Note: Descriptions are shown in the official language in which they were submitted.
CA 02578318 2007-02-23
METHODS OF STABILIZING DRILL FLUIDS AND DRILL CUTTINGS,
COMPOSITIONS AND USES THEREOF
FIELD OF THE INVENTION
Methods of stabilizing oil-based drilling fluids and hydrocarbon-contaminated
drill cuttings are
described. In addition, methods of using hydrocarbon-contaminated drilling
fluids and stabilized
drill cutting compositions are also described. These methods include the use
of use oil-based
drilling fluids and cuttings and stabilized oil-based drilling fluids and
drill cuttings in road
construction for dust suppression and as a fuel source. In addition, methods
of disposing of
stabilized drill cuttings are described.
BACKGROUND OF THE INVENTION
In the past, the disposal of drill fluids and drill cuttings has been a
significant issue for drill site
operators. For example, in a typical drilled well in the oil industry, upwards
of 100 m3 of drill
cuttings may be produced from a single well. Typical drill cuttings and drill
fluids will also
contain a variety of contaminants such as hydrocarbons, salts, metals, soaps
and other agents that
may have been added to the drilling fluid to assist in the drilling and
hydrocarbon recovery
processes or from contaminants from the formation that have become mixed with
the drilling
fluid.
In particular, in a typical drilling process, recovered and dried drill
cuttings may include up to
approximately 50 %(w/w) hydrocarbon contaminants for very small particle drill
cuttings or 0-20
% (w/w) for larger particle size drill cuttings. The contaminating
hydrocarbons may range in
viscosity from highly viscous bitumens through to less viscous lighter
fractions. Drill fluids may
also contain significant quantities of hydrocarbons that have originated
either from manufacture
of the original drill fluid composition or from the formation.
In the past, drill fluids are usually disposed of by transporting the used
drill fluids to a processor
that removes the solid fraction through chemical and mechanical means. The
remaining fluid is
usually then sold to asphalting companies. Transporting used drill fluids and
drill cuttings is
difficult due to the liquid or semi-liquid nature of these materials.
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Acceptable methods of disposal of drill cuttings are usually dictated by
various jurisdictional
regulations and will usually require that the drill cuttings are properly
remediated into the local
soil or alternatively, removed to a landfill site.
Current methods for adsorbing or absorbing contaminating hydrocarbons prior to
remediation
often include mixing the drill cuttings with cellulose based materials such as
sawdust. The use of
sawdust, as a method of remediating drill cuttings, however requires very
large volumes of
sawdust in order to effectively stabilize the drill cuttings. For example, 100
m3 of drill cuttings
may require approximately 200 m3 of sawdust in order to effectively stabilize
the cuttings which
significantly affects the transportation and disposal costs of the drill
cuttings. The presence of
cellulose material in oil based drilling fluid cuttings will also limit the
use of those stabilized
cuttings in other applications.
Further still, either disposal method, may lead to certain environmental
contamination as the
various contaminants may ultimately leach into the local groundwater,
particularly as the sawdust
decomposes. Moreover, the cost of transportation of drill cuttings to a
landfill and/or the cost of
soil remediation is significant.
However, as is known, road construction is not subjected to the same
environmental regulations
that either a local drilling site or landfill may be. That is, at a local
drill site, as a result of the
relative concentration of contaminants within drill cuttings, the regulations
are relatively strict
concerning acceptable levels of contaminants that may be contained within a
particular area
without proper remediation or disposal. In contrast, during the construction
of a road, the same
standards do not apply. That is, it is well known that government agencies use
hydrocarbons
and/or chlorides mixed with gravel aggregates to provide dust suppression in
gravel or dirt roads.
At a drill site, acceptable levels of hydrocarbons present within the soil
would be relatively low
whereas in providing dust suppression to a gravel or dirt road significantly
higher levels of
hydrocarbons in the form of crude oil can be laid down over large areas where
it is known that
certain quantities of the hydrocarbons will, over time leach away from the
road to the local
environment.
