The length and composition of sub-assemblies is usually dictated by the space and handling equipment considerations. They will ideally be made up and tested (both functionally and hydraulically) in a suitable base workshop.

On site make-up should only be performed if the correct make-up equipment is available to ensure correct make-up torque and no damage to the tubulars. The use of tongs/pipe wrenches and cheater bars is not recommended for obvious reasons.

1. sub-assembly preparation

The sub-assemblies should normally be drifted, functionally checked, operated and pressure tested once assembled (made-up) and prepared for shipment/transport.

Function testing must be made on all items of equipment which have moving parts, such as sliding sleeves and tubing retrievable safety valves. In some cases it may be more practicable to function test particular equipment once assembled with the other items.

2 Sub assembly make-up

As for the make-up of all tubulars, the connections need to be cleaned, dried and inspected for damage. The following points should be considered when making up sub-assemblies:

• ·Avoid sub-assemblies which will necessitate making up the next joint at an excessive height above the slips, e.g. side pocket mandrels (SPMs) should be made up as a sub-assembly on the pin end of a tubing joint, with a pup joint below the SPM or preferably between two pup joints.
• ·Avoid excessively long assemblies for handling reasons.
• ·Blast joints should be made up in lengths of 40 ft with, where applicable, a wing guide sub (centraliser) on top. The wing guide sub on top not only centralises the blast joints in the casing when installed, but also eliminates the necessity for installing a drill collar clamp during handling in the rotary table.
• ·Completion accessory outside diameters are often different from that of the tubing, so sub-assembly composition should be chosen to eliminate the necessity to frequently change tong dies.
• ·Power tongs and back ups should be positioned either side of the connection to be made up. Do not torque up across accessories.
• ·Packers and other heavy accessories should be made up between pup joints. The sub-assemblies centre of gravity should be low otherwise it can be difficult to control during make-up of the connection.