1. EERA SHALEGAS
Review of innovative stimulation
technologies
Andrzej Rogala
Anna Mykowska
Department of Chemical Technology
Faculty of Chemistry
Gdansk University of Technology

2. INTRODUCTION
• The aim of presentation is a short review of innovative
stimulation technologies to inspire the discussion between
industry and academia in the topic of environmental
friendly but also economically profitable technology
adequate to Polish shales.
• Two stages of stimulation will be considered. First is the
pre-completion stage of unconventional oil and gas
recovery and seconds are different methods of fracturing.

3. INTRODUCTION
Type of
fracturing
Description Divided into:
HYDRAULIC
FRACTURING
Liquid fluid use to fracture
the reservoir rock
• Water-based fluids
• Foam-based fluids
• Oil-based fluids
• Acid-based fluids
• Alcohol-based fluids –
• Emulsion-based fluids
• Cryogenic fluids (CO2, N2, He, etc.)
PNEUMATIC
FRACTURING
Gas (air or nitrogen) use
to fracture the reservoir
rock
FRACTURING
WITH
DYNAMIC
LOADING
Fluids are not used • Explosive fractuing
• Electric fracturing
OTHER
METHODS
• Thermal (cryogenic) fracturing
• Mechanical cutting of the shale formation
• Enhanced bacterial methanogenesis
• Heating of the rock mass
(Based on Gandossi, 2013)

4. • One of the most important advantage of
liquid CO2 fracturing is the elimination of
conditional formation damage normally
related with fracturing fluids, another one is
rapidly clean-up process and evaluation of
the well following the fracturing. CO2
fracturing keeps clays (smectite and illite)
stabilized and prevents metal leaching and
chemical interactions.
• In Canada were more than 1,200
accomplished with success only up to late
nineties. The technology was also used in
the USA for Devonian shale in East Kentucky
andWest Pennsylvania, Texas and Colorado.
It was observed that the average gas production in some wells was as much as five
times greater than in the case of production using as also used in the USA for
conventional HF treatments.
• The main problems related with carbon dioxide fracturing (also using nitrogen or
CO2/N2 mixture) are using special fracturing equiptment, CO2 transport in the liquid
state, and storage it in pressurized tanks.
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Carbon dioxide fracturing

5. Advantages
• increase the productivity of the well
• lower viscosity, density and surface tension of the fluid, which results in lower energy
consumption during fracturing
• full compatibility with reservoirs because LPG and hydrocarbons are mutually soluble
• smaller volume of chemicals added to the fracturing fluid
• sustainable, recyclable and more environmentally friendly then HF
• more dense than air, so there is no risk to air contamination and impact on global
warming
Disadvantages
• Investment costs are higher than for HF, because LPG is pumped into well at a very high
pressure, and after each fracturing it has to be liquefied again,
• LPG must be stored in costly pressurize tanks (water in HF is stored in non-pressure
tanks or in natural outdoor pools),
• LPG is explosive,
• LPG is more dense than air and fills up the ground cavities.
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LPG fracturing

6. Energized fluids
The flexibility of energized solutions allows hydraulic fracturing fluids to be mixed
according to the technological needs of unconventional reservoirs. They provide
more rapid and complete fluid recovery, help to clean without swabbing, and reduce
formation damage by minimizing the amount of aqueous fluids introduced into the
formation. In addition, many times energized solutions have superior proppant
transport properties without creating ultrahigh molecular weight polymer structures
and in the case of underpressured or depleted zones, provide enhanced energy for
hydrocarbon recovery.
Liquid leak-off increases water saturation, thereby decreasing the formation’s relative
permeability to gas. This may play a significant role in damaging gas reservoirs.
Energized solutions, however, use less water than conventional fracturing treatments
and provide energy for recovering induced fluids while decreasing the fluid leak-off
potential to minimize reservoir damage. Less water means less potential for clay
swelling, fines migration, liberating hydrogen sulfide, forming emulsion, and fluid
retention. Less damage enhances flow for effective flow back, reducing the time it
takes to move to production, while increasing overall production. Energized solutions
are ideal for reservoirs with low permeability, water sensitivity, underpressured or
depleted zones, or poor flow back caused by low pressure or strong capillary forces.
They also are used for refracturing wells where production has declined
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7. Energized fluids
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Averaged 10-Year Decline Analysis for Energized versus Nonenergized Frac Fluids

8. HiWAY – Flow Channel Fracturing Technique
Traditionally, efforts to enhance conductivity
have been directed toward improving flow
through a porous proppant pack. Strategies for
improving fracture production
• enhancing proppant roundness and strength
• lowering proppant crush and gel loadings
• improving gel breakers
The HiWAY technique changes the way
proppant fractures generate conductivity.

9. HiWAY – Flow Channel Fracturing Technique
Proppant is delivered in short high
frequency pulses to create stable
flow channels.

