Compaction and Porosity Based Pore Pressure Prediction in the “Cappe Field”, Coastal Swamp Depobelt, Niger Delta, Nigeria

Three wells of the “Cappe” Field in the offshore part of the Coastal Swamp depobelt I, Niger Delta, were evaluated primarily to determine the impact of compaction on reservoir quality and to determine possible over-pressured zones in the Benin and Agbada formations. Sandstone porosity-depth plots of the three wells show a linear trend of gradual porosity reduction with depth for the top of the wells 1, 2 and 3 (r2 = 0.26, 0.42 and 0.73 at 4500-5900ft, 3940-5000ft and 2500-5350ft respectively). Two variations from this simple trend were observed. 1: Intervals of insignificant porosity reduction (well 1; 6500-7950ft, r2 = 0.00003 and well 2; 5760-7911ft, r2 = 0.008), due to hydrocarbon entrapment. 2: A reversal in the trend (well 3; 5450-9658ft, r = -0.89) indicated by an increase in porosity as a result of overpressure. A number of factors such as compaction, fluid content and pore pressure affect the porosity-depth trends of the Agbada Formation. A decrease in porosity with depth generally holds true for shales (well 1: r2 = 0.74 and well 2: r2 = 0.81) except for an increase in porosity (r2 = -0.596) observed in well 3. Compaction factor is significant in sandstone porosity reduction in the Benin Formation (well 1: 58.3% and well 2: 68.9%) than in the Agbada Formation (well 1: 25.64% and well 2: 25.29%). Sandstone porosities predicted at the base of the wells are generally low (well 1: 5.86%, well 2: 7.52%), implying uneconomical reservoirs.KEY WORDS: Pore Pressure, Overpressure, Porosity, Compactio

Histopathologic effect of potassium bromate on the kidney of adult wistar rats.

Objective: We aimed to demonstrate the histopathologic effects of potassium bromate (KBrO ) on the kidney tissues of rats following 3short-term and long-term exposures.Method: Twenty young wistar rats of weights 180-250g were divided into three groups. The control group A was sub-divided into two groups of three rats each and orally administered with 1ml of distilled water daily for 7 days and 21 days respectively; the experimental groups B and C were administered with 75 mg/kg body weight/day dosage of KBrO orally for 1 week and 3 weeks 3 respectively.Results: Histopathological examination of the experimental groups showed haemorrhagic, necrotic and degenerative changes in the kidney tissues compared with the control group, which maintained normal kidney tissues. These histological changes were marked in group C animals exposed to KBrO for 3 weeks compared to those exposed for 1 week. 3             Conclusion: The present study indicated that both short-term and long-term exposures to sub-lethal dose of KBrO caused alterations 3in the histology of the kidney of wistar rats. These alterations may account for the various nephrotoxic effects associated with exposure to KBrO In addition, some of the histopathologic effects were marked in long-term compared to short-term exposure to 3. KBrO , thus indicating duration-dependent effect of KBrO consumption.Key Words: Potassium bromate, Wistar rats, Histopathology, Kidneys, Nephrotoxi

Clay mineral formation and transformation in non-marine environments and implications for Early Cretaceous palaeoclimatic evolution: The Weald Basin, Southeast England

Availability of data and materials: Supplementary data are available as Appendix 1. The corresponding author can be contacted for queries or clarifications.Analyses of clay minerals within the Early Cretaceous Weald Basin, Southeast England reveal kaolinite, illite and chlorite as the main detrital clay minerals while glauconite and smectite are subordinates. A kaolinite-rich assemblage which characterized the sand-dominated Ashdown and Tunbridge Wells Sand formations and an illite-dominated assemblage associated mostly with the Wadhurst Clay and Weald Clay formations are recognized. Kaolinite was enriched in the Ashdown and Tunbridge Wells Sand formations during warm and humid climate with high precipitation that encouraged chemical weathering and leaching, while cold and dry conditions favoured the concentration of illite in the Wadhurst Clay and Weald Clay formations. Rainfall patterns associated with warm climate were drastically reduced during the drier climatic conditions. Most clay minerals are detrital in origin, with chlorite being more prominent than previously recognized. Contrary to previous studies and assumptions, this study revealed that authigenic clay minerals are present in the Hastings Beds, with vermiform and mica-replacive kaolinite being the most common, consistent with humid depositional environments. Isolated authigenic illite is also present, along with a chloritized grain, providing evidence for mesodiagenesis. The absence of dickite and occurrence of kaolinite, suggest that authigenic illite formed in relatively shallow burial conditions, indicating a maximum burial depth of 2500 m–3000 m, about 1000 m deeper than previous estimates of 1500 m–2000 m. Authigenic clay minerals are absent in the Weald Clay Formation possibly because of hindered flow of meteoric water and limited growth space for authigenic minerals. This study is significant in: 1) reinforcing multiple methods to facilitate a robust and balanced knowledge of formation and transformation of clay minerals; 2) investigating detrital and authigenic clay mineral assemblages when assessing the palaeoenvironments of sedimentary basins.CGG Robertson provided collaborative funding by conducting QEMSCAN®, SEM and thin section analyses for the project