Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF TREATING AN UNDERGROUND FORMATION
FEATURING SINGLE-POINT STIMULATION
CROSS-REFERENCE TO RELATED APPLICATIONS
100011 This application claims the priority to U.S. Provisional
Application, Serial
No. 62/037,873, filed August 15, 2014, which is herein incorporated in its
entirety.
BACKGROUND
[0002] Wellbore treatment methods often are used to increase
hydrocarbon
production by using a treatment fluid to affect a subterranean formation in a
manner that
increases oil or gas flow from the formation to the wellbore for removal to
the surface.
Treatment operations may include fracturing operations, matrix acidizing
fracturing, and
injection of chelating agents. Hydraulic fracturing involves injecting fluids
into a
subterranean formation at pressures sufficient to form fractures in the
formation, with the
fractures increasing flow from the formation to the wellbore. In chemical
stimulation,
flow capacity is improved by using chemicals to alter formation properties,
such as
increasing effective permeability by dissolving materials in or etching the
subterranean
formation. Wellbore treatments may be applied in open or cased hole in which a
metal
casing has been cemented in place in a drilled hole. In a cased wellbore, the
casing (and
cement if present) may be perforated in specified locations to allow
hydrocarbon flow
into the wellbore or to permit treatment fluids to flow from the wellbore to
the formation.
[0003] To access hydrocarbon-rich intervals, treatment fluids may be
directed to
multiple zones of interest in a given wellbore passing through a formation.
Within a
single wellbore, there may be one or more zones of interest within various
subterranean
formations or multiple layers within a particular formation. Methods of
targeting
multiple zones often involve treating single or multiple zones within the well
at time
through the use of various fracturing technologies. For example, methods may
involve
multiple steps such as running a perforating gun down the wellbore to the
target zones,
perforating the target zones, removing the perforating gun, treating the
target zones with
a hydraulic fracturing fluid, and then isolating the perforated target zones.
This process
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may then subsequently repeated for all the target zones or a subset of target
zones of
interest until all the target zones are treated.
SUMMARY
[0004] This summary is provided to introduce a selection of concepts
that are
further described below in the detailed description.
[0005] In one aspect, methods of the present disclosure are directed
to methods of
treating an underground formation, including: obtaining logging data for at
least a section
of a wellbore; treating a plurality of zones in at least a section of the
wellbore using the
multi-stage single-point fracturing operation; obtaining one or more of
treatment data,
flowback data, or production data for the treated plurality of zones; defining
one or more
dependencies between the obtained logging data and one or more of treatment
data,
flowback data, or production data; and using the dependencies to design and
perform
subsequent operations on the at least a section of a wellbore or in another
wellbore.
[0006] In another aspect, methods of the present disclosure are
directed to methods
of designing a completion string including: obtaining logging data from at
least a section
of a wellbore; performing a multi-stage single-point fracturing treatment on a
plurality of
zones in the at least a section of a wellbore; obtaining one or more selected
from a group
of treatment data, flowback data, and production data; defining one or more
dependencies
between the obtained logging data and the one or more selected from a group of
treatment data, flowback data, and production data; designing a completion
string using
the defined one or more dependencies, and emplacing the designed completion
string.
[0007] This summary is not intended to identify key or essential
features of the
claimed subject matter, nor is it intended to be used as an aid in limiting
the scope of the
claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 is an example of a workflow demonstrating processes
included in
methods in accordance with embodiments described herein.
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[0009] Figure 2 is an example of a workflow that includes providing a
design for
multi-stage completion system based on acquired logging data in accordance
with
embodiments described herein.
[0010] Figure 3 is an example of a workflow with a pre-defined design
for a multi-
stage completion system in accordance with embodiments described herein.
DETAILED DESCRIPTION
[0011] At the outset, it should be noted that in the development of
any such actual
embodiment, numerous implementation-specific decisions must be made to achieve
the
developer's specific goals, such as compliance with system related and
business related
constraints, which will vary from one implementation to another. Moreover, it
will be
appreciated that such a development effort might be complex and time consuming
but
would nevertheless be a routine undertaking for those of ordinary skill in the
art having
the benefit of this disclosure. In addition, the compositions used/disclosed
for use in the
methods described herein can also include some components other than those
cited.
