U.S. patent application number 15/893363 was filed with the patent office on 2019-08-15 for simultaneous fracturing process.
The applicant listed for this patent is Crestone Peak Resources. Invention is credited to Michael Kraynek.
Application Number | 20190249527 15/893363 |
Document ID | / |
Family ID | 67540455 |
Filed Date | 2019-08-15 |
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United States Patent
Application |
20190249527 |
Kind Code |
A1 |
Kraynek; Michael |
August 15, 2019 |
Simultaneous Fracturing Process
Abstract
A method for extracting a natural resource may include creating
a fracture network in a target formation by simultaneously
pressurizing the target formation on opposing sides with hydraulic
fracturing liquid through different wells creating a series of
fractures from each of the different wells with effective fracture
lengths that overlap with each other.
Inventors: |
Kraynek; Michael; (Denver,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Crestone Peak Resources |
Denver |
CO |
US |
|
|
Family ID: |
67540455 |
Appl. No.: |
15/893363 |
Filed: |
February 9, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 49/00 20130101;
E21B 43/26 20130101; E21B 43/267 20130101; E21B 43/17 20130101;
E21B 47/07 20200501; E21B 47/06 20130101 |
International
Class: |
E21B 43/17 20060101
E21B043/17; E21B 43/26 20060101 E21B043/26 |
Claims
1. A method for extracting a natural resource, comprising: creating
a fracture network in a target formation by simultaneously
pressurizing the target formation on opposing sides with hydraulic
fracturing liquid through different wells creating a series of
fractures from each of the different wells with effective fracture
lengths that overlap with each other.
2. The method of claim 1, wherein the effective fracture lengths
are 300 feet or less from each of the different wells.
3. The method of claim 2, wherein the effective fracture lengths
are 200 feet or less from each of the different wells.
4. The method of claim 1, wherein the different wells are spaced
apart from each other at a distance of less than 600 feet.
5. The method of claim 1, wherein the different wells are spaced
apart from each other at a distance of less than 400 feet.
6. The method of claim 5, wherein each of the different wells are
horizontal wells.
7. The method of claim 1, wherein the target formation includes a
known hydrocarbon deposit.
8. The method of claim 1, wherein the target formation is in an oil
shale formation.
9. The method of claim 1, wherein the target formation is between
the different wells.
10. A method for extracting a natural resource, comprising:
creating a first series of fractures from a first well bore section
by pressurizing a target formation with a first hydraulic
fracturing liquid from the first well bore section where the first
series of fractures includes a first effective fracture length that
protrudes into the target formation; and simultaneously creating a
second series of fractures by pressurizing the target formation
with a second hydraulic fracturing liquid from a second well bore
section that is spaced apart from the first well bore section at a
distance and the target formation is located between the first and
the second well bore section where the first series of fractures
includes a second effective fracture length that protrudes into the
target formation and overlaps with the first effective fracture
length.
11. The method of claim 10, wherein at least one of the first
effective fracture length and the second effective fracture length
is 300 feet or less.
12. The method of claim 11, wherein at least one of the first
effective fracture length and the second effective fracture length
is 200 feet or less.
13. The method of claim 10, wherein the distance is less than 600
feet.
14. The method of claim 10, wherein the distance is less than 400
feet.
15. The method of claim 14, wherein each of the first well bore
section and the second well bore section are horizontal well bore
sections.
16. The method of claim 10, wherein the target formation includes a
known hydrocarbon deposit.
17. The method of claim 10, wherein the target formation is in an
oil shale formation.
18. The method of claim 10, wherein the natural resource is a
liquid hydrocarbon.
19. A method for extracting a natural resource, comprising:
creating a first series of fractures from a first horizontal well
bore section by pressurizing a target formation with a first
hydraulic fracturing liquid from the first horizontal well bore
section where the first series of fractures includes a first
fracture length that protrudes into the target formation; and
simultaneously creating a second series of fractures by
pressurizing the target formation with a second hydraulic
fracturing liquid from a second horizontal well bore section that
is spaced apart from the first horizontal well bore section that is
spaced away from the first horizontal well bore section less than
800 feet away and the target formation is located between the first
and the second horizontal well bore section where the first series
of fractures includes a second fracture length that protrudes into
the target formation.
20. The method of claim 19, wherein the second horizontal well bore
section is spaced less than 400 feet apart from the first
horizontal well bore section.
