Organic Geochemical Characterization of Some Carboniferous Coal Seams of the Zonguldak Basin (NW Turkey)

Abstract

The Carboniferous clastic sequence of the Zonguldak Basin contains several coal seams that have been mined since 1848 as the only major bituminous coal deposit of Turkey. Recently, a study was initiated aimed at determining the coalbed methane potential of the basin. Within the framework of this study, in addition to coal geology and numerical basin modelling, organic geochemical methods have been used to define the relevant properties of the coals. The coal seams are located in a Namurian to Westphalian D progradational delta and fluid plane sequence. This sequence was originally up to 3500 m thick prior to being eroded during two major uplift periods caused by the Hercynian and Alpine orogenic movements. There exists up to 8 coal seams in Namurian, 20 to 26 in Westphalian A and up to 8 coal seams in Westphalian B,C and D.

Geochemical analysis were carried out on 42 coal samples from wells and mines. The procedures applied includes total organic carbon (TOC) determination, Rock-sEval pyrolysis, proximate and elemental analysis and organic petrography. Additionally, kinetic parameters of bulk hydrocarbon generation from coal were determined by open-system non-isothermal pyrolysis. The majority of the coals in the Zonguldak basin are typical humic coals of high volatile C to A bituminous rank. Vitrinite reflectance values in general vary between 0.55 and 1.20 % (Ro mean). However, data from a recent deep test well showed that the maturity of the coals at the base of the Westphalian A can increase up to 1.45 % (Ro mean). Further details of the type, maturity, maceral composition, hydrocarbon generation potential of the coals and relations between various geochemical parameters are presented.