Oil Casing Length Ranges — R1, R2 and R3 Explained

API 5CT 11th edition Table C.22 sets casing Range 1 at 4.88–7.62 m (16–25 ft), Range 2 at 7.62–10.36 m (25–34 ft) and Range 3 at 10.36–14.63 m (34–48 ft), and it sets no minimum average length inside any of them. That last part is where purchase orders go wrong. I'm Hazel Wang at ZC Steel Pipe, and "Range 3" on its own is a length line I would rather not see on a casing PO.

Writing it that way is not wrong: longer joints mean fewer connections, less rig time and fewer leak paths. But "Range 3" alone leaves the average, the short end of the band and the pup joints undefined. We supply API 5CT casing and tubing in R1, R2 and R3 for grades from H40 through Q125, and this guide covers what the standard controls, what it leaves to your PO, and how to write the length line so the tally that arrives matches the well you planned.

API 5CT Length Range Definitions

API 5CT 11th edition Table C.22 defines three casing length ranges: R1 is 4.88–7.62 m (16–25 ft), R2 is 7.62–10.36 m (25–34 ft) and R3 is 10.36–14.63 m (34–48 ft), each a total range length, inclusive. Clause 7.6 puts it plainly: "Unless otherwise agreed upon between the purchaser and the manufacturer, casing, tubing, and pup joints shall be furnished in lengths conforming to Table C.22 or Table E.22."

Table: API 5CT casing (PE/T and C/SF) length ranges and maximum permissible variation, Table C.22 / E.22

Notice what is missing: there is no minimum average length in Table C.22. Some older guides — including an earlier version of this page — quote per-range minimum averages as if API 5CT required them; the 11th edition does not. Inside a range, the only control the standard gives you is the permissible variation, and note a limits even that: "Length variation applies to rail car shipment to the point of use and does not apply to order items of less than 18,144 kg of pipe" (40,000 lb in Table E.22). If you want an average — say R3 with a minimum average of 12.50 m — write it on the purchase order as an agreed term. The standard will not supply one for you.

Tubing Length Ranges

API 5CT Table C.22 gives tubing — and casing used as tubing — its own Range 1, 2 and 3, with a 0.61 m (2 ft) maximum permissible variation in every range. Integral tubing connections (IJ/PE and IJ/SF) get a third row with longer upper limits. The standard calls them Range 1, 2 and 3 for tubing too; "T1/T2/T3" is shorthand you will see on some RFQs, not API wording.

Table: API 5CT tubing and integral-tubing-connection length ranges, Table C.22 / E.22

Two things to read from this. First, the tubing bands are narrow — 1.22 m (4 ft) wide against 4.27 m (14 ft) for casing R3 — so a tubing tally is far more predictable than a casing tally. Second, if you order casing sizes for tubing service, they fall under the tubing row, not the casing row, and the ranges change accordingly.

Pup joints have their own row in the same table: standard lengths of 0.61, 0.91, 1.22, 1.83, 2.44, 3.05 and 3.66 m (2, 3, 4, 6, 8, 10 and 12 ft), tolerance ±0.076 m (±3 in). Note b to Table C.22 applies to the range columns and the pup row alike: "Lengths other than those listed may be furnished by agreement between the purchaser and the manufacturer."

For the complete grade ladder with tensile, hardness, and chemistry limits, see the API 5CT specification tables →

To match a grade to your well conditions, use the Pipe Grade Selector →. Length range is independent of size — to pin down OD, wall, and nominal weight for the string, use the casing size lookup →. The full casing sizes, dimensions and weight tables give OD, wall, ID and weight by size.

Why Buyers Choose R3 for the Main String

Range 3 is what most casing buyers put on the PO — most of the casing orders on our own project list shipped R3 — and the reasons are arithmetic, not tradition.

Fewer connections — every connection in a casing string is a potential leak path and a point of mechanical discontinuity. Taking an assumed R1 average of 6.1 m (20 ft) against an assumed R3 average of 12.2 m (40 ft), a 2,500 m string needs 2,500 ÷ 6.1 = 410 joints on R1 and 2,500 ÷ 12.2 = 205 joints on R3. Half the make-ups. Those averages are assumptions inside the Table C.22 bands — API 5CT sets none — and your real figure comes from the mill's tally. The R2-versus-R3 version of this sum, with costs, is worked through in full further down.