Description
BACKGROUND
[0001] Hydraulic fracturing is a technique for fracturing a
subterranean formation with a pressurized liquid. The process
involves injecting fluid under high pressure into a wellbore to
fracture the rock of the subterranean formation. The liquid
propagates throughout the fractures. When the liquid is removed,
the fractures stay open because sand or other types of proppants
suspended in the fracturing fluid remain in the fractures and keep
the fractures from closing. The open fractures provide greater
access to natural resources such as natural gas and liquid
petroleum and allow these natural resources to flow easier within
the subterranean formation to the well bore for recovery.
[0002] One method of hydraulic fracturing is disclosed in U.S. Pat.
No. 4,724,905 issued to Duane C. Uhri, et al. In this reference, a
process for sequential hydraulic fracturing of a hydrocarbon
fluid-bearing formation. A fracture is induced in said formation by
hydraulically fracturing via one wellbore. Thereafter, while the
formation remains pressurized from the first induced-fracture
operation, a second hydraulic fracturing operation is conducted via
another wellbore substantially within the pressurized formation
area of the first fracturing operation which causes a fracture
trajectory to form contrary to the far-field in-situ stresses. This
second hydraulic fracture will tend to curve away from the first
hydraulic fracture and has the potential of intersecting natural
hydrocarbon fluid-bearing fractures in said formation.
[0003] One method of hydraulic fracturing is disclosed in U.S. Pat.
No. 4,830,106 issued to Duane C. Uhri, et al. A process and
apparatus for simultaneous hydraulic fracturing of a
hydrocarbonaceous fluid-bearing formation. Fractures are induced in
said formation by hydraulically fracturing at least two wellbores
simultaneously. While the formation remains pressurized curved
fractures propagate from each wellbore forming fracture
trajectories contrary to the far-field in-situ stresses. By
applying simultaneous hydraulic pressure to both wellbores, at
least one curved fracture trajectory will be caused to be
transmitted from each wellbore and intersect a natural
hydrocarbonaceous fracture contrary to the far-field in-situ
stresses. Each of these references may be incorporated by reference
for all that they teach.
SUMMARY
[0004] In one embodiment, a method for extracting a natural
resource includes creating a fracture network in a target formation
by simultaneously pressurizing the target formation on opposing
sides with hydraulic fracturing liquid through different wells
creating a series of fractures from each of the different wells
with effective fracture lengths that overlap with each other.
[0005] The effective fracture lengths may be 300 feet or less from
each of the wells.
[0006] The effective fracture lengths may be 200 feet or less from
each of the wells.
[0007] The different wells may be spaced apart from each other at a
distance of less than 600 feet.
[0008] The different wells may be spaced apart from each other at a
distance of less than 400 feet.
[0009] Each of the different wells may be horizontal wells.
[0010] The target formation may include a known hydrocarbon
deposit.
[0011] The target formation may be in an oil shale formation.
[0012] The natural resource may be a liquid hydrocarbon.
[0013] The target formation may be between the different wells.
[0014] In some embodiments, a method for extracting a natural
resource includes creating a first series of fractures from a first
well bore section by pressurizing a target formation with a first
hydraulic fracturing liquid from a first well bore section where
the first series of fractures includes a first effective fracture
length that protrudes into the target formation, and simultaneously
creating a second series of fractures by pressurizing the target
formation with a second hydraulic fracturing liquid from a second
well bore section that is spaced apart from the first well bore
section at a distance and the target formation is located between
the first and the second well bore section where the first series
of fractures includes a second effective fracture length that
protrudes into the target formation and overlaps with the first
effective length.
[0015] At least one of the first effective fracture length and the
second effective fracture length may be 300 feet or less.
[0016] At least one of the first effective fracture length and the
second effective fracture length may be 200 feet or less.
[0017] The first well bore section may be spaced apart from the
second well bore section at a distance of less than 600 feet.
[0018] The first well bore section may be spaced apart from the
second well bore section at a distance of less than 400 feet.
[0019] Each of the first well bore section and the second well bore
section may be horizontal well bore sections.
[0020] The target formation may include a known hydrocarbon
deposit.
[0021] The target formation may be in an oil shale formation.
[0022] The natural resource may be a liquid hydrocarbon.
