Mr. Erik Milito - The House Committee on Natural Resources ...

ISOLATING POTENTIAL FLOW ZONES DURING WELL CONSTRUCTION 79
Critical Cement Slurry Parameters
Cement serves as an isolation medium during well construction. <strong>The</strong> design of the cement slurry, taking into account the
anticipated well conditions, is central to successfully isolating potential flow zones. Lead and tail cement slurries designed to
isolate potential flow zones should be fit for their intended purpose.
Cement
Compressive or
Sonic Strength
Wellbore Barriers:
Cement Plugs
Temperature for
Cement Testing
Slurry Design
(lead vs tail slurry)
Cement shall be considered a physical barrier element only when it has attained a minimum of 50 psi
compressive or sonic strength as measured at simulated pressure and temperature conditions (within the
limits of the laboratory equipment) at the uppermost flow zone.
Once the time to reach a minimum of 50 psi compressive or sonic strength has been determined by lab
tests for the specific cement slurry, the operator shall wait on the cement to set for that amount of time prior
to removing or disabling a barrier element.
Slurry properties shall be consistent with any regulatory requirements.
Testing shall comply with accepted industry standard practices.
Have temperature schedules been established based on methods contained in API RP 10B-2/ISO 10426-
2, direct measurements, computer modeling and/or offset well data
Has the lead slurry been designed so that the static gel strength development and thickening time are
longer than for the tail slurry, including applicable (batch) mixing and placement times
Slurry Design
(static gel strength)
Have the cement slurries, placed across potential flow zones, been designed to have as short a CGSP as
possible, preferably less than 45 minutes, at the temperature and pressure conditions found at the potential
flow zone
Slurry Design
(rheology)
Slurry Design
(fluid loss)
Slurry Design
(density)
Slurry Design
(stability)
Slurry Design
(compatibility)
Slurry Design
(mechanical
properties)
Slurry Design
(field blend
verification)
Slurry Design
(mechanical
barriers)
Are the rheological properties of the slurries conducive to surface mixability, drilling fluid removal and ECD
management with respect to fracture pressure
Does the fluid loss of the slurry placed across potential flow zones have appropriate control for the flow
potential
Does the slurry density meet requirements for maintaining well control
Are free fluid control, sedimentation and foam stability (when cement is foamed) appropriate for the
conditions found at the potential flow zone
Are lead and tail slurries compatible
Is the cement designed with mechanical properties suitable for long-term sheath integrity for anticipated
well operations
Have representative field blended samples been tested
Has the presence of mechanical barriers been taken into account in the slurry design and testing
Slurry Design
(formation type and
fluids)
Is the cement designed for specific formation (such as salt) and for expected formation fluids (such as
gas)
Slurry Design
(regulatory)
Slurry properties shall be consistent with any regulatory requirements.