Statistical Analysis of Geothermal Data of an Oil Field, in Parts of Niger Delta, Nigeria

Abstract

Geothermal gradient and heat flow were computed from bottom hole temperatures in an oil field in Niger Delta, Nigeria. The statistical analysis of computed geothermal data was carried out. The computed geothermal gradient vary from 17.3±0.14 to 24.33±0.70°C/Km with an average of 22.24±0.57°C/km. The heat flow ranges from 38.06±0.31 to 56.39±2.41 mWm^-2 with an average of 50.15±1.25 mWm^-2. The computed variance of the geothermal gradient and heat flow are 0.499 and 2.447 respectively. The standard deviation for the geothermal gradient and heat flow are also 0.79 and 1.564. The values of the geothermal gradient and heat flow are low in the south and high in the northern parts of the field. The geothermal values increase towards the north. The possible causes of geothermal anomalies are variation in thermal conductivity, presents of geological structures such as growth faults and rollover anticlines and movement of fluid in the subsurface. The least geothermal gradient and heat flow values occur in the edge of the south east region. The region with high heat flow may be attributed to low sedimentary thickness while area with low heat flow may be associated with high sedimentary thickness. The geothermal analysis shows that the sediments in the area has attained hydrocarbon generation stage of temperature interval of 150 to 300°F (65 to 150°C). In the concept of the hydrocarbon-liquid window, the depth range within which liquid hydrocarbons are likely to be present is 1550-4500 m.