U.S. patent number 3,795,282 [Application Number 05/285,142] was granted by the patent office on 1974-03-05 for well flushing method.
This patent grant is currently assigned to Cities Service Oil Company. Invention is credited to Don L. Oliver.
United States Patent |
3,795,282 |
Oliver |
March 5, 1974 |
WELL FLUSHING METHOD
Abstract
Method of flushing debris from a well wherein an upper section
of the well hole has a significantly larger diameter than the lower
end. Drilling fluid is normally supplied through a drilling bit,
but additional fluid can also be supplied from another source so
that the total amount of fluid being pumped to the hole is
substantially in excess of that which can be supplied through the
bit alone. Upward thrust of drilling fluid in the larger, upper
section of the hole is significantly increased, thus overcoming the
settling rate of debris therein so that it becomes entrained in the
circulated drilling fluid and is hence discharged from the top of
the hole while suspended in the fluid.
Inventors: |
Oliver; Don L. (Houston,
TX) |
Assignee: |
Cities Service Oil Company
(Tulsa, OK)
|
Family
ID: |
23092917 |
Appl.
No.: |
05/285,142 |
Filed: |
August 31, 1972 |
Current U.S.
Class: |
175/65; 175/317;
175/237 |
Current CPC
Class: |
E21B
21/00 (20130101); E21B 21/103 (20130101) |
Current International
Class: |
E21B
21/10 (20060101); E21B 21/00 (20060101); E21b
007/00 () |
Field of
Search: |
;166/99,222,223,311,312
;175/25,38,60,65,72,237,243,308,320,324 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brown; David H.
Attorney, Agent or Firm: Gunn; Elton F.
Claims
What is claimed is:
1. In the drilling of a well wherein an upper section of the well
hole has a significantly larger diameter than the lower end and a
drilling fluid is circulated from the bottom to the top of the well
hole by injection through a drilling bit, the method of flushing
debris out of the well hole which has a settling rate that
overcomes the upward thrust of drilling fluid injected through the
drilling bit and which passes through the upper section of the hole
having a larger diameter, said method comprising introducing
additional drilling fluid into the hole from a source other than
the drilling bit and hence in a quantity greater than can be
supplied through the bit alone, raising the upward thrust of fluid
in the upper section of the hole having a larger diameter,
overcoming the settling rate of debris therein, discharging debris
from the upper section of the hole while entrained in the fluid
introduced into the well hole, and preventing the falling of debris
into the lower end of the well hole.
2. A method as in claim 1 wherein fluid is introduced from a fluid
channel through the wall of the drilling string, said channel being
located above the drilling bit.
3. A method as in claim 1 wherein the supply of additional fluid is
shut off during drilling and is turned on prior to raising the
drilling bit into the larger, upper portion of the hole.
4. A method as in claim 1 wherein fluid from the source other than
the bit is introduced into the well hole near the bottom of the
upper section having a larger diameter than the lower section.
Description
BACKGROUND OF THE INVENTION
This invention pertains to the drilling of wells wherein a drilling
fluid is pumped into the well hole from a drilling bit and is then
circulated up through the hole and out at the top. More
particularly, this invention pertains to the flushing of rubble,
debris, small pieces of junk, etc. from a well hole having a
diameter in an upper section which is significantly larger than the
diameter of a shallower portion.
In the drilling of some wells the hole is first put down at one
diameter and is then drilled to one or more smaller diameters until
a desired total depth is reached. For instance, a casing program
might comprise 30 inch casing to 100-200 feet, 101/2 inch casing to
900-1,000 feet, and 7 inch casing to several thousand feet. Open
hole drilling can also be carried out below a casing to provide an
open hole having a diameter smaller than the casing.
It has now been observed that difficulty can sometimes be
en-countered with build up in the larger, upper part of the well
hole of large drill cuttings, rubble, small pieces of cement, junk,
etc.-- hereinafter referred to as debris-- which cannot be flushed
from the hole because of inadequate fluid velocity in the larger,
upper section.
