U.S. patent application number 13/919428 was filed with the patent office on 2013-12-19 for method for closed loop fracture detection and fracturing using expansion and sensing apparatus.
The applicant listed for this patent is Wajid Rasheed. Invention is credited to Wajid Rasheed.
Application Number | 20130333879 13/919428 |
Document ID | / |
Family ID | 39683278 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130333879 |
Kind Code |
A1 |
Rasheed; Wajid |
December 19, 2013 |
Method for Closed Loop Fracture Detection and Fracturing using
Expansion and Sensing Apparatus
Abstract
An expansion and sensing apparatus used to detect natural and
hydraulic fractures. In a closed loop aspect of the invention a
microprocessor may be incorporated to process data which identifies
natural fractures and optimises the coordinates for setting an
isolation device, hydraulically fracturing the formation,
identifying the effectiveness of the hydraulic fracture and if
required repeat the hydraulic fracture at the same co-ordinates or
select further co-ordinates in order to propagate an optimised
fracture pathway and maximise production. The apparatus may be used
with microseismic, tiltmeters, etc.
Inventors: |
Rasheed; Wajid; (Slough,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rasheed; Wajid |
Slough |
|
GB |
|
|
Family ID: |
39683278 |
Appl. No.: |
13/919428 |
Filed: |
June 17, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12966195 |
Dec 13, 2010 |
8511404 |
|
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13919428 |
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Current U.S.
Class: |
166/250.1 |
Current CPC
Class: |
E21B 7/28 20130101; E21B
47/09 20130101; E21B 47/085 20200501; E21B 47/12 20130101; E21B
43/26 20130101; E21B 47/095 20200501; E21B 10/322 20130101; E21B
47/08 20130101; B26B 21/54 20130101; E21B 44/00 20130101; A01N
43/40 20130101; E21B 47/01 20130101; E21B 47/00 20130101; E21B
49/00 20130101; E21B 33/124 20130101; E21B 10/32 20130101; A01N
43/40 20130101; A01N 37/20 20130101; A01N 37/22 20130101; A01N
37/26 20130101; A01N 43/10 20130101; A01N 43/12 20130101; A01N
43/20 20130101; A01N 43/78 20130101; A01N 43/80 20130101; A01N
43/82 20130101; A01N 47/12 20130101; A01N 47/16 20130101; A01N
47/38 20130101; A01N 57/14 20130101; A01N 2300/00 20130101 |
Class at
Publication: |
166/250.1 |
International
Class: |
E21B 43/26 20060101
E21B043/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2008 |
GB |
GB 0811815.0 |
Jun 27, 2009 |
ES |
PCT/ES2009/070261 |
Claims
1. An apparatus (50) for fracturing an oil or gas well comprising a
sensing element, means for attaching the sensing element to a
support whereby it can be moved in a borehole (20), characterized
by, at least one sensor (58), to detect a fracture or a feature of
the formation related to a fracture, at least one expandable
element (52)
2. The apparatus of claim 1 wherein said sensing element detects a
fracture or a feature of a formation related to a fracture in order
to generate an optimal location to set the expandable element in
real-time
3. The apparatus of claim 3 further comprising expanding the
expandable element in response to sensor data acquired by the
sensing element.
4. The apparatus of claim 1 wherein downhole sensors are used to
sense said fractures or fracture features
5. The apparatus of claim 1 wherein surface sensors are used to
sense said fractures or fracture features
6. The apparatus of claim 1 wherein said sensors are one of the
group selected from: resistivity, neutron density, nuclear magnetic
resonance, acoustic, wellbore imaging, seismic, micro-seismic,
tilt-meters, pressure, flow, temperature, stress, strain
7. The apparatus of claim 1 wherein said expandable element is
selected from one or more of the group of: plugs, packers,
elastomers, sponges, metals, porous material, non porous material
and effectively isolates or communicates with at least one zone of
the formation
8. Apparatus of claim 1 wherein the expandable element expands
under mechanical force, temperature, pressure, flow or other force
acting against it from the inside of a wellbore or from the inside
of the support.
9. Apparatus of claim 3 wherein the expandable element is expanded
on command in response to sensor data.
10. Apparatus of claim 4 wherein the expandable element is expanded
on command in response to sensor data.
11. Apparatus of claim 1 wherein the sensor is locatable above or
below the expandable element
12. Apparatus of claim 8 wherein the sensor is retrievable and has
an unrestricted internal diameter communicable to the expandable
element
13. Method of claim 20 wherein a fracture is detected by sensor,
the expandable element is expanded on command in response to sensor
data and a fracture is induced
14. Method of claim 15 wherein the induced fracture is detected by
sensor
15. Apparatus as claimed in claim 1 with sensors and expandable
elements configured with a wall contact member FIG. 5 (62) wall
contact member (63) at the trailing uphole or leading downhole
end
16. Apparatus of claim 17 wherein such downhole wall contact member
may form part of a rotary steerable, stabilizer, roller reamer, a
reamer, a pressure containment device, a measurement device, a
bridge plug, a packer and inflow control device.
17. Apparatus as claimed in claim 19 which is elongate and
comprises at least two of said expandable elements at
longitudinally separated positions along the support, (FIG. 7,
61)
18. Apparatus as claimed in claim 1 comprising microprocessor
control means (55) adapted to receive data on the formation or
formation features based on acoustic signature velocities
recognized by receivers (52), detect a formation or formation
feature and signal a tool in response to acquired data in order to
set the expandable element to maximize production.
19. Apparatus as claimed in claim 1 wherein a plurality of sensing
elements are directed outwardly of the tool to form a sensing zone
wherein said plurality is placed helically, longitudinally,
spirally, axially, radially and communicate with a user interface
in real-time so as to optimize performance.
20. An automated method of operating a fracturing apparatus to
optimally place a wellbore or tubular or packer or sand screen or
like completion or production system or device based on acquired
formation data, which comprises locating a tool as claimed in claim
one in a borehole, activating the sensing element to send and
receive formation data, rotating the tool and moving it axially
along the borehole on the drill-bit or support, receiving data by
receiver means, and continuing the formation evaluation until an
optimal fracking operation is achieved using logic programming to
diagnose and correct common errors or failures.
21. A method of fracturing using apparatus as claimed in claim 1
provided with a closed-loop micro-processor means for detecting a
wellbore feature or detecting a natural fracture or an induced
fracture, comparing this with a desired fracture and automatically
alerting an operator or changing the condition of an expandable
element in response thereto (62) and wherein the tool is supported
on a downhole string (40) and a surface interface controls and
exchanges data with the downhole string and any of its components
during the formation evaluation operation according to a program to
deliver a desired wellbore placement.
22. A method of completing an oil or gas well as claimed in claim 1
where the apparatus gives immediate evaluation of a formation, or
the characteristics of a formation yet to be drilled and, if the
tool detects a feature of a formation or a change in a feature of
interest, to automatically calculate and correct for an optimal
well path, and to repeat evaluation until such an optimal well path
result is achieved in real-time where formations are detected as
rock types, earthen formations or lithologies with a feature of
interest meant to include but not limited to detecting porosity or
a change in porosity, detecting permeability or a change in
permeability, an oil zone, a gas zone, a water zone, a fracture, a
fault, a dip, a bed, a vugular formation, an anticline, a syncline
and a trap.
