Running Squeeze

Key Takeaways

• The primary application where running squeeze cementing outperforms stationary hesitation squeeze is the remediation of a long channeled interval where primary cementing failed to fill the casing-formation annulus uniformly: in a 500-foot interval where the primary cement job left a series of channels (mud channels not displaced from the annulus during the original job), a stationary squeeze at any one perforation point can place cement only in the immediate vicinity of that perforation, leaving channels at other depths untreated; the running squeeze pumps cement continuously while pulling the pipe from the bottom to the top of the channeled interval, delivering cement sequentially to each depth and giving the cement an opportunity to enter channels at every elevation; the coverage is not perfect (channels that are blocked by formation bridging or that receive insufficient cement per foot may remain open), but the running squeeze approach covers a large interval in a single run that would otherwise require multiple stationary operations with interim well interventions between treatments.
• The cement slurry design for a running squeeze must balance two competing requirements: the slurry must be fluid enough to be pumped at acceptable pressures through the tubing and into the formation, and it must be viscous enough to be placed in the annulus without falling away from the casing wall before it sets; a very thin slurry (low viscosity) pumps easily but may not achieve adequate annular fill because the slurry settles before gelation; a thick slurry (high viscosity) resists settling but may screen out at the perforations before the pipe has traveled far enough up the interval; slurries formulated for running squeezes typically have a thickening time (API measured in Bearden units) that allows pumping for the duration of the running operation plus an adequate safety margin, and a fluid loss that is low enough to prevent premature dehydration at the formation face while being high enough to encourage filtration-driven cement deposition in any permeable channels; the slurry design is validated by pre-job simulations using wellbore hydraulic models that account for the changing hydrostatic pressure as the cement column accumulates in the annulus during the running operation.
• Verification of running squeeze effectiveness requires a follow-up evaluation log after the cement has set (typically 24-48 hours wait-on-cement): cement bond logs (CBLs), variable density logs (VDLs), or ultrasonic cement evaluation tools (Flexus, USIT, CAST-V) are run to compare the post-squeeze cement quality against the pre-squeeze evaluation that identified the channeled intervals; an effective running squeeze shows improved cement bond quality (lower CBL amplitude, better VDL character) in the treated interval compared to the pre-squeeze log, confirming that the channels have been at least partially filled; a failed running squeeze shows no improvement or shows that cement was placed in the wrong locations (washed into the formation rather than into the annular channels); cement evaluation after a running squeeze is complicated by the presence of the freshly set remedial cement mixed with the original set cement, which can create complex log responses that require careful interpretation to separate from residual channeling.
• The running squeeze technique has specific well control considerations that differ from stationary squeeze operations: because the pipe is being pulled while cement is being pumped, the pipe must be equipped with a float collar or back-pressure valve at the bottom to prevent cement from flowing back up the inside of the pipe when pumping stops at the end of a single connection; the well must be in a stable condition (no active formation fluid influx) before the running squeeze begins, because the simultaneous pumping and pipe movement makes it difficult to monitor for kick indicators and to respond quickly if a well control event develops; the cement in the annulus creates a progressively increasing hydrostatic pressure as the job proceeds, which may inadvertently fracture the formation if the placement rate is too high or if the annular fluid is heavier than anticipated; the operational risk management for a running squeeze includes a detailed pre-job hydraulics simulation, clear maximum allowable pump rate guidelines derived from the formation fracture gradient, and dedicated well control standby procedures for the case where the running operation must be aborted before completion.
• Economic comparison between running squeeze and stationary hesitation squeeze programs for long-interval remediation shows that the running squeeze typically requires fewer well interventions and less rig time to treat a given length of channeled cement, at the cost of higher cement volume per job (because the running squeeze covers the entire interval rather than treating spot locations selectively); for a 500-foot channeled interval requiring remediation, three stationary squeezes at selected perforation depths might treat 150-200 feet of the most critical sections in 3-4 rig days, while a single running squeeze covers the full 500 feet in 1-2 rig days but uses 3-4 times more cement slurry; the choice between the approaches depends on the specific geology (whether channels are localized or distributed), the rig rate (which determines the economic weight of rig days versus cement cost), and the remediation quality required (whether partial interval coverage is adequate for zonal isolation or whether comprehensive coverage is needed for regulatory compliance with fresh water protection requirements).