More specifically, the volume of drilling fluid which is provided
to a well hole by the drilling bit is generally sufficient to
provide a fluid velocity which effectively suspends the debris so
that it can be entrained and flushed from the section of hole then
being drilled. It has been observed, however, that the resulting
drop in velocity which occurs upon entry of the fluid into an upper
section of larger diameter can be so severe as to result in
precipitation and accumulation of at least some of the entrained
objects therein, i.e., the velocity is no longer sufficient to
overcome the settling rate of the debris. Accumulation of these
undesirable materials in the upper section does not necessarily
have any detrimental effects on the drilling operation during the
time that the buildup occurs, but upon stopping mud circulation to
trip the drill pipe out of the hole, the debris can settle around
the pipe and stick to it. On the otherhand, if the pipe is
successfully pulled from the hole, settling of the accumulated
debris can result in formation of a bridge across the hole that can
require drilling through to get the drill pipe back to the bottom.
Such bridging of debris is particularly detrimental when the
drilling string is pulled from the hole so that casing can be run
back, or when open hole logging is to take place. Besides sticking
and bridging, raising the drilling bit into the upper section can
cause debris to drop into the lower end of the hole and fall to the
bottom since there is no longer any upward fluid velocity or pipe
in the hole to prevent such an occurrence. Once on the bottom, the
objects which have fallen in can seriously interfere with drilling
when the bit is again lowered, and fishing may be required before
drilling can be safely resumed.
SUMMARY OF THE INVENTION
Therefore, the principle object of this invention is to
substantially preclude or even obviate the aforementioned problems
associated with accumulation of debris, rubble and the like during
the drilling of a well hole which has an upper section of larger
diameter than the lower end.
Other objects and advantages of the invention will become apparent
from the following description and the appended claims.
When drilling a well wherein an upper section of the hole has a
significantly larger diameter than the lower end, and a drilling
fluid is circulated from the bottom to the top of the hole to
lubricate the drilling string and flush drill cuttings and debris
out of the well hole at the top, additional drilling fluid is
introduced into the lower end of the hole from still another source
other than the drilling bit. As a consequence of this increased
flow to the lower end of the hole, fluid velocity in the upper
section of larger diameter is raised to a level in excess of that
which can be effected by pumping through the bit alone, for the
rate at which fluid can be pumped through the bit is limited by the
size of the discharge orifices therein, the pressure at the point
being drilled, and the pressure at which the fluid can be made
available to the bit.
Because of frictional drag with the interior wall of the drilling
string, much if not most of the pressure supplied to the drilling
fluid at the upper end is lost by the time it reaches the bit.
Thus, by using still another opening in the drilling string so that
fluid can be introduced to the well hole from another source as
well as the drilling bit, the aforementioned difficulties are
avoided. To advantage, this additional fluid can be introduced
higher up in the string where more pumping pressure and, hence,
more fluid flow is available for getting the fluid into the well
hole. The increased upward thrust made available by supply of
additional fluid thus overcomes the settling rate of debris in the
upper section of the hole having a larger diameter, thus
maintaining the debris suspended in the drilling mud after it has
passed from the lower end of small cross section, so that flushing
of debris out of the hole without accumulation can be carried out
either continuously or at will.
The present invention can be practiced by use of a special
circulating tool located in the drilling string above the bit. The
tool can comprise a tubular body section coupled at each end to
other members of the drilling string, a passageway through the body
section which interconnects with the central passageway for fluid
which extends through the side wall of the body section from the
fluid passageway therein to the outside. The tool can further
comprise a previously set operable member inside the section which
covers the channel through the wall of the body section when set,
and which uncovers the channel when operated.
The circulating tool, along with a bit, can thus be made up with
the drilling string when it is lowered into the smaller, lower end
of a hole. Because of the channel for fluid in the wall of the
tool, more drilling fluid can be injected into the bottom of the
hole, thus raising the velocity and hence the upward thrust of the
fluid in the upper section having a larger diameter.
