In mass of variety articles, publications, conferences, exhibitions, forums, media and Internet, dedicated to oil and gas production increasing, impossible to find mentions or references to circular stress conditions, arising at any drilling in the near wellbore zone, reducing porosity and permeability, and preventing flow of oil or gas to the wellbore, which consequently reduces the useful product already on the opening stages. Also nobody ever considering the importance of initial opening casing, cement and productive formation, paying all the attention to stimulation of already opened productive formation only. This can be compared with work or repair in the house, produced through the keyhole. Accordingly, there is no information about only one technology - hydro-slotting perforation, which solves all the above problems.
For unloading circular stress conditions in the near wellbore zone necessary deep longitudinal slots. To create such slots necessary rectilinear constant movement of the cutting nozzles along the borehole.
Deep longitudinal slots redistribute circular stress conditions from the near-well zone to the ends of these slots. The effect occurs when the depth of the slots 2-3 ft. Accordingly, in the near-wellbore area circular stress conditions decrease. Accordingly improve reservoir properties, increase permeability/porosity, and accordingly increase the productive flow to the wellbore.
Speed of movement cutting nozzles along the borehole should be sufficient low for cutting casing, cement and formation.
There are a lot of designs and patents, implying opening casing by slots, but unfortunately this is far from reality, and  practical tests clearly confirms these facts.
Longitudinal slots is impossible to obtain by movement of tubing/coiled tubing from the surface. Having a natural frequency, stretching and a strong dependence on the smallest operating pressure's fluctuations, tubing/coiled tubing jumping along the casing. Movement should be created exactly in the place of cutting inside downhole.

Rectilinear constant movement of cutting nozzles impossible to obtain using only the compression spring, used in some designs and patents. Spring force varies depending on the length at some point, so get a uniform motion of cutting nozzles is impossible to trying change the working pressure. In Maxxwell tool spring is used only for return cutting nozzles into original (set-up/initial) position. and not affect to the creation of a straight continuous motion.
Longitudinal and deep slots is impossible to obtain by abrasive jetting perforation (spot motionless perforation). Numerous tests stubbornly shows, that the depth of hole is less than 1 foot. This is because reverse jets from the holes (including sand and rock) prevents direct jets (including sand)from the cutting nozzles, and does not allow the formation of depth. If the point jetting perforation has a small vibration, may be formed of the cavity (not a slots). The depth of jetting perforation is too small for unloading circular stress conditions in the near wellbore zone.
In slot perforation tool, using disc cutters, impossible to use an abrasive. Cutting only by working solution does not form depth, sufficient for unloading circular stress conditions in the near wellbore zone.
Unloading stress conditions in the near wellbore zone accordingly reduces rock pressure in the well area. This positive moment can be used in problematic wells to stop the loose sand (rock pressure to the loose sand will be removed). Large opened area in casing (long extended slot instead of small hole) also reduces the damaging effect of productive inflow pressure near the wellbore (at the same flow rate damaging effect through the big slots is much smaller, than through the small holes).
Any existing today stimulation techniques (acoustic, acid, air, cavitation, chemical, electrical, frequency,  gas, hydraulic, laser, magnetic, nanotechnology, plasma, pneumatic, pulse, resonance, shock, steam, stress, overstress, temperature, thermal, ultrasonic, vacuum, vibration, wave, etc.) directly dependent on the casing opening area (the more casing's open surface, the greater the effect and duration of effect). Hydraulic fractiring after hydro-slotting perforation passes very easily, for specified directory, and with much less pressure.
Traditional methods of opening the casing, cement and productive formation are not effective, therefore the development of natural resources happened and happening for only 20% (including malicious hydraulic fracturing). The other 80% (with damage to the environment) remains in the ground. The main negatives of some used technologies:
gun/cumulative perforation, some stimulation methods: impact, casing deformation, cement cracking, stable border formation (scale, melting, burnt), chemical/termal damage of productive formation, hydraulic fracturing: harmful/violation, affects to other layers and zones, combining unwanted productive and non-productive reservoirs, generating unwanted flows, pulling up the water with subsequent flooding of the productive layer, reducing well's life.



  • ecologically safe

  • environmentally friendly­ (used water and sand)

  • penetration depth is up to 5 foot (1.5 m)

  • opening (drainage) area per one linear meter up to 13 ft² (2 nozzles/slots), and 23 ft² (4 nozzles/slots)

  • accordingly opening a large casing's area

  • accordingly reduces “breaking component” due passage productive inflow, taking place in a small casing's holes (after gun perforation, cumulative perforation, or abrasive jetting perforation)

  • cutting speed is 50 min per linear foot in cased wells, and 30 min per linear foot in open holes

  • simultaneous cutting 2, 3, and 4 slots along the wellbore

  • no detonation impact

  • no casing damage

  • no cement cracks

  • no clog-up the formation borders

  • unloading the annular compressive stress conditions in the near wellbore zone up to 50-100 %

  • accordingly increase the permeability up to 30-50 %

  • accordingly increase the useful productive inflow up to 5-10 times

  • can be used in oil, gas, injection and hydro-geological wells

  • can be used in newly drilled and low productivity (low debit) wells

  • can be used in vertical and horizontal wells

  • can be performed with tubing and coiled tubing

  • can be used in any formation (sandstone, carbonates, shale’s, thinly interbedded, quicksand, etc.)

  • can be used near the water reservoirs (where impossible to use hydraulic fracturing)

  • extract more than 20 % additional oil from the layers with higher productivity

  • duration of effect 10-15 years

  • make an excellent geometry for subsequent fracturing (if necessary)