Abstract:
An inflation verification system for an inflatable tool includes at least an information collector associated with the inflatable element of the inflatable tool connected to a controller with a predetermined set of instructions for inciting communications with the surface. Communicators contemplated include atmospheric chambers which when opened create a negative pressure pulse which propagates to the surface. More than one chamber increases the number of pulses generable and thus the amount of information conveyable. Alternative preferable communicators are electromagnetic pulse generators and acoustic telemetry. An advantage of acoustic telemetry is that more quantitative information is transmittable. Other downhole communication methods are also employable.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 60/066,602, filed Nov. 26, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to method and apparatus for verifying positive inflation of inflatable tools such as packers. More particularly, the invention relates to installing sensors within the inflatable tool, connecting the sensors to a controller which when it receives information from the sensors communicates the information to the surface using a device or procedure capable of so communicating. 
     2. Prior Art 
     Past methods for verifying positive inflation of inflatables such as an external casing packer (ECP) have been to monitor the pressure gauge employed to measure the applied pressure to inflate the packer. The applied pressure is provided either through an internal tubing string using an inflation tool or by pressuring the casing string in which the ECP is installed. When the ECP opens and begins inflating, fluid in the pressurized column begins to rapidly disperse in an amount equal to the displacement of the inflating packer. Where the ECP is large or is being inflated in a hole that is significantly larger than the outside diameter of the ECP in the uninflated condition the displaced fluid is of a relatively large volume. A large volume of fluid moving out of the pressurized column creates a pressure drop. The pressure drop occurs suddenly and is recognized by the gauge measuring the applied pressure. As long as the displaced volume is large the pressure drop is easily measured and noted and the setting of the packer is confirmed with high confidence. The method has been used for many years successfully and reliably on all larger ECP applications. Unfortunately, however, where the ECP is being set in a hole not much larger than its own uninflated outside diameter, the amount of fluid displaced into the packer is too small to be recorded by the gauge monitoring the applied pressure. This is not to say that the displaced fluid does not actually produce a pressure drop because indeed it does, it simply is to say that the drop in pressure is small because the displacement of fluid is small and the gauge employed to monitor applied pressure at many locations does not have sufficient resolution to detect the drop. Inflation of ECP&#39;s set in this type of environment cannot be confidently verified. 
     One prior art method that has been attempted to confirm positive inflation of an ECP in a hole not much larger than its own uninflated outside diameter is to measure displaced fluid from surface tanks. In situations where there is a long fluid column however, and the amount of fluid for inflation is very small the percentage of fluid depletion in the tanks may not be within a measurable range with equipment common at drilling sites. Therefore, the art is in need of a system for confidently verifying inflation of an inflatable tool such as an ECP which is inflated with a relatively small amount of displaced fluid. 
     Another prior art method to provide information about ECPs is not direct, but as a confirmation system. More specifically, memory pressure gauges are placed in an inflation tool and measure pressure in the packer. The gauges remember the pressure and can be downloaded after removal of the packer. Drawbacks to the system are that there is no real time information and the gauges only measure pressure. They do not in fact measure whether or not inflation has taken place. Thus the information supplied is helpful but not conclusive and not timely. 
     SUMMARY OF THE INVENTION 
     The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the method and apparatus of the invention. 
     The inflatable tool inflation verification system of the invention comprises employing an information collector in the interior of the inflatable tool or proximate thereto such as a pressure sensor or a fluid flow device such as a turbine. The pressure sensor would be calibrated to send a signal to a downhole controller in proximity with the inflatable tool when a predetermined pressure within the inflatable tool is reached or the flow device would send a signal when a predetermined volume of fluid (sufficient to fill the tool) has entered the tool. The controller activates a communication device to send confirmation of inflation to the surface. The addition of these devices makes for high confidence verification of inflation of ECPs inflated in holes not much larger than the ECPs uninflated outside diameter. 