[0023] In one embodiment, a method for extracting a natural
resource includes creating a first series of fractures from a first
horizontal well bore section by pressurizing a target formation
with a first hydraulic fracturing liquid from a first horizontal
well bore section where the first series of fractures includes a
first fracture length that protrudes into the target formation, and
simultaneously creating a second series of fractures by
pressurizing the target formation with a second hydraulic
fracturing liquid from a second horizontal well bore section that
is spaced apart from the first horizontal well bore section that is
spaced away from the first horizontal well bore section less than
800 feet away and the target formation is located between the first
and the second horizontal well bore section where the first series
of fractures includes a second fracture length that protrudes into
the target formation.
[0024] The second horizontal well bore section may be spaced less
than 400 feet apart from the first horizontal well bore
section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 depicts an example of fracturing a target formation
simultaneously from a first well bore and a second well bore in
accordance with aspects of the present disclosure.
[0026] FIG. 2 depicts a cross sectional view of an example of a
first well bore and a second well bore in an underground strata in
accordance with aspects of the present disclosure.
[0027] FIG. 3 depicts a cross sectional view of an example of
simultaneously hydraulically fracturing a target formation with a
first vertical well and a second vertical well in accordance with
aspects of the present disclosure.
[0028] FIG. 4 depicts a top down, cross sectional view of an
example of a fractured subterranean formation in a vertical well in
accordance with aspects of the present disclosure.
[0029] FIG. 5 depicts a top down, cross sectional view of an
example of a fractured subterranean formation in a horizontal well
in accordance with aspects of the present disclosure.
[0030] FIG. 6 depicts an example of hydraulically fracturing a
target formation in accordance with aspects of the present
disclosure.
[0031] FIG. 7 depicts an example of hydraulically fracturing a
target formation with a first well and a second well in accordance
with aspects of the present disclosure.
DETAILED DESCRIPTION
[0032] For purposes of this disclosure, the term "aligned" means
parallel, substantially parallel, or forming an angle of less than
35.0 degrees. For purposes of this disclosure, the term
"transverse" means perpendicular, substantially perpendicular, or
forming an angle between 55.0 and 125.0 degrees. Also, for purposes
of this disclosure, the term "length" means the longest dimension
of an object. Also, for purposes of this disclosure, the term
"width" means the dimension of an object from side to side. Often,
the width of an object is transverse the object's length. For the
purposes of this disclosure, the "effective fracture length"
generally refers to just the portion of the fracture that
corresponds having 90.0% of the cumulative gas flow rate from the
formation to the well bore.
[0033] For the purposes of this disclosure, the term "horizontal
well bore section" generally involves wellbores with a section of
the well bore aligned with the rock layer containing the natural
resource to be extracted. Generally, the horizontal section is a
terminal section of the well bore and may be referred to as a
"lateral." In some cases, more than one horizontal lateral may be
drilled from the same well site and share a common vertical section
with other laterals. In other cases, each of the horizontal wells
do not share the same vertical section, but are drilled at
different surface locations. In some examples, a horizontal well
bore may extend nearly 2,000 feet or longer. In contrast, a
vertical well is generally much shorter. Horizontal drilling
reduces the surface footprint as fewer wells are involved to access
the same volume of rock. Generally, horizontal wells make contact
with more of the rock bearing the natural resource and may have
greater production rates over a longer period of time.
[0034] Hydraulic fracturing may be used to increase the production
of natural resources to be extracted through a well bore, such as
petroleum, water, or natural gas. In some cases, hydraulic
fracturing can optimize the economic production of the well by
maintaining the same productions rates at a lower cost. Hydraulic
fracturing may increase the initial production, the estimated
ultimate recovery from the well, or increase another aspect of the
well's production. Hydraulic fracturing may also be used in making
a first completion, such as in the zone of interest; recompleting a
well, such making a completion in another part of the well;
refracturing the well, such as when re-stimulating a primary
completion or a recompletion; deepening the well, such as when
drilling the well deeper and completing that portion of well with a
smaller diameter; re-drilling the well, such as when drilling
another well next to an existing well, another drilling or
completion task, or combinations thereof.
[0035] The natural resources may be located in different types of
rocks, such as sandstones, limestones, dolomite rocks, shale rock,
coal beds, other types of formations, or combinations thereof.
Hydraulic fracturing can be applied in rock formations below the
earth's groundwater reservoir levels. At these depths, there may be
insufficient permeability in the reservoir to allow natural gas and
oil to flow from the rock into the wellbore at desirable returns.
