Maturity and Source‐rock Potential of Mesozoic and Palaeozoic Sediments, Jifarah Basin, Nw Libya

Abstract

The Jifarah Basin, NW Libya, has a sedimentary fill which includes marine shales of Triassic, Permian, Silurian and Ordovician ages together with Jurassic evaporites and Cambro‐Ordovician aeolian sandstones. Major risk in exploration of the basin is associated with the presence of source rocks. The present study investigates potential source rocks in the basin and assesses their thermal maturity, petroleum generation potential, organic richness and distribution. Cuttings and core samples from nine wells were analyzed using a Rock‐Eval 6 instrument and by standard petrographic microscopy. Kerogen type and amount were recorded. Triassic and Ordovician formations were only drilled in parts of the basin and have minor petroleum generation potential. Permian and Devonian samples also had low generation potential, as did samples from the upper part of the Silurian. The Devonian succession is of limited extent as a result of Hercynian uplift and erosion. Major petroleum generation potential is associated with the lower part of the Silurian Tanezzuft Formation in which high TOC values and moderate to high HI values were recorded. The formation is characterized by abundant fluorescing alginite. Most samples studied were early mature to mid‐mature but there was some regional variability.

Biomarker Characteristics of Potential Source Rocks in the Jabal Nafusah Area, Nw Libya: Petroleum Systems Significance

“…The results of Rock-Eval pyrolysis are presented in Fig. 12 and Table 2 (see also data in Abohajar et al, 2009). The source rock potential of the samples investigated is described in the following paragraphs.…”

“…The samples include potential source rocks of Triassic, Silurian and Ordovician ages. Permian and Devonian sedimentary rocks were not included in this study due to unfavourable organic facies (Abohajar et al, 2009). Most samples were ditch cuttings as only a few cores were available (Table 2).…”

“…For the present study, 27 samples from eight of the nine wells studied by Abohajar et al (2009) were selected for detailed organic geochemical analysis. The samples include potential source rocks of Triassic, Silurian and Ordovician ages.…”

“…A previous study (Abohajar et al, 2009) investigated the hydrocarbon generation potential of the Palaeozoic-Mesozoic succession preserved on the Arch. This study ultilized standard analytic techniques, identifying two organicrich intervals: in the Al-Azizyah Formation of Triassic age (up to 3.77 wt% TOC), and the Lower Silurian Tanezzuft "hot" shale (up to 8.7 wt% TOC).…”

“…Some 27 new samples (Table 1) from eight of the nine wells studied by Abohajar et al (2009) were selected from the Ordovician (Memouniyat Formation), Silurian (Tanezzuft Formation), and Triassic (Al-Aziziyah and Ouled Chebbi Formations) and were assessed using gas chromatography (GC), gas chromatographymass spectrometry (GC-MS) and Rock-Eval pyrolysis techniques.…”