Description
FIELD OF THE INVENTION
[0001] This invention relates to an apparatus and method capable of
detecting fractures and expanding a tubular or wellbore isolation
device in oil and gas wells. The expandable elements can be
configured to expand to the actual wellbore diameter while sensors
such as acoustic sensors or mechanical probes can detect wellbore
fractures. Further measurements can be obtained after expansion and
used in conjunction with fluid properties, vibration, flow,
hydraulic force, pressure, temperature.
[0002] It is to be understood that the term `expansion` as used
herein refers to the capacity of the expandable element to expand
outwardly and against the interior wall of a passage, such as a
borehole, especially a wellbore, or a tubular used as a casing, and
then to maintain pressure or isolate pressure from the formation.
It is not always essential that the expandable element such as a
bridge plug or packer be expanded, since the sensing elements can
be used to detect fractures without necessarily expanding the
packer.
[0003] The invention relates to an Expansion and Sensing apparatus
and method for identifying natural fractures and optimising the
process of man-made or hydraulic fractures in oil and gas wells.
The technology is especially useful in unconventional reservoirs
that hold tight gas, shale gas, coal bed methane, shale oil, etc.
If critical knowledge of the fracture i.e. reservoir
interconnectivty, fractures, pathways or dips can be gained both
pre and post fracking this would lead to greater recovery rates due
to more effective wellbore fracking by increasing the actual
fracked footage in the payzone. The invention is suitable for open
and cased/liner hole and hydraulic fracturing with or without
perforating tubing.
[0004] The apparatus and method is capable of evaluating natural
fractures to determine optimal depths and locations to set an
expandable element such as packers or other wellbore isolation
devices so as to optimise the fracture pathways that are naturally
present once the wellbore is isolated and the man-made or hydraulic
fractures can be propagated. The apparatus and method finds
particular use in characterising fractures and their geo-physical
and petro-physical features principally using sensors or wellbore
imaging based on electrical, ultrasonic, electromagnetic or nuclear
measurements to characterise the fracture and wellbore isolation
devices using expandable packers, swellable packers, intelligent
control valves, intelligent control devices. Alternative means can
be used to identify the fracture and isolate the wellbore. Any type
of fracturing method itself can be employed in the invention and
this is not limited to hydraulic fracturing, as different types of
reservoirs may require the use of differing methodologies or new
fracturing techniques.
[0005] In a closed loop aspect of the invention a microprocessor
may be incorporated to process data which identifies natural
fractures and optimise the coordinates for setting an isolation
device, hydraulically fracturing the formation, identifying the
effectiveness of the hydraulic fracture and if required repeat the
hydraulic fracture at the same co-ordinates or select further
co-ordinates in order to propagate an optimised fracture pathway
and maximise production.
[0006] On average, 65% of hydrocarbons are left underground this
equates to a recovery rate of 35%. Unconventional reservoirs often
have as many as 10 stages requiring fracturing. An optimized
fracture method and apparatus would potentially help increase
recovery rates. It is to be understood that the term `fracture` as
used herein refers to the capacity of the invention to evaluate an
aperture in the formation which may vary in size from millimetres
to metres, have a determined angular orientation and may connect to
other fractures in the same plane or another plane within a
formation that extends from the tool at a determined angle and
reaches a given angular depth and a true vertical depth.
[0007] In contrast, prior art logging tools are differentiated as
part of a separate function i.e. are tripped out of the hole and a
fracking assembly entered into the hole. In the prior art, once a
fracking assembly is located, neither a sensor nor an imaging tool
capable of detecting fractures is in communication with the
fracking operator due to the complex downhole configuration of
fracking and the location of the fracking stages. The technology
overcomes these issues by providing pre and post fracking data and
can also be configured with wellbore isolation devices and may be
configured so as to be retrievable through a packer to determine
the effectiveness of a frack job or a frac stage. It can be run
with a rotary steerable to detect fractures but it is not necessary
for fracking to occur using wellbore isolation devices conveyed on
drill pipe. An expandable element and fracture sensor to determine
natural fractures before formations are hydraulically fractured and
thereby increase hydrocarbon recovery factors by optimally setting
the wellbore and the wellbore isolation device such as a packer; a
method of closed loop fracture identification, fracking and
identifying frack effectiveness.
[0008] In one embodiment the present apparatus and method itself
overcomes these issues by providing pre and post fracking data and
can also be configured with wellbore isolation devices and may be
configured so as to be retrievable through a packer to determine
the effectiveness of a frack job or a frac stage. In another
embodiment the invention is configured with a rotary steerable to
detect fractures but it is not necessary for fracking to occur
using wellbore isolation devices conveyed on drill pipe.
[0009] Other aspects of the invention include a method of operating
an expandable element and fracture sensor to determine natural
fractures before formations are hydraulically fractured and thereby
increase hydrocarbon recovery factors by optimally setting the
wellbore and the wellbore isolation device such as a packer; a
method of closed loop fracture identification, fracking and
identifying frack effectiveness, identifying fractures, angularly,
axially and vertically ahead of hydraulic fractures; a method of
pre and post frac analysis using a closed loop system, creating a
an optimised sensing zone. In a further aspect, the invention
relates to an apparatus for controlling logging and wellbore
placement in real-time. The invention may also be combined with
micro-seismic, tiltmeters, frac tracers, proppant, or sensing of a
frack parameters such as flow, pressure, temperature, depth,
azimuth, inclination to provide insight into the fracking
process.
[0010] When deciding the optimal trajectory and placement of an
exploration or production well and its completion, numerous
downhole activities are conducted to ensure the highest recovery of
hydrocarbons and minimise the production of water over the well's
life-span. Geo-physical data such as formation porosity,
permeability, oil, water, gas contact zones, formation beds and
dips are required to be known to steer the well to its optimal
location. A variety of logging-while-drilling technology such as
neutron density, gamma ray, resistivity and acoustic investigation
tools are commonly used to identify formations and evaluate their
features. (FIG. 1).
[0011] For unconventional wells, the present invention provides
insight into natural fractures and their interplay with hydraulic
fractures. Many considerations affect the fracture matrix such as
organic content, porosity, permeability, brittleness, orientation,
pressure but as a general rule, because hydraulic fractures
propagate along the path of natural fractures, detecting natural
fractures is most useful in enlarging and stabilizing the natural
fracture matrix. Although, many fractures appear closed in cores,
markers i.e. differing properties from the surrounding rock such as
pressure, impedance, calcite lining, etc provide clues to their
detection. Consequently, the invention would enable oil companies
to maximise production by pin pointing natural fractures while
drilling, feed these into the fracture matrix and complement micro
seismic, tiltmeter, frac tracers, proppant effectiveness etc. Thus
the invention embodies a truly optimised closed loop method for
open hole/cased hole completions using packers or sleeves. Further
embodiments may determine fracture detection on the open hole
completion or stimulation string where a perforating string is
involved suitable reconfiguration of the technology.
[0012] The present invention details an embodiment of a sensor to
detect a fracture. As is known in the art, fractures may be derived
from a variety of formation evaluation data which comprise
acoustics, electro-magnetics, resistivity or conductance
measurements, neutron density, alpha particle measurements,
photoelectric measurements, gamma ray. In fact any type of sensor
that can detect a fracture is useful in the invention.
Alternatively or additionally a wellbore image may be provided.
