Patent Publication Number: US-2013248208-A1

Title: Downhole Tool Roller Device With Cylindrical Bearing Mechanism

Description:
PRIORITY CLAIM/CROSS REFERENCE TO RELATED APPLICATION(S) 
     This Patent Document claims priority under 35 U.S.C. § 119 to U.S. Provisional App. Ser. No. 61/613,261, entitled “Conveyance Accessories” filed on Mar. 20, 2012, and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses added emphasis has been placed on maximizing each given well&#39;s life and productivity over the course of the well&#39;s life. Thus, well logging, profiling and monitoring of well conditions are playing an ever increasing role in oilfield operations. Similarly, more actively interventional applications are regularly called for such as clean-out applications, opening or closing valves and sliding sleeves or any number of other maneuvers targeting maximized recovery and well life. 
     In addition to regular intervention for sake of monitoring and/or managing well operations, the well itself may also be of fairly sophisticated architecture. For example, in an attempt to maximize recovery from the reservoir and extend the useful life of the well, it may be of a fairly extensive depth and tortuous configuration. This may include overall depths in the tens of thousands of feet range. Once more, such wells may include extended horizontal or deviated sections of several thousand feet. As a result, interventions through such wells are becoming of ever increasing difficulty as noted below. 
     Where interventional applications are sought in wells of particularly challenging architecture, wireline cable, coiled tubing, drill pipe or other semi-rigid conveyance line may be utilized to deliver an interventional tool to a target location in the well. In order to help the conveyance line navigate the well downhole, conveyance aids are available to help the conveyance line and toolstring traverse the challenging architecture of the well. These may include active conveyance aids such as tractors or vibration tools, generally located near the end of conveyance line near the toolstring. Thus, the conveyance line may be actively pulled further downhole or vibrated in such a manner as to help extend the overall reach of the conveyance line. 
     In light of the potential drawbacks to conveyance aids noted above, a toolstring may be outfitted with more straight-forward, passive features to help in traversing a well of sophisticated architecture. For example, the toolstirng or a housing of a given tool may be equipped with passive rollers. That is, conventional, appropriate sized wheel-like features may be placed at the outer surface of the toolstring. So, for example, where a 100 foot toolstring is rounding a transition bend of a few hundred feet or so into a deviated well section, the rollers may passively contact the well wall as the bend is rounded. This may prevent mechanical or even differential sticking in such situations. Once more, preventing such sticking in this manner may be the extent of the conveyance aid that is required in order to allow the tool to reach the target location downhole. That is, the challenge in delivering the toolstring to the downhole target location at times may be less about overall load capacity throughout the well, for example, as may be met by a heavy duty tractor, and more about being able to passively round a bend at a given location. Certainly where this is the case, passive roller-aided conveyance may be preferable to other aiding techniques. 
     Unfortunately, while passive roller-aided conveyance may be suitable for helping the toolstring to reach a downhole target location in theory, rollers face their own inherent limitations. For example, passive, and even active rollers, generally include bearing ring assemblies similar to those found in wheels on conventional pair of roller skates. Setting aside manufacturability disadvantages, these types of assemblies are also relatively short-lived upon exposure to downhole environments. That is, it is understandable that a host of spherical bearings exposed to debris, sand or downhole fluids tends to lock-up and/or corrode fairly quickly. Indeed, after every couple of deployments into the well, it is likely that replacement of all of the bearing assemblies for the toolstring is called for. Yet, in spite of these added maintenance and materials costs, this is often the operators&#39; most practical option for aiding in the conveyance of the toolstring. 
     SUMMARY 
     A downhole toolstring is provided that includes a tool housing equipped with a conveyance aid. The conveyance aid includes at least two roller devices for contacting a wall of the well during the conveyance therethrough. Further, the roller devices themselves each include a cylindrical bearing based mechanism to allow rolling thereof during the contacting of the wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overview of an oilfield with a well that accommodates a toolstring employing embodiments of roller devices as a conveyance aid. 
         FIG. 2A  is an enlarged side view of the toolstring of  FIG. 1  and highlighting the roller devices thereof. 
         FIG. 2B  is a front cross sectional view of the toolstring taken from line  2 - 2  of  FIG. 2A  revealing the internal working of a given roller device. 
         FIG. 3A  is a side view of the underside of a roller device of  FIGS. 1 ,  2 A and  2 B highlighting an embodiment of a journal bearing therein. 
         FIG. 3B  is a side view of an alternate embodiment of the journal bearing of  FIG. 3A . 
         FIG. 4A  is a side view of the toolstring of  FIG. 1  employing an alternate embodiment of roller devices as a conveyance aid. 
