Abstract
The accumulation of Naturally Occurring Radioactive Materials (NORM) in the scales formed on different production facilities is a well known problem in the oil and gas industry. In the year 1998, NORM was identified to be an issue in some Libyan land based oil fields. The naturally occurring radioactive materials (NORM) involved in this matter are radium isotopes ( 226Ra and 228Ra) and their decay products, precipitating into scales formed on the surfaces of production equipment. A field trip to a number of onshore Libyan oil fields has indicated the existence of elevated levels of specific activity in a number of locations in some of the more mature oil fields. In this study, oil scale samples collected from different parts of Libya have been characterized using gamma spectroscopy through use of a well shielded HPGe spectrometer. In accordance with safe working practices at the University of Surrey to avoid potential alpha-bearing dust inhalation, the samples, contained in plastic bags and existing in different geometries, are not permitted to be processed. MCNPX, a Monte Carlo simulation code, is being used to simulate the spectrometer and the scale samples in order to obtain the system’s absolute efficiency and then to calculate sample specific activities. The samples are assumed to have uniform densities and homogeneously distributed activity. Present results are compared to two extreme situations that were assumed in a previous study: (i) with the entire activity concentrated at a point on the sample surface proximal to the detector, simulating a worst-case scenario, and; (ii) with the entire activity concentrated at a point on the sample surface distal to the detector, simulating the most optimistic-case scenario.