Note: Descriptions are shown in the official language in which they were submitted.
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Title: SEPARATOR FOR GASESLLIOUIDS AND SOLIDS FROM A WELL
FIELD OF THE INVENTION
The present invention is a separator for use in well drilling,
for separating rock cuttings, gas and water which are to be removed from
the bore hole. The flow from the bore hole may also contain drilling mud,
gases or foam. The present invention is more particularly intended to
separate these materials and clean them to meet environmental micro
toxicity limits.
BACKGROUND OF THE INVENTION
In surface drilling, the drill bit at one end of a drill stem is
rotated and used to bore into the earth. The drill stem and extensions
referred to as the "drill string" are typically hollow. During drilling, gas
or
fluid is pumped down through the drill stem, the gas or fluid then rises to
the surface through the annular space between the drill stem and the wall
of the hole bored by the drill stem. The hole bored by the drill stem is
referred to as the "bore hole". The gas or fluid may comprise air, nitrogen,
water, foam, drilling mud, or any other substance that is capable of
removing cuttings from the bottom of the bore hole to the surface of the
well. For example, in a conventional drilling rig, drilling mud is used to
cool the drill bit and remove cuttings from the bottom of the drill hole, by
carrying them to the surface in the annular space between the drill string
and the bore hole wall. Traditionally the drilling mud coming from the
well bore was dumped into a reserve pit. The drilling mud would then be
allowed to settle so that sediments fell to the bottom of the pit. The
drilling mud could then be pumped from the top of the pit back into the
well bore. However, because of ever increasing environmental concerns
many governments have banned the use of in-ground reserve pits.
Similarly, in the case of pure air drilling the cuttings and dust returning
from the bore hole would be allowed to dissipate in the environment,
creating a dust cloud that could extend several kilometers. and this is no
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longer environmentally acceptable.
Today, in place of in-ground reserve pits, tanks are used. The
drilling fluid is slowly circulated through the tanks to allow gases to
dissipate and solids to settle out. Recent drilling mud circulation systems
have used a vibrating screen assembly known as a "shale shaker" to
separate out the bulk of the cuttings which drop from the shaker onto the
ground or into a pit. Other methods of separation include centrifuge
separators to remove the solids while retrieving the substantial portion of
the fluid. Once passed the initial separation stage the fluid then enters one
or more rectangular open topped "mud tanks". The fluid slowly moves
through the mud tank and most of the fine solids which remain
suspended after screening or centrifuging settle out. Often the mud tank
has one or more transverse weirs or baffles, which divide the tank
chamber into compartments. The weir functions to trap settling fine
solids and thick mud, allowing "cleaned" mud to advance and to provide
tanks with mud at different concentrations. The cleaned mud is then
recycled to the well bore.
Such systems work well with relatively liquid drilling fluids.
However, in air or combined air and foam drilling systems these
separation units are not terribly efficient as the "drilling mud" contains
more air and foam than it does fluid or mud. Further, being less dense
than conventional drilling mud the output from the bore hole is at
considerably higher velocity, which can cause failures in conventional
filtration systems.
U.S. patent no. 5,718,298 discloses a separation system for use
with wells drilled using air or mist as the drilling fluid. The invention as
disclosed contains a longitudinal separator tube through which drilling
fluid from a blooie line passes. The longitudinal tube contains plurality of
openings into which water may be injected as well as a plurality of dump
gates through which drilling materials drop into a large receiving tank. A
series of angle baffles are utilized within the separator tube to reduce the
velocity of the exhaust from the blooie line. When drilling with dense
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fluids or in the case of large drill cuttings, the separator tube and its
associated outlet ports may rapidly become plugged. Should the injection
of water into the separator tube be unable to clear any obstructions, then it
may be quite difficult to clear out the separator tube.
Thus, there is a need for a drilling fluid separator that is able
to separate efficiently and cleanly drill cuttings from a gas, water and foam
drilling fluid.
