Abstract:
A conventional thru tubing bridge plug is rendered in a more effective and useful downhole tool by incorporating a sensor module complete with preferably a plurality of downhole sensors to monitor downhole parameters such as but not limited to temperature and pressure both within the inflatable tool and in the annulus of the well created thereby.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 60/198,605, filed Apr. 19, 2000 which is fully incorporated herein by reference. 
    
    
     BACKGROUND 
     Thru tubing retrievable bridge plugs provide a means of temporarily plugging selected sections of a well, without the need for pulling production tubing. Avoidance of the need to pull the production tubing dramatically reduces costs associated with plugging particular sections of a well. Different sections of a well might need to be plugged because of, for example, water breakthrough, gas production, etc. Retrievable bridge plugs are also run to plug certain sections of a well in order to test different fluids flowing into the well at that location or above that location from shallower zones within the wellbore. Such bridge plugs generally include a lower valve which provides a seal, blanking off a section of mandrel so that a packer element, also contained within the retrievable bridge plug, can be inflated. The packing element provides for the plugging off of the selected sections of the well. The construction and use of a conventional bridge plug is considered known to one of ordinary skill in the art. Such bridge plugs are commercially available from many sources including Baker Oil Tools, Houston, Tex. (Product Nos. 340-10 and 330-72). 
     SUMMARY 
     The above-identified drawbacks of the prior art are overcome, or alleviated, by the intelligent bridge plug system of the invention. 
     The present invention avails itself of the benefits evident in conventional retrievable bridge plugs and further provides a method and apparatus for accurately setting the inflation pressure of a retrievable bridge plug and verification of that setting. The apparatus of the invention is a thru tubing bridge plug having downhole instrumentation and employing an electric wireline setting tool such as that disclosed in co-pending U.S. Ser. No. 60/123,306, filed Mar. 5, 1999, the entire contents of which is incorporated herein by reference. The device further comprises several sections of a retrievable bridge plug and several downhole sensors. The sensors are worked into the tool preferably in a sensor module which is a part of the retrievable bridge plug assembly. The sensor module is located in different sections of the tool for different embodiments as disclosed hereinbelow. The tool of the invention preferably measures element inflation pressure, temperature inside the packer and the annulus temperature as well as pressure uphole of (above) and downhole of (below) the packer. These parameters of the well may be used to ensure a proper setting of the inflatable element and thereby ensure that the bridge plug operates as intended. The invention provides a superior advantage over the prior art for many reasons including that the temperature of the inflation fluid is nearly always cooler than the temperature downhole. If a packer is fully inflated with relatively cooler fluid, the thermal expansion of that fluid subsequent to filling could rupture the element. Such occurrence could be problematic and would preferably be avoided. The present invention provides the means to avoid such a condition and also will provide a high degree of confidence that the inflatable element is properly inflated every time the bridge plug is employed. 
     It is also important to note that one of the key points in measuring pressure below the bridge plug is to determine how the well is responding to the plug. This is an important benefit of the invention not heretofore available; comparing pressure above the plug with pressure below the plug which provides information about whether or not a zone has been effectively shut off and whether or not the packer has achieved a good seal. The existence of leaking through the casing or through fractures in the formation, etc. would be identified by comparing the above and below pressure. Moreover, the comparison indicated above provides information about whether or not pressure below a plug is being adversely affected by other wells in a situation where production wells and injection wells are operating in the same field. Furthermore, by monitoring all three of above the plug pressure, below the plug pressure and element inflation pressure verification can be obtained that the inflation pressure ratings for the element being employed have not been exceeded. 
    
    
     IN THE DRAWINGS 
     FIGS. 1-5 are an elongated view of a cross-section with a first embodiment of the invention; and 
     FIGS. 6-10 are an elongated view of a cross-section of a second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-5, a first embodiment of the invention is illustrated. It will be appreciated by one of ordinary skill in the art that FIGS. 1 and 2 and FIGS. 4 and 5 depict portions of the inventive bridge plug that are identical to a prior art bridge plug commercially available from Baker Oil Tools, Houston, Tex., under Product Nos. 340-10 and 330-72. Since these portions are very well known to the art, a detailed description thereof is not necessary to a full understanding of the invention. For orientation and clarity, one of skill in the art will recognize upper valve sleeve  12 , valve shaft  14  and equalizing mandrel  16  in FIG.  1 . In FIG. 2, bumper housing  18  and associated components will be recognized. 
     Referring now to FIG. 3, the sensor module  30  of the invention is illustrated. Sensor module  30  is important to the function desired in the present invention since it houses all of power, telemetry and sensor assemblies. Module  30  is essentially “cut into” the conventional tool in the position, in this embodiment, illustrated by FIGS. 1-5. Where bumper housing  18  would be connected to collet sub  20  in a prior art tool, the sensor module  30  is connected therebetween. It is important to note that collet sub  20  is modified in the invention to provide pressure paths which allow the sensing desired in the invention to take place. Poppet housing  22  is also modified, again to provide a pressure path for the sensing desired in the invention. Pressure is measured at the back side of the poppet to obtain accurate element pressure. The balance of the tool in this embodiment, referring to FIGS. 4 and 5 is conventional. One of skill in the art will recognize spring housing  24  connected to poppet housing  22  and element  26  connected to spring housing  24 . Guide  28  is shown at the downhole end of the tool at the right side of FIG.  5 . 
