text: referring now to the drawings , and more particularly to fig1 there is shown a top entry apparatus 10 , in accord with the present invention . while descriptive terms such as &# 34 ; above &# 34 ;, &# 34 ; below &# 34 ;, and the like , may be used herein to aid understanding of the present invention , it will be understood that these terms refer to the relative location of the components as illustrated in the accompanying drawings and may be disposed in different relationships in operation , storage , or transportation , as will be understood by those skilled in the art after studying the teachings of the present specification . thus , it is not intended that the invention be construed as being limited in any manner by such terminology . top entry apparatus 10 includes a pack - off body 12 having flange 14 forming a portion of said body as a integral unit or secured thereto as by welding or other means . flange 14 is designed to mate to a top drill pipe drive system in place of a gooseneck assembly as discussed hereinafter . flange 14 is provided as part of pack - off body 12 to reduce the axial space requirements of top entry apparatus 10 . the provision of flange 14 to form a body portion as part of pack - off 44 allows for a very significant reduction in axial space requirements . this is important due to the very small amount of axial space available between the top drive and the drilling blocks and hooks , especially when the larger size drilling blocks are used . apparatus 10 is designed to operable even with the very largest drilling blocks that may sometimes be referred to as &# 34 ; national 5750 &# 34 ; drilling blocks . while it is conceivable that operation without a pack - off could be utilized , in the presently preferred embodiment , a pack - off is provided . a wireline b . o . p . ( blow out preventer ) could also be used for this purpose if placed above circulation sub 47 . this arrangement could allow for some additional axial space . however , as stated hereinbefore , the present invention is usable with all present size drill blocks . top entry apparatus 10 includes adjacent and distal sheaves 16 and 18 , respectively . sheaves 16 and 18 are preferably standard wireline sheaves that are adapted for operation with top entry apparatus 10 . sheaves 16 and 18 include inner rotatable wheels 17 and 19 , respectively . outer sheave housings 21 and 23 do not rotate but are fixed . each rotatable wheel has a respective groove 25 and 27 around the circumference thereof that is sized according to the size of wireline that is used . the grooves 25 and 27 may be seen more readily in fig2 and fig3 . sheaves 16 and 18 are removable and may be changed out for use with different size wireline as desired . a common size wireline for free - point back - off operations as described above might be a 5 / 16 inch wireline . the sheave wheels are secured between beams 20 and 22 that collectively form sheave support arm 24 . braces such as brace 26 , 28 , and 30 support and strengthen sheave support arm 24 . sheave support arm 24 is preferably fixably secured to pack - off body 12 by welding or other means so as to be mounted in cantilever fashion therefrom . bolts 31 and 33 are used to secure sheaves 18 and 16 , respectively , in place within sheave support arm 24 . top entry apparatus 10 is , in a presently preferred embodiment , used to support a wireline for entry through a top drive as discussed hereinafter . the wireline may be threaded through sheaves 16 and 18 and then clamped therein with hinges 32 and 34 that allow wireline shields 36 and 38 , respectively , to open and close . pack - off nut 40 may be used to secure standard wireline pack - off sealing elements discussed hereinafter within a cavity therein . hydraulic quick connect 42 may be coupled to a hydraulic line ( not shown ) to operate pack - off 44 that consists of pack - off body 12 , flange 14 , pack - off nut 40 , the internal pack - off components , and other standard parts . handles 46 are available to help support sheave wheel arm 24 during installation in conjunction with u - damps 48 that are connected to cat lines during installation . u - clamps 48 may also be used to brace sheave wheel arm 24 during operation as with steel cables or chains ( not shown ). flow line 49 is provided to allow pumping into the drill stream for circulation purposes as desired . flow line 49 and circulation sub 47 are connected to a conventional valve and fluid flow line ( not shown ). alternatively , a circulation sub 47 and valve arrangement may also be provided in drill pipe 50 as shown in fig7 . fig7 provides an overview of the overall drilling system . wireline unit 52 , that may of course also be a skid mounted unit or the like , is rigged up for operation in derrick 54 . drill pipe 52 may be rotated by top drive unit 56 . top drive unit 56 is supported by drilling blocks 58 . in this wireline rigging arrangement , there is lower sheave 60 and upper sheave 62 that supports wireline 64 . wireline 64 is fed to distal sheave 18 of top entry apparatus 10 that is mounted between drilling blocks 58 and top drive unit 56 . lower and upper sheaves 60 are normally secured to derrick 54 by means of a strength cable or chain arrangement . as shown in fig7 top entry apparatus 10 may be used with only lower sheave 60 as desired . providing an upper sheave 62 allows the pipe to be moved without affecting the position of the wireline to thereby keep the wireline measurements constant . if only the lower sheave 60 is used , then movement of the drill pipe causes the wireline to also move . however , since this movement will not be too great if the pipe is stuck , it may be desirable simply to eliminate the need to rig up upper sheave 62 . typically rigging up time for an upper sheave such as sheave 62 is about 15 - 30 minutes . another consideration in whether to use an upper sheave is that while using only the lower sheave , movement of the wireline while stretching the pipe may affect free - point tool operation because of the corresponding cable movement , and therefore