Patent Application
20200378231
This application is directed, in general, to a downhole fracturing tool assembly, and more specifically, to an improved downhole fracturing tool assembly that creates localized pulse of pressure.
Many subterranean formations containing hydrocarbon reservoirs suffer from the problem of having insufficient permeability or productivity to enable the hydrocarbons to be recovered at the surface in an effective and economical manner. To increase the permeability or productivity of these formations, the formations are fracked/fractured and stimulated. While fracking is a well-known art, improvements are nevertheless needed in the tools and/or methods for fracturing subterranean formations.
Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The present disclosure is based, at least in part, on the acknowledgment that in fracture stimulation, the initial pressure to open a fracture is much higher than is necessary to complete the stimulation process. Turning briefly to
With the forgoing acknowledgment in mind, the present disclosure has further acknowledged that the pressure spike is generally necessary because of the near-wellbore stresses, e.g., because the initial fracture is at an angular direction from the local fracture direction. The larger the obliqueness of the position (e.g., near 90 degrees), the higher the spike. Once the fracture opens, the pressure requirement drops rapidly, as the fractures will take fluid and bend towards the max stress direction.
Given the foregoing acknowledgments, the present disclosure has recognized that a downhole rapid pressure modification system, for example that is significant enough to temporarily increase the initial downhole pressure to account for the near-wellbore stresses, may be used to initiate the fracture, without affecting the surface pressure requirements. In accordance with this recognition, introduced herein are a downhole fracturing tool assembly and a method of using the assembly that can create a sufficient local pressure (e.g., downhole near the zone of interest) to initiate a fracture therein. The introduced downhole fracturing tool assembly and method can, thus, locally create a pulse of pressure that is sufficient to initiate a fracture in the subterranean zone of interest using a localized fracking system. The localized fracking system can create a large initial pulse of pressure using an explosive, such as a current or spark initiated digital explosive, and/or an actuator, such as a piston or ball-release actuator, among other conceivable methods.
The introduced downhole fracturing tool assembly and method provides the following advantages over the conventional fracturing method. First, the introduced downhole fracturing tool assembly and method improves overall equipment life by reducing the pressures that are necessary for the fracturing process, and thus being subjected to the equipment. Second, the introduced downhole fracturing tool and method reduces the power requirement in the field by eliminating the need to drive the high pressure fluid from the surface. As such, the introduced downhole fracturing tool and method would be able to reduce the operation and maintenance cost, as well as any non-productive time for customers.
In the drawings and descriptions that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals, respectively. The drawn figures are not necessarily to scale. Certain features of the disclosure may be shown exaggerated in scale or in somewhat schematic form and some details of certain elements may not be shown in the interest of clarity and conciseness. The present disclosure may be implemented in embodiments of different forms.
Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed herein may be employed separately or in any suitable combination to produce desired results.
Unless otherwise specified, use of the terms “connect,” “engage,” “couple,” “attach,” or any other like term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described.
Unless otherwise specified, use of the terms “up,” “upper,” “upward,” “uphole,” “upstream,” or other like terms shall be construed as generally toward the surface of the ground; likewise, use of the terms “down,” “lower,” “downward,” “downhole,” or other like terms shall be construed as generally toward the bottom, terminal end of a well, regardless of the wellbore orientation. Use of any one or more of the foregoing terms shall not be construed as denoting positions along a perfectly vertical axis. In some instances, a part near the end of the well can be horizontal or even slightly directed upwards. In such instances, the terms “up,” “upper,” “upward,” “uphole,” “upstream,” or other like terms shall be used to represent the toward the surface end of a well. Unless otherwise specified, use of the term “subterranean formation” shall be construed as encompassing both areas below exposed earth and areas below earth covered by water such as ocean or fresh water.
