Note: Descriptions are shown in the official language in which they were submitted.
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TITIeE OF THE INVENTION:
Continuous Self-cleaning Drilling Fluid Tank
FIEI,17 OF THE INVENTION
The present invention relates tc a drilling fluid tank
used in earth drilling and, in particular, the drilling of
oil and gas wells.
BACI~CGFtOUND OF THE INVENTION
In earth drilling, drilling fluid is pumped down the
drill string; exiting through nozzles in the drill bit. As
pumping continues, the drill~_ng fluid flows up an annular
space on the outside of the drill string carrying cuttings to
surface. While the circulation of drilling fluid keeps the
bottom of the well bore clear of cuttings, it also plays a
vital role in well control as the column of drilling fluid
serves to contain well bore pressure. The viscosity of the
drilling fluid must be suited to well bore pressure. The
composition of the drilling fluid (oil based, water based)
must be suitable for the type of oil bearing or gas bearing
formation.
The drilling fluid is prepared in accordance with
directions given by a qualified expert. Due to the volume of
drilling fluid used, it is recycled. The recycling process
involves passing the drilling fluids through shakers and
other devices to remove large cuttings. The drilling fluids
are then diverted to a drilling fluid tank to be
'° reconditioned" to the desired viscosity and other
characteristics.
When drilling fluid is returned to the drilling- fluid
tank, a settling occurs. Fines from the cuttings which were
mixed with the drilling fluid, begin to settle out forming a
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sludge on the bottom of the drilling fluid tank,
Periodically this sludge must be removed using a vacuum
truck. The suction of the sludge from the drilling fluid tank
by the vacuum truck invariably removes some of the drilling
fluid and affects the chemical balance of the drilling fluid
in the drilling fluid tank. Every time this occurs, the
volume of drilling fluid removed must be replaced and
additional chemicals added.
gUy OF THE INVENTION
What is required is a drilling fluid tank that is
capable of continuous self-cleaning.
According to the present invention there is provided a
continuous self-cleaning drilling fluid tank which includes a
liquid impervious receptacle having a bottom and a peripheral
sidewall. Means are provided for diverting unprocessed
drilling fluid requiring -reconditioning into the receptacle.
A processed drilling fluid outlet is provided, whereby
reconditioned drilling fluid passes from the receptacle. A
plurality of scraper blades are provided which are carried by
a continuous loop conveyor positioned immediately adjacent to
the bottom. A sludge outlet is provided, whereby sludge
passes from the receptacle. Means are provided for driving
the continuous loop conveyor to cause the scraper blades to
scrape sludge resting on the bottom toward the sludge outlet.
With the drilling fluid tank, as described above, sludge
is continuously been directed by the scraper blades to the
sludge outlet.
Although- beneficial results may be obtained through the
use of the drilling fluid tank, as described above, the
addition of unprocessed drilling fluid into the drilling
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fluid tank can cause turbulence which retards the settling
out of fines from the drilling fluid. Even more beneficial
results may, therefore, be obtained when the means for
diverting unprocessed drilling fluid requiring reconditioning
into the receptacle is a spray manifold which is adapted to
spray unprocessed drilling fluid onto a surface of drilling
fluid in the receptacle.
Although beneficial results may be obtained through the
use of the drilling fluid tank, as described above, it is
preferred that a paddle system be provided which is adapted
to carry sludge out of the receptacle through the sludge
outlet. The use of paddles has been found to perform better
than a gravity feed through the use of an inclined. plane or
other feed mechanisms.
Although beneficial results may be obtained through the
use of the drilling fluid tank, as described above, the use
of a pump to remove reconditioned drilling fluid causes
undesirable turbulence which retards settling of fines. Even
more beneficial results may, therefore, be obtained when the
drilling fluid outlet extends through the peripheral sidewall
adjacent to the bottom and the drilling fluid outlet has an
upwardly extending feed pipe. With this configuration,
drilling fluid spills into the feed pipe and flows by force
of gravity through the drilling fluid outlet.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become
more apparent from the following description in which
reference is made to the appended drawings, the drawings are
for the purpose of illustration only and are not intended to
in any way limit the scope of the invention to the particular
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embodiment or embodiments shown, wherein:
FIGURE 1 is a perspective view of a continuous self-
cleaning drilling fluid tank constructed in accordance with
the teachings of the present invention.
FIGURE 2 is a side elevation view, in section, of the
drilling fluid tank illustrated in FIGURE 1-
FIGURE 3 is a top plan view of the drilling fluid tank
illustrated in FIGURE 1.