BRIEF SUMMARY OF THE INVENTION
The present invention provides both a method of and an
apparatus for separating gases, fluids and solids exiting from a well, for
example an oil well, during drilling of the well. More particularly, the
invention is concerned with so-called "air drilling", where a high velocity
flow of air is used to entrain well bore cuttings. In such systems, a certain
amount of liquid is often introduced as a foam, which has a number of
advantages. Nonetheless, the essential intention is to keep the volume of
liquids in the flow down into and back from the well to a minimum.
To ensure adequate removal of cuttings, and bearing in mind
the lower density of gases, high velocities and flow rates have to be used.
In turn, where foam is used, this means that large volumes of foam are
vented from the well. Frequently, this presents a significant disposal
problem.
Accordingly, the present invention provides a method and
apparatus intended to, sequentially;
break down the foam, to separate gases from the liquids;
separately vent the gases and pass the liquids and entrained
solids on for further processing;
separate the solids from the liquids, preferably by way of a
shale shaker and a centrifuge;
as required, chemically treat the liquid to promote
flocculation of smaller particles, to enable their separation from the liquid;
re-use recovered liquid, or after checking to meet local toxicity
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requirements, dispose of liquid as permitted by local regulations.
For this purpose, the present invention provides an
apparatus including a first chamber with a device for breaking down the
foam and separating the gases and liquids. This is preferably in the form of
a vortex tube cluster, which generates centrifugal forces sufficiently to
break down the foam. The gas then exits from the top and the liquids and
solids from the bottom. The liquids are then withdrawn and passed
through a shale shaker, where larger cuttings or shale are separated. The
liquids and finer particles then drop down into a second compartment.
From the second compartment, liquids and fines are withdrawn and
separated in a centrifuge. The cleaner liquid from the centrifuge is passed
to a third compartment and the fines rejected. In a fourth compartment, a
flocculation agent resides, which can be circulated through the centrifuge
as required to cause flocculation of any remaining fines.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will now be
made, by way of example, to the accompanying drawings which show a
preferred embodiment of the present invention and in which:
Figure 1 is a schematic illustrating the well bore, the
separator, and a line connecting the well bore to the separator;
Figure 2 is a side view of the separator;
Figure 3 is a perspective view of a portion of a first
compartment of the separator;
Figure 4 is a perspective view of a mud gun within the first
compartment;
Figure 5 is a top plan view of the separator;
Figure 6 is an end view of the separator;
Figure 7 is a perspective view of an mechanism to aid in the
alignment of a degasser with the line connecting the well bore to the
separator;
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Figure 8 is a perspective view of posterior alignment
mechanism designed to function in cooperation with the anterior
alignment mechanism of figure 7; and
Figure 9 is a perspective view of an adaptor used to connect
the line from the well bore to the separator.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring first to Figure 1, a schematic view of the preferred
embodiment of the apparatus is shown generally as 10. The principal
components of the apparatus consist of a line 12 and a separator 14. The
line 12 connects the well head 15 at the drilling rig, (shown generally as
16), to the separator 14. The line 12 is commonly known as a "blooie" line
and is designated as such in this specification, including the claims. The
drilling rig 16 contains a rotatable drill string 18 which extends into the
well bore 20 from the well head 15. At the end of the drill string 18 in the
well bore 20 is mounted a drill bit 24. Drilling fluid 26 is pumped through
the drill string 18 and out of the bottom of the drill bit 24. "Drilling
fluid"
may comprise air, gases, foam, water, oils, drilling mud or a mixture of
different fluids. The drilling fluid 26 then returns to the surface through
the annular space 22 between the drill string 18 and the well bore 20. The
drilling fluid 26 then exits the drilling rig 16 through the blooie line 12,
ultimately entering the separator 14. The blooie line 12 contains an impact
device, commonly referred to as a "dead head" 19 which includes a
plurality of impact plates 28. The exposed face or end of each impact plate
28 is hardened by welding a bead of suitable hard steel alloy or by using
other known hardening means to prevent wear of the plates 28.