[0012] In the present disclosure, numerical values should be read once
as modified
by the term "about" (unless already expressly so modified), and then read
again as not so
modified unless otherwise indicated in context. Also, in the present
disclosure, it should
be understood that a concentration range listed or described as being useful,
suitable, or
the like, is intended that any and every concentration within the range,
including the end
points, is to be considered as having been stated. For example, "a range of
from 1 to 10"
is to be read as indicating each and every possible number along the continuum
between
about 1 and about 10. Thus, even if specific data points within the range, or
even no data
points within the range, are explicitly identified or refer to only a few
specific, it is to be
understood that inventors appreciate and understand that any and all data
points within
the range are to be considered to have been specified, and that inventors
possessed
knowledge of the entire range and all points within the range. The statements
made
herein merely provide information related to the present disclosure and may
not
constitute prior art, and may describe some embodiments illustrating the
disclosure.
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[0013] In one aspect, embodiments of the present disclosure are
directed to methods
of treating an underground formation penetrated by a well that utilize single-
point
fracturing techniques to stimulate the production of formation fluids and/or
generate
information regarding the fractured intervals of the wellbore. As used herein,
"single-
point fracturing" refers to a technique in which a targeted interval of a
formation is
treated through a single opening at a time, thus providing better control of
the flow rate of
the treatment fluid and allowing a direct opportunity to measure the changes
in the
formation associated with the single point of fracture the formation. Examples
of an
opening through which treatments may be delivered include a fracturing sleeve,
kick-start
valve, single perforated cluster, open hole wellbore interval isolated between
two
packers, including inflatable packers, and the like. In some embodiments
suitable lengths
or diameter of the opening may be within in the range 0.03-20ft (0.001-6.1m),
0.03-5ft
(0.001-1.5m), or 0.03-2ft (0.001-0.61m); however, the ranges provided are
merely
guidelines and do not limit the present disclosure.
[0014] Single-point fracturing as used in methods in accordance with
the present
disclosure may enable diagnostics to be performed on a single wellbore in a
formation,
creating a convenient laboratory for the analysis of a range of treatments on
similar
intervals within a formation having similar mineralogical composition and
physical
characteristics, or using assaying a single treatment against intervals having
differing
composition and properties. The use of single-point fracturing may also
translate to a
decrease of the volume of a terminal flush substage required to clean the
wellbore of
particles (often referred to as overflush) prior to initiation of fracturing a
successive
wellbore treatment stage, or may even eliminate overflushing altogether in
some
instances.
[0015] Single-point fracturing may be contrasted with other fracturing
techniques
such as "plug-and-perf." During plug-and-perf fracturing, operation involves
lowering a
perforating gun loaded with explosive to a zone, igniting the gun(s) thus
creating
perforation through the tubing and the near wellbore. However, such techniques
may be
problematic in that an operator may underestimate the near wellbore connection
and its
effect on conductivity, and thus ultimately production. Common practice is
often to
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perforate 4-6 clusters, and push a proppant loaded fracturing fluid at
fracture pressure to
create and propagate fractures in the formation; it is estimated that 30 to
60% of these
perforations do not produce hydrocarbons due to, for example, screen out,
geological
constraints, etc., and thus for every 100 perforations in a wellbore, commonly
only 30 to
70 of the conventional perforations are useful for production.
[0016] Embodiments herein relate to a method for completing a well
including
completing a zone of a first well using a single-point fracturing technique,
acquiring data
from the completion of the first well, interpreting the data, tailoring an
optimized design
for completing a further well, and completing a further well with the tailored
design.
Some embodiments may benefit from drilling and acquiring data during the
drilling of
the first well (i.e., logging while drilling). In some embodiments, a
plurality of zones
(and at least three zones in more particular embodiments) are completed with
single-point
fracturing. In some embodiments, the data acquired includes injection flow
rate, flow
back rate, and/or production rate. In some embodiments, the drilling data
(i.e., logging
data) acquired are correlated with completion data including injection flow
rate, flow
back rate, and/or production rate. In some embodiments, the further wells are
also
completed using single-point fracturing workstring; however, the disclosure is
not limited
to the use of single-point fracturing alone, and other embodiments may use
other
fracturing techniques, such as plug-and-perf. In some embodiments, the
tailoring
includes modifying at least one of the following: drilling and landing another
well,
cementing another well, treating another well, flowing back another well, and
producing
another well.
