Squeeze Cementing Procedure
The general sequence of events during a typical low-pressure squeeze job involving casing perforations include the following:
- Zones below the interval to be squeezed are isolated with a retrievable or drillable bridge plug or cement retainer.
- The perforations are washed or back-surged with the appropriate tools.
- A retrievable squeeze packer is run into the hole on the work string, set at the desired depth above the perforations and pressure-tested. Special care must be taken regarding the packer setting depth, which will vary depending on where the bottom end of the tubing is relative to the perforations. Usually, the packer should be set 30 to 60 ft from perforations. If corrosion holes or split pipe are being squeezed, more space is recommended.
- An injection test is performed using clean, solids-free water or brine.
- A lead spacer fluid, followed by the cement slurry, is circulated via the packer bypass with care taken to avoid squeezing fluids ahead of the slurry into the formation. A small amount of backpressure is maintained on the annulus to avoid cement slurry free-fall in the work string as a result of U-tubing.
- The packer by-pass is closed 2 or 3 barrels before the slurry arrives at the packer.
- Squeeze pressure is applied and pumping continues until no pressure leak-off occurs. The squeeze is then tested at a pressure that exceeds the final injection pressure, typically about 500 psi above final injection pressure.
- It is desirable to test and then maintain some pressure on the casing annulus above the packer. Observing this pressure can be a check for leaks in the squeeze string, packer, or casing. Annulus pressure can also prevent casing-collapse during high-pressure jobs.
- Pressure is bled off, the packer bypass is opened, and any excess cement is reversed out by circulating down the annulus and up the work string. Clearing excess cement from the casing opposite the perforations can be achieved by releasing the packer and lowering the work string during reversal.
- Tools are retrieved and the well is left undisturbed until the cement cures.
The parameters that must be monitored during a cement squeeze include:
- Density and remaining volume of fluids as they are pumped
- Pressure and pump rate
- Volume and density of fluids returned through the annulus
During the job, these data are recorded (Figure 1) and analyzed in real time to support decision-making: continue squeezing, increase pressure, stop squeezing, start cleanup.
Cleaning out the excess cement in the casing after a squeeze job avoids the added cost of a trip with drill pipe and bit to drill out the cement after curing, but it adds the risk of disturbing the cement “nodes” in the plugged perforations and jeopardizing the job’s success.
