Side entry sub with tension release wireline cable clamp

Disclosed is a side entry sub with tension release wireline cable clamp. The side entry sub includes a tubular member having a port for the passage of the wireline cable into the interior of the tubular member. A cable clamp holder is positioned on the tubular member adjacent the port. The cable clamp holder has an axially extending passage with a cable clamp mounted therein. The cable clamp includes two clamp parts that are adapted to grip the cable therebetween. The cable clamp parts are movable from a gripping position to a releasing position responsive to axial movement with respect to each other in the clamp holder passage.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The present invention relates generally to a drill string sub having a side 
entry port for insertion and removal of wireline cable and more 
particularly to a side entry sub with a tension release wireline cable 
clamp. 
B. Description of the Prior Art 
The drilling and completion of oil or gas wells commonly involves the use 
of apparatus made up of a drill string having a steering tool or a 
plurality of logging tools positioned within or affixed to the drill 
string near its lower end. A communication wireline cable is often used 
for transmitting to the surface the information gathered by such tools. 
Devices known as "mud motors" or "turbo drills" are often employed during 
well drilling operations. These devices are attached at the lower end of 
the drill string above the bit. During mud motor drilling operations, high 
pressure drilling mud is circulated down the interior of the drill string, 
through the mud motor and bit and up the annulus of the well bore. The 
action of the mud in the mud motor rotates the bit without rotating the 
drill string. Mud motor drilling is particularly useful in the drilling of 
deviated holes where the bit may be kicked out by the use of a bent sub. 
During such mud motor drilling operations, a steering tool is often 
positioned inside the drill string above the mud motor. The steering tool 
monitors the inclination and azimuth of the well bore during drilling, so 
that course corrections may be continuously made. 
Additionally, there has recently been developed a system for logging a zone 
of interest by the use of drill pipe. Conventional open hole wireline 
logging of highly deviated or bad holes is often impossible because 
logging tools cannot be lowered into the zone of interest by gravity. 
Pump-down techniques, often used in highly deviated holes, are both time 
consuming and expensive. 
One method for establishing communication with steering or down hole 
logging tools in drill pipes involves insertion of a wireline cable 
through a port in an element of the drill string known as a "side entry 
sub" to form a hard wire link between the down hole tool and the surface. 
Thus, a fixed length of cable is contained within the drill string below 
the side entry sub. The cable between the side entry sub and the surface 
extends outside the drill string. 
One benefit of the wireline cable's entry through a side entry sub stems 
from the fact that new drill pipe sections may be added to the drill 
string without first withdrawing the cable from the well bore. In 
contrast, if the wireline cable is run totally inside the drill string 
from the surface to the down hole tool, the most feasible method for 
adding a pipe section to the drill string involves the complete removal of 
the cable from the drill string, followed by addition of the new pipe 
section, and reinstallation of the cable. Inclusion of a side entry sub in 
the drill string renders unnecessary such repeated cable reinstallation, 
increasing the speed of operation, and lowering its cost. 
Typically, in the case of logging, the bottom hole tools are assembled and 
then lowered into the hole on drill pipe to a depth directly above the 
interval of open hole to be logged. The logging cable is passed through 
the port of the side entry sub and connected with an electrical connector 
or latch. The sub is then made up to the drill string and the latch and 
cable are lowered or pumped down inside the drill string to the logging 
assembly. Once the logging cable is latched to the logging assembly, the 
cable is clamped mechanically to the side entry sub, whereupon additional 
lengths of drill pipe may be made up and lowered into the hole. 
When the cable is in place, it is possible to circulate through the drill 
string and reciprocate the drill string. However, it may be desired to 
remove the cable from the drill string during drilling or logging 
operations, for example, if the cable becomes damaged. Another important 
reason for removing the cable would be to vacate the drill pipe after it 
has become stuck. Retaining a length of cable inside such drill pipe would 
severly hamper the running of tools, such as free-point indicators and 
explosive devices, down the interior of the drill string. Also, if the 
drill string must be rotated, the portion of cable extending along the 
outside of the drill string and running to the surface would probably be 
damaged and would severly interfere with drill string rotation. When it is 
desirable to remove the cable from the drill string, the cable usually is 
removed by retrieving it through the port in the side entry sub. 
