U.S. patent number 3,713,499 [Application Number 05/170,709] was granted by the patent office on 1973-01-30 for method and apparatus for treating drilling mud.
This patent grant is currently assigned to Gulf Research & Development Company. Invention is credited to Raymond L. Arscott, Eber W. Gaylord, Ernest A. Mori, Richard A. Morris.
United States Patent |
3,713,499 |
Arscott , et al. |
January 30, 1973 |
METHOD AND APPARATUS FOR TREATING DRILLING MUD
Abstract
A method for treating drilling mud discharged from a well in an
abrasive jet drilling process using ferrous abrasives to
recondition the drilling mud for reuse in which the drilling mud is
passed over a shale shaker to remove oversized cuttings and is then
delivered into a magnetic separator in which the abrasive particles
are separated from the major portion of the drilling mud. The
ferrous abrasive particles from the separator are further cleaned
of drilling mud in a centrifugal cleaner and dried. The dried
abrasive particles are screened to remove broken abrasives, and the
resultant sized abrasive particles are stored in a dry condition in
a hopper from which they are introduced into drilling mud at a
controlled rate and recirculated through the abrasive jet drilling
process.
Inventors: |
Arscott; Raymond L.
(Pittsburgh, PA), Gaylord; Eber W. (Pittsburgh, PA),
Mori; Ernest A. (Glenshaw, PA), Morris; Richard A.
(Monroeville, PA) |
Assignee: |
Gulf Research & Development
Company (Pittsburgh, PA)
|
Family
ID: |
22620945 |
Appl.
No.: |
05/170,709 |
Filed: |
August 11, 1971 |
Current U.S.
Class: |
175/66;
175/206 |
Current CPC
Class: |
E21B
21/066 (20130101) |
Current International
Class: |
E21B
21/06 (20060101); E21B 21/00 (20060101); E21b
007/18 () |
Field of
Search: |
;175/54,66,206 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Claims
We claim:
1. A method of treating ferrous abrasive laden drilling mud
discharged from a well for recirculation in an abrasive jet
drilling process comprising screening oversize cuttings from the
drilling mud, dividing the screened drilling mud into a
ferrous-abrasive-rich stream and a drilling mud stream
substantially devoid of ferrous abrasives, cleaning the ferrous
abrasives in the ferrous-abrasive-rich stream to reduce the
concentration of drilling mud with the ferrous abrasives to below
about 5 percent by weight, drying the clean ferrous abrasives, and
mixing the dried ferrous abrasive with drilling mud liquids at a
controlled rate to form a drilling mud for recirculating through
the well.
2. A method as set forth in claim 1 in which the division of the
screened drilling mud is accomplished by magnetically separating
ferrous abrasives from the drilling mud.
3. A method a set forth in claim 1 in which the division of the
screened drilling mud is accomplished by magnetically separating
ferrous abrasives from drilling mud and the reduction of the
concentration of drilling mud on the ferrous abrasives is
accomplished by centrifugally cleaning the drilling mud from the
ferrous abrasive particles.
4. A method as set forth in claim 3 in which the dried ferrous
abrasives are screened to remove particles larger than 20 mesh and
particles smaller than 80 mesh before mixing with drilling mud
liquids.
5. A method as set forth in claim 3 in which drilling mud
discharged from the centrifugal cleaning is passed through a
cyclone separator to separate abrasive particles therefrom and the
abrasive particles from the separator are dried with abrasive
particles delivered from the centrifugal cleaner directly to the
drier.
6. A method as set forth in claim 3 in which drilling mud
discharged during centrifugal cleaning of the magnetically
separated ferrous abrasive particles is recycled through the
magnetic separator.
7. A method as set forth in claim 1 in which the stream of drilling
mud substantially devoid of abrasive particles that was divided
from the screened drilling mud is passed through a cyclone
separator to remove fine particles therefrom and form a clean
drilling mud, and the cleaned drilling mud is mixed with dried
abrasive particles.
