Note: Descriptions are shown in the official language in which they were submitted.
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INHIBITING FORMATION FACE FAILURE IN OIL AND GAS WELLS
BACKGROUND
[002] The invention generally relates to inhibiting formation face failure in
oil
and gas wells.
[003] In well drilling, artificial lift describes the process for using
artificial means
to increase the flow of liquids, such as crude oil or water, to the surface of
a production
well. Artificial lift is usually provided by providing a pressure gradient
within the
reservoir, thereby encouraging the flow of reservoir fluids to the producing
well bore.
[004] Artificial lift can be provided by an electric submersible pump (ESP).
An
electric submersible pump has a hermetically sealed motor close-coupled to the
pump
body. The pump assembly is submerged in the reservoir fluid. Reservoir fluids
are then
drawn into the electric submersible pump, and are pumped up the well bore for
collection. The electric submersible pump can provide a significant lifting
force since it
does not rely on external air pressure to lift the fluid.
[005] Artificial lift is provided in many working reservoirs by electric
submersible pumps, lifting from shale inter-bedded sandstone sequence, such as
that
found in the Forties Field of the North Sea. The working life of the electric
submersible
pump can be adversely affected in fields, such as the Forties Field where
sandface
failures are common. In these types of fields, run times for the electric
submersible
pumps have fanged from several days, to several years, depending on the
frequency of
the sandface failures.
[006] Pump failure is sometimes attributed to electrical insulation failure,
such as
the cables, windings, and ingress of fluids to the electrical motor. However,
more often,
electric submersible pumps fail due to mechanical failure of the pump, such as
a seized
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shaft, seal failure, or pack off of the pump impellors. These mechanical
failures
are often caused by the operating environment. For example, solid contaminants
within the flow stream may cause abrasion of the mechanical pump parts. This
abrasion may result in a failure of the pump. Failure of the sandface is a
major
producer of these contaminants.
SUMMARY
[006a] According to one aspect of the present invention, there is provided a
method comprising: running a string into a well bore, the well bore extending
at
least partially through a non-producing layer, and a hydrocarbon formation
layer;
and inhibiting formation face failure, comprising: communicating a proppant
into
the well bore via the string until a well bore pressure exceeds a first
formation
stress of the non-producing layer, causing a fracture to form in the non-
producing
layer; and communicating the proppant into the fracture to create a barrier
layer
between the well bore and the non-producing layer to prevent formation face
failure due to reduction of pressure in the hydrocarbon formation layer caused
by
production.
[006b] According to another aspect of the present invention, there is
provided a method usable with a well, comprising: determining an intervention
for
the well at the well site; applying the intervention to the well; and managing
the
well site, comprising: running a string into a well bore of the well, the well
bore at
least partially extending through a non-producing layer, and a hydrocarbon
formation layer; and inhibiting formation face failure, comprising:
communicating a
proppant into the well bore via the string until a well bore pressure exceeds
a first
formation stress of the non-producing layer, causing a fracture to form in the
non-
producing layer; and communicating the proppant into the fracture to create a
barrier layer between the well bore and the non-producing layer to prevent
formation face failure due to reduction of pressure in the hydrocarbon
formation
layer caused by production.
[007] In an embodiment of the invention, a technique includes running a
string into a well bore and inhibiting formation face failure. The well bore
extends
at least partially through a non-producing layer and a hydrocarbon formation
layer.
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The inhibiting of the formation face failure includes communicating a proppant
into
the well bore via the string until a well bore pressure exceeds a first
formation
stress of the non-producing layer, which causes a fracture to form in the non-
producing layer, and communicating the proppant into the fracture to create a
barrier layer to prevent the formation face failure.
[008] In another embodiment of the invention, a technique to manage a
well site includes determining an intervention for a well at the well site and
applying the intervention to the well. The technique includes managing the
well
site, including running a string into a well bore of the well. The well bore
at least
partially extends through a non-producing layer and a hydrocarbon formation
layer. The management of the well site includes inhibiting formation face
failure,
which includes communicating a proppant into the well bore via the string
until a
well bore pressure exceeds a first formation stress of the non-producing
layer,
causing a fracture to form in the non-producing layer, and communicating the
proppant into the fracture to create a barrier layer to prevent the formation
face
failure.