         FIG. 4B  is a front cross sectional view of the toolstring taken from line  4 - 4  of  FIG. 4A  revealing the internal working of a given roller device. 
         FIG. 5  is a flow-chart summarizing an embodiment of employing roller devices of a toolstring as an aid to conveyance thereof through a well. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described with reference to certain downhole applications through deviated well sections that may benefit from roller devices as an aid to conveyance of a toolstring through the well. In particular, coiled tubing line is utilized to deliver a logging and treatment assembly of considerable length to a downhole location at a depth beyond a non-vertical section of the well. Though, wireline, drill pipe and other conveyance line types may be utilized. Regardless, conveyance of the assembly may be aided by passive rollers thereof as it enters a deviated or tortuous portion of the non-vertical well section. Of course, a host of other downhole assemblies and accessories, conveyed by coiled tubing or otherwise, may be outfitted with conveyance aids as detailed herein. These may include more interventional devices and applications such as for perforating or those of a more passive nature such as for more limited conventional logging. Regardless, so long as the conveyance aid of the assembly includes roller devices with cylindrical bearing based mechanisms therein, enhanced conveyance thereof through the well may be achieved. 
     Referring now to  FIG. 1 , an overview of an oilfield  105  is shown accommodating a well  180 . The well  180  in turn accommodates a toolstring  101  that employs embodiments of roller devices  100  as a conveyance aid. That is, as is increasingly the case, the well  180  may be of somewhat sophisticated and non-vertical architecture, traversing several thousand feet and multiple formation layers  190 ,  195 . 
     Thus, in the depicted example, where the toolstring  101  is conveyed to sufficient depths, it must traverse a bend  197  in the well  180 . Given that the toolstring  101  may be a fairly rigid structure spanning 50-150 feet or more, roller device or devices  100  such as those depicted may serve as a passive aid in allowing the toolstirng  101  to round the bend  197 . That is, as the rigid toolstring  101  is advanced by conveyance line such as, but not limited to, coiled tubing  110  into the bend  197 , the well wall  185  may present a tight fit or squeeze to the elongated toolstring  101 . However, the roller devices  100  may passively and responsively roll against the well wall  185  at this time to further aid in conveyance of the toolstring  101  beyond the bend  197 . 
     While rounding the bend  197  with passive assistance of roller devices  100  appears fairly straight forward, particular challenges may be presented to the effectiveness of the devices  100  due to the nature of the well environment. For example, as detailed further below, the toolstring  101  of the example embodiment shown includes logging devices  160  for obtaining a variety of different types of well data such as the nature of the surrounding formation  195  or well fluids and other constituents. Indeed, as shown in  FIG. 1 , a significant amount of debris  199 , sand or other particulate may be found in the well  180 . These types of physical corrosives are not limited to isolated locations but are disbursed throughout the well  180  and fluids thereof. As a result, roller devices  100  as shown are fully exposed to such corrosives whenever positioned downhole. However, as detailed further below, the roller devices  100  are equipped with a unique cylindrical bearing based mechanism so as to minimize internal exposure and wear from the downhole environment, thereby extending life and effectiveness as a conveyance aid. 
     Continuing now with reference to  FIG. 2A , with added reference to  FIG. 1 , an enlarged side view of the toolstring  101  is shown which highlights the noted roller devices  100 . In this depiction it is apparent that the roller devices are of a profile that is slightly larger than the diameter (d) of the toolstring  101 . Thus, as noted above, the roller devices  100  may passively contact the well wall  185  as needed (e.g. upon rounding the bend  197 ). As also indicated above, the toolstring  101  is conveyed via coiled tubing  110 . In the embodiment shown, such operations may involve surface equipment  125  that includes use of a mobile coiled tubing truck  135  with reel  144  and control unit  142  for directing operations. These operations may include the conveyance of the coiled tubing  110  and toolstring  101  and/or directing of downhole applications as described further below. As will be appreciated by those skilled in the art, the conveyance line  110  may comprise wireline cable, slickline, coiled tubing, drill pipe, or any suitable conveyance line. 
     Continuing with reference to  FIG. 1 , conveyance includes routing the coiled tubing  110  and toolstring  101  through a gooseneck injector  155  at a rig  145  over the well  180 . Thus, the entire assembly may be forcibly advanced through a blowout preventer  165  and into the vertical portion of the well  180 . With added reference to  FIG. 2A , the toolstring  101  may be advanced within the well  180  as described above for sake of logging and/or other downhole applications. 
