BAKER HUGHES - Drilling Fluids Reference Manual

FLUIDS ENVIRONMENTAL SERVICES
• How significant an impact will the cuttings slurry have on nearby wellbores/formations?
• How will the cuttings slurry affect existing wells and future drilling plans?
• What volume of cuttings slurry can be safely disposed of?
• What forces will be put on the well casing?
• How can the cuttings slurries be injected in order to minimize formation impact?
• How can the annulus and the formation be protected?
• When the formation changes, what does the CRI operator do next?
Lithology Concerns
An accurate description of the various lithologies and the transition depths from one lithology to
another is integral in determining where injection of the cuttings slurry should take place.
The disposal formation must be able to readily accept the cuttings slurry, and must also be massive
enough to accommodate the volume of cuttings produced.
The target formation should not contain natural fractures or faults that might communicate the slurry
to the surface or to formations containing potable water. Additionally, the disposal formation must be
associated with some type of seal mechanism that will adequately restrict the slurry to the specified
formation interval.
A review of mechanical property logs, cores, leak off tests, pore pressures, mud logs and other data
from offset wells is a very useful tool when addressing these issues. Fracture modeling, although
currently designed for hydrocarbon stimulation operations, has proven useful for estimating the size
and shape of the disposal plumes.
Seismic data can be utilized for identification of natural vertical fracturing that could make the project
fail and can be utilized to define the formation properties, such as fracture pressures, pore pressures,
and other elements crucial to CRI.
Surface Equipment Requirements
The type of surface equipment required to process the drilled cuttings is based on a number of
parameters established after addressing downhole considerations. The properties of the drill cuttings
dictate the type of grinding equipment required. Modified centrifugal pumps designed to reduce the
size of the cuttings using high shear rates are most effective when processing cuttings from soft,
hydratable shale formations. All modified centrifugal pumps are not the same. In those instances
where a sizable quantity of hard cuttings will be processed, the use of a mechanical grinder should be
considered.
Proven equipment durability, manpower, requirements, utilities, ease of installation/time requirements
and contingency plans must all be considered when designing the surface equipment system. Proper
system design is important since any downtime for repairs or maintenance directly impacts the
drilling process. In zero discharge operations, the rig cannot drill if the CRI surface equipment is not
adequately designed and installed to stay ahead of the drill rate/surge conditions. The costs
associated with CRI increases rapidly when the drilling
progress is negatively impacted.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 14-38