GB2525229A

GB2525229A - A downhole device for reliable data recovery after data acquisition during downhole operation and method thereof

Info

Publication number: GB2525229A
Application number: GB1406892.8A
Authority: GB
Inventors: Fraser Louden; Neil Matheson
Original assignee: OMEGA WELL MONITORING Ltd
Current assignee: OMEGA WELL MONITORING Ltd
Priority date: 2014-04-16
Filing date: 2014-04-16
Publication date: 2015-10-21
Also published as: GB201406892D0; WO2015159058A2; WO2015159058A3

Abstract

A downhole device 104 for data acquisition during fracing operations, includes at least one data acquisition device, adapted to detect and record at least one physical property; a wireless data transceiver, operably coupled to said at least one data acquisition device; a controller, operably coupled to said wireless data transceiver and adapted to execute a wireless data transmission in response to an actuation signal, and a data acquisition device carrier adapted to accommodate said at least one data acquisition device, said wireless data transceiver and said controller.

Description

A DOWNHOLE DEVICE FOR RELIABLE DATA RECOVERY AFTER DATA

ACQUISITION DURING DOWNHOLE OPERATION AND METHOD

THEREOF

The present invention relates to devices and processes used in well drilling. More specifically, the invention relates to a downhole device for data acquisition and wireless data recovery during a hydraulic fracturing operation and a method thereof

INTRODUCTION

In drilling operations for the production of oil and gas deposits, operators strive to maximize both the rate of flow and the overall quantity of hydrocarbon that can be recovered from the subsurface formation or reservoir to the surface. Therefore, various stimulation techniques have been developed and one of the most commercially successful techniques today is hydraulic fracturing, also referred to as fracking" or "fracing".

The hydraulic fracturing process involves targeting a portion of the strata surrounding the wellbore and injecting a specialized fluid into the wellbore at pressures sufficient to initiate and extend a fracture into the formation. The fluid which is injected through the wellbore typically exits through holes which are formed in the cemented well casing using a special tool known as a perforating gun.

As a result, a fracture zone, i.e. a zone having multiple fractures, or cracks in the formation, is created through which hydrocarbon fluids such as crude oil or, more commonly, gas can flow into the wellbore and be produced at the surface. These fractures are extended by continued pumping and are either propped open with sand or other propping agents, or the fracture faces are etched by a reactive fluid such as an acid, or both. These techniques allow hydrocarbons contained in the formation to more readily flow from the fractures into the well bore. The artificially created fractures may be complimented by naturally existing fractures, or by fractures caused by previous or simultaneous stimulation operations in the same or nearby formations. The quality of the fracturing operation obviously has a great effect on the overall success or failure of the well production.

In particular, horizontal oil and gas wells allow the extraction of valuable hydrocarbons at a minimum environmental "footprint", because more downhole zones can be grouped together from one surface location requiring fewer rigs and less surface area disturbance, subsequently making it easier and cheaper to produce the reservoir One of the tools commonly used by some operators of hydraulic fracturing equipment includes specially sized "frac-balls" or "drop balls", which are injected into a well to block the passage of a previously installed frac plug and therefore close off portions of a well to allow pressure to build up and cause fracturing in a target section of the well above the location of the well blocked by the frac-ball. The frac-plug (or bridge plug) is a downhole tool that is located and set to isolate the lower part of the wellbore. Frac-plugs are usually removable (via post frac milling operations) so that the lower wellbore section can be temporarily isolated from a treatment conducted on the upper section of the frac-plug (i.e. during fracing operations). Frac-balls may be made of various materials, including G-10 (or other related phenolics), Torlon, PEEK, and other high-temperature thermosets or thermoplastics.

Typically, the material selected is based upon the operators' experience and the chemistry and temperatures within the well. Frac-ball sizes are selected specifically to fit within the wellbore, frac plugs or sliding sleeves of the downhole tools which vary in diameter as the well sections progress from upper to lower sections.

For example, one popular method for creating multiple fractures in a weilbore is the use of frac ports & sliding sleeves. Openhole packers isolate different sections of the horizontal well. A sliding sleeve is placed between each packer pair and is opened by injecting a properly sized frac-ball inside the borehole. Typically, a completion string is placed inside the well. The string includes frac ports and openhole packers spaced to specifications. The spacing between packers may be up to several hundred feet. The packers are actuated by mechanical, hydraulic or chemical mechanisms. In order to activate each sleeve, a properly sized frac-ball is pumped along with a fracturing fluid inside the well. Each ball is smaller than the opening of all of the previous sleeves, but larger than the sleeve it is intended to open. Seating of the frac-ball exerts pressure at the end of the sliding sleeve assembly, causing it to slide and open the frac ports. Once the port is opened, the fluid is diverted into the openhole space outside of the completion assembly, causing the formation to fracture.

