Abstract:
A pulser providing pressure based accoustic telemetry in a fluid column includes a formed turbine and valve wheel moveable as one unit, an aft turbine configured to drive the valve wheel and a brake to inhibit movement of the aft turbine. During periods when the aft turbine is slowed relative to the formed turbine and valve wheel, the aft turbine blocks misalign with blades of the valve wheel inhibiting fluid flow therepast. A pressure buildup is caused hereby until the brake is released allowing the aft turbine blades to realign with the valve wheel by resuming speed rotation thereby terminating pressure buildup.

Description:
BACKGROUND 
     The desire for more information is pervasive in virtually every discipline. In the case of transport of fluid from a distant source in a fluid column, information about any number of things occurring distantly or the ability to communicate through the fluid column distant locations is desirable. While this is particularly true in the oil and gas industry it is generally applicable in any such fluid column systems. 
     SUMMARY 
     A pulser comprises a first turbine and valve wheel and a second turbine rotationally moveable selectively with or relative thereto to create flow restriction and constant pressure increase for a selected period of time. A method for pulsing and communication in a fluid column comprising spinning at two turbine system in an aligned condition; selectively misaligning said system for a selected period of time and allowing said system to realign. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a pulser in a flow unrestricted (aligned) configuration; 
     FIG. 2 is a schematic perspective view of the pulser in a flow restricted (misaligned) configuration; 
     FIGS. 3 a - 3   d  are an exploded view of the pulser; 
     FIGS. 4 a - 4   b  are a view of the components of the pulser in an assembled condition; and 
     FIG. 5 is an alternate embodiment of the pulser. 
    
    
     DETAILED DESCRIPTION 
     The pulser operates to cause a pressure buildup within the fluid column for a discrete period of time through selective misalignment of a valve wheel with another valve wheel or a turbine. A buildup of pressure is caused by the misalignment of the valve. The pressure buildup is propagated through the fluid column from its point of origin at the valve and is detectable at a distant location. The discrete pressure buildup is known in the vernacular as a “pulse”. A series of pulses with timed intervals are readable as a message. 
     With reference to FIGS. 1 and 2, the pulser in the valve open or aligned position and in the valve closed or misaligned position, respectively, are illustrated. One of skill in the art will appreciate that in the FIG. 2 (misaligned) position, a pressure buildup is created. The misalignment of the valve is the beginning of a pulse which ends upon the valve being realigned. 
     Referring to FIGS. 3 a - 3   d , the components of the pulser are illustrated in exploded form and hereunder described. For purposes of discussion it is assumed that fluid will flow from the left side of each of the drawings to the right side of each of the drawings. It will be understood through that the flow could be reversed. 
     Referring to FIG. 3 a , components for operability of forward turbine  12  are illustrated. Forward support  14  is configured to be receivable in a tubular member (not shown) such that support may be provided to a forward shaft  16  upon which forward turbine  12  is supported. Forward shaft  16  includes a bushing nose  18  sized and configured to nest with a bushing  20  which may be of a bronze material or other suitable supportive yet lubricious material. A double shoulder  22  defines a thrust bearing land  24  to be received in thrust bearing  26 . Bearing area  28  is received in bearing  30  which may be a roller bearing or other suitable bearing for the intended environment. It is noted that this bearing may be mud cooled when the device is utilized in a hydrocarbon well or may be oil bathed. If oil bathed then a seal  32  is also desirable to maintain a delineation between the bathing oil and the surrounding fluid. It will be appreciated from the figure, by one of ordinary skill in the art, that support  14  provides a stepped recess  34  wherein bushing  20 , thrust bearing  26 , bearing  30  and seal  32  are received to provide support for forward shaft  16 . 
     Upon forward shaft  16  is mounted forward turbine  12 . Turbine  12  is mounted thereon by means of a splined connection or other similar positive connection limiting relative rotational movement therebetween. 
     Still referring to FIG. 3 a , but now bridging to FIG. 3 b , forward shaft  16  includes an ID profile  36  intended to receive a bushing  38 , thrust washer  40 , bearing  42  and seal  44  (optional) in a manner similar to that of front support  14 . The support set  38 ,  40 ,  42  and  44  receive and support inner shaft  46  by receiving that shaft in a manner similar to the receipt by front support  14  of shaft  16  in FIG. 3 a.    
     Inner shaft  46  supports aft turbine  48  thereon in a rotationally inhibited arrangement such as a splined connection or other similarly acting connection. At one end of aft turbine  48  (left in the drawing) is an aft valve wheel  50  which has an end view similar to that of the aft turbine such that alignment of the valve wheel  50  with aft turbine  48  can be accomplished. In one embodiment both the aft turbine  48  and aft valve wheel  50  possess four blades each, each blade occupying 45° of arc and defining a space of 45° of arc therebetween. Aft valve wheel may be advantageously constructed of a hard material to reduce flow cutting thereof and to additionally protect aft turbine  48 . Aft valve wheel  50  is rotationally affixed to aft turbine  48  and is maintained in proximity therewith. It will be appreciated that aft valve wheel  50  may be omitted with aft turbine  48  assuming the function of wheel  50 . In such event, consideration of resistance to flow cutting of turbine  48  should be given and suitable material resistant thereto employed. 
