Completion design in hydraulic fracturing determines how fractures are placed along the wellbore and how different stages are isolated during stimulation. In horizontal wells, multistage fracturing is commonly used to maximize reservoir contact. The most widely used completion techniques include plug-and-perforation, open-hole completions, and sliding sleeve systems.
Plug-and-Perforation (Plug-and-Perf)
Plug-and-perforation is one of the most widely used completion techniques in hydraulic fracturing and is a cased-hole approach. In this method, a bridge plug and perforating gun are conveyed to the desired stage in the wellbore. Once the plug is set, the perforating gun creates holes in the casing and cement, establishing communication with the reservoir.
Hydraulic fracturing is then performed by pumping fluid through the perforations into the formation. After completing a stage, another plug is set, and the process is repeated sequentially from the toe of the well toward the heel. Once all stages are fractured, the plugs are removed by drilling or milling to allow production.
This method provides high flexibility in stage placement and is widely used due to its reliability and control over fracture initiation.
Sliding Sleeve and Open-Hole Completions
Sliding sleeve systems are commonly used in open-hole completions and are designed to improve operational efficiency during multistage fracturing. In this approach, the well is completed without casing across the reservoir section, and sliding sleeve tools are installed along the wellbore.
Each sleeve corresponds to a specific stage and can be opened sequentially, typically using ball-drop activation. Once a sleeve is opened, fracturing fluid is pumped directly into the formation at that location. This allows multiple stages to be fractured in a single continuous pumping operation without the need for repeated plug setting and perforation.
This method significantly reduces completion time and operational complexity. However, it offers less flexibility than plug-and-perforation systems, as stage locations are predetermined and cannot be easily modified during the operation.