[0017] Embodiments herein relate to methods for designing a well
treatment
including completing a zone of a first well, prior to or after, using a single-
point
fracturing technique, acquiring data from the completion of the first well,
interpreting the
data, and tailoring an optimized design for completing one further zone. In
some
embodiments, the optimized design includes at least one of the following:
modifying the
fracturing fluid composition, pumping acid, modifying the injection flow rate,
drilling
and landing another well, cementing another well, treating another well,
flowing back
another well, and producing another well.
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[0018] Embodiments herein relate to a method for designing a
completion string
that includes completing a plurality of zones of a first well using a single-
point fracturing
technique, acquiring data from the completion of the first well, interpreting
the data, and
tailoring an optimized design for the completion string to be used in a
further well. In
some embodiments, the single-point fracturing string embeds sliding sleeves
and the
tailoring includes modifying the spacing of the sleeves. In some embodiments,
the
number of sleeves is reduced.
[0019] Methods of treating a wellbore in accordance with the present
disclosure
may include acquiring logging data along a wellbore section, treating the
section using
single-point fracturing methodology (treating one zone per stage), and then
determining
dependencies that exist between the acquired logging data and the data
acquired during or
after subsequent treatment operations. For example, data obtained from the
treatment
operation itself, such as changes in pressure or near-well permeability, or
from
subsequent operations including flowback operations in which data is acquired
from
injecting tracer fluids and measuring the return flow, or from the rate of
fluid flow from
production operations carried out in the treated wellbore.
[0020] In some embodiments, dependencies established from single-point
fracturing operations in one or more intervals may be used to design
subsequent
operations for other wells drilled in the same or similar underground
formations. By
virtue of treating and measuring a single interval of the formation at a time,
variations
between the zonal response to the performed treatment and zonal properties
(determined
from the logging data, for example) may be detected. For example, the
combination of
the data obtained during the single-point fracturing operation may yield zonal
mechanical
properties such as Young's modulus, Poisson ratio, in situ stresses, including
minimum in
situ stress, mineralogy composition, hydrocarbon content, rock density,
resistivity,
particulate emission factor (PEF), and the like. Gathered data may be
interpreted using
computer-based systems in some embodiments, including commercially available
software packages such as fracCADE available from Schlumberger, Petrel,
Advanta, and
the like.
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[0021] Performing multi-stage single-point fracturing to prepare a
sequence of
clusters in a wellbore may be useful as a diagnostic operation in some
embodiments, and
may be used to acquire information on formation response to a given treatment
based on
the composition of a particular zone or interval. The data may then be used to
tailor or
optimize future treatment for additional wells that may be stimulated using a
single-point
treatment methodology or any other stimulation technique. In other
embodiments, data
obtained through the multi-stage single-point stimulation of a wellbore may be
used to
design completion strings and stimulation jobs for use in subsequent wellbores
in the
same formation or formations of similar composition and physical properties.
[0022] In some embodiments, methods in accordance with the present
disclosure
may also be applied to wellbores and wellbore sections that are substantially
horizontal.
As used herein, a horizontal well may be interpreted as including a
substantially
horizontal portion, which may be a cased or completed open hole, wherein the
fracture is
transversely or longitudinally oriented and thus generally vertical or sloped
with respect
to horizontal.
[0023] Single-point fracturing in accordance with embodiments
disclosed herein
may involve pumping a fluid above the fracturing pressure of the formation to
be treated
through a single entry to the formation. The entry may be a perforation, a
valve, a sleeve,
or a sliding sleeve. Often sliding sleeves in the closed position are fitted
to the production
liner, and the production liner is then placed in a hydrocarbon-bearing
formation. The
sliding sleeves may be opened and closed by a coil-tubing (CT) mounted
shifting tool in
some embodiments. Tools equipped with sliding sleeves may also include one or
more
packers that may be set below an opened sleeve providing a seal between the
operating
sleeve and other sleeves below. During operation, treatments may be performed
by
pumping fracturing fluid either down the annulus between CT string and
wellbore tubular
(e.g. casing) or by down the CT string or both.
[0024] In some embodiments, the sleeve or device controlling the
treatment opening
is activated by an object, such as a frac ball or dart, which is introduced
into the wellbore
from surface and the object is transported to the target zone by the flow
field or
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mechanically, for example, using a wireline or coiled tubing. When at the
target location,
the object is caught by the sliding sleeve or device and shifts the sleeve to
the open
position. The object remains in the sleeve, obstructing hydraulic
communication from
above to below. A fracture treatment is then circulated down the wellbore to
the
formation adjacent the open sleeve.
