Biostratigraphy, Palynofacies and Organic Geochemical Characterization of Three Wells, Western Offshore Niger Delta Nigeria  

作　　者：Oluwafemi Gabriel Ogunsanya Joshua Babatunde Asere Olugbenga Ademola Boboye Kehinde Sunday Bosikun Grace Adewumi Adegboye Oluwafemi Gabriel Ogunsanya;Joshua Babatunde Asere;Olugbenga Ademola Boboye;Kehinde Sunday Bosikun;Grace Adewumi Adegboye(Department of Geology, University of Ibadan, Ibadan, Oyo, Nigeria)

机构地区：[1]Department of Geology, University of Ibadan, Ibadan, Oyo, Nigeria

出　　处：《Open Journal of Geology》2023年第5期504-535,共32页地质学期刊（英文）

摘　　要：Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T_max), and Vitrinite Reflectance (VR_o) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.Ditch samples from AP-4, ER-51 and UK-2 offshore Niger Delta were subjected to biostratigraphic and organic geochemical analyses which entail foraminiferal, palynological, Spore Colour Index (SCI), Rock-Eval Pyrolysis and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The results have established N19 and N17;N17, N16 and N15;and N9 and N8 biozones;and P600 and P700 palynological zones. The dominance of palynomaceral (PM) I and II suggests Type III kerogen. PM III and IV (Type II and IV) were recorded. SCI ranges from 3/4 to 5/6 suggesting an early to mature liquid hydrocarbon generation phase. Rock-Eval Pyrolysis shows that the Total Organic Carbon (TOC), Hydrogen Index (HI), Pyrolysis temperature (T_max), and Vitrinite Reflectance (VR_o) range from 2.48 wt% - 6.37 wt%, 78 - 258, 411°C - 431°C and 0.26% - 0.69% respectively suggesting high TOC of Type II/III kerogen. FTIR indices show Type I kerogen in all the wells. VRo results range from 0.4 - 0.5 indicating an immature source. High concentrations of aliphatic saturates in identified functional groups indicate a low biodegradation. The abundance and diversity of recovered assemblages and dominance of PM I and II suggest shallow depositional environments with an age range of late Miocene to early Pliocene. Palynomaceral, SCI, and Rock-Eval inference contradict FTIR kerogen type suggesting that IR spectroscopy might not be suitable for kerogen typing and origin. The geochemical and biostratigraphical inferences must be corroborated for a successful evaluation. However, the source rock in the study area has adequate organic matter with the prospect to generate both oil and gas at appropriate maturity.

关 键 词：BIOSTRATIGRAPHY ROCK-EVAL PALYNOFACIES Infrared Spectroscopy Palynomaceral 

分 类 号：P61[天文地球—矿床学]