Composite plugs are plugs that are specially designed and manufactured using composite materials such as thermoplastics, epoxy materials, resins and provides zonal isolation of the wellbore during multistage simulation treatments. As there can be multiple layers of hydrocarbon reservoirs below one another at different depths, these composite plugs helps in isolating these hydrocarbon zones. When an operator needs to access the second reservoir layer which is below the first one, operator can simply perform plug-and-perf operation and consume these composite plugs using a drill bit and drill further to reach to the second reservoir layer. Thus, composite plugs are also consumable components that provide zonal isolation between two hydrocarbon zone in a vertical, deviated and horizontal drilled wells.
The other name for Composite plugs are Frac Plugs. These tools are rated to be used in the environment having high temperature and pressure such as up to 180oC and 12,000 psi pressure.
Composite plugs consists of flowing components:
· Lower Slip
· Lower Cone
· Moulded Element System
· Mule Shoe
· Upper Slip and Cone
These composite plugs once set at their positions are simple to operate. It is mounted on a wireline adapter kit and run inside on the setting tool and pumped downhole to perform zonal isolation before zonal stages are fractured. Its rigid slips and an internal shear ring prevent pre-setting. A pump down ring minimizes the fluid needed to transport the plugs to depth. Once the plug is reached to the desired depth, an electrical signal is initiated from the wireline adapter which ignites a power charge and thus exerts pressure on the setting tool which further creates pressure on the outside components of the plug. Because of this pressure, plug prevents element extrusion and creates a robust seal. After the element is compressed to the near full potential, the plugs internal shearing shears.
This action releases the upper and lower slips causing the slip pads to shift and allowing the wickers to engage the casing and prevents chipping. When the outside components are fully compressed, the setting tool is released from the plug. With the plug set at its position and zone isolated, the bottom most gun is fired creating perforation clusters. Once, this is done, the wireline adapter kit holding setting tool can be removed from the wellbore and fracturing operations can be started. To block the plugs, a frac ball is dropped from the surface that closes the check valve of the composite plug or frac plug. When the fracturing operation is complete, the composite plug can be milled out with the help of millers passed through coiled tubing umbilical.