DETAIIaED DESCRIPTI0~1 OF THE PREFERRED E1~BODIMEI~TT
The preferred embodiment, a continuous self-cleaning
drilling fluid tank generally identified by reference numeral
10, will now be described with reference to gaIGS 1 through
3~
Structure and Relationship of Parts:
Referring to FIGURE 1. drilling fluid tank 10 includes
a liquid impervious receptacle 12 having a bottom 14 and a
peripheral sidewall 16. Referring to FIGURES 2 and g, in the
illustrated embodiment, a spray manifold 18, adapted with
slots 20, sprays unprocessed drilling fluid 22 onto a
drilling fluid surface 24 within liquid impervious receptacle
12. A processed drilling fluid outlet 26 extends through
peripheral sidewall 1~ adjacent to bottom 14 whereby
reconditioned drilling fluid passes from liquid impervious
receptacle 12. Referring to FIGS ~, processed drilling
fluid outlet 26 has an upwardly extending feed pipe 28 which
allows drilling fluid to spill into feed pipe inlet 30 and
flow, by force of gravity, out of liquid impervious
receptacle 12 through processed drilling fluid outlet 26. In
the illustrated embodiment, processed drilling fluid outlet
26 is further adapted with a pivotal joint 32 allowing for
angular adjustment of upwardly extending feed pipe 28.
Referring to FIGURES 1 through S, a. plurality of scraper
blades 34 actuated by a continuous loop conveyor 36 circulate
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within liquid impervious receptacle 12 such that scraper
blades 34 are positioned immediately adjacent to bottom 14 as
illustrated in ~°zGURE 2. Referring to gIG~9 irA the
illustrated embodiment, continuous loop conveyer 36 is in the
5 form of two continuous loop chains 38 transported by several
transverse rollers 40 such that plurality of scraper blades
34 extend transversely between continuous loop chains 38. In
the illustrated embodiment, liquid impervious receptacle 12
is further adapted with a paddle system 42 and a sludge
outlet 44, by which sludge is propelled from liquid
impervious receptacle 12. Referring to glGr 1 through 3,
continuous loop conveyor 36 and paddle system 42 are driven
by a drive motor 46 which causes scraper blades 34 to scrape
sludge resting on the bottom toward paddle system 42 and
sludge outlet 44.
The remaining aspects of continuous self-cleaning
drilling fluid tank 10, not directly related to the inventive
concept, will now be described. Referring to gyG
liquid impervious receptacle 12 is further adapted with a
chemical treatment unit 48, ladder 50, railing 52 and skid
54.
Operation:
The use and operation of continuous self-cleaning
drilling fluid tank 10 will now be described with reference
to glG~g g through 3. Referring to ~IG2, unprocessed
drilling fluid 22 is sprayed into liquid impervious
-receptacle 12. Spray manifold 18 continues to add
unprocessed drilling fluid 22, maintaining an optimum level
for drilling fluid surface 24, Referring to ~IG1, drive
motor 46 is engaged, driving continuous loop conveyor 36 and
paddle system 42. Referring to FIGS 2, this causes a
scraping action near bottom 14 of liquid impervious tank 12
by plurality of scraper blades 34. Referring to FIGS 3, as
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sludge settles toward bottom 14 of liquid impervious tank 12,
it is directed toward paddle system 42 which, in turn, expels
it out of sludge outlet 44. Referring to
reconditioned drilling fluid spills into feed pipe inlet 30
and drains by force of gravity out liquid impervious tank 12
through processed drilling fluid outlet 26.
Tank 12 is primarily a settling tank. As fines settle
out of the drilling fluids, they form sludge on bottom 14 of
tank 12. The present invention permits the continuous
removal of sludge from tank 12 as it settles. In addition,
the present invention accommodates the continuous entry of
unprocessed drilling fluids and the continuous exit of
processed drilling fluids, without disrupting the settling
process. The entry of drilling fluids is accommodated by
spraying them lightly onto the surface of liquid within tank
12. The removal of drilling fluids is accomplished by a
gravity feed through a skimmer pipe.
In this patent document, the word °"comprising" is used
in its non-limiting sense to mean that items following the
word are included, but items not specifically mentioned are
not excluded. A reference to an element by the indefinite
article °'a°' does not exclude the possibility that more than
one of the element is present, unless the context clearly
requires that there be one and only one of the elements.
It will be apparent to one skilled in the art that
modifications rnay be made to the illustrated embodiment
without departing from the spirit and scope of the invention
as hereinafter defined in the Claims.
