Directional Drilling

# What Happens During a Directional Drilling Pullback

TLDR

Pullback draws the reamer and product back through the finished hole. It succeeds or fails on **hole cleaning**, a free-spinning **swivel**, and steady, monitored **pull tension**.

Last updated October 20, 202614 min read

During pullback the rig draws a reamer, swivel, and the product line back from the exit point to the rig while circulating drilling fluid. The reamer sizes and conditions the hole, the swivel keeps rotation off the product, and the crew watches pull tension and fluid returns continuously. The pull is planned to run start to finish without stopping.

## What has to be finished before pullback starts?

Pullback is not the moment to discover an unfinished detail. Before the reamer turns for the pull, the pilot has been tracked and logged, the hole has been reamed to final size, returns are circulating, and the product is strung out, joined, tested, and supported along its full length.

Product preparation is the item most often rushed. Fused HDPE joints need their bead condition checked and their cooling time respected before the line takes tension. A joint pulled before it has cooled becomes a failure in the middle of the hole, where nothing can be done about it.

- Pilot log complete, with the path verified against the profile and every crossing clearance.
- Final ream and a clean-out pass finished, with steady returns.
- Product joined, cooled, and verified continuous before it goes anywhere near the hole.
- Rollers or skates set so the product never drags on grade or rides across a curb edge.
- Clear layup area for the full length, or a controlled bend radius layout where space is tight.
- Fluid volume, pump capacity, and containment sized for the whole pull, not the first half.

## How does the reaming sequence set up the pull?

A pilot hole is too small to accept the product. Reaming brings it up to final size in passes, and the final hole is intentionally larger than the product outside diameter so fluid can move around the pipe and drag stays manageable. The oversize is a planned dimension driven by soil, product size, and length, not a decision made at the exit pit.

How many passes it takes is a ground question. Stable material tolerates larger steps. Loose sand, heavy cuttings loads, and long shots do better with smaller increments so the annulus is never asked to carry more than the fluid can move.

The last pass before the pull is often a swab or clean-out pass with little or no cutting action. Its job is to circulate the hole, confirm it is open end to end, and leave conditioned fluid in place for the product to slide through.

## What is in the pullback assembly?

Behind the drill string the pullback assembly is short, and every component has one job.

The swivel is the least appreciated part and the most likely to cause damage when it fails. A swivel that binds transmits reamer rotation straight into the product. HDPE will twist, and a bundle of ducts will corkscrew, which shows up weeks later as a duct that will not accept a fiber blow or a tracer wire wrapped around the bundle.

The breakaway link exists so that when something goes badly wrong, the assembly parts at a known load in a known place instead of stretching the product to failure somewhere in the middle of the crossing.

- Reamer: sizes and conditions the hole and mixes fluid with the formation ahead of the product.
- Swivel: separates rotation from tension so the reamer can turn while the product does not.
- Breakaway or weak link: a deliberate failure point set below the product allowable tensile load.
- Pulling head or grip: transfers load into the product without crushing or necking it.
- Shackles and connecting hardware rated for the load and inspected before the pull begins.

## How is pull tension controlled?

The rig can pull harder than the product can survive. That is the entire reason tension is monitored. The controlling limit is the product allowable tensile load, taken from the manufacturer for that specific pipe and wall thickness and reduced by the safety factor the design calls for. The rig rated pull is not the limit that matters.

Tension comes from several sources at once: friction between the product and the hole wall, buoyant force pressing an empty pipe against the crown of the bore, capstan effect where the path bends and load multiplies through the curve rather than simply adding, and surface drag if rollers are missing or badly spaced.

The control measures are simple and effective. Ballast the conduit with water to reduce buoyancy, keep the path gentle so capstan multiplication stays low, roller support the entire surface run, maintain fluid circulation for lubrication, and watch the tension readout continuously so a rising trend is caught while it is still a trend.

## What sets the pace of the pull?

Pull speed is a balance, not a race. The reamer has to cut and condition the hole ahead of the product, and the pump has to deliver enough fluid to carry those cuttings away. Pull faster than the fluid can clean the hole and the annulus loads with cuttings, pressure climbs, and tension follows.

The pace that works depends on the ground, the reamer, the product size, and pump output. Crews watch returns and tension together. When returns thicken or tension trends upward, they slow the pull and let circulation catch up instead of forcing the product forward.

