Integrated Monitoring Radon and NORM Scale: HSE Case Study Well Surveillance
- Ardian Nengkoda (Schlumberger) | Mohammad Salim Al-Hajri (Petroleum Development Oman) | Azzan Kindy | Abdulwahab Bulushi | Zeyana Yazeedi | Barry Nicol
- Document ID
- Society of Petroleum Engineers
- Abu Dhabi International Petroleum Exhibition and Conference, 1-4 November, Abu Dhabi, UAE
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 4.1.5 Processing Equipment, 5.6.4 Drillstem/Well Testing, 5.2 Reservoir Fluid Dynamics, 6.2.4 Industrial Hygiene, 5.1.2 Faults and Fracture Characterisation, 4.1.2 Separation and Treating, 6.5.4 Naturally Occurring Radioactive Materials, 4.3.4 Scale, 4.6 Natural Gas, 5.8.7 Carbonate Reservoir, 4.3 Flow Assurance, 3 Production and Well Operations
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Processes of oil production, gathering, transportation are some times accompanied by scaling of radioactive materials (NORM). As an integrated approach to identify the Radon and NORM scale as flow assurance issue, a campaign of Radon monitoring, Barium and Strontium ion analysis from produced water potential lead to NORM scale have been conducted starting from well testing and in both onplot-offplot of the oil gathering station. Chemical composition of NORM scales strongly depend on chemical composition of produced waters. Presence of considerable amount of radioactive materials on technological equipment during production and treatment of oil, and gas may lead to personnel irradiation exceeding allowable levels and creates potential hazard to environmental pollution. The role of radon and its decay products in pollution of environment and internal personnel irradiation was not practically studied. Liberation of radon with decay products from scales and their entry into atmosphere may lead to radioactive pollution of environment, which increases the risk of internal personnel irradiation. This technical paper explained how to monitor effectively potential NORM and the intensity of radon accumulation in X field Petroleum Development Oman. During well testing or intervention, the equipment of wells radiobarite precipitates on impellers of electric centrifugal pumps, tubing inside surface in the form of white films with yellowish tint. Thickness of scales on tubing surface achieves 3 mm. In long-run operation radiobarite in electric centrifugal pump is able to clogging up. As a result of this well surveillance, Radon, Barium and Strontium analysis from produced water are really helpful in predicting NORM potential.
Processes of oil production, gathering, transportation are some times accompanied by scaling of radioactive materials NORM. In example, inorganic scale build up inside the wellbore and near wellbore formation can smother a well in a very short productive period causing additional operating expenses in the range of millions of dollars. This statement is particularly true if the deposited scale is contaminated with NORM (naturally occurring radioactive materials).
In addition to loss of production and workover cost, the full set of contaminated tubulars and downhole equipment needs to be either decontaminated at designated site or to be disposed following international regulations. Both the options are undesirable from the operational complication and expenditure point of view. The NORM radionuclides are uranium, potassium, thorium, radium and radon. These elements are found in trace quantities throughout the earth's crust. These unstable radioactive elements undergo periodic decay and results in the formation of elements with different physical and chemical properties. Radium-226 which is a decay product of U-238 and Th-230 is water soluble and may therefore be found dissolved in aqueous phase associated with oilfield produced water. As far as radioactive scales are concerned, Ra-226 is the most common element responsible for radioactivity which is co-precipitated with Gr-II elements, particularly with barium as carbonates or sulphates. RaSO4 and BaSO4 have similar solubility and crystal structure hence Ra2+ substitutes for Ba2+ in the BaSO4 lattice. At lower temperatures RaSO4 is less soluble than BaSO4, increasing Ra substitution. There may be cases where Pb-210 is also a minor contributor. These types of radioactivity are also called TENR (technology enhanced natural radioactivity).
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