Using an operable member inside of the tool for covering and
uncovering the fluid channels at will, drilling fluid can be
circulated only to the bit until such time as a need is recognized
for injecting a greater volume of fluid than can be passed through
the bit, e.g., when raising the bit in the hole to a level above
the lower section of smaller diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view, partly in section, of one embodiment of the
tool of the present invention.
FIG. 2 is a side view of a weighted dart, or plunger, which can be
used to operate a slidable sleeve which covers the channels in the
wall of the body section of the tool, and also to obstruct flow of
fluid beyond the tool.
FIG. 3 is a side view, partly in section, of a slidable sleeve
which can be used as the preset operable member in the tool of FIG.
1 for covering and uncovering the channels in the wall of the body
section of the tool.
FIG. 4 is a partially fragmentary and partially sectional side view
of another embodiment of the invention wherein the sleeve
arrangements and the method of operating the sleeve are different
from that shown in FIG. 1 .
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1, the tool is generally represented at 1, and is
connected by threads to a drill pipe 2 and a drill bit 3. The tool
is thus made up with the drilling string at the time the bit is to
be lowered in he hole, and does not necessarily perform any special
function until there is need to pump drilling fluid into the hole
at a greater rate than can be supplied through the bit. The body
section 4 of the tool is attached at the upper end to a coupling 5
on the drill pipe 2. A passageway 6 for drilling fluid runs through
the body section 4 and interconnects at the upper and lower ends
with fluid passageway 6a and 6b which lead, respectively, from the
drill string 2 and into the drilling bit 3.
Channels 7 are drilled ducts which extend through the wall 8 of the
body section from the passageway 6 to the outside. When the string
is lowered into the bore hole these channels can be covered over by
an impervious axially slidable sleeve 9 frictionally held in place
in the passageway 6 by means of O-rings 10 attached to the sleeve
in recessed grooves. As drilling proceeds, drilling fluid passes
through the central passageway 6c of the sleeve which is aligned
with the other passageways 6, 6a and 6b, thus maintaining a flow of
all drilling fluid to the bit, since the channels 7 are blocked off
by the sleeve which is preset in position over the openings of the
channels before the tool and bit are lowered into the well
hole.
In FIG. 1, the sleeve 9 is thus shown in the preset position
whereby the channels 7 are covered over. The passageway 6 in the
vicinity of the sleeve is recessed for a distance in excess of the
sleeve length to permit the sliding thereof when operated and to
provide a chamber which accommodates the thickness of the sleeve
wall, the latter feature tending to preserve the diameter of the
fluid passageway 6 while also forming a shoulder 11 at the top of
the chamber which serves as an upper stop for the sleeve. The upper
edge 3a of the drill bit 3 serves as a lower stop for the
sleeve.
When it is desirable to increase the rate at which drilling fluid
is pumped into the well hole, channels 7 are then uncovered in
order to divert flow from the bit and into the hole through the
wall 8 of the body section. This can be accomplished in various
ways, and two apparatus arrangements intended for this purpose are
shown in the drawings. FIGS. 1-3 illustrate use of a weighted dart,
or plunger, which is dropped into the drilling string for
displacing the sleeve downwardly to uncover the channels 7, and
FIG. 4 illustrates use of a sleeve which normally covers the
channels 7 when the sleeve is bottomed, and which can be lifted by
wire line to uncover the channels.
Referring to FIGS. 1-3, the dart 12 is dropped into the drilling
string from the surface when it is desirable to increase the rate
at which fluid is pumped to the hole so that flushing of debris can
be continuously carried out. As soon as the dart is dropped,
pressurization of the drilling fluid can be resumed. The momentum
of the falling dart may in itself be sufficient to drive the sleeve
downward below the channels 7, but in any event both dart and
sleeve are constructed so as to form a piston which can be driven
downward by pumping pressure when engaged as shown in the
drawing.