Rod handling sets a rhythm of its own. Each rod broken out at the rig is a brief pause in forward motion, and a well organized crew keeps those pauses short and keeps fluid moving through every one of them.

## Why should a pullback not stop?

Drilling fluid is thixotropic. It gels when it stops moving, which is useful for suspending cuttings and unhelpful the moment you want to move again. Break-out tension after a stop is always higher than the running tension was before it.

The hole is not static either. Cuttings settle, the wall relaxes, and in loose saturated sand the annulus can begin to close around the product. Every minute of a stopped pull raises the load required to restart it.

So pulls are planned to run continuously: enough hands for rod handling, enough fluid mixed and staged, a fueled rig, and a crew that stays in position from start to finish. If a stop becomes unavoidable, keep circulating, rotate the reamer if it can be done safely, and restart deliberately rather than snatching at the load.

## What goes wrong during pullback, and what prevents it

Nearly every pullback failure traces back to one of six causes, and each of them has a control that costs less than the failure.

| Risk | What causes it | Control |
| --- | --- | --- |
| Product stretch or separation | Tension above allowable load, aggressive doglegs in the path | Weak link set below the product limit, gentle path, live tension monitoring |
| Stuck pull | Hole collapse, packed annulus, or a stopped pull | Staged reaming, clean-out pass, continuous circulation, no unnecessary stops |
| Twisted or corkscrewed duct | A binding swivel transmitting rotation into the product | Inspect and service the swivel, confirm free rotation before the pull |
| Damaged pipe wall | Dragging on grade, curb edges, missing or misplaced rollers | Roller support the full surface run, station a spotter at the entry |
| Inadvertent return during the pull | Annular pressure buildup from a loaded hole | Manage cuttings load, keep returns flowing, walk the alignment |
| Conduit riding high in the hole | Empty pipe floating below the water table | Ballast the product with water before the pull |

## How does pulling a bundle of ducts change the job?

Many fiber bores pull more than one duct at a time, often with a tracer wire alongside. A bundle needs a larger final hole than a single duct, and the pulling head has to share load among the ducts so one pipe does not carry the whole pull while the others ride along.

Each duct in the bundle has its own allowable load, and the breakaway link is set against the weakest member of the assembly, not the combined strength. Ducts are strapped together at intervals so they enter the hole as one unit, and the tracer wire is fastened so it stays with the bundle instead of wrapping around it.

Layout takes more room as well. Several reels or coils have to feed at the same rate, and a duct that lags behind the others can kink where the bundle enters the hole. A crew member watching the bundle at the product end is as important as the operator watching tension at the rig.

## What happens at each end of the hole?

At the exit side the crew builds the assembly, controls fluid, and feeds the product in cleanly. The entry side at the rig is where returns and spoil are managed. Both ends are where the public and the inspector form their opinion of the job, because both are visible from the street.

Excess fluid is contained and hauled rather than allowed to run into a swale, an inlet, or a wetland. Pits are backfilled and compacted, pavement patches are made to the permit standard, sod or seed matches what was there, and the site is swept before the crew leaves.

Restoration is not a courtesy step. On county and FDOT right of way permits it is a stated condition, and it is frequently the item standing between a finished bore and a released permit.

## How is the installation proven after the pull?

A conduit in the ground is not yet an accepted conduit. Proofing follows the pull: run a mandrel sized to the duct to confirm the bore is round and unobstructed, verify tracer wire continuity, then cap and mark the ends so the duct stays clean until fiber goes in.

For fiber the verification chain continues. Cable is blown or pulled with tension and bend radius limits respected, slack is stored at splice points and access points so future maintenance does not require cutting into the span, and splices are fusion spliced and tested.

Splices are then confirmed with bidirectional OTDR testing and an end to end loss check against the design loss budget. For the bore crew, the point is simpler: a duct that proofed clean and a tracer that tested continuous mean the splicing crew starts on a sound pathway, and any loss they find is a splicing question rather than a construction one.

## What belongs in the closeout package?

The pull is finished when the paperwork is finished. A closeout package that lets an owner operate and maintain the plant generally contains a defined set of items, assembled while the work is happening rather than reconstructed afterward.