Referring initially to
A subsea conduit 245 extends from the platform 215 to a wellhead installation 250, which may include one or more subsea blow-out preventers 255. A wellbore 260 extends through the various earth strata including formation 210. In the embodiment of
When it is desired to fracture a particular subterranean zone of interest, such as zone 275, the downhole fracturing tool assembly 290 may be deployed within the wellbore 260 using a downhole conveyance 280. In the illustrated embodiment of
With the downhole fracturing tool assembly 290 in place, pressure within the wellbore 260 may be increased using the fracturing pump 235 and one or more different types of fracturing fluid and/or proppants. Once a threshold pressure is achieved, the downhole fracturing tool assembly 290 may be operated to introduce a localized initial pulse of pressure sufficient to initiate a fracture of the subterranean zone of interest 275. In one example embodiment, the downhole fracturing tool assembly 290 generates the localized initial pulse of pressure to initiate the fracture, and the pressure created by the fracturing pump 235 extends the fracture. In another alternative embodiment, the downhole fracturing tool assembly 290 generates the localized initial pulse of pressure to initiate the fracture, and then generates one or more subsequent pulses of pressure sufficient to extend (e.g., along with the threshold pressure generated with the fracturing pump 235) the fracture of the subterranean zone of interest 275.
In certain embodiments, discussed more fully below, the downhole fracturing tool assembly 290 includes an isolation assembly (e.g., including one or more slips and/or one or more packers) that radially deploy therefrom. In this embodiment, the downhole fracturing tool assembly 290 may be used to isolate a portion of the wellbore 260 below the subterranean zone of interest 275, for example prior to generating the localized initial pulse of pressure. In certain other embodiments, again discussed more fully below, the downhole fracturing tool assembly 290 additionally includes a perforator coupled thereto. The perforator, which in one embodiment may be a perforating gun assembly or hydrajet perforating assembly, among others, may be used to perforate the casing 265 after the isolation assembly has been set and prior to generating the localized initial pulse of pressure. In this embodiment, the subterranean zone of interest 275 is isolated, perforated, and fractured using a single (e.g., wireline deployed) downhole assembly, and moreover may be done so without the aforementioned significant surface pressure spikes.
Turning to
The downhole fracturing tool assembly 300, in the illustrated embodiment of
The connector 310, in the illustrated embodiment, is designed to connect/disconnect any one of the perforator 320 and/or the downhole fracturing tool 330 from the conveyance device 305 when any of said components needs to be repaired, replaced or abandoned. The connector 310 may use any currently known or hereafter discovered connecting/disconnecting mechanism and remain within the purview of the disclosure. Accordingly, the present disclosure should not be limited to any specific connector 310.
The perforator 320, in the illustrated embodiment, is a perforating tool designed to perforate a portion of the casing 390, as well as any cement that may be located between the casing 390 and the wellbore 395. As those skilled in the art appreciate, the perforations allow the fracturing fluid to reach the subterranean zone of interest during subsequent fracturing processes, as well as allow production fluids to enter the casing 390 during well production. The perforator 320, in one embodiment, may be positioned proximate the downhole fracturing tool 330, e.g., between the connector 310 and the downhole fracturing tool 330.
In one example embodiment, the perforator 320 is a perforating gun assembly configured to discharge one or more charges (e.g., shaped charges in one embodiment) to form the perforations in the casing 390. In embodiments wherein a perforating gun assembly is used, signals (e.g., electrical signals) may travel down the conveyance device 305 for operation thereof. In another example embodiment, the perforator 320 is a hydrajet perforating assembly configured to employ high pressure jets of fluid (e.g., as opposed to charges) to form the perforations in the casing 390. One such hydrajet perforating assembly may be purchased from Halliburton Energy Services (Houston, Tex.) under the tradename Hydra-Jet™. In embodiments where a hydrajet perforating assembly is used, the perforator 320 might be coupled to surface equipment using a tubular (e.g., coiled tubing in one example).
It is understood that the connector 310 and perforator 320 may be omitted from the downhole fracturing tool assembly 300 depending on the application in which the downhole fracturing tool assembly 300 is used. For example, to frack an open-hole portion of the wellbore 395, the perforator 320 may be omitted, and thus there may be no need for the connector 310.