[0013] Several types of sound based investigation sensors exist
such as passive seismic that record natural seismic events, active
seismic that generate and register sound waves from man-made
sources and those known as acoustics (below 20,000 Hz) and those
known as ultrasonic (above 20,000 Hz). It is understood that the
term `acoustic` covers ultrasonic, sonic and other frequencies.
[0014] Seismic tools provide wide-scale geological data, however
these have poor resolution of formation detail and drilling itself
is the true test of geophysical formation characteristics.
Therefore, there is a need for and reliance on real-time acoustic
while drilling tools. These tools use transducers or sources to
create high frequency sound waves which are propagated as shear or
pressure waves in solids and fluids respectively. Sound waves are
further classified as those travelling within the wellbore
(Stoneley waves), the near formation as (Flexural waves) and far
formation as (Body waves). Through an evaluation of the echo pulse,
its maxima and minima, which are received back by the
sensor/receiver, and derivations thereof, calculations, can be made
as to the time interval between signal transmission and recording
the echo to determine the distance to an object or formation
feature. Further, using algorithms various characteristics such as
formation density, void spaces, fluid saturations, fluid trapping
and formation direction changes such as beds or dips all have
definite signature velocities that correspond to their reflective
ability.
[0015] In all of these applications, the prior art suffers from two
major limitations namely a lack of pre and post frack data (FIG. 2,
90, 100) and the integration thereof. Firstly, sensor and natural
fracture data is not always available to set the packer in a timely
manner based on fracture evaluation (100). The discontinuity (100
feet or more) between sensors and the packer leads to a trial and
error approach.
[0016] Second, the effectiveness of the frack job is not determined
as the prior art may not be deployed below the packer or may not be
retrievable through the packer to determine the orientation and
propagation of the hydraulic fractures (90). This severely limits
the ability to repeat the frack job to allow for perforation,
fracture propagation and proppant to be pumped through (FIG. 2). In
this way, the prior art can only provide for formation evaluation
subsequent to drilling. This is unsatisfactory as it prevents the
optimal placement of the packer and the wellbore due to the
non-existent or tardy arrival of formation data after wellbore
placement has already occurred.
[0017] Measurement may involve the acquisition and communication to
surface of various types of wellbore data such as resistivity,
porosity, permeability, azimuth, inclination and borehole diameter
or rugosity, formation dips or bedding angles. Such measurements
are known in the art and in the interest of brevity therefore are
shown conceptually only.
[0018] In the event of a productive hydrocarbon bearing zone having
been unsuccessfully fractured (bypassed or exited or simply not
fractured), there is a missing step between the data showing where
the hydrocarbons are located and the subsequent production. Often,
the missing step leads to uncertainty, additional cost and can be
accompanied by a loss of production as hydrocarbons are bypassed or
the optimal fracking stage configuration within a low permeability
zone is lost. In the case of productive zones, characterization
using wireline or micro-seismic occurs after fracking, once the
assembly has been tripped out of the hole and the area has been
traversed.
[0019] The present invention may be suitably combined with
microseismic, tiltmeters etc to provide inferred or indirect or
direct measurements where the invention provides the detail for the
fracture pathways that are necessary for production. In the prior
art this means that the payzone of the reservoir may be exited and
further corrective fracking or drilling must occur to place the
wellbore in the desired productive state. Such cycles of delayed
post fracture data arrival and subsequent corrections can be
eliminated with the present invention.
BACKGROUND OF THE INVENTION
[0020] To those versed in the art, it is known that over geological
time, ancient river systems carried and deposited millions of
tonnes of sediment and organic matter as they ran their courses to
river outlets, deltas or gulfs. Over time, continuing deposits
eventually formed numerous layers of sedimentary rock. These were
pushed deeper and deeper under the seabed. Each successive layer
(younger deposits) increased the pressure on earlier layers (older
deposits) and tectonic plate movement deformed the layers creating
folds, hills (anticlines) valleys (synclines), unconformities
(eroded areas), faults and traps. Time, pressure and heat converted
the decomposed marine life into elemental hydrocarbons. Within a
given rock structure, the younger deposits or later layers form
`overburden` pressure conditions. Additionally, each layer has a
given temperature profile according to the True Vertical Depth
(TVD) at which it is located. These factors combine to form oil and
gas deposits in certain rocks known in the art as `source-rock`,
which can often be seen in certain oil and gas provinces in
outcrops. From their origins deep within the source beds,
hydrocarbon molecules are squeezed by immense pressures caused by
the overlying sediments similar to water from a sponge. They
migrate to water-saturated porous and permeable beds where, being
lighter than water, they start to rise. As they rise, they contact
other hydrocarbon molecules and coalesce into droplets that keep
rising until they encounter an impermeable layer known in the art
as `a cap rock`. There, they accumulate, forming a reservoir.
[0021] To those skilled in the art, the three rock classes--source,
reservoir and cap--explain two concepts. Firstly, the sedimentary
process explains why oil and gas are contained in minute rock
spaces or pores (porosity) and not in caverns. This can be imagined
as a dry sponge placed over water. The water is drawn in and
contained within the voids of the sponge. To those skilled in the
art, porosity is defined as the percentage of `voids` in a volume
of rock. Secondly, sedimentation shows the ability of a fluid to
`seep` or `flow` through a given formation (permeability). Minute
channels are created in the formations and, due to the pressurised
nature of oil and gas and their relative lightness, there is always
a tendency for the oil and gas to rise. This is illustrated by the
migration of oil and gas from a source rock to a porous reservoir
rock.
[0022] Such oil and gas accumulations are therefore contained in
highly complex structures which are found at varying depths in
different geological basins worldwide. Exploration and production
of such accumulations relies on the construction of a well
according to a well plan which is itself based on calculations and
assumptions derived from scarce data and similar offset wells.
[0023] Various well types exist and are defined according to usage
such as wildcats or those used in exploration; delineation; and
production and injection. Variations in well profile exist also
according to vertical, slant, directional and horizontal
trajectories. Each differs according to the oil company's
objectives and the challenges that a given basin presents from the
surface of the earth or the ocean to the hydrocarbon reservoir at a
given underground depth.
[0024] Geological mapping and geophysical surveys allow oil
companies to characterise their acquired acreage and the age and
sedimentation patterns of the rock formation contained therein.
This process of characterisation can be reconstructed as a visual
earth model that delineates the position and shape of the structure
including anticlines, faults-stratigraphy, structure which helps
increase production from subsequent wells and from the field as a
whole. However, the earth model and the well plan have inherent
uncertainties.
[0025] Geological uncertainties and challenges are related to the
location of the hydrocarbons, water contacts, traps, formation
stresses, movements and reservoir porosity and permeability. To
overcome these challenges, a highly detailed well plan is developed
which contains the well objective, coordinates, legal, geological,
technical and well engineering data and calculations. To resolve
the uncertainties, however, drilling is the final test.
[0026] The data is used to plot a well profile using precise
bearings which is designed in consecutive telescopic
sections--surface, intermediate and reservoir. To deliver the well
objective and maintain the integrity of well over its lifecycle, a
given wellbore trajectory with multiple sections and diameters is
drilled from surface. Although there are many variants, a simple
vertical well design could include a surface or top-hole diameter
of 171/2'' (445 mm), intermediate sections of 135/8'' (360 mm) and
95/8'' (245 mm) narrowing down to the bottom-hole diameter of
81/2'' (216 mm) in the reservoir section.
