Improve Zonal Isolation with Surface Pressure Pulses
Cement pulsation is the application of low-intensity
pressure pulses to the annulus after a primary cement job to
break the gel strength development in the cement slurry. Gel
strength of the cement causes a lowering of the hydrostatic
pressure transmitted through the annulus. By breaking the gel
strength, the hydrostatic pressure on the formation is
maintained until the cement has built sufficient strength to
prevent the influx of reservoir fluids through the cement
matrix.
Field Operation
The patented cement pulsation process starts
immediately after cement pumping stops and the annular
BOP is closed. Low pressure pulses, typically in the
range of 80 to 200 psi, are applied to the casing
annulus at a time interval of 30 to 60 seconds. Pulsing
continues until the compressible volume levels off or
the laboratory thickening time indicates the cement has
reached 70 BC; usually in 4 to 6 hours.