The downhole fracturing tool 330, in accordance with the disclosure, is configured to create a localized initial pulse of pressure sufficient to initiate a fracture of the subterranean zone of interest. The term “localized pulse,” unless specifically stated otherwise, hereinafter refers to a pulse that is localized or contained proximate to a zone to which a fracturing operation is directed, but does not extend uphole to negatively affect the surface equipment. For example, while the zone of interest might see a large spike such as that shown in
The downhole fracturing tool 330, in the illustrated embodiment, includes a tool body 340. The tool body 340 may comprise a variety of different configurations and/or materials and remain with the scope of the disclosure. In the embodiment shown, the tool body 340 is a metal tubular. Located within the tool body 340, in the embodiment of
In the illustrated embodiment, the localized fracking system 350 includes an explosive device 355. The explosive device 355, in the illustrated embodiment, is the feature of the localized fracking system 350 that is designed to provide the localized initial pulse of pressure. A variety of different explosive devices and/or materials are within the scope of the present disclosure. In one embodiment, the explosive device 355 includes a single charge configured to provide a single initial pulse of pressure. Those skilled in the art, given the aforementioned disclosure, would be able to design and manufacture such a single shot explosive device 355.
In other embodiments, the explosive device 355 is designed to provide multiple different explosions, which allows the localized fracking system 350 to provide multiple pulses of pressure (e.g., whether initial pulses or subsequent pulses) to the subterranean zone of interest. And in even different embodiments, the explosive device 355 is designed to provide varying amounts of localized pressure, for example depending on how the explosive device 355 is detonated. One such explosive device 355 that provides multiple detonations and varying degrees of pulses in pressure is a current initiated solid state propulsion device. When using such a current detonated device, the number of explosions and/or size of the explosions, and thus the number and size of the pressure pulse(s), may be modulated by varying the duration of the current or amount of the current, respectively. By creating modulated current, the current initiated solid state propulsion device can create a desired series of pressure pulses, which can help initiating the fracture. Another such explosive device 355 that provides multiple detonations and varying degrees of pulses in pressure is a spark initiated solid state propulsion device. When using such a spark detonated device, the number of explosions and/or size of the explosions, and thus the number and size of the pressure pulse(s), may be modulated by varying the duration of the spark or size of the spark, respectively. By creating modulated sparks, the spark detonated device can create a desired series of pressure pulses that can help initiating the fracture. Current initiated solid state propulsion devices and spark initiated solid state propulsion devices, as might be used herein, may be purchased from Digital Solid State Propulsion, Inc., having a principal place of business of 5474 Louie Lane, Reno, Nev. 89511. Those skilled in the art understand the various different mechanisms that may be used to control the explosive device 355, including an electrical signal provided through the conveyance device 305 from uphole (e.g., from the control system 240 of
The localized fracking system 350, for example by way of the current initiated solid state propulsion devices and spark initiated solid state propulsion devices, among others, may be configured to create one or more localized subsequent pulses of pressure sufficient to extend the fracture of the subterranean zone of interest in certain embodiments. The subsequent pulses of pressure, in one or more embodiments, may be less than the initial pulse of pressure, but yet sufficient to stimulate the fracture in the zone.
