Irati Formation

PETROSIX Operations in Brazil. Petroleo Brasderio (Petrobras) has a dedicated facdity to produce cmde shale oil from the Irati formation in southern Bra2d. The facdity is called the Oil Shale Industriali2ation Superintendency (SIX) and uses the PETROSIX retorting technology (see Table 7 and Fig. 3). 

Paulo to up to 5-7% in Sao Gabriel (frontier with Uruguai). The inorganic phase is mainly carbonates in Sao Paulo while in the South it is mainly clays. Even the characteristic fossil of the Irati Formation changes from the Stereosternum tumidum in Sao Paulo, pro per to fresh, limpid water to the Mesosaurus braziliensis, in the South, more adapted to brackish water. What would then be the chemical composition of the Irati Formation if not a distribution func tion ... 

IRATI FORMATION, by far the largest, which extends from the state of Sao Paulo to the frontier with Uruguai. The very conservative numbers shown in Table II are meant to represent the measured reserves processable by the Petrosix process developed by Petrobras to retort oil shales. These restrictions are mainly related to min ing variables, carbon content, brittleness etc. Indeed, they repre sent only a small fraction (the border) of the Parana Basin. 

A very comprehensive analysis of hydrocarbons (linear, acyclic and cyclic - steranes, hopanes etc.- isoprenoids) carboxylic acids, aldehydes, ketones and amines of the Vale do Paraiba and Marau oil shales was made by Chicarelli (27). An extremely careful quantitative and qualitative analysis of hydrocarbons (n-, iso-and anteiso-paraffins, isoprenoids, steranes and triterpanes) and carboxylic acids of Irati oil shale was presented by Carvalhaes (28). Nooner Oro (29) also reported data on the hydrocarbons pres ent in the Irati Formation. Polycyclic aromatic hydrocarbons in I-rati were determined by Youngblood Blumer (40). 

The CPI determination as a stratigraphic function (33) in the Irati Formation led to the characterization of a most important ph nomenum that occurred in this region, a diabase intrusion with important implications to organic geochemistry. In this stratigraphic column, the CPI varied from 1.07 at the bottom of the first layer (8.8m depth) to 1.21 at the bottom of the lower layer (21.4m depth). The completely anomalous behaviour of the CPI as a stratigraphic function in this column led to the characterization of the above mentioned heat effect caused by the diabase intrusion. 

The diabase intrusion in the Irati Formation. A natural laboratory for the study of the influence of heat in geochemical reactions... 

In general, photolysis either leads to protonic acids or Lewis acids, which iratiate a cationic polymerization of oxies. However, the formation and initiation step of the active species of several initiators are not yet fully dari/ied. 

This method was used to determine the content of various organic functional groups (amines, alcohols, phenols, aldehydes, ketones, carboxyl, insaturation, allylic/benzylic sites) in kerogens of Brazilian oil shales. The results (26) indicate the Tremembe Formation as being the most functi.onatTzed while Irati is the least. This is in accordance with the accepted trend that functionalizations correlates with maturity. 

Carbon Preference Index (32). This index, devised by Bray and Evans to be used as a maturity index decreases as the sediment increases maturation to a limit of one. Carvalhaes C28) showed that an Irati sample submitted to a maximum of 509C in its thermal history, presented a CPI of 1.58 indicating it to be a reasonably mature sediment. Nooner Oro (29) gave the values of 1.05 for this Formation. 

Pristane/Phytane Index. The data obtained for the stratigra-phic column CERI-1 (33) say that the ratio pristane/phytane varies froml.l (at the topof thelst layer) to 2.0 (2m below the previous point). It keeps approximately constant at 1.5 for therest of the col umn. Carvalhaes (23) found the value 1.94 for a sample of the same formation. In all samples so far analysed from the Irati F. the ratio is greater than one. 

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