What are the reasons for using packer?

Packer is a downhole tool used for layering in oil production engineering. An oil production channel is designed on the packer. When setting, the piston sleeve goes up and the oil production channel is opened; After setting, the upper pressure acts on the balance piston and pushes the rubber cylinder upward to prevent the unsealing pin from shear force; During unsealing, the unsealing pin is cut off by the friction between the rubber cylinder and the casing, the piston sleeve goes down, and the oil production channel is closed. Advantages: it reduces the water plugging construction process of oil well packer, can easily realize the operation without killing and blowout, can bear high pressure in both directions and has long service life. The cup packer commonly used in oil field is self sealing. The outer diameter of the leather cup is larger than the inner diameter of the casing. The packer is sealed by the interference fit between the leather cup and the casing. When running down the well, the resistance is large, and the leather cup is easy to wear and scratch, so it loses its tightness. With the in-depth understanding of the oil layer, it is imperative to tap the potential of thick oil layer, and it also puts forward high requirements for downhole packer.

The packer is mainly composed of j-groove transposition mechanism, mechanical slip, rubber barrel and hydraulic anchor. When RTTS packer goes down the well, the friction pad is always close to the inner wall of the casing, the lug is at the lower end of the transposition groove, and the rubber cylinder is in a free state. When the packer is lowered to the predetermined well depth, first lift the pipe string to make the lug to the upper position of the short groove. While maintaining the torque, lower the pipe string and add compression load. As the right-hand pipe string makes the lug from the short groove to the long groove, the lower mandrel moves downward during pressurization, the slip cone moves downward to open the slip, the edges and corners of the alloy block on the slip are embedded in the casing wall, and then the rubber cylinder expands under pressure until both rubber cylinders are close to the casing wall to form a seal.

When the test negative pressure difference is large, and the pressure below the rubber cylinder of the packer is greater than the hydrostatic column pressure above the packer, the lower pressure will be transmitted to the hydraulic anchor through the volumetric pipe, so that the hydraulic anchor tile is opened, and the alloy slip teeth on the slip face upward, so that the packer can be firmly sealed on the inner wall of the casing to prevent the upward movement of the string. If the packer is pulled out, it only needs to apply tensile load, first open the circulating valve to balance the upper and lower pressure of the rubber barrel, and the hydraulic anchor slip will automatically retract, and then continue to lift up. The rubber barrel will release the pressure and return to the original free state. At this time, the lug will automatically return to the short groove from the long groove along the inclined plane, the cone will go up, and the slip will retract, so that the packer can be pulled out of the wellbore.

Application of packer:

1. In drilling operation: as type bridge plug or recyclable bridge plug, operation packer or type cement retainer.

2. In the test operation: separate the test interval from the drilling fluid and other intervals.

3. In cementing operation: as a packer outside the pipe, avoid formation fluid channeling caused by drilling fluid channeling and micro gap.

4. In perforation operation: maintain gas pressure.

5. In the operation of stimulation measures: provide conditions for water injection, steam injection, measure transformation, plugging and channeling sealing.

6. In the production string: provide conditions for oil and gas production.

7. It plays the role of sealing, circulation and separation in gravel packing and sand control.

Packer stuck reason:

During the test, the hydraulic anchor cannot return normally when the packer is unsealed, resulting in the RTTS packer being stuck. The common reasons are roughly as follows:

1. Casing corrosion deformation: under the long-term immersion of formation fluid and rock stratum extrusion, the oil layer casing will usually deform or corrode to varying degrees. If RTTS packer just sets the damaged section of casing, the hydraulic anchor slip teeth may be deeply embedded in the casing wall and cannot return, resulting in difficulty in unsealing.

2. Sand Jam: formation sand production and sand deposition not caused by well flushing will accumulate on the upper part of the packer, so that the hydraulic anchor cannot return smoothly during unsealing, resulting in the packer being stuck.

3. Falling objects stuck: falling objects fall into the upper part of the annular packer, which will also cause the packer to be stuck and cannot be unsealed.

4. Releasing method of RTTS packer

Annulus pressurization and active unsealing is a common method for RTTS packer not unsealing normally.