In the illustrated embodiment, the localized fracking system 350 is designed to create the localized subsequent pulse of pressure at varying frequencies that correspond with the natural frequencies of the fracture. By varying the timing of the detonation, the localized subsequent pulse of pressure can be varied to correspond with the natural frequencies of the fracture as the fracture extends into the zone of interest. For example, the downhole fracturing tool 330 could employ a sensor 370 to measure the pressure of the zone of interest throughout the fracturing operation. Based on the changes in the pressure, the pressure sensor 370 can detect the natural frequencies of the fracture as the fracture extends into the zone of interest. Thus, the natural frequencies of the fracture may be relayed to a control system, e.g., a local control system within the downhole fracturing tool 330 or the surface control system 240 in
The downhole fracturing tool 330, in the illustrated embodiment, additionally includes an isolation assembly 375 radially deployable from the tool body 340. The isolation assembly 375, in the illustrated embodiment, is an electrically actuated isolation assembly 375 that includes one or more slips 380 and/or packers 385. For example, the conveyance device 305 could be used to send a signal to the electrically actuated isolation assembly 375 to radially deploy. While the isolation assembly 375 is illustrated in
Turning to
Turning to
In the illustrated embodiment, the localized fracking system 550 employs a ball-release fluid hammer actuator device designed to create the localized initial pulse of pressure. The localized tracking system 550, in the illustrated embodiment, includes a ball release 555 that holds a ball 560 at an initial position. The ball release 555 is designed to release the ball 560 from the initial position to create the localized pulse of pressure. The ball release 555 may be controlled electrically by the control system, such as the surface control system 240 in
Turning to
At step 620, a downhole fracturing tool assembly is deployed within a dvellb a subterranean zone of interest. The zone of interest refers to a targeted region in the oil/gas formation that is to be perforated and fractured for production. In step 620, the downhole fracturing tool assembly may be deployed within the wellbore using a conveya ice device, such as a wireline.
At step 630, the zone of interest is perforated using a perforator. The perforator may be a perforating gun that is design to shoot a charge into the inner wall of a casing, through the cement outside the outer wall of the casing, and out into the zone of interest. In another embodiment, the perforator may also be a hydrajet perforating assembly, or a different perforator.
At step 640, the zone of interest is isolated from a portion of the wellbore that sits below the zone of interest using an isolation assembly. The isolation assembly, in one embodiment, is radially deployed from a tool body of the downhole fracturing tool assembly and seals the portion of the wellbore sitting below the isolation assembly. It is understood that if the zone of interest is the bottom end of the wellbore, the isolation assembly need not be deployed, and step 640 may be omitted. It should be further understood that step 640 may occur before step 630 in certain embodiments.
At step 650, a localized initial pulse of pressure is created using the downhole fracturing tool assembly. More specifically, the localized initial pulse of pressure is created using a localized fracking system, which forms, with a tool body, a portion of a downhole fracturing tool. The localized initial pulse of pressure is sufficient to initiate a fracture of the zone of interest. The localized initial pulse of pressure can be created using an explosive device, a linear oscillatory actuator device, a ball-release fluid hammer actuator device, or another device manufactured and designed according to the disclosure.
At step 660, natural frequencies of the fracture that extend into the zone of interest are detected using a sensor (e.g., pressure sensor). The sensor may be located on/in the tool body, and can detect the natural frequencies of the fracture based on the changes in the pressure measurements as the fracture develops after the initial fracture. While the sensor has been described as being located on/in the tool body, those skilled in the art understand that other locations for the sensor are within the scope of the disclosure, so long as the sensor is capable of taking the necessary pressure measurements to detect the natural frequency of the fracture.
At step 670, a localized subsequence pulse of pressure is created using the downhole fracturing tool assembly. More specifically, the localized subsequent pulse of pressure is created using the localized fracking system of a downhole fracturing tool. The localized subsequent pulse of pressure is sufficient to stimulate the fracture, and may be created at varying frequencies that correspond with the natural frequencies of the fracture. Similar to step 650, the localized subsequent pulse of pressure can be created by using an explosive device, a linear oscillatory actuator device, a ball-release fluid hammer actuator device, or another device manufactured and designed according to the disclosure. The magnitude of the pressure created can be controlled by controlling the amount of the explosive being detonated, and the frequency of the pressure can be controlled by timing the activations of the localized fracking system.
The method 600 ends in a stop step 680.
Aspects disclosed herein include:
Those skilled in the art to which this application relates will appreciate that other and further additions, deletions, substitutions and modifications may be made to the described embodiments.
