Up front disclosure, we at Oil States supply the larger sizes of the range you are looking at (18-5/8" - 30" or larger).
Taking into account the key points made above WRT Design first, then enquiry later, it may be useful to know that there can be quite a bit of flexibility in wall thicknesses and casing strengths if you have drift vs pressure factors to balance and lead times for special runs presently are not over the top. So it can be useful to have some contact up front with suppliers before settling on optimum design. What you see on the on-line sizes is often only the basic stuff.
Hello Gaz, please find below information from a different approach, an alternative for steel casing.
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Please drop me a line if you need more information.
0. In the past, the Composite Catalog of Oilfield Equipment & Services was the vehicle to find most of the Oilfield Suppliers. OCTG are available in America, Europe & Far East, but each can play on a different league. That is the easy bit. For the subsequent steps here are two generic and one specific guidelines
A. Drilling equipment purchasing
1. My standard recommendation is to pre-quality drilling related designs and manufacturer before asking for commercial quotations. This to encourage more innovative designs to come forward and to discourage low quality and/or copy-cat designs.
In the pre-qualification stage a quality phase, scaled drawings, stress calculations and testing data are a must. After approval the vendors are then invited to submit a comprehensive commercial quote covering specifically the agreed design and quality plan.
2. We refer now to an article appeared in "Process Engineering" March 1985, entitled "Going for open tender on plant equipment" by J. Fawbert where the following steps, similar to ours, are detailed:
- Tender evaluation involving tender documentation, rules for pre-qualification, preliminary evaluation and short listing.
- Final tender involving site visits to short listed bidders, standardization of bidders' offers and selection.
3. Tender evaluation stages
Tender documentation - Structural design, mechanical solutions, life expectancy, quality plan and environment to be included.
. Pre-qualification rules ask for previous experience, technical innovations and service support.
. Preliminary evaluation should audit the design proper against existing equipment failures. These are normally attributed to misuse (35%), mis-machining (15%) and last but not least, incorrect design (27%). However, it must be borne in mind that most of the operational abuse, improper maintenance, lack of quality in manufacturing stem from a sub-optimum design.
Feed back and cooperation at all levels between User and Vendor is the only way to improve this situation.
For instances, a simple 'environmental test' of a prototype can be an eye opener vis-a-vis engineering appraisal of designs.
. Short listing should look at mechanical aspects, structural design, weight and room requirements, ease of machining, inspection and service.
4. Tender proper
. Site visits to short listed bidders - This is mainly to assess the level of cooperation among the design office, shop floor and service end of the facilities, e.g. for environmental testing.
Potential design short-comings and eventual design improvements can be discussed.
(It is worthwhile the looking at the "Rejects" and "Spare part" market to assess reliability. The delivery records are also a useful indication).
. Standardization of bidders offers - where the original specification are refined and made uniform.
. Selection - The comparison now should weigh technical evaluation, delivery and cost in that order.
5. It is worth noting that the article which parallels our views relates to coal industry.
B. Technical acceptability of new products/vendors
Different operators continuously query on the accept-ability of new vendors or new design and for application in their operation.
Our philosophy is to support new ideas provided they are well engineered and remain financially attractive.
Prospective vendor should however provide the following:
1. Design parameters and scaled drawings
2. Analytical guidelines - (e.g. Finite Element Analysis)
3. Fatigue resistance.
4. Rating procedures
5. Prototype test results, third party witnessed
6. Quality plans.
When the assessments are favorable a pilot test could be conducted provided the cost competitiveness criteria are also met.
C. Technical suggestions for ordering API* Tubular Goods
To complement API Spec 5CT suggestions for ordering casing or tubing, a Technical recommendation which reflects worldwide experience - recognizing that tubular goods are a 'specialty' often ordered under API Spec 5 CT 'commodity' guidelines .
Find below these additional guidelines.
The evaluation of the commercial implications should be carried out in cooperation with the relevant mills.
1. OD tolerances: rather than the API combination OD-0.5%, OD+1%, it is recommended to stick to the following combination OD- 0.5%, OD+0.75%.
This reduced upper limit should be imposed, not only for roundness but mainly to ensure interchange-ability with ancillary equipment.
The OD should be checked with a 'go/no-go' gauge like the bit caliper and not with a 'PI' tape which allows oval pipe.
(THE 'pi' tape measures the circumference of a circle but is calibrated in terms of its diameter). The background to this is that the API Spec 5A - forerunner of API Spec 5CT - referred to OD tolerances as nominal.
Length and leak resistance. Exxon's proposals to API via E+P Forum should be adhered to. API Task Group/92 suggest making it a Supplementary Requirement (item 2221).
3. Range length: API Range 3 length varies from 34' to 48'. If a mean length of 45' is specified it speeds up running casing, as it minimizes connections - potential leak paths - and allows better dilution of thread costs, less handling and the possibility of doubles on mast - attractive in some work-overs: tubing stands - and when casing has to be round tripped. Operators could take advantage of large pipe rack areas to prepare doubles on the rack to ran as 'false singles' through the 'V' door, as USA did with API tubing (4.5'' and smaller) that does not cover range 3. This is another reason to deviate from API specifications.