As a result, there has been a need for effective disposal methods wherein
drill fluids and drill
cuttings are disposed of in a manner that meets environmental regulations and
that does not
increase the overall cost of disposal. More specifically, there has been a
need for a disposal
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CA 02578318 2007-02-23
method in which drill fluids and drill cuttings provide a useful product
wherein the contaminants
may be encapsulated or incorporated with other products to reduce the
likelihood of such
contaminants leaching to the environment and that may otherwise provide useful
and beneficial
properties to the road. The use of oil based drilling fluids and cuttings can
provide a low cost
alternative to traditional disposal methods.
In addition, the disposal of used rubber tires and asphalt shingles is a
significant environmental
issue with there continuing to be a need for effective uses of these
materials.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a method of disposing of
drill cuttings by
incorporating the drill cuttings into a road. In particular, there is provided
a method of disposal of
hydrocarbon-contaminated drill cuttings in a road comprising the steps of:
mixing hydrocarbon-
contaminated drill cuttings with virgin aggregates to form a blended mixture;
and incorporating
the blended mixture into the road. The degree of hydrocarbon contamination of
the drill cuttings
may be less than 15 % (w/w) (hydrocarbon/drill cuttings). Hydrocarbon-
contaminated drill
cuttings may also be mixed with virgin aggregates to 5-25 % (w/w).
In various embodiments, the blended mixture is incorporated as the base course
of a road and/or
the blended mixture is further mixed with asphalt cement to form asphalt
concrete and the asphalt
concrete is incorporated into the top course of a road. The blended mixture
may also be mixed to
a consistency enabling effective use of the blended mixture for dust
suppression within a road.
In a further embodiment, the hydrocarbon-contaminated drill cuttings are mixed
with blending
materials selected from, for example, any one of or a combination of
elastomeric materials such
as recycled rubber, viscous hydrocarbons such as recycled asphalt shingles
and/or waxes.
In another embodiment, the invention provides a method of disposal of
hydrocarbon-
contaminated drill cuttings in a road comprising the steps of: mixing
hydrocarbon-contaminated
drill cuttings with an elastomeric material, viscous hydrocarbon and/or wax to
form a blended
mixture of a desired consistency; and incorporating the blended mixture into
the road.
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In a further embodiment, the invention provides for the use of hydrocarbon
contaminated drill
cuttings stabilized with elastomeric materials, viscous hydrocarbons and/or
waxes for dust
suppression in roads. The elastomeric materials and viscous hydrocarbons, in
various
embodiments may be selected from any one of or a combination of recycled
rubber crumb and
recycled asphalt shingles.
In a further embodiment, the invention provides a method of stabilizing
hydrocarbon-
contaminated drill cuttings comprising the step of mixing hydrocarbon-
contaminated drill
cuttings with blending materials to form a blended mixture of a desired
consistency.
In yet a further embodiment, the invention provides a method of stabilizing
hydrocarbon
contaminated drill fluids comprising the step of mixing hydrocarbon-
contaminated drill fluids
with blending materials to form a blended mixture of a desired consistency.
Blended mixtures and compositions prepared in accordance with the invention
may also be used
as a fuel source.
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DETAILED DESCRIPTION
Methods of stabilizing oil-based drilling fluids and hydrocarbon-contaminated
drill cuttings are
described. In addition, methods of using hydrocarbon-contaminated drilling
fluids and stabilized
drill cutting compositions are also described. These methods include the use
of use oil-based
drilling fluids and cuttings and stabilized oil-based drilling fluids and
drill cuttings in road
construction for dust suppression and as a fuel source. In addition, methods
of disposing of
stabilized drill cuttings are provided. Within this description, drilling
fluids generally include oil-
based drilling fluids, frac fluids and production fluids such as hydrocarbon
based fluids and/or
synthetic oils or silicate oils.
Methods of Stabilizing Oil-Based Drilling Fluids and Drill Cuttings
In one embodiment, oil-based drilling fluids and/or hydrocarbon-contaminated
drill cuttings are
blended with elastomeric hydrocarbon materials, viscous hydrocarbons including
asphalts and/or
waxes as a means to stabilize drill fluids or cuttings for subsequent uses.