[0025] In some embodiments, a sealing device, such as a packer or
cups, may be
positioned below a sleeve on a completion string in order to isolate the lower
portion of
the wellbore. During operation, the sealing device is set and fluid is pumped
into the
fracture. Once pumping is completed, then the sealing device is unset and
moved below
the next zone (or sleeve) to be treated. Representative examples of sleeve-
based systems
are disclosed in U.S. Patent No. 7,387,165, U.S. Patent No. 7,322,417, U.S.
Patent No.
7,377,321, U.S. Patent No. 2007/0107908, U.S. Patent No. 2007/0044958, U.S.
Patent
No. 2010/0209288, U.S. Patent No. 7,387,165, U.S. Patent No.2009/0084553, U.S.
Patent No. 7,108,067, U.S. Patent No. 7,431,091, U.S. Patent No. 7,543,634,
U.S. Patent
No. 7,134,505, U.S. Patent No. 7,021,384, U.S. Patent No. 7,353,878, U.S.
Patent No.
7,267,172, U.S. Patent No. 7,681,645, U.S. Patent No. 7,066,265, U.S. Patent
No.
7,168,494, U.S. Patent No. 7,353,879, U.S. Patent No. 7,093,664, and U.S.
Patent No.
7,210,533, which are hereby incorporated herein by reference.
[0026] In one or more embodiments, methods in accordance with the
present
disclosure include well completions in which a zone of a first well is
stimulated using
single-point fracturing techniques; acquiring data from the completion of the
first well;
interpreting the data; and using the data optimize the design for subsequent
operations
such as the completion and stimulation of additional wells. With particular
respect to
FIG. 1, an embodiment of a possible workflow is shown. The method may begin at
100
by establishing an initial reservoir model by obtaining the initial parameters
of the
wellbore, which may be obtained by logging a wellbore through use of dedicated
logging
tools or drill string equipped for logging-while-drilling (LWD). Information
from the
wellbore may then be compiled and used to design an appropriate completions or
treatment operation for the well.
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[0027] At 102, a multi-stage treatment is designed based on the
generated reservoir
model and executed on distinct zones of the well using a single-point
treatment
methodology. At 104, data gathered during single-point treatment, which may
include
production and flowback data, may be used to determine the effectiveness of
the
treatment. If necessary, the collected data may also be used to update the
reservoir model
to account for changes from fracturing or the presence of natural features
such as faults,
zonal variations, etc. At 106, the collected data is mapped to the logging
data from the
wellbore and used in 108 to design, execute, or evaluate subsequent wellbore
operations.
Subsequent operations may include, for example, drilling and landing
additional wells,
cementing jobs for another wells, planning treatments for other wells in the
formation,
flowing back into another well, or determining production parameters for
another wells.
[0028] With respect to FIG. 2, a flowchart showing a method for
executing the
single-point fracturing technique in accordance with embodiments of the
present
disclosure is shown in which completions operations may be finalized prior to
initiating
the multi-stage single-point fracturing operation. Once a well site is
selected, an operator
may begin at 202 by drilling a well having at least one substantially
horizontal trajectory
while logging the well using logging-while-drilling or logging the well in a
separate
operation subsequent to drilling. The wellbore is then completed at 212 using
techniques
that are compatible with subsequent operations utilizing a single-point
methodology.
[0029] The logging data 204 obtained is then used to develop and
supplement an
initial reservoir model 200 at 208. The initial reservoir model may in some
cases be
generated from existing data known for the formation. The updated reservoir
model 210
is then used to design a multi-stage treatment using single-point fracturing
methodologies. Next, at 214, a multi-stage treatment is designed on the basis
of the
logging information and executed on a plurality of distinct zones of the well
at 218.
Following treatment using single-point fracturing techniques, the operation
may proceed
by optionally initiating flow back into the well 222, e.g., after the
injection of a chemical
tracers, to obtain flowback data 224 regarding the fracture flow performance
and the frac
fluid returning from various stages in the multi-stage treatment. In some
embodiments,
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optional production from the well may also be initiated at 226 following
treatment or
after testing flowback of the well in order to generate production data 228.
