Abstract:
A bottom hole assembly (BHA) which is transported via a wireline through downhole and lateral wellbores and thence through a wellbore window aperture, the BHA carrying with it a blocking tool which is adapted to engage the edge of a lateral wellbore window and prevent the wireline from contacting and abrading against that edge of the window, the blocking tool being detachable from the BHA which proceeds axially distally through the wellbore window while the wireline slides through the blocking tool. Upon withdrawal of the BHA the blocking tool is reattached thereto and is removed with it.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 61/784,784 filed on 14 Mar. 2013, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention is in the field of oil and gas drilling apparatus and procedures for well logging at different elevations along the depth of the wellbore in order to determine and monitor the characteristics of the strata that are being encountered and traversed. 
       BACKGROUND AND PRIOR ART 
       [0003]    Basic downhole wellbore systems often include lateral wellbores at different depths. For investigation, monitoring or other well logging operations it is known to employ a logging tool or bottom hole assembly (BHA) which has the capacity to measure and/or monitor any, all or any combination of resistivity, conductivity, formation pressure, electrical, acoustic, radioactive, electromagnetic, nuclear magnetic resonance and other properties of the strata such as rock, sand, mud, oil, gas and shale and their contained fluids. 
         [0004]    U.S. Pat. No. 6,131,659 entitled “Downhole Well Corrosion Monitoring Apparatus and Method”, incorporated herein by reference, discloses an array of transducers and associated microprocessors insertable into a wellbore. 
         [0005]    U.S. Pat. No. 6,725,925 entitled “Downhole Cathodic Protection Cable System, incorporated herein by reference, discloses some of the basic concepts in downhole drilling operation. 
         [0006]    A further disclosure entitled “Technical Paper: High-performance Wellbore Departure and Drilling System for Accessing New Target”, incorporated herein by reference (available at the website http://slb.com/resources/technical papers/drilling/138001.aspx), discloses application of wellbore departure in downhole drilling systems. The paper asserts that conventional wellbore departure and drilling systems generally require the operator to make multiple downhole trips to achieve a specific objective, including a window milling bottom hole assembly (BHA) that is run in hole to create an exit path in the existing casing and drill sufficient rathole for the next drilling assembly, and that in the subsequent trip, a directional drilling BHA is run to extend the rathole and drill laterally to the target. The paper discusses the possibility of single trip operation with good downhole dynamics control and overall BHA drillability. The paper surmises that a re-entry system should be able to mill a window in the existing casing sufficiently large enough for obstruction free entry of the BHA and new liners, and that once the BHA has exited the casing, the new system would be required to drill a full gauge lateral wellbore to the target with good directional control and minimal vibration. Technological/operational issues analyzed include dynamic simulation of the BHA to study the nature and magnitude of the vibrations, controlling vibrations and feed rate to reduce premature cutter damage during window milling operations, utilizing the latest force balance software for selection of shapes, sizes, number and location of cutters for maximizing on-bottom time, exploring hybrid cutting structures on bit/mill to maintain gauge. The discussed system, over several phases, involved milling of a window in the existing casing and drilling a lateral to various depths. The first phase was run on a conventional rotary BHA in soft and medium formations, the second phase included testing on a positive displacement motor with bent sub or bent housing, and the third phase included a push-the-bit type rotary steerable system. The paper concludes that a functional single-trip system for milling a window and drilling a lateral borehole is commercially feasible, and that a versatile system will contribute substantially to the technology required to efficiently and economically mill a window in the existing casing and then drill an extended length lateral wellbore to the target formation without tripping for equipment/bit change out. 
         [0007]    Wirelines and slicklines are tools inserted in to a well for both workover and logging efforts, and are similar devices. A slickline is used to place and recover wellbore equipment, such as plugs, gauges and valves. These are single-strand non-electric cables lowered into oil and gas wells from the surface. Slicklines can also be used for adjustment of downhole valves and sleeves, and to repair tubing within the wellbore. A wireline is an electrical cable used to lower tools into, transmit data about the conditions of the well bore, and conduct logging. Wirelines can be single strands or multi-strands. A wireline can be used for well intervention and formation evaluation operations. Wireline logs can be used to measure formation properties in a well through electrical lines. These measurements can be used to help geologists, drillers and engineers make real-time decisions about drilling operations, and can include resistivity, conductivity and formation pressure, as well as sonic properties and wellbore dimensions. A logging tool, known in the industry as a sonde, is located at the bottom of the wireline. The tool is lowered by the wireline to a certain depth, and measurements are taken continuously on the ascent. When producing wells require remedial work to sustain, restore or enhance production, this is referred to in the industry as workover operations. A well-servicing unit is used to winch items in and out of the wellbore. The line used to raise and lower equipment can be braided steel wireline or a single strand slickline. Workover operations can include well clean-up, setting plugs, production logging and perforation through explosives. 
