Note: Descriptions are shown in the official language in which they were submitted.
CA 02300659 2000-03-10
BP #492-944
BERESKIN & PARK CANADA
Title: DRILLING FLUID
Inventor(s): MICHAEL FEFER, LORNE PIERSON
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s This invention relates to the field of drilling fluids. In one
embodiment, the invention relates to a drilling fluid having oil as a
continuous phase. In another embodiment, this invention relates to a
rate of penetration enhancer comprising a continuous aqueous phase
having a fluid dispersed therein, or a spotting fluid.
BACKGROUND OF THE INVENTION
Drilling fluids used for offshore or on-shore applications
need to exhibit acceptable biodegradability, human, eco-toxicity, eco-
accumulation and lack of visual sheen credentials for them to be
considered as candidate fluids for the manufacturer of drilling fluids. In
addition, appropriate fluids used in the drilling arena need to possess
acceptable physical attributes. These generally include viscosities of less
than 4.0 cSt Q 40°C, flash values of 100°C (Cleveland Closed
Cup) and, for
cold weather applications, pour points of -40°C or lower. These
properties
2o have typically been only attainable through the use of expensive synthetic
fluids such as hydrogenated poly alpha olefins, as well as unsaturated
internal olefins and linear alpha-olefins and esters.
Drilling fluids may be classified as either water-based or oil-
based, depending upon whether the continuous phase of the fluid is
2s mainly oil or mainly water. At the same time, water-based fluids may
contain oil and oil-based fluids may contain water.
Water-based fluids conventionally include a hydratable clay,
suspended in water with the aid of suitable surfactants, emulsifiers and
other additives including salts, pH control agents and weighting agents
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- such as barite. Water constitutes the continuous phase of the formulated
fluid and is usually present in an amount of at least 50 percent of the
entire composition; minor amounts of oil are sometimes added to
enhance lubricity.
s Oil-based fluids have a hydrocarbon fluid as the continuous
phase and include other components such as clays to alter the viscosity,
and emulsifiers, gallants, weighting agents and other additives. Water
may be present in greater or lesser amounts but will usually not be greater
than 50 percent of the entire composition; if more than about 10 percent
1o water is present, the fluid is often referred to as an invert emulsion,
i.e. a
water-in-oil emulsion. In invert emulsion fluids, the amount of water is
typically up to about 40 weight percent based on the drilling fluid, with
the oil and the additives making up the remainder of the fluid.
Oil-based fluids may be formulated from various
1s hydrocarbon fluids such as synthetically derived poly alpha olefins,
internal olefins, esters, low toxicity mineral oils or even diesel oil. Diesel
and even low toxicity mineral oils are undesirable since they are toxic to
marine life. As a result, the discharge of drilling fluids containing these
oils into marine waters is usually strictly controlled because of the serious
2o effects which the oil components may have on marine organisms. For
this reason, offshore drilling rigs either use synthetic oil based fluids for
drilling, or return the oil-based fluids to shore after they have been used.
Synthetic fluids have the disadvantage of being very expensive.
Oil-based fluids may be made environmentally acceptable by
25 the use of oils which posses inherently low toxicity to marine organisms
and good biodegradability. Generally, these properties are associated i n
hydrocarbons with low aromaticity. For these reasons, drilling fluids
based on linear paraffins might be considered desirable. On the other
hand, however, linear paraffins tend to have high pour points. Further,
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higher molecular weight fractions of linear paraffins tend to be waxy so
that in the low temperature environments frequently encountered i n
offshore drilling, there is a significant risk that waxy paraffin deposits
will
be formed in the downhole equipment or in the riser connecting the sea
s bed to the drilling equipment. In either event, this is unacceptable so that
paraffinic oils have not achieved any significant utility as the base fluid i
n
oil based fluids.
Furthermore, several jurisdictions in Europe and North
America have either banned the discharge of all drilling cuttings
(including drilling fluids) or legislated the reduction of the level of oil-
on-cuttings that may be discharged. In light of this, drillers have started to
re-inject the oil laced cuttings back into the geological formations.
