+) in microscopic test. 0- !hermal 0- !hermal maturity should be mature enough for oil generation.

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t the beginning of this lesson it is necessary to give the definitions of some terms and basic indications for assessment of source rocks to be the base in explaining the seuence of works in this lesson, 1-

!otal organic carbon ($OC), t represents the total organic carbon measured in

percentage from the total weight of the rock. 2- 3',

ydrocarbons present in the rock in free form and which are librated at

temperatures less than $$#º and measured in milligram hydrocarbon/gram from the rock. 3- 3.,

ydrocarbons which resulted from the crack of kerogen in high temperatures

($$#º-%$$#º) and measured in milligram hydrocarbon/gram from the rock. 4- S3: 5-

Organic carbon dioxide released between 300 º and 390Cº.

*aximum temperature ($max.), t represents the temperature of higher oil

production at (01) and it is measured in degree centigrade. t is used in measurements of the organic matter and its maturation.

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ydrogen index ( ,) t represents the ratio range and hydrogen activity

in organic matter to produce hydrocarbons, it can be gotten mathematically by the euality of 0 1 on the total organic matter measured in (mg #/g !"#). 7-

"xygen index ( O) t represents the ratio range and oxygen activity in

organic matter to produce hydrocarbons, it can be gotten mathematically by the euality of 0  on the total organic matter measured in (mg #" 1/g !"#). 8-

Petroleum potential ( 44) t represents production potential for

hydrocarbon group form the source rocks included in maturity and it is measured from the sum of 0 2 and 01 pours from pyrolysis device through the rock. 9-

Production index ( 4)

=

02/ (0 2301) "il window

=

$.$4 - $.5. igher igher values values

are often due to migrating hydrocarbons hydrocarbons or contaminants.

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!he origin of hydrocarbons belongs to the sedimentary organic matters derived from living organic matter, which is called kerogen in petroleum geology (0taplin, 26768 and orsfield, 2669).

Kerogen   is defined as organic material with a high molecular weight is not soluble in organic solvents and acids (#:, ;) and consists of the remains of microorganisms with plants and plankton. 'erogen in rocks has four principle sources marine, lacustrine, terrestrial, and recycled. !he relative ability of source rock to generate petroleum defined by its kerogen uantity (!"#) and uality (high or low in hydrogen). 2.0

>2.0

10.0-20.0

12.0-24.0

Quantity

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Table 2: 2: ock!/val yrolysis data of the studied samples (GeoMark Laboratories)

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8xamples of the source roc#s in ra! '. 'a(mah )imestone *ormation .  +amama *ormation 0. ,ulaiy *ormation *. Ratawi *ormation 9. -ubair *ormation . 'ahr .mr *ormation 7. ,argelu *ormation . /hia -airi *ormation 30

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