Abstract:
A hydrophone free from internal leads and further including a stabilizing jacket is described. The hydrophone uses the metallic end caps of the stabilizing jacket to complete the circuit thereby eliminating the need for internal leads. Further, the stabilizing jacket results in a hydrophone configuration that can withstand harsher conditions while nonetheless providing excellent detection capabilities.

Description:
[0001]    The present disclosure describes a new sensor construction and more particularly, a hydrophone configuration that, in one embodiment, can be used in logging-while-drilling (LWD) systems. 
         [0002]    Many applications exist for hydrophones and other pressure pulse sensors. One common use for hydrophones is in sonar detecting devices, like those that are used to detect submarines. A hydrophone uses transducers to convert a pressure wave (e.g., a sound) to an electrical signal. Hydrophones now find use in many environments. They are currently used, in such diverse areas as the deep ocean to measure seismic activity and in oil wells, to measure fluid characteristics. While the sensors as described will be discussed within the context of their use in an oil well, they can be used in any environment where a typical hydrophone would be used and, in some environments that could not previously be studied using a traditional hydrophone due to its fragility. 
         [0003]    Unfortunately, conventional hydrophones and other pressure sensors are fragile. They generally do not respond well to low frequency pressure waves and are sensitive to movement of the tools carrying the sensors. The fragility and tool movement sensitivity problems are undesirable in any environment, but are particularly detrimental in an oil well or downhole environment where tool movement, shock and vibration, temperature extremes, and erosive mud flow are common. Additionally, where a pressure sensor is used in a downhole signal transmission system, the lack of low frequency response is very undesirable since it is known that pressure pulses are attenuated far less at low frequencies and, therefore, low frequency signals may be transmitted greater distances. Thus, it would be a significant improvement in the art to provide a pressure sensor that is robust and that is less sensitive to environmental fluctuations. 
         [0004]    A better understanding of the various disclosed system and method embodiments can be obtained when the following detailed description is considered in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic diagram of a logging-while-drilling environment according to an illustrative embodiment; 
           [0006]      FIG. 2  is a schematic diagram of a logging environment according to an illustrative embodiment; 
           [0007]      FIG. 3  is a cylindrical hydrophone according to an illustrative embodiment; 
           [0008]      FIG. 4  is a cylindrical hydrophone enclosed in a stabilizing jacket according to an illustrative embodiment; 
           [0009]      FIG. 5  is a cut away view of the hydrophone of  FIG. 3  and stabilizing jacket of  FIG. 4 ; 
           [0010]      FIGS. 6 and 7  are enlarged views of the a electrical connections of the hydrophone of  FIG. 3 ; 
           [0011]      FIG. 8  illustrates one distribution of openings on the stabilizing cylinder according to one illustrative embodiment; 
           [0012]      FIG. 9 . illustrates the hydrophone of  FIG. 3 , as seen looking through the stabilizing jacket. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following discussion is directed to various embodiments of the invention. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0014]    Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not structure or function. 
         [0015]    In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to. The use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
         [0016]    The hydrophone discussed herein may be utilized in various contexts to determine properties in downhole environments. By way of example, it may be included in a tool to receive signals transmitted as pressure pulses from the surface, it may be used in a sensor to monitor seismic signals that create pressure waves in a wellbore, in may be included in a drill string to monitor dynamic pressure waves during drilling. The embodiments may be utilized to determine properties in logging-while-drilling (LWD) environments, wireline, or other logging environments, as well as in marine seismic and sonar environments. Other applications, including non-drilling applications are contemplated. 
         [0017]      FIG. 1  is a schematic diagram of a logging-while-drilling environment  100  according to an illustrative embodiment. LWD may also be referred to as measurement-while-drilling (MWD). A drilling platform  5  is equipped with a derrick  10  that supports a hoist  15 . A rig operator drills an oil or gas well for production or exploration using a string of drill pipes  20 . The hoist  15  suspends a top drive  25  that rotates a drill string  20  as it lowers the drill string  20  through the wellhead  30 . Connected to the lower end of the drill string  20  is a drill bit  35 . The drill bit  35  is rotated and drilling is accomplished by rotating the drill string  20 , by use of a downhole motor near the drill bit  35  or the top drive  25 , or by both methods. 
         [0018]    In one embodiment, recirculation equipment  40  pumps drilling mud or other fluids through a flow line  80  to the derrick  10 . The flow line  80  goes up the derrick  10  and connects  25  to a swivel  83  on the top drive through a stand pipe  81  and a flexible Kelly hose  82  to permit fluid to be pumped through the top drive  25  and into the drill string  20  below. The fluid is delivered down through the drill string  20  at high pressures and volumes to emerge through nozzles or jets in the drill bit  35 . The drilling fluid then travels back up the hole via an annulus formed between the exterior of the drill string  20  and a borehole wall  50 , through a blowout preventer (not illustrated) and a return line  45  into a retention pit  55 , reservoir, or other enclosed receptacle(s) on the surface. On the surface, the drilling fluid may be cleaned and then recirculated by the recirculation equipment  40 . The drilling fluid may be utilized to carry cuttings from the base of the bore to the surface and balance the hydrostatic pressure in the rock formations in the LWD environment  100 . 
