Transcript Overbalanced Perforating

Propellant Completions
Principles - HEGF, etc.
• The pressure used for fracturing is provided
by the rapid combustion (burning) of
propellant in the wellbore, which generates
large quantities of CO2 gas. When this
pressure exceeds the in-situ stresses, the
rock fails in tension, and the high velocity
gasses erode the face of the subsequent
fractures. The operation may be conducted in
both open and cased wellbores.
Tradenames
• The technique is known by several generic names,
such as Dynamic Gas Pulse Loading® (ServoDynamics), High Energy Gas Frac (Sandia National
Laboratories), and Controlled Pulse Fracturing (Mobil
Research and Development Corporation).
• Stimgun and Stimtube (MOC)
Explosive Stimulation
(Well Shooting)
• Liquid or solidified nitroglycerin - since 1800s.
• The intended to fracture or "rubbilize" the rock
to alter permeability near the wellbore.
• Brief, extremely high and compressive pressure
pulse, or shock wave is generated, which far
exceeds the tensile strength of the formation
rock.
Explosive Stimulation
(Well Shooting)
• The high pressures of the detonation cause the
rock to yield and compact.
• After the stress wave passes, the rock unloads
elastically, leaving an enlarged, deformed
wellbore, a zone of compacted rock and a
region of greater compressive stress. This
crushed region contains a substantial quantity
of fines, which reduce permeability and
productivity around the wellbore.
Propellant Technology
• Explosives and propellants have similar
energy contents, but different
ingredients.
• Both release energy as they "burn",
and the type of energy released is
directly related to the rate at which
they chemically convert into gas.
• For inducing multiple, radial fractures,
the rate at which the borehole is
pressurized is the controlling factor.
• Peak pressure is important, but
secondary.
Detonation
(microseconds)
Pressure
Overbalance
Propellant
(milliseconds)
Hydraulic Fracture
(10s to 100s of seconds)
Time
Principles
• A burst of high-pressure gas or a fluid "spear" is
driven into the perforation at extremely high
velocities - to remove crushed-zone damage and to
create short fractures in the formation.
• Trade literature suggests that this can result in
negative skin.
• "Cleaner perfs mean reduced treating pressures - 500
to 1,300 psi lower than for similar wells perforated in
an underbalanced condition.
• Significantly lower treating pressures mean
significantly lower treatment costs."
StimgunTM
• Propellant sleeve over a conventional assembly.
• When the guns detonated, the propellant sleeve
is ignited instantly, producing a burst of highpressure gas.
• This gas enters the perforations, breaking
through any damage around the tunnel,
creating fractures in the formation.
• As the gas pressure in the wellbore dissipates,
the gas in the formation surges into the
wellbore carrying with it damaging fines.
StimGun, StimTube and POWRPERF are
service marks/trademarks of Marathon Oil Company
The StimGun™ assembly used in the
Mara-Stim process
• The propellant is ignited by
the pressure and shock
wave of the shaped
charges as they penetrate
the gun, casing and
formation.
• The propellant sleeve, on
initial inspection, would
appear similar to a piece of
PVC pipe held in position
by slightly larger end subs
on the carrier.
The Players (Stimgun)
• Marathon Oil Company
• Owen Oil Tools, Inc. (manufactures the
StimGun™ and the StimTube™ Tool)
• HTH Technical Services, Inc.
• Computalog Ltd.
• Halliburton Energy Services, Inc.
• Baker-Atlas
The StimTube™ Tool
• Same solid propellant
technology as StimGun™ tool
• StimTube™ tool creates a
surge of high-pressure gas
downhole. The surge can
clean up damage and initiate
fractures in perforated cased
and open hole wells.
• Runs on standard tubingconveyed, electric line or
slickline equipment.
The StimTube™ Tool
• Positioned across the formation of interest.
• Ignition over the tool's entire length. The
burn, from inside out, produces constantly
increasing gas volumes.
• Fractures are initiated.
• As wellbore pressure declines after the burn,
gas surges back out of the formation,
carrying damaging fines with it, providing
enhanced communication between the
formation and wellbore.
The PerfStim™ Process
• Halliburton’s extreme overbalanced technique
• In the PerfStim™ process, an extreme
overbalanced condition is created - pressure
gradients of at least 1.4 psi/ft (31 kPa/m).
• A small volume (usually no more than a 300ft column) of non-damaging fluid is placed
above the gun, then pressured with nitrogen.
If needed, a liquid can be bullheaded on top
of the nitrogen column.
The PerfConSM Process
• Extreme overbalance technology to perforate
and inject a Halliburton sand consolidation
resin
• When the guns fire, the resin surges into the
formation around the perforations.
• Pump catalyst to set the resin.
• The initial high-pressure, high-flow-rate surge
removes debris from the perforation tunnel
and crush zone.
• Can be used through existing perforations.
POWRPERFSM
• The POWRPERFSM process incorporates an
agent that scours the perforations to remove
the crushed zone damage, often producing
negative skin.
KISS ™ Charge vs. Big-Hole Charge
• Designed to just penetrate the formation while
the high pressure gas breaks through the
crushed zone in the tunnel and creates fractures
in the formation.
– KISS charges created holes in the casing that
were equal to or larger in diameter than those
created by conventional big-hole perforating
charges.
– Perforation depth was reduced, so there was
far less damage to the formation as well as a
significantly reduced crushed zone (less than
one-third of a conventional big-hole charge).
Servo-Dynamics
DGPL®/STRESSFRAC®
–
–
–
–
Produces fractures extending several feet.
Restricts vertical fracture growth
Multiple zones without the need for mechanical isolation.
under non-damaging fluids, such as liquid CO2, methanol,
diesel fuel, kerosene distillates, or other similar liquids
– multiple fractures which intercept and connect with the
natural fracture pattern
– in single run lengths up to 304.80 m (1,000 ft.)
– in horizontal wells in open hole, pre-perforated liners,
cemented and perforated casing. tubing conveyed, with or
without packers, and with or without tubing anchors