Drill stem mud wiping apparatus

A wiping tool for free fall in a drill stem is disclosed. The wiping tool is adapted to be dropped in the drill stem to wipe the inner wall. It is constructed with an elongate mandrel terminating at upper and lower subs. The upper sub supports a fishing neck and the lower sub encloses a check valve assembly. Adjustable weight means are affixed to the lower sub. Wiping is accomplished by an elongate sleeve having narrow upper and lower ends slideably mounted on the central mandrel, and the sleeve is enlarged at central portions to a diameter sufficient to wipe the wall of internal upset pipe, and wherein said sleeve is resilient, and is therefore able to reduce in diameter on passing through an internal upset and resiliently restores to the initial diameter after passing through the upset. A closed system stores incompressible fluid to keep the sleeve filled and inflated.

BACKGROUND OF THE DISCLOSURE 
This apparatus is directed to a device to be placed in a drill stem at the 
time that the drill stem is pulled from the well borehole during drilling 
and, more particularly, is a device for weighting the column of mud in the 
drill stem. This is a continuation-in-part of U.S. Pat. No. 4,923,011 
issued on May 8, 1990 which is incorporated by reference. 
During drilling of a well, it is necessary to periodically remove the drill 
stem from the borehole, typically to replace the drill bit. When this 
occurs, the drill stem is normally lifted up and disassembled joint by 
joint or perhaps stand by stand. In the process of removing the pipe from 
the borehole, it is normally lifted in a wet condition and, upon 
unthreading, may spill drilling fluid on the rig floor creating a risky 
condition. Moreover, this destroys the hydrostatic balance which existed 
in the borehole. Heretofore, this has been overcome by slugging the column 
of mud in the drill stem with a slug of drilling fluid of heavier density 
so that it will tend to keep the level of mud down in the drill pipe due 
to the hydrostatic unbalance created on slugging. In the case of oil base 
muds, it requires the addition of weight material which has to be removed 
for best results when drilling is resumed. 
The apparatus set forth in the parent disclosure hereof is thought to be a 
successful device which provides the necessary wiping inside the drill 
stem. This disclosure, however, sets out a further improvement which is 
directed to the resilient sleeve 25. In the referenced parent disclosure, 
the sleeve 25 is a resilient sleeve which is supported between upper and 
lower rings 27 and 28. It is made of resilient material so that it can 
flex and it tends to inflate, bowing outwardly to create a contact area 
which tends to wipe the inside of the pipe. Ordinarily, it provides 
contact against the full circle of the surrounding or enclosing axial 
passage through the drill stem. There are, however, internal upsets which 
are encountered periodically along the drill stem. When they are 
encountered, this requires the sleeve to contact against the upset 
regions, thereby shrinking to prevent leakage past the upset region. The 
present improvement sets forth a method and apparatus for further assuring 
that the sleeve is expanded radially outwardly so that the sleeve 
maintains more reliable contact with the surrounding drill stem, in 
particular better contact with the surrounding drill stem. Thus 
dynamically, the device will pass downwardly in a drill stem, being forced 
to shrink or narrow on encountering the internal upset, and is freed to 
expand radially outwardly after passing through the upset so that the 
present apparatus provides a more sure and certain contact region just 
below the upset. It is very helpful to maintain the resilient sleeve 25 at 
a fully inflated condition for assuring contact against the surrounding 
upset and the sidewall just below the upset. In the absence of certain 
contact, it is possible for leakage to occur and this system overcomes 
that tendency. 
The present system has the further advantage of overcoming the tendency to 
leak by assuring a fully inflated sleeve during traversing of a drill 
stem. Moreover, the sleeve is filled with an incompressible fluid which is 
momentarily compressed when passing through an internal upset which fluid 
overflows from the sleeve into a chamber. The chamber is maintained under 
pressure which is assured by a cylinder in the chamber exposed to ambient 
pressure. Pressure on the tool dynamically moves the piston within the 
cylinder to adjust pressure equalization within the sleeve. This change in 
piston location maintains fluid pressure within the tool keeping the 
sleeve expanded in light of its physical location relative to upsets of 
the drill stem. 