         [0008]    Wirelines can also be used for core drilling operations, in which the objective is to retrieve a core sample. In core drilling, a core drill string includes a series of connected long hollow tubes, known as a rod string, with a barrel at the end connected to a cutting bit at the bottom of the hole. To remove the core, the entire core barrel including each connected tube is removed. With wireline core drilling, the barrel can be removed without removing the rod string. An overshot is lowered on the end of a wireline, and the overshot attaches to the back of the inner tube disengages itself from the barrel as the core barrel inner tube and the wireline is pulled back. 
         [0009]    To access a lateral wellbore such a BHA is attached to a wireline cable and transported downward in the main wellbore, then turned in a lateral direction and into the lateral wellbore, and then directed to exit the lateral wellbore through a window or aperture milled in a wall thereof and then into a strata of interest. 
         [0010]    Unfortunately the milled window in a lateral casing wall often has sharp edges that may abrade or break a wireline cable that traverses against such edges. Tension on such cable as well as repeating the operation for multiple runs of a BHA are two factors that increase abrasive friction or other damage to a wireline cable. 
         [0011]    Use of wireline cable and slicklines to transport the logging tool has been preferred for various reasons including ease, accuracy and economy; however, the risk of abrading or damaging the cable at the lateral window has been a major problem causing time delays, expense and even shutdown of the entire apparatus when a cable must be repaired or replaced. 
       OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
       [0012]    A first object of the present invention is to provide apparatus that allows safe and efficient use of wireline cable to transport a BHA through a milled window in a lateral wellbore and provides similarly for safe and efficient use of slicklines. 
         [0013]    Another object is to provide a tool attached to a BHA which engages the wellbore window and prevents the wireline from contacting the edge of the window as the BHA travels through said window and moves axially distally beyond said window. 
         [0014]    A further object is for the tool as described above to be attached to and carried by the BHA as it passes through downhole and lateral wellbores approaching said lateral wellbore window. In a preferred embodiment of the present invention the tool will have a diameter no greater than the BHA to which it is removably attached. Alternatively, this tool may be standalone from the BHA and still function with a wellbore window to improve safe and efficient use of wirelines and slicklines. 
         [0015]    A still further object is for said tool as described above to separate from said BHA when said BHA enters said window, and as the tool engages the window to maintain said wireline from contacting the edge of the window. 
         [0016]    A further object is for said tool as defined above to be reconnected to said BHA when the BHA is withdrawn back out through said window and thence outward of said lateral and downhole wellbores. 
         [0017]    An additional object is for said tool is described above to engage said edge of the window by having a part of said tool move to positions radially outward of the central axis of the BHA to thus have a diameter greater than the opening of the window. 
         [0018]    Another object is for said tool as described above to comprise a pair of pivotal arms which are spring biased or otherwise directed to their open position where they span a space greater than the opening of said window. Optionally, the tool could have two pairs of arms or some number more than two arms. 
         [0019]    It is thus another object to provide a tool which can protect the wireline from damage by a sharp edge of the wellbore window, which tool is transported to the window by the BHA itself and is removed by the BHA when it is retracted. 
         [0020]    Various exemplary embodiments of the present invention are described below: 
         [0000]    1. A bottom hole assembly (BHA) connectable to a wireline cable, the BHA having outer diameter D1 adapted to pass through a wellbore inner pipe of predetermined inner diameter Dp, the BHA comprising:
       a. a cylindrical housing having a proximal end connectable to said wireline and a distal end, and a maximum outer diameter D1 less Dp, and   b. a blocking tool comprising:
           i. a body part having a central axis and a distal end releasably coupled to said proximal end of said housing,   ii. a maximum outer diameter D2 less than Dp,   iii. a central bore through which said wireline cable is axially slidable,   iv. a blocking part carried by said body part and movable from a closed position where said blocking part extends radially outward of said central axis a distance less than Dp, and has an open position where it extends radially outward a distance greater than Dp, and   v. a drive mechanism adapted to move said blocking part from said closed position to said open position, and further adapted to cause separation of said blocking tool from said cylindrical body while allowing said cable to remain slidable through said blocking tool when said cylindrical housing moves axially distally away from said blocking tool.
 