At the completion of each fracturing stage, the next larger frac-ball is injected into the well, which opens the next sleeve, and so on, until all of the sleeves are opened and multiple fractures are created in the well. The main advantage of this completion technique is the speed of operation, because it allows activating multiple fractures with a single completion string.

In some alternative completions, the sleeves are sometimes cemented into the hole with acid soluble cement, such that the sleeves are opened by pumping down acid and the fracing operation can thereafter be performed. Also, occasionally, in some other wells, the sleeves can be run with out packers if the formation is of the type that it can be counted on to provide isolation between the sleeves.

In any event) in all completions, the quality of the fracturing operation obviously has a great effect on the overall success or failure of the well production. Therefore, knowing current formation and/or wellbore properties can be a very important tool to optimize productivity of the hydrocarbon output and improve the quality and safety of for example, fracing operations. In particular, knowing what was or is happening downh6le at each of the perforations during the perforation and fracing process, maybe invaluable information in order to improve the quality and safety of the fracing process.

Accordingly, logging tools, such as disdosed in W02013/017859A2, are used downhole to record, for example, pressure and temperature data while fracing. The recorded data is then recovered by retrieving the data acquisition device(s) utilising specifically modified milling tools. These milling tools are arranged to mill away an outer part of the data acquisition device (typically the outer part which connects the device to the completion) and the milling tool also requires a suitable catcher mechanism that is adapted to recover the remaining part of the deployed data acquisition device and store it inside the modified milling tocil until pulled out of the wellbore back to the surface.

However) modification of the milling tools entail additional costs, and much more care has to be taken when operating the milling tool during recovery of the deployed data acquisition devices, so as not to cause any damage to the data storage part This can be very time consuming which inevitably leads to an increase of cost.

Accordingly, it is an object of the present invention to provide a downhole device and method for data acquisition and reliable data recovery after fracing operations, without having to physically recover the data acquisition device.

SUMMARY OF THE INVENTION

Preferred embodiments of the invention seek to overcome one or more of the above

disadvantages of the prior art.

According to a first aspect of the invention there is provided a downhole device for data acquisition during fracing operations, comprising: at east one data acquisition device, adapted to detect and record at least one physical property; a wireless data transceiver, operably coupled to said at least one data acquisition device; a controller, operably coupled to said wireless data transceiver and adapted to execute a wireless data transmission in response to an actuation signaL and a data acquisition device carrier adapted to accommodate said at least one data acquisition device, said wireless data transceiver and said controller.

This provides the advantage that data recorded downhole during, for example, a fracing operation, can be recovered from the deployed data acquisition device without having to physically retrieve the data acquisition device holding the recorded data. In particular, a standard milling tool may be equipped with a wireless transceiver (including data storage) that is programmed to transmit an actuation signal, or similar function, which, when received by the wireless data transceiver located at the deployed downhole device, initiates a wireless data transmission from the data acquisition device to the data storage of the milling tool) before the deployed downhole device is milled away and the milling tool proceeds to the next deployed downhole device (if any). Thus, minimal or no modifications of the milling tool or complicated mechanisms to physically recover and store the data acquisition device(s) are required. The recorded data is instead transmitted from one device to another upon receiving an actuation signal, or a type of toggle handshake, allowing for an efficient and speedy data recovery.

Advantageously, the controller may be adapted to selectively encode and/or compress the recorded data in response to the actuation signal.

Advantageously, the actuation signal may be an electromagnetic signal. Preferably, the actuation signal may be a wireless signal received from a remote wireless transceiver. Even more advantageously, the wireless data transceiver may be adapted to utilise any one of a Radio Frequency Identification (RFID), a Near Field Communication (NFC) and Bluetooth or any other suitable wireless data transmission system or protocol or wireless data transmission standard.

Preferably, the wireless data transmission may be initiated at a predetermined actuation signal strength. This provides the advantage that the data transmission is only initiated and executed at a sufficiently close distance between the deployed data acquisition device and the milling to& approaching the data acquisition device, thus allowing a more reliable & possibly a higher data throughput and ensuring minimum risk of data loss during transmission.

Advantageously, the data acquisition device may further comprise an integrated data storage device adapted to record a predetermined maximum amount of data.

Preferably, the data acquisition device may be adapted to wirelessly transmit the recorded data from said integrated data storage device to a remote location in response to said actuation signal via said wireless data transceiver. Even more preferably, the recorded data may be transmitted utilising any one of radio communication, free-space optical communication, sonic communication and electromagnetic induction communication.