Because of the possibility of accidental spillage in these situations, there
is
a reluctance to use inexpensive diesel or low toxicity mineral oil based
fluids. At the same time, there is a reluctance to use expensive synthetics
oil based fluids. Consequently there is a need for an inexpensive
environmentally acceptable drilling fluid, which has good
environmental credentials and physical properties.
US Patent No. 5,189,012 to Patel et al. discloses a drilling fluid
2o having synthetic branched chain oligomers synthesized from one or
more olefins having a chain length of two to fourteen carbon atoms.
The oligomers have an average molecular weight of from 120 to 1000.
The synthetic hydrocarbon mixture possesses a viscosity of from 1.0 to 6.0
centistokes, preferably a viscosity of from 1.5 to 3.5 centistokes. The
2s synthetic hydrocarbons may be hydrogenated (saturated), partially
hydrogenated or non-hydrogenated.
US Patent No. 5,589,442 to Gee et al. discloses a drilling fluid
composed of "mostly linear" olefins, that is, non-branched olefins with at
least one double carbon-carbon bond present in the chain. The chain
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4
length of the olefins is at least twelve carbon atoms. The fluid contains
substantial amounts of internal olefins, and small amounts of branched
olefins.
US Patent No. 5,432,152 to Dawson et al. discloses an invert
s drilling fluid which comprises a water-in-oil emulsion which includes at
least 50 volume percent of a low toxicity base oil, an emulsifier, and at
least one solid additive suspended in the drilling fluid. At least about 25
volume percent of the base oil content of the drilling fluid is one or more
linear alpha-olefins which have from about 14 to 30 carbon atoms.
o US Patent No. 5,045,219 to Trahan et al. discloses a
polyalphaolefin based downhole lubricant and spotting fluid used as an
additive in water-based drilling. The polyalphaolefin contains no more
than 0.5% of 1-decene monomer, blended in a concentration range of at
least 5% by volume with emulsifiers.
~s Mercer et al. (US Patent No. 5,096,883) discloses a synthetic
based drilling fluid made from synthetic branched-chain paraffins that
may or may not contain ester functionalities. The base-oil has between
about 16 and about 40 atoms per molecule. Preferably, the branched-chain
paraffin used as the base-oil consists essentially of the dimer of 1-decene,
2o which has a viscosity of about 5 centistokes at 40°C.
Trahan et al. (US Patent No. 4,876,017) discloses a synthetic
hydrocarbon compound, such as a polyalphalolefin, which may be
combined with emulsifiers and thinners. The polyalphaolefin may be
used as a downhole lubricant in water based fluids. The fluids are non-
2s toxic. The polyalphalolefin may be used at higher ratios to functional
additives, to function as a spotting fluid for the removal of lodged tools
downhole.
US Patent No. 5,837,655 to Halliday et al. discloses non-toxic,
biodegradable purified paraffins that may be used as lubricants, rate of
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' S
penetration enhancers, and/or spotting fluids for water-based drilling
fluids. The paraffin component may be cycloparaffins having between
about 8-28 carbon atoms, preferably between about 8-16 carbon atoms,
straight or branched hydrocarbons having between 8 and 28 carbon atoms,
or mixtures of the two. Examples include white oils and other technical
or food grade paraffins. The white oils and food grade paraffins are
manufactured through conventional means such as hyrotreating or
through separation technologies. They have conventional pour points of,
for example, -18°C.
~o US Patent No. 5,605,879 to Halliday et al. discloses the use of
olefin isomers, which are added to water-based drilling fluids, for
downhole lubricants, rate of penetration enhancers, and/or spotting
fluids. The additives may be used to prevent a drill bit from sticking in a
formation, enhance the penetration of a drill bit through a formation, or
free a drill bit when it becomes lodged in a formation during drilling. The
olefin isomers may be compounds having the formula Cn H2~~"-x~+l, where
n is between about 8 and about 30; x is the number of carbon-carbon
double bonds in the isomer and is between about 1 and about (n/2).