2. A bottom hole assembly (BHA) connectable to a wireline cable, and operable to pass through a downhole wellbore contiguous with a lateral wellbore both having diameter Dp (or the lateral wellbore may have a diameter less than the diameter of the mainbore), the lateral wellbore having a lateral window aperture of maximum diameter Dw, the BHA comprising:
   
           a. a cylindrical housing having a proximal end connectable to a wireline and a distal end, and a maximum outer diameter D1 less than Dp, and   b. a blocking tool comprising:
           i. a body part having a central axis and a distal end releasably coupled to said proximal end of said housing,   ii. a maximum outer diameter D2 less than Dp,   iii. a central bore through which said wireline cable is axially slidable,   iv. a blocking part carried by said body part and movable from a closed position where said blocking part extends radially outward of said central axis a distance less than Dp, and has an open position where it extends radially outward a distance greater than Dw, and   v. a drive mechanism adapted to move said blocking part from said closed position to said open position, and further adapted to cause separation of said blocking tool from said cylindrical body while allowing said cable to remain slidable through said blocking tool when said cylindrical housing moves axially distally away from said blocking tool.
 
3. A method operable with a BHA as defined in example 2 above that is entering a lateral wellbore window, comprising the steps to prevent said wireline from engaging any edge of said lateral wellbore window:
   
           a. directing said drive mechanism of said blocking tool to move said blocking part to said open position to have diameter greater than said window and to engage the edge of said window and thereby block entry of said blocking tool through said window, and   b. separating said blocking tool from said BHA while allowing said cable to remain slidable through said blocking tool and maintaining said cable spaced from engaging said window edge, as said BHA moves axially distally away from said blocking tool.
 
4. A BHA according to example 1 above where said blocking part comprises a pair of arms having proximal ends pivotally coupled to said body part and distal ends, said arms being movable to a position where said distal ends thereof are radially outward of said body part.
 
5. A BHA according to example 4 above where said pair of arms are spring biased toward said open position and are restrained by said drive mechanism in said closed position until said BHA begins to enter said wellbore window.
 
6. A BHA according to example 5 above where said BHA contains wellbore logging sensors selected from the group consisting of resistivity, conductivity, formation pressure, electrical, acoustics, radioactive, electromagnetic, nuclear magnetic resonance and other properties of strata and their contained liquids being investigated and/or monitored.
 
7. A BHA according to example 1 above where said blocking part comprises a plurality of arms having proximal ends pivotally coupled to said body part and distal ends, said arms being movable to a position where said distal ends thereof are radially outward of said body part.
       