Advantageously, the at least one data acquisition device may be any one or all of a pressure data acquisition device and/or a temperature data acquisition device and/or a geophone and/or a seismic sensor and/or flow device and/or resistivity or conductivity device. One or more of such devices would be located within, or attached to, the downhole device.

According to a second aspect of the invention there is provided a method for acquiring and recovering data during fracing operations in a subterranean formation having a welibore penetrating the formation, the method comprising the steps of (a] running in a downhole device having at least one data acquisition device according to the first aspect of the invention into a welibore; (bJ placing said downhole device at a location inside the wellbore; (c) initiating said at least one data acquisition device for monitoring and recording at least one physical property; (d) initiating a fracing operation while monitoring said at least one physical property; (eJ recording data of said at least one physical property in an integrated data storage device; and (fl transmitting said recorded data to a local and/or remote data storage device in response to receiving an actuation signal, utilising a wireless data transceiver operably coupled to said at least one data acquisition device.

Typically, the actuation signal may be provided by a remote wireless transceiver.

Preferably, the actuation signal comprises a toggle signal. Even more preferably, the actuation signal may be automaticafly initiated at a predetermined distance of said remote wireless transceiver from said at least one data acquisition device.

Alternatively, the actuation signal may be initiated manually at a predetermined distance of said remote wireless transceiver from said at least one data acquisition device. Yet, in another alternative embodiment, the actuation signal may be initiated at a predetermined signal strength received at said wireless data transceiver.

Advantageously, the recorded data may be downloaded utilising any one of a radio communication, free-space optical communication, sonic communication and electromagnetic induction communication. Typically, any suitable wireless transmission means is utilised to download the recorded data.

Preferably, the method may further comprise the step of (g) milling away said downhole device placed inside the wellbore utilising a milling tool after said recorded data has been transmitted to said remote data storage device.

Preferably, the method may frirther include step (a] comprising running in a plurality of said downh&e devices and may further include step (b) comprises placing said plurality of downhole devices at different depth locations and may further comprise repeating steps [cJ to (gJ for each downhole device wherein the milling tool is moved progressively deeper into the wellbore such that two or more downhole devices are milled in one or trip of the milling tool into and out of the wellbore.

Preferably, the remote data storage device and said remote wireless transceiver may be located at, mounted on or in or integral with or in line with or otherwise being included in the same workstring as said milling tool.

Alternatively, said remote wireless transceiver may be in data communication with a surface data transceiver device. Advantageously, said remote wireless transceiver and said surface data transceiver device are connected via a tool wireline and/or a separate wired connection and/or an optical fibre connection. Preferably, said surface data transceiver device comprises a data storage device. Even more preferably, said surface data transceiver device comprises data analysing means.

Alternatively, said wireless transceiver may be coupled to any one of a predetermined location on a coiled tubing bottom hole assembly, a wireline tool, a slickline tool, a tractor tool, a drill pipe and snubbing pipe bottom hole assembly (BHA).