[0027] Each consecutive section is `cased` with the specified
diameter and a number of metal tubes placed into the wellbore
according to the length of the section. Each must be connected to
each other after which they are cemented into the appropriately
sized hole with a given tolerance. In this way, a well is
constructed in staged sections, each section dependent on the
completion of the previous section until the well is isolated from
the formation along the entire distance from surface to the
reservoir. Each section will also have a logging plan with minimum
formation evaluation requirements. In a similar way, the reservoir
section is left open hole or bare or completed using production
casing, sandscreens, gravel packs etc. Production casing fully
isolates the wellbore from the reservoir formations and therefore
requires communication which is provided via perforations created
in the casing allowing fluid commingling. Perforations are of
further importance in unconventional basins as they provide the
coordinates for the hydraulically induced fractures.
[0028] Scarcity of oil and gas is driving oil and gas companies to
explore and develop reserves in unconventional basins such as those
known as tight gas, shale gas, shale oil and coal bed methane.
Unconventional reservoirs are those whose permeability is far lower
than conventional oil and gas reservoirs as the oil and gas is
essentially trapped due to a lack of permeability. The completion
method known as fracking, fractures the reservoir liberating the
hydrocarbons from their tight earthen structure. These wells are
highly dependent on fracture pathways to ensure that permeability
is achieved to allow hydrocarbons to flow from the reservoir.
[0029] Therefore, the well plans that are used to drill these wells
may include modeling or fractures using micro seismic, tiltmeters,
acoustic, resistivity or other logging devices to characterize
natural fractures. In this way, modeling is an integral part of
fracture construction and there is now an increased dependence on
modeling for wellbore fracture placement.
[0030] Previously, the fracture detection has been restricted to
natural or pre frack measurements which are often modeled only.
Typically, the natural frack data means that modeled fracture data
would be provided before a fracking operation and may or may not
have microseismic applied. Consequently, the fracking operation may
have exited a payzone and the fracking would be of limited
effectiveness. A new well may have to be drilled to reach back to
the optimal location or the fracking operation repeated. If
critical knowledge of the fracture i.e. reservoir
interconnectivity, fractures, pathways or dips can be gained both
pre and post fracking this would lead to greater recovery rates due
to more effective wellbore fracking by increasing the actual
fracked footage in the payzone.
[0031] In other applications such as gas zone, kick detection, pore
pressure analysis or fracture identification, the tolerances
between the planned parameters and actual downhole parameters can
be very close and variations of 0.2 ppg can lead to the failure or
loss of the well. By being able to detect a kick, or establish a
fracture before it is actually drilled through, remedial drilling
action can be taken in advance saving time, money and providing a
significant safety margin.
[0032] To those skilled in the art, it is known that the industry
relies on modeled data which may not incorporate direct downhole
fracture detection whether pre or post fracking.
[0033] Therefore, the prior art does not lend itself to a reliable
or certain means of investigating formations before, during or
immediately after drilling or fracking.
[0034] Further the prior art generates time-consuming correction
cycles of changes in fracking, azimuth and inclination in an
attempt to retrospectively maintain an optimal frack
trajectory.
[0035] Further, the prior art contributes to an average and
unsatisfactory recovery rate of 35% of hydrocarbons as reserves are
not detected or produced in an optimal manner.
[0036] Further the prior art does not detect variations in
fractures prior to fracking in real-time.
[0037] Further the prior art does not detect variations in fracture
characteristics such as porosity or fluid content in real-time.
[0038] Further the prior art does not detect gas zones, fractures
or water flows ahead of the bit or wellbore in real-time.
[0039] Further the prior art does not detect pressure or
temperature variations ahead of the bit or wellbore in
real-time.
[0040] Further the prior art does not automatically allow for a
closed-link or automatic troubleshooting of well trajectory or
fracking placement.
SUMMARY OF THE INVENTION
[0041] The present invention has for a principal object to provide
an improvement on the prior art wherein the pre and post fractures
are characterized so that fracture pathways and production rates
can be maximised. The invention seeks to provide critical knowledge
of the fracture i.e. reservoir interconnectivty, fractures,
pathways or dips can be gained both pre and post fracking this
would lead to greater recovery rates due to more effective wellbore
fracking by increasing the actual fracked footage in the
payzone.
[0042] The invention seeks to meet the need for a closed-loop
real-time fracture detection to provide real time formation data of
formation data and natural fractures (pre frack) while the wellbore
is being fracked or before the packer is set at a give coordinate
(depth, azimuth, inclination etc). This has not been forthcoming in
the prior art due to missing steps inherent in the pre and post
frack placement, orientation and assembly.
[0043] The present invention seeks to directly investigate pre and
post fracking and offers optimal wellbore and packer placement
using a novel sensor configuration which also allows for optimized
fracture propagation and measurement of post frack
effectiveness.
[0044] The present invention eliminates the uncertainty of trial
and error by providing real-time data which allows the wellbore
isolation device to be set at optimized coordinates, the frack job
to conducted thereafter and the its effectiveness measured thereby
providing real time data as to the effectiveness of the fracking
operation and where necessary to repeat the frack job until the
required recovery will be achieved.
[0045] It is thus an object of the present invention to provide
closed loop fracturing means, enabling the device to give immediate
evaluation of a formation to be fractured, or the characteristics
of a formation once fractured and, if the apparatus detects a
parameter of interest or a change in a parameter of interest such
as a fracture pathway, propagation, production flow, to
automatically calculate and correct for an optimal fracking, and to
repeat evaluation until such an optimal well path result is
achieved in real-time.
[0046] Although fracture detection is a principal route to
characterizing the effectiveness of fracking, the invention is not
limited to fracture detection and envisages alternative
investigation means similarly integrated with fracture detection
capability of the tool. These alternative means can include
nuclear, electro-magnetic, optical, temperature or other such
sensor as deemed required for optimal fracking or wellbore
placement.
[0047] Further the invention can be used to perform hydraulic
fracking with open hole or cased/liner hole applications with or
without perforating assemblies. In such cases, the downhole and
surface configurations would be arranged to meet the needs of the
operation and the apparatus may be connected directly or indirectly
in any manner or order so that the frack operation may be
optimized.
[0048] Fracture sensing means may be located above, below, on the
wellbore isolation means and suitably configured to enable downhole
fracking operations. For example, this may involve the unrestricted
ID (internal diameter) or passage for full flow or pressure or to
drop ball etc to as is know in the art to create the necessary
pressure for fracking. Other configurations may require
additionally or alternatively the ability to retrieve the sensors
or to deploy the sensors above or below the packer. Deployment may
be performed via means such as collapsible supports for the
sensors, fibre optics, miniaturized sensing means, fixed supports,
independently rotatable, extendable supports, arms, blocks, blades,
etc. Power would be provided accordingly and can be contained
within the apparatus or provided from outside the apparatus.
Communications would be provided using wires, wirelessly or a
combination. The invention is not limited in the placement or
configuration of the apparatus.
[0049] It is a further object of the present invention to provide
an apparatus capable of verifying pre and post frack data through a
processor arrangement that uses sensor data to detect fracking
results and conducts diagnostics according to a logic circuit in
order to ensure the wellbore frack plan is optimized in view of
real time fracking data. The processor will automatically detect
whether corrective steps are required to maintain/move the wellbore
fracking in the optimal zone. Data can be collected on each stage
as it is fracked and this is compared with pre frack data and
differing stage data. If the tool finds a significant divergence, a
signal may be sent to the rig-surface or to the location of the
operating engineer so that further remedial action can be taken,
such as coordinate revisions. A memory mode may store sensor
information that can be downloaded at surface when the tool is
retrieved, or sent to the surface by telemetry or by wireless
means.
