GEOCHEMICAL ASSESSMENT OF CRETACEOUS SEDIMENT IN THE NIGERIAN SECTOR OF THE CHAD BASIN FROM KADARU-1 AND HERWA-1

EXPLORATORY WELLS FOR POSSIBLE PETROLEUM GENERATION

Y. B. Mohammed

Department of Geology

University of Maiduguri, Maiduguri, Nigeria

Email: bzakirai@yahoo.com

 ABSTRACT

Two of the exploratory wells, Kadaru-1 and Herwa-1 drilled in the Nigerian sector of the Chad basin were used for the research. The geochemical assessment was carried out using twenty (20) selected shale samples for the analytical work. The samples were raw shale from some Cretaceous sediment. The overall average SOM, SHC, AHC, and NSO values are 130ppm, 22.8ppm, 38.3ppm, and 67.8ppm in Kadaru-1 well and 280ppm, 33.5ppm, 65.3ppm, and 156ppm in Herwa-1 well. The concentrations of SOM, SHC, AHC, and NSO as a function of burial depth in both wells are generally inconsistent, but there is a progressive increase of these parameters with burial depth in Herwa-1 well between (1745- 2455) m, which is characterized as the source bed and reveals “oil shows”. The general interpretation signifies that the samples are relatively of low quality and the nonhydrocarbon heteroatomic compounds (NSO) have higher concentration values than the hydrocarbon compounds (SHC&AHC) in the two studied wells and the anaerobes utilized sulfate and nitrate ions instead of molecular oxygen as electron acceptors for their metabolic processes and survived under anoxic-suboxic condition.