Van Slyke (US Patent No. 5,958,845) discloses a non-toxic,
2o synthetic fluid for use in drilling fluids. The synthetic fluid may be at
least about 95 weight percent hydrocarbons containing 11 or more carbon
atoms, greater than 5 weight percent hydrocarbons containing 18 or more
carbon atoms, at least about 50 weight percent isoparaffins, at least about
90 weight percent total paraffins, at least 2 hydrocarbons containing a
2s consecutive number of carbon atoms, less than about 1 weight percent
naphthenics, and less than 0.1 volume percent aromatics. Alternately,
the synthetic fluid has at least about 95 weight percent hydrocarbons
containing 10 or more carbon atoms and at least about 90 weight percent
n-paraffins.
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US Patent No. 5,846,913 to Sawdon discloses a biodegradable
wellbore fluid. The fluid has a continuous oil phase containing a
dispersed hydrophilic liquid. The continuous oil phase has at least 50
percent by weight of an n-alkane having from 10 to 20 carbon atoms, or
s mixture of n-alkanes having from 10 to 20 carbon atoms. The continuous
oil phase is substantially free of cycloparaffins, isoparaffins, and aromatic
compounds, and not greater than 20 percent by volume of
polyalphaolefin.
Lin (US Patent No. 5,569,642) discloses an invert drilling
1n fluid (oil in water emulsion) based on synthetic hydrocarbons. The fluid
has at least 50 volume percent of a low toxicity base oil, and at least one
additive such as an emulsifier, viscosifier, or weighing agent. At least 25
weight percent of the base oil is content of the drilling fluid is a mixture
of a linear alkane and a branched alkane which may be prepared from
1s olefinic monomers. The olefinic monomers have carbon chain lengths
from six to twenty, and have at least one polymerizible double bond.
US Patent No. 5,498,596 to Ashjian et al. discloses well fluids
which are formulated with a hydrocarbon oil blend of a low viscosity
polyalpha-olefin (PAO) such as a low molecular weight oligomer of
2o decene together with a Clo to Cls paraffinic hydrocarbon from petroleum
and a Clo to Cl8 olefin such as dodecene-1 or tetradecene-1.
Van Slyke (US Patent No. 5,333,698) discloses a wellbore fluid
based on a white mineral oil. The white mineral oil has at least 95 weight
percent of compounds containing 14 or more carbon atoms. The white
2s mineral oil has an n-paraffinic content of at least 5.25 weight percent,
and
a total paraffinic content of 25 weight percent. The total naphthenic
content of the white mineral oil is between about 30 and about 75 weight
percent.
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US Patent No. 4,787,990 to Boyd discloses a low toxicity oil for
use in drilling fluids. The oil consists essentially of branched- and cyclic-
paraffins having 11 to 17 carbon atoms per molecule, and has a low
aromatic content of less than about 1%, and a low n-paraffin content (less
than about 5%).
It has now been discovered that it is possible to formulate
paraffin based drilling fluids for off-shore and ecologically sensitive on-
1o shore applications (eg. where the water table is close to the surface) with
fluids made through sequential hydrocracking, hydroisomerization and
hydrogenation reactions. The fluids produced as a result of this reaction
sequence (sometimes referred to herein as HHH Fluids) may be used as a
drilling fluid wherein the HHH Fluid itself is the continuous phase. The
1s drilling fluid may also include standard additives, which are common in
the industry for drilling fluids. In addition, the HHH Fluids may be mixed
together with synthetic fluids to reduce the cost of the latter without
compromising performance, ecotoxicity or biodegradability.
One advantage of the HHH Fluids produced according to this
2o invention is that they possess high levels of isomerized paraffins and
therefore exhibit good biodegradability and low toxicity. Further, they
have low pour points (eg. less than about -45°C, preferably less than
about
-55°C, and more preferably less than about -60°C). Their
viscosity does not
increase rapidly with decreasing temperature and therefore they disperse
25 more rapidly in cold water conditions endemic to deep sea and northern
climates. Therefore, drilling fluids based on the present invention
typically do not need to be stored in heated areas, even in cold weather
climates.
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A further advantage of the instant invention is that their
manufacture is significantly simpler than that of synthetic fluids that are
traditionally used in the field and are therefore less expensive.