By fracturing the rock, the permeability of the formation increases
thereby improving the production of the natural resource.
[0036] The placement of one or more fractures along the length of
the borehole can be determined by different methods. One type of
method includes using a perforating gun to create holes in the well
bore's casing.
[0037] A hydraulic fracture may be formed by injecting a fracturing
fluid into a wellbore with a high enough pressure through the well
bore's perforations. This pressurized fluid increases the
subterranean formation's pressure to a level where the rock
fractures. As the rock cracks, fissures are created that allows the
fracture fluid to permeate deeper into the rock and thereby
increasing the formation pressure deeper and deeper into the
formation thereby extending the cracks further. The hydraulic fluid
may include a proppant (e.g. grains of sand, ceramic, or other
particulate) that remain in the fractures after the hydraulic fluid
has drained out of the formation and prevent the fractures from
closing. The propped fracture maintains an increased permeability
to allow the flow of the natural resource to the well.
[0038] Equipment that may be used in hydraulic fracturing may
include a slurry blender, one or more high-pressure, high-volume
fracturing pumps, a monitoring unit, units for storage and handling
of proppant, a chemical additive unit, low-pressure flexible hoses,
and gauges and meters for flow rate, fluid density, and treating
pressure.
[0039] Any appropriate type of fracturing fluid may be used in
accordance with the principles described in the present disclosure.
In some examples, the fracturing fluid includes a slurry of water,
proppant, and chemical additives. In some cases, the fracturing
fluid may also include gels, foams, and compressed nitrogen,
compressed carbon dioxide, compressed air, another type of
compressed gas, hydrochloric acid, acetic acid, sodium chloride,
polyacrylamide, ethylene glycol, borate salts, zirconium salts,
chromium salts, antimony salts, titanium salts, other types of
salts, sodium carbonates, potassium carbonates, glutaraldehyde,
guar gum, citric acid, isopropanol, methanol, isopropyl alcohol,
2-butoxyethanol, and ethylene glycol, aluminum phosphate and ester
oils or combinations thereof. The fracturing fluid may be between
85.0 percent to 95.0 liquid or gas, between 5.5 percent and 9.5
percent proppant, and 1.0 to 0.25 percent chemical additives.
[0040] In other examples, the fracturing fluid may be a gel, a
foam, or be slickwater-based. Gels may be useful in situations
where it would otherwise be difficult to keep the proppant in
suspension. Slickwater, which is less viscous and has a lower
friction, may allow fluid to be pumped at higher rates which allows
fractures to be created farther out from the wellbore.
[0041] Any appropriate proppant may be used in accordance with the
principles of described in the present disclosure. In some cases,
the proppant may be a granular material, such as sand or a
synthetic material that prevents the fractures from closing after
the target formation is pressurized. Types of proppant may include
silica sand, resin-coated sand, bauxite, man-made ceramics, another
type of proppant, or combinations thereof. Bauxite or ceramics may
be used in situations where the formation pressure is high enough
to crush natural silica sand.
[0042] The subterranean pressure and fracture growth rate may be
measured during the hydraulic fracturing process. Additionally,
known geological features can be used to model the fractures by
length and width.
[0043] Radioactive tracers can be used to determine the injection
profile and location of created fractures. Any suitable
radiotracers may be used in accordance with the principles
described in the present disclosure. Suitable radioactive isotopes
chemically bonded to at least some of the proppant may also be
injected into the formation with the hydraulic fluid to track
fractures. In some examples, some of the proppant may be coated
with isotopes of silver, isotopes of iridium, isotopes of
technetium, isotopes of iodine, another appropriate type of
isotope, or combinations thereof to track the fracture profiles
and/or flow rates of the hydraulic fluid.
[0044] The temperature of the well may be monitored at different
lengths, which assists in determining where the fracturing fluid is
located and the associated volumes. Fiber optic cable, wired pipe,
or other types of communication systems may be used to transmit
this data to the surface in real time. In other examples, the data
may be retrieved after the fracturing procedure and analyzed at a
later time.
[0045] Horizontal wellbores can be useful in shale formations where
horizontal wellbores tend to produce more economically than with a
vertical well. Shales may be fractured by the plug and perforation
method in the well bore either in a cemented or uncemented well
bore. A wireline tool may be lowered into the well bore at a first
stage location to perforate the well bore. With the well bore
perforated, the fracturing fluid is pumped into the formation.
