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The Science
The
basis of The PGDBK treatment is to have influence on the parameters
imbedded in the fundamental equation that governs the flow of oil and
gas in a reservoir rock (porous, permeable medium rock).
The
PGDBK is based on the effort to enhance the flow of oil and gas by
creating substantial effects on some of the above rock and fluid
properties that determines the flow of oil/gas in the reservoir.
The
cylindrical shaped powder charges are ignited almost instantaneously
along its length, in the well, creating excessive pressures and
temperature. These gases are quickly forced to expand. In the process
of expansion the gases first fill the void spaces around the wellbore
and overload the existing fractures. The pulsating action of the quick
gas overload builds up pressures to overcome the rock’s tensile
strength, creating several additional fractures of diverse
orientation. The vertical fractures tend to stay longer, as they are
least affected by overburden pressure and are assisted by the
confining pressure.
The
reaction is not an explosion and a blast does not occur as in some
perforation practices. Thus the formation is not crushed but rather
yields to the intrusion of gases into void spaces and channels with a
reaction that occurs on an order of magnitude slower than rocket
propellant.
The
mechanical impact of the combustion products on the formation is
manifested in formation of fractures, displacement of corrosion
products, products of chemical reactions, loose sand, clay particles
and solid deposits. The impact of this action is determined by the
amount of pressure created and the way the pressure behaves over time.
Note: The generators
do not contain explosives and a combustion blast does not occur.
Fractures
created go through an irreversible deformation process when the
following condition is met;
…
where Pw, is the wellbore pressure, Pf the
formation pressure, and Plr the lateral rock pressure.
Here, E1 and E2 are Young’s moduli for the
rocks in the case of loading and relief, respectively. Such fractures
once created cannot completely close after the generators have been
expended.
The
pulsating action of the pressured gases helps to erode the fracture
surfaces. It also cleans the perforations and pore channels through
the surge action of liquid and combustion products under high speed.
The eroded and plasticized wall is a distinguishing feature PGDBK
treatment has over conventional stimulation methods. Whereas hydraulic
fractures must be kept open with special propping agents, the PGDBK
plasticized walls stay open much longer without the need for proppants.
This
process is also accompanied by partial erosion of the fracture walls.
The continuous generation of the gases extends these fractures until
enough volume is created to reduce the gas pressure below the fracture
extension pressure.
After
the gas has been burnt out, a pressure back surge cleans out the
solids of sedimentation and filtration due to drilling, completion and
production practices. Other solids arising from the combustion of the
powdered charges are similarly washed back into the well. The amount
of gas to be generated is determined with the knowledge of the
fracture gradient and the transmissibility of the formation to the
gaseous products. This initial process substantially reduces the skin
effect of the wellbore area, s, and also increases the permeability,
k, of the wellbore region.
Another
advantage of the PGDBK powdered charge is its thermal effect.
Tremendous heat (930o F - 1300o F) is emitted in
this process acting in two ways. First, there is a reduction of the
viscosity of the fluid, m, in the wellbore region which mobilizes any
precipitation of paraffin, asphalt, resin, and other heavy
hydrocarbons. The thermal energy helps to keep the fractures, once
created, open for a longer period of time by plasticizing the walls of
the fractures. Such fractures stay open for a long time and do not
require propping agents, which would limit the number of
re-treatments, as occurs with hydraulic fracturing. The chemical
reaction reduces the surface tension between oil and water,
facilitating the relative permeability to oil.
Using
existing reservoir and well data, our mathematical models are used to
determine: a) the optimal amount of generators that are required; b)
the design of the tool configuration; c) predict the outcome and yield
probability of each treatment.
The
Technology
The
tools can be conveyed on a wireline or in tubing. The generators are
mounted in series and typically lowered on a wireline. Tubing
conveyance is used in setting the charges in horizontal wells. When
positioned at the determined depth in the well bore, the generators
are ignited almost instantaneously. They disintegrate completely since
they have no outer casing.
The
type of generator appropriate for a stimulation job is dependent on
the geological and reservoir conditions and also on the well
configuration. The number of generators required on a single run
assembly depends on the number of pay zones and their thickness.
Our
usual tools have temperature and pressure ratings up to 400oF
and 14,500 psi respectively. Well depths of at least 2000 feet are
desired, however, they can be used to depths of 22,000 feet. GEOTEC is
capable of handling other reservoirs that fall outside these desired
parameters with customized generators.
The
application of PGDBK technology is not limited to the stimulation of
oil and gas wells. There are other applications. It has been
successfully used to relieve methane from coal beds in Russia. Today
we are ready for the commercial exploitation of coal bed methane gases
that are found, in Australia and in the Midwest and Western basins of
the United States. This technology enables operators to book gas
reserves in several existing coal bed methane deposits.
Applications
Fracturing
and thermo-chemical treatment of near wellbore region using the
burning effect of powdered charges. This is a reliable application to
increase production capacities of oil and gas wells.
Advantages
of Method
- Uncomplicated
technology
- High
portability of tools
- No
operator charge for the technology application unless we are
successful
- Short
rig-up time and running operations
- Compatible
and may be used as a complement to other methods of stimulation
- May
be applied over a wide range of geological conditions
- Primary
well treatment ensures higher productivity and longer production
time before workover.
- Ideal
for wells in which packers cannot be used
- Thin
beds or beds with close oil and gas contacts
- Reservoirs
that are incompatible with external fluids
Results
of Uses
Average incremental oil production after PGDBK treatment – 800 tons
per year per well. (6,000 bbls/yr/well) from a single or repeat
treatments. In a single field in the Tyumen region, in Russia, an
incremental 330 million tons (2.4 billion barrels) was produced over 5
years.
Average incremental oil production after PGDBK treatment – 800 tons
per year per well. (6,000 bbls/yr/well) from a single or repeat
treatments. In a single field in the Tyumen region, in Russia, an
incremental 330 million tons (2.4 billion barrels) was produced over 5
years.
- Duration
of treatment effectiveness is from several months to several
years. In some specific fields, treatments have lasted for 5-7
years.
- Success
rate of PGDBK treatment; oil wells 70%; gas wells 90+%
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