In accordance with the instant invention, the HHH Fluids
may also be used as a constituent element of a drilling fluid having a
continuous aqueous phase, and the HHH Fluid is dispersed in the
aqueous phase. Examples of such drilling fluids include rate of
penetration enhancers and spotting fluids.
According to the present invention, drilling fluids are
formulated with a hydrocarbon oil component. The hydrocarbon is
Is produced by the sequential hydrocracking-hydroisomerization-
hydrogenation of a crude oil. The fluid produced by the sequential
hydrocracked-hydroisomerized-hydrogenated oil (HHH Fluid) may be a
mixture of one or more hydrocracked-hydroisomerized- hydrogenated
components having a chain length of about 10 to about 40 carbon atoms,
2o and may include isomerized paraffins, which may be branched non cyclic
paraffins or cyclic paraffins with branched alkyl side chains. Preferably, the
HHH Fluid is a mixture of one or more Clo to CZO isomerized-paraffins.
Most preferably, the HHH Fluid is a mixture of one or Clo - Cle isomerized
paraffins. The HHH Fluid preferably has a viscosity of about 1 to about 4
2s cStQ40 °C (ASTM D-445) and a flash point (ASTM D-93) of preferably
at
least 70°C, more preferably at least 100°C, and most preferably
at least
120°C. Preferably, the pour point should be less than about -40
°C (ASTM
D-97), and more preferably it should be less than about -50 °C. The
density
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' of the oil is preferably in the range of about 0.76 to about 0.86 kg/L at
15°C
(ASTM-D-1298).
The HHH Fluid of the present invention is preferably
substantially free of aromatic compounds. More preferably, the HHH
Fluid contains less than about 0.1 weight percent aromatic compounds.
Most preferably, the HHH Fluid contains less than about 0.01 weight
percent aromatic compounds. The HHH Fluid may be a mixture of one or
more isomerized paraffins having between about 10 and about 40 carbon.
Preferably, the HHH Fluid is a mixture of one or more isomerized
1o paraffins having between about 10 and about 20 carbon atoms. It will be
appreciated by those skilled in the art that the exact number of carbon
atoms in the HHH Fluid may be varied depending on the desired
viscometrics of the drilling fluid.
The HHH Fluid of the instant invention may be obtained by
atmospheric and vacuum distillation of a feedstock that is a crude oil.
Preferably, the fractions that are selected for the feedstock of the process
are those that are rich in linear molecules such as waxy vacuum gas fluid
fractions, wax fractions as well as heavier hydrocracker bottom fractions.
The feedstock is first subjected to a hydrotreating or
2o hydrocracking (herein referred to as hydrotreating) step. While
hydrotreating processing conditions are known to those skilled in the art,
in general terms, the feedstock is exposed to a catalyst at elevated pressure
and temperature conditions to obtain a hydrotreated product. The
hydrotreating catalyst may be a sulphur and nitrogen resistant catalyst,
which is based on sulphided group VIB and/or VIIIB metals. Examples of
such catalysts include Ni/W or Co/Mo on an alumina or crystalline
alumino silicate carrier. The hydrotreating may be conducted at a
temperature from about 200 to 450°C, at a pressure from about 400 to
about 4,000 psig and a space velocity of from about 0.1 to about 20 hr -1.
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The processing conditions are preferably adjusted such that the levels of
sulphur and nitrogen molecules are reduced to a level where they will
not act as poison in the subsequent hydroisomerization reaction.
Preferably, the hydrotreated product is free or at least essentially free of
s any sulphur and nitrogen molecules.
The hydrotreated product is then hydroisomerized. During
the hydroisomerization step, the linear or normal paraffin sections of the
molecules undergo branching with a resulting decrease in pour point.
Hydroisomerization processing conditions are known to those persons
1o skilled in the art. In general terms, the hydroisomerization reaction may
be carried out in conditions ranging from about 250 to about 450°C, at
pressures from about 100 to about 5,000 psig, a hydrogen circulation rate of
about 400 to about 15,000 SCF/B and liquid hourly space velocity of 0.1 hr 1
to 20 hr 1. The hydroisomerization reaction is conducted in the presence
~s of the catalyst. Preferably, the catalyst is a noble metal catalyst. For
example, the catalyst may be using a crystalline silicoaluminophosphate
molecular sieve catalyst which optionally contains group VIIIB and IIA
metals such as platinum or palladium.
