• Casing protection • Separation of multiple zones • Isolation packers • Elimination of surging and heading • Sub-surface safety control • Artificial/gas lift • Suspend the weight of tubing when there is compressive load on the tubing string There are three types of packers: mechanical and hydraulic set and permanent. All packers fall into one or a combination of these.
Mechanical set packers are set by some form of tubing movement, usually a rotation or upward /downward motion. Others can be weight set—the tubing weight can be used to compress and expand the sealing element. By a simple up string pull the packer is released. It is used best in shallow low pressure wells that are straight. It is not designed to withstand pressure differences unless a hydraulic hold down is incorporated.
Tension-set packers are set by pulling a tension on the tubing, slacking off releases the packer. Good for shallow wells with moderate pressure differences. The lower pressure helps to increase the setting force on the packer. Used in a stimulation well.
Rotation-set packer – Tubing rotation is used to set the packer to mechanically lock it in; a left-hand turn engages and a right-hand turn retrieves it.
Hydraulic-set packers use fluid pressure to drive the cone behind the slips. Once set they remain set by the use of either entrapped pressure or a mechanical lock. They are released by picking up the tubing. They are good for use in deviated or crooked holes where tubing movement is restricted or unwanted. The tubing can be hung in neutral tension.
Inflatable packers - use fluid pressure to inflate a long cylindrical tube of reinforced rubber to set the packer. Frequently used for open hole testing in exploration wells and for cement assurance in production wells. Also used in wells where the packer must pass through a restriction and then set at a much larger diameter in casing or open holes. Many variations for specific applications are available including those capable of withstanding high pressure differentials.
Permanent packers are run and set on an electric wireline,
drill pipe or tubing. Opposed slips are positioned to lock it in compression. Once set this packer is resistant to motion for either direction. Wireline uses an
electric current to detonate an explosive charge to set the packer. A release stud then frees the assembly form the packer. Tubing can be used by applying rotation or a pull or a combination of both. They are good in wells that have high pressure differentials or large tubing load variations and can be set precisely. They can be set the deepest.
Cement packers – In this case the tubing is cemented in place inside the casing or open hole. This type of packer is cheap. ==Factors affecting packers==