         [0019]    A bottom hole assembly  60  (i.e., the lowermost part of drill string  20 ) may include thick walled tubular elements called drill collars, which add weight, stability, and rigidity to aid the drilling process. The thick walls of these drill collars make them useful for housing instrumentation, tools, and LWD sensors. For example, in an embodiment, the bottom hole assembly  60 , or well tool, of  FIG. 1  includes a sensor system  65  and a communications and control module  70 . The sensor system  65  includes one or more hydrophones  72  along with necessary support circuitry. 
         [0020]    From the various bottom hole assembly  60  sensors, the communications and control module  70  (telemetry module) may collect data regarding the formation properties or various drilling parameters, tool configurations and readings, and stores the data, for example in internal  30  memory. In addition, some or all of the data may be transmitted to the surface by wireline communications, wireless communications, magnetic communications, seismic communications, or mud telemetry. 
         [0021]    The communications signals may be received by a surface receiver  84 , converted to an appropriate format, and processed into data by one or more computing or communications devices such as computer  75 . Computer  75  may include a processor that executes software which may be stored on portable information storage media  80 , such as thumb drives, CDs, DVRs or installed computer memory, such as a hard disk, random access memory, magnetic RAM (MRAM) or other forms of non-volatile memory. The computer  75  may also receive user input via an input device  91 , such as a keyboard, mouse pointer and mouse buttons, microphone, or other device to process and decode the received signals. The resulting sensory and telemetry data may be further analyzed and processed by computer  75  to generate a display of useful information on a computer monitor  90  or some other form of a display device or output, such as a mobile device like a hand held smart phone or a tablet PC. For example, a driller may employ the system of the LWD environment  100  to obtain and view information about downhole substances. 
         [0022]      FIG. 2  is a schematic diagram of a logging environment  200  in accordance with an illustrative embodiment. The logging environment  200  may include any number of tools, devices, locations, systems, and equipment that may be utilized to provide the sensor tools, systems, and methods. The logging environment  200  may include a reservoir  201 . The reservoir  201  is a designated area, location, or three-dimensional space that may include natural resources, such as crude oil, natural gas, or other hydrocarbons. The reservoir  201  may include any number of formations, surface conditions, environments, structures, or compositions. In an embodiment, sensors are utilized to determine properties and measurements of the reservoir  201  and a wellbore  203  penetrating the reservoir. For example, one or more hydrophones  72  may be utilized to measure properties in reservoir  201  and a wellbore  203  as described above with reference to  FIG. 1 . Processing or computations utilizing the measured properties may be performed downhole, on-site, off-site, at a movable location, at a headquarters, utilizing fixed computational devices, utilizing wireless devices, or over a data network using remote computers in real-time or offline processing. 
         [0023]    The data and information determined from examination of the wellbore  203  may be utilized to perform measurements, analysis, or actions for exploration or production of the reservoir  201 . The wellbore  203  may be drilled and configured with the reservoir  201  to extract wellbore fluids or gases from the formation. The size, shape, direction, and depth of the wellbore  203  may vary based on the conditions and estimated natural resources available. The wellbore  203  may include any number of support structures or materials, divergent paths, surface equipment, or so forth. 
         [0024]    The instant disclosure describes a pressure sensor, a hydrophone, for use in LWD or MWD systems.  FIG. 3  illustrates one example of a hydrophone  300  that may be used in a downhole tool. The hydrophone  300  is a cylindrical hydrophone and includes a cylindrical base  302 . The base  302  is plated with an external electrode  304  and an internal electrode  308 . In this embodiment, the plated electrodes leave an insulation area  310 , which in this instance is a gap of unplated base material to separate the electrodes  304 ,  308 , which will be explained more fully with reference to  FIGS. 6 and 7 . 
         [0025]    The base  302  may be formed of a piezoelectric material. The piezoelectric material can be chosen from any art recognized piezoelectric materials, natural or man-made. According to one embodiment, the piezoelectric material is chosen from one or more of piezoelectric ceramics, piezoelectric polymers, or crystalline materials, including by not limited to Quartz, PMN-PT crystal, PZN-PT Relaxor-based crystal and the like. 
         [0026]    The electrodes  304 ,  308  may be adhered to the base by any appropriate method of manufacture including but limited to plating, including electroplating and electroless plating: deposition, including vapor deposition, ion plating, sputtering deposition, laser surface alloying and chemical vapor deposition; thermal spray coating, including combustion torch, electric arc and plasma sprays. As used herein, the application of the electrodes  304 ,  308  to the piezoelectric base material  302  will be referred to as metallizing. 