10. 10
Perforating technologies for
shale gas recovery
Basic
FracGun
PulseFrac
StressFrac
Improved
StimGun
GasGun
MP

11. FracGun
System of perforation engineered for wells requiring fracture stimulation, sand
control operations, and coalbed methane wells.
The main benefits of this system is increased safety from real-time
communication, optimized frac jobs and maximized production from the
flexibility of using custom-designed charges in different guns or intervals.
The guns are conveyed with wireline or slickline. A plug and shoot adapter makes
it possible to set a plug and shoot multiple guns on the same descent, saving
operating time.
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12. The StimGun perforator is composed of explosive charges encased in layer of solid
propellant and connected to detonator (Snider et al., 1998). There is a two stage
perforation. First, high explosive is ignited, making perforation. Next, propellant is
ignited, instantly producing a burst of high pressure gases. The resulting pressure
causes the formation of fractures. During this process, dislocations of the fractures
made by very fast increase of pressure in reservoir occurs but also blocking of
fractures results by fragments of rocks formed during fracturing. This allows free gas
flow in spite of no proppant application. The StimGun has been used also with great
success in a variety of applications ranging from both soft and hard rock perforating
and perforation breakdown, near well bore stimulation, acid stimulation and many
others. The technology is still being developed, by applying changes in charges
geometry, perforation tools, explosive ingredients and ignition systems, to reach
greater length of perforation (Snider and Zierolf, 2007). Unfortunately, at this stage
of development of these techniques, perforation hardly exceeds 0.7 m, reaching 1.6
m under some conditions whereas for comparison hydraulic fracturing achieves 100 -
200 m or longer.
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Stimgun

13. Stimgun
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14. 14
Gasgun

15. GasGun is the most advanced technology of pre-stimulation of reservoirs using solid
propellants. It is based on the ballistic U.S. military technology, designed to perforate
hydrocarbon bearing rocks. It is much more effective compared to other known
perforation technologies due to creation of multiple radial fractures, removing skin
and cleaning up the well-bore damaged by perforators, drilling fines, cement,
paraffin, mud cake, etc. The principle of operation of GasGun is based on three step
rocket fuel combustion and has no shape charges. Both, the perforation as well as
the fracturing are done by high pressure gases. In the first stage of StimGun, the
pressure increase is slower than in the case of high explosives use in the classical
methods, but
lasts longer and gives much better results. According to literature length of the
perforation can reach from 0.3 up to 3 m. Therefore, it is a potential method, which
is worth developing as an alternative to the hydraulic fracturing. Unfortunately, for
this moment, there is not enough data to determine how often a maximum range of
perforation can be achieved. In addition, the effectiveness of GasGun and StimGun
oscillates around 5 - 10 %, due to the ineffective flow control of gases, generated
during the perforation.
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Gasgun

16. Comparison of energetic and hydraulic fracturing
pressure
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17. Multistage Perforator
The overall concept of the project
Multistage Perforator is a combination of high explosive, shaped charges
and a progressively burning, solid propellant (solid rocket fuel which is rapidly burning,
accompanied by production of large amounts of heat and the considerable amount of gas
under high pressure) and a proppant (fine material added to the fracturing fluids used for
hydraulic fracturing, which, to prevent fracture closure, which in turn allows the gas
outflow from reservoir). It consists of two phases: detonation of high cumulative charges
and immediately after multistage propellant combustion. The additional low explosive
propellant is used in order to generate high pressure gas at very high rate to create multiple
fractures slippage radiating over 10 m in Sweet Spot from the well-bore, regardless shale
Least Principle Stress orientation and fracture - slippage type with secondary detonation
in the reservoir.
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18. Multistage Perforator
Multistage Perforator allow to:
 Increasing the efficiency of hydraulic fracturing through the creation of a network of
cracks already in the stage of of perforation of considerable range. Hydraulic
fracturing preceded this kind of perforation cover a larger volume of deposit, giving a
much higher gas production. The literature suggests that to achieve the larger fracture
net during of perforation translates to increased efficiency of the hydraulic fracturing
 The possibility of extracting gas from shale layers separated by layers of other rocks.
Polish gas-bearing shales are often separated by several meter thick layers of other
rocks which prevents hydraulic fracturing after the standard perforation. By applying
the proposed method, perforation tunnel is long enough to reach for shale which
allows you to perform hydraulic fracturing in this type of deposits
 Additional gas flow associated with a very effective fracturing of near borehole zone.
 Protection of perforations and preliminary fractures
- physical - by the presence of proppant in a stream of cumulative charges, entering
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into the reservoir and keep fractures open
- chemical - additives for solid rocket fuel and combustion products ensure the
stability of the reservoir until fracturing

19. 19
Classic perforators vs Mulstistage perforator

20. 20
Classic perforators vs Mulstistage perforator

21. Thank you for your attention
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