According to a third aspect of the present invention there is provided a frac plug (or bridge plug) comprising a downhole device according to the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of an embodiment of a downhole device according to the present invention including a bypass sub, a data acquisition device carrier and wireless data acquisition device (inside the data acquisition device carrier and therefore not seen in Figure 1) and a centralizer; Figure 2 shows a cross sectional side view of the downhole device of Figure 1, but with an alternative centralizer; Figure 3 shows a perspective sectional view of the bypass sub of Figure 1 having a first flow path selectively closed by a drop ball; Figure 4 shows a sectional side view of the bypass sub of Figure 3 indicating a (fully open) flow path of the fluid from an uphole weilbore region to a downhole welibore region; Figure 5 shows a sectional side view of the bypass sub of Figure 3 indicating a (restricted) pressure bypass path of the fluid from an uphole wellb ore region to a data acquisition device and/or data acquisition device carrier when the first flow path is selectively closed by a drop ball; Figure 6 shows (a) a close up sectional side view of the data acquisition device carrier of Figure 1 and a data acquisition device (including wireless transceiver) placed inside the data acquisition device carrier, (b) a close up sectional view of the wireless data transceiver of the data acquisition device, and (c) a close up view of a pressure transducer; Figure 7 shows a sectional side view of another embodiment of a downhole device according to the present invention, with the bypass sub mounted to the uphole end of a frac-plug and two data acquisition devices placed in series one above the other inside the mandrel of the frac-plug, a wireless data transceiver is operably connected to both data acquisition devices (not shown); Figure 8 shows a sectional side view of the downhole device of Figure 7 (but with the outer most parts of the frac-plug and the data acquisition device not shown), where the bypass sub is mounted to the uphole end of an inner mandrel of a frac plug, where (a) shows the fluid flow from an uphole wellbore region through to a downhole wellbore region when the first flow path is open, (b) shows the fluid pressure path along a second fluid communication path, bypassing the first flow path, from an uphole wellbore region into a data acquisition device carrier (data acquisition device and wireless data transceiver not shown), and (c) shows a front view and section lines of (a) and (b); Figure 9(a) shows a cross-sectional side view of another embodiment of a downhole device according to the present invention, with the bypass sub mounted within and just below the uphole end of a frac-plug and one data acquisition device (induding wireless data transceiver, not shown] located inside the mandrel of the frac-plug; Figure 9(b) shows a different cross-sectional side view of the downhole device of Figure 9(a) but on a different cross-section plane and Figure 9(b) therefore shows the second fluid communication pressure path; Figure 10 shows a simplified schematic side view of the step of pumping the downhole device of the first aspect of the present invention downhole inside a welibore in accordance with the second aspect of the invention; Figure 11 shows a simplified schematic side view of the step of closing the first flow path of the downhole device of the present invention by dropping a drop ball into place, Figure 12 shows a simplified schematic side view of the step of recovering the recorded data in the downhole device in accordance with the first aspect of the present invention from the wellbore using a milling device (including a mountable wireless transceiver) and milling away the downhole device after data recovery, Figure 13 shows wireless data transceivers coupled to a Frac/Bridge plug at different locations; Figure 14 shows an example of a data recovery device including a module with the wireless data transceiver at a first location; Figure 15 shows another example of a data recovery device induding a module with the wireless data transceiver at a second location, and Figure 16 shows another example of a data recovery device induding a module with the wireless data transceiver at a third location, and wherein the wireless data transceiver is connected to the surface via a wire.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following definitions will be followed in the specification. As used herein, the term "wellbore" refers to a wellbore or borehole being provided or drilled in a manner known to those skilled in the art. The wellbore may be openhole' or cased', being lined with a tubular string. Reference to "up" or "down" will be made for purposes of description with the terms "above", "up", "upward", "upper", or "upstream" meaning away from the bottom of the welibore along the longitudinal axis of a work string and "below", "down", "downward", "lower", or "downstream" meaning toward the bottom of the wellbore along the longitudinal axis of the work string. Similarly, "work string" refers to any tubular arrangement for conveying fluids and/or tools from a surface into a wellbore. In the present invention, a "coiled tubing string" or a "drill pipe string" is the preferred work string. Also, the terms "downloading" and "transmitting" may be used interchangeably, wherein the term "wireless" refers to any transfer of information between two or more points that are not connected by a physical conductor (i.e. electrica' or optical].

Referring to Figures 1 to 6, a downhole device 100 is shown comprising a bypass sub tool 102, a data acquisition device carrier 104 and a centralizer 106. The downhole device 100 disclosed herein is one possible embodiment including a data acquisition device 108 capable of transmitting recorded data via a wireless data transceiver (i.e. receiver and transmitter]. The upper end of the exemplary bypass sub 102 of Figure 1 is adapted to be mounted to the lower end of any standard frac plug 10 and/or on any manufacturers frac plug. The data acquisition device carrier 104 of Figure 1 is operatively coupleable to the in use lower or downhole end of the bypass sub 102 and is adapted to provide a housing for at least one data acquisition device 108 (shown in Fig. 6(a)) including a data storage and wir&ess data transceiver (not shown). The centralizer 106 is mounted to the lower or downhole end 107 of the downhole device 100 and comprises) for example, a centralizer disc and an anti rotation stab 112.

Alternatively, and as shown in Figure 2, the centralizer 106 may comprise a flange-type member 114 having a depression 116 at the downhole end that is adapted to cooperatively engage with a matching counter part (not shown] coupled to the uphole end 109 of another downhole device 100. The centralizer 106 and matching counter part (not shown) engage such as to guide the downhole end 107 of an upper downhole device 100 into the uphole end 109 of a lower downhole device 100 during recovery of a plurality of bottom hole assemblies 100 placed within a wellbore as will be subsequently described in more detail.

As shown in Figure 2, the bypass sub 102 comprises a first fluid path 118 which in use is in fluid communication with the fluid flow through path of the frac plug 10 such as to provide a fluid path between an uphole region of the weilbore (that is, the welibore located above the plug 10) and a downhole region of the wellbore located below the plug 10. The first fluid path is selectively blockable by a drop ball 124 landing on a drop ball seat 121 (see Figure 3). The bypass sub 102 comprises a second fluid pressure path 120 bypassing the dropb all 124 such as to provide fluid communication (particularly to transmit pressure) between the uphole region of the wellbore and the interior cavity 122 of the data acquisition device carrier 104 even in the event the first fluid path 118 is blocked by the drop ball 124, thus allowing measurements of physical parameters of the uphole weilbore environment located above the frac plug 10 at all times during the fracing operation.

