What Causes Stuck Pipe? – Mechanisms and First Actions

The driller picks up off bottom for a connection and the weight indicator climbs past normal. He slacks off, and it won't go down either. Now the rotary stalls out and everybody on the floor gets quiet. Stuck pipe is one of the most expensive problems on any rig, and the first few minutes decide how bad it gets. So, what causes stuck pipe, and what should the crew do first?

Stuck pipe is caused by one of three mechanisms: differential sticking, packoff (or bridging), and wellbore geometry. Differential sticking happens when mud pressure pins the pipe against a permeable zone. Packoff happens when cuttings, caving shale or junk fill the annulus around the string. Geometry sticking happens when the hole shape, such as a keyseat, ledge, dogleg or undergauge section, won't let the BHA pass. Your first move depends on which one you've got, and you figure that out by asking three questions: can you circulate, can you rotate, and was the pipe moving when it stuck?

What Is Stuck Pipe, Exactly?

Stuck pipe means the drill string can't be pulled out of the hole without exceeding a safe limit, and often can't be rotated or lowered either. The SLB Energy Glossary definition of stuck pipe puts it simply: a drillstring that can't be rotated or moved along the axis of the wellbore.

It isn't the same thing as tight hole. Tight hole is a warning. You see extra overpull or drag, but you can still work through it. Stuck pipe is what happens when the warnings get ignored or the hole changes faster than anybody expected.

Here's the part that makes it so costly. Every hour spent stuck is rig time, and if the pipe can't be freed you're looking at backing off, fishing, and maybe sidetracking around lost tools. Downhole tools like MWD and motors aren't cheap to leave behind, either.

What Are the Three Types of Stuck Pipe?

Almost every stuck pipe event fits into one of three buckets. Learn them cold, because the fix for one can make another one worse.

1. Differential Sticking

The mud column in the hole is heavier than the pressure in a permeable formation, like a sandstone. That overbalance pushes the pipe into the filter cake on the wall. The contact area grows the longer the pipe sits still, and the force holding it there grows with it.

It almost always happens when the string is stationary, like during a connection, a survey or a long wait. Classic picture: full circulation, no rotation, no movement. If you want the whole breakdown and freeing procedure, read our article on differential sticking.

2. Packoff and Bridging

Packoff means something has filled the annulus around the string and locked it in place. That something might be:

• Cuttings that settled out because hole cleaning fell behind
• Shale that's caving or sloughing off the wall
• Unconsolidated sand or gravel falling into the hole
• Fractured or faulted rock breaking off in chunks
• Cement blocks or soft cement around casing shoes
• Junk, like a lost hand tool or broken bit parts

The signature here is pressure. When the annulus packs off, pump pressure spikes and circulation gets restricted or stops completely. You may also see torque climb and drag build before it locks up.

3. Wellbore Geometry

Geometry sticking is when the hole itself is the wrong shape for what you're trying to pull or push through it. Common culprits include keyseats worn into a dogleg, ledges between hard and soft layers, sharp doglegs, undergauge hole from a worn bit, and a stiff BHA run into a crooked hole. Mobile formations like salt or plastic shale can also squeeze in on the string.

The giveaway is that circulation is usually normal. The pipe got stuck while it was moving, and often at a specific depth you've had trouble at before.

How Do You Tell Which Kind of Stuck Pipe You Have?

Don't guess. Ask the three questions, and ask them before anybody starts yanking on the string. Here's how the answers usually line up:

Real life doesn't always read the textbook. A packoff can sit there long enough that the pipe also gets differentially stuck. That's why you note everything the instant it happens: depth, string weight, torque, pressure, which direction you were moving, and how long since the last movement.

What Are the Warning Signs Before Pipe Gets Stuck?

Stuck pipe rarely comes out of nowhere. The hole usually tells you it's in trouble first. Watch for:

• Rising torque or erratic torque while drilling or reaming
• Increasing overpull on connections or trips
• Higher drag when slacking off
• Pump pressure creeping up with no change in rate
• Fill on bottom after a connection or trip
• Cuttings at the shakers that are bigger, splintered, or a different shape than drilled cuttings
• Low cuttings returns compared with how fast you're drilling
• Hole not taking proper fill on a trip out, or giving back too little on a trip in

One sign alone might be nothing. Two or three together at the same depth means stop and talk to the driller and the company man before you push your luck.

What Should You Do First When Pipe Gets Stuck?

First, follow your well-site stuck pipe procedure. Every operator and contractor has one, and the company man and toolpusher make the call. What follows is the general logic most of those procedures are built on, not a replacement for them.

The biggest rule of all: jar in the opposite direction of the movement when it stuck. If you were pulling up, work it down. If you were going down, work it up. Pulling harder in the same direction that got you stuck usually just sets it deeper.

First Actions for a Packoff

1. Drop pump pressure right away. Bring the pumps down to a low rate so you're not packing the annulus tighter.
2. Keep a low pressure trapped below the packoff if possible, and don't let it bleed off fast.
3. If you were pulling out, apply torque within the string's limits and slack off. Jar down.
4. Try to break circulation slowly. Once returns come back, increase rate gradually.
5. When you're free, circulate the hole clean before you trust it again.