     In the embodiment of  FIG. 2A , the example toolstring  101  includes traditional logging as well as more interventional tool segments. For example, imaging  270 , gas monitoring  230  and density acquisition  260  tools may constitute part of the logging device  160 . However, a treatment tool  120  for delivering downhole fluids is also provided. In fact, the toolstring  101  is even outfitted with a sampling implement  265  for direct interfacing with the well wall  185  as described further below. That is, in the embodiment shown, the toolstring is not configured for use in an exclusively cased well or other more isolated environment. Rather, exposure by the toolstring  101  and its roller devices  100  to a host of downhole fluids, debris  199 , introduced treatment fluids, and even formation disturbance is to be expected. 
     In light of the vast amount of particle and other expected downhole exposures, the roller devices  100  are configured with cylindrical bearing based mechanisms as noted above. More specifically, with reference to  FIG. 2B , a front cross sectional view of the toolstring  101  is shown taken from line  2 - 2  of  FIG. 2A . In this manner, the internal workings of a given roller device  100  are revealed. That is, apart from the internal density acquisition tool  261  and housing  260  at this portion of the logging device  160 , two roller devices  100  are shown along with internals thereof. 
     The internals of the roller devices  100  reveal cylindrical bearing based mechanisms in the form of journal bearings  200 . That is, the indicated housing  260  is equipped with mandrels  215  that extend therefrom such that circumferential, substantially monolithic journal bearings  200  may be disposed thereabout. In this manner, a smooth substantially uninterrupted bearing interface is provided between the body of each roller device  100  and each mandrel  215 . As a result, exposure and opportunity for particulate, sand and other debris  199  of the well  180 , to interact with such bearing based mechanisms  200  is kept at a minimum. For example, the amount of exposed surface to volume area is minimized with use of a smooth monolithic piece as opposed to conventional ball bearings. Furthermore, the ability is now afforded to configure the underside of a body of the roller device  100  to substantially morphologically match the journal bearing  200 . Thus, the bearing  200  may be substantially isolated from the indicated exposures of concern. 
     Continuing with reference to  FIG. 2B , the journal bearing  200  may be of a non-corrosive, durable metal so as to even further extend the life thereof. Additionally, the single-piece nature of the bearing  200  may afford ease of assembly and maintenance, even in circumstances where replacement is required. That is, hub screws  240  may be loosened for removal of a hub  210 , and the single-piece bearing  200  dropped out of the roller device  100 . 
     In the embodiment shown, two rollers  100  in an adjacent fashion. Thus, when a sampling implement  265  as shown in  FIG. 2A  is extended to interface with the well wall  185  (through zone  266 ), it may achieve a stable interface along a perpendicular axis  201 . That is, the roller devices  100  may attain a foothold at one side of the well wall  185  and allow the implement  265  to achieve a largely sealed engagement with the opposite side of the well wall  185  for formation sampling therefrom. From a dimensional standpoint this may be achieved so long as the diameter of the well  180  sufficiently exceeds the width of the toolstring  101 , from one  100  roller device to another roller device  100 . 
     In the embodiment of  FIG. 2B , the cylindrical bearing based mechanism is a journal bearing  200  as described. However, other forms of cylindrical bearing based mechanisms may alternatively be employed. For example, in one embodiment, cylindrical roller bearings may be utilized which provide a degree of both radial and axial slip. Additionally, as described further below with regard to  FIGS. 4A and 4B , alternate embodiments of roller devices  400 ,  401  and journal bearing configurations may also be utilized. 
     Referring now to  FIG. 3A  a side view of the underside of a roller device  100  such as that of  FIGS. 1 ,  2 A and  2 B is depicted. In this view, an embodiment of the journal bearing  200  is highlighted therein. The bearing  200  is of a circumferentially continuous and monolithic form as described above. Accordingly, it includes a continuous interior surface  315  for direct interface with a mandrel  215  as shown in  FIG. 2B . Similarly, an exterior surface  301  is provided for interfacing the body of the roller device  100 . 
     With added reference to  FIG. 2B , the roller device  100  includes an exterior structure  350  and face  351  that is exposed to the well  180  for interfacing the well wall  185  as described above. However, it is also configured with a recess  375  having a portion for receiving the bearing  200 . In the embodiment shown, this recess  375  is stepped down such that the bearing  200  does not occupy the entirety of the recess  375 . Of course, in other embodiments, alternative recess architecture may be utilized. 
     Referring now to  FIG. 3B , a side view of an alternate embodiment of the journal bearing  200  of  FIG. 3A  is shown. In the embodiment of  FIG. 3B , the journal bearing  200  remains of continuous circumferential form. However, the bearing is split into separate monolithic pieces  320 ,  340  which are utilized together. More specifically, this results in the noted interior surface  315  and exterior surface  301  being associated with separate pieces  320 ,  340  of the bearing  200 . As a result, forces that are exerted on the interior surface  315  by the mandrel  215  of  FIG. 2B  are not necessarily imparted directly across the entirety of the bearing  200  (e.g. all the way to the other surface  301 ). Similarly, forces from interface with the well wall  185  which translate over to the exterior surface  301  are not automatically imparted directly across the bearing to the opposite surface  315  (see  FIG. 2B ). 
