In this study, the secondary well data for Cretaceous to Miocene cutting samples in four deep offshore exploration wells, i.e., Pomboo-1 in the north, Kubwa-1 in the central, Simba-1 and Kiboko-1 in the south of the d...In this study, the secondary well data for Cretaceous to Miocene cutting samples in four deep offshore exploration wells, i.e., Pomboo-1 in the north, Kubwa-1 in the central, Simba-1 and Kiboko-1 in the south of the deep offshore Lamu Basin were assessed for identifying source rock presence and examining thermal maturity of the source rocks. The 2D basin modelling was used to analyse the bulk gas transformation in the basin. Total organic carbon (TOC) content values for the wells range from 0.09 wt % to 2.23 wt % with an average of 0.78 wt %. The average organic richness is higher in the Upper Cretaceous (0.83 wt %) than in the Palaeogene (0.65 wt %), Lower Cretaceous (0.28 wt %) and Upper Jurassic (0.30 wt %). The S_(1) averages for the Upper Cretaceous are 3.76 mg HC/g rock in Pomboo-1 and 0.31mg HC/g rock in Kubwa-1. The S_(2) averages for the Upper Cretaceous are 5.00 mg HC/g rock in Pomboo-1 and 0.72 mg HC/g rock in Kubwa-1. Hydrogen index (HI) values vary between 4 and 512 mg HC/g TOC with an average of 157.09 mg HC/g TOC. Organic matters were identified as mixed types of Ⅱ-Ⅲ (oil and gas prone) and Ⅲ-Ⅳ (gas prone) kerogen in the potential source rocks. The HI and S_(2) yield values are exceptionally high for the observed TOC values in Pomboo-1. The vitrinite reflectance and Tmax values of deep offshore Lamu Basin are in the ranges of 0.38%–0.72% and 360–441 ℃, respectively. It suggests the existence of both immature and mature source rocks. Vitrinite reflectance maturity favours near coastal region in the Upper Cretaceous. These results explain why Pomboo-1, Kubwa-1, Simba-1 and Kiboko-1 wells were dry. The temperatures are still cool for hydrocarbon generation in deep offshore. The critical risk for deep offshore Lamu Basin is charge, primarily source presence, and a lack of definitive evidence of a deep-water marine source rock being present. The four wells penetrate good quality reservoir and seal rocks, but source rock presence and maturity remain the critical play risk in the deep offshore Lamu Basin.展开更多
We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of near...We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of nearinfrared laser pulses at a central wavelength of 1036 nm from a commercial,high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad bandwidth of more than 9 THz without a significant power fall-off in the higher THz frequency components.The conversion efficiency is high(0.13%)in spite of the high excitation average power of 8 W.We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties ofχ(2)nonlinear crystals up to 8 THz.This new high-repetition-rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement time.展开更多
文摘In this study, the secondary well data for Cretaceous to Miocene cutting samples in four deep offshore exploration wells, i.e., Pomboo-1 in the north, Kubwa-1 in the central, Simba-1 and Kiboko-1 in the south of the deep offshore Lamu Basin were assessed for identifying source rock presence and examining thermal maturity of the source rocks. The 2D basin modelling was used to analyse the bulk gas transformation in the basin. Total organic carbon (TOC) content values for the wells range from 0.09 wt % to 2.23 wt % with an average of 0.78 wt %. The average organic richness is higher in the Upper Cretaceous (0.83 wt %) than in the Palaeogene (0.65 wt %), Lower Cretaceous (0.28 wt %) and Upper Jurassic (0.30 wt %). The S_(1) averages for the Upper Cretaceous are 3.76 mg HC/g rock in Pomboo-1 and 0.31mg HC/g rock in Kubwa-1. The S_(2) averages for the Upper Cretaceous are 5.00 mg HC/g rock in Pomboo-1 and 0.72 mg HC/g rock in Kubwa-1. Hydrogen index (HI) values vary between 4 and 512 mg HC/g TOC with an average of 157.09 mg HC/g TOC. Organic matters were identified as mixed types of Ⅱ-Ⅲ (oil and gas prone) and Ⅲ-Ⅳ (gas prone) kerogen in the potential source rocks. The HI and S_(2) yield values are exceptionally high for the observed TOC values in Pomboo-1. The vitrinite reflectance and Tmax values of deep offshore Lamu Basin are in the ranges of 0.38%–0.72% and 360–441 ℃, respectively. It suggests the existence of both immature and mature source rocks. Vitrinite reflectance maturity favours near coastal region in the Upper Cretaceous. These results explain why Pomboo-1, Kubwa-1, Simba-1 and Kiboko-1 wells were dry. The temperatures are still cool for hydrocarbon generation in deep offshore. The critical risk for deep offshore Lamu Basin is charge, primarily source presence, and a lack of definitive evidence of a deep-water marine source rock being present. The four wells penetrate good quality reservoir and seal rocks, but source rock presence and maturity remain the critical play risk in the deep offshore Lamu Basin.
基金Ministerium für Kultur und Wissenschaft des Landes Nordrhein-Westfalen(terahertz.NRW program Netzwerke 2021)Ruhr-Universit?t Bochum(DFG Open Access Publication Funds)Deutsche Forschungsgemeinschaft(SFB/TRR196 MARIE project M01 and C07,PR1413/3-2,EXC-2033-Projektnummer390677874-RESOLV)。
文摘We present a high-power and broadband terahertz(THz)time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector.The THz source is based on optical rectification of nearinfrared laser pulses at a central wavelength of 1036 nm from a commercial,high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad bandwidth of more than 9 THz without a significant power fall-off in the higher THz frequency components.The conversion efficiency is high(0.13%)in spite of the high excitation average power of 8 W.We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties ofχ(2)nonlinear crystals up to 8 THz.This new high-repetition-rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement time.