As is detailed below, the function of the dead head 19 is to
absorb the momentum and energy from a high velocity gas stream and in
particular, the momentum of solid particles. For this purpose, the line 12
can expand at the dead head 19 to have a larger diameter downstream.
This in turn gives a lower downstream velocity. Upstream from the dead
head 19, there is a deduster 30. The deduster 30 is a short length of pipe
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with an annular chamber around it, provided with a port for connection
to a water supply. Inside the deduster 30, there are a series of inlet ports
or
holes, causing water to be sprayed radially into the gas flow. This serves to
wet dust and other solid particles, promoting later separation of solids
from the gas flow. For air drilling, approximately one cubic meter of water
per minute is injected into deduster 30. For foam applications, three cubic
meters per minute would be injected. Alternatively, steam could be
injected upstream of a degasser 40 in the separator 14. As with the
injection of water, steam has a dampening affect and it reduces the
possibilities of explosions. Additionally, nitrogen could be injected with
steam or water to reduce explosion risk.
The blooie line 12 also contains intake ports 32 and 36. The
purpose of these intake ports is to inject water into the blooie line as
detailed below. In the case of pure air drilling, water injected at intake
port
32 serves to add liquid to the incoming dust, which aids in reducing the
wear to the impact plates 28, and liquifies the drilling fluid 26 before it
enters the separator 14. Without the use of the intake port 32 and deduster
30, dust carry over in the gas from the Vortex Cluster will occur, i.e. dust
will not be absorbed by water in the separator, but will be vented from the
separator with the gas flow. In the case of foam drilling, the water serves
to saturate the foam with water, so that the additional mass and density
breaks down the foam when it enters the Vortex Cluster. Intake port 34 is
an air bypass inlet, used to divert air away from the drill pipe when a drill
pipe connection is made while drilling.
Referring now to Figure 2, which is a side view of the
separator 14. The separator 14 comprises a series of compartments through
which the drilling fluid 26 is circulated and filtered. A first compartment
48, a second compartment 52 and a third compartment 96 have connecting
gates 112 which when opened allow fluid to flow between the upper levels
of the compartments. The degasser 40 is mounted above and extends into
the first compartment so as to be adjustable (Figure 7 and Figure 8). The
degasser 40 separates the gases in the drilling fluid from the solids and
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liquids. The degasser 40 in this embodiment is a Vortex Cluster separator
manufactured by Porta-Test International Inc.. Essentially this device
imparts a strong swirl component to the fluid flow, creating high G forces
which promote separation of gases from the liquids and solids, and also
tending to break down any foam. The gases are vented upwardly and out
to a flare pit in known manner (not shown) through a flare pit exit 42.
The degasser 40 has an upper housing 43. The upper housing
43 has a top which has been modified in the preferred embodiment from a
flat top to a circular dome 44. It was found, that when flaring off gas,
pressure would build in the housing 43, and pressure surges could arise,
causing the original flat top to momentarily lift. The dome 44 is able to
handle the pressure without lifting.
The solids and liquids flow down a set of drop tubes 46 and
fall to the bottom of the first compartment 48. The number of drop tubes
46 descending from the degasser 40 is dependant upon the flow rate. For
foam, four tubes is adequate to maintain a good velocity for the foam. The
degasser 40 as provided by the manufacturer originally had plates at the
bottom of the drop tubes 46. The plates were intended to limit the vertical
extent of the air vortex or cone, and prevent it from extending out of the
bottom of the cluster. However, it was found that the plates could become
clogged with large cuttings. The plates were subsequently removed, and it
is a simple matter of monitoring flow conditions to ensure that gas does
not extend out the bottom of the cluster. Another change to the degasser
40 was to place wear plates on the leading edges of the drop tubes 46, to
prevent wear by the various solids.
A circulation pump 50 is situated exterior to the main
compartments of the separator 14. Circulation pump 50 is connected to a
suction line 54 which has a main valve 59 and three intake valves 60.