Less rig time — each connection means picking up a joint, stabbing, making up the thread and torqueing. Halving the make-ups halves that time; what the hours are worth depends on your rig rate, which the worked example below sets out as a labelled assumption. For how make-up itself should be run, see the premium connection make-up torque and running guide.

Lower connection cost — fewer joints means fewer threaded ends and couplings. For premium connections in particular, that difference adds up across a long string.

When R1 or R2 Are Appropriate

Shorter ranges, or R3 with agreed limits, have legitimate uses:

Pup joints — short sections of casing used to adjust string length or span a specific interval. Pup joints are not ordered as R1 — Table C.22 gives them their own lengths, 0.61 to 3.66 m (2 to 12 ft), tolerance ±0.076 m (±3 in); see the API 5CT pup joint specifications and sizes guide for standard increments and the depth-control math.

Casing patches — when repairing a damaged section of an existing casing string, the patch length must be sized to the damaged interval. R1 or custom-specified lengths are used.

Rig handling constraints — if a land rig, workover unit or modular rig cannot pick up a single joint as long as 14.63 m (48 ft), R3 as written is the wrong line. Get the rig's pipe-handling limit before the PO, not after the pipe lands.

Liner strings — some liner hanger and running-tool designs come with their own joint-length guidance. If yours does, take the number from the liner supplier's running procedure and write it on the PO as a maximum individual length; Table C.22 will not supply it.

Specific well sections — interval lengths rarely divide evenly into R3 joints, so the last few metres above the shoe are made up with pups or shorter joints ordered alongside the main R3 quantity.

When NOT to Specify R3

Read the first two rows together: the limit that matters is the rig's, and it has to reach the PO as a number.

Procurement trap — the short-tally trap: R3 with no average, no minimum and a joint count only

Wrong PO: "API 5CT, Grade L80, 9-5/8 inch × 47.00 lb/ft, BTC, Range 3, 300 joints."

What ships: compliant R3 casing — every joint between 10.36 and 14.63 m, with no average required by API 5CT. Take an illustrative batch with a heavy short end that averages 12.19 m: 300 × 12.19 = 3,657 m received, against a planned 3,850 m. The string is 193 m short, and the top-up is now a separate, urgent order. The mill has done nothing wrong; the PO never asked for more.

Correct PO: "API 5CT, Grade L80 Type 1, 9-5/8 inch × 47.00 lb/ft, BTC, Range 3, minimum average joint length 12.50 m, minimum individual joint length 11.00 m, quantity 310 joints / 3,875 metres minimum."

Three things changed: the type is named, the length band is closed from below, and the quantity is stated in metres as well as joints (310 × 12.50 = 3,875 m). For the rest of the PO, the OCTG casing purchase specification and RFQ checklist walks through every line.

Failure Modes

Failure Mode 1 — R3 joints longer than the rig can handle

Mechanism: R3 ordered without checking the rig's pipe-handling limit — the longest single joint the catwalk, pipe-handling system and elevators can safely bring to the rig floor. Illustrative scenario: the limit is 12.0 m. Compliant R3 runs to 14.63 m, so every joint between 12.0 m and 14.63 m is a handling problem, and the long ones have to be set aside or cut on site.

Diagnostic: compare the longest length on the mill's tally with the rig's handling limit before the pipe ships, not when it is on the catwalk.

Fix: write the limit on the PO. In this scenario: "Range 3, maximum individual joint length 12.00 m", agreed under Table C.22 note b. If the limit is below 10.36 m, R3 cannot work at all — order R2.

Failure Mode 2 — The short tally

Mechanism: the procurement trap above — a joint-count-only R3 order arrives compliant but short in metres.

Diagnostic: add up the per-joint lengths on the tally and compare the total with the string length you planned, before the pipe leaves the mill. That needs a per-joint tally, which is a purchase-agreement document — see Marking below.

Fix: state the quantity in joints and metres, and close the band from below with a minimum individual length.

Joint Length and Connection Cost — A Worked Example

For a 2,500 metre production casing string in 5½" P110 with premium connections:

Step-by-Step Calculation — R2 vs R3 for a 2,500 m String

Average joint lengths below are planning assumptions inside the Table C.22 bands (R2 7.62–10.36 m, R3 10.36–14.63 m); API 5CT does not set them. The connection price, make-up time and rig rate are illustrative assumptions, not quotes — replace them with your own.