8. A method as set forth in claim 7 in which the cleaned drilling
mud is cooled and screened, and the cooled and screened drilling
mud is mixed with the dried ferrous abrasive particles to form the
abrasive laden drilling mud for recirculating to the well.
9. A method of treating ferrous abrasive laden drilling mud
discharged from a well for recirculation in an abrasive jet
drilling process comprising screening oversize cuttings from the
drilling mud, magnetically separating ferrous abrasives from the
screened drilling mud, cleaning the magnetically separated ferrous
abrasives to reduce the concentration of drilling mud thereon to
less than 5 percent by weight of the ferrous abrasives, drying the
cleaned ferrous abrasives, screening the dried ferrous abrasives to
remove oversize and undersize particles, passing drilling mud from
the magnetic separation through a cyclone separator to remove solid
particles therefrom and form a clean drilling liquid, cooling the
clean drilling liquid, blending screened dried ferrous abrasives
with a first portion of the cleaned drilling liquid to form a
slurry containing 15 - 50 percent abrasive particles, increasing
the pressure on the slurry to 5,000 - 20,000 p.s.i., pumping a
second portion of the clean drilling liquid to a pressure of 5,000
- 20,000 p.s.i., mixing the clean drilling liquid and the slurry at
a pressure of 5,000 - 20,000 p.s.i. to form a drilling mud for
recirculating to the well.
10. Apparatus for treating ferrous abrasive laden drilling mud
discharged from a well in an abrasive jet drilling process to form
an abrasive laden drilling mud for recirculation through the well
comprising means for separating abrasive particles from the
drilling mud discharged from the well, a cleaner for removing
drilling mud from the separated abrasive particles, means for
transporting the ferrous abrasive particles to the cleaner, a drier
for drying the clean abrasive particles, means for delivering the
cleaned abrasive particles to the drier, and means for mixing dried
abrasive particles at a controlled rate into drilling mud liquids
to form an abrasive laden drilling mud for recirculating to the
well.
11. Apparatus as set forth in claim 10 in which the means for
separating is a magnetic separator.
12. Apparatus as set forth in claim 10 in which the means for
removing drilling mud from the separated abrasive particles is a
centrifugal cleaner.
13. Apparatus for reconditioning drilling mud discharged from a
well in the abrasive jet drilling process for recirculation through
the well comprising a screen for separating oversize cuttings from
the drilling mud discharged from the well, a magnetic separator,
means for delivering screened drilling mud from the screen to the
magnetic separator, a centrifugal cleaner for removal of drilling
mud from the ferrous abrasive particles, means for delivering
ferrous abrasive particles from the magnetic separator to the
centrifugal cleaner, a drier, means for delivering ferrous abrasive
particles from the centrifugal cleaner to the drier, screening
means adapted to remove particles larger than 20 mesh and smaller
than 80 mesh from the ferrous abrasive particles, means for
delivering ferrous abrasive particles from the drier to the
screening means and from the screening means into a storage hopper,
and means for mixing dry ferrous abrasive particles from the
storage hopper at a controlled rate with drilling mud to form an
abrasive laden drilling mud for recirculating through the well.
Description
This invention relates to the drilling of wells and more
particularly to the treatment of drilling mud used in abrasive jet
drilling to condition the mud for recirculation in the drilling
operation.
In the rotary method for drilling wells, a drilling mud is
circulated down through a rotating drill pipe and discharged from a
drill bit at the lower end of the drill pipe. The rate of
circulation of the drilling mud is such that the drilling mud picks
up the cuttings cut by the drill bit from the drilled formation and
carries them upwardly through the annulus surrounding the drill
pipe to the surface. The drilling mud is treated at the surface to
remove the cuttings and is recirculated down the well for further
drilling. The drilling mud serves other purposes than transporting
cuttings from the borehole. A principal purpose is to provide a
hydraulic pressure in the well that exceeds the pressure of liquids
in formations drilled.