[0050] One or more sensors may be optimally spaced in the fracking
apparatus in order to investigate the formation, detect fracking
and provide pre and post frack data. The resolution of fracture
detection may be user defined and can be pre-programmed at surface
to the processor or via instruction from a surface location to the
downhole location of the apparatus and processor. The method
according to the invention similarly provides for pre programming
or programming on the fly and communication both using wires or
wirelessly.
[0051] A keyway may provide a channel for wiring from the sensors
to the processor and to a transponder. The wiring can be used to
transmit sensor data retrieved by the sensors, as well as
positional and structural data of formation characteristics such as
fractures and their relative depths, pathways, corridors,
inter-connectivity etc. The keyway may be sealed and filled with a
means to absorb vibration such as silicon gel or grease and to
maintain wires in position. Similarly, the keyways may be left
redundant and as a back-up to a wireless mode of operation.
[0052] The transponder converts formation and fracture data so that
it can be transmitted and may be linked a the mud-pulser which
transmits the data to surface using a series of binary codes at a
given frequency using drilling fluid as means of mud pulsing. Other
means of data transfer may be used such as wireless transmission
short hop using radio frequency or electro-magnetic pulses or wired
drill-pipe. This allows up and downlink of the tool in order to
receive and transmit data and commands so as to optimize
fracking.
[0053] At surface a transducer may be incorporated within a decoder
housing which decodes the binary code and may link to the frac
operations or driller's terminal or may be yet further transmitted
by satellite or other means to a remote operations centre.
[0054] These and other objects will emerge from the following
description and the appended claims.
[0055] In one aspect, the closed loop fracture apparatus (50)
comprises a tool body with means for attaching the tool body (63)
directly or indirectly to a support or reamer, reaming shoe,
drill-bit whereby it can be rotated and moved axially along a
passage (20), and is characterized by, at least one sensor (58)
which can detect natural or man made fractures (FIG. 5) relative to
the horizontal axis of the tool, and (57) is adapted to investigate
and recognize sensor data from a fracked stage (70) or from a
plurality of stages (110,120,130,140) and thereby increase
hydrocarbon recovery rates by optimizing wellbore trajectory and
hydraulic frack location based on formation data acquired by the
sensor before, during or after a frack operation occurs with or
without a drill-bit (70).
[0056] The support may typically be a perforating or production
string (30) or a workstring or drillstring or extended length of
coiled tubing as used in downhole operations in oil and gas
fields.
[0057] In preferred embodiments of the invention, the investigation
operation is based on sensor elements comprising a set of at least
one sensor, receiver combination optimally configured and oriented
to investigate beyond the wellbore and detect fractures. The sensor
housing may comprise protective covering, which may be of similar
construction to the sensors, but having outer surfaces where
sensors are protected by a hardened material. Such protection may
simply bear under temperature, pressure or flow acting against it
from the inside of a wellbore. In an alternate embodiment, the zone
surrounding the housing may be treated to actively receive data or
configured with a variety of receivers rendering it a sensing zone.
The sensors may be provided with a lens surface that may be convex
(52 a), concave (52 b), or planar (52 c) according to requirement.
The sensors and receivers may be optimally tuned and gated in terms
of frequency so that emitted frequencies do not cancel out upon
contact with return waves and so that reference measurements are
taken to establish background noise which would be suitably
excluded from operational measurement calculations. Alternatively,
the same sensors may be received within an additional section of
apparatus or a separate steel body or behind or ahead such section
suitably prepared to provide a means of stabilization or
centralization and protection for downhole applications. Further
sensors may be provided with a means to reduce `ringing` or
`dampening` of the sensors so as to always ensure the measurements
are fit-for-purpose.
[0058] It is to be noted that the description herein of the
structure and operation of sensors or receivers and tool design is
applicable generally, irrespective of function, except to the
extent that certain sensors may be provided specifically for
formation evaluation purposes and replaced by other sensors such as
nuclear or resistivity or acoustic or nuclear magnetic resonance
sensors as required by the drilling operation.
[0059] The apparatus comprises a tool body or a plurality of tool
bodies which are typically cylindrical high grade steel housings
adapted to form part of a fracking assembly. It is not always
necessary that the assembly be used for fracking as the sensors may
be used to determine natural fractures while drilling. Thus the
means for attaching the tool body to the support, whether it is a
drill string or work string or coiled tubing, may comprise a screw
thread provided on the tool body which is engageable with a drill
collar or a connection to a production string for fracking. The
attachment need not be direct, but may be indirect, as there will
typically be many different functional elements to be included in
the long and narrow assembly, and the arrangement of the successive
elements will vary based on production, completion or drilling
applications. The lower end of the assembly may be the drill bit
(or a packer or casing shoe or reamer shoe) which may be directly
connected to the tool and in between there may or may not be other
components dependent on the operational requirement. For example,
in drilling such components could be a means for directional
control such as a rotary steerable system or directional motor. The
tool body may be provided with a through passage for the flow of
drilling fluid from the drill string. For example, in completion
operations using perforating such components could be a means for
wellbore isolation such as a bridge plug or packer. The tool body
may be provided with a through passage for the flow of completion
fluid from the string. In open hole completions perforating may not
be required prior to hydraulic fracturing. Thus the invention is
not limited to a single configuration of the apparatus since it is
always envisaged that the necessary components are available to
perform the frack job.
[0060] Such a through passage allows for full flow, pressure, drop
ball or other actions above or below the tool i.e. activation,
deactivation, or retrieval of equipment. The tool itself may also
be provided to be retrievable so that it may be placed below a
packer or take measurements below a packer or above a packer.
Similarly, any completion or wellbore isolation device such as
intelligent control valve, swellable packer or inflow control
device can be used to isolate the wellbore and create the necessary
pressure to fracture the formation.
[0061] The sensors may be protected and housed in a plurality of
positions directed outwardly of a body. The sensor may be received
within the profile of the tool body in a sensor recess suitably
protected from abrasion, wear and damage by means of at least one
protective coating or covering. The protective coating may be steel
with HVOF, tungsten carbide, boron nickel or other protection
according to requirements. The sensor may be provided with a
dampening material or mechanism such as silicon gel or a
spring.
[0062] The sensor and receiver may then be provided with means for
driving the sensors and receiving the data from the far formation,
near formation or wellbore so as to characterize the fractures
located therein. The microprocessor control means may be suitably
adapted to receive formation data from the sensors and to control
the frequency in response thereto. A gating procedure may be
suitably incorporated to discard a range of background noise
frequencies or by means of establishing a maxima reference
measurement and engaging with such a maxima or by means of
establishing a measurement and engaging with such a measurement.
The microprocessor also may receive information from micro-seismic,
tiltmeters, frack parameters so as to optimize the frack operation
and this may be done in a closed loop operation with or without
user intervention. In this way, a number of differing frac jobs may
be performed at a number of sites and data viewed at a central
location.
[0063] Pressure compensation may be provided to handle variations
in downhole pressure compared to surface atmospheric conditions for
example in fracking where hydraulic flow and pressure may require
pressure compensation (not shown).