- As-built drawing showing the bore path, stations, depths, and crossing clearances.
- Pilot log and pullback record, including tension observations and any anomalies.
- Pothole log with exposed utilities, measured depths, and achieved separation.
- Sunshine 811 ticket numbers and locate documentation covering the work window.
- Photographs of pre-existing conditions, exposed crossings, and completed restoration.
- Mandrel proofing and tracer wire continuity results.
- Splice and test data where fiber was placed, including OTDR traces and end to end loss.
- Permit closeout correspondence and inspection sign-offs.

## Key takeaways

- The controlling pullback limit is the product's allowable tensile load, not the rig's rated pull.
- A pullback should run start to finish, because drilling fluid gels and the hole relaxes whenever the pull stops.
- A binding swivel can twist HDPE duct or corkscrew a bundle, and the damage often shows up only when cable is installed.
- Filling HDPE conduit with water before the pull reduces buoyancy, friction, and peak tension below the water table.
- A conduit is accepted only after mandrel proofing, tracer wire continuity testing, and documentation, not when it reaches the rig.

## Key terms

**Pullback**: The final stage of a horizontal directional bore, in which the rig draws a reamer, a swivel, and the product line from the far end of the bore back to the rig through the reamed hole while drilling fluid circulates.

**Swivel**: A rotating connector between the reamer and the product. It lets the reamer turn with the drill string while the product follows without rotating, so HDPE duct and bundled ducts are not twisted during the pull.

**Breakaway link**: A deliberate weak point in the pullback assembly, rated below the product's allowable tensile load. If tension climbs too high, the link parts at a known place and load, which protects the product from stretching or separating inside the bore.

**Allowable tensile load**: The maximum pulling force a specific pipe or duct can take without damage, published by the manufacturer for that size and wall thickness and reduced by the design safety factor. It is the number that governs a pullback, not the rig's capacity.

**Mandrel proofing**: A test in which a plug sized to the duct is pulled or blown through installed conduit. Clean passage confirms the duct is round, continuous, and free of crushing or debris before cable placement begins.

*What the crew watches during a pullback*

| Signal | Normal | Warning sign | Typical response |
| --- | --- | --- | --- |
| Pull tension | Steady, with a gradual rise as more product enters the hole | Sharp climb or sudden spikes | Slow or pause, keep circulating, and diagnose before pulling harder |
| Fluid returns | Steady flow carrying cuttings | Returns slow, stop, or turn very thick | Reduce pull speed, check for fluid loss, and walk the alignment |
| Rotary torque | Consistent for the ground being reamed | Torque rising along with tension | Possible packoff, so slow down and let circulation clean the hole |
| Pump pressure | Stable at the planned rate | Pressure rising without more flow | Annulus may be restricted, so ease off and watch for surface returns |
| Product at the far end | Feeding smoothly off rollers | Product stalls, twists, or drags on grade | Stop and correct rollers, swivel, or layout before continuing |

*Pilot bore, ream and pullback*

## What this means for your project

Pullback is the step where most of a bore's value is either delivered or lost. A stuck or damaged product can mean abandoning the hole, drilling a new one, and paying for a second round of restoration and permitting. Asking how the contractor sets the weak link, monitors tension, and avoids stops is a quick way to judge pullback risk before the job starts.

Schedule the pull with margin. A pull should not start late in the day, ahead of a forecast storm, or before fluid, crew, and product are all staged, because a forced stop raises the load needed to restart. A pull pushed back a day so it can start properly almost always costs less than one that stops halfway.

Make post-pull proof part of the deliverable. Mandrel results, tracer wire continuity, tension notes, and photographs of capped duct ends confirm the conduit is usable before fiber crews arrive. Without them, problems surface during cable placement, after the bore crew has demobilized, when finding the fault costs more.