Intake valves 60 may be closed or opened as desired to control the flow of
fluid through the compartments of separator 14. In the preferred
embodiment intake valves are controlled by a valve mechanism (see
Figure 3). Also connected to the circulation pump 50 is a discharge line 68
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which has five mud guns 80 branching from the discharge line 68. Fluid
from the discharge line 68 may be routed through any mud gun 80 by
actuating the mud gun control valve 84 which regulates flow of fluid from
discharge line 68 to mud gun 80. In the present embodiment the mud gun
control valves 84 are mechanically actuated; however to one skilled in the
art electrical actuation would be equally possible. As the sediments in a
tank build up the operator will open the appropriate mud gun control
valves 84 allowing the fluids cycled by circulation pump 50 to enter mud
gun 80 thus agitating any settling debris. Mud guns 80 are rotatably
mounted (as shown in Figure 4) to discharge line 68 so that they may be
directed throughout a compartment to stir up debris.
A shale shaker pump 90 resides at the base of the first
compartment 48. The shale shaker pump 90 is well known in the art and
is commonly referred to as an ABS pump, and is designed to handle liquid
containing significant quantities of solids. In the preferred embodiment
the ABS pump is provided with a hardened impeller. In experimentation
it was found that a standard impeller lasted approximately 100 hours. A
hardened impeller is expected to have three to four times that life. Two
different techniques have been used for hardening the impeller, namely:
a) hardening the surface of the impeller to one or two thousandths of an
inch and then coating with a two thousandths of an inch hardening
treatment or, b) treating the entire impeller so that it just penetrated
throughout to harden it.
The cuttings and fluid are pumped from the base of first
compartment 48 to a shale shaker 86 by the shale shaker pump 90 via the
shale shaker input line 87 (shown as a dashed line). As the cuttings settle
to the base of first compartment 48, inclined base 92 channels them toward
the shale shaker pump 90. Should the deposits at the base of first
compartment 48 no longer continue to adequately flow through shale
shaker input line 87, mud gun 80 of first compartment 48 may be actuated
to stir up the deposits, thus allowing them to be pumped through shale
shaker input line 87. Shale shaker pump 90 is attached to a winch
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mechanism 88 which allows for efficient and rapid replacement of shale
shaker pump 90 for service and maintenance. Shale shaker pump 90
engages shale shaker input line 87 by way of shale shaker pump connector
94 (Figure 3).
The shale shaker input line 87 is connected to the top of the
shale shaker 86 which resides above the second compartment 52. The
shale shaker 86 in known manner, is configured to shake or move larger
particles of rock until they fall into an exterior shale tank (not shown). As
is known in the art, the shale shaker 86 functions as a sifting screen. The
size of the mesh in the screen may be changed to allow for different size
particles to pass through. The shale shaker 86 vibrates the screen and as
the screen is positioned on an angle slightly above or below the horizontal,
the larger solids that fail to pass through the screen work to the end of the
vibrating screen and fall off into the exterior shale tank. In the preferred
embodiment the drill cuttings separated by the shale shaker 86 to the
external shale tank are of sufficient size to provide samples of use to
geologists examining the geological structure of the site. In the case of air
drilling the material exiting the well bore comprises about 50% drill
cuttings and 50% dust, depending on formation. Since a large portion of
the cuttings are very fine, and will pass through any screen, the use of a
coarse screen, e.g. one with 210 or 250 mesh, will ensure that the large
cuttings are separated. Flocculant (from a fourth compartment 100) may
be added to the shale shaker 86, to aid in flocculation of smaller particles.
Smaller particles may be charged, causing them to repel each other. The
flocculant serves to eliminate the effect of the electric field and permits
the
particles to flocculate or coagulate. Liquids and fines (small particles)
simply fall through the shale shaker 86 into the second compartment 52.
The shale shaker 86 can be replaced by a scalper or alternative
device if there is a problem of foam being recreated. Due to its vibratory
motion, the shale shaker 86 may recreate the foam that was broken up by
the degasser 40.
Residing above a third compartment 96 is a centrifuge 98.
