Palynofacies and Source Rock Potential of the ST-7H Well, Offshore Tano Basin, Western Region, Ghana

Abstract

Abstract:Samples from ST-7H well offshore Tano basin in western region of Ghana have been subjected to palynofacies, palynological and geochemical analysis. Five palynofacies associations (I -V) have been identified based on the percentage relative abundances of the sedimentary organic matter (SOM). Palynofacies type I and type IV reflects deposition in a distal dysoxic-anoxic shelf (nearshore) environment, palynofacies type II suggest distal dysoxic to anoxic shelf to deep basin environment with abundant AOM, palynofacies type III is indicative of distal dysoxic to oxic shelf (fluvio-deltaic) environment of deposition and palynofacies type V, a mud -dominated oxic distal shelf (open marine) environment. Based on marker palynomorphs, an Aptian to Maastrichtian age, have been assigned to the sediments in the ST 7H well, with an unconformity between the Cenomanian and Campanian sediments. Geochemical data indicate that the samples from ST 7H well have fair to very good petroleum potential. Most of the samples, however, fall out of the hydrocarbon generating zone because of the low (< 0.10) Production Index (PI). Kerogen types show type II, II/III and III which are oil prone, oil-gas prone and gas prone respectively. Thermal maturity from within the well indicates immature to early mature hydrocarbons.

Sedimentary organic matter as a proficient tool for the palaeoenvironmental and palaeodepositional settings on Gondwana coal deposits

“…Resultantly, the dominance and the sub-dominance of the various forms of the organic matter types also indicate the source rock potential of any rock. Concurrence of TAI (Thermal Alteration Index) with palynofacies is an excellent parameter for the source rock evaluation and has been used widely by different researchers (Misra and Pundeer 1994;Thakur and Dogra 2011;El Atfy et al 2014;Peters et al 2015;Christoph et al 2019). Hacquebard and Donaldson (1969) and modified by Marchionni 1980;Singh and Singh 1996;Aggarwal et al 2019a, b, c The implication of palynofacies in high-resolution sequence biostratigraphy:…”

Palynostratigraphy, Paleoenvironments and Kerogen Evaluation of the Campanian-Maastrichtian Enugu Shale, Anambra Basin, Nigeria

“…AOM includes all particulate organic components that appear structureless at the scale of light microscopy, including bacterially derived AOM, resinous and amorphous products of the diagenesis of macrophyte tissues (Atta-Peters et al, 2015). The relative abundance of the palynofacies element recovered from the samples are recorded (Table 2).…”

“…However, palynofacies type I (P-I) and type III (P-III) could be classified as type III kerogen (mainly gas prone, could be related to the high phytoclasts input) as deduced mainly from Tyson (1993) ternary plot (Jaeger, 2013;Tahoun et al, 2013;Makled & Baioumi 2013). The kerogen investigation indicates that particulate organic matter, spore coloration and thermal maturity results obtained from the Enugu outcrop samples is at an immature thermal oil maturity stage (Atta-Peters & Kyorku, 2013;Makled et al, 2013;Ribeiro et al, 2013;Chiaghanam et al, 2014;Atta-Peters et al, 2015).…”