Variation in well-head gamma radiation levels at the Nigerian Petroleum Development Company oil field, Ologbo, Edo State, Nigeria

Gamma radiation levels at the well heads in the Nigerian Petroleum Development Company Oil Field located at Ologbo in Edo State of Nigeria have been investigated using a Digilert 50 Radiation Geiger Muller Counter. The sites investigated include one heavy crude oil producing well (A), one light crude producing well (B) and a shut-down gas well. Diurnal measurements were made in the morning and afternoon periods on selected days during the dry and wet seasons between 2002 and 2004. The mean dose rate varies from one well head to the other. It is (17.22 ± 0.36) x 10-12m Sv/hr at the heavy crude well head and much lower (14.30 ± 0.46)x 10-12mSv/hr for the light crude, while the shut down gas well gave (17.26 ± 0.46)x 10-12mSv/hr. It is found that the difference between the morning and afternoon radiation levels is within 68% significance level. The mean exposure rate for the dry season however seems to be consistently lower than that of the wet season. It was generally observed that the level of radiation around the well heads is less than 20x 10-12mSv/hr, which is in agreement with the International Atomic Energy Agency\'s standard on ionizing radiation background level. Keywords: Radiation, crude oil, radionuclide, contaminant, exposure Nigerian Journal of Physics Vol. 18 (1) 2006: pp. 135-14