HWDP and Drill Collars: NC50 Weight Basis and Recess Selection

Shared connection names do not close a substitution

A request for “5 in NC50 HWDP” leaves important purchasing questions unanswered. It identifies useful features, but it does not distinguish every assembly carrying those features. If a quotation changes the HWDP configuration while retaining the connection label, the change can disappear from a short commercial description.

The buyer's task is to keep the requested configuration, offered configuration and supporting documents connected. Use a change-control worksheet before comparing prices. This is a document-selection guide, not a bottom-hole assembly design or a recommendation about where to place a component in a drill string.

Read two catalogue rows without merging them

The NOV Grant Prideco HWDP table lists Standard and Spiral-Wate configurations at 5 in nominal size with NC50 connections and 6-5/8 x 3 in tool-joint OD and ID. Standard lists 50.38 lb/ft as adjusted weight; Spiral-Wate lists 59.16 lb/ft as approximate weight including tube and tool joints.

The page gives a 31 ft nominal basis for its per-joint figures. Preserve the distinction between per-foot and per-joint entries and between the weight headings. Matching nominal size and connection does not make the configurations identical.

The NOV drill-collar slip-recess table belongs to a different comparison: its 6-1/2 in collar-diameter row gives a 6 in recess diameter. That family reference does not describe a complete collar model.

Build a change-control worksheet

Record changes individually rather than accepting one overall “same specification” statement. A useful worksheet separates confirmed differences from information that has not been supplied.

Attach the document reference to each answer. When a revised offer arrives, compare changed fields rather than assuming that a new price leaves the technical scope untouched.

Do not manufacture a missing wall dimension

The cited HWDP rows identify tool-joint dimensions; they do not supply the tube-body wall and grade needed for a complete purchase specification. A tool-joint ID cannot fill the missing tube-bore field. Label the absence and request the selected configuration's drawing and material schedule.

The same discipline applies to the collar reference. A recess dimension cannot establish the collar bore, complete geometry or compatibility with a particular handling tool. Keep the collar line separate from HWDP, even when both are purchased for the same project. Related equipment does not share every dimension or acceptance document.

This prevents a spreadsheet from becoming more certain than its sources. An openly incomplete row is more useful than a complete-looking row assembled from unrelated component dimensions.

Fictional desk review: a hidden configuration change

Imagine a buyer requests Standard HWDP and receives a response labelled only “5 in NC50.” The attached weight is taken from the Spiral-Wate row, while the drawing attachment has not been identified. A second line offers a drill collar but supplies only the family recess pair.

The HWDP response needs a confirmed configuration and a consistent drawing reference. The collar response needs a complete dimensional identity. Neither problem is resolved by accepting the shared connection description or by treating a larger listed weight as automatically preferable.

Ask for corrected, separately identified lines. Preserve the original request and mark whether each revision corrects a clerical error or proposes a substantive alternative. That distinction gives the responsible reviewer a clear decision to make without predicting performance from incomplete information.

Carry the open questions into the RFQ

For each assembly, specify quantity, new or replacement scope, required inspection records, marking and traceability expectations. Identify any retained components so that interface questions are visible. The responsible engineer must assess suitability; the purchasing worksheet only organizes the documents supporting that assessment.

The drill-collar and HWDP reference keeps the catalogue rows separate. Use the HWDP RFQ Builder to request configuration drawings and responses to the unresolved fields. The image is an AI-generated downhole-tool category reference, not a photograph of these configurations. Catalogue references do not establish availability or a manufacturer's authorization to supply.