Within this description
these materials are collectively referred to as blending materials. The
blending materials are
mixed with the drilling fluid or drill cuttings to absorb excess free oil
contained within the drilling
fluid or drill cuttings. In addition to absorbing free oil, the blending
materials may be added in
proportions such that the consistency of the resulting mixture is suitable for
a variety of uses.
Such uses may be to improve the ease of handling of the stabilized drill fluid
or cuttings for
remediation of the mixture to the ground, for use in road construction, dust
suppression and/or as
a fuel source.
Generally, drill cuttings removed from a well will be a loose, slippery and
fluid mixture of rock
particles coated with varying amounts of hydrocarbons and other contaminants.
After mixing
with the blending materials in appropriate proportions in accordance with the
invention, the
resulting mixtures will have the general appearance of granular, dry rock.
Depending on the
specific hydrocarbon contaminants and proportions used, the resulting mixtures
may be clumpy.
Mixtures may be created by any suitable mechanical mixing apparatus including
disking
machines, mechanical stirring equipment and other equipment known to those
skilled in the art.
After creating mixtures of the desired solid or semi-solid consistency, the
mixtures may be
handled by conventional handling equipment for materials of a similar
consistency.
Preferred blending materials include recycled elastomeric hydrocarbon
materials such as recycled
rubber from tires. Viscous hydrocarbons may include recycled asphalt shingles,
natural asphalts
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such as gilsonite, and/or waxes. Within this application, wax generally refers
to both refined
paraffin materials and other source materials occurring in nature and
described in the literature as
wax materials. Examples of waxes and viscous hydrocarbons include but are not
limited to
montan wax, ceresine wax, beeswax, candelilla wax, carnauba wax, castor wax,
chinese wax,
hydrogenated jojoba oil, jojoba wax, jojoba oil, jojoba esters, lanolin,
lignoceric acid, ozokerite,
ouricury wax, paraffin (from crude oil) and shellac.
The blending materials may be mixed with the drill fluid or drill cuttings at
an appropriate
proportion to reduce the free oil content within the drill fluid or drill
cuttings and thereby impart
further binding properties to the aggregate and/or asphalt cement for a road
construction
application.
In a road construction or road dust suppression application, the amount of
added blending
materials may be at any suitable proportion to produce a desired consistency
of the aggregate
and/or asphalt cement. In other words, sufficient blending material may be
added to create a
"dry" mixture where substantially all free oil is absorbed, or to maintain a
"wet" or "semi-wet"
mixture.
In an alternate application, the amount of blendng material added may be
sufficient to create a
blended drill cutting/blending material composition having a consistency
wherein excess free oil
on the drill cuttings is absorbed to the extent that the blended composition
is sufficiently "clean"
or "dry" to enable it to be buried in the ground.
Importantly, in comparison to the use of past materials to affect hydrocarbon
absorption,
substantially smaller volumes of blending materials may be added to the drill
cuttings to absorb
free oil. In the past, for example, a 200% volume of sawdust may be required
to absorb free oil
relative to a given volume of drill cuttings, whereas in accordance with the
present invention, a
10% volume of blending material may only be required to absorb free oil on
similar drill cuttings.
As can be readily understood, such a substantial reduction in blending
material quantities will
significantly lower the volume of the mixtures, which substantially reduces
the handling and
transportation costs of the materials.
In various embodiments, a blending of 3-5% by weight of such materials
relative to the drill fluid
or drill cuttings can provide a desired consistency to enable effective
handling of the material.
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Road Construction
As is known, a typical road construction includes a sub-grade of supporting
native rock, soil,
sand, clay or other material onto which a base course generally comprising a
depth of crushed
gravel or aggregate is placed and compacted. The aggregate will usually range
in depth from 12
inches to several feet depending on the engineering requirements of the road
and may include
various additives that provide dust suppression if the road is not to be
sealed.
In a sealed road, a surface course of a concrete (usually an asphalt concrete)
is applied and
compacted over the aggregate to seal and bind the upper surface of the road.