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The centrifuge 98 is of a type known in the art as a decanter centrifuge.
The fines and liquid contained in the second compartment 52 are pumped
through centrifuge input line 97 via an external pump (not shown) to the
centrifuge 98. The fines and liquid pumped from second compartment 52
are mixed with a polymer flocculant agent pumped from the fourth
compartment 100 via flocculant line 103, prior to their entry into the
centrifuge 98. The purpose of the flocculant being to attract smaller
particles to each other so that they may be extracted from the fluid by the
centrifuge. Solids extracted by the centrifuge 98 are removed by an auger to
the shale tank (not shown). Liquid and small fines from the centrifuge 98
are typically passed to the third compartment 96, but may be passed to any
tank. The centrifuge could be provided with a hose to direct outlet fluids
into any tank as desired, for example to bring up the level of a particular
tank.
The fourth compartment 100 is the final compartment of the
separator 14. The fourth compartment 100 is divided into two tanks. Each
tank contains a polymer flocculant, a flocculant pump 102 and a flocculant
agitator 104. The pumps 102 serve to pump the flocculant to the centrifuge
98 via flocculant line 103. While one tank is in use, the second is used to
mix new polymers. When the first tank becomes empty the pump is
switched to use the second tank which then becomes the flocculant source.
The flocculant agitators 104 serve to mix flocculant with water, and the
compartments 100 are provided with a device for adding concentrated
flocculant. The flocculant causes ultra fines within the liquid, e.g. those
particles of less than 50 microns in size, to coagulate. If necessary, a
further external tank may be provided where the fluid as output from the
centrifuge may be treated with carbon or other standard chemicals so that
it will meet a micro toxicity test.
Adjacent to fourth compartment 100 is operator cabin 101
which contains electrical controls for pump control which provides shelter
for an operator during winter operation.
Referring now to Figure 3, a photograph of a portion of the
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first compartment 48 of the separator 14 is shown. One drop tube 46 from
the degasser 40 is shown in the foreground. The end of the suction line 54
is shown with one intake valve 60 open. Intake valve 60 may be closed by
the vertical movement of intake valve control arm 62 which lifts valve
shutoff 64 to engage with the face of intake valve 60 resulting in the
closing of intake valve 60. Shale shaker input line 87 and shale shaker
pump connector 94 are shown without shale shaker pump 90. Shale
shaker pump 90 is configured to be raised and lowered by winch
mechanism 88 along pump guide rod 89. The shale shaker pump 90 and
the shale shaker pump connector 94 each have flanges which engage each
other when the shale shaker pump 90 is lowered by the winch mechanism
88 along pump guide rod 89 to mate with shale shaker pump connector 94.
One connecting gate 112 is shown in Figure 3, and this
connects the first compartment 48 to the second compartment 52. The gate
112 is shown in the closed position. By raising gate arm 114, connecting
gate 112 is opened, thus allowing fluid to flow from first compartment 48
to second compartment 52. Connecting gates 112 between the other
compartments are similarly configured.
Figure 4 is a photograph of a mud gun 80 located within the
first compartment 48 of the separator 14. The mud guns 80 are common in
mud tanks and the like and their design can follow conventional practice.
The mud gun 80 is rotatably connected to discharge line 68 by a rotation
collar 70. A rotator mechanism 72 permits the rotation of mud gun 80
within rotation collar 70. The rotator mechanism 72 contains a plurality of
slots 74 which are sized to engage one or more teeth 76 mounted on the
external surface of mud gun 80. Once tooth 76 has been engaged in slot 74,
mud gun 80 may be rotated by using control arm 78, thus moving the
position of mud gun outlet 82. Through the use of control arm 78, the
mud gun outlet 82 may be rotated through 360~, allowing the mud gun 80
to stir up sediments in any portion of the compartment.