[0030]
Next, at 230 dependencies may be established by comparing the logging data
304 and at least one of the treatment data 220, the flowback data 224, and the
production
data 228 obtained after single-point fracturing treatment. The dependencies
obtained
from the comparison of the available data may then be used in a number of
subsequent
operations in the same or other wells, including, but not limited to, drilling
and landing,
cementing operations, additional fracturing or refracturing treatments,
flowback
operations, and production.
[0031]
With particular respect to FIG. 3, a more detailed flowchart showing a
method for executing the single-point fracturing technique is shown. Once a
well site is
selected, an operator may begin at 302 by drilling a well and logging the well
using
logging-while-drilling or logging the well in a separate operation subsequent
to drilling.
The logging data 304 obtained is then used to develop and supplement an
initial reservoir
model 300 at 306. The initial reservoir model may be generated from existing
data
known for the formation in some cases. The updated reservoir model 308 is then
used to
design a multi-stage treatment using single-point fracturing methodologies.
[0032]
In a next possible step 312, a completion string adapted for multi-stage
fracturing is designed to fracture one or more intervals of the formation at
314 prior to
performing single-point fracturing on a plurality of distinct zones of the
well. Where
completions operations have already finished, an operator may move directly to
318 and
initiate the process of designing the multi-stage treatment using a single-
point fracturing
methodology.
Following treatment using single-point fracturing techniques, the
operation optionally may proceed by initiating flow back into the well 322,
e.g., after the
injection of a radioactive tracer, in order to obtain flowback data 324
regarding the fluid
conductivity throughout the near-wellbore formation. In some embodiments,
optional
production from the well may also be initiated at 326 following treatment or
after testing
flowback of the well in order to generate production data 328.
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[0033] Next, at 330, dependencies may be established by comparing the
logging
data 304 and at least one of the treatment data 320, the flowback data 324,
and the
production data 328 obtained after single-point treatment. The dependencies
obtained
from the comparison of the available data may then be used in a number of
subsequent
operations in the same or another wells, including, but not limited to,
drilling and landing,
cementing operations, additional fracturing or refracturing treatments,
flowback
operations, and production.
[0034] Methods in accordance with the present disclosure may include
the drilling a
well prior to or during the logging of the well. Indeed, mud logging or
logging while
drilling, or subsequent logging operations may be used to define formation
characteristics
for at least one section of the drilled well as a function of depth. In one or
more
embodiments, well logs may be obtained through well logging techniques that
are
routinely employed including logging-while-drilling (LWD), by analyzing
cuttings
suspended carried to the surface by drilling fluid, or by using a memory
logging tool (or
real-time logging tool) that may be pumped down the drillstring after drilling
the well to
some target depth and then be retrieved to the surface with a drill bit
assembly (e.g., the
Thrubit service commercially available from Schlumberger). In some
embodiments,
formation characteristics may be acquired after drilling by using open-hole
logs such as
resistivity logs, gamma-ray logs, density logs, neutron logs, photoelectric
index logs,
image logs, sonic scanner, cased-hole logging techniques such as the Sonic
ScannerTM
acoustic scanning platform commercially available from Schlumberger, induced
resistivity logging, and other available well logging techniques.
[0035] It is noted that information for many formations may already be
available
from previous drilling information, and may be utilized to perform single-
point fracturing
based on existing data without the need for additional drilling. Results of
the evaluation
may also be combined with information relevant to the drilled well and
obtained from
other sources, such as seismic data, formation, and rock properties defined
from offset
wells and pilot holes, and the like.
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[0036] Methods in accordance with the present disclosure may include
completing
at least one section of a drilled wellbore with a completion string that
enables performing
a single-point treatment sequence on that section of the well. In one or more
embodiments, the completion string may be casing (cemented or including
packers such
as swellable packers). The casing may also include single-point fracturing
ports such as
sliding sleeves, burst-disks, or any other devices to create a single-point
opening in a
completion to establish communication with the formation. The formation
characteristics
involving post treatment may also be used after the completion, for example,
using cased
hole logging after completing the well with a completion string, e.g., Sonic
ScannerTM,
induction logging, and the like.
