Composite cement systems for encapsulation of barium sulphate scale from oil industry and application as high density support matrix

Radioactive barium sulphate scales raise a serious concern in the oil and gas industries. They are often classified as low level radioactive waste, but there are no clear methodologies established world widely to deal with this well know issue. The present study investigates a potential use of composite cement systems based on Portland cement to encapsulate the barium sulphate scales, aiming to provide a feasible option for safe handling, storage and disposal. The investigation was conducted on three different aspects: basic formulation, wasteform development and potential use as a high density support matrix.
The first part studied the basic formulation to clarify the impact of BaSO4 loading and water contents on the physical properties of the composite cementing system. Fine BaSO4 powders and excess water were found to influence the product phases whereas coarse BaSO4 particles showed larger impact on strength of the products. The second part investigated the effect of mineral admixtures to develop practical wasteform formulations. Fine BaSO4 powder, metakaolin and quartz were found to improve the workability of the pastes as well as the microstructure by eliminating highly porous interfacial transition zone, resulting in the higher compressive strength and reasonable leaching rates of elements. Addition of quartz was found to be most effective to minimise the degradation caused by the high temperature environment, by initiating the formation of stable tobermorite phase.