     Confirmation may be sent to the surface in a number of ways but in one preferred method, which is preferred because it enables employing the same surface equipment, is to program the controller to open an atmospheric chamber of about 150 to about 250 cubic inches in volume attached to the inflatable tool itself which displaces fluid into the chamber and thus creates a pressure drop. The drop is significant because the differential between atmospheric pressure and the ambient pressure can be 5000 psi or more. This can be largely different from the pressure drop while inflating an ECP because the ECP inside the element is at well pressure as opposed to atmospheric pressure. Thus the pressure drop in the ECP will only be perhaps 1000 psi. As is appreciated it is more difficult to measure a 1000 psi drop than a 5000 psi drop in pressure. The pressure drop caused by flooding of the atmospheric chamber is easily measurable by a commercially available specially sensitive differential pressure monitoring gauge employed in the invention. Due to the method and apparatus of the invention, the verification of inflation of inflation tools employing only a small amount of displaced fluid (as well as larger ECPs) can be confidently confirmed. This is a great benefit to the industry both because it provides for verification of inflation and additionally the invention enables the use of conventional surface techniques with the improved equipment. In addition, more atmospheric chambers could be provided to add to the information gained at the surface. 
     Other modes in which confirmation may be sent to the surface are by supplying an electromagnetic pulse generator in the vicinity of the inflation tool and operably connected to the controller and by using acoustic telemetry through the pipe. 
     Although the foregoing summary of the invention discusses external casing packers specifically, it should be understood that any type of inflatable tool can benefit from the invention. As such, the detailed description which follows is directed generically to inflatable tools/inflatable elements. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is a schematic representation of the invention. 
     FIGS. 2-7 are an elongated view of a particular embodiment of the invention in the run in position. 
     FIGS. 8-13 are an elongated view of a particular embodiment of the invention in the partially actuated position; and 
     FIGS. 14-19 are an elongated view of a particular embodiment of the invention in the fully actuated position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention solves an old problem by causing the parameters of the problem to fit into old methods thereby alleviating the problems. More specifically, by employing devices capable of measuring fixed parameters such as volume of fluid following therepast or pressure internal to an inflated tool and a controller to generate communication to the surface the problem of a low fluid displacement inflatable tool is solved. FIG. 1 is referred to provide an understanding conceptually of the components of the system hereinafter described in detail. 
     In all of the embodiments of the invention which follow, a sensor  14  or other type of information collector is employed within or adjacent an opening (not shown) in the inflatable tool which serves to allow fluid to enter the tool to inflate it. One preferred sensor is a pressure sensor disposed preferably adjacent to the packer. The sensor is preprogrammed to include a threshold differential pressure between the tool and the annulus before sending a millivolt impulse signal to the downhole controller  16  which, in turn, will activate the communicator  18 . The pressure differential programmed into the sensor will be that pressure which has been predetermined to provide complete inflation of the inflatable tool. One of the other types of information collectors presently preferred is a fluid displacement device which would be located at the entrance to the inflatable portion of the inflatable tool. The device would replace or be in addition to sensor  14  and therefore is contemplated in the same flow chart box as is identified by numeral  14 . In the case of the fluid displacement device, the amount of fluid flowing therepast is measured and when a threshold amount has passed, having been determined previously to be sufficient to completely deploy the inflatable element, the device sends an impulse to the controller  16  and the process continues as set forth above. In another embodiment of the invention, one or more strain gauges are employed as the sensor  14 . These gauges are preferably mounted directly in the rubber cover of the packer and measure contact pressure with the open borehole or cased holes. Each of these embodiments of information collection are disposed proximately to where the information can most easily be accessed and therefore are quite reliable. With either embodiment the controller  16  is clearly advised that the inflatable tool  12  is deployed. 
     Communicating the information contained in the controller to the surface can be accomplished in a number of ways through a communicator  18  but preferably is by opening an atmospheric chamber, generating an electromagnetic pulse or by employing acoustic telemetry. 
     In the first preferred communication embodiment, a atmospheric chamber of about 150 to about 250 cubic inches in volume is built into the inflatable tool or is in a sub attached to the tool in proximty thereto. The chamber is openable at the instance of the controller. The atmospheric chamber is in effect the communicator  18  because when the chamber opens due to an action of controller  16 , the chamber is rapidly flooded with fluid sufficiently to create a negative pressure pulse that is easily readable at the surface by surface detector  20 . In this embodiment, surface detector  20  is a specially sensitive gauge the same gauge monitoring applied pressure. The pressure pulse read by detector  20  is then relayed either electronically to a computer  22  or directly to a technician by sight. 
