The potential of CBM (Coalbed Methane) generation in the South Santa Catarina reserve: 1. petrographic and chemical characteristics of the coal seams in Rio Bonito Formation, Paraná Basin

Currently, CBM is an important source of alternative energy in Brazil. The most important coal bearing sedimentary succession occurs in the Paraná Basin, and the largest reserves are located in RS and SC. This work aims to analyze the chemical and petrological characteristics of coal seams from three boreholes, being recently conducted in the South Santa Catarina coalfield, in the areas of Treviso and Ararangua (SC), in order to assess the capacity to generate associated methane gas. Samples of seven coal seams were collected (Barro Branco, Irapuá, seam A, Bonito Superior, Bonito Inferior, Pré-Bonito Superior and Pré-Bonito Inferior) from the Rio Bonito Formation, and were prepared and submitted for petrographic and chemical analysis. The lithotype banded dull (BD) was prevalent in hole CBM-SC-2012, and dull (D) in hole CBM-SC-2013. Petrographic results indicated average vitrinite reflectance values ​​​​​​​​​​​​​​​​from 0.60 to 1.26 % Rrandom, classifying the seams according to rank from high volatile bituminous C to medium volatile bituminous. Maceral analysis showed significant variation in maceral composition, with predominance of vitrinite and inertinite. Results from the proximate analysis showed ash variation from 34.93 to 65.70 wt%, whereas the gross calorific value varied from 1858.0 to 5074.8 cal/g. The carbon content ranged from 4.15 to 65.81 wt%, and sulfur ranged from 0.22 to 12.43%. According to the analyzed parameters, the Barro Branco and Irapuá seams present characteristics suitable for the generation of natural gas, whereas the Bonito seam has a lower gas generation potential because of its high ash content.

Coal; natural gas; Rio Bonito Formation