The presently existing side entry sub cable clamp includes a pair of clamp 
parts that are fastened about the cable by bolts or the like. The fastened 
together clamp parts are in turn connected by shear pins to the side entry 
sub. When it is desired to retrieve the cable, a tension force is exerted 
on the cable sufficient to shear the shear pins and the cable and sheared 
clamp parts are pulled to the surface. When the clamp parts reach the 
surface, they are removed from the cable and the cable is then pulled the 
rest of the way out of the hole. 
The removal of the clamp parts is a time consuming operation. The reeling 
up of the cable must be slowed down when it is expected that the clamp 
parts will reach the surface and must be stopped entirely when the clamp 
parts are removed. Since the pulling of the cable is normally pursuant to 
some emergency, time is of the essence. 
Accordingly, it is an object of the present invention to provide a side 
entry sub with a tension releasable cable clamp that does not have to be 
removed from the cable as the cable is pulled from the hole. It is a 
further object of the present invention to provide a side entry sub with a 
tension releasable cable clamp wherein the cable clamp remains with the 
side entry sub after the cable is released. 
SUMMARY OF THE INVENTION 
Briefly stated, the foregoing and other objects are accomplished by the 
side entry sub of the present invention. The side entry sub includes an 
elongated tubular member having a port formed therein for the running of a 
cable from the exterior into the bore of the tubular member. A clamp 
holder is positioned on the tubular member axially adjacent the cable 
port. The clamp holder has an axially extending passage within which is 
mounted a cable clamp. The cable clamp includes first and second parts, 
each of which includes a cable gripping surface adapted to grip the cable. 
The cable clamp is normally fixed against axial movement within the clamp 
holder passage by shear bolts. When the cable clamp is so fixed, the clamp 
parts are held in gripping relationship with the cable. Upon the 
application of a tension force above a preselected amount, the shear bolts 
shear and allow the cable clamp to move axially within the clamp holder 
passage. Movement of the clamp causes the clamp parts to move out of 
gripping relationship with the cable and thereby allow the cable to be 
pulled freely out of the cable port while the clamp parts remain in the 
cable clamp holder. 
One of the cable clamp parts is axially longer than the other part, but 
both are shorter than the length of the clamp holder passage. The cable 
clamp parts are held together by an arrangement which allows axial 
movement therebetween and lateral movement responsive to such axial 
movement. More specifically, one of the cable clamp parts has a plurality 
of inclined bolt holds, which are adapted to receive plurality of inclined 
holes. Each of the bolts has a threaded shank and enlarged head. The other 
clamp part has a plurality of elongated apertures with each aperture 
including an elongated counterbore with a sloping bottom. The bolt shanks 
are axially slidingly received in the apertures and the bolt heads are 
axially slidingly received in the counterbores. Axial movement between the 
clamp parts causes the bolt heads to go into and out of engagement with 
the sloping bottoms of the counterbores. Thus, in one position the heads 
of the bolts engage the bottoms of the counterbore and hold the cable 
clamp parts in gripping relationship. When the cable clamp parts are moved 
axially with respect to each other, the bolt heads move out of engagement 
with the counterbore bottoms and allow the cable clamps to release. 
The axial movement between the cable clamp parts with respect to each other 
is provided by a stop shoulder in the cable clamp holder passage in 
combination with the differing lengths of the cable clamp parts. When the 
cable clamp parts are restrained against axial movement in the cable clamp 
holder passage, the bolt heads are in tight engagement with the 
counterbore bottoms. One end of the cable clamp part having the apertures 
and counterbores extends axially outward of the end of the other part. 
Upon release of the shear bolts, the cable clamp parts move together 
toward the stop shoulder in the cable clamp passageway. The end of the 
cable clamp holder having the apertures and counterbores strikes the stop 
shoulder first and stops while the other cable clamp part continues to 
move. The continued movement of the other cable clamp part causes the bolt 
heads to move out of engagement with the counterbore bottoms.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, and first to FIG. 1, a drilling rig 10 is 
shown above a well bore 12. The lower portion of well bore 12 is deviated 
at a high angle away from the vertical. An elongated drill string 14 
extends down into well bore 12 and has a logging tool assembly 16 attached 
to its lower end. Drill string 14 is made up of a plurality of end-to-end 
connected sections of pipe, each designated by the numeral 18. 