In an abrasive jet drilling process recently developed to drill
hard formations, abrasive particles are suspended in a drilling mud
and pumped down a rotating drill pipe in a manner similar to that
used in the conventional rotary drilling. The abrasive laden
drilling mud is discharged at an extremely high velocity, above
about 650 ft. per second, through nozzles in a drill bit at the
lower end of the drill pipe and against the bottom of the borehole
to cut grooves in the bottom that facilitate mechanically breaking
rock extending upwardly between the grooves. Virtually all
penetration of the formations drilled is accomplished in the
abrasive jet drilling process by the high velocity jet streams. The
circulation of the abrasive laden liquid up the annulus surrounding
the drill pipe carries the cuttings to the surface where the
drilling mud is treated to remove cuttings and condition the mud
for reuse in the drilling.
Ferrous abrasive particles, which may be either steel or cast iron
grit or shot, have been found to be highly effective in the
abrasive jet drilling process. Steel shot is the preferred
abrasive. The size of the abrasive particles depends on the
diameter of the throat of the nozzles in the drill bit and is
usually in the range of 18 - 80 mesh in the U. S. Sieve Series. A
narrow range of particle size, for example, 30 - 50 mesh for use
with a nozzle throat diameter of one-eighth inch, is
advantageous.
Treatment of the drilling mud used in abrasive jet drilling is
substantially more difficult than the treatment of conventional
drilling muds. In addition to causing severe erosion of equipment,
the abrasive particles increase substantially the concentration of
solids in the drilling mud and thereby make more difficult pumping
the drilling mud from one vessel to another. Because of the large
size and high density of the abrasive particles relative to
conventional drilling mud solids, the abrasive particles settle
from the drilling mud rapidly unless the drilling mud is kept
moving at a high velocity. Moreover, it is necessary to remove from
the drilling mud broken abrasive particles as well as oversize and
undersize cuttings to maintain maximum drilling rates.
This invention resides in a method and apparatus for treating
ferrous abrasive laden drilling mud discharged from the well for
use in the abrasive jet drilling process in which the drilling mud
discharged from the well is screened to remove large cuttings, the
ferrous abrasive particles are separated from the screened drilling
mud in a magnetic separator, the abrasive particles are cleaned of
adhering drilling mud, the cleaned abrasive particles are dried,
and then are classified while in a dry condition to separate
oversized and undersized particles from the abrasive. The abrasive
particles are stored in a dry condition and fed at an accurately
controlled rate into a blender for admixture with clean
abrasive-free liquid to form a drilling mud and the resulting
drilling mud is pumped at the high pressure needed for circulation
down the well and imparting the necessary very high velocity to the
liquid discharged from the drill bit nozzles.
The single FIGURE of the drawings is a diagrammatic flow sheet for
treating abrasive laden drilling mud by this invention.
Referring to the drawing, a well 10 is indicated diagrammatically
with a kelly 12 extending downwardly through the upper end of the
well for connection to a drill pipe within the well. A mud return
line 14 from well 10 discharges mud with suspended cuttings into a
rotating ditch 16 which delivers the drilling mud onto a shale
shaker 18. Shale shaker 18 is a vibrating screen which can be 5 to
20 mesh. The size of the openings in the shale shaker will depend
on the size of the abrasive and type of drilling mud. A drilling
mud that can be used in the abrasive jet process is described in U.
S. Pat. No. 3,508,621 and typically contains 1 - 6 percent clay,
0.5 - 5 percent plant fibers, and 1 - 20 percent steel shot, but
this invention can be used advantageously in treating any drilling
mud containing ferrous abrasives. The ferrous abrasives can be
either shot or grit.
Oversize cuttings are rejected by the shale shaker and discarded
from the system through a waste line 20. The drilling mud
containing solid particles that pass through the screen on the
shale shaker is delivered through line 22 into a magnetic separator
24 in which ferrous abrasive particles are separated from liquid
and the other solid constituents of the drilling mud. Magnetic
separator 24 includes a steel drum rotatably suspended in a tank
into which drilling mud is delivered from the shale shaker.
