Intensifier

An intensifier is a downhole tool that sits in the drillstring directly above a drilling jar and roughly doubles the impact force the jar delivers when it fires. Drilling jars are used to free stuck pipe, fishing tools, or stuck wireline equipment by delivering a sudden hammer-like blow up or down the string. The intensifier stores spring-loaded energy as the operator pulls or sets weight on the string, then releases all of it at the exact instant the jar trips. The combined system hits harder than the jar alone, which is often the difference between freeing the stuck equipment and giving up.

Key Takeaways

An intensifier is run directly above a drilling jar in the bottom-hole assembly. Its job is to multiply the jar's impact when the jar fires by adding stored spring energy to the strike.
A typical intensifier multiplies the jar's effective impact force by 2x to 5x. Surface pull of 50,000 pounds-force (222 kN) on a stuck string can deliver 250,000 pounds-force of jarring energy at the stuck point with the right intensifier-and-jar combination.
Intensifiers are most often deployed during fishing operations to free stuck drillpipe, stuck packers, parted drillstrings, or lost wireline tools. Without an intensifier, the same jar might lack the energy to break the stuck connection or free the stuck object.
The two main intensifier types are mechanical (using a coil or disc spring) and hydraulic (using a fluid-charged piston). Mechanical is simpler and more reliable in cold or shallow wells. Hydraulic delivers more controlled energy in deep, hot wells where mechanical springs lose performance.
Stuck pipe is one of the most expensive non-productive-time events on a drilling rig. A stuck drillstring on a deep horizontal well can cost CAD 250,000 to CAD 2.5 million per incident depending on depth, formation, and resolution time. The few thousand dollars in rental cost for an intensifier is insurance against a much larger loss.

Fast Facts

The largest hydraulic intensifiers used on deepwater rigs in the Gulf of Mexico, the Norwegian Continental Shelf, and Australia's North West Shelf store more than 100,000 pounds-force (445 kN) of preload energy in a single charged piston. When that piston releases at the instant the jar fires, the combined strike on the stuck point can exceed 400,000 pounds-force in a few milliseconds. That is roughly the impact of a small car hitting a wall at highway speed, delivered three miles below the rig floor.

What Is an Intensifier in Oil and Gas, Explained

Picture a slingshot. The further you pull the rubber band back, the harder the rock flies when you let go. The rock leaves with more energy than your hand alone could throw it because the rubber band stored your pulling effort and then released it all at once. An intensifier works the same way for a drilling jar.

A drilling jar by itself is a tool that creates a sudden impact in the drillstring. The driller pulls or pushes on the string from surface, and at a preset load the jar trips and releases that stored mechanical energy as a hammer blow up or down the pipe. That blow travels down the string and hits whatever is stuck. Sometimes it works. Sometimes the jar's blow alone is not strong enough.

The intensifier is run in the bottom-hole assembly directly above the jar. As the driller takes weight up or sets weight down to trigger the jar, the intensifier compresses (mechanical type) or pressurizes (hydraulic type) and stores that energy in a spring or fluid charge. At the millisecond the jar fires, the intensifier releases all of its stored energy at the same time. The blow that hits the stuck point is the jar's energy plus the intensifier's stored energy combined.

Where Intensifiers Are Used

The most common application is fishing: the work of recovering equipment that has separated from the drillstring or got stuck downhole. A drillpipe joint that fails. A bottom-hole assembly that twists off. A stuck packer that will not release. A wireline tool that broke free of its cable. The recovery starts with running a fishing tool to grab the stuck object, then jarring on it to break it free. If the jar alone cannot deliver enough force, the intensifier is what makes the operation work.

Intensifiers are also routinely run on every well as preventive insurance. A drilling crew that gets stuck without a jar-and-intensifier combination already in the hole has to trip the entire string out, run the jarring tools, and trip back in. That round trip can take 24 to 48 hours on a deep well at full rig day rates. Most operators specify the intensifier as standard equipment in the BHA on any well where stuck pipe is a meaningful risk: deepwater wells, deviated wells, salt sections, and reactive shale formations.

An intensifier is also called a jar intensifier or jar booster. The closely related tool that performs the same energy-storage function but on a different mechanical principle is called an accelerator. Some operators use the names interchangeably; the strict distinction is that accelerators store kinetic energy in a moving mass while intensifiers store potential energy in a spring or fluid charge. Related terms include drilling jar (the impact-delivering tool that the intensifier sits directly above and multiplies; available as mechanical, hydraulic, or hydromechanical types depending on the trip mechanism), bottom-hole assembly (the lower portion of the drillstring containing the bit, drill collars, stabilizers, and any specialty tools including the jar and intensifier), fishing (the wellbore operation of retrieving objects that are stuck downhole or that have separated from the drillstring; the primary use case for intensifiers), stuck pipe (drillpipe or BHA components that cannot be moved up, down, or rotated; the problem the jar-intensifier system is designed to solve, with mechanical sticking responsive to jarring while differential sticking often is not), and accelerator (a closely related downhole tool that stores kinetic energy from a moving mass to multiply jar impact; an alternative to the intensifier with similar function but different mechanics).

Why a CAD 10,000 Tool Saves a CAD 1.5 Million Fishing Job

A drilling crew on a deep horizontal well in the Montney Formation in northeast British Columbia has a drillstring stuck at 3,475 metres (11,400 feet). The pipe will rotate but will not move axially, so they diagnose mechanical sticking, not differential sticking. They start jarring up with the hydraulic jar that was pre-installed in the BHA. After 40 minutes of jarring at increasing pull, the string still will not budge.

The intensifier above the jar has been adding stored energy to every blow the entire time. The driller raises the pull tension one more notch. At 95,000 pounds of overpull, the jar fires and the intensifier releases its preloaded energy at the same instant. The combined strike is more than 280,000 pounds of impact at the stuck point. The string lifts free on the next pickup.

Total non-productive time: 90 minutes. Total cost: about CAD 22,000 in rig time. Without the intensifier, the same string almost certainly would have stayed stuck through that round of jarring, leading to a back-off operation, a fishing trip, and several days of lost progress. The fishing job alone would have run CAD 1 million to CAD 1.5 million on a well of that depth and complexity. The intensifier itself adds CAD 7,000 to CAD 14,000 to the BHA rental cost for the well. The math is so one-sided that most operators specify the tool as standard equipment without a second thought.