Lubricants lower the friction between the drill string and the wellbore; spotting fluids are placed against a stuck string to help free it. Ironstone supplies both — extreme-pressure lubricants for water-based and oil-based mud, and spotting-fluid concentrates — with a certificate of analysis for every batch.
When friction between the drill string and the wellbore becomes a problem — usually in directional, extended-reach, or horizontal holes where the string drags along the low side. High friction shows up as high torque while rotating and high drag while moving the string. A lubricant adds a slippery film between the steel and the rock, which lowers torque and drag and reduces wear on the string and casing. Oil-based muds are already lubricating, so lubricant additives are mostly a water-based-mud concern.
A spotting fluid is a treated volume of fluid pumped down and placed (“spotted”) across the stuck part of the drill string when the pipe is differentially stuck. This happens when the string presses into a thick filter cake against a permeable formation and the pressure of the mud column holds it there, like a suction. The spotting fluid is designed to soak into and break down that filter cake, releasing the string. It is pumped as soon as differential sticking is diagnosed — the longer the string sits, the harder it is to free — and it is usually left to soak for several hours, with the string worked as it soaks.
Enough to cover the stuck length of the string with a safe margin. Field practice is to calculate the volume needed to fill the annulus across the stuck bottom-hole assembly, then add extra — commonly around 100 percent excess — so the whole stuck interval stays covered as some fluid moves and some soaks into the cake. Some volume is also kept inside the string so the spot can be advanced during the soak. We send the product data sheet with placement and soak guidance when we quote.
| Step | What to do |
|---|---|
| Diagnose | Confirm the sticking is differential (string moves at first, no circulation loss) before spotting. |
| Volume | Annular volume across the stuck assembly, plus a margin (commonly ~100% excess), plus a string volume to advance the spot. |
| Soak | Place across the stuck interval and let it soak several hours; work the string within safe limits as it soaks. |