The study of oil and gas potential of the upper layer of Aleksinac oil shale deposit

[G. Gajica]

185 listova

Hemija - Geohemija / Chemistry - Geochemistry

U okviru ove disertacije ispitivani su uzorci uljnih šejlova i bituminoznih laporaca koji potiču iz povlatnog sloja Aleksinačkog ležišta (blok „Dubrava”). Istraživanjima u okviru ove disertacije po prvi put detaljno je geohemijski okarakterisan povlatni sloj uljnih šejlova, koji je znatno deblji i pristupačniji te lakši za eksploataciju i preradu. Ispitivanja organske supstance (OS) pokazala su da je ona u značajnoj meri očuvana, formirana pretežno od algalnih prekursorskih organizama sa izvesnim primesama viših kopnenih biljaka, staložena u redukcionoj alkalnoj brakično-slatvododnoj jezerskoj sredini, i da je na niskom stepenu zrelosti. Organska supstanca većine analiziranih uzoraka pretežno je sačinjena od kerogena tipa I i/ili tipa II. Ovi tipovi kerogena imaju veliki sadržaj vodonika i stoga imaju visok potencijal za generisanje tečnih ugljovodonika. Na osnovu stepena obogaćenja (Ki) i faktora obogaćenja (EF) utvrđeno je da su uzorci samo obogaćeni sa Mo i Cs. Analizom najpotencijalnijih uzoraka utvrđeno je da se veći prinosi sintetičke nafte dobijaju u otvorenom sistemu pirolize u poređenju sa zatvorenim. Prinosi ugljovodonika u pirolizatima iz otvorenog sistema odgovaraju vrednostima za matične stene sa odličnim potencijalom, dok u zatvorenom ukazuju na vrlo dobar. Dobijeni rezultati pokazuju da u otvorenom sistemu pirolize količina OS ima veći uticaj na generisanje sintetičke nafte nego tip kerogena, dok je u zatvorenom sistemu u uslovima kojima se intenzivnije simuliraju maturacione promene OS situacija obrnuta. Sastav dobijene „sintetičke nafte” ima određene nepoželjne karakteristike, zbog relativno velikog sadržaja olefina (otvoren sistem) i polarnih jedinjenja (zatvoren sistem), što može zahtevati dodatni tretman pre upotrebe i poskupljuje proces dobijanja.

In this thesis oil shale and bitumious marlston samples from the Upper layer of Aleksinac deposite (block Dubrava) were investigated. Within the investigation done in this thesis the Upper layer of oil shale, which is considerably thicker and more accessible, thus easier for exploitation and processing, was for the first time geochemically characterized in more detail. The examinations of organic matter (OM) has shown that it is significantly preserved, formed mainly from algae precursor organisms with a certain input of higher terrestrial plants, deposited in reduced lacustrine alkaline brackish to freshwater environment, and it is in low degree of maturity. The OM of most analysed samples predominantly contains kerogen types I and/or II. These types of kerogen have high hydrogen content and therefore have a high potential for generation of liquid hydrocarbons. Based on the degree of enrichment (Ki) and enrichment factor (EF) it was found that the investigated samples are enriched only in Mo and Cs. Analysing the most potential samples it has been determined that a higher yield of shale oil is obtained in the open pyrolysis system in comparison to the closed one. The yields of hydrocarbons in pyrolysates from the open system correspond to the values for excellent source rock potential, while in the closed pyrolysis system indicate very good potential. The obtained results showed that the quantity of OM has a greater impact on the shale oil generation than the kerogen type in the open pyrolysis system, while in the closed system in conditions, which more intensively simulate maturity changes of OM, the situation is reversed. The composition of obtained shale oil has certain undesirable characteristics due to the relatively high content of olefins (open system) and polar compounds (closed system), which may require additional treatment prior to use and increases the price of the entire process of obtaining shale oil.

uljni šejlovi, Aleksinačko ležište, biomarkeri, Rock-Eval, termogravimetrijska analiza, otvoren i zatvoren sistem pirolize, „sintetička nafta”

oil shale, Aleksinac deposite, biomarkers, Rock-Eval, thermogravimetric analysis, pyrolysis in the open and the closed systems, shale oil

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