     The intentional physical disconnect between the journal pieces  320 ,  340  as described above results in an interface  330  that allows for intentional slippage. That is, the reason forces from one surface  301  or another  315  do not necessarily fully translate across the entirety of the bearing  200  is due to the allowance of slippage at the noted interface  330 . Once more, this interface  330  is located at an isolated interior of the bearing  200  such that its presence does not result in a new location of exposure in terms of well debris and other corrosives of the environment. More specifically, unlike use of multi-piece spherical bearings for example, a multi-piece bearing  200  is provided in  FIG. 3B  that does not result in added surface exposure to the well environment that might compromise life of the bearing  200 . 
     Referring now to  FIGS. 4A and 4B , alternate embodiments of roller devices  400 ,  401  are shown which may be of a more elongated  400  or dual-sided  401  configurations. These embodiments highlight the fact that a variety of different configurations of roller devices may be employed which utilize underlying embodiments of cylindrical bearing based mechanisms, whether of a journal bearing type or otherwise. 
     Specifically, with reference to  FIG. 4A , a side view of the toolstring  101  of  FIG. 2A  is shown, again with focus on the vicinity of the logging device  160  near a sampling tool  465 . However, in contrast to  FIG. 2A , the embodiment of  FIG. 4A  reveals roller devices  400  which are of a more interior and elongated configuration with respect to the tool housing  460 . That is, as opposed to being more fully exterior the housing  460 , the roller devices  400  may be recessed to a degree into the housing  460  (see  FIG. 4B ). 
     By the same token, with reference to  FIG. 4B , a roller device  401  may instead be extended further away from the housing  460  (e.g. and of a dual-sided configuration). Specifically,  FIG. 4B  is a front cross-sectional view of the same toolstring  101  of  FIG. 4A , taken from line  4 - 4  thereof. In this view, the internal workings of roller devices  400 ,  401  are shown. Wear piece type journal bearings  410  of a more elongated variety may serve as the cylindrical bearing based mechanisms as depicted in the partially sectional view of a dual-sided roller device  401 . 
     Additionally, with reference to these same roller devices  401 , they may be positioned at opposite sides of the housing  460  and of sufficient distance (d′) relative a diameter (D) of the well  180  so as to provide a degree of centralization. That is, rather than attain a footing at a side of the well  180  opposite the perpendicular axis  411  and zone  466  for the sampling tool  465 , centralization above the ‘floor’ of the well wall  485  may be attained. So, for example, at the time of sampling, it is less likely that the elongated interior roller devices  400  would be in contact with debris at the well wall  185 , particularly during formation sampling. Of course, a variety of additional tool configurations and roller device types may also be developed which take advantage of underlying embodiments of cylindrical bearing based mechanisms. 
     Referring now to  FIG. 5 , a flow-chart summarizing an embodiment of employing roller devices of a toolstring as an aid to conveyance is shown. Specifically, the toolstring is deployed into the well as indicated at  510 . The roller device may provide conveyance assistance as indicated at  530 . Further, in recognition of debris and other wear-inducing factors of the well environment, a cylindrical bearing based mechanism may be utilized in conjunction with the device as noted at  550 . Thus, as indicated at  570  and  590 , an application may be performed with the toolstring and it may be removed from the well in a reliable and repeatable manner without undue concern over roller device ineffectiveness, failure or excessive wear. 
     Embodiments described hereinabove include roller-aided conveyance devices and techniques that may or may not be passive in nature. However, these roller devices avoid the use of ring assemblies utilizing a plurality of spherical bearings. Thus, bearing life is not significantly compromised in light of regular exposure to the downhole environment. Rather, roller devices and conveyance may be aided through use of an underlying cylindrical bearing based mechanism, that may even be of enhanced manufacturability and comparatively low labor replacement cost. In addition to aiding conveyance of the toolstring  101 , those skilled in the art will appreciate that the roller device or devices  100 ,  400 , and/or  401  may also prevent or mitigate sticking of the toolstring  101  while the toolstring  101  is stationary, such as when the sampling implement  265  or sampling tool  465  is directly interfacing with the well wall  185  for extended periods of time, as the roller device or devices  100 ,  400 , and/or  401  may provide a mechanism for passively and/or responsively rolling against a well wall  185  and/or a mudcake formed thereon. 
     The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Regardless, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.