Definition
Fill-Up Tool — A fill-up tool is a device stabbed into the top of a casing string that fills it with mud as it is run and can circulate through it, maintaining hydrostatic pressure and avoiding the need to break connections to top up fluid.
Also known as: fill-up tool, casing fill-up tool, fill-up and circulating tool
What a fill-up tool does
A fill-up tool allows the crew to add drilling fluid to a casing string quickly as it is lowered into the well. Running casing empty lets it float or reduces the hydrostatic head, so the string must be filled at intervals. A fill-up tool seals against the casing bore and delivers mud through a control valve, filling each joint or stand without waiting for slow gravity fill or breaking a connection.
Fill-up and circulating tools add a pack-off so the crew can also circulate to condition the hole, break gel strength or push through a tight spot. Both maintain the hydrostatic column that keeps the well controlled while casing is being run.
Well control during casing running
Keeping the casing full maintains hydrostatic pressure against formation pressure. If a string is run too empty or too fast, the fluid level and hydrostatic head can drop, and surging or swabbing can disturb the balance. A fill-up tool supports steady, controlled running and hole condition.
Why it matters for rentals
Reliable fill-up and circulating equipment keeps casing running safe and efficient. Rental tools should seal correctly for your casing bore and pressure rating. See our casing accessories and casing running application, or contact us with your specs.