COMPARISON SPT WITH INITIAL OPENING METHODS
Compare SPT is possible with the same category/group includes main methods of initial opening: different kinds of drilling, gun perforation, cumulative perforation, abrasive jet’s (point) perforation, and various types of slotted perforations (not with subsequent stimulation methods (acoustic, acid, air, cavitation, chemical, electrical, frequency, gas, hydraulic, laser, magnetic, plasma, pneumatic, pulse, resonance, shock, steam, stress (overstress), temperature, thermal, ultrasonic, vacuum, vibration, wave etc.). These methods cannot work by itself without opening methods. Compare possible by opening penetration area and by depth.
Graphical comparison of gun, shooting, jet, abrasive jetting and hydro-slotting perforation:
Graphical of comparing the depth and drainage zone (penetration):
Interpretation of “SPT is an alternative to hydraulic fracturing” is not quite correct, because here are compared of technologies totally different categories/groups. Hydraulic fracturing is not working itself without initial opening, so hydraulic fracturing cannot compete/compare with the methods of initial opening casing, cement and productive formation.
Hydraulic fracturing used in conjunction with these methods, or together with these methods, or not used at all (if there is a risk of flooding). Slotting Perforation conversely can be successfully used individually, or as combination with hydraulic fracturing, depending on the selected method of treatment after detailed geophysical analysis. Nevertheless, we will try to compare these two methods of different categories.
COMPARISON SPT WITH HYDRAULIC FRACTURING
Hydraulic fracturing (fracking) - hydraulically pressurized liquid made of water, sand, and chemicals - is known since 1947.
Hydraulic Fracturing is the most powerful method, creating very long cracks and micro cracks spread in the direction of the greatest fracture.
Fracturing relates to methods of opening the productive formation, but it can be applied only after one of the known methods of opening the casing:
shock-explosive: bullet (gun perforation) and cumulative perforation
unstressed: methods of point perforation and continuous opening
very large area of penetration into the productive formation
large productive inflow (especially in the initial stage)
process has practically no control;
process affects the other layers and zones;
cracks and micro cracks of large length extend the boundaries of producing formation and transferred to other layers
coefficient of efficiency sometimes reduced up to 20% (within productive formation), the remaining 80% are harmful
violation of the integrity of a producing formation
combining unwanted productive and non-productive reservoirs
generating unwanted flows
pulling up the water with subsequent flooding of the productive layer
reducing the life of the well
Coefficient of efficiency of hydraulic fracturing in shale’s or thinly interbedded layers, for example, is very low and financially not beneficial.
Slotting perforation - continuous moving jet slotting perforation - is known since 1975 (recommended for industrial use since 1980).
Slotting perforation is the most effective method of opening the casing, cement and productive formation.
For SPT process is used a special slotting perforation tool, that produces linear motion with constant velocity of abrasive cutting jets along the wellbore, and without moving the tubing from the surface.
SPT may be used as a completely independent method for opening casing, cement, productive formation, and receiving the productive inflows.
Also SPT can be used in combination with other methods.
ecologically safe, environmentally friendly (water and sand)
very long duration of effect (up to 10-15 years and more)
opportunity of using near the water reservoirs (impossible to make a hydraulic fracturing)
process is controlled (length and depth of slots)
process takes place within the productive formation, and not affects other layers and zones
large opening area, penetration depth is up to 5 feet
no detonation impact, no casing damage, no cement cracks, no clog-up the formation in borders
unloading the tangential circle stress conditions in the near wellbore zone up to 50-100%
increases the collecting properties in the near wellbore zone
increase of the drainage volume characteristics in more than 6 times
increase of permeability and accordingly increase the useful inflow up to 30-50%
opportunity to use in any wells and in any formations
process is quite complicated in the performance
Slotting perforation perfectly working in sandstones and carbonates, thinly interbedded formations, shale’s, etc.
Coefficient of efficiency of SPT in shale’s and thinly interbedded layers is very high.
SCOPE OF APPLICATION SLOTTING PERFORATION TECHNOLOGY
Slotting Perfpration Technology (SPT) is possible to use in oil, gas, injection and hydrogeological wells, in vertical and horizontal wells, in newly drilled and low productivity wells, in sand and carbonate formations, in shale and thinly interbedded layers.
In principle, SPT perforation can be used everywhere.
Consider some more examples.
Picture below shows example of thinly interbedded formation, and very similar to shale formation (side view +top view).
Top view shows only one limited layer, side view shows all other productive layers.
Start to open casing, cement and formation by traditional cumulative perforation. Receive several holes 2" diameter and less than a foot depth. Stress condition in the near wellbore zone do not allow productive inflow pass to the well, therefore necessary additional stimulation.
Apply traditional hydraulic fracturing. Fracturing spreads in the directions of most fractured and least resistance. After hydraulic fracturing left about half of unopened productive layers.
Hydro-slotting perforation opens all layers completely. No casing damage, no cement cracks, no clog-up the borders, plus unloading annular compressive stress conditions in the wellbore zone, and as a result, increase permeability, porosity, and productive inflow. Additional stimulation is not required.
MORE EXAMPLES OF USE SLOTTING PERFORATION TECHNOLOGY
The following example below shows the use of hydraulic fracturing and slotting perforation in horizontal well. SPT opens formation within the productive reservoir only, without mixing of productive and non-productive layers.
Consider one more example of use SPT in loose sands. Under the action of rock pressure and stress conditions in the near wellbore zone, quicksand is pressed against the well.
SPT unloads wellbore zone, and removes stress conditions. As a a result rock pressure becomes less, and sand stops to crumble.
Next, let `s talk about “breaking component”. As a result of initial opening casing by gun perforation, cumulative perforation, or abrasive jetting perforation, diameter holes does not exceed 2", and it does not change even when used hydraulic fracturing. Speed of equal quantity productive inflow through a small hole is always larger than through a large area (and for an equal amount of time). Small hole slows the productive inflow, thereby increasing the internal pressures, affecting and to loose sands.
SPT opens a much larger casing's surface, Productive inflow flows freely, without forming an additional internal pressures and without affecting to loose sands in the near wellbore zone. Sand stops to crumble.