Referring now to Figure 5, a top plan view of the preferred
embodiment of the apparatus, the circulation pump 50 is connected to the
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suction line 54 with its associated intake valves 60 and to the discharge
line 68 with its associated mud guns 80. A steam line 106 extends through
the compartments of the separator 14 and may be activated in cold weather
operations to prevent the fluid in the separator from freezing. A steam
manifold 108 may be connected to an external steam line to provide a
source of steam.
Referring now to Figure 6, an end view of the preferred
embodiment of the apparatus, dump gates 110 are illustrated. A dump
gate 110 is located at the base of each compartment. The dump gate 110
allows the operator to flush or scrape out any sediments remaining in the
compartments after the separator 14 has been drained.
Referring now to Figure 7, there is shown a perspective view
of a mechanism to aid in the alignment of the degasser 40 with the blooie
line 12. A degasser alignment mechanism 116 comprises a fixed alignment
support 118, a slidable alignment support 120, an alignment screw 122, an
alignment handle 124 and an alignment base 126. The fixed alignment
support 118 is securely attached to the main body of the separator 14 by
welding or the like to ensure it remains immobile. The fixed and slidable
alignment supports 118, 120 have abutting sliding surfaces, which
preferably are maintained lubricated. The slidable alignment support 120
is in the form of a cradle to support the degasser input line 39. The slidable
alignment support 120 is securely attached by welding to the exterior wall
of the degasser input line 39, proximate the degasser connector 38. An
alignment screw 122 adjustably connects the fixed alignment support 118
to the slidable alignment support 120. Rotation of an alignment handle
124 in a clockwise or counter clockwise direction rotates the alignment
screw 122 and causes the slidable alignment support 120 to move laterally
away from or toward the fixed alignment support 118 along an alignment
base 126. The alignment base 126 has attached to each end of its upper
surface, an alignment stop 128. The alignment stops 128 ensure that the
slidable alignment support 120 does not move beyond a desired range of
adjustment. Attached to the slidable alignment support 120 is a locking
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plate 130. The locking plate 130 has a locking channel 132 which also
serves to limit the lateral movement of the slidable alignment support 120
along the alignment base 126. Positioned within the locking channel 132
is a locking bolt 134 which is connected to the alignment base 126. Once
the degasser connector 38 is aligned with the blooie line 12, the locking bolt
134 is tightened to secure the position of the degasser input line 39.
As can be appreciated by one skilled in the art, the ability to
laterally adjust the degasser input line 39 to mate with the degasser
connector 38 is a preferred solution to moving the entire separator 14 in an
attempt to provide a connection.
Referring now to Figure 8, a perspective view of a posterior
alignment mechanism designed to function in cooperation with the
alignment mechanism of Figure 7, the posterior alignment mechanism
136 is shown. The posterior alignment mechanism 136 is of similar
construction to the degasser alignment mechanism 116. The posterior
alignment mechanism 136 serves to cooperate with the degasser
alignment mechanism 116 in that it allows for the lateral movement of
the degasser 40 of required. The structure of alignment mechanism 116 is
similar to that of posterior alignment mechanism 136 and a description of
the like numbered components may be found in the description of Figure
7 above. The posterior alignment mechanism 136 has as its slidable
alignment support 120, a pair of flanges welded to the exterior of a pair of
drop tubes 46.
As can be appreciated, the alignment mechanisms 116, 136
may cooperate to provide a slight angular movement, thus allowing the
line 12 to enter the degasser 40 at an angle not parallel to the vertical
walls
of the separator 40.
Referring now to Figure 9, there is shown a perspective view
of an adapter used to connect the line from the well bore to the separator.
As discussed above, with regard to Figure 1, the dead head 19 in its
standard configuration has an inlet 8 inches in diameter and an outlet 16
inches in diameter. The degasser connector 38 is sixteen inches in
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diameter. In some drilling situations, for example when using foam, it
may be beneficial to eliminate the dead head 19 entirely or alternatively
provide for an outlet diameter of 8 inches from the dead head, i.e. with no
change in diameter. The use of an 8 inch pipe and no dead head allows
the foam to flow at a relatively high velocity, which aids the degasser 40 in
breaking down the foam. As the degasser connector 38 receives a
connection sixteen inches in diameter, the degasser adaptor 138 is required
for such situations. The degasser adaptor 138 has an adaptor flange 140
sized to mate with the degasser connector 38. When the adaptor flange 140
and degasser connector 38 are mated, the degasser insert 142 is contained
within the walls of degasser input line 39. Thus, just prior to entry into
the degasser 40, the flow from the well bore 20 is contained within the
degasser adapter 138. This avoids any abrupt change in the flow cross-
section.