Step 1 — Joint count at R2 (assumed average 9.0 m): 2,500 m ÷ 9.0 m/joint = 277.8 → 278 joints, 277 connections

Step 2 — Joint count at R3 (assumed average 12.2 m): 2,500 m ÷ 12.2 m/joint = 204.9 → 205 joints, 204 connections

Step 3 — Connections saved: 277 − 204 = 73 fewer connections with R3

Step 4 — Connection cost saving at an assumed $250/connection: 73 × $250 = $18,250 saved in connection cost

Step 5 — Rig time saving at an assumed 15 min per make-up: 73 connections × 15 min/connection = 1,095 min = 18.25 hours At an assumed $75,000/day rig rate: 18.25 hr × ($75,000 ÷ 24 hr) = $57,031 (about $57,000) rig time saving

Step 6 — Total combined saving from R3: $18,250 + $57,031 = $75,281 on a single 2,500 m string

Table: R2 versus R3 for a 2,500 m casing string, using the assumed averages, connection price and rig rate above

On these assumptions the R3 saving is about $75,000 on one string, and it repeats on every well in a programme. The structure of the sum matters more than the dollar figure: joint count scales with 1 ÷ average length, so the average you write on the PO is what the saving rests on. For how connection choice itself moves total cost, see premium versus API thread connection cost.

To carry that joint count on into the tonnes you will actually order, invoice and ship, follow the casing tonnage calculation from joints and metres.

How to Specify Length Ranges on a Purchase Order

A complete length specification on a casing purchase order includes:

1. Range designation — Range 1, 2 or 3, and which Table C.22 row applies: casing, tubing (or casing used as tubing), or integral tubing connections
2. Minimum average joint length — API 5CT sets none, so state your own as an agreed term (e.g. R3 with min average 12.50 m)
3. Minimum individual joint length — if tighter than the range minimum (e.g. R3 with min individual 11.00 m)
4. Maximum individual joint length — only if the rig, yard or liner has a handling limit below 14.63 m
5. Pup joints — lengths and quantities, noting any that are not on the Table C.22 list
6. Quantity — in both joints and linear metres, so a short-joint run cannot leave you short of string

Example purchase order length specification:

API 5CT, Grade P110, 5½" × 20.00 lb/ft, BTC, Range 3, minimum average joint length 12.50 metres, minimum individual joint length 11.00 metres, quantity 205 joints / 2,562 metres minimum.

When the length line is ready, send it with the rest of the order details through our casing quotation request form. The ZC casing and tubing product range shows the sizes, grades and connections we supply.

Is Joint Length Marked on the Pipe?

No — API 5CT 11th edition does not require the length to be marked on each joint. Clause 10.3 sets the stencil location and refers to Table C.43 for the marking sequence, and Table C.43's 18 items — manufacturer, "5CT", date of manufacture, size, mass, grade, heat treatment, process of manufacture, supplementary requirements, hydrostatic test pressure, thread type, drift, serialization and so on — contain no length item.

What the standard does require is that length be measured. Clause 7.6: "The length of each finished product shall be determined for conformance to length requirements. Length determination shall be in meters and hundredths of a meter (feet and tenths of a foot)." The same clause sets the measuring accuracy at ±0.03 m (±0.1 ft) for lengths under 30 m (100 ft), and clause 9.13.6 says how threaded-and-coupled pipe is measured: with the coupling installed, "from the end of the pin to the outer face of the coupling".

If you want that measured length on the joint, ask for it. Clause 10.1.10: "Other additional markings are allowed and may be applied as desired by the manufacturer or as requested by the purchaser, but shall be applied after the markings specified in Table C.43 or Table E.43." Put "stencil measured length on each joint" on the PO and it becomes a contract term.

Traceability per joint follows the same logic. Clause 5.4.2 makes serialization mandatory only for C90, T95, C110 and Q125: "Each length of pipe shall be uniquely numbered so that test data can be related to individual lengths." Clause 5.4.1 requires heat-and-lot tracing for C110, Q125, "and for other Grades when specified in the purchase agreement". For L80 or P110, nothing ties a measured length to a joint number unless you specify it. The certificate content in clause 12.3 does not list individual lengths either, so a per-joint tally — joint number against measured length — is a document you name on the PO. Our guide to mill test certificates and EN 10204 covers what the MTC does carry.

References

• API Specification 5CT, 11th edition — Specification for Casing and Tubing (American Petroleum Institute): clauses 5.4, 7.6, 9.13.6, 10.1.10, 10.3, 12.3; Tables C.22 / E.22 and C.43
• ISO 11960 — Petroleum and Natural Gas Industries: Steel Pipes for Use as Casing or Tubing