BAKER HUGHES - Drilling Fluids Reference Manual

FLUIDS ENVIRONMENTAL SERVICES
• Particles are small in size, soft/ductile in nature.
• Pumped at low rates for long periods of time.
• Purposely designed to keep the fluid horsepower low.
• Generally high in fluid loss.
• Designed to impact the formation minimally - large fractures are not desired.
Injection Process
A fter a homogeneous slurry is prepared and conditioned to site specific properties, the cuttings slurry
is then injected through a dedicated conduit, such as the annular space between two strings of casing
(annular injection) into the exposed formation. The cutting slurries are pumped at planned rates into
the formation.
When the pressure increase resulting from the pumping operation exceeds the strength of the exposed
formation rock and the natural pore pressure, the formation allows the cutting slurries to flow into the
formation. If the rheology/physical properties and pumping methods are correct, the formation will
safely hold large amounts of cuttings.
Operating Considerations
A variety of operational details must be dealt with to properly plan the project. Successful operations
dictate that the majority of the work is done in the planning stage. Some of the details include:
• Identifying suitable cuttings disposal/sealing formations.
• Selecting surface equipment.
• Designing the casing programs.
• Designing the injection programs and contingency planning.
• Plug prevention in the annulus and the formation.
• Preventing cutting slurries from breaching to the surface or contaminating potable water
zones.
• The impact on existing producing wells or future wells to be drilled.
• Quality control/monitoring of injection procedures
• Abandonment of waste disposed to permanently entomb the waste.
• Obtaining regulatory approval.
Characteristics of the subsurface environment, sealing formations, injection zone, slurry properties,
drilling plans, subsurface slurry disposal dimensions and other elements directly impact each of these
operational considerations. Of the various technical details that must be evaluated, the least
understood but of equal importance, are those questions associated with downhole considerations:
• Into what formation can the cuttings slurry be injected?
• How will the cuttings slurry be contained?
• In what direction will the cuttings slurry propagate? And how
far?
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 14-37