High Specific Gravity, Ultrafine Particle Size and Acid Soluble Manganese Tetra Oxide Succeeds in Replacing Heavy Brines as Completion and Workover Fluid

A high-density completion and workover fluid (18-20 ppg) was required for deep high-pressure gas wells. The traditional clear completion brines, which provide a solids-free environment to run and set downhole completion equipment were evaluated and were not approved as they came with an expensive price tag and, more importantly, they came with serious health, safety, and environmental concerns in addition to formation damage concerns. The available alternative barite weighed water-based mud (WBM) was used as completion fluid to set lower completion; however, due to the concentration and size of the solids contained in this system, serious issues became evident. These included leaks due to poor sealing, string plugging, and stuck completions due to barite settlement issues. Manganese tetroxide (Mn3O4) was evaluated as an alternative to barite as it has higher specific gravity and a much smaller particle size. To overcome all limitations of brines and barite WBM, and achieve the required density for well control purposes, to address this issue, rigorous lab work was performed to formulate a completion and workover fluid with viscous sodium chloride brine. Additional density was achieved with manganese tetroxide (Mn3O4). Manganese tetroxide has a very low SAG index due to its ultrafine particle size. The small size of manganese tetroxide (Mn3O4) eliminated the solids sag and settlement issues that were associated with barite weighed fluid and allowed for longer static fluid periods without the need to interrupt operations to circulate and condition the fluid saving significant time lost on sorting out all barite sagging related issues in previous completion and workover operations. This paper presents laboratory design data and comparative data where this type of high-density fluid is used to successfully run lower completions and perform successful workover operations in gas wells without any problems.