Completion Packers – Types and How They Set
A well can have perfect perforations and brand-new tubing and still be in trouble if reservoir pressure gets into the casing annulus. Corrosive fluids, high pressure and leaks all go after the casing when nothing keeps them out. One piece of hardware stands guard deep in the well, and most people never see it. What is a completion packer, and how does it set and seal?
A completion packer is a downhole tool that seals the space between the production tubing and the casing, so well fluids flow up the tubing instead of the annulus. It sets in two moves: steel slips with teeth bite into the casing wall to anchor it, and rubber packing elements are squeezed outward until they seal against the casing. Packers are set mechanically (by tubing rotation, pull or set-down weight), hydraulically (by tubing pressure), or on wireline with a setting tool.
Permanent packers stay in the well and have to be milled out to remove, while retrievable packers can be released and pulled with the tubing. The right choice depends on pressure, temperature, how often the well will be worked over and what else the completion needs to do.
What Does a Production Packer Actually Do?
A production packer has a few jobs, all tied to control and protection:
- Isolates the annulus so reservoir pressure and fluids stay inside the tubing.
- Protects the casing from corrosive fluids like CO2 and H2S.
- Anchors the tubing so it doesn't move too much with pressure and temperature changes.
- Separates zones in multi-zone wells so each zone can be produced or shut off on its own.
- Serves as a well barrier, part of the system that keeps the well safe if something fails above it.
It also makes the annulus useful. With a packer in place, the annulus can be filled with inhibited packer fluid, monitored for pressure, or used to carry gas lift gas down to the valves.
How Does a Completion Packer Set?
Every packer, whatever its type, uses the same basic idea. Force moves parts of the packer body relative to each other. That pushes the slips out onto cones so they grip the casing, then squeezes the rubber elements so they expand and seal.
The setting methods differ in where that force comes from:
- Mechanical set. The crew rotates the tubing to release a J-slot or similar latch, then sets down weight or pulls tension. Simple and reliable in vertical wells, harder in deviated ones where weight and torque don't transfer well.
- Hydraulic set. A plug or ball seat below the packer lets the crew pressure up the tubing. That pressure drives pistons that set the packer. No pipe movement needed, which makes it popular in deviated wells and when running multiple packers.
- Wireline set. A setting tool on electric line fires a power charge that slowly builds gas pressure and strokes the packer to set. It gives precise depth control. The tubing is then run in and stung into the packer with a seal assembly.
After setting, the crew pressure tests the packer, usually by pressuring the annulus and watching for leaks.
Permanent vs Retrievable Packer: Which Is Better?
Neither is better across the board. The permanent vs retrievable packer choice comes down to how long the completion should last and how often the well will need work.
| Permanent packer | Retrievable packer | |
|---|---|---|
| Removal | Milled or drilled out | Released and pulled with the tubing |
| Pressure and temperature rating | Generally higher | Generally lower |
| Tubing connection | Seal assembly stings into a polished bore; tubing can be pulled and the packer stays | Usually made up directly in the tubing string |
| Cost | Higher upfront, cheap to keep | Lower upfront, can often be redressed and reused |
| Best for | Long-life, high-pressure or harsh wells, offshore | Wells expected to need regular workovers, temporary jobs |
A neat trick of permanent packers: since the tubing seals into the packer bore, the crew can pull the tubing for repairs and leave the packer in place as a barrier.
What Other Packer Types Will You Run Into?
Beyond the main families, you'll hear about a few specialty packers:
- Swell packers, with elements that swell when they contact oil or water. Common in open-hole horizontal completions for zone isolation.
- Inflatable packers, which expand with fluid pressure and can seal in irregular or oversized hole.
- Dual packers, with two bores for producing two zones through separate tubing strings.
- Seal-bore packers, which accept a seal assembly and allow some tubing movement.
- Test and treating packers, used temporarily for frac jobs, squeeze cementing or testing.
The SLB glossary entry on the packer gives the general definition, but in the field the service company's specification sheet is what you want in hand.
What Goes Wrong When a Packer Won't Hold?
These are the packer problems that show up most, with the likely cause and where to start. Your engineer's procedure and the company man's call come first on every one of these.
- Annulus pressure tracks tubing pressure. The packer isn't sealing, or the leak is in the tubing above it. Run a test to tell the two apart before blaming the packer.
- Packer won't set. It may be off depth, set in a bad spot of casing, or the setting sequence wasn't followed. Check the tally and the procedure.
- Packer sets early. Debris, tight spots or rough handling can trip a hydraulic or mechanical packer on the way in. Run speed and clean casing matter.
- Packer won't release. Common with retrievables that have sat for years in sand or scale. Try the release procedure carefully before jarring. It can turn into a fishing job.
- Tubing movement damage. Temperature and pressure swings make tubing grow and shrink. Engineers calculate this so the packer and seals can handle it.
A common mistake: setting a packer in a casing collar. Slips don't grip well there, and the elements may not seal. Use a collar log or careful tally to pick a spot in the body of a joint.
Where Does the Packer Sit in the Completion?
The packer usually sits just above the producing zone, with a short tail of tubing below it. Above it, the tubing runs to surface through landing nipples, maybe gas lift mandrels and a safety valve, all the way to the tubing hanger.
At the top, the tubing hangs in the wellhead and the tree controls the flow. Together, the packer at the bottom and the wellhead and Christmas tree at the top bracket the whole flow path, and they're the main barriers that keep a producing well under control.
Does Every Well Need a Completion Packer?
Not every well, but most flowing and high-pressure wells use a completion packer. It seals the tubing-casing annulus with slips and rubber elements, set mechanically, hydraulically or on wireline.
Permanent packers win on long life and high pressure. Retrievable packers win when the well will need regular work. Specialty packers handle open hole, dual zones and temporary jobs.
Many rod-pumped wells skip the packer so gas can vent up the annulus, which tells you the choice is always about the well in front of you. When you're picking or troubleshooting one, start with the procedure, the tally and a solid pressure test.