[0037] Once the well logging data is obtained from evaluating a given
zone, a
reservoir model may be constructed and updated as additional logging data for
the
formation is obtained. In one or more embodiments, the reservoir model may
then be
used to design a multi-stage single-point treatment for at least three
sequential zones
contained in one or more sections of a first drilled well. Such a treatment
design may be
based on usage of updated formation model or results of evaluation of the
collected zonal
information as discussed above. In one or more embodiments, a multi-stage
single-point
treatment may be designed on pre-determined zonal characteristics that allow
an operator
to select zones to be treated or avoided.
[0038] In one or more embodiments, single-point fracturing treatments
may be
performed to enable access to the target formation zones. In some embodiments,
the first
step may be to create a single perforating cluster on the tubing or casing
string. For
example, the perforating cluster may be created using a perforating gun, a
jetting tool,
casing cutting, sawing, filing, laser perforating, and the like. In some
embodiments, the
cluster is already present in the tubing such as when involving a sliding
sleeve system, in
such instance the sleeve is active or shifted to be in an open position.
Fracturing fluids
may be pumped down above the fracturing pressure in some embodiments, and may
include viscosified hydraulic fracturing fluid, slick water, foam, energized
fluid, fluid
containing viscoelastic surfactants (VES fluids), linear gels, crosslinked
fluids, gelled
acid, gelled oils, liquefied gas, in-situ channelization fluids, and the like.
Fracturing
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treatments in accordance with the present disclosure may also include proppant
stages
wherein proppant may be sand, ceramic glass beads, mica, and the like.
[0039] In some embodiments, the treatment fluid may be pumped into the
target
zone below the fracturing pressure. For example, chemical fracturing
treatments may be
applied at or below fracturing pressure and may include matrix acidizing
treatments such
as hydrochloric acid, citric acid, acetic acid, and mud acid; chelating
agents; scale
inhibitors, and the like. Treatment fluids in accordance with the present
disclosure may
also include friction reducers, clay stabilizers, biocides, crosslinkers,
breakers, corrosion
inhibitors, and/or proppant flowback control additives. The treatment fluid
may further
include a product formed from degradation, hydrolysis, hydration, chemical
reaction, or
other process that occur during preparation of the treatment fluid or during
the fracturing
operation.
[0040] Treatment fluids in accordance with the present disclosure may
also be
modified to obtain additional formation related parameters. In one or more
embodiments,
the treatment design may include injecting tracing agents including
radioactive and
chemical tracers into the formation and measuring the rate of return of the
tracing agent
as a method to define the effectiveness of the treatment. For example, tracers
may be
complexes of radioactive materials such as rare earth metals that are injected
in various
zones in order to evaluate flowback and production performance of the zones
through
radiometric analysis of fluids as they flow back from the formation.
[0041] In one or more embodiments, the treatment designs may further
include
diagnostic tests to improve analysis of formation characteristics. Examples of
such
diagnostic tests are injectivity tests performed above and below fracturing
pressure,
drawdown tests, cycled injections/drawdowns, formation breakdown, step-up rate
test,
step down tests, flowback and pressure rebound tests, calibration injections
with
registration of pressure decline, injection of "calibration slugs of solids,"
and the like.
[0042] After the treatment fluid has been pumped, the single-point
treated zone is
then isolated and access to the following zone in the sequence is enabled.
Here again,
perforation may be made or the next sleeve may be opened. Various techniques
may be
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used. In embodiments, a coiled tubing (CT) is used to open a CT actuated
fracturation
sleeve in the next zone, still involving a sealing element to be set through
or below the
sleeve to be treated. In embodiments, the previous zone that was treated is
isolated using
for example bridge plug, ball sealers, sand plug, or by pumping zonal
isolating bridging
material such as particulates, fiber, flakes, and combination thereof.
[0043] In one or more embodiments, treatment fluids may also be
modified between
zones to optimize data gathering or to obtain different data from the
formation. For
example, a sequence of clusters may be designed such that a first single-point
fracture
and data collection is performed using a first treatment formulation or
condition, and
when the sequence progresses to the next region of interest, a second
treatment or
condition is used during the fracturing operation. While such approaches may
find utility
for treating formations containing zones of differing composition and physical
characteristics, it is also envisioned that such an approach may be useful for
diagnostic
purposes in a formation having a homogenous composition and structure to assay
optimal
treatment conditions by varying treatments in a sequence of clusters. In some
embodiments, multi-stage single-point treatments may be repeated in additional
zones or
other wells of similar composition until sufficient confidence of the accuracy
of the data
has been established.
