For some wells, the spacer was also foamed to increase the sweeping efficiency, reducing hydrostatic pressure and assisting successful placement of foamed lead and conventional tail slurry. On inner-string cementing jobs, a drill pipe dart was released and latched into the float shoe to help address cement slurry residue/contamination on the walls of the drill pipe. In total, Halliburton batch-set 23 wells by mixing and pumping 96,000 sacks of cement in an offshore environment of over 8,500-ft water depth. In all, this was a very successful cementing operation with zero NPT related to the cementing operations. Permanent Monitoring and Chemical Injection Halliburton WellDynamics has supplied Shell with permanent monitoring and chemical injection systems for their subsea installations since the mid-1990s. Due to the reliability and success of these previous installations, Halliburton won the contract to supply the permanent monitoring and chemical injection systems for the Perdido project.