[0064] The system may comprise a microprocessor means for
monitoring fracture evaluation data and relative positions of frack
stages where the microprocessor means may include a means of
automatically anticipating any fracture or detecting a feature of a
formation or detecting a change in the feature of a formation,
thereby guiding the control system to ensure the optimal placement
and functioning of the frack operation.
[0065] The tool normally comprises a plurality of sensor and
receivers arranged symmetrically around the tool and disposed
outwardly. The sensor receiver may be configured as an integral
transducer or separated as a sensor to receiver array known as a
`sensing zone` (not shown). Two transducers would be on opposite
sides of the tool, three blocks would be separated by 120 degrees,
four by 90 degrees, and six by 60 degrees. Additionally or
alternatively, sensor receiver arrays could be configured in a
plurality of combinations including longitudinal or wellbore
spacings or axial or spiral, with the object of ensuring the zone
of investigation covers the pre and post fractures.
[0066] In accordance with a particularly preferred aspect of the
invention, the sensor receiver array is provided with an internal
keyway for directing power from a source within the tool and
providing communications to and from the sensor receiver. The
source of power may be a battery within the tool or within another
support for the tool suitably adapted for such purpose. The
communications may be a processor within the tool, or at surface or
other support for the tool suitably adapted for such purpose.
Alternatively or additionally, the sensor/receiver or tool body may
be provided with a wireless means of communication to an internal
or external processor. In each case, the two-way communications
provide data transmission, operational refinement and data
capture.
[0067] In order to keep the sensor/receiver clean and prevent the
build-up of clogging debris from the fracking operation, the sensor
housing may be provided with a specialized coating to minimize the
residence or remove such material altogether from the sensing
zone.
[0068] In one preferred aspect the present invention incorporates a
wellbore isolation device so as to permit a frack job and sensors
to permit the detection of fractures before and after a frack
job.
[0069] In another aspect of the present invention housing for other
types of sensors is provided. The tool may further comprise
telemetry means for communicating downhole data and control signals
between the tool and a surface interface, which may, among other
functions, control the drill string or work string during the
drilling or frack operation.
[0070] In a further aspect, the invention provides a method of
operating an apparatus to investigate natural and induced fractures
and to optimally guide and place a wellbore which comprises
locating a wellbore fracking device according to the invention in a
borehole on a support, activating the sensors/receivers to detect
natural fractures and establish a set of coordinates for locating a
wellbore fracking device, fracking a wellbore, and detecting the
effectiveness of the fracking operation and if unsatisfactory
repeating the fracking operation at the same coordinates or further
coordinates until an optimal fracking operation is completed and
hydrocarbon production is maximized.
[0071] The data gathered by the sensors relates to the natural and
induced fractures and can be all relevant characteristics
concerning the fracture matrix, such as their depth, relative
distance, azimuthul orientation, pathways, interconnectivity and
corridors. natural fractures and their interplay with hydraulic
fractures. Many considerations affect this fracture matrix such as
organic content, porosity, permeability, brittleness, orientation,
pressure but as a general rule, because hydraulic fractures
propagate along the path of natural fractures, detecting natural
fractures is clearly most useful in enlarging and stabilizing the
natural fracture matrix. Although, fractures may appear closed in
cores, markers i.e. differing properties from the surrounding rock
such as impedance, calcite lining, etc provide clues to their
detection.
[0072] In accordance with the method of the invention, the tool may
be provided with microprocessor means responsive to formation data
received from the sensor/receivers. In this way, a closed loop tool
which is capable of detecting fracture changes and controlling
wellbore fracking may be realised. The sensor/receiver may
investigate the fracture, or investigate a feature of a fracture,
set a wellbore fracking device, frack a formation and may further
investigate the fracture to provide data to a surface monitor to
signal an opportunity for operator intervention to correct wellbore
fracking if it were not able to do so automatically.
[0073] Thus, in the case of the pre and post frack detection system
data from the formation are detected by sensors. These fracture
data may be transmitted from the sensor to a processor which
correlates the fracture data and uses this to establish the optimal
location for setting a wellbore fracking device taking into
consideration formation characteristics such as dips, faults, and
allowing for variations in the formation. The processor uses this
data to correlate whether the pre-programmed frack program will be
achieved and the resulting hydraulic pressure and frack fluids that
would be required to frack to an optimal level. Where the processor
detects that a fracture or feature of a formation may affect the
frack parameters such as hydraulic pressure, fluid types, proppants
etc it can automatically recalculate an optimal value for the
hydraulics as well as the physical location for the frack to occur.
Or it may simply signal an opportunity for an operator to
intervene.
[0074] In the case of fracking, the operator may frack using a
drilling or completion or production assembly or a frack assembly.
In both cases the present invention can be employed to detect pre
and post fractures and thereby a novel way of maximizing the
placement and effectiveness of any fracking operation. The
principal objective is knowledge of the fracture i.e. reservoir
interconnectivty, fractures, pathways or dips gained both in pre
and post fracking which leads to greater recovery rates due to more
effective wellbore fracking by increasing the actual fracked
footage in the payzone.
[0075] For example, the processor may be programmed with a logic
circuit which can be configured in any number of ways so as to
optimize performance. An exemplary configuration may involve the
circuit to first cross check the natural fracture data and then set
a wellbore fracking device. The fracking operation is performed and
the induced fracture data and if required corresponding flow of
hydrocarbons is obtained by the sensors and transmitted to the
processor. In this way, the processor can measure the effectiveness
of the induced fracking directly and if it were insufficient
provide for a further cycle of fracking. This distinguishes the
present invention from the prior art which has neither the ability
to compare natural and induced fractures nor optimize the location
of fracking devices.
[0076] If it is seen that the induced fracture is insufficient in
terms of production of hydrocarbons, the fracking operation can be
repeated at the same coordinates with a change in fracking
parameters. If the post frack data still shows insufficient gain in
production of hydrocarbons, the apparatus can provide for example,
a change in the depth, orientation or angle at which the fracking
device is either isolated from the wellbore or the coordinates at
which it fractures the formation. The apparatus may further be
optimized for shale oil, shale gas or tight gas zone or coal bed
methane so that apparatus can alert the user by means of telemetry
to check the wellbore frack device location, azimuthal,
inclination, or frack parameters as necessary or prompt this
through a closed loop system. The skilled person will readily
appreciate that other procedures may be implemented by the logic
circuit within the processor, which can be programmed to cover
other scenarios.
[0077] In another aspect, the invention provides a fracture
detection method comprising locating a tool body with sensors and
receivers, optionally but not limited to a housing carrying a
plurality of sensors and receivers directed outwardly of the tool
body, wherein the sensor or receiver is received within the tool
body in a purpose built housing having an open mouth, and means for
allowing sensor emissions to propagate to and from the housing and
to and from the wellbore, near and far formation to detect natural
and man-made fractures.
[0078] In a still further aspect, the invention provides a wellbore
fracking device used in conjunction with the fracture detection
capability outlined above comprising a wellbore isolation device
such as a expandable packer, intelligent flow control device,
intelligent control valve, confirmable sponge, swellable packer
carrying at least one expandable element to conform to the wellbore
and isolate a specific area in the wellbore. Additionally or
alternatively further areas in the wellbore may be left open to
allow free flow of hydrocarbons. In this way a plurality of
wellbore flow areas may be created allowing for fluids to frack the
wellbore as well as allowing the flow of hydrocarbons into the
wellbore.
