BAKER HUGHES - Drilling Fluids Reference Manual

FLUIDS ENVIRONMENTAL SERVICES
Casing Program
The casing program is developed once the injection zone and sealing formations have been identified.
The cement integrity of the surface casing defines the upper sealing boundary of the injection zone
and the top of cement for the intermediate casing string provides the lower boundary.
It should be borne in mind that the injection plume takes the path of the least resistance, and
ac cordingly, will likely be initiated at the casing shoe and could grow vertically upward and outward
from that point, depending on a variety of conditions. For this reason, the casing shoe needs to be set
at an adequate depth below the top of the specified injection zone.
In theory, the height of the top of the cement for the intermediate casing string is planned such as to
make certain that the length of exposed formation will allow for desired downward fracture growth.
Experience in designing the subsurface injection profile and related casing/cement programs is
paramount to successfully implement the technology. To ignore the required engineering experience
and judgment in this phase of the operation and in later evaluation of formation changes will result in
failure.
Monitoring Procedures
No matter how well the project is planned there is always the possibility of a breakdown which may
result in disposal failure. Negative impacts on the existing drilling program, on future wells and to the
environment are risked if proper quality control of the slurry and the surface operation is not
maintained. The quality control procedures should monitor, at minimum, the following:
• Pressure impact on nearby wells.
• Disposal plumes, direction and location.
• Injection rate, total volume and pressure.
• Disposal slurry properties, density, funnel viscosity, rheological properties and particle size.
• Equipment condition.
• Experience level of operators/management.
In many cases, a meeting with the appropriate regulatory agencies will not be necessary, but adequate
communication is always crucial to gaining the agency’s understanding and approval. Obtaining early
regulatory input has two primary advantages:
• Allows the operator to comply with pertinent regulations.
• Provides the operator with an opportunity to hear concerns of regulatory personnel so that
special needs can be addressed and appropriate changes made to the work plan.
Early dialogue makes it possible to resolve concerns and issues while developing the cuttings
injection plan.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 14-39