Earth, Energy & Environment
Received: 28 Apr 2018 , Published: 06 May 2018
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|1||Uzoegbu, M. U|
The thermal maturity parameter used in the evaluation of the hydrocarbon generative potential of the sedimentary organic matter is based largely on the extent of molecular transformation of the biological markers due to geothermal stress which is a function of depth or burial history. The shale samples were collected at Gbekebo ditch cutting locality. The samples were examined and analyzed to determine their oil and gas potential. The HI values range from 2.00 to 327.07 mgHC/gTOC with a mean value of 103.46 mgHC/gTOC indicates a Type III and mixed Type II/III kerogen. Tmax values ranging from 415 to 437 oC with an average of 429.50 oC shows that the shale samples are immature to marginally mature. The total organic carbon (TOC) (1.61 wt%) and S1 + S2 (2.81) of the shale constitutes that of a excellent source rock with gas-prone kerogen indicated by Rock-Eval S2/S3 (5.59). The high oxygen index (OI) (40.85 mgCO2g-1TOC) suggest deposition in a shallow marine environment. Biomarker analysis of the shale samples generally reveal a bimodal nalkane envelope with maxima between (nC16 and nC18) and (nC27 and nC29) suggesting that the source organic matter were derived from a variable mixture of algae and higher plant materials with q relative higher input from marine algae as reveal by the presence of the C30 24-n-propyl cholestane (%C30 sterane range from 0.45 to as high as 5.23%). The presence of organic matter of marine algae (%C27 sterane av. 52% and positive detection of C30 sedimentary n-propyl cholestane av. 3.7%) suggest that the control on the HI as an indication of source rock quality in varying level of organic matter preservation. The source rocks have predominantly gas prone with lesser oil prone organic matter ranging from immature to marginally mature at shallow levels but may reaching proven mature levels in the subsurface.
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