Can any one advice on Standards and Policies for requirement of 36" Diverter for Jack up Rig.
Can anyone share the experience using 36" diverter.
If originally 36" diverter is not the part of rig equipment. What is the availability of 36" Diverter for a shallow Jack up rig drilling Operation in Middle east area.
What are the mitigations if we could avoid using the same. I mean, drilling a pilot hole etc.
If the Pilot hole is drilled and confirmed no shallow gas!! Is it require to drill the 36" hole with 36" Diverter ON.
36" hole section is planned to drilled to @ 2400ft.
Appreciate your comments and help
Surface gas can represent a real hazard and with a significant release of shallow gas in the sedimentary layer could adversely affect the spud can stability of the installation (worst case). Please refer to API RP 64, Section 6.1.
The overall danger here drilling into shallow gas with a 36in. hole opener is the potentially large volumes of gas at pressure. The vent lines need to be suitably sized such that no well pressure will build within your containment boundary - once the diverter has been shut in. Remember the diverter system is a low pressure system and is never considered to be a positive shut-in device for the well in respect of well control. Diverters are what they name suggests: a means of diverting well fluids/gas to a safe area.
The nominal diameter of your vent lines has a direct impact on the pressure drop due to friction losses - related to pressure and velocity of the well fluids. (Beggs and Brill Correlation). Try and assimilate the possible pressure build-ups in the system if you drill into shallow gas versus generated back pressure in the vent lines with the diverter shut-in. I cannot stress sufficiently the fact that this system is a LOW PRESSURE SYSTEM.
Your current policy to drill a pilot hole is a prudent step in the drilling of the surface conductor section to 2400 feet BML. Again, whilst drilling the pilot, consider the release of significant volumes of shallow gas and the rig's ability to handle and divert this safely.
To be 100 % safe, you could consider setting a cement plug over the bottom unlogged section before opening up to 36". Circulating bottoms up and check for gas from the bottom of the hole is often good enough for most.