Figure 3 shows a detailed perspective section view of the bypass sub 102, the first fluid path 118, the bypassing second fluid pressure path 120 and drop ball 124. It is understood that the bypass sub 102 may comprise more than one first fluid path 118. Similarly, the bypass sub 102 may comprise more than one fluid pressure path bypass path 120.

The upper end of the bypass sub 102 of the downhole device 100 may be coupled to the lower end of the frac plug 10 via a fluid tight screw thread 125. The upper end of the data acquisition device carrier 104 is coupled to the lower end of the bypass sub 102 via a fluid tight screw thread 126. However, it is understood by the skilled person in the art that any other suitable connection may be used to mount the bypass sub 102 to the data acquisition device carrier 104 and to the plug 10. The data acquisition device carrier 104 and/or the plug 10 may be removably or permanently fixed to the bypass sub 102.

Referring to Figure 4, the first fluid path 118 through the bypass sub is shown in greater detail when there is no drop ball 124 blocking the first fluid path 118.

Figure 5. shows the second fluid pressure path 120 through into the interior cavity 122 of the data acquisition device carrier 104 when the drop ball 124 blocks the first fluid path 118; as can be seen in Figure 5, no fluid can flow along or through the second fluid pressure path 120 because the tower end of the cavity 122 is blocked.

Figure 6 shows a particular example of a data acquisition device 108 placed inside the data acquisition device carrier 104. Here, a pressure transducer 130 is located towards the uphole end of the data acquisition device carrier 104 and an interface unit 128 is place towards the downhole end of the data acquisition device carrier 104. The interface unit 128 may include a wireless transceiver (not shown), a controller (not shown] and a suitable memory data storage device (not shown).

This particular data acquisition device 108 requires no input to acquire data since the sensor is in monitor mode checking for pressure and temperature changes after a pre-determined period has lapsed for instance in between a second and some minutes such as every 2 minutes. Once a temperature and/or pressure threshold has been exceeded, the data acquisition device 108 automatically switches into record mode sending the acquired data to the memory data storage unit (not shown) at a pre-set sample rate. At the end of the acquisition, the data acquisition device 108 automatically switches off and goes back into its monitor mode. The data can now be downloaded from the data storage unit (not shown) via the wireless transceiver unit (not shown) upon receipt of an actuation signal sent from a remote location.

Figures 7 and 8 show an alternative downhole device 200, where the bypass sub 202 is located vertically above the frac plug 20 such that the in use lower (downhole) end of the bypass sub 202 is mounted to the in use uphole end of the frac plug 20 such that the at east one data acquisition device carrier 204 and/or data acquisition device 208 as well as the wireless transceiver (not shown) and controller (not shown) and data storage device (not shown) are located inside the mandrel 22 of the frac plug 20. In the example shown in Figure 7, two data acquisition devices 208 are placed inside a data acquisition device carrier 204 that is in fluid communication with a second fluid pressure path 220 (see Figures 8 and 9) from an uphole region of the wellbore above the plug 20 to the data acquisition devices 208 (not shown in Figure 8). Both data acquisition devices 208 are operably connected to the wireless transceiver (not shown] and controller [not shown) via the data storage device (not shown]. A first fluid path 218 runs through the bypass sub 202 and the frac plug 20 between an uphole region of the weilbore located above the plug 20 and a downhole region of the wellbore located below the plug 20 allowing fluid communication between the uphole and downhole region of the wellbore in the absence of a drop ball 224 blocking the first fluid path 218. If a suitably sized drop ball 224 is dropped into the fluid flow at surface, it will come to rest against the upper most end 221 or seat 221 of the bypass sub 202, in which case the first fluid path 218 is blocked, but the data acquisition devices 208 can still experience the parameters of the fluid (such as pressure and/or temperature) via the bypass path 220.

Note that Figure 8 omits to show a data acquisition device and data acquisition device carrier located below the bypass sub 202.

Figures 9(a) and 9(b) show an alternative embodiment of a downhole device 250 in accordance with the present invention, where the bypass sub 252 and the data acquisition device 258 are mounted within the throughbore of the frac plug 20 (rather than being mounted below the frac p'ug 10 as shown in Figure 2 or respectively above and within the frac p'ug 20 as shown in Figure 7 for that embodiment of the downhole device 200].