[0079] Additionally, sensor and receiver arrays may be configured
optimally by providing longitudinal spacings between the sensors
and receivers.
[0080] Additionally, the apparatus may be provided with
compensation and/or calibration means for enhancing fracture
detection. Typically, compensation and/or calibration occurs using
look up tables for parameters affecting sensor measurements or
measurements made at surface or downhole. The invention envisages
all types of such calibration since they can improve the accuracy
of measurements and fracture detection.
[0081] Other aspects of the invention are disclosed in the
following specific description of exemplary embodiments of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0082] Embodiments of the invention are illustrated by way of
non-limiting examples in the accompanying drawings, in which:
[0083] FIG. 1 is a general diagrammatic view of an oil or gas well
showing rig surface structures (10) and the underground well (20),
with a tool (50) in accordance with the invention as part of a
bottomhole assembly (40) drilling a well (30) and indicating
formations and formation features (70) located ahead of the
drill-bit (60) and a wellbore (80);
[0084] FIGS. 2,2a,2b, are downhole side views illustrating a a
plurality of sensor distributed along the apparatus in a helical,
longitudinal, spiral arrangement respectively. It is not essential
the sensors are distributed on a tubular body as the may be located
within collapsible arms, extendable arms, fibre optic cables,
distributed within casing or liners or retrievable from below a
packer. Sensors may be non rotating, rotatable, independently
rotatable, toward the wellbore or internally or may be fixed in
position. The invention is not limited in sensor placement or
fixing.
[0085] FIG. 3a show a and 3b show a radial corresponding to radial
sensor distribution corresponding to FIG. 2
[0086] FIG. 4 is a 3-D Earth cube from a surface (260) and downhole
side (150) view, part cut away to show the fracking operation (160)
according to a multi stage fracking operation (280);
[0087] FIG. 5 is a diagrammatic cross section through the apparatus
in accordance with the invention similar having a wellbore
isolation device (62) or other zonal isolation member (63) at the
downhole end;
[0088] FIG. 6 is a diagrammatic cross section through the apparatus
in accordance with the invention similar to that shown in FIG. 5,
but having an additional wellbore isolation device (61) or other
zonal isolation member at the trailing uphole end
[0089] FIG. 7 is an exemplary embodiment with sensing element
between zonal isolation devices as would be the case with multiple
stages or packers according to frack operations.
[0090] FIG. 8 is an exemplary diagnosis and troubleshooting
procedure according to the invention showing fracture detection and
integration with other data such as micro-seismic, tiltmeters,
fracking parameters and the like.
DETAILED DESCRIPTION OF THE INVENTION
[0091] As shown in FIG. 1, an exemplary exploration or production
rig comprises a surface structure (10) at the wellhead, a wellbore
(20), and a string (30) in the wellbore with a downhole assembly
(40) at its lower end. The downhole assembly includes an apparatus
(50) in accordance with one aspect of the invention, a sensing
means and a wellbore isolation device (60) and formations fractured
and detected as the object of the invention.
[0092] The apparatus (50) is illustrated by way of exemplary
embodiments in FIGS. 5, 6, and 7 comprises a tubular steel body
(62) provided with a connection at either end to enable its direct
or indirect connection to the wellbore isolation device (60) and
connect it to other elements of the downhole assembly (40) and a
link to a means of communication to the surface (64). Wellbore
isolation device (60) may be replaceable by a drill bit where the
invention is used in while drilling capacity to detect natural
fractures.
[0093] The apparatus comprises a tool body (58) that carries at
least one housing for at least one sensor (58) and a wellbore
isolation device (60) capable of detecting natural and induced
fractures. The sensor element (51) comprises a number of sensing
elements (52) disposed radially around the profile of the tool body
FIG. 3a. The sensors detect fractures that extend beyond the
wellbore (60) and into formations surrounding (70) and at multiple
stages or locations in the wellbore (110, 120, and 130).
[0094] An exemplary configuration of the invention in accordance
with its specified object is shown in FIG. 5.
[0095] FIG. 5 is a diagrammatic cross section through a lookahead
tool in accordance with the invention similar to that shown in FIG.
5, but having a wellbore isolation device (62) or other wall
contact member (69) at the trailing uphole end. Equally, such
downhole wall contact may be an expandable device, pressure
containment device;
[0096] FIG. 7 illustrates diagrammatically the aforementioned
sensing elements within the tool (50), together with a wellbore
isolation device (61) in a cross section view in accordance with
the invention similar to that shown in FIG. 5, but having an
additional wellbore isolation device (61) at the leading downhole
end; wherein a plurality of such devices may be employed as is the
case where multiple frack stages are required to stimulate the
reservoir.
[0097] Fracking performance is verified using a micro-processor,
shown in location (55), that compares data from the sensor (51)
with a pre-programmed wellbore frack plan, thus detecting natural
and induced fracking. Additionally or alternatively, the micro
processor may be located at the surface especially when a micro
seismic or tiltmeter or surface frack parameters are measured. The
apparatus is programmed and automated to conduct diagnostics
according to a logic circuit or diagnostic program stored in
processor (55) in order to ensure the fracking is optimally
performed. Once corrective steps have been taken, and if the
apparatus indicates that the planned fracking (trajectory,
productivity, location etc) is not optimal in light of formation
data, an alert signal is sent via the mud-pulser (64) to the
rig-surface 10 or to a remote operator so that control action of
the assembly (40) can be taken. A memory module (not shown)
associated with processor (55) may store sensor information that
can be downloaded at surface when the tool is retrieved, or sent to
the surface by telemetry through a transponder to a mud-pulser (64)
or by other communication means. A means of powering the sensors
and receivers is shown by (54).
[0098] The tool is provided with a built-in link to a communication
system which may be a wired or wireless telemetry system (64) which
also serves to monitor real-time formation data and features. One
or more sensor receivers (51) are spaced within the tool body in
order to detect fractures in a single part of the wellbore (40) or
a multiple number (110,120,130). The microprocessor (55)
establishes formations (110, 120, 130) and formation features (160)
and fracture data through a series of calculations derived from
acoustic velocity or resistivity or neutron density imaging. The
invention is not limited to sensing or imaging means and compares
this with preprogrammed targets. If the two measurements match
given user defined tolerances the tool continues to total depth of
the wellbore section. Where the formation data do not match the
logic circuit dictates a series of diagnostic steps, which are
further discussed in relation to FIG. 8 below.
[0099] As further shown in FIG. 5, a keyway provides a channel for
wiring (56) from the sensor (51) to the processor (55), and also to
a comms device (64). The wiring is used to transmit formation
evaluation data retrieved by the acoustic reflection sensors (51)
as well formation features (110, 120, 130, 160) from the receivers
(52) to the processor (55) and transponder (64). The keyway may be
sealed and filled with a means to absorb vibration and maintain
wires in position such as silicon gel or grease (not shown).
[0100] The comms device (64) converts data from the microprocessor
(55) so that it can be transmitted to surface (10) and may also
receive data from the surface. Means of data transfer may be used
such as wired, wireless, short hop using radio frequency or
electro-magnetic pulses, mud-pulse etc.
[0101] FIG. 6 shows an alternative configuration with a wellbore
isolation device (61) and shows a central axial through passage
(59) for the free flow of fracturing fluid or drop ball through a
central axial passage.