 
         [0037]    Further method embodiments of the present invention are exemplified as follows: 
         [0000]    1. A method of reducing potential damage to a wireline having a BHA coupled to its distal end when said wireline is axially extended through and past edges of a window opening that extends from the outer to the inner side of the wall of a lateral wellbore, the BHA having a proximal and distal ends, the wireline and BHA having outer diameter less than that of said window, the method comprising the steps:
       a. removably coupling a blocking tool to the proximal end of said BHA,   b. coupling said BHA to the distal end of said wireline,   c. directing said wireline and BHA to said window in said lateral wellbore,   d. directing said blocking tool to expand to a diameter greater than the diameter of said window,   e. de-coupling said blocking tool from said BHA and allowing said wireline and BHA to axially enter and traverse said window and enter said wellbore while said blocking tool prevents said wireline and BHA from contacting said edges of said window   f. subsequently withdrawing said wireline and BHA outward through said window while said blocking tool continues to prevent said wireline and BHA from contacting said edges of said window, and   g. re-coupling said BHA to the proximal end of said blocking tool as said wireline and BHA are withdrawn through said window.
 
2. The method of claim  2  where said blocking tool has a body part and a plurality of arms with proximal ends pivotally coupled to said body part and distal ends, the arms having a closed position and said arms being movable to an extended position where said distal ends thereof are radially outward of said body part to define a diameter of said blocking tool greater than the diameter of said window, whereby said blocking tool is barred from entering into said window.
 
3. The method of claim  2  where said blocking tool comprises a drive mechanism to move said arms to said extended position and to subsequently withdraw said arms to said closed position.
 
4. The method of claim  2  where said drive mechanism further comprises spring elements biasing said arms toward said open position thereof, and said drive mechanism restrains said arms in said retracted position until directed to allow said spring elements to drive said arms to said open position.
 
5. The method of claim  1  where said BHA contains wellbore logging sensors that are capable of measuring and/or monitoring properties selected from the group consisting of resistivity, conductivity, formation pressure, acoustics, radioactivity, electromagnetic and nuclear magnetic resonance of strata and their contained liquids being investigated and/or monitored.
 
6. A method of reducing the risk of potential damage to a wireline when it is axially extended through and past edges of a window opening that extends from the outer to the inner side of the wall of a lateral wellbore, the window opening being larger than the diameter of said wireline, the method comprising the steps:
   a. providing a blocking mechanism that has width greater than the size of the window opening,   b. positioning said blocking mechanism adjacent said outer side of said lateral wellbore adjacent said window, said blocking mechanism being barred from entering and traversing said window because of its diameter being larger than said window opening, and   c. with said blocking mechanism blocking said wireline from engaging said edges of said window as said wireline is directed to enter and pass through said window, and as said wireline is subsequently withdrawn out of said window.       
 