Don't make this mistake: slamming the pumps on to blow it free. That usually compacts the cuttings and can break down a weak formation, which just adds lost returns to your stuck pipe.

First Actions for Differential Sticking

1. Keep circulating at the normal rate.
2. Slack off weight and apply torque within limits. Getting the pipe moving down and turning often breaks the seal.
3. Jar down first, then try up, following your procedure and the jar's limits.
4. If that fails, the team may spot a pipe-freeing fluid across the stuck zone and let it soak.
5. Reducing the overbalance is another option, but only if well control allows. That's never a floor-level decision.

First Actions for Geometry Sticking

1. If you stuck going up, jar down with light torque. If you stuck going down, jar up.
2. Keep circulating normally.
3. Once free, ream or backream through the bad spot instead of pulling straight through it again.

How Do Jars Help Free Stuck Pipe?

A drilling jar is a downhole impact tool built into the BHA. It stores energy as you stretch or compress the string, then releases suddenly to hit the stuck point with a hard blow. The SLB glossary entry on jars covers the basic types, which are mechanical and hydraulic.

A few practical points matter here. Jars only help if they sit above the stuck point. They need to be cocked properly and fired within their rated loads. Placement is planned in advance for exactly this reason, so the jar isn't buried in the stuck section.

Murphy loves to stick the string right across the jar. When that happens, surface jars or an accelerator on a fishing string may be the next step.

How Do You Free Stuck Pipe If the First Actions Fail?

If jarring and circulating don't get it done, the job moves into a more planned phase. The engineer and the company man will usually work through some version of this sequence:

• Soak with a spotting fluid for differential sticking, then work the pipe again
• Run a free point tool on wireline to find where the pipe is stuck and where it's still free
• Back off the string above the stuck point, usually with a string shot to loosen a connection
• Go fishing with an overshot, jars and accelerator to pull the remaining fish
• Cut and sidetrack if fishing becomes more expensive than drilling around it

There's a cost decision behind every one of those steps. At some point it's cheaper to plug back and kick off a new hole than to keep fishing, and that call belongs to the operator.

How Do You Prevent Stuck Pipe?

Stuck pipe prevention is mostly discipline. Nothing exotic, just doing the boring stuff right every single tour.

• Keep the pipe moving. Minimize static time across permeable zones, especially on connections and surveys.
• Clean the hole. Circulate enough flow rate and time to bring cuttings up, and rotate when you can, especially in deviated hole.
• Run the right mud weight. Enough to hold the hole up and control the well, but not so much overbalance that you invite differential sticking.
• Keep the mud in shape. Thin, tough filter cake, good inhibition in reactive shale, and proper rheology.
• Watch the trends. Torque, drag, overpull and pump pressure tell you a lot if somebody is actually watching them.
• Respect tight spots. Ream through them instead of pulling through hard. Note the depths on every trip.
• Design the BHA for the hole. Spiral collars, fewer stabilizers or a smaller contact area can help in sticky intervals.
• Check the bit gauge when you pull it, and ream back to bottom if it's worn.

A lot of crews run stuck pipe drills and post the decision tree on the floor. That's smart. You don't want the driller reading a procedure for the first time when the string has already locked up.

Is Stuck Pipe More Common in Directional and Horizontal Wells?

Yes, generally. Once the hole is deviated, the drill string lies on the low side of the hole instead of hanging in the middle. That gives it more contact area for differential sticking, and gravity drops cuttings onto the low side where they build into beds.

Those cuttings beds can slide back down the hole when the pumps go off, and that's a recipe for a packoff on the next trip. Doglegs from steering also create the bends where keyseats wear in.

None of that means directional wells are doomed. It means the hole cleaning plan, the rotation practices and the trip practices matter even more. Backreaming, circulating bottoms up a few times before a trip, and watching for drag at the build section are all part of the routine on a good directional crew.

Who Decides What to Do When Pipe Is Stuck?

The driller reacts first, because he's the one on the brake when it happens. His immediate actions should follow the posted procedure. After that, the toolpusher and the company man take over the planning, with input from the drilling engineer back in the office.

Don't freelance. I've never heard of a stuck pipe event that got better because somebody tried something clever and off-script. Overpulling past the string's limits can part the pipe, and now your stuck pipe is a twisted-off fish.

What Causes Stuck Pipe, and What's the Smart First Move?

Stuck pipe comes from three places: differential pressure holding the pipe to the wall, packoff from cuttings or caving rock, and wellbore geometry that won't let the BHA through. Figure out which one you have by checking circulation, rotation and which way the pipe was moving.

Then act fast but calm. Drop pressure on a packoff, keep circulating on differential sticking, and jar opposite to the direction you were moving when it stuck. Follow your rig's procedure, and let the company man and toolpusher make the bigger calls.

Best of all, don't get stuck in the first place. Keep the pipe moving, keep the hole clean, and pay attention when the torque and drag start talking to you.

← All Resources