[009] In yet another embodiment of the invention, a system includes a well
bore and a barrier layer that contains a proppant. The well bore extends
through
a hydrocarbon formation layer and a non-producing layer. The barrier layer is
disposed between the well bore and the non-producing layer and inhibits
formation face failure.
[0010] Advantages and other features of the invention will become apparent
from the following drawing, description and claims.
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BRIEF DESCRIPTION OF THE DRAWING
[0011] Fig. I is a pictorial representation of a network data processing
system
according to an embodiment of the invention.
[0012] Fig. 2 is a diagram of an offshore oil and gas platform connected to a
hydrocarbon producing well according to an embodiment of the invention.
[0013] Fig. 3 is a schematic diagram of a drill string apparatus used to
provide
fracture packing intervention to areas surrounding a perforated well bore
according to an
embodiment of the invention.
[0014] Fig. 4 is a table illustrating a classifying of elastic rocks according
to the
diameter of individual grains of sediment within the rock.
[0015] Fig. 5 is a schematic diagram of a fracture packing intervention of the
prior
art.
[0016] Fig. 6 is a cross sectional illustration of a pressure profile
according to an
embodiment of the invention.
[0017] Fig. 7 is a schematic diagram of a fracture packing intervention
according
to an embodiment of the invention.
[0018] Fig. 8 is a flow diagram of a fracture packing technique according to
an
embodiment of the invention.
[0019] Fig. 9 is a flow diagram of a well site according to an embodiment of
the
invention.
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DETAILED DESCRIPTION
[0020] With reference now to Fig. 1, a pictorial representation of a network
data
processing system is depicted in which a preferred embodiment of the present
invention
may be implemented. In this example, network data processing system 100 is a
network
of computing devices in which different embodiments of the present invention
may be
implemented. Network data processing system 100 in these examples is used to
collect
data, analyze data, and make decisions with respect to the life cycle of
different natural
resources, such as oil and gas. Different stages in this life cycle include
exploration,
appraisal, reservoir development, production decline, and abandonment of the
reservoir.
In these different phases, network data processing system 100 is used to make
decisions
to properly allocate resources to assure that the reservoir meets its
production potential.
[0021] Network data processing system 100 includes network 102, which is a
medium used to provide communications links between various devices and
computers in
communication with each other within network data processing system 100.
Network
102 may include connections, such as wire, wireless communications links, or
fiber optic
cables. The data could even be delivered by hand with the data being stored on
a storage
device, such as a hard disk drive, DVD, or flash memory.
[0022] In this depicted example, well sites 104, 106, 108, and 110 have
computers
or other computing devices that produce data regarding wells located at these
well sites.
In these examples, well sites 104, 106, 108, and 110 are located in geographic
region b.
This geographic region is a single reservoir in these examples. Of course,
these well sites
may be distributed across diverse geographic regions and/or over multiple
reservoirs,
depending on the particular implementation. These well sites may be well sites
that are
being developed or ones in which production are occurring. In these examples,
well sites
104 and 106 have wired communications links 114 and 116 to network 102. Well
sites
108 and 110 have wireless communications links 118 and 120 to network 102.
[0023] Analysis center 122 is a location at which data processing systems,
such as
servers are located to process data collected from well sites 104, 106, 108,
and 110. Of
course, depending on the particular implementation, multiple analysis centers
may be
present. These analysis centers may be, for example, at an office or an on-
site in
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geographic region 112 depending on the particular implementation. In these
illustrative
embodiments, analysis center 122 analyzes data from well sites 104, 106, 108,
and 110
using processes for different embodiments of the present invention.
[0024] In the depicted example, network data processing system 100 is the
Internet
with network 102 representing a worldwide collection of networks and gateways
that use
the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of
protocols to
communicate with one another. At the heart of the Internet is a backbone of
high-speed
data communication lines between major nodes or host computers, consisting of
thousands of commercial, governmental, educational and other computer systems
that
route data and messages. Of course, network data processing system 100 also
may be
implemented as a number of different types of networks, such as for example,
an intranet,
a local area network (LAN), or a wide area network (WAN). Fig. 1 is intended
as an
example, and not as an architectural limitation for different embodiments.
