A SIMPLER, MORE EFFECTIVE METHOD FOR CEMENTING SURFACE CASINGS IN SHALLOW GAS ZONES

摘要

Cementing upper casing strings in wells that traverse shallow gas sands has been a troublesome process. Because these top zones are often weak, high-density slurries that are gas-tight cannot be used. When a combination of low-density lead slurry and high-density tail slurry is used to reduce hydrostatic pressure and prevent lost circulation, high concentrations of cement additives are required to make the lead slurry gas-tight Statistically, a significant number of cement-job problems are associated with the transition from low slurry density to high slurry density. Eliminating this transition point improves cementing operations by maintaining consistent slurry density.