Next, another plug is set in the well to temporarily seal off the
previously pressurized section of the well bore so the next section
of the wellbore can be perforated and then pressurized with the
hydraulic fracturing fluid. The process is repeated along the
horizontal length of the wellbore. Fracturing creates pathways in
the rock, allowing for hydrocarbons to flow from the rock to the
wellbore for production. The low permeability in the shale
reservoirs results in hydrocarbon molecules that are relatively
immobile in the reservoir.
[0046] In other examples, sliding sleeves are used to sequentially
fracture the formation at different locations along the length of
the well bore. Once one stage has finished the pressurizing the
formation, the next sleeve is opened, concurrently isolating the
previous stage, and the process repeats.
[0047] The number of stages used to hydraulically fracture the
formation may vary from target formation to target formation. In
some cases, a hydraulic fracturing method may have a single
hydraulic fracturing stage to greater than thirty hydraulic
fracturing stages. But, any appropriate number of fracturing stages
may be used in accordance with the present disclosure.
[0048] When the subterranean formation is pressurized, the fracture
is created along the path of least resistance. The fracture may
radiate out from the well bore in a single direction or in multiple
directions when a single well bore is hydraulically fractured at a
time. The entire fracture length may stretch a substantial
distance, but the proppant may not travel as far as the entire
length of the fracture. Further, the entire length of the fracture
may not cause the formation to separate a meaningful amount to
increase the permeability of the target formation. Generally, just
a sub-portion of the fracture length results in increasing contact
with the formation to yield an increase in production. That portion
of the fracture length that contributes to 90.0 percent of the
increased flow through the target formation may be referred to as
an effective fracture length and is generally under 300 feet
long.
[0049] Propagation of fractures during hydraulic fracturing
treatments is governed by in-situ stresses in the rock. Fractures
will generally propagate in a direction perpendicular to the least
principal stress. Close to the well, multiple fractures may emanate
outward in multiple directions when a single well bore is
hydraulically fractured at a time, but those fractures tend to
converge together as the fractures progress outward away from the
well bore. Fractures propagating in one direction tend to be long,
but do not necessarily contact high volumes of rock.
[0050] Maximizing fracture density, sometimes called stimulated
reservoir volume (SRV), can be a difficult task because rock
resists being fractured in a complex pattern. Fracture behavior is
governed by stresses in the earth. Rock tends to fracture in the
direction of maximum principal stress.
[0051] The principles described herein include simultaneously
pumping a fracturing treatment into two or more adjacent wellbores
with fracturing stages lined up along a fracture azimuth to
artificially increase the pressure of the target formation at a
localized area, resulting in a growth of fracture complexity,
further resulting in higher stimulated reservoir volume and a more
productive well.
[0052] The increase in pressure from the simultaneous fracturing
operation would not need to overcome both minimum and maximum
stresses. Rather, the increase in pressure just needs to exceed
minimum stress by some percentage to start growing complex
fractures away from the initial fracture. In other words, with the
simultaneous fracturing on multiple sides of the target formation
and with the first and second well bores in close enough proximity
to each other, the fractures diverge from each other rather than
converging to a single dominant fracture.
[0053] By simultaneously fracturing the target formation along the
azimuth fracture direction to localize the pressure, the
perforation fractures develop a complex network of fractures that
spread outward rather than having the fractures converge to a
single dominant fracture that occurs with just a single well bore
that is fractured at a time. The increased complexity of the
fracture network can result in greater well production.
[0054] Simultaneously fracturing the target formation between the
wells may be fractured more intensely with additional complex
fractures exposing more rock for production. The simultaneous
hydraulic fractures are from well bores that are close to the
target formation such that the effective fracture lengths from each
of the well bores may spatially overlap. The pressure generated
from the first well affects the fracture from the second well, and
the pressure generated from the second well affects the fracture
from the first well. Thus, the pressure from the first well
prevents the fractures from the second well from converging to a
single dominant fracture, and the pressure from the second well
prevents the fractures from the first well to converge to a single
dominant fracture. As a result, the fractures spreads creating a
larger and more complex fracture network that increases the contact
with more of the target formation.