[0025] Referring now to Fig. 2, an exemplary well site 200 includes an oil and
gas
platform 210 and well sites 104, 106, 108, and 110. Although a subsea well is
specifically described below for purposes of example, it is understood that
the systems
and techniques that are described herein may likewise be applied to land-based
wells, in
accordance with other embodiments of the invention.
[0026] Platform 210 is positioned over hydrocarbon formation 212. Hydrocarbon
formation 212 is a formation of sandstone, or other permeable material,
containing
hydrocarbons, such as oil and natural gas, interspersed within the rock
matrix.
[0027] Derrick 214 is used to install pipe string 216 from integrated deck 218
to
well head 220 situated on sea floor 222. In addition to installing pipe string
216, derrick
214 can also be used to convey drill string apparatuses 223 down pipe string
216 and
within well bore 228.
[0028] Drill string apparatuses 223, including monitoring and intervention
type
apparatuses, can be used to measure properties of hydrocarbon formation 212,
as well as
non-producing layer 224 and non-producing layer 226 adjacent to hydrocarbon
formation
212 and surrounding well bore 228. Drill string apparatuses 223 may also be
used to
provide intervention to well bore 228 and hydrocarbon formation 212. In
undersea
operations, such as shown in well site 200, non-producing layer 224 and non-
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layer 226 may be largely formed from shale or siltstone. An intervention is a
remedial
measure applied to a well bore, which is aimed at improving production
therein.
[0029] Well bore 228 extends from wellhead 220, below sea floor 222. Well bore
228 traverses through non-producing layer 224 and into hydrocarbon formation
212.
Depending on the particular embodiment of the invention, well bore 228 may or
may not
be lined with a metal or cement casing to support well bore 228 and thus,
stabilize the
recently drilled formation.
[0030] Perforation 230 is punctured through well bore 228, including any
casing
therein, and extends from well bore 228 into hydrocarbon formation 212.
Perforation
230 is a series of tunnels that are formed by (as non-limiting examples)
punching, jetting
or shaped-charge jets. The tunnels extend though the casing or liner of well
bore 228 and
into hydrocarbon formation 212 to hydraulically connect well bore 228 to
hydrocarbon
formation 212. Perforation 230 allows hydrocarbons from hydrocarbon formation
212 to
flow into well bore 228. Perforation 230 also provides a conduit from well
bore 228 to
provide any intervention, such as hydraulic fracturing, gravel packing, or
fracturing
packing to hydrocarbon formation 212.
[0031] Perforation 230 may be formed in a prior downhole run using a shaped
charge perforating gun, a jetting tool or any other type of perforating
device.
[0032] Referring now to Fig. 3, a diagram illustrating an exemplary drill
string
apparatus used to provide fracture packing intervention to areas surrounding
the
perforated well bore is shown according to an embodiment of the invention.
Drill string
apparatus 300 can be a drill string apparatus, such as drill string apparatus
223 of Fig. 2,
to provide fracture packing intervention to a hydrocarbon formation, such as
hydrocarbon
formation 212 of Fig. 2. Drill string apparatus 300 includes one or more
assemblies for
performing perforation or packing of an intervention in the well bore. As a
non-limiting
example, drill string apparatus 300 may be a QUANTUM gravel pack system,
available
from Schlumberger Limited.
[0033] As a non-limiting example, the drill string apparatus 300 may be run
downhole in the well bore 228 by a wire line 310, which may include a single
strand,
multiple strands, or braided strands of metal wire. Wire line 310 is capable
of conducting
an electrical circuit to drill string apparatus 300 and is also capable of
providing a
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communications pathway between drill string apparatus 300 and any monitoring
computers receiving the well bore data. It is noted that the wire line 310 is
only one
example of a conveyance device, as another type of conveyance device (such as
jointed
tubing, a slickline, coiled tubing, etc., as non-limiting examples) may be
used to run the
drill string 300 downhole, in accordance with other embodiments of the
invention.
[0034] Tool controller 314 provides instructions received from the control
computer to other components of formation evaluation tool 300. Tool controller
314 can
be a data processing system, including software instructions, which provides
control
instructions to drill string apparatus 300.
