Introduction
Recently the industry has had to moved from having traditional
derrick mounted drill string compensators to utilizing active
drawworks. This stems from the need to increase both the
Variable Deck Load and the stability of deep water drilling rigs.
Unfortunately, drill line compensation units present drawbacks
when used for Drill Stem Testing type operations as their failure
mode can create scenarios that either lock up the compensating
ability or instruct the drawworks to lift the string that is in
support or as per other failure modes.
Introduction Cont’d…
Due to operational requirements pertaining to movement of the
travelling/crown blocks, which in the case of DST work can occur
during critical operations, a drill line fatigue limit may initiate a shut
down of operations until the drill line can be slipped.
The solution for such a scenario is to utilize a Coil Tubing Lift Frame
with Motion Compensation capabilities. The following is a
culmination from years of experience installing, interfacing,
designing, and troubleshooting motion compensating systems in
both drilling and coil tubing applications.
Stingray Scana MoComp CTLF
• Estimated Weights
MCCTLF Unit:
500/350 -124,000 lbs [56,245 kg] Carbon steel
500/350 -100,000 lbs [45,359 kg] Alloy steel
750/500 - 186,000 lbs [84,368 kg] Carbon steel
750/500 - 125,000 lbs [56,700 kg] Alloy steel
Stroke:
20 ft (All systems)
Power Vessel Storage Rack:
350 MC - 35,000 lbs Est. [15,875 kg]
500 MC – 52,500 lbs Est. [23,814 kg]
Associated Hoses, Manifolds, etc.:
5,000 lbs [2,300 kg]
Stingray750/500 ton MoComp Coil Tubing
Lift Frame Specifications
•
•
•
•
Maximum Lift (locked position):
Maximum Compensating Load:
Compensating Stroke:
Blind End
Maximum Working Pressure:
Typical Operating Pressure:
• Rod End
Maximum Working Pressure:
Typical Operating Pressure:
• Number of 1,000 gal APVs:
• Design Specifications:
750 tons
500 tons
20 ft
2,400 psi
2,230 psi
95 psi
40 psi
2 for operations
DNV – OS – E101
in accordance with API 8C
Operational Philosophy
Manufactures of rig motion compensation systems have
advised their customers that active drawworks is not suitable
for DST work and should not be used for this application; and
that some other form of compensation be used. Because of
this Stingray has developed a passive system using our years
of experience and years of field proven reliability with existing
passive systems.
Under normal circumstances, we could expect to use a
simple rod end down design for this application. But the
increased severity of the design and its application creates a
new set of considerations for the deep water Motion
Compensating Coil Tubing Lift Frame. For this reason the
Stingray MCCTLF has been designed using the compensating
cylinders as compression members. By doing this the
advantages are great. This is discussed in the following
section.
Operational Philosophy Cont’d…
The handling logistics are also critical. Transporting an
item of this size, lifting it onto the rig, inserting it into the
derrick, and stabilizing it are strong considerations in this design.
All areas of the Stingray CTLF have been analyzed with regard to
minimizing its weight.
An additional consideration is the coordination of the
existing equipment on the rig. It may be possible to use some of
the existing motion compensation bottles and air compressors to
resolve any logistical requirements. Because of the specialization
of this type of equipment, each rig application will require a
moderate to extensive review. This is why the weight and
handling of the unit is so critical.
MCCTLF Stability – Cylinder Guidance
• The MCCTLF design has taken into consideration the potential
for axial and lateral loads.
• The SOS MCCTLF system utilizes four (4) cylinders which can
better balance the loading.
• The cylinder rods are fully protected by the Sub Frame’s
structure.
• The Sub Frame has stainless steel sliding surfaces which
interface with the Winch Frame’s (upper section) nylatron
sliding pads (see drawing SOS-10-123-093).
• The Extension Legs (middle section) have stainless steel
sliding surfaces which interface with the Compensation
Cylinder’s nylatron sliding pads (see drawing SOS-10-123-093).
MCCTLF Stability – Cylinder Guidance
Cont’d…
• Having completed the first version of the MCCTLF, SOS has
already reviewed and incorporated additional sliding pads
into the design for increased guidance and stability.
• The rod clevises have spherical bearing assemblies to
accommodate misalignments and avoid transmission of
torque into the cylinder rods.
MCCTLF Guides
Design Advantages
The Stingray MoComp CTLF operates by applying high pressure
air to the blind side of the compensation cylinders rather than
the rod side. The positive effects of this application outweigh any
negative effects in the following manner:
• The weight of the SOS CTLF is much less than competitive
units.
• The actual operation of the SOS CTLF is very similar to the
older inline drill string compensator. This makes for very
simple controls and maintenance.
• By using trunion mounted cylinders with high strength steel it
is possible to create the same or better balance of the load.
This approach also allows the framework to function as
protection for the cylinder rods.
Design Advantages Cont’d…
• The unit has the ability to either attach to the riser by the
traditional means of bails or the test tree can be installed inplace utilizing a special bushing. The latter greatly reduces the
height of the operational string.
• By utilizing the blind end for the compensation force, the
system becomes much more efficient as there are no losses
due to rod area that a tension type system would have.
• By employing the cylinder rod in compression, a larger
diameter is required. However, this benefits the system by
reducing the volume required for the rod end Air/Oil
reservoirs.
Design Advantages Cont’d…
• Speed control is easily achieved by having the low pressure oil
on the rod side of the cylinder; enabling the use of industry
standard and field-proven speed control devices for the
dampening and control of the barrel and rod travel.
• Applications using a rod end vent to atmosphere have
contamination and corrosion problems. The SOS CTLF avoids
this through the implementation of Air/Oil reservoirs.
• There is only Air on the high pressure blind side of the SOS
CTLF. This makes the unit much more responsive as air flows
much easier than oil. In addition, it removes the requirement
for large, heavy accumulators and overly complicated speed
control devices.
Additional Key Features
• The bail pins are hydraulically operated; making it safer and
easier to use.
• There is a hydraulically operated gate system on the lower
frame. This allows for the test tree and riser to be mounted
directly in the frame. This removes the requirement for bails
and thus reducing the overall length of the system in the
derrick.
• There is an optional hydraulically operated “jib arm” with a
light duty winch for the handling of small equipment.
• Critical cylinders have built in mechanical lock in the closed
position the do not rely on a hydraulic lock.
Pneumatic System Schematic
Hydraulic System Schematic
Control Panel Schematic
Speed Control Valve
General Arrangement
MCCTLF 500-350-20
MCCTLF 500-350-20 MCCTLF
MCCTLF 500-35-20MCCTLF