[0044] In addition to modification of the treatment between clusters
in a sequence,
the spacing between the clusters may also be used to modify the design of the
completion
string in some embodiments. The space between single-point clusters, or
sleeves in a
wellbore may be arranged geometrically, for example, at an equidistant spacing
that is
every 50 feet, every 20 feet, every 10 feet, or every 2 feet. In some
embodiments,
geometric spacing of the clusters may be used in the event that the available
data sets do
not provide sufficient data regarding formation composition, where the
formation is
homogeneous, or where time is a constraining factor. In some embodiments,
clusters
may be placed according to pre-determined engineering criterion, at non-
equidistant
spacing, including placing clusters where it is anticipated that formation
intervals will
have similar or different mineralogy, near regions of general interest, or at
intervals
determined to be maximal production targets. For example, a multi-stage single-
point
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fracturing job may be designed such that clusters are spaced within zones
having
different composition in order to assay the efficacy of a particular treatment
on the type
of rock or structure in the zone.
[0045] Multi-stage operation may occur in the same well or in other
wells. In some
embodiments, experimental treatments may be applied at varying points in the
well, or
alternatively the treatment may be repeated at several intervals to determine
the
heterogeneity of the response to treatment across intervals.
[0046] Single-point fracturing allows measurement before, during, and
after
fracturing operations, allowing greater control over the information obtained
from the
formation. Characteristics obtained for the formation may include mechanical
or
mineralogical properties, breakdown pressure, logging and comparison to
pressure data.
In one or more embodiments, treatment of a single-point fracturing zone may be
monitored using a number of measuring techniques in order to determine the
dependencies between defined formation parameters and the results for each
treated zone.
Depending on the type of a treatment, measurements may depend on the nature of
the
fracturing treatment and may include measurement of pressure level, maximum
injection
rate achieved, Instantaneous Shut In Pressure (ISIP), fracture geometry,
pressure
evaluation, and the like.
[0047] In some embodiments, measurements may include analysis of
bottomhole
pressure data, including bottomhole pressure calculated from "deadstring"
measurements,
in which the level of bottomhole pressure is compared to that of the treated
interval.
Real-time microseismic diagnostics may also be used wherein microseismic
events
generated during fracturing are registered to provide an understanding of the
position and
geometry of the fractured zone. Real-time temperature logging methods in which
distributed temperature sensors indicate the portion of a wellbore is being
treated, such as
fiber optic probes to measure the temperature profile during treatment, may
also be used.
In other embodiments, radioactive logging may be used in which a radioactive
sensor is
positioned in a wellbore prior running a treatment, and then detecting a
signal from
radioactive tracers added in the treatment fluid during the job. In yet
another
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embodiment, low frequency pressure wave (tubewave) analysis may be used to
monitor
fractures, obstacles in the wellbore, completion segments, etc., by measuring
the decay
rates and resonant frequencies of free and forced pressure oscillations to
determine the
characteristic impedance and the depth of each reflection in the well.
[0048] In some embodiments, additional monitoring techniques may be
used
including bottomhole pressure gauges including real-time measurements and
memory
gauges, using microseismic monitoring, tiltimetry, real-time logging including
temperature and gamma ray logging, monitoring pressure in surrounding wells
for
defining communication events, measuring fluid flow using in-line spinning
flowmeters,
and the like.
[0049] In one or more embodiments, measurements obtained from at least
one of
prior, during, or after single-point treatment may be used to establish
dependencies or
correlations between defined formation parameters and the treatment results
for each
affected zone. Examples of revealed dependencies may include: dependence of
formation breakdown pressure or any other treatment pressure parameters on
zone
mineralogy, mechanical properties, or zonal logging data; dependencies of
fracture
geometry on injection pattern; presence of natural fractures; dependencies on
leak off
coefficients defined during diagnostic tests on rock fabric characteristics
which may
include presence of natural fractures; zone permeability; and the like.
[0050] In one or more embodiments, information obtained from one or
more zones
of a primary well may be used to design post-job well logging operations in
the treated
primary well or the information may be used to refine designs for treatments
in
neighboring or other wells, including those in formations having similar
properties to
those observed in the first well. Some examples may include temperature
logging; this
may be used for defining fracture height (typically for vertical well
section); gamma ray
logging in the case of injection of a radioactive sand that, for example, may
be used for
defining fracture height, or gamma ray logging of neighbor wells for
establishing
injection pattern in the formation for example when radioactive tracers were
used.