4. Toughness requirements: Bearing in mind perforation requirements on tubular goods and wedging of slips - of packers, liner hangers, wellheads, cement retainers and bridge plugs - a minimum impact strength for any of the full size transverse samples shall be of 15 ft-lbs Charpy energy, not only for Group 3 (formerly 5AX, extra Yield strength P 110) and part of Group 1 (formerly 5A: J 55 and K 55 ) but also for the remainder of Group 1 Grade N 80 and Group 2 (formerly 5AC, restricted chemistry) - C 75, L80, C 90 and T 95.
API Spec 5CT makes it mandatory to Group 4(formerly 5AQ) - Q 125, only. (API committee on standardization of tubular goods Task Group ITEM NR. 2213)
5. Pup joints: Long deliveries and costly pup joints can be expected if bar stock is used to machine them.
Mills should be encouraged to supply pup joints - even if plain ended - making not only better use of rejects (saving the good sections of the faulty joint) but also providing identical raw material for the pup joints.(Jointers can be used to make the required length for threading machines).
Incidentally, threads on ancillary tools (casing hangers, stage collars, float equipment, wire-line nipples, Side Pocket Mandrels, Blast joints and flow couplings) must be cut either by integrated mill or by the recognised licensee that cut the threads on the pup joints.
6. Alternate drift: API Spec 5CT table 6.0 refers. World wide the following combinations are common: 13 3/8'' 72 LBS/ft, 9 5/8'' 53.5 LBS/ft and 7'' 32 LBS/ft. Alternate drift allows the use of more common bits - 12 1/4'', 8.5'' AND 6'' - improves flow-by area around close-fit ancillary equipment - liner hangers, packers, etc - and enhances roundness and leak resistance.
In this vein, longer drift mandrels are required. API recommend 6''-12'' drift length for casing, however, as some of the API casing is used as tubing - 7'', 5'' very common production strings - drift MUST be longer. THE EQUIVALENT TO API TUBING DRIFT MANDREL 42'' LONG IS suggested.
7. Matched Strength Connections: API couplings are either regular - nominal pipe OD+1''- or special clearance. The above dimensions and price should include the required qualification test. The then internationally accepted qualification standard is API RP 5C5, which establishes 4 levels of acceptance: IV (3 specimens and differential working pressure below 4000 psi), III (12 SP, 4/8 KSI),II 24SP, 8/12 KSI) AND I (27 SP, MORE TH.12KSI). We must optimize the API Qualification test procedures, streamlining time and expense associated with qualification tests. Listing of qualified connections are available from reputable Vendors.
Qualification tests for steam injection are even more severe and more revealing. There, a lot can be learned from torture testing connections.
9. Chemical composition: It is essential to get from the manufacturer, the complete chemistry - aim and actual - to assess if modern steel making technology is being used.
Levels of Sulphur, Phosphorous, Manganese and Carbon could be revised downwards for steel cleanliness, in line with API TG item Nbr 1035.
For instances, E+P Forum suggested L80 type 1 values to be respectively 93%, 84%, 67% and 50%of the values of API spec 5CT Table 3.1.
This is available at no extra cost from all reputable mills
10. Heat Treatment: The option which will be elected by the mill should be asked for in the pre-qualification phase and should be spelled out in the quotation, by the manufacturer and in the purchase order, by the purchaser.
For instances, N80 can be either Full Length Normalized (N), Normalized & Tempered (N+T) or quenched & tempered (Q+T). For the latter chemistry must be restricted - both C and Mn levels to be reduced - to allow crack free quenching.
11. Line pipe used as Casing: The steel making and process of manufacturing should follow API Spec 5L but acceptance criteria - geometry mainly - should be in line with API Spec 5 CT. This is seldom the case. See case histories: 13 3/8'', 16'',18 5/8'', 20'' and 30'' where pipe ovality and/or pipe maximum OD, created difficulties with not only threading but mainly ancillary equipment - hoisting, centralisers/stop collars and wellhead slips.
12. Thread Protectors: Preference for 'drift-able thread protectors' should be spelled out. Premium Connections require premium protectors. Not all qualified Research acceptance criteria as published in 1988 SPE 17209. Furthermore, pipe preservation techniques require grit blasting, following accepted Swedish standards - SA 2.5 as defined in S.I.S. 05 5900:1967. (See equivalent BS 4232/1967). This operation may place grit in the thread and/or seal area which can create leaks and galling, if sub-optimum protectors are used.
In this vein, it is useful to remember that split-able handling protectors were not designed for premium connections and can damage the seal area.
Recommended thread compounds are updated by proceedings of JIP DEA(E) - 1992 on the subject of environmentally acceptable products.
14. Pipe roundness: To achieve quality thread cutting, pipe must BE ROUND AND STRAIGHT. ITEM NR 2248 OF API TG/92.
END USERS ARE encouraged to check roundness using either Go/No-go gauges or Eddy current. Thread enhancement can be achieved 'true´ing up' the pipe near both ends and/or cutting the threads using an ID chucked lathe - done sometimes, on request.
The latter creates a string which is a true 'gun barrel' and enhances metal seals.
Eddy current is recommended to measure pipe ovality prior to and after threading. Long pipe and heavy wall create mass unbalance which creates thread chatter, clover leaf and/or egg shaped threads.
15. Thread Make-up: Presently, proper make up of
premium connections is difficult to
assess as it relies on indirect measurement: torque, function
of friction. This is the case, even using scribe-lines on
mill-end, dope applicators and updated torque turn tongs -
including 'soft touch' and 'low stress' dies - . Ultrasonic techniques are available, to
assess the correct pre-load of the seal interface.