consideration of the type of free - point tool used is necessary . referring to fig2 it will be seen that cavity 66 in pack - off 12 is provided for standard sealing elements that may include split upper brass elements 68 , split elastomeric elements 70 , and split lower brass elements 72 . the elements are typically split to facilitate assembly . a bore or hole 74 is provided through the sealing elements that is sized for the particular size wireline used . if a different size wireline is used , then the sealing elements may be readily changed out . hydraulic pressure provided through hydraulic quick connect 42 results in compression of the components as with a piston member . other types of relatively short length sealing elements could be used such as grease seals and the like that are sometimes preferably used for higher pressure operations with the wireline being movable at relatively high speeds without losing the seal . smaller diameter wire is preferable for high pressure work . standard pack - offs with standard pack - off elements will typically seal with a stationary 5 / 16 inch wireline at about 5 , 000 to 10 , 000 psi . depending on the condition of the wireline ; i . e ., if the wireline is packed or covered with grease or well oiled then the seal will be higher . in fig4 top entry apparatus 10 is secured to top drive unit 56 . it will be understood that part of method of the present invention first requires removal of the gooseneck assembly whereby an upper top drive frame 76 is accessible to provide flange connection 78 to mate with flange 14 on pack - off 44 . top entry apparatus 10 is thereby preferably bolted and / or threadably secured as with bolts 80 and threaded pin / socket connections 82 . thus , access is available to drill pipe tubular bore as indicated schematically in dash as drill pipe bore 83 wherein it will be understood that the drill pipe may be located further below the indication and be of various sizes . a feature of the present invention is that it allows a choice in rig ups with the associated derrick sheave ( s ). a lower sheave 60 may be used alone with top entry apparatus 10 . alternatively , an upper 62 and lower 60 sheaves may be used as with the presently preferred rig up , at least for free - point back - off operation . relative advantages of the different rig ups for the free - point back - off operation have been discussed hereinabove . however , this unique rig up feature can be very useful in other types of rig up situations . for instance , in multi - well offshore rigs , it may be necessary to have multiple sheaves located at multiple levels due to well - head access problems that may occur in those situations whereby the wireline unit may be located on a different level and at a different part of the offshore rig . the flexibility of being able to direct the wireline in either direction could be quite helpful in those rig up situations . it may also be helpful and for other situations that may be encountered or already known to those skilled in the art . this unique rig up feature of the present invention can be seen in fig4 and fig6 where the preferred wireline 64 rig up for free - point back - off operation is indicated in solid lines . the optional single lower sheave wheel rig up for wireline 64 is indicated in dashed lines . for the preferred rig up indicated by solid lines , clearances are provided such that wireline 64 does not contact an outer diameter 84 or lower surface 86 of hook portion 88 of traveling block 58 . if the single sheave rig up is used , then clearances are provided such that wireline 64 does not contact an outer diameter region 90 or upper surface region 92 of top drive unit 56 . moreover , the angles provided for bending the wireline are designed not only to avoid engagement or frictional rubbing with equipment that is in a confined region , but also is designed to be within the bending specifications for wirelines having electrical conductors . the sheaves are preferably of the approximately 14 inch diameter readily available standard type that is often used with single conductor 5 / 16 inch wireline cable . however , due to the use of decreased bending angles , even multi - conductor cable or larger diameter cable may be used as specifications allow . referring to fig4 as wireline 64 emerges from pack - off 44 it encounters a first bending region 94 that is provided by adjacent sheave wheel 16 . first bending region 94 preferably ranges from about sixty degrees to about eighty degrees depending on the type of rig up . if cable 64 goes over both sheave wheels 16 and 18 , then the angle of first bending region is decreased . although the presently preferred embodiment bends as shown , top entry apparatus 10 could have different bending angles as from about twenty to over ninety degrees . for other rigging situations in which the present invention may be used , different angles are possible . it will be understood that although the preferred embodiment of the present invention is directed to use with top drive systems , it is not intended to be so limited and may be used with other operations that involve other rigging requirements . a second bending region 96 for wireline 64 is provided at a radially outwardly position from the drill pipe 50 , traveling block 58 , and top drive unit 56 . thus , top entry apparatus 10 effectively controls the path of the wireline and directs it radially outwardly to a safe position . second bending region 96 will remain at a constant fixed distance form upper top drive frame 76 as block 58 moves the pipe string longitudinally . second bending region 96 bends wireline cable 64 by an amount of from about one - hundred degrees for the preferred rig up to about one - hundred thirty five degrees for the single derrick sheave rig up . as with the first bending region , these angles could be varied for use of the present invention in other rig up situations as desired . the position of the bending region may be designed by placement of the sheave and the position of bend 102 in the sheave support arm 24 . sheave support arm 24 may be of various shapes , however in the presently preferred embodiment it is provided generally with an s - shape . a first bend 100 is provided proximate to pack - off 44 and a second bend 102 is provided distal from pack - off 44 . other configurations and positions of bends in support arm 24 could also be provided . sheave support arm 24 is braced and dimensioned so as to be able to withstand a substantial moment acting on it as will applied in different directions depending on the type of derrick sheave rig up . u - bolt 48 may be used to brace sheave support arm 24 with cables or chains as discussed hereinbefore . fig5 shows the top drive unit 56 with gooseneck flow line 104 connected thereto . this is the situation before rig up of the present invention and after rig down . thus , riser portion 106 of the circulation flow line is removed and replaced before and after the free - point back - off operation , respectfully . while there is very little axial clearance 108 in this region , the present invention allows for wireline operation in a very tight situation without frictionally engaging the wireline on surfaces that may be otherwise damaged . with the use of the largest hook 88 and drilling block 58 known to applicant , the axial clearance 108 is approximately 13 inches . it will be understood that while the present invention is directed to use of wireline such as wireline 64 , other types of flexible line members may also conceivably be used such as a very flexible coiled tubing as may be available at the present or in the future . the two - sheave fixed assembly of the present invention is therefore adaptable to other operation and with other rotational devices such as , by way of example only , roller systems . furthermore , the concept of a sheave support arm 24 being cantilevered from the pack - off 44 may be applied to additional sheaves in such an arm to provide smaller bends and / or greater radially movement of a flexible elongate line member . in operation , the first step for rigging up is to disconnect gooseneck flow line 104 at the top of top drive unit 56 . top entry apparatus is then preferably bolted onto or otherwise secured as with securing member flange 14 . the drill pipe is set in slips and at least one pipe such as top pipe 110 is disconnected using top drive unit 56 . the top sheave may be rigged up if it is used . the wireline from the appropriate derrick sheave , that may be either an upper or lower sheave , is then threaded or stripped through top entry apparatus 10 by opening hinges 32 , 34 and then closing guards 36 , 38 to maintain the wireline in the sheaves . the cable head may then be striped or threaded through the pack - off and through the drill pipe . the pack - off sealing elements are then positioned into the pack - off and pack - off nut 40 is tightened . a downhole tool , such as a collar locator , a string shot or a free - point tool or a combination of such tools well known to one skilled in that art , may be connected to the cable head . wireline unit operator can then pull the tool up into the top pipe 110 using wireline unit 52 . the drill pipe can then be reattached and the wireline operation may proceed . if it is necessary to pump into the pipe , then flow line 49 or circulation sub 47 may be used . the top drive unit 56 can be used to rotate , apply torque , and lift the drill pipe string using drill block 58 . in this manner , it is now no longer necessary to use a pipe tong to maintain torque on the drill string as the drill string is moved longitudinally . in the alternative embodiment shown in fig8 the top entry apparatus 10 is provided with threaded connections 15 for releasably connecting a device with standard tubular members used for the drilling of wells . all other like - numbered components are the same as those described and discussed above in connection with fig2 , and 4 . referring to fig9 which is a partially schematic drawing of an alternative embodiment , the top entry apparatus 10 is releasably connected to a lifting sub or pup joint 114 , which is supported by elevators 112 . elevators 112 are releasably engaged to clamp around the shoulder or upset portion of the lifting sub 114 in conventional manner . the elevators 112 are connected to bails 87 which are carried by conventional hook assembly 88 such as shown in fig6 or other connection means of the traveling block 58 , well - known to those skilled in the art . as an alternative to pump - in 49 , the lifting sub 114 may be connected to a circulation sub 47 ( as shown in fig7 ) or to pump - in sub 116 as shown in fig9 for the attachment of the conventional valve and hydraulic line ( not shown ) to permit the continuance of fluid flow during the wireline operations . a conventional in - line swivel 118 is attached below the lifting sub to permit the tubular drill string 110 ( as shown in fig7 ) below to rotate . the in - line swivel 118 is attached to the top of other forms of top - drive units known in the art , such as older versions of the varco top - drive units 122 , in an arrangement shown schematically here , which supplies rotational force to the drill string 110 which is threadably connected to said top - drive unit 122 in a conventional manner during the wireline operation as desired . it may be appreciated by those skilled in the art that other subs may be placed in the arrangement of the alternative embodiment shown in fig9 as preferred . fig9 shows valve sub 120 which provides a means of regulating the fluid flow through the top drive unit 122 before and after wireline operations , while the apparatus is connected and disconnected for normal drilling operations . the foregoing disclosure and description of the invention is illustrative and explanatory thereof , and it will appreciated by those skilled in the art , that various changes in the size , shape and materials as well as in the details of the illustrated construction or combinations of features of the various top entry system elements may be made without departing from the spirit of the invention .