[0035] Fluid pump 316 pumps fluid into the bore hole and into fluid sample
chambers 318 and formation isolation packers 322. Fluid pump 316 may also
include
valves or ports that may be opened and closed from the surface of drill string
apparatus
300 in order to introduce fluids into fluid sample chambers 318 or formation
isolation
packers 322.
[0036] Formation isolation packers 322 are inflatable annular rings disposed
around the outer surface of drill string apparatus 300. Formation isolation
packers 322
are adapted for sealingly engaging the well bore. Formation isolation packers
322 are
typically made of a thermoplastic elastomer, such as rubber. Fluid sample
chambers 318
provide a channel by which formation fluids can be pumped from fluid pump 316
into the
interior of formation isolation packers 322, causing formation isolation
packers 322 to
inflate and engage the sides of the well bore. Formation isolation packers 322
thus
provide a seal such that the conditions in an area between formation isolation
packers 322
can be changed, for instance by altering the pressure within this area,
relative to the
conditions elsewhere in the well bore.
[0037] During a hydraulic fracturing process, the pressure in a well bore is
increased by the pumping of fluids into the well bore. The fluid can be any
number of
fluids, ranging from water to gels, foams, nitrogen, carbon dioxide or even
air in some
cases. When the pressure within the well bore exceeds the formation stress of
the
formation, a fracture within the formation is caused to open, thereby
relieving some of
the pressure. The fracture extends away from the well bore according to the
natural
stresses within the formation. The fracture can be maintained in an opened
position by
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pumping proppant into the opened fracture to prevent closing of the fracture
when
pressure within the well bore is reduced. A proppant is a porous media, such
as sand, that
is pumped into a fracture in order to maintain the fracture in an expanded
state when the
pressure in the well bore is decreased.
[0038] Proppants are dissolved or otherwise carried in specially engineered
fluids
pumped at high pressure and rate into the reservoir interval to be treated.
The proppant,
which is commonly sieved round sand, is carried into the fracture. This sand
is chosen to
be higher in permeability than the surrounding formation and the propped
hydraulic
fracture then becomes a high permeability conduit through which the formation
fluids can
be produced back to the well. Various types of proppants are used, including
sand, resin-
coated sand, and man-made ceramics depending on the type of permeability or
grain
strength needed.
[0039] When formation isolation packers 322 are set into place, drill string
apparatus 300 provides fracturing and fracture packing to the hydrocarbon
formation,
such as hydrocarbon formation 212 of Fig. 2. The proppant slurry is pumped
into the
casing or screen annulus via a circulation housing located in the extension
below the
packer.
[0040] In a fracture packing operation, the proppant slurry is pumped into the
well
bore until the pressure within the well bore exceeds the formation stress.
When a fracture
within the formation is caused to open, the proppant slurry is forced into the
formation.
The proppant filled fracture facilitates flow of hydrocarbons from the
formation into the
well bore.
[0041] Referring now to Fig. 4, a table is shown classifying elastic rocks
according
to the diameter of individual grains of sediment within the rock. In table
400, size ranges
define limits of classes that are given names in the Wentworth scale to
classify the elastic
rocks and formations made therefrom.
[0042] According to the Wentworth scale depicted in Fig. 4, sandstone 410
typically has a particle size of from about 0.0063 millimeters to about 1.0
millimeters in
diameter. Siltstones 420 and shales on the other hand typically have a
particle size of
from about 3.9 micrometers (0.0004 millimeters) to about 63 micrometers
(0.0063
millimeters). The smaller particle size in the siltstone and shale result in
less interstitial
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space between neighboring particles. The limited interstitial space
effectively precludes
any hydrocarbons from being located within the siltstone and shale. Larger
sandstone
particles result in larger interstitial spaces, in which hydrocarbons can be
found.
[0043] Referring now to Fig. 5, a schematic diagram of a fracture packing
intervention applied to a well bore is shown according to the prior art. Well
bore 510,
which can be well bore 228 of Fig. 2, extends through hydrocarbon formation
512, which
can be hydrocarbon formation 212 of Fig. 2. Perforation 514 may be perforation
230 of
Fig. 2. This perforation connects well bore 510 to hydrocarbon formation 512.