The present apparatus sets out an elongate tool which is buoyantly carried 
on the top of the mud column in the drill stem as the stem is being pulled 
and which includes a central elongate mandrel. The mandrel is of 
relatively narrow diameter to receive thereon a telescoped and slideable 
resilient sleeve. The resilient sleeve is not shaped as a cup, but rather 
incorportes upper and lower ends which are relatively narrow and are 
mounted on circular rings to enable telescoping movement of each end 
independently on the mandrel. The sleeve bows outwardly at the central 
portions and defines a resilient wiping surface. This surface is able to 
pass through the internal upset pipe. When it does, the sleeve is 
constricted slightly, forcing the two ends farther apart and which are 
both free to move. The two ends of the sleeve are arranged in a circular 
construction around the mandrel. Conveniently, shoulders at the upper and 
lower ends of the sleeve supported by the mandrel define the centered 
sleeve position, but such sleeve movement is nevertheless permitted during 
transition through an internal upset. The transition thus occurs as the 
device is traveling through the drill stem and yet permits the sleeve to 
slide through the internal upset, shrinking at the fatter central portion, 
forcing the two ends thereof relatively apart, and moving at one end or 
the other to accommodate appropriate elongation on diametric shrinkage, 
and further restoring to the original shape after transition through the 
internal upset. This is markedly different from cups which face upwardly 
or downwardly. Likewise, it is different from sleeves of substantially 
uniform diameter, and is substantially different from the wiping action 
provided by such devices. 
The foregoing briefly sets out certain aspects of the present disclosure, 
but details of the present apparatus will become more readily apparent and 
understood in conjunction with the drawings of the preferred embodiment, 
and it is therefore a structure including the components illustrated 
discussed below for the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Before beginning with a description of the present disclosure, the 
disclosure found in the above referenced patent 4,923,011 is hereby 
incorporated by reference. It explains generally the wiping action which 
occurs in the apparatus, particularly when a drill stem is pulled from a 
well borehole which is normally filled with drilling fluid. The fluid is 
located on the exterior and interior of the pipe. In particular, there is 
a standing column of drilling fluid accumulated in the pipe as it is 
pulled from well. A typical procedure envisions disassembly of the drill 
stem stand by stand. A stand is normally three joints of pipe which have 
an aggregate length of about ninety to ninety-five feet in length. One 
stand of pipe is normally unthreaded and pushed to the side so that it 
stands erect in the derrick. It is stored momentarily there as the entire 
drill stem is disassembled and stored. As will be understood, these 
operations are accomplished quite rapidly. As each stand is unthreaded, 
there is a substantial mess created as drilling fluid within that stand of 
pipe drips on the rig floor, making the work far more dangerous than it 
should be. The foregoing disclosure is directed to a wiping device which 
assists in wiping the drill stem on the inside. This reduces the spillage 
of drilling fluid. Moreover, it serves as a safety device in the event 
there is an unwanted pressure surge from the well. The pressure surge 
might otherwise travel up through the string of drill pipe. 
The present version particularly focuses on improvements in the expandable 
of flexible sleeve 25. Specifically, it is expanded and heling in wiping 
contact both at the internal upsets and as it traverses the length of the 
drill pipe. 
The further improvement will therefore be described by referring generally 
to the construction of the device 50. It can also be constructed with 
slips as exemplified in the embodiment 50 of the foregoing embodiment. In 
any case, the numeral 70 identifies the improved drill stem mud wiping 
apparatus which is positioned in a string of drill pipe 71. There is a 
hollow sub 72 at the upper end which is provided with an axial passage 73 
from the upper end. The upper end, of course, includes a fishing neck 74 
(of conventional shape) which enables the device to be retrieved by means 
of conventional overshot tools. The sub 72 communicates with a check valve 
75 biased by a spring 76 to permit downward flow. Flow upwardly through 
the passage 73 is prevented by the check valve 75 which incorporates a 
sphere larger than the valve seat confronting it. The sphere is held in 
contact with the seat by the coil spring 76. When the fluid pressure 
acting downwardly against the sphere exceeds a predetermined pressure 
level, the spring is forced open, and fluid flow then occurs. A supportive 
sleeve includes multiple ports or openings to the exterior and axially of 
the spring 76 which extend downwardly to an opening 77. This communicates 
downwardly into the elongate stem or mandrel 78. The mandrel 78 extends 
from FIG. 1 downwardly to the sleeve which will be discussed and which is 
shown better in FIG. 2. There is a central mandrel 79. This mandrel 79 is 
concentric within a resilient sleeve 80 which is inflated with fluid and 
forced to expand, expanding something in the fashion of a balloon. It has 
a stiff ring 81 at the upper end. The ring 81 is similar to that disclosed 
in the foregoing embodiment and is therefore able to telescope on the 
exterior of the mandrel. 
