On 27th May 2021 at around 9:00am, the Operation was circulating hole through 4-1/2” tubing at bottom prior to cementation. Mud engineer instructed mud tester to mix the caustic soda and Biocide on intermediate tank no.2 prior to backloading the mud to the mud plant. While the mud tester was attempting to mix the biocide with pre-existing caustic soda into the caustic soda device, the reaction between the two chemicals resulted in splashing the fluid on his face and body causing multiple burn injuries. First aid was administrated by Rig medic and then referred to Nizwa Hospital by PDO doctor for further medical examination