The bypass sub 252 is coupled via a screw thread 275 provided on its outer surface to a similarly shaped screw thread surface formed on the inner throughbore 21 of the frac p'ug 20. The lower end of the bypass sub 252 is coupled to the upper end of the data acquisition device carrier 254 via a fluid tight screw thread 276. Figure 9(a) shows frac ball or drop ball 224 as being seated on ball seat 271, but were the frac ball 224 is not present, the first fluid path 268 through the bypass sub 252 can be seen in Figure 9[aJ. Figure 9(b) shows the second fluid pressure path 270 as being present when the frac ball 224 is seated on the ball seat 271 where the second fluid pressure path 270 leads from the throughbore portion of the frac plug 20 located above the frac ball 224 and into the interior cavity 272 of the data acquisition device carrier 254. As can be seen in Figure 9(b), no fluid can flow along or through the second fluid pressure path 270 because the lower end of the interior cavity 272 is blocked. A membrane (not shown) is typically provided across the second fluid pressure path 270 at some point, where the cavity 272 is filled with clean hydraulic fluid and the membrane acts to seal that cavity 272 but also acts to communicate the pressure of the downhole fluid to the sealed hydraulic fluid.

Figures 9(a) and 9(b) also show the data acquisition device 258, such as sensors or gauges, as being housed within the interior cavity 272. The data acquisition device 258 is similar in form to the data acquisition device 108 as described above.

Figures 10 to 12 show the placement and operation of the downhole device 100, as well as, the automatic recovery (download) of the recorded data and removal of the downhole device 100, step-by-step. In particular, as shown in Figure 10, the downhole device 100 is mounted to the downhole end of a frac plug 10 and placed downhole into the wellbore in a region that is determined for perforation and a fracing operation by running them into the welibore 101 by conventional methods such as towering on wireline (not shown) or a tubing string such as coiled tubing (not shown) or pumped into the wellbore 101, wherein a plurality of downhole devices 100 may be placed in the required respective zone in a plurality of dedicated regions. The plug(s) 10 are then set in the conventional manner to seal against the inner surface of the wellbore 101. Perforation guns (not shown) associated with each downhole device 100 are then detonated in the conventional manner to create fractures within the formation. The pressure and temperature changes caused by the detonation may initiate the data acquisition of the data acquisition device 108, which also starts to record the data. Alternatively) the data acquisition devices 108 may be operated from the surface remotely) or may be on a timer to operate after a period of time has elapsed.

After a successful perforation, as shown in Figure 11, a first drop ball 124 is pumped downhole such as to engage with the seat 221 provided in the bypass sub 102 or 202 or 252 of a downhole device 100 or 200 or 250 and block the first fluid path 118 or 218 or 268. Subsequently, fracing fluid including proppants is then pumped downhole and into the fractures of the formation at extremely high pressure, while determining, for example, wellbore pressure and temperature using the data acquisition devices 108 or 208 or 258 by means of being in fluid communication via the second fluid pressure path 120 or 220 or 270. After completing the fracing operation of the first downhole device 100 or 200 or 250, a communication sub tool (not shown) may be moved downhole to wirelessly connect to the data acquisition device 108 or 208 or 258 and recover the recorded data via a near fieki transmission means such as RFID or other suitable means. Alternatively, the data may be recovered utilising a milling tool 30 having a wireless transceiver 400 mounted thereto.

A second smaller diameter drop ball 124 or 224, which is adapted to engage with the seat 121 or 221 or 271 ofa second, subsequently run in downhole device 100 or or 250, is then pumped downhole to block the first fluid path 118 or 218 or 268 of the second upper most downhole device 100 or 200 or 250 before repeating the fracing operation for that upper most downhole device 100 or 200 or 250 while recording, for example, well pressure and temperature for evaluation. These steps are repeated with further bottom hole assemblies 100 or 200 or 250 until all dedicated formation regions are perforated and fraced.

Once the fracing operations have been completed, as shown in Figure 12, a tool to mill away the bottom hole assemblies 100, 200 or 250, for example a milling device (i.e. a mill plug) 300, is run in downh&e, for example, on coiled tubing or a drill pipe string to recover recorded data of each of the data acquisition devices 108, 208 or 258 and thereafter respectively mill away each downhole device 100 or 200 or 250 in in its path starting with the uppermost one closest to the surface.