Abrasive particles adhere to the drum and are carried out of the
tank and separated from the drum. Ferrous abrasives are discharged
from separator 24 through line 26 as a concentrated slurry. The
major portion of the liquid of the drilling mud and the other
drilling mud solids are discharged from separator 24 through line
28 as a dirty liquid stream substantially free of ferrous
abrasives. The slurry is pumped by a suitable pump 30, which may be
a Moyno pump, to a centrifugal cleaner 32 in which further
separation of the drilling mud and ferrous abrasive occurs.
Centrifugal cleaner 32 is described and claimed in a patent
application of Eber W. Gaylord entitled Centrifugal Cleaner filed
concurrently herewith. In cleaner 32 the slurry is discharged into
a guide at the center of a rotating impeller having a plurality of
impeller blades inclined in a direction opposite the direction of
rotation of the impeller. The slurry flows from the guide onto the
inner end of the impeller blades. Abrasive particles are discharged
from the trailing edge of the impeller blades and drilling mud from
the outer end. Ferrous abrasive particles discharged from cleaner
32 are delivered through line 34 to a conveyor 36 which transports
the ferrous abrasive particles into the inlet end of rotary kiln
drier 38.
The major part of the liquid delivered into cleaner 32 with the
solids other than the ferrous abrasive particles and a small part
of the ferrous abrasives, particularly broken abrasive particles,
charged to the cleaner 32 are discharged through line 40 and pumped
by a pump 42 through line 44 into a cyclone separator 46. Ferrous
abrasive particles are discharged from the lower end of the cyclone
separator onto a screen 48 where the abrasive particles are washed
by a water stream circulated by pump 50. It is necessary
periodically to replace the water used in the washing because of
the buildup in the concentration of nonferrous solid particles.
Ferrous abrasive particles discharged from the screen 48 are
delivered through line 51 onto conveyor 36 for delivery with the
abrasive particles from separator 32 into the kiln drier 38.
The arrangement illustrated in the drawing for processing the
liquid discharged from the cleaner is one of several that can be
used. The processing of that liquid will depend on the amount of
abrasive broken in the drilling operation because broken abrasive
particles tend to remain in the drilling mud and a large part of
them are discharged from the cleaner with the drilling mud. If only
a small part of the abrasives are broken, the drilling mud can be
returned through a line 43 to the magnetic separator 24. Drilling
mud would then be bled from the system periodically through line 41
to prevent a buildup of broken abrasives in the system. Another
alternative is to deliver the drilling mud discharged from the
cleaner to a second magnetic separator to recover the small amount
of abrasives not separated from the drilling mud in the
cleaner.
Hot gases pass through the kiln drier 38 countercurrent to the
ferrous abrasive particles to evaporate moisture from the ferrous
abrasive particles. Hot gases circulated through the drier to
provide the heat necessary to evaporate the water can be obtained
from a suitable source such as a burner in the drier or the exhaust
from the motors used to drive the high pressure pumps used to
circulate the abrasive laden liquid down the well. Dry ferrous
abrasive particles discharged from the kiln 38 are delivered
through line 52 to an elevator 54 which lifts the shot particles
and discharges them onto the upper surface of a screen 56. The
oversized and undersized shot particles are rejected from the
system through lines 58 and 60 respectively and the dried and sized
shot particles are delivered through line 62 into a suitable
storage hopper 61. Make-up abrasive is added to the system at 53 to
replace abrasive removed from the system as fines.