[0044] Proppant slurry 516 is pumped into well bore 510 from a drill string
apparatus, such as drill string apparatus 300 of Fig. 3. Proppant slurry 516
is pumped
into well bore 510 until the pressure within well bore 510 exceeds the
formation stress.
When a fracture within the formation opens or occurs, the proppant slurry is
forced into
the formation through the fracture. The proppant filled fracture facilitates
flow of
hydrocarbons from the formation into the well bore.
[0045] Perforation 514 is typically located within hydrocarbon formation 512,
to
provide a ready conduit for hydrocarbons to flow from hydrocarbon formation
512 into
well bore 510 where the hydrocarbons can be extracted. Because perforation 514
is
localized within hydrocarbon formation 512, proppant slurry 516 is typically
maintained
within hydrocarbon formation 512, and does not flow into non-producing layer
518 and
non-producing layer 520 that sandwich the hydrocarbon formation 512. Non-
producing
layer 518 and non-producing layer 520 may be formed primarily of shale or
siltstone.
[0046] As hydrocarbons are extracted from hydrocarbon formation 512, changes
in
pore pressure directly affect the horizontal stress. Pore pressure is the
internal pressure of
a certain layer of the formation. Pore pressure is dependent upon the
concentration of
fluids within the formation layer. For a relaxed basin where the overburden
dominates
the stress field, the horizontal stresses in non-producing layer 518 and non-
producing
layer 520 are dependent on the overburden, the Poisson's Ratio, and the
current pore
pressure according to Equation 1:
(7h = 1 (6v - ap) + ap , Equation 1
I-v
where:
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6h = the horizontal stress;
a, = the vertical stress;
v = the Poisson's ratio;
a = the overburden; and
p = the pore pressure.
[0047] The stress in each layer, including hydrocarbon formation 512, non-
producing layer 518 and non-producing layer 520 can then be calculated based
upon the
Poisson's Ratio, and then adjust this stress for depletion. The reduction in
stress within
hydrocarbon formation 512 - often due to a production withdrawal of
hydrocarbons -
leads directly to an increase in horizontal stress within the adjacent, low
permeability
non-producing layer 518 and non-producing layer 520. This increase in
horizontal stress
is due to a static force equilibrium shift from the decreased pressure within
hydrocarbon
formation 512. The horizontal stress reduction in the hydrocarbon layer and
the
horizontal stress increase in the non-producing layers create a stress
discrepancy.
[0048] Referring now to Fig. 6, a cross sectional illustration of a pressure
profile is
shown. The pressure profile of Fig. 6 is obtained as formation fluids are
removed from
the hydrocarbon layer 616, which can be hydrocarbon formation 512 of Fig. 5.
[0049] Formation pressure Pf 610 typically increases with the depth 612 of the
formation. However, formation pressure Pf 610 deviates significantly from
predicted
formation pressure Po 614 in an area of hydrocarbon layer 616, which can be a
production
formation in a reservoir. Because formation fluids have been withdrawn from
hydrocarbon layer 616, formation pressure Pf 610 has been decreased
significantly from
predicted formation pressure Po 614.
[0050] Lateral stress Ohf 618, similar to formation pressure Pf610, also
typically
increases with the depth 612 of the formation. Lateral stress Ohf 618 deviates
significantly from the predicted lateral stress Oho 620. In hydrocarbon layer
616, lateral
stress Ohf 618 experiences a stress reduction due to the withdrawn formation
fluids.
However, in order to maintain static force equilibrium, lateral stress Ohf 618
in
surrounding non-producing layer 622 and non-producing layer 624 will
experience a
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corresponding pressure increase. These stress increases can be seen at lateral
stress
redistribution 626 and stress concentration 628.
[0051] The overall result when considering a reservoir with depletion is that
the
stress contrast between hydrocarbon layer 616, non-producing layer 622, and
non-
producing layer 624 is increased due to stress changes between the media. The
net result
is twofold: first, hydraulic fractures are more vertically confined and hence
longer.
Second, any open hole or perforated shale or siltstone is more liable to
destabilize,
especially at low bottom hole pressure, such as when approaching a depleted
layer with a
drill bit or operating an electric submersible pump completion.