In use, the separator 14 operates as follows: the blooie line 12
connects the separator 14 to the drilling rig shown generally as 16. The
drilling rig 16 comprises a rotatable drill string 18 which extends into the
well bore 20. At the end of the drill string 18 in the well bore 20 is
mounted a drill bit 24. As the drill string 18 rotates, the drill bit 24 cuts
into the ground. Drilling fluid 26 is pumped through the drill string 18 to
cool drill bit 24 and to flush cuttings to the surface and out of the bottom
of
the drill bit 24. The drilling fluid 26 then returns to the surface of the
drilling rig through the annular space 22 between the drill string 18 and
the well bore 20. The drilling fluid 26 then exits the drilling rig 16 through
the blooie line 12 toward the separator 14. Water or steam is injected into
the drilling fluid 26 at intake line 30. This serves to mix water with dust or
other cuttings to aid in dedusting. The drilling fluid 26 then contacts
impact plates 28 which serve to slow down its velocity. After contacting
the impact plates 28, the now slower moving drilling fluid 26 drops to a
chamber below the impact plates 28 and proceeds along the blooie line 12
toward the separator 14. Corresponding to these different velocities, the
blooie line upstream and downstream from the impact plates has different
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diameters; for example, in air drilling, the diameter is 8" upstream while
the diameter is 16" downstream. In the case of foam drilling, the impact
plates may be eliminated and a single 8 inch line to the separator may be
utilized. This smaller diameter line keeps the foam at a high velocity
which makes it easier for the separator to break it down.
Flow into the blooie line 12 may be reduced by injecting
water into intake line 30, and this also serves to wet dust in the air flow
for
pure air drilling. For example, if 5,000 litres per minute are injected
through intake line 30, then the air flow upstream of intake line 30 has to
impart momentum to the injected water, which in turn creates back
pressure. This back pressure is exerted upon the well, which in turn limits
the flow from the well and allows the pressure on the oil reservoir to be
controlled without restricting flow from the well. The injection of water
also makes the drilling fluid 26 more dense and more liquid to aid in
separation of the air, gas, foam, solids from the liquid.
The blooie line 12 also contains the additional intake ports
32, 34, and 36. Intake port 32 is a water injection connection similar to
intake line 30, to enable injection of water to kill dust cuttings, dilute
foam
and reduce the velocity or momentum of the flow in the blooie line 12.
The port 34 is a bypass connection, when a drill pipe connection is made
while drilling, air flow which would normally go down the well bore, is
diverted into this port or intake 34. This diverts air flow away from the
drill pipe and allows the drilling rig crew to safely make a connection to a
new pipe, and it also maintains a uniform flow through the blooie line 12,
downstream from this connection. Intake port 36 is a high volume water
injection point which serves to further kill dust cuttings, dilute foam and
reduce momentum if required.
These connections were also originally intended for breaking
down foam, but it is now preferred to provide a second deduster unit in
addition to the one shown at 30, for foam applications.
The drilling fluid 26, having passed through the blooie line
12, next enters the degasser 40. The degasser 40, a Vortex Cluster
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manufactured by Porta-Test International Inc., separates the gases in the
drilling fluid 26 from the solids and liquids. The gases are vented out to a
flare pit or flare stack (not shown) through a flare pit exit 42 where they
are
burned. The solids and liquids then flow down the set of drop tubes 46
and fall to the bottom of the first compartment 48. The liquid level in the
first compartment 48 is maintained high enough to prevent flow of gas
down through the drop tubes 46.