In particular, the milling device 300 may be equipped with a mountable wireless transceiver 400 [including a data storage device] that is adapted to send an actuation signal S towards the deployed downhole device(s) 100, 200 or 250. Once) the actuation signal S is received by the wireless data transceiver [not shown] of the data acquisition device 108, 208 or 258, the recorded data SDQta is transmitted to the wireless transceiver 400 mounted to the milling device 300. After all the data has been recovered to the data storage of the wireless transceiver 400, the milling device 400 then mills away the downhole device 100, 200, 250 to free up the welibore path to the next lower deployed downhole device 100, 200, 250, and repeat the wireless download procedure.

The actuation signal S may be a signal with a limited range that is transmitted continuously by the wireless transceiver 400. Thus, the actuation signal S is only received by the wireless data receiver of the data acquisition device 108, 208 or 258 when the mountable wireless transceiver 400 of the milling device 300 is at a predetermined distance, or the actuation signal SQ received at the data acquisition device 108, 208 or 258 is of a predetermined strength, therefore ensuring a stable wireless connection for data transmission with minimised risk of any data loss. In addition, only activating the wireless data transceiver of the data acquisition device 108, 208 or 258 when recorded data is downloaded minimises energy usage, thus potentially increasing the lifespan of the data acquisition device 108,208 or 258.

Alternatively, the actuation signal S may be sent manually by an operator, or at predetermined time intervals. Even more alternatively, the wireless download may be initiated when the milling device 300 manually contacts an actuator operably coupled to the deployed downhole device 100, 200 or 250 (e.g. a switch), in which case the wireless data transceiver and controller [not shown) are adapted to transmit all recorded data before the deployed downhole device 100, 200 or 250 is milled away.

When receiving the actuation signal Sa at the data acquisition device 108, 208 or 258, a controller (not shown) maybe adapted to execute transmitting the data from the data storage device (not shown) via the wireless data transceiver (not shown).

The controller (not shown) may also be adapted to, selectively (in response to the actuation signal containing additiona' information] or automatically, encode and/or compress the data before transmission, wherein the wireless data transceiver (not shown) may be adapted to modulate the data for transmission.

It is understood by the person skilled in the art that any suitable wireless technology may be used and any suitable data transfer protocol may be applied to transmit and receive the actuation signal) and transmit and receive the recorded data. Typical suitable wireless systems may utilise radio communication, Bluetooth, sonic communication, optical communication, electromagnetic induction, RFID (Radio Frequency Identification) and/or NFC [Near Field Communication).

Figure 13 shows an example of Frac / Bridge plug assembly with one or more possible locations for the data acquisition device and/or the wireless transceiver 400. Alternatively, the data acquisition device and/or the wireless transceiver may also be located within the plug, wherein the housing(s) of the data acquisition device and/or the wireless transceiver may be composed within the composite plug material.

Figure 14 shows an example of a data recovery device, such as a milling device 400, where the wireless data transceiver 400 is housed within a module 402 at some location within) for example, a coiled tubing bottom hole assembly (BHA), a wireline tool, slickline tool, tractor tool or drillpipe or snubbing pipe BHA. Thus various conveyance methods may be available to transport the recorded data to the surface.

Figure 15 shows another example of a data recovery device, such as a milling device 300, where the wireless data transceiver 400 is housed within a module 404 at a different location within, for example, a coiled tubing BFIA, a wireline tool, slickline tool, tractor tool or drillpipe or snubbing pipe BHA.

Figure 16 shows yet another example of a data recovery device, such as a milling device 300, where the wireless data transceiver 400 is housed within a module 406 at a different location within, for example, a coiled tubing BHA. a wireline tool, slickline tool, tractor tool or drillpipe or snubbing pipe BHA. Also, in this particular example, the wireless data transceiver 400 is connected to a surface transceiver (not shown) via a real-time link through an internal wire connection 500 or an optical fibre to the surface.

Alternatively, the wireless data transceiver 400 may be operably coupled to a wireline that is run downhole to the deployed downhole device 100, 200 or 250 in order to download the data wirelessly. The wireline is then pulled back to the surface before the deployed downhole device 100, 200 or 250 is milled away by the milling device 300. The wireline and coupled wireless data transceiver may be run through the throughore of a drillpipe string.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departing from the scope of the invention.