Both ends of the resilient sleeve 80 are constructed in the same fashion 
and they are both able to telescope. That is, they can slide to and fro 
around the central mandrel 79. The range of travel, however, is limited by 
shoulders which are on the interior of the sleeve. There is an upwardly 
facing shoulder and a downwardly facing shoulder also is included. In this 
particular instance, the shoulders are not continuous shoulders machined 
in the mandrel as set forth in the foregoing disclosure. Rather, the 
shoulders here comprise protruding levers 82, therebeing preferably three 
or four at the top end and three or four at the bottom end. When these 
levers 82 collectively protrude, they define a shoulder which prevents the 
stiffened ring 81 from traveling any farther than the shoulder will 
permit. These shoulders are defined by pivotally mounted elongate levers. 
These levers have a retracted position which can be fully withdrawn so 
that the sleeve 80 and the associated end located rings 81 will slide over 
and past the shoulders. This is helpful during assembly. The shoulders, 
however, being pivotally mounted, are able to deflect radially outwardly 
into the abutting location shown in FIG. 2 of the drawings. The shoulders 
are forced outwardly by the concentric construction of the multiple parts 
of the mandrel at 78 and 79. It will be observed that the mandrel is 
formed of two concentric parts. The mandrel 79 thus has an elongate window 
cut for the finger like levers 82, having a pivot at one end of the 
deflected fingers. They are forced outwardly by the mandrel end located 
chamfered undercuts 84. At the time of assembly, these undercuts are 
threaded in position on the central mandrel portion 79 to initiate lateral 
deflection thereby forcing the finger shaped levers 82 radially outwardly. 
The passage through the mandrel 79 communicates to the interior of the 
sleeve 80 by suitable ports 85. The ports 85 are included so that fluid in 
the mandrel passage can fill the interior of the sleeve 80. This fluid is 
under pressure. The actual pressure noted will be discussed in 
relationship to the pressure balance that is achieve in the system 
hereinafter. 
There is no leakage from the interior of the sleeve 80. The stiff ring 81 
supports an inwardly directed seal member which is preferably an O-ring 
which holds against the pressure within the sleeve so that expansion and 
leakage does not occur. Even when there is a pressure build up within the 
sleeve, there is essentially no leakage. The stiff ring 81 is preferably 
bonded to or otherwise adhesively joined with the upper end of the sleeve 
so that there is no leakage at this interface. The same is also true at 
the lower end so that symmetrical construction prevents leakage at either 
end. 
The mandrel 79 is one of the multiple pieces as mentioned above and extends 
downwardly to an enlarged mandrel portion 86, and this in turn connects 
with an elongate hollow cylindrical member 87. This defines a fluid 
receiving chamber 88 shown at the top of FIG. 3. This chamber is 
sufficiently large to match, or even more than match, the volume within 
the sleeve 80 for reasons to be defined. The chamber 88 is closed by a 
floating piston. The piston 89 can move upwardly and downwardly within the 
chamber. The piston 89 is constructed with an axial passage 90 opening 
therethrough. There is an axial fluid flow path through the passage 90. 
Fluid flow from this passage must dislodge the check valve 91 from its 
seat. This valve has the preferred form of a sphere which is forced 
against the seat by a resilient spring 92. The spring forces the check 
valve to a closed condition unless pressure overcomes the check valve 
spring. Again, the relative pressure on the check valve will be discussed 
below in detail. The piston 89 is floating in the sense that it can move 
upwardly or downwardly. The initial filling of the system with a 
particular fluid will be descried so that the piston is forced to a 
particular location. Pressure balance is achieved within the system while 
the piston 89 is subject to movement along the cylindrical chamber 88. 
The fluid flow path extends downwardly from the passage 90 into the sub 93 
and flows to the exterior through the laterally directed ports 94. 
Therebelow, weight bars or sinkers are included. The sub 93 supports a 
pivot 95 which provides one degree of freedom, and there is another degree 
of freedom at the pivot 96 therebelow. The two pivots or degrees of 
freedom are at right angles. This permits the weight bars to snake through 
the drill pipe even though they may be several feet in length. This type 
of U-joint, referring to the pivots 95 and 96, is repeated at various 
locations along the weight bars. Conveniently, the weight bars are 
assembled by positioning the pins 95 and 96 in the matching passage as 
indicated in this construction. One or more weight bars can be included. 
The range of angular deflection at an individual pivot is almost ninety 
degrees; referring to the pin 96, it is at right angles with respect to 
the other pin so that the weight bar therebelow is able to pivot 
substantially to the left or right and at right angles. 
