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Underground slot perforation tool (SPT), regardless of the design, consists of the following mandatory parts:

  Perforator with nozzles

  Return unit

  Hydraulic unit

External dimensions of body SPT tool are determined by the most commonly used well's standards. In North America the most common ID well casings 4.5" and 5.5".

Internal design and construction of SPT tool for vertical and horizontal wells are different.


Currently Maxxwell Production is using SPT tool by patent US 8863823 (Granted October 21, 2014), which replaced the previous model by patent US 8240369 (Granted August 14, 2012). Tool is constantly being improved.

Hydro-slotting perforation tool

HYDRAULIC UNITS • Patent US 8863823 •

Hydraulic Units (Maxxwell Tool)

Hydraulic slot perforation unit is a main part of SPT tool for performing slotting perforation process.
At applied working fluid pressure hydraulic unit creates a forward rectilinear motion of the perforator with nozzles (along the borehole).
Speed of movement defines the cutting depth. Speed is constant, but depends on the pressure  and temperature of working fluid.
Hydraulic unit is a sealed and closed system, able to change its internal volume depending on exposure of external hydro-static pressure at different depths, to prevent an explosion.

RETURN UNITS • Patent US 8863823 •


PERFORATORS • Patent US 8863823 •

Return Units (Maxxwell Tool)

Return unit is a part of SPT tool. Return unit providing a return the perforator with nozzles to the original (start-up) position, when cut operating pressure.
Return unit also provides the following functions:

Prevents circular rotation of perforator with nozzles or

Conversely, allowed freely rotate of perforator with nozzles

Defines the direction of cutting slots (directly, along the borehole, or angled, by spiral)

Prevents force impact on the hydraulic block at accidental lowering perforator on the on ground

Perforators (Maxxwell Tool)

Perforators is a part of SPT tool, performs rectilinear translational movement along the borehole, thereby providing cutting slots by cutting jets from nozzles.


In the perforator working fluid changes its direction, and flows into the nozzles. Also perforator prevents the nozzles from shocks and touches the walls of the well.


Perforators vary in design, type, form, destination, number of nozzles, number of stiffened ribs, for different well designs, diameter, tasks, etc.


Exist ergonomic, streamlined, multiple use, for vertical and horizontal wells, self-oriented, swiveling, etc.


NOZZLES • Patent US 8863823 •

Nozzles (Maxxwell Tool)

Nozzles for SPT are made ​​from high quality tungsten mixture of carbide, tungsten, corundum, technical diamond grit and special additives in a definite proportion.

Nozzles must to meet all  requirements of SPT technological process:  lasting of work,  resistance to high temperature, high pressure, impacts, crumbling and have a high hardness.

The nozzles are of different design and size, depending on the form of nozzle holders and perforators, in which they are used.

COMPENSATORS • Patent US 8863823 •

Compensators (Maxxwell Tool)

In some rare cases, and using a special technique of executionfor, for cutting short slots along the borehole in vertical wells, possible to use special compensators.


Compensators simulate forward movement of perforator with nozzles, and allow to create a short slots in casing, cement and formation.

ADAPTERS • Patent US 8863823 •

Adapters (Maxxwell Tool)

Adapters is element for connecting  HSP tool with standard tubing or coiled tubing. 


Adapters also can perform other functions, as pressure testing of tubing or coiled tubing.


Nonmagnetic adapters, visible at logging, can be used at correlate the initial installation of cutting interval.


Also exist elongated adapters, smoothing fluctuations of supply working fluid pressure. In this case adapter partially function as compensator.


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