Casing Storage, Handling and Transport

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This article describes the recommended guidelines for casing storage, handling and transport that need to be taken account in the design phase of the casing.

1 Storage

The design of pipe racks is dependent on local conditions. i.e.: required load bearing capacity and degree of permanency.

Racks can be made with pipe supports (stringers) set on concrete, or on large wooden bases provided with recesses to accommodate the stringers. They should be spaced to support the longest and the shortest joint in stock. This requires a spacing of around 6.5 ft (2 m) which allows 20 ft (6.1 m) joints to be stored on two stringers and 40 ft (12.2 m) joints on four stringers. For temporary stringers timber is often used. The dimensions will depend on the soil bearing capacities but 10´10 in (25 cm´25 cm) is generally sufficient.

Casing should be stacked with separators between layers. Tubulars should never be nested. Separators in successive layers should be vertically in line to avoid bending moments on the pipes. As separators, timber of around 5" (7.5 cm) can be used with a wedge at both ends. Fresh timber should be avoided as the moisture is squeezed out of the tubulars and can cause local corrosion and pitting of the casing in contact with the separators.

For storing for long periods in wet climates, the joints should be separated on the racks to allow for drainage. This is achieved by use of a plastic wedge or T-piece. Also, the rack should be tilted towards the pin-end to enhance self drainage (open-ended thread protectors should be used).

In determining space requirements for casing, the following points are to be considered:

  • height of stack;
  • diameter of casing (including coupling);
  • range of casing and total footage;
  • size of pipe racks;
  • working space.

In accordance with API Recommended Practice RP 5C1 (Section 3), the height of the stack should not exceed 10 ft (3 m) including the pipe rack. If the height of the rack above the ground is taken to be 20 in (0.5 m) then the maximum height of casing on the rack should not exceed 8 ft (2.5 m). In case of temporary storage where casing is stacked on the ground, it is even more advisable for safety purposes, to limit the height of the stack.

The length of each pipe rack should be sufficient to accommodate Range 3 tubulars. The width of the rack can vary, but for the limited quantity of each type of casing held in stock, the width should not be more than 40 ft (12 m) nor less than 20 ft (6 m).

A lane not less than 20 ft (6 m) wide should be allowed on either side of the racks for transport and handling operations, with a space of approximately 5 ft (1.5 m) between racks.

For small quantities, particularly small diameter casing/tubing it is impractical to build a stack to the maximum height. Here the stacking height must be reduced and the stack width increased in proportion. (A rough guide is that the height of tubulars in a stack should not exceed the base width). Therefore when planning pipe racks, allowance must be made for small quantities which require more space than the table indicates.

2 Preservation

The corrosivity of the atmosphere depends on the degree of contamination which can vary considerably even from a few hundred metres apart. Significant corrosion occurs if the air is polluted. The usual contaminants are the result of domestic and industrial combustion and when close to the sea, wind borne salt. The presence of moisture alone, even prolonged rain, will not cause significant corrosion of steel. Sand and dirt collecting on steel can increase corrosion by holding contaminants on the surface.

Cost should be taken into account when choosing a preservative. Some types are expensive and can only be justified by the high cost or critical nature of the material to be protected. The most expensive method of preservation is not necesarily the most suitable.

There are publications on methods of preservation, and systems change from time to time as new products become available or new demands occur.

2.1 Pipe body

Unless otherwise requested at the time of purchase, casing is ordered in accordance with API Specification 5CT and therefore the pipe body will have a mill coating. The purpose of the mill coating is to protect the casing from rusting in transit. Since API is not specific in this respect, the type and quality of these coatings vary as does the length of time the coatings gives protection in storage. If casing is to remain in storage for a long period, the mill coating could be supplemented or the casing completely cleaned from the mill coat and re-coated.

The internal and external surfaces of production tubulars may be grit blasted and then re-coated prior to storage. This cleaning minimises any loose material that might cause problems during completion, the operation or workover of the well.

There is evidence to suggest that mill coatings and other applied coatings affect the signals from acoustic cement evaluation devices. The log will indicate weak or even no cement bond when this is not in fact the case. There is also some evidence that the presence of an external coating might adversely affect the actual hydraulic bond. As a result, for casings where it is important to be able to detect the quality of the cement bond accurately, all mill coating should be removed by grit blasting but no coating should then be applied unless necessary for corrosion purposes. Where coatings are applied, this fact should be recorded on the headers of cement bond logs.

Whenever grit blasting is carried out, extreme care should be taken to ensure that the proper thread protectors are fitted to prevent damage to the threaded connections during the blasting operation.

Where internal surface coating is required, the use of coatings which give a thick film should be avoided because of potential problems running wireline tools.

