Fibers are commonly used as lost circulation materials (LCMs) during cementing. Their evolution began with 2-in. long natural fibers, and glass fibers 3-mm long are now available to the industry to address lost-circulation issues.
A major operator needed to cement 5-in. production liner in a depleted reservoir in the Gulf of Suez (GOS). The equivalent circulating density (ECD) exceeded the fracture gradient of the formation while circulating more than 1.5 bbl/min of mud. Losses were predicted during the cementing and an effective LCM added to the fluids was necessary to minimize the loss. A higher concentration of conventional fibers was not recommended because they can block the floats or area around liner-hanger slips.
A new spacer and slurry design was formulated using two different types of LCM systems to help minimize losses during cementing. Both types have minimal chances of blocking restricted flow areas inside pipe. These LCMs help minimize risk of plugging floats or liner hangers, particularly in slim liners where the ID of float valves is only a couple of inches. Powdered LCM was used with the spacer only because it can affect cement slurry properties. This LCM can be used in at least two to three times higher concentrations than conventional fibers. The main objective of using it with spacer was to seal any loss zone before cement began entering into that zone. A different type of inert glass-fiber LCM was used with the cement slurry, but in lower concentrations, to provide extra safety measures for curing losses. The combination of these two fibers helped cure losses from a state of complete loss, to minor losses; later, no remedial jobs were required. This paper summarizes job design and lessons learned from this successful job, which can be applied globally, specifically for slim-liner jobs.