RELATIONSHIPS AMONG OILS AND WATER COMPOSITIONS IN NIGER DELTA.

In some fields of the Tertiary Niger delta of Nigeria, heavy, asphaltic oil is found in shallow reservoirs and light, waxy oil is found in deeper reservoirs in the same field. Both oils appear to have had the same source. The change with depth from heavy to light oil is usually abrupt and occurs at a reservoir temperature between 150 degree and 180 degree F. In other areas similar degradation of oil has been ascribed to bacteria brought into the oil reservoir by invading meteoric water. In Nigeria, meteoric water is low in dissolved solids and high in bicarbonate, whereas connate water is saltier and contains more chloride. Samples of both types of oil and associated water from six fields were analyzed and compared with previously acquired analyses from these fields. Results of this study are discussed.