     Referring back to FIG. 3, the detail of the invention is discussed. At the box thread  32  of bumper housing  18 , an uphole end of sensor module  30  is provided with a pin thread  34 . The pin thread  34  is actually cut on a mandrel  36  of sensor module  30 . Mandrel  36  is connected at its downhole end at pin thread  38  to collet sub  20  via box thread  40 . Mandrel  36  is made pressure tight between tubing pressure and exterior wellbore pressure by o-rings  42  and  44  on the uphole and downhole ends thereof, respectively. Since sensitive electronic equipment must be delivered to the downhole environment in this tool, it is necessary to create a sealed chamber which may be atmospheric or hydraulic fluid filled. The chamber is numeraled  46  and is formed annularly between mandrel  36  and sleeve housing  48 . Sleeve housing  48  shares an o-ring with mandrel  36  at  42  and is provided with an additional o-ring  50  at an outer surface of collect sub  20 . Chamber  46  is filled, in the invention, with a transmitter  52  locked in a desired position as shown by locking ring  54  which is threadedly connected to mandrel  36  at thread  56 . Transmitter  52 , preferably a piezo ceramic transducer, is connected via contacts (not shown) to an electrical control module with signal receiver  60  which is connected to battery pack  58 . The control module regulates power to the transmitter  52 , receiver  60  and the pressure transducers. Typically, a sine or square wave is sent to the transmitter to create either pulser or frequency acoustic outputs. It should be noted that several different control modules  60  or a single annular one may be employed. It is preferable to employ several modules  60  to reduce cost of manufacture. Constructing annular circuit boards for modules is expensive. The one or more modules  60  are connected to pressure transducers  62  and  64  which each monitor pressure in a different place via pressure pathways as shown. Pressure transducer  64  is “plumbed” to element pressure via pathway  66 . Numeral  66  is repeated several times in the drawings to indicate the pathway. It will be noted that plug  68  is provided to close annular pressure from conduit  66 . The plug is needed as a consequence of the manufacturing process for creating the pressure pathway  66  to element pressure. 
     In the case of pressure transducer  62 , a pressure pathway  70  is provided which is left open to annulus pressure at port  72 . This transducer will sense annulus pressure above the element  26  (FIG.  5 ). Differences between this pressure location and pressure below the element provides information about the setting of the element  26 . Pressure below the annulus is measured by a similar set of components which cannot be seen in this drawing but will be understood to one of skill in the art by exposure to the shown component sets illustrated. 
     The tool as described is operable in several modes. One mode is a continuous data stream mode wherein the transmitter of the invention transmits acoustic (radio wave, electromagnetic wave, vibration or other) data at all times. As required or desired, a receiver is run in the hole to acquire the acoustic (radio wave, electromagnetic wave, vibration or other) signal and transmit data uphole. It should be noted that in situations where it is physically possible for the signal from the transmitter to reach the surface on its own, a receiver can be positioned at the surface. In another mode of operation of the invention, data is stored downhole until a signal to transmit is received by the tool. The signal could be generated at the surface and sent downhole or generated downhole by a receiver run in the hole for that purpose and for retrieving the data released. 
     In another embodiment of the invention, referring to FIGS. 6-10, a sensor module is differently configured and is located in a position within the otherwise conventional (except for pressure pathways) bridge plug. Power and communication is provided through an inductive coupler coil discussed hereunder. In this embodiment, it is the uphole end of the tool which is most modified from its conventional cousin. For clarity, conventional components such as upper valve sleeve  80 , lock segments  82 , extension spring  84  and equalizing mandrel  16  are numbered. All other downhole components of the tool are conventional except for pressure pathways as noted in each of the figures. Pressure pathways are numbered in numerous places on the figures to provide an understanding to one of ordinary skill in the art as to the precise location thereof. 
     Focusing on the sensor module  90  in this embodiment of the invention, a sensor housing  92  has an uphole profile  94  to act as a fishing neck which functions as is known in the art. It will be appreciated that in prior art bridge plugs the fishing neck would be threaded directly to the equalizing mandrel  16 . In the invention however, the equalizing mandrel  16  is threadedly connected to a porting sub  95  threadedly connected to sensor housing  92  at thread  96  and inner mandrel  98  at thread  100 . The connections to porting sub  95 , as stated, are sealed with o-rings  102 . 
     A chamber  104  is created between inner mandrel  98  and sensor housing  92  which is sealed at the uphole end by o-ring  106  against an i.d. of sensor housing  92 . Within chamber  104 , electronic equipment similar to the first discussed embodiment is disposed. At least one electronic control module(s)  108  is connected to pressure transducers  110  and  112 . Pressure transducer  110  is connected to pressure pathway  114  which leads to annulus pressure downhole of the element  26 . Plug  118  is required incident to the manufacturing process to prevent annulus pressure above the element  26  from being registered. Conversely, pressure transducer  112  measures pressure in the annulus uphole of element  26  through pressure pathway  120  which has access to annulus pressure through port  122 . 
     In this embodiment, power is provided to the electronic components enumerated above via an inductive coupler coil  124 . Power will thus be initiated at the surface or another remote power source. Since batteries are not the limiting factor on the life of this tool regarding testing of the parameters readable by the electronics therein, readings may be performed at any time, even many years after installation of the tool simply by providing power via a complementary coil (not shown). The sensors so powered can then communicate with a remote location or store data for later retrieval through the inductive coupler which in such an embodiment is employed as a communication link to a remote location. In one embodiment, the inductive coupler will not supply power at all but rather will act solely as a communications pathway and will function to extract data from the bridge plug whether the data is stored or is being actively recorded. 
     In yet another embodiment of the invention, transmission of data is forsaken entirely. More specifically, a battery pack is utilized to power the tool and data is stored on the control module. This activity would continue as long as the battery pack supplies energy. Further the data storage could be continuous or could be at time intervals. Subsequently, when the bridge plug is pulled out of the well, the stored data on the control module could be downloaded for review and/or analysis. It will be appreciated that other sensors for parameters such as gamma radiation, temperature flow and other element or formation parameter may be added to any embodiment hereof. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.