     Still referring to FIG. 3 b , forward valve wheel  52  is positioned proximate and coaxially with aft valve wheel  50  (or aft turbine  48  in the event wheel  50  is omitted). Moreover, forward valve wheel  52  is configured to rotate with forward shaft  16  and thereby forward turbine  12 . Forward valve wheel  52  is configured to have blades substantially equivalent in number, size and configuration to aft valve wheel  50  to facilitate alignment and thereby low flow restriction when desired. It is further desirable to provide forward stop  54  and aft stop  56  whose functions will be discussed hereunder. 
     Returning to inner shaft  46 , the not-hereinbefore-discussed end (right end in drawing) of shaft  46  is provided with a profile sufficient to nest with a support set including retainer  58 , seal  60 , bearing  62 , thrust bearing  64  and bushing  66  which are substantially similar to the support sets hereinbefore discussed with the exception of retainer  58  which ensures that the other members of this support set are reliably retained in stepped recess  68  of brake housing  70  (see FIG. 3 c ) wherein the second discussed end of inner shaft  46  is received and supported. 
     Referring to FIG. 3 c , brake housing  70  is configured to be receivable in a tubular (not shown), which may be a hydrocarbon well tool, in such manner that housing  70  is non-rotatable with respect to said tubular. Within housing  70  is a brake mechanism  72  (FIG. 3 d ) which may be an electric brake. The brake may be a brushless dc motor operating as a generator with one or more relay circuits (not shown) actuatable to short the phases of the motor on command. It will be appreciated that the brake mechanism need merely have the capability to reduce the attained rotational speed of the aft turbine  48 , due to fluid flow therepast, to below the speed of the forward turbine  12  to effect relative rotation of forward valve wheel  52  to aft valve wheel  50  and thereby at least partial restriction of fluid flow therepast. In one embodiment a brushless dc motor operating in generator mode is selected to achieve the advantage that no current is required to operate the brake. Rather, merely a 5 volt signal need be communicated to the brake to obtain the desired result. As illustrated, inner shaft  46  is coupled to brake mechanism  72  by shaft coupling  74 . An end cap  76  may be provided to secure and protect brake mechanism  72 . 
     Each of the components discussed relative to the exploded view of FIGS. 3 a - 3   d  are also illustrated and identically numbered in FIGS. 4 a  and  4   b  to further enhance understanding of the illustrated embodiment of the pulser. 
     The forward turbine  12  and aft turbine  48  are configured with specific pitches relative to one another that are calculated to produce the desired effect of the aft turbine  48  driving the forward turbine  12  under valve open (aligned) conditions. This is achieved in one embodiment by configuring the aft turbine  48  with a greater pitch than that of forward turbine  12 . The greater the pitch of a turbine, the faster that turbine will spin incident to fluid flowing thereover. Since the aft turbine  48  in this embodiment is of greater pitch than the forward turbine  12 , the aft turbine will spin faster than does the forward turbine  12  for a given flow through the system. Thereby the aft turbine necessarily drives the forward turbine  12 . Since, as is visible in FIG. 4 a , stops  54  and  56  overlap in the assembled configuration of the device the more rapidly spinning aft turbine  48  will necessarily provide a driving force to forward valve wheel  52 , forward shaft  16  and forward turbine  12 , which as noted above are rotationally affixed to one another. Placement of stops  54  and  56  is such that when the forward components identified are driven by aft turbine  48 , all blades of the valve wheels are aligned and the least restriction to fluid flow is presented. 
     When a pulse is desired, brake mechanism  72  is engaged causing a torque to be loaded onto inner shaft  46  thereby slowing aft turbine  48  (and aft valve wheel  50 , which is affixed thereto rotationally, if included). It is desirable that the torque loading available be sufficient in view of the inertial mass of inner shaft  46 , aft turbine  48 , valve wheel  50  and drag forces between valve wheel  50  and valve wheel  52 , to rapidly slow aft turbine  48 . It is helpful to reduce the mass of these components as is practical to reduce necessary brake torque. It is desirable to slow aft turbine  48  rapidly to a speed below that of forward turbine  12  so that forward valve wheel  52  will rapidly misalign with aft valve wheel  50  which begins a pulse due to restriction in the flow path. In one embodiment, the degree of misalignment obtained is limited to about 22.5°. It has been found that this degree of misalignment in this embodiment is sufficient to create pressure rise in the flowing fluid while still allowing enough fluid to pass through the valve wheel aft turbine misalignment to cause the aft turbine to spool up again upon release of the brake mechanism. It will be understood however that any degree of misalignment provides some degree of pressure rise. Depending upon sensitivity of receiving equipment for a pulse the misalignment may be lesser or greater as desired. 
     Since the aft turbine spins more quickly than the forward turbine  12 , the tendency is for aft turbine  48  to drive aft valve wheel  50  into alignment with the forward valve wheel  52  marking the end of that discrete pulse. The width of the pulse is controllable by the time during which the brake mechanism is activated. It should be noted that to enhance the operation of the illustrated embodiment, the valve wheels are advantageously made thin to reduce hydraulic opening forces which are an impediment to rapid misalignment of the valve wheels. 
     In an alternate embodiment, schematically illustrated in FIG. 5, the aft turbine  48 , brake housing  70  and brake mechanism  72  of FIGS. 3 and 4 are collapsed to reduce components and length of the assembled tool. In this embodiment aft turbine  80  is itself a rotor. A housing  82  is disposed outwardly of turbine  80  and includes coils  84 . Turbine  80  includes magnets  86 . These components, it will be understood comprise a generator when in a shorted phase condition. The turbine may be slowed by activation of the coils with results similar to the foregoing embodiment. 
     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.