         [0048]    These and other objects will be evident from the drawings and description herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0049]      FIG. 1  is a schematic fragmentary side elevation view partially in section of a prior art well casing, downhole pipe and wellhead penetrator, 
           [0050]      FIG. 2  is an enlarged detail of a portion of the prior art structure in  FIG. 1 , 
           [0051]      FIG. 3A  is a schematic fragmentary side elevation view of a BHA at the distal end of a wireline in a downhole well casing approaching a lateral wellbore, 
           [0052]      FIG. 3B  is a view similar to  FIG. 3A  showing the BHA in the lateral well bore and inserted through a lateral window, 
           [0053]      FIG. 3C  is a detailed top plan view of the lateral window opening in the lateral wellbore of  FIG. 3B , 
           [0054]      FIG. 3D  is a fragmentary side elevation view in section of the lateral window of  FIG. 3C , 
           [0055]      FIG. 4A  is similar to  FIG. 3A  but shows the BHA with the blocking tool coupled to the distal and of the BHA, 
           [0056]      FIG. 4B  is similar to  FIG. 3B  but shows the BHA having passed through the lateral window and the blocking tool in gauging the inner edge of the lateral window, 
           [0057]      FIG. 5A  is an enlarged side elevation view of the BHA showing the blocking mechanism with arms in closed condition, 
           [0058]      FIG. 5B  is similar to  FIG. 5A  but shows the blocking mechanism with the arms extended transversely and engaging the edges of the inside wall of the lateral window as the BHA begins entry and traverse of the lateral window, and 
           [0059]      FIG. 5C  is similar to  FIG. 5B  but shows the blocking member separated from the BHA and the BHA moved distally away from the blocking member. 
           [0060]      FIG. 5D  is similar to  FIG. 5C  but employs two pairs of arms. 
           [0061]      FIG. 5E  is similar to  FIG. 5A  but illustrates employs longer arms. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0062]    For convenience and clarity in describing these embodiments, similar elements or components appearing in different Figures will have the same reference numbers. 
         [0063]      FIGS. 1 ,  2 ,  3 A- 3 D,  4 A and  4 B illustrate a conventional downhole wellbore  10  whose downhole outer pipe casing  11  inner casing  12  leads to lateral wellbore  13 . Near the top of wellbore  10  is a wellhead penetrator  14  into which is inserted either wireline  16  seen in  FIG. 1  or coiled cable  17  seen in  FIG. 2 . 
         [0064]    At the distal end  20  of wireline  16 , seen in  FIG. 3A , is attached a bottom hole assembly (BHA)  22  which includes selective sensors or at least one sensor for detecting and/or measuring and reporting the existence and characteristics of strata in the vicinity of a lateral wellbore  13  that will be entered by the BHA  22 . At the distal or lead end of the BHA  22  is a steering probe  24  which is used to guide the BHA along a selective path including turn  25 , then into lateral wellbore  13 .  FIG. 3B  shows the BHA having passed through lateral window  26  of lateral wellbore  13  and into area  28 . 
         [0065]      FIG. 3C  provides an enlarged illustration of lateral window  26  in lateral wellbore  13 , this window being an opening milled or otherwise cut in the wall of lateral wellbore  13 . While window  26  appears as an oval opening, its proximal edge  27  is necessarily a friction point or knife edge against which wireline  16  rubs when it traverses window  26  and moves distally into area  28 . It is this knife edge friction point where wirelines become damaged and may even break when they are moved axially back-and-forth during strata examination, with expensive and time-consuming consequences. Thus, a need has existed for a system that has wireline benefits of ease of use, speed and relatively low cost, and also avoids or reduces damage or risk of damage to wirelines. The present invention achieves these objectives as illustrated in  FIGS. 4A ,  4 B,  5 A,  5 B and  5 C described below. Window  26  may have a vertical as well as horizontal orientation. 
         [0066]      FIG. 4A  is similar to  FIG. 3A  showing a downhole outer pipe casing  11 , inner pipe  12 , lateral wellbore  13 , wireline  16  and BHA  22  with its steering probe  24 . The rear or proximal end segment is blocking tool  30  where later separates from the remainder of BHA  22  as further described below. The BHA is shown descending before it turns to approach lateral window  26  and passes the window&#39;s sharp edged  27 . 
         [0067]      FIG. 4B  shows BHA  22  having traveled to and through lateral window  26  with a blocking tool  30  separated from the remainder of BHA  22  and now situated at the inner edge of window  26 . Wireline  16  has moved axially through blocking tool  30  as BHA  22  is directed axially into area or zone  28 . 
         [0068]    An object of this invention is to protect a wireline from damage at the friction point  27  where it must pass, this procedure occurring deep underground. 
