Source Rock BY: ABDELRAHMAN AHMED ALI ABDELRAHMAN UNDER SUPERVISOR OF: PROF.DR: ALIAA ZALAT

INTRODUCTION Source rock is the most important part in the petroleum system as it refers to rocks from which hydrocarbons have been generated. Source rock examples as shale,clay and fine limestone while shale is one of the dominant source rocks for hydrocarbon.

Types of source rocks: Source rocks are classified according to the types of kerogen that they contain, which control the type of hydrocarbons that will be generated.

Type 1 Source rocks are formed from algal remains deposited under anoxic conditions in deep lakes, they tend to generate waxy crude oil when exposed to thermal stress during deep burial.

Type 2 Source rocks are formed from marine planktonic remains preserved under anoxic conditions in marine environments, they produce both oil and gas when thermally cracked during deep burial.

Type 3 Source rocks are formed from terrestrial plant material that has been decomposed by bacteria and fungi under oxic or sub-oxic conditions, they tend to generate mostly gas with light oils when thermally cracked during deep burial, most coals and coaly shales are generally type 3 source rocks.

Evaluation of the source rock: Evaluation of source rock uses the methods of geochemical exploration 1-organic matter richness 2-type of organic matter 3-degree of H.C maturation

1-Organic matter richness Shale contains 99% rock + 1% organic matter (90% kerogen + 1% bitumen)

2-Types of organic matter Kerogen Insoluble-high M.Wt Bitumen Soluble-low M.Wt Kerogen is usually classified according to type based mainly on its H/C ratio and O/C ratio.

Diagenetic track

Kerogen can be classified by source material: Type Name Source I algal kerogen mainly algae II liptinitic kerogen mainly marine plankton III woody kerogen mainly terrestrial plants

3-Degree of H.C maturation 3.1-Color change during maturation 3.2-Vitrinite reflectance 3.3-Factors controlling H.C maturation

3.1-Color change during maturation Yellow (low mature) Yellowish browen Brown Black (high mature)

3.2-Vitrinite reflectance -Determine degree of H.C maturation -high reflected light = high maturation

3.3-Factors controlling H.C maturation 1-temperature 2-pressure 3-time 4-radioactive content 5-catalysts(bacteria)

Source rocks in Egypt Based on the results of intensive studies and analyses carried out on numerous well samples only four levels were considered to have the prerequisites to yield oil. These are the Kareem and Rudies shale of the Gharandal group, the Balayiem shales of the Ras Malaab evaporites and the Esna shale of the Paleocene-Eocene sequence.

Other potential source rocks appear to be either immature (Balayiem shales) or over mature (Brown limestone of the Sudr formation, and the Black shales of Nubia B). These formations may have yielded oil prior to the Pre-Miocene erosional period and the accumulations of these oils may have been dispersed during taphrogenic phase .

Test Yourself A- True or False 1-source rock are classified according to type of bitumen they cotain. ( ) 2- Type 1 Source rocks are formed from algal remains and tend to generate waxy crude oil. ( ) 3-most coals and coaly shales are type 2 source rocks. ( ) 4-black kerogen color is related to low degree of maturation. ( )

B-Complete 1-kerogen change to graphite by .….hydrogen. 2-source rock can be classified acco. To type of kerogen into …….,………and…….. 3-diagenetic track used to know……………. 4-kerogen change to methane by .….hydrogen. 5-Factors controlling H.C maturation.................

C-Choose 1-degree of maturation can be determined by (vitrinite reflectance-diagenetic track-carbon isotopes). 2-geochemical exploration is used to evaluate (cap-resevoir-source) rock.

Answers A 1-false 2-true 3-false 4-false B 1-losing 2-type1,type2 and type3 3-type of organic matter 4-gainning 5-temp,pressure,time,radioactive content and catalyst C 1-vitrinide reflectance 2-source rock

References Urov, K.; Sumberg, A. (1999). "Characteristics of oil shales and shale-like rocks of known deposits and outcrops" . Oil Shale. A Scientific-Technical Journal (Estonian Academy Publishers) 16 (3 Special): 1–64.ISBN 9985-50-274-4. Hutton, A.C. (1987). "Petrographic classification of oil shales". International Journal of Coal Geology (Elsevier Science) Lee, Sunggyu (1991). Oil Shale Technology. CRC Press. pp. 6, 10. Moody, Richard (2007). "UK Oil and Gas Shales—Definitions and Distribution in Time and Space". History of On-Shore Hydrocarbon Use in the UK. Weymouth: Geological Society of London.