The liquid in separator 14 is circulated through the separator
14 by the circulation pump 50. The circulation pump 50 may extract liquid
from the bottom of any or all of the first, second or third compartments
(48, 52, 96) via the suction line 54 and associated intake valves 60. In
standard use, suction line 54 will extract fluid solely from the third
compartment 96. The operator may, however, choose to open or close any
of the intake valves 60 by utilizing intake valve control arm 62 (Figure 3).
The liquid is circulated through circulation pump 50 and expelled via
discharge line 68 to mud guns 80. Mud guns 80 serve to stir up sediment
at the base of individual compartments within the tank. The operator
may control the flow of liquid through a mud gun 80 by opening or
closing mud gun control valve 84. In addition to opening or closing the
control valves 84, the operator may rotate each mud gun 80 by using the
control arm 78 (Figure 4).
The liquid and sediments at the base of the first compartment
48 are pumped to the conventional shale shaker 86 through shale shaker
input line 87 by the shale shaker pump 90. The shale shaker 86 screens out
the larger solids and jettisons them to a shale tank (not shown) exterior to
the separator 14. Typically, this is a tank, which can be a three sided tank,
butted against the side of the separator 14 for collecting the shale. In the
preferred embodiment, the liquid exiting through the shale shaker 86, is
returned to the second compartment 52. The liquid may, however, be
routed to any of the other compartments (48, 96) compartments via a hose
connection (not shown) from the shale shaker 86.
The liquid is pumped by an external pump (not shown)
CA 02256821 1998-12-18
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through centrifuge input line 97, from the second compartment 52 to the
centrifuge 98. The centrifuge 98 separates the finer solids from the liquid
and deposits the solids in the shale tank (not shown). The centrifuge 98
also helps to break up any foam in the liquid mixture. Associated with the
centrifuge is a flocculant pump 102 which may add chemicals such as
polymers to the liquid to promote flocculation of the particles in the
liquid, diluted flocculant being pumped from the fourth compartment 100
via flocculant line 103. The liquid is then returned from the centrifuge 98
to the third compartment 96. The liquid may, however, be routed to any
of the other compartments (48, 52) via a hose connection (not shown).
Once the liquid reaches the third compartment 96 it is pumped out to be
re-used in the drilling process, stored in a tank or deposited at the site if
it
meets environmental guidelines. A portable submersible pump (not
shown) can be provided in the third compartment 96 to pump out the
relatively clean water.
A steam line 106 runs through the compartments of the tank
and may be activated in cold weather operations to prevent the liquid in
the tank from freezing. A steam manifold 108 is connected to the steam
line to provide an external source of steam.
When use of the separator 14 at a particular site is finished, or
in the event that enough sediment has accumulated to impede proper
filtration, the various pumps are turned off. The unit is then drained, by
way of external dump gates 1l0 located near the base of each compartment
and the sediment removed via the dump gates 110.
It is noted that the present invention will handle:
(a) foam drilling;
(b) air rated fluids;
(c) dust drilling;
(d) nitrified flows;
(e) sweet gas (i.e. no H2S);
(f) under balanced operations;
(g) mist drilling; and
CA 02256821 1998-12-18
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(h) environmental fluids and solids clean ups.
Although the preferred embodiment comprises four
compartments (48, 52, 96, 100), a degasser 40, and a shale shaker 86,
additional compartments, shale shakers, centrifuges and degassers, may be
added to handle large flow volumes.
In an alternative embodiment, the separator 14 may be sized
to fit within a frame dimensioned to the standard shipping container.
This would allow for simple shipping and deployment in offshore use.
For offshore use an alternative drilling fluid would be a combination of
diesel fuel and brine water. This could conceivably be aerated with
nitrogen, to lighten the fluid column.
In an alternative use, the separator 14 may be utilized in a
mining application. For example, in the cleaning up of tailings from gold
mine operations. The large solids from the tailings would be separated by
the shale shaker and the centrifuge would be set to separate out from the
tailings any residual gold dust.