[0055] Now referring to specific examples with the figures, FIG. 1
depicts an example of hydraulically fracturing a target formation
100 from a first well bore 102 and hydraulically fracturing the
target formation 100 from a second well bore 104 simultaneously. In
this example, the first well bore 102 includes a first well bore
section 106 that extends horizontally from a first vertical section
108. Also, in this example, the second well bore 104 includes a
second well bore section 110 that extends horizontally from a
second vertical section 112. The target formation 100 is between
the first well bore section 106 and the second well bore section
110. A first subset 114 of fractures emanate from the first well
bore 102, and a second subset 116 of fractures emanate from the
second well bore 104. As depicted in the example of FIG. 1, the
fractures from the first subset 114 and the second subset 116
overlap with each other. In some cases, the fractures from the
first subset and the fractures from the second subset
interconnect.
[0056] Further, the fractures of the first subset 114 propagate
towards the second well bore 104, and fractures of the second
subset 116 propagate forward towards the first well bore 102 within
the target formation 100. Fractures of the first and second subsets
within the target formation may propagate without converging into a
dominant fracture direction. However, those fractures that emanate
out from the far sides 118 of the first and second well bores 102,
104 may include fractures that converge into a single dominant
fracture. On the other hand, at least some of the fractures within
the target formation 100 may even diverge from each other. It is
believed that the pressure increase from the first well bore 102
and the pressure increase from the second well bore 104 create more
destructive damage to the target formation when released
simultaneously than would otherwise occur if each of the well bores
were used to hydraulically fracture the formation at separate
times.
[0057] Each of the first and second well bores 102, 104 may be
perforated with a perforation gun or with another appropriate
mechanism. The perforated clusters formed by the perforation guns
of the first well bore 102 may be aligned with the perforation
clusters of the second well bore 104. The fracturing stage 120 may
be the area along the length of the well bores that is pressurized
during a hydraulic fracturing event and may encompass the
perforated clusters. The fracturing stage 120 of the first well
bore 102 may be aligned with the fracturing stage 120 of the second
well bore 104. In some examples, while the first and second well
bores 102, 104 may include multiple fracturing stages to be
pressurized, just one of the stages may be pressurized at a time
within the same well bore. In some cases, the stages within a
single well bore may be fractured sequentially along the length of
the well bore while still being fractured simultaneously with the
aligned stages of the other well bore.
[0058] However, the fracturing stage 120 of the first well bore 102
that is aligned with the fracturing stage 120 of the second well
bore 104 may be triggered simultaneously. With the aligned
fracturing stages being triggered at the same time, the pressure
between the aligned stages forces the pressures released from the
first well bore 102 to interact with the pressures released from
the second well bore 104 due to the proximity of the hydraulic
fracturing stages.
[0059] The stage lengths may be any appropriate length. In some
examples, at least one of the stage lengths is less than 150 feet,
less than 200 feet, less than 250 feet, less than 300 feet, less
than 400 feet, or less than another appropriate distance.
[0060] In the example of FIG. 1, the first well bore section and
the second well bore section are horizontal sections that are
located at different heights. In this example, the first well bore
section is located deeper within the earth than the second well
bore section. The target formation is located between the varying
heights of the first and second well bore sections. In this
example, the first well bore section and the second well bore
section may be located within the same strata, such as a layer of
porous oil bearing rock. In other examples, the first well bore
section and the second well bore section may be located in
different strata or even different types of strata.
[0061] FIG. 2 depicts an example of a first horizontal well bore
section 200 and a second horizontal well bore section 202 within
the same strata 204. In this example, the first and second well
bore sections 200, 202 are generally at the same depth of earth.
However, in other examples, the first and second well bore sections
200, 202 may be at different depths, but still spaced apart
horizontally within the same strata 204.
[0062] The first well bore section 200 and the second well bore
section 202 may be spaced apart at any appropriate distance that
allows the pressures from the simultaneous fracturing of the
different well bores to prevent the convergence of the fractures to
a dominant fracture and/or direction. In some examples, the first
well bore section is spaced at a distance of less than 800 feet
from the second well bore section. In some cases, the first well
bore section is spaced at a distance of less than 600 feet from the
second well bore section. Further, the first well bore section may
be spaced at a distance of less than 400 feet from the second well
bore section.
[0063] As the pressure recedes in the formation after
pressurization, the proppant in the hydraulic fracturing liquid
remains behind keeping the fractures open. With the fractures
remaining open, the natural resources within the formation may move
towards either the first well bore section 200 or the second well
bore section 202. In some cases, the strata 204 containing the
natural resource is a shale material that contains oil within the
pores of the shale. The downhole pressure may cause the oil in the
pores to move towards areas lower pressure, such as in the
fractures towards the well bores. This pressure differential may
cause the oil to move from the subterranean formation into the well
bore and move towards the surface where the oil can be
collected.