         [0069]    The new blocking tool  30  shown in FIGS.  4 B and  5 A- 5 C has a pair of arms  32  that spring out when released. When these arms engage the edges  29  of window/aperture  26  in lateral wellbore  13 , tool  30  is situated at window  26  but blocked from proceeding through the window. While so situated tool  30  serves as a guide or bushing and may include rollers through which cable  16  moves easily axially without encountering sharp edge  27  of window  26 . Arms  32  and associated mechanism not shown in tool  30  position, orient and maintain this tool in the lateral wellbore window  26 , and safely guide wireline  16 . BHA  22  is thus transported axially into zone  28  with no risk of damage to cable  16  from friction, abrasion or cutting by edge  27 . Furthermore, the bushing characteristic of tool  30  facilitates ease, speed and safety of repeated back-and-forth transitions of cable  16 . 
         [0070]    The specific construction of blocking tool  30  may vary, but the one illustrated herein has arms  32  in closed compact position shown in  FIG. 5A , the arms being biased by springs  34  to pivot in the directions of arrows  33  to open positions shown in  FIG. 5B . Release element  36  activated by electronic signals in wireline cable  16  releases arms  32  to spring to their open position, seen in  FIG. 5B , just when the BHA  22  has arrived in the mid-window location. Feet  38  of arms  32  are now spaced apart a distance greater than the width of opening  26 , which bars tool  30  from continuing through window  26 . However, with this movement of arms  32  to their open end blocking position, blocking tool  30  separates from the main body of BHA  22 , the main body then proceeding in the direction of arrow  40  its investigation and monitoring functions, as seen in  FIG. 5C . Separation may be achieved by many different mechanisms, one device illustrated schematically herein is element  39  that engages mating element  39 A and is activated by release element  36 . 
         [0071]      FIG. 5D  illustrates a variation of the blocking tool, having more than two arms, such as a second pair of opposite arms, one being shown as arm  33  and its foot or roller wheel  33 A, the opposite arm not seen.  FIG. 5E  illustrates a still further variation of the blocking tool where the arms  40  are not confined to be stored internal of the housing and thus can be longer and more effective in some situations. 
         [0072]    When BHA  22  is withdrawn back up the wellbore, cable  16  is pulled in the direction of arrow  42  as seen in  FIG. 5C , until BHA  22  returns to its position of  FIG. 5B , and then proceeds backwards and upwards into the wellbore. During retraction of cable  16  the tension in the cable pulls BHA  22  rearward where it reconnects with blocking tool  30 . Blocking tool  30  either returns to its closed position of  FIG. 5A , or alternatively its arms  32  resiliently close enough to fit within downhole pipe  12  as BHA  22  is withdrawn. For arms  32  as illustrated, the feet  38  are formed as rollers to facilitate movement of the feet when they engage edges  29  of window  26 , and when they later ride against the inner wall surfaces of pipe  12  when BHA is retracted. Other forms of blocking tools are possible, but the device presently shown effectively achieves the goal of facilitating passage of cable  16  past sharp edge  27  while eliminating frictional contact therewith and risk of abrasion or other damage to the cable, and does so by attachment of an auxiliary blocking element at the distal end of the BHA that conforms generally to the small diameter dimensions required for ready passage of the BHA within the downhole pipe and the lateral borehole. 
         [0073]    Thus, in this embodiment the BHA carries its own blocking in cable guidance tool all the way down to the lower depths of the wellbore. This tool traverses the extremely narrow diameter of the inner downhole pipe and then opens to a substantially larger diameter in its blocking mode. In this particular case the blocking tool&#39;s arms  32  are carried totally within the outer circumferential dimension of the cylindrical BHA. The location of the cable generally along the central axis of BHA  22  is maintained, as seen in  FIG. 5C , when blocking tool  30  separates from the main body of BHA  22 . 
         [0074]    In the claims herein the bottom hole assembly or BHA for investigation, monitoring or other well logging operations is presumed to include at least one sensor to investigate, measure and or monitor resistivity, conductivity, formation pressure, electrical, acoustic, radioactive, electromagnetic, nuclear magnetic resonance and other properties of the strata and their contained fluids in an area of interest. In embodiments of this invention a selected BHA would have outer dimensions appropriate for being transported through the bore of a downhole and lateral wellbore. 
         [0075]    While the invention has been described in conjunction with several embodiments, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications, and variations which fall within the spirit and scope of the appended claims.