     In an alternate iteration of the first embodiment, two atmospheric chambers are provided. The two chambers are opened at different times, the lapse of time between each negative pressure pulse produced thereby being correlated to the amount of actual pressure within the inflatable element. This provides valuable information uphole about the actual status of the inflatable element. In operation, the sensor or other information device  14  generates an impulse at a first differential value as discussed above. This is communicated to the controller which may immediately open a chamber or may time delay the opening to provide an opportunity for shut down of the rig pump. The pressure pulses are then more easily read at the surface. The first differential value is a minimum amount of pressure or fluid influx (or other predetermined parameter) to the inflatable element  12 . In this alternate construction, a second impulse is generated when pressure stops climbing or fluid ceases to move into the element at a predetermined appreciable rate. Controller  16  is preprogrammed with a series of possible pressure ranges and is directed to open a second chamber a predetermined amount of time after the first depending upon which preprogrammed pressure range the sensor has signaled to the controller. Where a time delay for opening the first chamber is used to get beyond the time pumping is occurring, each of the signals will be easily measured at the surface and the time between the signals will provide information as to which final pressure range the element is in (e.g. between 875 and 925 psi the controller will wait 60 seconds between opening of chambers). 
     It should be understood that while the negative pressure pulse method of the invention is preferred, other methods are also available. For example, other preferable methods are to employ acoustic telemetry or electromagnetic pulse technology. Moreover, other downhole communications technology can also be adapted to be employed in the invention. 
     With respect to acoustic telemetry, additional quantitative benefits are realizable such as the ability to transmit annulus pressure; inflatable tool temperature, the degree to which the tool is inflated, etc. Of course it is necessary to provide sensors to read these parameters but information from as many sensors as are desired is transmittable via acoustic telemetry. 
     In the acoustic telemetry embodiment the communicator  18  is an acoustic transmitter and the surface detector  20  is an acoustic receiver. Basic acoustic telemetry is known to the art. 
     Another alternative communication method contemplated For the present invention is electromagnetic pulse technology. In employing this communication method the communicator  18  is an electromagnetic pulse generator and the surface detector  20  is adapted to receive the wavelengths produced. 
     In a particular embodiment of the negative pulse method and apparatus of the invention, referring to FIGS. 2-19, FIGS. 2-7 illustrate the tool in the first condition where two atmospheric chambers are sealed; FIGS. 8-13 illustrate the tool in a second condition where the first atmospheric chamber has been opened and the second atmospheric chamber is still closed; and FIGS. 14-19 illustrate the tool with both atmospheric chambers having been opened and the tool in its fully set and permanent position. 
     At the downhole end of the tool of the invention is attached conventionally a valve collar  100  and an inflatable packer  102 . These are well known to the art and do not require explanation except to note that a pressure pathway  104  is provided in collar  100  to facilitate the function of the invention. Collar  100  is in contact with a connector sleeve  106  having an inflation and pressure test port  108  and o-ring seals  110 . Port  108  leads to annular chamber  112  which is fed pressure through pathway  104  and terminates at conduit  114  leading to differential pressure transducer  116 . Chamber  112  is formed by a space between connector sub  106  and transducer sub  120  relative to mandrel  122 . Transducer housing  120  is also pressure sealed to mandrel  122  by o-ring seals  110 . It should be noted that the pressure transducer  116  is a differential pressure transducer and so must be provided with pressure conduits leading to distinct pressure sources. The first has already been described and corresponds to the pressure inside the inflatable element of the packer  102 ; the second source of pressure is wellbore pressure and is accessed through a pair of ports  124  through cover sleeve  126  which extends over the transducer housing  120 . Fluid from the wellbore fills the chamber  130  defined by the cover sleeve  126 , transducer housing  120  and mandrel  122 . An electrical connector such as a single pin connector  132  provides electrical/communication connection to pressure transducer  116  via wire (not shown). Connector  132  communicates through transducer housing  120  to microprocessor  134  by a conductor housed in conduit  133 . This is the sensory portion of the invention and functions as follows: Pressure transducer  116  measures differential pressure between the internal space of the inflatable element of packer  102  and the wellbore pressure of chamber  130 . The information sensed is communicated through the pathway indicated to microprocessor  134 . Microprocessor  134  is programmed to allow current from battery pack  136  to run to the communication portion of the invention discussed hereunder only under specific circumstances and at specific times. Microprocessor allows current to run to a first pulse generator upon a 200 psi differential being sensed between the internal packer pressure and wellbore pressure, the packer being at the higher pressure and a second pulse generator at a second selected value of pressure differential between the two identified pressure sources and which is timed relative to the first pulse according to a predetermined ratio More specifically, the time between first and second generated pulses is directly related to the differential in pressure from the 200 psi threshold pulse and the ending packer pressure pulse. Specific knowledge as the ending pressure in the packer is in this way obtainable at the surface. It is preferable that the sequence of the microprocessor is delayed for some period of time of about five minutes after suspected setting is accomplished. Such a delay allows the well to “settle” after the pump has shut down which makes the pressure pulse communication method of the invention is easier to read at the surface. 