[0064] The fractures formed on the target side 206 of the well
bores may be included in those fractures that synergistically crack
more rock while those fractures that are on the far side 208 of the
well bores may converge into a single dominant fracture 210.
[0065] FIG. 3 depicts an example of a first vertical well bore 300
and a second vertical well bore 302 where a first stage 304 of the
first well bore 300 is fractured simultaneously with a second stage
306 of the second well bore 302. The first stage 304 and the second
stage 306 are aligned with each other along the dominant direction
of the target formation. In some examples, the first stage 304 and
the second stage 306 that are fractured simultaneously are at the
same depth, substantially the same depth, or within 5.0 percent of
the same depth. In some cases, the first and second stages 304, 306
are in the same pay bearing strata.
[0066] In other examples, the first well bore may be a vertical
well bore and the second well bore may be a horizontal well bore.
In such an example, the first stage of the first well bore may
still be aligned with the second stage of the second well bore.
When they are fractured simultaneously, the collective
pressurization may cause the fractures to spread rather than allow
the fractures to converge into a congregate towards a single
fracture.
[0067] One advantage to fracturing the rock with stages that are
aligned along the fracture azimuth is that a web or network of
fractures in both the directions of maximum principle stress and
perpendicular to that stress are created. Whereas when the stages
fracture the formation simultaneously, but are misaligned, it is
believed that the pressure from first well will cause the fractures
from the second well to be angled away from the hydraulic
fracturing stage of the first well. Such a misdirected fracture may
not form the network of fractures and increase the surface area of
the rock accessible to the either the first well or the second
well. Rather, misaligning the stages that are activated
simultaneously may be used to direct a fracture, but may not have
the result of creating an increased fracture network.
[0068] FIG. 4 depicts a cross sectional example of a first vertical
well 400 and a second vertical well 402 viewed from the earths'
surface. In this example, the fractures between first vertical well
400 and the second vertical well 402 form a network 404 of
fractures. On the other hand, those fractures that formed on the
far side 406 of the first and second wells 400, 402 are fewer and
converge together to form a single dominant fracture.
[0069] FIG. 5 depicts a cross sectional example of a horizontal
vertical well 500 and a second horizontal well 502 viewed from the
earths' surface. In this example, the fractures between first
horizontal well 500 and the second horizontal well 502 form a
network 504 of fractures. On the other hand, those fractures that
formed on the far side of the first and second wells 500, 502 are
fewer and converge together to form a single dominant fracture.
[0070] FIG. 6 shows a flowchart illustrating a method 600 of
simultaneously fracturing a target formation. The operations of
method 600 may be implemented by any of the hydraulic fracturing
systems described in FIGS. 1-5 or their components as described
herein. In this example, the method 600 includes creating 602 a
fracture network in a target formation by simultaneously
pressurizing the target formation on opposing sides with hydraulic
fracturing liquid through different wells creating a series of
fractures from each of the different wells with effective fracture
lengths that overlap with each other.
[0071] At block 602, a target formation is fractured by
simultaneously pressurizing the target formation from two
directions. The pressurization from both sources is close enough to
each other that the target formation is compressed in tension in
some directions and pulled in tension in other directions such that
the induced fractures are caused to spread out rather than converge
together. The effective fracture lengths of the series of fractures
from the first well and the series of fractures from the second
well travel deep enough into the target formation that the
effective fracture lengths may cross each.
[0072] FIG. 7 shows a flowchart illustrating a method 700 of
simultaneously fracturing a target formation. The operations of
method 700 may be implemented by any of the hydraulic fracturing
systems described in FIGS. 1-5 or their components as described
herein. In this example, the method 700 includes creating 702 a
first series of fractures from a first well by pressurizing a
target formation with a first hydraulic fracturing liquid from a
first well where the first series of fractures includes a first
effective fracture length that protrudes into the target formation,
and simultaneously creating 704 a second series of fractures by
pressurizing the target formation with a second hydraulic
fracturing liquid from a second well that is spaced apart from the
first well at a distance and the target formation is located
between the first and the second well where the first series of
fractures includes a second effective fracture length that
protrudes into the target formation and overlaps with the first
effective length.
