Title : New scale dissolver for the removal of elemental metal deposits
Abstract:
The formation and deposition of mineral scales during energy production is a well-known issue in the oil and gas industry as well as the geothermal sector. Mineral scales can cause several issues ranging from formation and equipment damage, production delays, to loss of time and resources leading to expensive remedial solutions. The use of chemical scale dissolvers in dissolving oilfield scale is a well understood concept which is widely researched and implemented. While some mineral scales can be seen as easy to dissolve especially for acid soluble scales like calcite, some mineral scales are more challenging to remove once formed. One of these types of scale is elemental metal deposits like lead which forms as a thin layer on equipment and tends to be radioactive due to the transportation of lead-210 (210Pb) radioisotope from the reservoir to the surface. Radioactive metal deposits present additional safety risks and environmental restrictions in their removal and handling. There are currently limited dissolvers specifically designed for the safe removal of radioactive lead so acid dissolvers are typically used. This work focused on the evaluation of a newly developed scale dissolver designed primarily for dissolving radioactive lead deposits under surface and downhole temperature conditions applicable to both oil and gas and geothermal environments. Static soak tests were performed in the lab using lead shots at 20 - 22°C and 160°C respectively. The corrosivity of the dissolver against various metals, elastomers and thermoplastics commonly used in the oilfield was also evaluated. The dissolution results showed that at 20 - 22°C, the dissolver with the addition of <10% of hydrogen peroxide as a catalyst, can dissolve metallic lead up to 10grams per liter and up to 31grams per liter at 160°C without the addition of a catalyst. The rate of dissolution was also tracked at 20 - 22°C within a 24-hour period, which showed that 18% of a 1-gram lead shot sample had dissolved within the first 2 hours.