[0052] Thus, lateral stress redistribution 626 and stress concentration 628 in
the
surrounding non-producing layer 622 and non-producing layer 624 can lead to
sandface
failure in those areas. This formation face failure can lead to an
overproduction of sand
contaminants, which adversely affects the pump life of the electric
submersible pumps
providing artificial lift to the reservoir. When contaminants are
overproduced, the
contaminants can find their way into the electric submersible pump, and cause
mechanical failure of the pump.
[0053] In accordance with embodiments of the invention, an intervention is
used to
prevent fine material from being removed from the formation face due to
formation face
failure. The intervention should prevent future plugging of electric
submersible pumps.
The intervention would also prevent local destabilization of the sands at the
perforation
due to the removal of supporting adjacent material.
[0054] Referring now to Fig. 7, a schematic diagram of a fracture packing
intervention applied to a well bore is. shown according to an embodiment of
the
invention. Well bore 710, which can be well bore 228 of Fig. 2, extends
through upper
non-producing layer, 718, hydrocarbon formation 712 and lower non-producing
layer 720.
The hydrocarbon formation layer 712 may be hydrocarbon formation 212 of Fig.
2.
Perforation 714, which can be perforation 230 of Fig. 2, connects well bore
710 to
hydrocarbon formation 712.
[0055] Proppant slurry 716 is pumped into well bore 710 from a drill string
apparatus, such as drill string apparatus 300 of Fig. 3. Proppant slurry 71:6
is pumped
into well bore 710 until the pressure within well bore 710 exceeds the
formation stress.
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When a fracture within the formation is caused to open, the proppant slurry is
forced into the formation. The proppant filled fracture facilitates flow of
hydrocarbons from the formation into the well bore.
[0056] Perforation 714 is extended from their typical location within
hydrocarbon formation 712 to include perforation 714 into non-producing layer
718
and non-producing layer 720 that sandwich the hydrocarbon formation 712.
Proppant slurry 716 is pumped into hydrocarbon formation 712 to provide a
ready
conduit for hydrocarbons to flow from hydrocarbon formation 712 into well bore
710 where they can be extracted. Furthermore, proppant slurry 716 is pumped
into surrounding non-producing layer 718 and non-producing layer 720 to
provide
structural support to those areas during extraction of hydrocarbons from
hydrocarbon formation 712. By providing proppant slurry 716 to surrounding non-
producing layer 718 and non-producing layer 720, a barrier is created between
the
surrounding non-producing layer 718 and non-producing layer 720, thereby
reducing erosion of the sandface due to the static equilibrium shift caused by
removal of hydrocarbons from hydrocarbon formation 712. The barrier layer is
an
amalgamated conglomeration of the proppant slurry and the surrounding rock
matrix which is more resistant to erosion than is the rock matrix of the well
bore
without the proppant.
[0057] Referring now to Fig. 8, a fracture packing intervention technique
800 may be performed according to an embodiment of the invention. Before the
technique 800 commences, at least one operation (a logging operation, for
example) has been conducted for purposes of identifying the locations and
thus,
the boundaries of hydrocarbon formation layers (i.e., producing layers) and
nearly
non-producing layers.
[0058] The technique 800 includes conveying (block 810) a drill string
apparatus down a well bore to provide fracture packing intervention to a
hydrocarbon formation. The drill string apparatus may contain one or more
assemblies for performing perforation or packing intervention in the well bore
and
may be the drill string apparatus 300 of Fig. 3. The drill string apparatus
can be a
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QUANTUM gravel pack system, available from Schlumberger. In other
embodiments of the invention, the perforating may be performed, for example,
in a
prior a run into the well using a perforating string.
[0059] The drill string apparatus is run downhole and positioned to target a
producing layer and at least one non-producing layer. The drill string
apparatus is
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secured into place by inflating formation isolation packers, pursuant to block
820. The
formation isolation packers are adapted for sealingly engaging the well bore.
The
formation isolation packers can be formation isolation packers 322 of Fig. 3.
The
formation isolation packers are typically made of a thermoplastic elastomer,
such as
rubber. Fluid sample chambers provide a channel by which formation fluids can
be
pumped from fluid pump into the interior of the formation isolation packers,
causing the
formation isolation packers to inflate and engage the sides of the well bore.