Particular care is required to prevent the corrosion of notch-sensitive casing such as C95 and P110. If storage for more than three months is foreseen, unless adequately coated when delivered, casing of these grades should be cleaned and coated internally and externally.

As already mentioned thorough cleaning is essential for effective conservation and all scale, rust, dirt, oil and grease should be removed before any coating is applied. If any deposits on or in the tubulars have contained salts, such as from sea water spray during shipment, the surfaces should be washed with fresh water and then dried.

Recommended storage coatings for internal and external casing surfaces are given below.

  • Internal: Blacksmith CP 914, Agma 273
  • External: Agma 865, Agma 5601, Shell Ensis HP

Several external coatings have been identified as acceptable only provided that the tubulars are covered (with a tarpaulin). These are:

  • Malacote 400
  • Oil Centre Research Inc. 911
  • Shell Ensis MD

2.2 Threaded connections

Whilst in storage, thread protectors should be removed from time to time to check that the thread compound is in good condition. If in doubt, washing, brushing and re-application of the compound should be carried out.

Example of thread storage compound:

  • Shell Rhodina Grease 2
  • Geveko Mercasol 630
  • Jet Marine Imperator 1078
  • Kendex OCTG corrosion inhibitor
  • TSC thread storage compound
  • Cortec VC1-369
  • Rust Vetco heavy
  • RD5

It should be noted that a storage compound is not to be used as a running compound and that a running compound is not to be used as a storage compound.

There are hybrid compounds available which can be used for both storage and running. Example of hybrid compound products are:

  • Kendex Enviro Seal
  • Mercasol 633 SR Multimake White
  • Cats Paw black 712 S
  • Bestolife copperfree PTC
  • Bestolife 2000 5% copper
  • Shell Française SF 3646

Most running compounds contain chemicals that are harmful to the environment such as lead, copper, zinc, arsenic, antimony and molybdenum disulphide.

3 Handling in the pipeyard

4 Transportation

4.1 Road

Always ensure that tubular goods are adequately secured, irrespective of how short the journey may be.

Forces are generated on the load when a vehicle brakes, accelerates, changes direction or crosses road undulations. These forces are frequently greater than the frictional restraint between load and platform which means that all loads must be secured by a restraining device. The device must be sufficient to withstand a force equal to not less than the total weight of the load forward and half of the weight of the load backwards and sideways.

The design and construction of anchorage points through which the securing device can be attached must allow twice the specified capacity acting in any direction. Anchorage points must be firmly attached to the chassis or to a metal cross member or outrigger and where practical with doubling plates.

Prior to moving off with the loaded vehicle all tensioning devices should be checked by the driver and after a few miles the lashings should again be checked, thereafter at regular intervals during the journey.

4.2 Water

The stowage and transportation of casing by marine craft will be the sole responsibility of the Master. The safe handling of tubulars to/from the vessel will follow closely the guidelines indicated above. It is good operating practice to ensure that casing, where possible, be bundled in preparation for handling offshore. When bundled the slings are doubled wrapped and secured with a bulldog grip and a plastic tie-wrap. The bulldog stops the loops of the sling round the bundle from becoming loose during transit, the tie-wrap is an extra precaution to stop the bulldog from slipping. The reason why the joints are bundled in this way is in case there is a snatch-lift, i.e. while the load is being unloaded from the vessel, the vessel heaves and dips due to wave action leaving the load to be supported by the crane suddenly, the load will be secure and joints will not become loose and fall.

5 Identification

Electronic tagging of casing will improve pipe identification and inventory control. This involves attaching to the casing a small passive electronic chip which has a unique identity number. Against that number the user can store any information he chooses, e.g. pipe dimensions, material grade, date of manufacture, thread inspection records.

6 Low-temperature environments

Low ambient temperatures substantially reduce the size of the flaw necessary to cause failure. The following procedures, while being applicable in all circumstances, are particularly important for low temperature environments:

  • Do not drop, bend, or scratch the pipe. If lengths of pipe have to be forcibly separated due to ice accumulation, take care not to scar the metal surface.
  • Thread protectors should be removed without hammering or shock loading.
  • Extra precautions should be taken when stabbing the pipe, since low temperatures reduce the impact resistance of the metal.
  • Box and pin should be of equal temperature to ensure proper make-up. Use Arctic grade thread lubricant.

Comments  

#1 AndyProud 2014-04-23 10:19
In this article under section 2 Preservation, towards the end of section 2.1 Pipe Body, recommended storage coatings for internal and external casing surfaces are listed. The product references for the AGMA coatings are incorrect and should be:-

The Agma product for the internal surface should be Agma Synergen 718
The Agma product for the external surface should be Agma Synergen 501

Andy Proud
Business Manager
AGMA Limited
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