HYDROCARBON GENERATION POTENTIAL OF JURASSIC, CRETACEOUS AND EOCENE ORGANIC-MATTER RICH SEDIMENTS FROM MOROCCO

Organic geochemical and petrological analysis has been carried out for sediments of the Tarfaya Basin, southern Morocco and for a Pliensbachian source rock from the Middle Atlas, due to missing Jurassic outcrops in the Tarfaya Basin. In order to obtain more information about hydrocarbon generation potential, cores from wells and outcrop samples covering a large area were collected. Organic and inorganic carbon as well as sulphur measurements, Rock-Eval pyrolysis, vitrinite reflectance measurements and organic-geochemical analyses (GC/GC-MS) were carried out to obtain information on depositional environment, thermal maturity and hydrocarbon generation potential.

High C_org contents were measured for Eocene sediments in the southern part of the Tarfaya Basin (up to 7 %). C_org values of Santonian, Coniacian and Campanian range between 1 and 6 %, with increasing values towards the recent coast. Similar C_org values were also measured for the Pliensbachian sample set (5 %). Highest values were measured for Cenomanian/Turonian black shales (up to 16 %). Most of the samples are representing a type-II kerogen, whereas some of the Late Turonian, Santonian and Eocene samples contain type-I kerogen. Kerogen type I/II was also assigned for the Pliensbachian samples. All of these sediments were deposited under marine, oxygen-depleted bottom waters, with favourable conditions for preservations of the organic matter (algae/phytoplankton). Eocene sediments revealed a higher influence of terrestrial organic matter mixed to the plankton-derived material. Maturity of the samples of the Tarfaya Basin is low, i.e. they are immature or at an early mature range, as reflected by vitrinite reflectance data, Rock-Eval pyrolysis T_max and specific biomarker ratios. Despite their immature range, especially the Late Cretaceous can be regarded as unconventional petroleum source rocks due to their thickness, quality and quantity of organic matter. In contrast to the immature sediments of Tarfaya Basin, the Pliensbachian sediments act as effective petroleum source, and oil seeps were observed. This is supported by thermal maturity data and bulk kinetic parameters, which were included in a numerical 1D petroleum system model. Burial-, thermal-, and maturation histories were calculated, as well as timing and petroleum generation potential within this source rock.