More specifically, the sleeve 9 comprises an attached or integral
ring 13 which projects into the central passageway and is axially
aligned therewith. With the sleeve shown, the ring is machine
beveled to provide an upper tapered sealing surface 13b. The upper
part of the dart 12 is provided with a matched bevel 14, so that
when the dart and the sleeve are engaged as in FIG. 1, flow of
fluid past the sleeve is effectively obstructed. Therefore,
elevation of pumping pressure on the drilling fluid will displace
the dart and sleeve down-wardly and thus uncover the channels 7
when dart and sleeve are mated as in FIG. 1.
FIG. 4 illustrates a different arrangement wherein the sleeve is
normally bottomed against the lower stop 22a for covering of the
channels 7. When there is a need to increase the rate at which
drilling fluid is pumped to the well hole, a wire line tool is
lowered which engages a latch 15 on a rod 16 which extends inside
the sleeve from one side to the other. The sleeve is then raised
against the upper stop 11 by means of a wire line tool. A snap ring
17 which extends around the sleeve and is attached thereto in a
groove engages a latching groove 18 in the wall of the passageway
and thus holds the sleeve in an elevated position. The wire line is
then pulled loose from the sleeve and the latter remains in place
by engagement of the snap ring with the latching groove.
Should it become desirable to again cover up channels 7 once the
sleeve has been shifted to uncover them, e.g., when pumping of more
fluid to the bit is needed, the sleeve can be relocated over the
channels by an action taken at the surface. When using a sleeve and
dart arrangement as shown in FIGS. 1-3, the lower spindle 19 of the
dart is provided with a snap ring 20 attached thereto in a groove
so that upon entry of the dart into the sleeve the snap ring is
compressed by the ring 13 into its recess, thus permitting the
bevel 14 on the dart to abut the ring bevel 13b. However, when the
dart is pulled upward through the sleeve, sufficient resistance is
provided by the flat under surface of the ring to effect upward
sliding of the sleeve before the ring 20 is compressed. Once the
sleeve is topped against the upper stop 11, the snap ring can then
be compressed by upward tugging and the dart withdrawn from the
sleeve. Using an arrangement as shown in FIG. 4, the sleeve can be
lowered again to cover the channels by bumping it downward with a
weight on a wire line.
It will be appreciated that when the dart 12 is emplaced within the
sleeve 9 the sealing surfaces 13b and 14 become mated, and flow of
fluid to the bit is shut off. Since it will usually be desirable to
continue the pumping of fluid through the bit as well as through
the circulating tool, the snap ring on the plunger can be omitted.
In such cases a dart, minus the snap ring, is dropped into the
drill pipe for operation of the sleeve, and can then be raised back
out of the pipe by wire line without pulling the sleeve upwards and
over the channels. Should it be desirable to again recover the
channels, this can be accomplished with use of still another dart
having a snap ring, as previously described.
In any event the apparatus illustrated in FIGS. 1-4 can be employed
for increasing and subsequently restoring to normal the amount of
drilling fluid which can be pumped into a well hole. As previously
indicated, the channels 7 can be kept covered over by the sleeve 9
until greater flow is needed; for example, until the bit is about
to be lifted up into the upper section of the hole of larger
diameter, and can subsequently be covered over again when the
increased flow is no longer needed.
The number and size of the channels 7 in the wall of the body
section is subject to variation, but at least one is required and
should have sufficient diameter to permit pumping of a
significantly additional amount of fluid into the well hole.
FIG. 1 illustrates placement of the circulating tool directly above
the drilling bit for introducing additional drilling fluid at that
point. It will be appreciated, however, that the tool can, to
advantage, be located further up in the string for introduction of
additional fluid at a higher point, e.g., nearer the bottom of the
upper section of the hole having a larger diameter than the lower
end, for thus located, more pressure is available from the string
for introducing a greater quantity of fluid into the hole.
The present invention has been described with reference to
particular conditions, techniques, materials, apparatus
arrangements and the like, but it will be understood that still
other embodiments will become apparent which are within the spirit
and scope of the invention described in the following claims.
* * * * *