One of the recommendations of the UKOOA was that all UK operators should ensure that all installations contracted to or operated by them have oil mud containment systems in place. The guidelines produced contained an idealised list of mechanical containment methods which should be considered when designing new rigs and installations.
The report recognized that it may not be possible to retrofit all items on existing installations, however where certain items are missing there should be containment procedural methods in place to cover the lack of mechanical containment systems.
Rig Floor
Mud Saver Valve
- A mud saver valve suitable for OBM shall be provided. This was envisaged redundant if a top drive system with a remote operated Kelly Cock was installed.
Mud Buckets
- A range of mud bucket seals should be available for all tubular sizes utilised on the drilling unit. The mud bucket drain lines should have a minimum ID of 6" and should be tied back to the flowline.
Mousehole / Rathole Drains
- The mousehole and rathole should be fitted with drains which can then be piped to a central collection tank or be fitted with valves to be periodically emptied to a suitable container.
Pipe Wipers
- Pipe wipers should be used when tripping out of the hole.
Rig Floor Drainage System
- The rig floor should have a drainage system installed. All drains should be able to be pumped back into the pits or to a storage facility for treatment ashore. After settling out of OBM and wash water in the collection tank it should be possible to vacuum of OBM using a suitable Mudvac.
- The collection tank should be fitted with an alarmed level indicator. Drip trays should be fitted under the rigfloor to collect the remaining OBM for disposal to the collection tank or to trip tank.
Flowline
- Any open parts of the flowline should have splash lids fitted which can be sealed during normal drilling operations but be available for opening, should jetting of the flowline become necessary due to plugging.
Shale Shaker House
Shale Shakers
- Modern generation linear motion shakers should be installed to enable use of fine screens in situations of high ROP and flowrate. Use of fine screens will limit the necessity to use mud cleaners. The use of primary solids control equipment only has proven to reduce greatly the consumption of OBM.
- Sufficient shale shakers should be supplied for the quantity of cuttings anticipated. The header box should be carefully designed to ensure even flow over all shakers. Each shaker unit should be fitted with a running light. This light should be mounted in view of the driller.
Solids Control Tanks
- All solids control tanks should have drainage lines recessed into the bottom of tank to ensure total drainage when backloading OBM. If pits are synthetic mudall a mud vacuum unit could be used.
- The sand trap should have a pump installed to allow recirculation of its contents over the shakers. All centrifugal pumps should have bunds surrounding them and all pump glands should be fitted with mechanical or pressurised seals. All bunds should be sealed and emptied via a mud vacuum unit or may be unsealed and have a drain fitted to the central collection tank.
- All dump valves should have double valve isolation. All valves should be of either screw of knife type.
- All floor drains should be sealed or piped to the central collection tank.
Pit Room
Mud Pits
- All mud pits should have suction lines recessed into the bottom of the tank. All pits should have accurate volume markers and pit level indicators. Pits should be fitted with an agitation system to prevent solids settling. All mud tank dump lines should have double isolation and be routed through a master dump valve. All valves should be lockable.
Floor Drains
- All drains should either be sealed or drain to the central collection tank.
Trip Tank
Trip Tank Pump
- A bund should surround the pump, gland packings should be of the mechanical or pressurised variety.
Trip Tank Overflow Line
- An overflow line should be fitted to the trip tank.
Trip Tank Dump Line
- The dump line valve should be lockable and be either of the gate or knife type.
Sack Mixing Area
- All hoppers should be surrounded by a bund and any drainage sealed or piped to the central collection tank.
Riser Slip Joint
- The slip joint packer should have a low pressure alarm system fitted and should have a reserve pressure supply.
Base Oil Storage / Transfer System
- all base oil movements should be metered whilst loading / backloading.
- All loading hoses should be routinely maintained and monitored to ensure they are fit for the purpose.
- procedures are in place for draining of base oil/OBM transfer hoses after backloading or uploading these fluids from/to the rig.