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Quality HDD Support Equipment |
Drilling Fluids Recycling
by Ray Clayton
Although recycling of drilling fluids is commonplace in large diameter river
crossing applications, it is relatively new to the mini and midi-sized rigs
users. Successful recycling requires proper planning and onsite supervision. The
potential benefits are significant and are worth evaluation and consideration.
Recycling Advantages:
Advantages of recycling include:
Cleaner, safer drilling location
Reduced disposal costs
Reduced drilling fluid costs
Economical use of mud motor
Reduced water hauling
Limit truck traffic
Environment considerations
Reduced overall project costs
Recycling Process:
A recycling system cleans the returned slurry, allowing the liquid phase to be
reused and discards the cuttings. A highly efficient system can clean the
returned fluid down to a less than 1 percent sand.
Recycling Systems:
There are various types of recycling systems available. Systems can be skid or
trailer mounted. Desired processing rates determine actual components. Most
systems include these basic items:
Spoils/Slurry Pump -- This pump routes the returned slurry to the recycling
system for processing. Several types are available including gasoline or diesel
driven trash pumps, electric or hydraulic submersible pumps, vacuum from venturi,
or air pumps.
Fluids Tank -- Tank designs and sizes very as required. Most double as mixing
tanks. The cleaning equipment is mounted on top of the tank.
Shaker -- The shaker is the "first line of defense" and is the most important
element of the cleaning process. Fluid is pumped via the spoils pump to the
shaker. Larger cuttings are removed, while the liquid phase and smaller cuttings
are directed into one compartment in the fluids tank. Two primary types of
shakers are available, linear motion and elliptical motion. "Linear motion"
shakers provide finer separation efficiencies, however, they are higher priced
and utilize more expensive replacement screens.
Hydrocyclones -- (desander and desilter cones): The cleaned fluid passing
through the shaker is pumped to the cones via a centrifugal feed pump.
Centrifugal force and the cone design provide further separation. The liquid
phase exits the top of the cone and the solids are discharged out the cone
bottom.
Mud cleaners -- A mud cleaner is simply an additional shaker with desander
and/or desilter cones mounted over the top. The liquid attached to the cone
underflow is routed over the shaker and provides a "dry; solids discharge."
Hydrocyclones vs Mud Cleaners
Hydrocyclones provide superior cleaning efficiency, however discharge a soupy
discharge.
Mud cleaners provide very acceptable cleaning efficiency while providing a "dry
solids discharge."
The "dry solids discharge" of a mud cleaner provides a safer, cleaner, more
environmentally friendly drilling location and greatly reduces expensive
disposal costs. A drilling contractor must weight the options and make a
decision.
Onsite Personnel
Operation of recycling systems is easily accomplished. However, it is necessary
to have a dedicated crew member to operate the unit. Proper personnel training
and operation is essential to equipment efficiency.
Most systems double as a mixing system, therefore one man can be designated as
the "mud man" and easily handle all mixing & recycling responsibilities.
Triplex Mud Pumps
Recycling can present problems for triplex mud pumps. Contractors new to
recycling should be prepared for increased wear of pump expendables. Even the
best systems allow ultrafine solids to be recycled. The ultrafines will create
sandblasting effect on the inside of the pump.The benefits of recycling normally
greatly outweigh the costs of increased wear.
Plunger vs. Piston
Plunger pumps: Until recently, recycling has not been routine with small rigs.
Therefore, most triplex pumps utilized on mini rigs are of the plunger
configuration designed for use only on "clean fluid". This type pump is very
intolerant of recycling. Use of abrasion resistant valves & seats is beneficial.
Piston pumps: Piston pumps are somewhat more resistant to the abrasions incurred
during recycling. Piston pumps also tend to be higher volume and have larger
valves reducing the velocity of the fluid through the pump, therefore reducing
abrasion. However, a high percentage of these piston pumps are also designed as
"clean fluid" pumps.
Slurry service triplex piston pumps: These are the most preferred pumps for
recycling. Specifically designed for heavy slurries, they are very resistant of
solids versus the "clean fluid" pumps. This design pump is widely used in
oilfield drilling and in large diameter river crossing HDD projects. Slurry
service pumps are larger pumps and require more horsepower. These pumps are
generally on separate skids or on trailers as part of a self contained mixing,
cleaning and pumping system.
Equipment Performance Testing
Efficiency testing of recycling equipment is easy to accomplish onsite and
should be routine. Three common procedures are sand content test, mud weight,
and total solids content. Your local drilling fluids supplier can supply the
necessary tools to perform these tests.
Ray Clayton, vice president of Tulsa Rig Iron Inc., Kiefer, Okla., has 18 years
experience in liquid solids separation. The Drillmaster Reports are reviewed by
a team of seasoned drilling professionals: Frank Canon, Baroid Industrial
Products; Mark Van Houwelingen, Vermeer Mfg.; and Jerry Watson, HDD Mud Systems.