[0073] At block 702, a first series of fractures from a first well
are formed in a target formation by pressurizing the formation with
a first hydraulic fracturing fluid. This series of fractures
includes at least one effective fracture length that protrudes into
the target formation. The effective fracture length may be that
portion of a fracture that corresponds to 90 percent of the flow
for that particular fracture.
[0074] At block 704, a second series of fractures from a second
well are formed in a target formation simultaneously pressurizing
the target formation with a second hydraulic fluid. These fractures
include effective fracture lengths that also protrude into the
target formation. The effective fracture lengths of the first
series of fractures and the effective fracture lengths of the
second series of fractures may spatially overlap each other in the
target formation.
[0075] In some cases, the first hydraulic fluid and the second
hydraulic fluid are the same type of fluid, substantially the same
type of hydraulic fluid, or different types of hydraulic fluid.
Further, in some cases, the volume of the first hydraulic fluid is
same as, substantially the same as, or different than the volume of
the second hydraulic fluid. Additionally, the pressure induced with
the first hydraulic fluid may be the same as, substantially the
same as, or different than the amount of pressure induced with the
second hydraulic fluid.
[0076] In some examples, simultaneously creating fractures from the
first well and the second well may include triggering the hydraulic
fracturing events in both wells at exactly the same time. In some
cases, simultaneously creating fractures from the first well and
the second well may include triggering the hydraulic fracturing
events in both wells within one minute of each other, within five
minutes of each other, within ten minutes of each other, within 15
minutes of each other, within 25 minutes of each other, within
another appropriate time period, or combinations thereof.
[0077] In other examples, simultaneously creating fractures from
the first well and the second well include different triggering
start time, but that at least some period of time exists where the
pressure from the first well and the pressure from the second well
are increasing at the same time. For example, in some cases,
pressurizing a target formation from a first well from a base
formation pressure to a peak formation pressure may occur over a
period of time. This period of time may be referred to as a first
pressurization time period. Likewise, pressurizing the target
formation from the second well from the base formation pressure to
the peak formation pressure may also occur over a period of time.
This second period of time may be referred to as a second
pressurization time period. Thus, for the purposes of this
disclosure, simultaneously creating fractures in the target
formation from the first well and creating fractures in the target
formation from the second well may include having at least some
temporal overlap between the first pressurization time period and
the second pressurization time period.
[0078] In another example, simultaneously creating fractures from
the first well and the second well include having at least some
period of time that exists where the pressure from the first well
and the pressure from the second well are increased at the same
time. In this example, the target formation remains in an increased
pressurized state even after reaching a peak pressure. After
reaching the peak pressure, the pressure in the target formation
may diminish, but still have an elevated pressure above the base
formation pressure resulting the hydraulic fluid from either the
first well or the second well. Fractures may be created even after
the formation pressure is diminishing. After some point, the
formation pressure may return to the base formation pressure or
drop below the base formation pressure. The time period in which
the target formation initially increases pressure from the base
formation pressure and returns to at least 50 percent of the base
pressure from the hydraulic fluid from the first well may be
referred to as the first elevated pressure time period. Similarly,
the time period in which the target formation initially increases
pressure from the base formation pressure and returns to at least
50 percent of the base pressure from the hydraulic fluid from the
second well may be referred to as the second elevated pressure time
period. In some examples, simultaneously creating fractures from
the first well and the second well may include having a temporal
overlap between the first elevated pressure time period and the
second elevated pressure time period.
[0079] In another example, simultaneously creating fractures from a
first well and a second well may refer to a time period in which
fractures are still forming in the target formation as a result of
the hydraulic fracturing. In some cases, as the target formation is
pressurized, the stresses in the target formation cause the
formation to move creating the fractures, but as the formation
depressurizes the target formation may still move resulting in
additional fractures.
[0080] It should be noted that the methods described above describe
possible implementations, and that the operations and the steps may
be rearranged or otherwise modified and that other implementations
are possible. Furthermore, aspects from two or more of the methods
may be combined.
[0081] The description herein is provided to enable a person
skilled in the art to make or use the disclosure. Various
modifications to the disclosure will be readily apparent to those
skilled in the art, and the generic principles defined herein may
be applied to other variations without departing from the scope of
the disclosure. Thus, the disclosure is not limited to the examples
described herein, but is to be accorded the broadest scope
consistent with the principles and novel features disclosed
herein.
* * * * *