Dirty liquid from the separator 24 is delivered through line 28
into compartment 62A of a mud pit 62 divided into compartments 62A,
62B, and 62C by suitable partitions. A pump 64 withdraws dirty
liquid through line 66 from compartment 62A and delivers it into
cyclone separators 68. The underflow from the cyclone separators,
which contains cuttings and a small amount of abrasive particles,
is discharged from the system through line 70. Clean liquid is
discharged from cyclone separators 68 as an overhead stream and is
delivered through line 72 into clean-liquid compartment 62B. The
term clean liquid refers to the liquid component of the drilling
mud including suspended clay solids but from which abrasive and
cuttings have been removed. A pump 74 withdraws clean liquid from
compartment 62B through line 76 and delivers a part of the clean
liquid into line 78 to adjust the volume of liquid passing through
line 44 for most efficient operation of cyclone separator 46.
Another portion of the clean liquid is delivered through line 80
into compartment 62A to maintain a constant supply of liquid as
needed for most efficient operation of cyclone separators 68. A
third portion of the clean liquid is returned through line 81 into
clean liquid compartment 62B. Makeup chemicals are added to the
stream in line 81 from a suitable hopper 82 as required to maintain
the desired drilling mud properties.
Clean liquid in compartment 62B is withdrawn through a line 84 by a
pump 86 and passed through a heat exchanger 88 to remove heat
imparted to the drilling mud during the jet drilling operation. A
portion of the cooled clean liquid is returned to compartment 62B
through line 90 for recycling through the heat exchanger. Another
portion of the clean liquid is discharged through line 92 onto a
vibrating screen 94 to remove any oversized solid particles that
might have fallen into the liquid. The cleaned, cooled, and
screened liquid is delivered from screen 94 through line 96 into
compartment 62C. Compartment 62C should be covered to prevent
contamination of the cleaned and cooled liquid.
A pump 98 withdraws clean liquid from compartment 62C through line
100 and delivers it through lines 102 and 104 into a blender 106
equipped with mechanically driven paddles to obtain homogenity and
to keep the solids suspended in the liquid. Cleaned, dried, and
screened ferrous abrasive is discharged from hopper 61 into a weigh
feeder 108 which delivers the ferrous abrasive at a controlled rate
into the blender 106. A concentrated (15 - 50 percent by bulk
volume) suspension of ferrous shot in clean liquid is withdrawn
from the blender 106 and delivered at a low pressure of about 100
lbs. per square inch by pump 110 to a high pressure injector 112.
Pump 110 is preferably a Moyno type pump. Injector 112 is a plunger
type pump with a long stroke and operating at a low number of
strokes per minute to increase the pressure on the concentrated
suspension of ferrous abrasive in clean drilling mud to 5,000 -
20,000 p.s.i. and discharges the suspension into a line 114 for
delivery to the well 10. The major portion of the clean drilling
mud in line 102 is delivered through line 116 to a battery of high
pressure pumps, indicated generally by reference numeral 118,
suitable for handling a clean liquid and discharging the liquid at
a pressure of approximately 5,000 - 20,000 p.s.i. The clean liquid
is delivered through line 120 into line 114 for mixing with the
concentrated suspension of ferrous abrasive particles to form the
drilling mud used in the abrasive jet drilling process. Drilling
mud is returned to kelly 12 and then to well 10 through line
114.
In a typical apparatus utilizing this invention, magnetic separator
24 will separate substantially all, for example 99 percent, of the
ferrous abrasives from the drilling mud delivered to the separator
and discharge through line 26 that ferrous abrasive in a slurry in
which the ferrous abrasive constitutes approximately 50 percent
bulk volume of the slurry. About 85 percent of the drilling mud
liquids delivered to magnetic separator 24 are normally discharged
from the separator through line 28.