[0060] The formation isolation packers provide a seal such that the conditions
in
an area between formation isolation packers 322 can be changed, for instance
by altering
the pressure within this area, relative to the conditions elsewhere in the
well bore.
[0061] The technique 800 including pumping (block 830) proppant slurry into
the
well bore until the pressure within the well bore exceeds the formation
stress, causing at
least one fracture within the formation to open and, in accordance with
embodiments of
the invention, at least one fracture in the non-producing layer to open. The
fractures
extend away from the well bore according to the natural stresses within the
formation.
[0062] The pumping continues, pursuant to block 840, to force proppant from
the
well bore into the opened cracks of the formation and non-producing layers.
Proppant is
forced into both the sandstone hydrocarbon formation, as well as the
surrounding, non-
producing siltstone and shale layers.
[0063] Proppant pumped into the surrounding non-producing layers, creates a
barrier between the non-producing sandstone layers and the well bore, pursuant
to block
850. The barrier layer is more erosion resistant than the natural sandstone.
The barrier
layer is a amalgamated conglomeration of the proppant slurry and the
surrounding rock
matrix which is more resistant to erosion than is the rock matrix of the well
bore without
the proppant. The reservoir therefore experiences less erosion when the
barrier layer is in
place.
[0064] When pumping of proppant is complete, the technique 800 includes
deflating (block 860) the isolation packers, and removing (block 860) the
drill string
apparatus from the well bore, with the process terminating thereafter. Excess
proppant is
removed along with the drill string apparatus.
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[0065] It is noted that the isolation packer may be retracted, the string may
be
repositioned and the isolation packers may be re-inflated during the course of
the
fracturing and proppant delivery operation, in accordance with embodiments of
the
invention. Thus, many variations are contemplated and are within the scope of
the
appended claims.
[0066] Referring now to Fig. 9, a flowchart depicting a technique 900 to
manage a
well site is shown according to an embodiment of the invention. The technique
900
includes determining (block 910) an intervention for a well bore at a well
site in an area
where sandface failure is common. The intervention can provide a fracture
packing
proppant to the well bore, as shown in Fig. 7. The well site can be well site
200 of Fig. 2.
[0067] The intervention is then applied to the well bore, pursuant to block
920.
According to the intervention, proppant is pumped into the well bore until the
pressure
within the well bore exceeds the formation stress, causing one or more
fractures to extend
into the formation into non-producing and producing layers. The fracture(s)
extend away
from the well bore according to the natural stresses within the formation.
Pumping of the
proppant continues until the proppant is forced from the well bore into the
opened
fracture(s) of the formation. Proppant is forced into both the sandstone
hydrocarbon
formation, as well as the surrounding, non-producing siltstone and shale
layers. Proppant
pumped into the surrounding non-producing layers, creates a barrier between
the non-
producing sandstone layers and the well bore. The barrier layer is more
erosion resistant
than the natural sandstone. The reservoir therefore experiences less erosion
when the
barrier layer is in place. The barrier layer is an amalgamated conglomeration
of the
proppant slurry and the surrounding rock matrix which is more resistant to
erosion than is
the rock matrix of the well bore without the proppant.
[0068] The technique 900 includes managing (block 930) the well site by
extracting hydrocarbons from the well bore with the technique 900 terminating
thereafter.
[0069] Other embodiments are contemplated and are within the scope of the
appended claims. For example, in accordance with other embodiments of the
invention,
the hydrocarbon producing and non-producing layers may be interleaved. As
another
example, in accordance with other embodiments of the invention, the
hydrocarbon
producing formation may be a formation other than a sandstone formation and
thus, the
14
CA 02646849 2008-12-16
110.0147
SHF.0009US
techniques and systems that are disclosed herein may inhibit a formation face
failure
other than a sandface failure.
[0070] While the present invention has been described with respect to a
limited
number of embodiments, those skilled in the art, having the benefit of this
disclosure, will
appreciate numerous modifications and variations therefrom. It is intended
that the
appended claims cover all such modifications and variations as fall within the
true spirit
and scope of this present invention.