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[0051] In embodiments, it may be decided to flow back the well with
analysis of
flowback fluid including analysis of tracer content in a returning fluid.
Flowback may be
combined with wellbore clean out, drilling out operation (e.g. when frac plugs
were used
for zonal isolation between stages), nitrogen injection for unloading the
well, workover
operation typically performed on a well after treatment completion. Analysis
of flowback
fluid may include salinity, chloride content, elemental analysis and other
parameters all
of which can be used for making conclusion about percentage of fluid return,
content of
formation fluid in the flowback fluid, fracture height (e.g. in the case of
presence of
elements in a flowback fluid which are specific to some formation layers).
Flowback
operation may also be combined with logging the well. One of the examples may
be
production logging done for defining individual zone flowback rates and
initial
production profile. Results of evaluation of information collected during well
flowback
period can be used for further update of the formation model, defining
dependencies with
the results of the performed treatment in a manner described herein.
[0052] Once completions are finalized, the well may be prepared for
production
operations. Production operations may include installation of production
string, change of
wellhead equipment, installation of production tree, installation of wellbore
equipment
(e.g., artificial lift equipment such as nitrogen/natural gas injectors or
electric submersible
pumps), and the like.
[0053] In one or more embodiments, post-flowback well logging of the
treated well
(or other wells), including production logging, may be used to generate
production data
that may reveal the relative success of the performed treatment. Production
data in
accordance with the present disclosure may be obtained by monitoring of fluid
flow rates,
including production rates, fluid composition, pressure including surface and
bottomhole
pressure, and the like.
[0054] Production operations may also be combined with logging
operations, such
as production logging, and may be performed on a treated well one or several
times to
define production rates and produced fluid composition for treated zones, in
addition to
any changes in production from treated zones. Production data logging in
accordance
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with embodiments of the present disclosure may also include defining
production profile
and fluid composition for each treated zone. Obtained production results may
define
dependencies between zonal production characteristics, previous formation
parameters
for each zone, treatment parameters, results of the performed treatment that
were defined
from post-treatment evaluation, treatment volumes, and the like.
[0055] Methods in accordance with the present disclosure may carry
advantages
over standard fracturing techniques in which multiple fracturing clusters are
generated in
a single operation, because single-point fracturing allows information from
the formation
to be gathered after each fracture stage, which in turn may be correlated with
logging data
obtained from the well. Thus, increased amounts of information regarding
formation
composition, formation pressure, and production volume may be gathered from a
single
well.
[0056] The skilled artisan will be able to tailor operations for a
further well to be
treated. Indeed, the data obtained through single-point fracturing and their
interpretation
will allow the skilled artisan to establish dependencies between formation
characteristics
of each treated zone, treatment parameters/achieved treatment results and
production
performance of each treated zone are further used for defining technical
recommendations for improving well performance for considered reservoir. Such
recommendations may include guidelines for zonal selection with the aim of
minimizing
treatment pressure or maximizing production performance or optimizing
treatment
economics; recommendations for volume and treatment schedule of a treatment
stage,
guidelines for well landing within formation, etc. Such another well can be
completed
and treated using single-point fracturing methodology or any other methodology
including "plug and perf' technology.
[0057] In one or more embodiments, data acquired by drilling,
completing, and
measuring data from a first well, may be used to enable a further optimization
of a
fracturing process. Indeed, using single-point fracturing and obtaining
relevant data for
establishing dependencies will help in the choice of fluid flow rate and
treatment fluid
composition. In addition, data acquired from single-point fracturing may
enable
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optimization of completion string design, because dependencies may be used to
optimize
perforation depending on the zone, which may in turn contribute to more
efficient
hydrocarbon production. Similarly, an operator may tailor the placement and
number of
fracturing ports on a completion string depending on data obtained from a
first diagnostic
well, which can minimize sleeve shifting time, manufacturing cost, and
fracturing fluid
consumption.
[0058] While the disclosure has provided specific and detailed
descriptions to
various embodiments, the same is to be considered as illustrative and not
restrictive in
character. Only certain example embodiments have been shown and described.
Those
skilled in the art will appreciate that many modifications are possible in the
example
embodiments without materially departing from the disclosure. Accordingly, all
such
modifications are intended to be included within the scope of this disclosure
as defined in
the following claims.
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