The cleaner 32 which utilizes large dynamic forces to multiply
differences in mobility of the abrasive particles and drilling mud
over the impeller blades to separate the ferrous abrasives from the
drilling mud liquids and very fine solids discharges through line
34 about 90 - 95 percent of the abrasives charged to the cleaner in
a stream containing 1 - 4 percent by weight of drilling mud
liquids. Approximately 90 percent of the drilling mud liquids
delivered to the cleaner 32 is discharged from the cleaner through
line 40 and delivered into cyclone separators 46. The cyclone
separators 46, which may be for example 4-inch cones, complete the
removal of ferrous abrasives and about 50 percent of the rock
cuttings from the drilling mud introduced into the cones. The
ferrous abrasives discharged from the screen 48 may constitute
about 6 - 7 percent of the abrasives originally charged to the
magnetic separator and contain about 10 percent by weight drilling
mud liquids. The amount of ferrous abrasives discharged from the
screen 48 will depend upon the extent to which the abrasive is
broken in the drilling operation and the operation of the cleaner
32.
The cyclone separators 68 which may be 6-inch cones remove
substantially all ferrous abrasives from the dirty liquid charged
to those separators and about 95 percent of the rock cuttings. Only
very finely divided rock particles and clay solids remain in the
clean liquid discharged overhead from separators 68.
It is essential to the efficient operation of the abrasive jet
drilling process that solid particles, including broken abrasive
particles, other than the ferrous abrasives of the desired particle
size be removed from the drilling mud before the drilling mud is
recycled through the well. While abrasive particles having a size
of 20 - 50 mesh are preferred, that range may extend to particles
as small as 80 mesh. Separation of broken abrasive particles and
other solids smaller than 80 mesh from the unbroken abrasive
particles by means of screens while the abrasive particles are
suspended in drilling mud is not feasible because of the low
capacity of screens for making that separation. If the abrasive
particles are suspended in drilling mud of the type disclosed in U.
S. Pat. No. 3,508,621 which contains an appreciable quantity of
plant fibers, the fibers in the drilling mud blind the screens and
make separation by screening virtually impossible.
In the treatment of the drilling mud according to this invention,
use is made of the differences in magnetic properties of the
abrasive particles and other mud constituents and the differences
in mobility of the abrasive particles to make the separation of
abrasive particles from other drilling mud constituents. The
magnetic separator, additionally, has the important advantage that
drilling mud can merely drain from the shale shaker into the tank
of the magnetic separator. In contrast, cyclone separators require
pumps to deliver the drilling mud into the cyclone separator at a
high velocity to make the desired separation, and such pumps are
subjected to severe erosion. In the process for treating the
drilling mud described herein, substantially all of the abrasive
particles are removed from the drilling mud before the drilling mud
must be pumped for delivery at a high velocity into a cyclone
separator.
Drying of the ferrous abrasive particles, particularly if the
ferrous abrasive is used with the drilling mud described in U. S.
Pat. No. 3,508,621, is necessary to make an effIcient separation of
broken and unbroken ferrous abrasive particles; however, the
ferrous abrasive discharged from the magnetic separator cannot be
dried effectively in a kiln drier or fluidized bed type drier.
Twenty-five, or even more, percent by weight of the abrasive laden
slurry from the magnetic separator is drilling mud. If that slurry
is charged directly to the drier, the abrasive particles are bonded
together in the drier. It is necessary to reduce the amount of
drilling mud charged to the drier with the abrasive to below about
5 percent by weight of abrasive particles. The centrifugal cleaner
32 removes approximately 90 percent of the drilling mud from the
abrasive particles charged to the cleaner and discharges a stream
containing as little as 1 - 2 percent drilling mud for delivery to
the drier. The clean abrasive particles discharged from the cleaner
can be readily dried without clumping in either a kiln type or
fluidized bed type drier. The reduced moisture content of the
abrasive particles has an additional important advantage of
reducing the heat required by the drier.
The dried abrasive particles can readily be separated from broken
abrasive particles by screening. A five stack screen has been found
to be advantageous in giving a compact structure of adequate
capacity. Dried abrasives can be stored without corroding and are
easily charged at an accurately controlled weight to a blender for
mixing with clean drilling mud to form a suspension of uniform
concentration of abrasive particles in drilling mud for
recirculating to the well.
* * * * *