     The communication portion of the invention is responsive to triggering by microprocessor  134 . Specifically, the embodiment employs two atmospheric chambers  140  and  142 . Microprocessor  134  and battery pack  136  are disposed within chamber  142 . Chamber  140  is defined by housing connector  144 , mandrel  122  and outer housing  146  whereas chamber  142  is defined by mandrel  122 , transducer housing  120  and outer housing  146 . The chambers are divided by bulkhead  148  of mandrel  122  which extends radially from mandrel  122  to seal against outer housing  146  with o-rings  110 . Signals and power are transmitted through bulkhead  148  by conductor  149  and connector  151 . Each chamber is provided with its own opening actuation device which is operable upon command from the microprocessor so that a negative pressure pulse is created. The devices are identical and are merely oppositely disposed. The first actuator includes locking dogs  150  mounted to a piston  152 , which dogs are forced into engagement with groove  154  by Kevlar wire  156 . In this condition piston  152  is maintained in a blocking position over plugs  158  in ports  160 . Piston  152  is also in compressive contact with spring  162  which is charged so that piston  152  will be pushed off plugs  158  upon release of locking dogs  150 . Preferably a spring guide pin  164  is provided as seen in FIG.  9 . 
     The Kevlar  156  (high tensile strength, low heat resistance) is burned by current supplied by battery pack  136  on command of microprocessor  134  and delivered to a resistor element (not shown), which releases the dogs  150 . Spring  162  then pushes piston  152  off plug  158  as stated. Plug  158  is only inserted into port  160  and so will easily be urged out of port  160  by the tremendous differential pressure between atmospheric chamber  140  at 14.7 psi and wellbore pressure which maybe many thousands of pounds of pressure per square inch. The atmospheric chamber  140  thus is immediately flooded with wellbore fluid. A pressure drop pulse is created hereby which will propagate to the surface signifying that about  200  psi has been registered in the packer as sensed by the transducer  116 . 
     The second atmospheric chamber  142  is employed to provide information about how much ending pressure is within packer  102 . Since second chamber  142  operates identically to chamber  140 , but in the opposite direction in this embodiment, a second negative pressure pulse will be received at the surface upon activation thereof The elements are identified as similar and distinguished by changing the first number to the two hundred series, to wit: Dogs  250 ; piston  252 ; groove  254 ; Kevlar  256 ; plug  258 ; port  260 ; spring  262 ; and pin  264 . Microprocessor  134  is programmed to allow a certain period of time to pass between flooding each chamber, which time is directly correlated to the amount of pressure in the packer above the pressure signaled by flooding the first chamber, in this embodiment, about 200 psi. For example, if the ending pressure in the packer happens to be 500 psi above wellbore pressure and the threshold pressure is 200 psi, the first chamber  140  will be flooded and three minutes later the second chamber  142  will be flooded. In this example, each minute of delay signifies 100 psi differential pressure over wellbore above the threshold pressure. By timing the negative pressure pulses then, (the pulses will travel at the same speed through the fluid column) a surface crew is able to verify precise set pressure of the packer. 
     It should be noted in this embodiment that chamber  140  is flooded first only because chamber  142  houses the microprocessor and battery pack and once flooded, these items rapidly become inoperable. 
     For completeness, the uphole end of the tool includes top sub  170  which is threaded to mandrel  122  at thread  172  and maintained there with set screw  174 . Seals are supplied in the illustrated positions to maintain specific pressure areas separate as is understood by one of skill in the art. 
     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 illustration and not limitation.