As is known, asphalt
is a complex mixture of hydrocarbons primarily comprised of bitumen which in
itself is generally
comprised of asphaltenes as the dispersed phase and maltenes as the continuous
phase. Mixed
with various aggregates or mixtures of aggregates, varying blends of asphalt
concrete can be
produced depending on the desired qualities for the road surface.
In accordance with the invention, drill cuttings are incorporated into a road
bed either as part of
the base course or surface course in conjunction with appropriate quantities
of aggregates and/or
asphalt. The use of drill cuttings as described herein is particularly
effective in dust suppression
for gravel roads. Drill fluids as described herein are also particularly
effective in dust suppression.
As noted above, drill cuttings may include hydrocarbon contaminants or
diluents coated upon the
native rock chips removed from the drilled well.
In a first embodiment, the drill cuttings are blended with aggregate to 5-25 %
(w/w) for use as the
base course of a road bed with or without a surface course. The blended drill
cuttings and
aggregate may be applied to the road bed in the usual manner with graders and
compaction
vehicles. In this embodiment, as a result of the hydrocarbon contaminants, the
blended drill
cuttings and aggregate provide effective dust suppression when used in an
unsealed road.
In a second embodiment, drill cuttings are blended with aggregate to 5-25 %
(w/w) and blended
with asphalt cement such that the asphalt cement is 4-8 % (w/w) of the total
mass of the resulting
asphalt concrete.
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The blending of drill cuttings with aggregate may be achieved through use of
appropriate mixing
equipment including reclaimers either at the road construction site, aggregate
quarry or an asphalt
plant.
The actual proportions of drill cuttings relative to aggregate are determined
through assessment of
the relative amounts of and properties of the hydrocarbon contaminants.
Generally, more viscous
hydrocarbon contaminants can be incorporated at a higher weight % whereas less
viscous more
volatile hydrocarbon contaminants are incorporated at a lower weight %.
Fuel Source
Mixing blending materials into oil wet drill cutting or used oil based
drilling fluids may allow for
the blended materials to be used as a solid or semi-solid fuel source. As many
blending materials
have a relatively high heat value, various mixtures of drill cuttings and
drill fluids are highly
effective as fuels. In particular, it should be noted that the heat value of
resulting mixtures can be
increased through the addition of particular blending materials and notably
higher when
compared to what they would be if mixed with cellulose or wood based
materials. Resulting
mixtures can effectively compete with coal as an efficient and low cost fuel
source. Comparative
BTU values of various fuels are shown in Table 1 and demonstrate that the
selection of particular
blending materials can significantly increase total heat value of a blended
mixture as compared to
sawdust.
Table 1-Comparative BTU values of various fuels
COMPARTIVE BTU
VALUES
ASPHALT 15,500 BTU/LB*
CHARCOAL 12,800 BTU/LB
ETHANOL 11,500 BTU/LB
SUBBITUMINOUS COAL 10,500 BTU/LB
LIGNITE COAL 7,300 BTU/LB
OIL (NO. 6 FUEL OIL - 151,000 BTU/GAL
'BUNKER C)
TIRE - CHIP FUEL 14,200 BTU/LB*
TIRE - DERIVED FUEL 15,500 BTU/LB*
RUBBER - DERIVED FUEL 16,000 BTU/LB**
WOOD (WET -'HOG FUEL') 4,375 BTU/LB
KEROSENE 19905 BTU/LB
PARAFFIN WAX 18057 BTU/LB
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For example a kerosene equivalent oil used for drilling fluid would generate a
cutting which
when stabilized with rubber crumb and/or asphalt shingles and/or wax would
provide a fuel
source approaching or exceeding 7300 BTU. A solids laden drilling fluid
stabilized in such a
manner would also provide a superior fuel source to coal when blended with
elastomers and/or
wax.
The above-described embodiments of the invention are intended to be examples
only.
Alterations, modifications and variations may be effected to the particular
embodiments by
those of skill in the art without departing from the scope of the invention
which is defined by the
following claims.
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