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Drawing a well schematic others can trust

Collect the right documents, build casing and completion tables, and produce a schematic that matches what is really in the hole.

Field
Production engineering
Level
Beginner
Time
12 min

The picture

20 in casingshoe 400 m13-3/8 in casingshoe 1400 m9-5/8 in casingshoe 2600 m7 in linershoe 3000 mTubing 3-1/2 inTop of cement9-5/8 in, 900 mPacker, 2650 mPerforations2800 to 2900 mTotal depth 3000 mSurface
Illustrative example, not to scale across string widths. Every item should have a depth, a size, a source document and a date.

The workflow

  1. Collect the source documents

    In: Drilling reports, casing tally, cement reports, completion reportOut: A list of documents with dates

    Start from the final well report, then add every workover or intervention after it. The latest document that touched a piece of equipment is the one to trust.

  2. Build the casing table

    In: Casing tally and drilling reportsOut: A table of each string: size, weight, grade, top, shoe

    List every string from the conductor down to the production casing or liner: outer diameter, weight, grade, top depth and shoe depth. Write down whether each depth is measured depth (MD) or true vertical depth (TVD).

  3. Add hole sizes and cement

    In: Cement reports, bond logsOut: Cement tops and hole sizes behind each string

    Show the hole size drilled for each section and the top of cement behind each casing. If the cement top is estimated rather than confirmed by a log, say so.

  4. Add the completion

    In: Completion report and workover reportsOut: Tubing, packer, valves and perforations at their depths

    Add tubing (size and depth), packer, safety valve, nipples, sliding sleeves, and the perforated intervals with their status: open, squeezed or isolated by a plug.

  5. Check it against itself

    In: The finished table and drawingOut: A schematic with no contradictions

    Check that depths increase in order, that tubing fits inside the casing with room to pass tools, and that each perforation sits inside a cemented string. Mark anything you could not confirm.

What you hand over

A schematic plus an equipment table, each item with its depth, size, source document and date.

Background

What a schematic is for

A well schematic is a drawing of what is in the well and where. Drilling, production, reservoir and well-integrity teams all use it, and many decisions are based on it: whether a tool will pass, where to perforate, whether a barrier is in place.

A schematic is only useful if people can trust it. That trust comes from the table behind the drawing: every item has a depth, a size, a source and a date.

Work from the table, not the picture

Build the equipment table first and generate the drawing from it. If you draw first and add numbers later, small contradictions creep in, and they are hard to see in a picture.

Say what you do not know

If a cement top is estimated, or a depth comes from a plan rather than a report, mark it. An honest gap in the schematic is safer than a confident guess.

Common mistakes

  • Mixing MD and TVD in the same table.
  • Drawing the well as planned rather than as built.
  • Leaving out workovers, so the schematic shows equipment that was pulled years ago.
  • Forgetting plugs, fish and abandoned perforations.
  • Not recording the source and date, so nobody knows how far to trust the drawing.

Check yourself

1. Which version of the well should a schematic normally show?
2. Why do you record both MD and TVD?
3. A perforated interval was squeezed off in a later workover. How should the schematic show it?

Try this workflow in SchemaTech

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