Multistage completions have long been used for the selective stimulation and production of different zones of interest. These completions rely mainly on ball activated sleeves that allow access to each zone individually. In the pursuit of unconventional reserves, optimizing well operations became inevitable. Such optimization requires innovative solutions that rely on the latest technology with the aim of reducing cost and time of operation.
Solid and degradable balls are rivals when it comes to activating the sleeves of multistage completion systems as wells the temporary zonal isolation. For long, solid balls were favoured and regarded as a safe option for their consistency as they maintain their characteristics throughout the whole operation. Degradable balls were regarded as unreliable due to the fear of immature degradation which is considered a nightmare as it may jeopardize the whole operation. The rate of ball degradation is affected by the salinity and temperature of the surrounding fluid.
Clearing the wellbore of any restriction during the production phase dictates milling all solid balls which is usually accompanied by several challenges including the risk of getting the milling assembly stuck as well as the time lost during the operation. Such challenges revived the discussion about the need for alternatives. In order to consider a degradable ball reliable for implementation in any specific well, lab tests simulating down hole conditions are necessary in order to obtain information about the rate of degradation relative to the duration of the operation.
This paper discusses the implementation of multistage completion systems in seven wells where activating the sleeves relied mainly on the use of solid balls until degradable balls were introduced revolutionizing the whole application. From reduced operational time to avoiding all challenges associated with milling, degradable balls proved reliability and effectiveness. The paper will focus on the process through which degradable balls were introduced as an alternative to solid balls including the planning, testing and execution phases.