         [0027]    The electrodes  304 ,  308  comprise metallic electrode materials chosen from any art recognized electrode materials. According to one embodiment, the electrode material is chosen from one or more of silver, gold, nickel, cobalt, tin, chromium, vanadium, copper, zinc, and alloys thereof. 
         [0028]      FIG. 4  illustrates a stabilizing jacket  400  that surrounds the hydrophone  300  as seen in  FIG. 3 . The jacket  400  is made from an insulated shell  410  that surrounds the hydrophone  300 . As used herein “insulated shell” refers to the cylinder of insulating material within which the hydrophone rests. As used herein, “stabilizing jacket” refers to the insulating shell  410  in combination with the end caps  402 . The ends of the insulated shell  410  are closed with metal end caps  402 . The hydrophone stabilizing jacket  400  can be creating by securing the end caps  402  to the insulating shell  410 . In one embodiment, the end caps  402  are attached to the insulating cylinder  410  by providing screw threads on the insulating cylinder and screwing the end caps on to secure them. 
         [0029]    The insulating shell  410  can be made of any art recognized insulated material. According to one embodiment, the insulating shell  410  is made of one or more ceramic materials. The material of the insulating shell needs to be non-conductive and strong to prevent damage to the encased hydrophone  300 . 
         [0030]    The end caps  402  may be made of a conductive material, preferably a metal. According to one embodiment, the end cap material is chosen from one or more of stainless steel, brass, kovar, silver, gold, nickel, cobalt, tin, chromium, vanadium, copper, zinc and alloys thereof. 
         [0031]      FIG. 5  is a cutaway view of the jacketed hydrophone  400  at line  5 - 5 . As can be seen in  FIG. 5 , the hydrophone  300  is placed inside the insulating shell  410  and when the end caps  402  are secured to the shell  410 , the circuit is completed and the hydrophone  300  is held stable between the end caps  402 . No internal leads are necessary and external leads (not shown) may be attached to one or more end caps  402 . The stabilizing jacket  400  surrounds the hydrophone  300  and reduces the stress on the piezoelectric cylindrical base  302 . 
         [0032]    As can be seen in  FIGS. 6 and 7 , the metallic end cap  402  contacts the electrodes  304 ,  308  along the electrode material that is plated on the respective ends of the cylindrical base  302 . An insulated region  310  separates the end cap  402  from the other electrode,  308  or  304 , respectively. As used herein, the terms “insulate,” “insulated,” and “insulating,” refer to a material or lack of material that prevents or reduces the passage, transfer or leakage of heat, electricity, or sound from one location to another. 
         [0033]    The insulated area  310  can be a gap in the plating material of electrodes  304  or  308  which creates an insulated region where only the cylindrical base  302  contacts the metal end caps  402  between the electrodes. In an alternative embodiment, not shown in the figures, the gap area  310  may comprise an additional insulating material to prevent contact between the electrodes. The additional insulation material may be chosen from any art recognized insulator. According to one embodiment, the insulation is chosen from polymeric insulator, spray foam, plastic, varnish, paint and the like. 
         [0034]      FIG. 8  illustrates the stabilizing jacket  400  comprised of the insulating shell  410  and the end caps  402 . The insulating shell is provided with openings  415 . The openings  415  reduce the impedance through the stabilizing jacket allowing the fluid pressure to be felt directly by the piezoelectric cylinder  302 . The shape and distribution of the openings are based upon a balance between fluid access to the hydrophone and the strength of the insulating shell so that it doesn&#39;t break during use. According to one embodiment, the openings account for less than 50% of the surface area of the insulating cylinder, for example, less than 40% of the surface area, for example, less than 30% of the surface area. 
         [0035]      FIG. 9  provides a view of the hydrophone  300  as seen through the shell  410 . While the hydrophone is described with respect to a cylindrical hydrophone, other non-cylindrical hydrophones can be constructed in the same manner as described. The hydrophone can be any shape that will allow contact to be established between the electrode material along the edge thereof and an end cap. Alternative shapes include spherical, square, rectangular or any other art recognized shape. 
         [0036]    When one or more jacketed hydrophones  400  is included in the bottom hole sensory system  65  of the bottom hole assembly  60  of  FIG. 1 , the sensor system  65  can measure changes in fluid pressure which can provide information regarding seismic events, drill location, formation mechanical properties, cross-well surveys, sonar, leak detection and flow generated noise detection. 
         [0037]    According to one embodiment, the jacketed hydrophone  400  may be electrically coupled to one or more additional jacketed hydrophones to form an array. 
         [0038]    Other embodiments of the present invention can include alternative variations. These and other variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.