A bridge plug is a tool used in downhole applications in the oil drilling industry. Downhole means that the bridge plug is used in a subsurface manner, meaning it is applied into the wellbore, or underground, to stop a well from being used. A bridge plug has both permanent and temporary applications, which means it can be applied in a fashion that permanently ceases oil production occurring from the well it’s applied to, or it can be manufactured in a manner which makes it retrievable from the wellbore, thus allowing production from the well to resume. They can also be used on a temporary basis within the wellbore to stop crude oil from reaching an upper zone of the well while it’s being worked on or treated.
Bridge plugs are typically manufactured from a number of materials that each have their own applicable benefits and disadvantages. For instance, bridge plugs made out of composite materials are often used in high-pressure applications because they are able to withstand pressures of 18,000-20,000 psi (124-137 MPa). On the other hand, their permanent use tends to lend itself to slippage over time due to the lack of bonding between the composite materials and the materials inside the wellbore. Bridge plugs fabricated out of cast iron or another metal may be perfect for long-term or even permanent applications, however, they don’t adhere very well in high-pressure situations.
Bridge plugs don’t just get placed in a wellbore and left to plug the end, however. In fact, placing a bridge plug within a wellbore to either permanently or temporarily stop the flow of oil or gas is an intensive process that must be done tactically and skillfully. It must be done while utilizing a bridge plug tool that is specially designed to place bridge plugs in an efficient manner.
The tool used to place the plug usually has a tapered and threaded mandrel that is threaded into the center of the bridge plug and has compression sleeves placed in succession with each other so that as the tool engages the plug, the sleeves compress around the plug and the tool rotates the plug downhole into the wellbore. When the bridge plug is at the desired depth, the tool is disengaged from the axial center of the plug, and unthreaded from the cylinder. The tool is removed from the wellbore with the plug being left in place, as the sleeves have decompressed once the tool no longer has the plug engaged.