Presentation on theme: "Introduction Recently the industry has had to moved from having traditional derrick mounted drill string compensators to utilizing active drawworks. This."— Presentation transcript:
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.
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. Introduction Cont’d…
Stingray750/500 ton MoComp Coil Tubing Lift Frame Specifications Maximum Lift (locked position):750 tons Maximum Compensating Load:500 tons Compensating Stroke:20 ft Blind End Maximum Working Pressure:2,400 psi Typical Operating Pressure:2,230 psi Rod End Maximum Working Pressure:95 psi Typical Operating Pressure:40 psi Number of 1,000 gal APVs:2 for operations Design Specifications: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.
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. Operational Philosophy Cont’d…
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.
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
The unit has the ability to either attach to the riser by the traditional means of bails or the test tree can be installed in- place 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. Design Advantages Cont’d…
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. Additional Key Features