Claims

CLAIMS1. A downhole device for data acquisition during fracing operations, comprising: at least one data acquisition device, adapted to detect and record at least one physical property; a wireless data transceiver, operably coupled to said at least one data acquisition device; a controller, operably coupled to said wireless data transceiver and adapted to execute a wireless data transmission in response to an actuation signal, and a data acquisition device carrier adapted to accommodate said at least one data acquisition device, said wireless data transceiver and said controller.
2. A downhole device according to claim 1, wherein said controller is adapted to IC) 15 selectively encode and/or compress the recorded data in response to said actuation signal.
3. A downhole device according to any one of the preceding claims, wherein said actuation signal is an electromagnetic signal.
4. A downhole device according to any one of the preceding claims, wherein said actuation signal is a wireless signal received from a remote wireless transceiver.
5. A downhole device according to claim 4, wherein said wireless transceiver is adapted to utilise any one of a Radio Frequency Identification [RFID], a NearField Communication (NFCJ and Bluetooth.
6. A downhole device according to any one of the preceding claims, wherein said wireless data transmission is initiated at a predetermined actuation signal strength.
7. A downhole device according to any one of the preceding claims, wherein said data acquisition device further comprises an integrated data storage device adapted to record a predetermined maximum amount of data.
8. A downh&e device according to claim 7, wherein said data acquisition device is adapted to wirelessly transmit said recorded data from said integrated data storage device to a remote location in response to said actuation signal via said wireless data transceiver.
9. A downhole device according to claim 8, wherein said recorded data is transmitted utilising any one of radio communication, free-space optical communication, sonic communication and electromagnetic induction communication.

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10. A downhole device according to any one of the preceding claims, wherein said at least one data acquisition device is any one or all of a pressure data acquisition device and/or a temperature data acquisition device and/or a geophone and/or a seismic sensor and/or flow device and/or resistivity or conductivity device) and wherein one or more of said pressure data acquisition device, temperature data acquisition device) geophone, seismic sensor, flow device and resistivity or conductivity device are located within or attached to said downhole device.
11. A method for acquiring and recovering data during fracing operations in a subterranean formation having a wellbore penetrating the formation, the method comprising the steps of: [a) running in a downhole device having at least one data acquisition device according to any one of claims 1 to 10 into a wellbore; [b) placing said downhole device at a location inside the wellbore; [c) initiating said at least one data acquisition device for monitoring at least one physical property; [d] initiating a fracing operation while monitoring said at least one physical property; [e) recording data of said at least one physical property in an integrated data storage device; [fl transmitting said recorded data to a local and/or remote data storage device in response to receiving an actuation signal, utilising a wireless data transceiver operatively coupled to said at least one data acquisition device.
12. A method according to claim 11, wherein said actuation signal is provided by a remote wireless transceiver.
13. A method according to any one of claims 11 and 12, wherein said actuation signal comprises a toggle signal.

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14. A method according to any one of claims 11 to 13, wherein said actuation signal is automatically initiated at a predetermined distance of said remote wireless transceiver from said at least one data acquisition device.
15. A method according to any one of claims 11 to 13, wherein said actuation signal is initiated manually at a predetermined distance of said remote wireless transceiver from said at least one data acquisition device.
16. A method according to any one of claims 11 to 13, wherein said actuation signal is initiated at a predetermined signal strength received at said remote wireless transceiver.
17. A method according to any one of claims 11 to 16, wherein step (f] includes the use of a wireless transmission means to download said recorded data.
18. A method according to claim 17, wherein said recorded data is downloaded utilising any one of a radio communication, free-space optical communication, sonic communication and electromagnetic induction communication.
19. A method according to any one of claims 11 to 18, further comprising the step of: [g] milling away said downhole device placed inside the wellbore utilising a milling tool, after said recorded data has been transmitted to said remote data storage device.
20. A method according to any one of claims 11 to 19, wherein step (a) further comprises running in a plurality of said downhole devices and step [b) further comprises placing said plurality of downhole devices at different depth locations; and wherein said method further comprises repeating steps [c] to [gJ for each downhole device, wherein the milling tool is moved progressively deeper into the weilbore such that two or more downhole devices are milled in one trip of the milling tool into and out of the wellbore.IC) 15
21. A method according to claim 20, wherein the remote data storage device and the remote wireless transceiver are located at) mounted on or in or integral with said milling tool, or in line with or otherwise being included in the same r
22. A method according to claim 21, wherein said remote wireless transceiver is in data communication with a surface data transceiver device.
23. A method according to claim 22, wherein said remote wireless transceiver and said surface data transceiver device are connected via a tool wireline and/or a separate wired connection and/or an optical fibre connection.
24. A method according to any one of claims 22 and 23, wherein said surface data transceiver device comprises a data storage device.
25. A method according to any one of claims 22 to 24, wherein said surface data transceiver device comprises data analysing means.
26. A method according to claim 11, wherein said wireless data transceiver is coupled to a predetermined location on any one of a coiled tubing bottom hole assembly, a wireline tool, a slickline tool, a tractor tool, a drill pipe and snubbing pipe bottom hole assembly (BHA].
27. A frac plug comprising a downhole device according to any one of claims 1 to 10. IC) r