MODE OF OPERATION 
As a preliminary matter before use, the piston 89 is located at a 
particular location by a support stand inserted from below the piston. It 
is preferably located at some mid location so that it will not bottom out 
at either end of possible travel. An incompressible fluid which is 
preferably water is pumped into the apparatus. Air is voided by pressing 
the check valve 75 downwardly from above. Only slight pressure is 
required, and it should be sufficient to dislodge the ball downwardly with 
a rod to enable filling. Water is placed in the tool by inverting the tool 
with surplus water forced out through the check valve 75. The equipment 
thus is filled with water, and is preferably filled while in the upright 
inverted position to permit air bubbles to escape. It is preferably filled 
to the extent that the sleeve 80 is expanded outwardly to its normal 
diameter. In summary, fluid filling is the initial step accomplished 
before use. 
When it is time to remove the drill stem from a well as typically 
occasioned on changing drill bits, the wiping apparatus 70 is dropped into 
the drill string from the top end at the rig floor. It will fall in the 
drill string until it encounters mud. It assumes a buoyant position 
floating on the top of the column of drilling fluid. In this posture, the 
sleeve 80 expands to fill the pipe cross-sectional area and to provide a 
wiping surface. Assume for the moment that there is no drilling fluid 
above the sleeve 80 and wiping occurs as it moves relatively downwardly 
along the stand of pipe moving upwardly. Wiping occurs in the routine 
fashion. As the wiping forces the drilling fluid downwardly, the drill 
pipe can be pulled upwardly. Eventually, the wiping apparatus 70 will 
encounter an internal upset. When an upset relatively approaches the 
sleeve 80, the shoulder at the end of the upset will encounter the gently 
sloping external face of the sleeve 80 and begin compression hereof. The 
sleeve is compressed as the wiping apparatus 70 is pulled through the 
region where the internal upset is located. This is accomplished with 
substantial compression. Prior to the upset, the sleeve was full gauge, 
being held in that position by water on the interior. The water, however, 
is forced out of the sleeve 80. Water is then forced into the passage 73. 
It cannot flow upwardly because it kept in the passage by the topmost 
check valve 75. It flows downwardly, creating expansion room by forcing 
the piston 89 downwardly in the chamber 88. The spring 92 in the bottom 
check valve is sufficiently strong that the piston will move before the 
check valve will open. This enables the piston to move to accomodate an 
increase in the chamber 88 volume occasioned by the reduction in diameter 
of the sleeve 80. In other words, the chamber 88 becomes longer as the 
piston moves downwardly; the piston 89 moves upwardly when the sleeve 
expands. The piston 89 is opposed by the prevailing pressure in the 
drilling fluid. The piston 89 is forced upwardly in response to prevailing 
pressure to force the incompressible water out of the cylinder 88 back 
into the expandable sleeve 80 whereby the sleeve maintains its wiping 
contact during and after the upset. In other words, this occurs even after 
the upset has relatively moved upwardly past the sleeve so that the lower 
side of the upset and the pipe just below the upset is likewise 
successfully wiped. Continual sleeve contraction and expansion is 
permitted by this arrangement. 
Another important factor in the operation of the present device is the 
ability to pump through the device. In the unlikely event that a pressure 
surge comes from a blowout below which would otherwise force mud to flow 
upwardly through the drill string, the mud flow will tend to lift the 
present apparatus somewhat. Drilling fluid, however, cannot force its way 
upwardly through the central passage because the check valves are arranged 
to prevent this. If there is an upward surge on the exterior of the wiping 
apparatus 70, the entire assembly might be carried upwardly until the 
expanded sleeve 80 encounters the internal upset at the pipe joint 
thereabove. When this occurs, the present apparatus will be slowed but may 
continue to be lifted upwardly. It will, however, serve as a brake on 
rapid upward flow as might occur with a blowout. Indeed, a blowout is 
retarded, even prevented. This, of course, depends on the relative 
pressure drive behind the blowout. 
Another important factor in the present apparatus is the ability to pump 
from above. Assume that a blowout has occurred, but that it is only a 
partial blowout in that the wiping apparatus has been lifted somewhat from 
an initial position along the drill stem. If fluid flow is established by 
reconnecting the mud line to the top end of the drill string, then fluid 
can be forced downwardly. It can flow through the passage 73 and dislodge 
the check valves which are biased to permit downwardly flow. That is, a 
slug of heavy weight material can be pumped through the present apparatus 
to reestablish control over the blowing well. At any time, the present 
apparatus can be retrieved by grappling the top end of it with a fishing 
tool such as an overshot which is used to retrieve the present apparatus. 
While the foregoing is directed to the preferred embodiment, the scope 
thereof is determined by the claims which follow.