Ultimate QC free sag check ← ultimate qc

BHA sag check — free

Describe or upload your BHA and we solve it with a stiff-string finite-element model — Euler–Bernoulli beam, unilateral low-side wall contact, buoyed weight — the same engine that runs on our live wells. Check one inclination or upload a whole survey and download it corrected. No account needed.

What the model assumes — read before trusting the number

Hole & survey point

The single inclination is ignored when you supply a whole survey below.

BHA — bit up

Format: list the string from the bit upward, one row per element with its own length — positions follow from the stack, so a stabilizer goes in as its own short element exactly where it sits. Blades act at the middle of the element unless you say otherwise: the amber "blade mid" column shows the computed blade-mid-from-bit as its placeholder — if your tally disagrees, type the true gauge-band centre (m from bit) right there and the model pins the blade where you said. A component carrying several gauges (an RSS, a sleeve-stabilised motor) lists its blade ODs and its mid positions separated by ; — e.g. blade OD 8.375; 8.25, mid 0.6; 2.4 (a comma stays a decimal comma). Lengths in metres, diameters in inches. A wall contact = any row with a blade/gauge OD (the bit gauge counts); leave it empty for plain collars, MWD and pipe.
You don't need the exact blade length or shape. Sag is governed by the long unsupported collar spans between stabilizers, so a few centimetres of blade position or whether the blade is straight/spiral changes the correction negligibly — what matters is which sub the stabilizer is and how far from bit it sits.
componentlength mbody OD in body ID inblade/gauge OD in stiff OD in stiff ID in blade mid from bit blade len m blades wrap ° total
accepted columns for the BHA file (.xlsx / .csv)
Header row anywhere in the first sheet; extra columns ignored; rows without a numeric length+OD skipped. Accepted names (case/units ignored):
component — name component description element tool
length, m — length length (m) len
body OD, in — OD body OD collar OD
body ID, in — ID body ID bore
blade OD, in — blade OD stab OD gauge contact OD
stiffness section, in — stiff OD stiff ID structural OD/ID
Russian service workbooks: «КНБК…» tally sheets (№ п.п. / Наименование / Диаметр Внутр-Наруж / Макс. Наружный / Длина, mm and two rows per component) are auto-detected anywhere in the workbook and converted mm→in — stab blades kept separate from bodies, drill-pipe tool joints not treated as blades.
PDF: text-based BHA sheets are read line-by-line as name length OD [ID] [blade] — always CHECK the filled table before computing; scanned/graphic PDFs are refused (export .xlsx/.csv then).

Conditions at the survey — asked, never assumed

Hole opener / under-reamer (optional — makes the hole two-diameter, pilot below it, opened above; this is modelled per contact):
Casing (optional — above the shoe the diameter is known exactly, so no gauge assumption applies there; casing ID is wider than the hole drilled through it, so a stabilizer inside it rests a little lower):
Washout (optional — a measured enlarged section, from a caliper. This is modelled as a real diameter: a stabilizer inside it rests lower or stops touching altogether, and the span it was holding lengthens. Deflection goes with the fourth power of span, so a washout at a stabilizer can be worth more than the correction itself — it can even reverse its sign):
Pumps on, off-bottom pick-up and push-the-bit RSS are outside the static beam model — the answer still computes but is graded REDUCED with the reason shown. A stated motor bend / point-the-bit setting IS modelled.

Whole survey — optional

One station per line: MD  Inc or MD  Inc  Azi (spaces, commas or tabs). With azimuths we also compute the TVD shift the correction makes at your deepest station. File columns accepted: MD/depth, Inc/inclination, optional Azi/azimuth.

Your result

The result appears right here. We keep your email to follow up about Ultimate QC — nothing automated, no spam.

Sag correction

Sign convention: Δ is added to the raw survey (corrected = raw + Δ). On our live service this runs on every station automatically — watch the demo wells or request access.