GEOCHEMISTRY AND ENVIRONMENTAL IMPLICATIONS OF PRODUCED WATER FROM NIGER DELTA PETROLEUM PROVINCE, NIGERIA

Oil- and gas- field produced water which constitute about 98% of hydrocarbon waste generated from petroleum industries normally contain hydrocarbon residues, metallic and non-metallic compounds capable of impacting the environment negatively. This study focuses on geochemical composition of produced water associated with crude oil production in area of Niger Delta, with emphasis on its physico-chemical properties. A total of twenty (20) samples of produced water from four (4) offshore oil wells in the Niger Delta were analyzed in this study. The parameters (pH, Conductivity, TDS, Salinity etc) were measured in situ using potable Hatch model 156 pH and EC meter. Similarly, other parameters (alkalinity, soluble salt etc.) were measured using standard methods while analysis of metals was achieved using ICP-OES. The data generated were subjected to appropriate statistical analysis. The results obtained indicate that mean pH values of the analyzed produced water are 7.71±0.46, 7.21 ±0.79, 7.97±0.4 and 7.7 ± 0.8; mean salinity values are 11.50±6.50,13.0±0.32, 9.97±0.34 and 11.60±2.2% and mean conductivity values of 18,746.0±103, 21,498.0±456, 16,702.0±563 and 19,028.4±289 for Delta, Okan, Meren and Parabe respectively. However, the mean ammonium and sulphide values are 24.18±11.76 and 1.21±1.02; 21.10±13.4 and 0.64±0.09; 20.29±17.6 and 0.31±0.04 and 21.15±10.5 and 1.71±0.89 for Delta, Okan, Meren and Parabe respectively. Besides, the range of mean concentration values of some of the analyzed metals are As (1.20±0.78-2.44±1.2); Cr (0.07±0.05-0.3±0.07); Ni (0.14±0.10-0.53±0.30); Pb (2.87±1.26-3.94±0.24) and V (0.03±0.01 -0.05±0.03) in all the produced water samples. The statistical evaluation of measured parameters showed significance ( P<0.05) for salinity between locations. The Duncan Multiple Range Test also signified significance for salinity and sodium. The rotated principal component Analysis (PCA) on produced water sample revealed the sources including marine intrusion, underlying rocks and crude oil. The Pearson Correlation Coefficient (r²) analysis on the produced water samples revealed high and positive significance between TDS, EC and Salinity (r²= 0.72-0.99; P<0.01). A strong correlation exists between Cd & Zn which might signify contamination from drilling.