Drill string 14 extends down through the floor 20 of rig 10 into well bore 
12. A conventional rotary table and slip assembly 22 for rotating and 
supporting drill string 14 is shown. A power wench assembly 24 is 
connected to an elongated flexible cable or wireline 26 and is suitable 
for paying out or reeling in the cable. Cable 26 passes over suitable 
sheaves 28 and 30 in rig 10 and into well bore 12 adjacent drill string 
14. A side entry sub 32 is provided in drill string 14 so that cable 26 
may enter the interior of drill string 14. 
In positioning logging tool assembly 16 for performing log operations, or 
other procedures in accordance with the particular type of tool being 
used, the tool is typically lowered to the upper portion of the zone of 
the well bore to be surveyed and the side entry sub 32 is added to drill 
string 14. Wireline cable 26 is then inserted through a suitable port in 
side entry sub 32 and lowered or pumped down the interior of drill string 
14 for connection to logging tool assembly 16 by means of a latch or 
connector assembly, designated in phantom by the numeral 34. The details 
of latch 34 are not a part of the present invention and it will suffice to 
say that the latch may be withdrawn with the cable through the cable port 
in a side entry sub 32 or, alternatively, the wireline cable may be 
provided with a weak link which will permit the cable to part at a point 
within the interior of the drill string when subjected to a predetermined 
tension force. In this way, the main portion of cable 26 may be withdrawn 
from the interior of the drill string through side entry sub 32. This 
procedure is necessary, particularly in regard to operations with drill 
strings in angled or deviated well bores, since it may be necessary to 
rotate the drill string to unstick it or to carry out some other 
operation. 
If the drill string is rotated with the wireline cable in place through the 
side entry sub, the portion of the wireline cable extending up the well 
bore between the side entry sub and the rig floor may become entangled and 
limit the rotation of drill string, or the cable may break. It is 
therefore desirable to withdraw the cable prior to any rotation of the 
drill string. However, it is desirable during normal operations that the 
cable be firmly clamped to the side entry sub. 
Referring now to FIG. 2, side entry sub 32 includes an elongated cable 
clamp holder 36. Cable clamp holder 36 includes an elongated axially 
extending passage 38 which has mounted therein a cable clamp 40. Cable 
clamp 40 is slidable within passage 38 between a first end 42 and a second 
end 44. 
Referring now to FIGS. 3 and 4, cable clamp 40 includes a first part 46 and 
a second part 48. First part 46 and second part 48 each include elongated 
semicylindrical cable gripping surfaces 50 and 52, respectively, which are 
adapted to grip cable 26. Cable gripping surfaces 50 and 52 preferably 
have a knurled or gripping finish so as to enhance their gripping ability 
as will be explained in detail hereinafter. 
First part 46 and second part 48 of cable clamp 40 are normally held in 
gripping relationship with cable 26. Cable clamp 40 is normally fixed 
against axial movement within passage 38 of cable clamp holder 36 by means 
of shear bolts, including, for example, shear bolt 54. The shear bolts 
engage the sides of cable clamp holder 36 and first part 46 of cable clamp 
40. The shear bolts normally hold first part 46 and second part 48 of 
cable clamp 40 against first end 42 of passage 38 of latch holder 36. 
Cable clamp holder 36 includes on either side of passage 38 cable guideways 
56 and 58. Adjacent lower cable guideway 56, side entry sub 32 includes a 
port, designated generally by the numeral 60, for the passage of cable 26 
from the exterior of side entry sub 32 into the bore 62 of side entry sub 
32. Port 60 is defined by an insert 64, which includes suitable seals and 
which may include a valve mechanism for closing the port when cable 26 is 
withdrawn therefrom. 
Referring now to FIG. 5A, first part 46 and second part 48 of cable clamp 
40 are held together by means of a plurality of bolts 64. Each bolt 
includes a threaded shank 66 and an enlarged head 68. The shanks 66 of 
bolts 64 are received in threaded bolt holes 70 in first part 46 of clamp 
40. Bolt holds 70 and bolts 64 are inclined axially in the direction 
toward second or upper end 44 of passage 38 of cable clamp holder 36. 
Second part 48 of clamp 40 is connected to first part 46 by means of a 
plurality of apertures 72, which engage bolts 64. Each aperture 72 
includes an elongated slot 74 which axially slidingly receives shank 66 of 
bolt 64. Slot 74 is keyhole shaped and includes an elongated first portion 
76 having a width less than the diameter of head 68 of bolt 64 and a 
circular second portion 78 having a diameter substantially the same as 
that of head 68. 