## Related reading

- [Pullback operationsPlanned, monitored pulls of conduit and bundles through reamed bores.](https://strillacommunications.com/services/directional-drilling/pullback-operations)
- [Staged reaming before the pullOpening the pilot hole to final size in passes the ground can support.](https://strillacommunications.com/services/directional-drilling/reaming-services)
- [HDPE conduit placementSelecting, joining, and placing the duct that rides behind the reamer.](https://strillacommunications.com/services/conduit-installation/hdpe-conduit-placement)
- [Proving the duct after installationMandrel, swab, and pressure testing before cable goes in.](https://strillacommunications.com/services/conduit-installation/conduit-verification)
- [Restoration after a boreHow pits, pavement, and turf are put back once the pull is done.](https://strillacommunications.com/blog/how-restoration-is-handled-after-directional-drilling)
- [What a closeout package should containThe records a project manager should receive when the job closes.](https://strillacommunications.com/blog/what-project-managers-should-expect-from-a-closeout-package)

## Frequently Asked Questions

**How much larger than the product should the final hole be?**: Larger than the product outside diameter by an amount the design sets from soil, length, and product size. The goal is enough annular space for fluid to circulate around the pipe and carry cuttings, without so much space that the hole becomes hard to keep open or generates excess spoil. It belongs in the bore plan, not in field improvisation.

**Can a pullback be reversed if it gets stuck?**: Sometimes, and it is rarely a good outcome. Backing off can free a mechanically pinched assembly, but in collapsing ground it often loads the annulus further and makes the situation worse. The better answer is prevention: proper reaming, a clean hole, continuous circulation, and tension watched closely enough that a rising trend is noticed before it becomes a stall.

**Why fill the conduit with water before pulling?**: An empty pipe in a fluid filled hole is buoyant. It presses against the crown of the bore, which increases normal force and therefore friction, and the effect grows with installed length. Filling the product with water brings it closer to neutral buoyancy, lowers drag, and reduces peak tension. The water is drained after the pull is complete.

**What tension reading should the crew watch for?**: The number that matters is the product allowable tensile load from the manufacturer, reduced by the design safety factor, not the rig rated pull. The shape of the curve matters just as much. Steady tension with gradual increase is normal, while a sharp climb signals a collapsing hole, a bind, or an obstruction, and it is a reason to pause and diagnose rather than pull harder.

**Is fiber cable pulled directly through the bore?**: Rarely. The usual practice is to pull HDPE conduit through the reamed hole and place fiber later by blowing or pulling it into the duct. Conduit protects the cable from pullback forces, abrasion, and ground movement, and it lets the cable be replaced or upgraded without a new bore. Pulling cable straight into a bore is uncommon and calls for cable designed for that use.

**Should the final ream and the pullback happen on the same day?**: Ideally they happen close together. A reamed hole starts to deteriorate once circulation stops, especially in saturated sand, where the wall can slough and cuttings settle. Many crews plan the final ream, a clean-out pass, and the pull as one continuous sequence. Where that is not possible, a swab pass just before the pull confirms the hole is still open end to end.

**What happens to the drilling fluid left in the hole?**: Fluid left in the annulus around the installed product normally stays in place and gels. Bentonite is a natural clay, and the gelled fluid fills the space between the product and the soil. Some designs call for grouting the annulus instead, usually on larger pipe or where settlement is a concern. Fluid that returns to the pits is contained, then recycled or hauled away.

## Related services

- [Pullback OperationsControlled pullback of HDPE conduit, multi-duct, and cable on Florida bores. Monitored tension, swab passes, and proofing before the pits are closed.](https://strillacommunications.com/services/directional-drilling/pullback-operations)
- [Reaming ServicesBack reaming and hole conditioning for directional bores in Florida sand, shell, and limerock. Correct hole size, fluid volume, and passes for clean pullback.](https://strillacommunications.com/services/directional-drilling/reaming-services)
- [Conduit InstallationHDPE duct, innerduct, and microduct placed by bore, trench, or plow, proofed with a mandrel, and made locatable with tracer wire and marker tape.](https://strillacommunications.com/services/conduit-installation)
- [HDPE Conduit PlacementHDPE conduit placement by directional bore, trench, or plow in Central Florida: wall rating, fused joints, controlled pull tension, and sealed, proofed runs.](https://strillacommunications.com/services/conduit-installation/hdpe-conduit-placement)
- [Fiber PullingFiber optic cable pulling through Florida conduit and duct. Monitored pulling tension, correct swivel and grip rigging, lubrication, and bend radius control.](https://strillacommunications.com/services/fiber-splicing-installation/fiber-pulling)

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Source: https://strillacommunications.com/blog/what-happens-during-a-directional-drilling-pullback