BAKER HUGHES - Drilling Fluids Reference Manual

FLUIDS ENVIRONMENTAL SERVICES
BEST OPERATING PRACTICES
Reducing the volume of waste and containing those substances with higher potential for pollution is
critical to improve the environmental performance under a FES system. A key area for improvement
is in the segregation and accounting of wastes. As a rule, treatment costs are higher as the
concentration of hydrocarbon increases. If wastes free from hydrocarbons are commingled with oily
residues then a larger than necessary volume of waste containing hydrocarbons is being treated.
Likewise, poor accounting at both the rig site and at the waste treatment center could lead to
differences between volume of waste sent and received. It is important that it is realized that all waste
is not the same and even though it is waste, it needs to be tracked as carefully as any other asset. This
is of particular importance to the operator as it is related to liability, duty of care and ownership of
any waste.
Volume Reduction
An important part of the FES strategy is to reduce the overall volumes of fluids produced from the
drilling and completion of each well. By reducing excess volume there will be a corresponding
reduction in waste, bringing further cost benefits.
The main sources of excess fluids volume are:
a) Discharges of WBM
• Limited fluids recycling and reuse.
Water based drilling fluids by their nature are more readily biodegradable and have a shorter “shelf
life” than oil based drilling fluids. As they are generally less inhibitive than OBM they tend to
become solids laden more readily and require expensive separation processes to remove the
incorporated drilled solids.
In the past very little effort was spent on evaluating the economical and environmental potential of
reusing WBM fluids in offshore operations. This was primarily due to the perception that the
incremental cost of shipping, reconditioning and storing these fluids would be prohibitive. This is
particularly evident when the water-based system is being replaced by an oil based system. Many
drilling installations do not have the capacity or the facilities to handle two types of drilling fluids
simultaneously and marine vessels do not have sufficient tanks to transport both systems
independently.
For onshore operations, dewatering techniques are used in the closed loop mud systems (CLMS) as
an alternative to direct discharge of WBM drilling fluids. This process eliminates the use of reserve
pits and recirculation pits or sumps, in the treatment and removal of drill solids from drilling fluids.
The dewatering techniques used in this process combines conventional solids control equipment with
chemically enhanced dewatering methods to remove the ultra-fine solids from the drilling fluid and
dispose of it as a dry waste. The application of these techniques has grown in usage to become an
integral part of routine drilling operations.
Dewatering methods were initially used to treat the liquid drilling waste in a reserve pit, removing the
solids and discharging the cleaned fluid. As the economic and environmental pressures grew to go to
a CLMS operation, the use of coagulation and flocculation chemical technology in conjunction with
decanting centrifuges and specialized dewatering equipment became the preferred method for drilling
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 14-20