[0102] Additionally or alternatively, housing (51) may also be
suitably adapted and treated for use of other types of sensor,
analogue or digital, resistivity, electro-magnetic, nuclear
magnetic resonance, acoustic, pressure, flow to detect a
fracture.
[0103] The tool body (50) is a cylindrical high grade tube adapted
to form part of a downhole fracking assembly 40. Suitable materials
for the tool body are metallic, ceramic, or any other high strength
material. FIGS. 5, 6 show a diagrammatic side view of the apparatus
(50). At the leading downhole end there is pin connection (63) to a
drill-bit, in the centre is a profiled section (58) housing sensing
(51, 52) and control functions (55).
[0104] FIG. 6 shows a further section at the uphole end, (69), is
connected to a fracking assembly (40). At either end a wellbore
isolation device may be placed to create zonal isolation for
fracking. Sensors can detect fractures pre and post fracking either
downhole or at surface as per FIG. 2 above. Sensors may be
constructed and housed integrally and generally designated as (51),
except that a plurality of sensors may be placed to form a sensing
zone as per FIGS. 2a,2b,2c, 3a and 3b. In all embodiments there is
at least one surface which is hard faced or coated with a hard
abrasion-resistant material. Any suitable means for attaching the
tool body to a fracking assembly is envisaged.
[0105] In this alternative configuration the tool is configured, in
addition to sensing capacity, with the wellbore isolation device
incorporating expandable device to isolate the wellbore and allow
pressure to frack the formation. The wellbore isolation device may
be directly or indirectly above or below the central sensing
section and may be hard-wired or wireless accordingly so as to
ensure the comms device (64) may transmit data to surface (10). The
comms may be provided as wireless or wired the configuration of the
apparatus may be changed to suit such an application.
[0106] As shown in FIGS. 5, 6, and 7, the illustrated example of a
pre and post frack apparatus in accordance with the invention is a
sensor which uses a microprocessor (55) and wellbore isolation
device to determine and perform an optimal wellbore frack
operation. Sensor/receiver means (51, 52) determine single or
multiple frack characteristics (110, 120, 130, 160) and send
corresponding signals back to the processor (55).
[0107] As required, the sensors (51) may be protected and housed
(53) in a plurality of positions and/or orientations directed
outwardly of a tool body (58) and at all times to detect fractures
(60) and configured optimally based on formation and downhole
component considerations. The sensors may be received within the
tool body in a sensor housing recess (53) that is also suitably
protected from abrasion, wear and damage by means of at least one
protective coating or covering. The protective coating may be steel
with a HVOF coating, tungsten carbide, boron nickel, titanium,
epoxy, kevlar or other protection suited to requirements. The
sensor may also be provided with a dampening material or mechanism
such as silicon gel or a spring (not shown).
[0108] The sensor means may then be provided with drive means (54)
for driving the sensors and receiving data from the multiple stages
(110,120,130,160), fracture or wellbore (80). The microprocessor
control means (55) may be suitably adapted to receive formation
data from the sensors (51, 52) and to control the frequency in
response thereto. A gating procedure may be suitably incorporated
to discard a range of background noise frequencies or by means of
establishing a maxima reference measurement and engaging with such
a maxima. Noise in this context does not refer to solely to
acoustic noise, but any electrical, sensor or other signal or
circuitry interference.
[0109] Pressure compensation may be provided to handle variations
in downhole pressure compared to surface atmospheric conditions
where activation is opposed by a source of external pressure. This
may comprise a port from a source of downhole fluid into a chamber
suitably connected to the area within the area requiring pressure
compensation (not shown).
[0110] The system may comprise a microprocessor means for
monitoring formation evaluation data and relative positions of
formation structures where the microprocessor means may include a
means of automatically anticipating a fracture or detecting a
fracture or detecting a change in a fracture or detecting a
fracking effectiveness, thereby guiding the fracking operation to
ensure the optimal wellbore production.
[0111] The apparatus normally comprises a plurality of sensing
means arranged around the toolbody and disposed outwardly. The
sensing means may itself may be configured as an integral
transducer or separated as a plurality of sensors to receivers
(array) known as a `sensing zone`. Sensors or transducers may be on
opposite sides of the tool radially, longitudinally, axially or
helically. Sensor receiver arrays could be configured in a
plurality of combinations with the object of ensuring the zone of
fracture detection and the zone of wellbore isolation is optimized
within the sensing zone.
[0112] In accordance with a particularly preferred aspect of the
invention, the transducer or sensor receiver array is provided with
an internal keyway for directing power from a source within the
tool and providing communications to and from the sensor receiver.
The source of power may be a battery within the tool or within
other support for the tool suitably adapted for such purpose. The
communications may be a processor within the tool, or at surface or
other support for the tool suitably adapted for such purpose.
Alternatively or additionally, the sensor/receiver or tool body may
be provided with a wireless means of communication to an internal
or external processor. In each case, the two-way communications
provide data transmission, operational refinement and data
capture.
[0113] In order to keep the sensors and/or receivers clean and
prevent the build-up of clogging debris from the downhole
operation, the sensor housing may be provided with a specialized
coating to minimize the residence or remove such material
altogether from the sensing zone.
[0114] In one preferred aspect the present invention incorporates
an optimal means of fracture detection which is practically
applicable to natural and induced fractures and is combined with
wellbore placement means such as rotary steerables.
[0115] In another aspect of the present invention the fracture
detection means are provided with a plurality of wellbore isolation
devices.
[0116] The apparatus may further comprise telemetry means for
communicating downhole data and control signals between the tool
and a surface interface, which may, among other functions, control
the apparatus during the formation evaluation operation.
[0117] In a further aspect, the invention provides a method of
operating a logging tool to investigate a formation or a fracture
or the like to optimally guide and place a wellbore isolation
device which comprises locating a device according to the invention
in a borehole on a support, activating the sensors/receivers to
detect fractures from the formation and establish data on fractures
and features thereof, their relative distance, size from the tool
in a preferred embodiment of apparatus, fracturing a formation,
investigating the formation recently fractured by the sensors, and
continuing the operation until an optimal wellbore production is
achieved.
[0118] To those skilled in the art, it is known that the wellhead
surface structure (10) includes a control and communications system
having an interface for communication telemetry with downhole
instrumentation including a transponder and a decoder which decodes
data and may be linked directly to the user's terminal. The decoded
data may be yet further transmitted by satellite or other means to
a remote user or a remote operations centre by means of a
telecommunication link. This surface control system allows full
communication to and from the downlink and uplink to the
invention.
[0119] The invention may also provide a method of automatically
operating a directional tool according to a processor to optimally
place a wellbore, tubular or completion.
[0120] FIG. 8 is an exemplary diagnosis and troubleshooting
procedure according to the invention showing fracture detection and
integration with other data such as micro-seismic, tiltmeters,
fracking parameters and the like.
[0121] It is recognized that the apparatus could be programmed by
the skilled person to cover many other scenarios.
[0122] Those skilled in the art will appreciate that the examples
of the invention given by the specific illustrated and described
embodiments show a novel fracture detection apparatus and method
for formation evaluation, with numerous variations being possible.
These embodiments are not intended to be limiting with respect to
the scope of the invention. Substitutions, alterations and
modifications not limited to the variations suggested herein may be
made to the disclosed embodiments while remaining within the ambit
of the invention.
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