Each aperture 72 includes an elongated counterbore 80 which slidingly 
receives heads 68 of bolts 64. Each counterbore 80 has a floor 82 which 
slopes inwardly and upwardly toward first part 46 of clamp 40. 
Second part 48 of clamp 40 is longer than first part 46. As shown in FIG. 
5A, when clamp 40 is in gripping relationship with cable 26, the first 
ends 86 and 88 respectively of first part 46 and second part 48 abut lower 
or first end 42 of passage 38. The heads 68 of bolts 64 firmly engage the 
floors 82 of counterbores 80, thereby holding first part 46 and second 
part 48 of clamp 40 together in gripping relationship with cable 26. Clamp 
40 is restrained against axially upward movement by shear bolts 54. 
When it is desired to release clamp 40 and retrieve cable 26, an upward 
tension is applied to cable 26. When the upward tension exceeds a 
predetermined amount, shear bolts 54 shear and release the connection 
between first portion 46 of clamp 40 and clamp holder 36. The release of 
the connection allows clamp 40 to move axially in passage 38 toward second 
end 44. Since second part 48 of clamp 40 is longer than first part 46, its 
second end 90 contacts second end 44 of passage 38 before the second end 
92 of first part 46. The contact of second end 90 of second part 48 causes 
second part 48 to stop. However, first part 46 continues to move axially 
until its second end 92 contacts second end 44 of passage 38 as shown in 
FIG. 5B. The axial movement between second part 48 and first part 46 
causes the heads 68 of the bolts 64 to move out of engagement with the 
floors 82 of the counterbores 80. Such movement thereby allows second part 
48 to move away from first part 46 and out of gripping relationship with 
cable 26. Cable 26 may thus be pulled freely out of side entry sub 32. A 
plurality of retainers 94 are provided in cable clamp holder 36 to keep 
second part 48 from falling out after release of cable 26. As is best 
shown in FIG. 2, each retainer 94 has a generally cylindrical head having 
a flat side 96. 
In operation, drill string 14 with logging tool assembly 16 connected 
thereto is run into well bore 12, to a point above the zone of interest. 
Side entry sub 32 is then inserted in the drill string and cable 26 is run 
into side entry sub 32 through port 60. Cable 26 is then lowered or pumped 
down drill string 14 until latch 34 connects with logging tool assembly 
16. With latch 34 so connected, cable 26 is positioned between first part 
46 and second part 48 of cable clamp 40. Preferrably, cable clamp 40 is 
assembled by inserting the heads 68 of the bolts 64 through the round 
portions 78 of apertures 72 and then sliding second part 48 of cable clamp 
40 axially until the first ends 86 and 88 of first part 46 and second part 
48, respectively, coincide. Then, bolts 64 are tightened and the assembled 
cable clamp 40 is inserted into cable clamp holder 36 and fixed in place 
by shear bolts 54, as shown in FIG. 5A. The retainers 94 are then rotated 
to the position shown in FIG. 2. After cable 26 has been clamped to side 
entry sub 32, additional sections of pipe 18 may be added and run into 
well bore 12. 
In the event that it becomes necessary to retrieve cable 26, a tension 
force is applied to cable 26 sufficient to shear bolts 54. With shear 
bolts 54 sheared, cable clamp 40 moves toward second end 44 of cable clamp 
holder passage 38, as shown in FIG. 5B, and releases cable 26. Retainers 
94 keep second part 48 of cable clamp 40 from falling out of passage 38. 
Further modification and alternative embodiments of the apparatus of this 
invention will be apparent to those skilled in the art in view of this 
description. Accordingly, this description is to be construed as 
illustrative only and is for the purpose of teaching those skilled in the 
art the manner of carrying out the invention. It is to be understood that 
the forms of the invention herewith shown and described are to be taken as 
the presently preferred embodiments. Various changes may be made in the 
shape, size and arrangement of parts. For example, equivalent elements or 
materials may be substituted for those illustrated and described herein, 
parts may be reversed, and certain features of the invention may be 
utilized independently of the use of other features, all as would be 
apparent to one skilled in the art after having the benefit of this 
description of the invention.