The resultant hydroisomerized product is then subjected
2o to a hydrogenation step to eliminate any unstable molecules (for
example olefins) produced during the hydroisomerization step.
Hydrogenation procedures are well known in the art. Typically, the
hydrogenation is carried out in the presence of the catalyst and may be
conducted at a temperature from about 200 to about 350°C, a pressure
25 from about 400 to about 5,000 psig, and a hydrogen circulation rate
between about 400 SCF/B and about 15,000 SCF/B. The catalyst may be
a noble metal catalyst and/or a catalyst based upon sulphided group
VIB or VIIIB metals. Preferably the hydrogenation is conducted in the
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presence of a solid metal hydrogenation catalyst such as Ni, Pt or Pd o n
an alumina support.
The hydrogenated product is fractionated, such as using a
vacuum or atmospheric distillation column, to produce a narrow cut
s (from about Clo to about Cue, preferably from about Clo to about CZO and
most preferably from about Clz to about C18) as the HHH Fluid.
Through the choice of feedstock and processing conditions,
the composition of the fluids made by the sequential hydrocracking,
hydroisomerization and hydrogenation of the feedstock is controlled to
o yield products which have improved biodegradability, toxicology and
dispersive properties. Fluids obtained through the sequential steps set
out herein have improved properties over those known in the trade and
are easier to manufacture.
The HHH Fluid may be used as a drilling fluid by itself or i n
15 conjunction with other standard additives such as clays, emulsifiers,
gallants, and weighting agents. Typically, these additives comprise
between about 0 and about 30 volume percent of the drilling fluid.
Alternately, the HHH Fluid may be used as a rate of
penetration enhancer in drilling fluids having a continuous aqueous
2o phase. In this situation, the HHH Fluid comprises between about 1 and
about 15 volume percent of the drilling fluid, and preferably, between
about 1 and about 2 volume percent. The remainder of the drilling fluid
is made from water and other standard additives known in the art.
Additionally, the HHH Fluid may be used as a spotting fluid
2s to help dislodge downhole drill bits. In this situation, the spotting fluid
comprises between about 50 and about 90 volume percent of the HHH
Fluid, and about 10 to about 50 volume percent of additives such as
emulsifiers, viscosifiers, surfactants and brine.
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The HHH Fluids may also be used as an additive to internal
or linear olefins (for example C12 C1$ internal or linear olefins of low
viscosity that makes the linear or internal olefin suitable as a formulation
for use in drilling fluids. It is known in the art to use internal or linear
olefins as drilling fluids (for example see US Patent No. 5,589,442 to Gee et
al., discussed above). However, these fluids are very expensive to
manufacture, particularly compared to the manufacture of the HHH
Fluids of the present invention. The addition of the HHH Fluid to
internal olefins, decreases the cost of the resulting drilling fluid, and
1o maintains or decreases the toxicity of the resulting drilling fluid.
The internal or linear olefins preferably include one or more
olefins having a between 12 and 18 carbon atoms. More preferably, the
olefins are a blend of olefins having between 16 and 18 carbon atoms. The
amount of the olefin component in the hydrocarbon blend is preferably
1s in the range of about 5 to about 75 volume percent of the blend. More
preferably, it is from about 10 to about 70 volume percent of the blend.
Most preferably, the olefin is from about 40 to about 60 volume percent of
the blend.
20 Example 1
Two drilling fluids were obtained by subjecting a
feedstock to sequential hydrotreating, hydroisomerization and
hydrogenation steps. The resultant fluids were tested to determine
various properties. The properties and the test method are set out i n
2s Table 1:
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Test Method Sample 1 Sample 2
s Color ASTM D1500 <0.5 <0.5
Color Visual Water White Water White
Odor None None
Viscosity~40C, cSt ASTM D445 3.95 2.74
ViscosityC~3100C, cSt ASTM D445 1.44 1.13
1o Density,15C, kg/L ASTM 4052 0.828
Pour Point, C ASTM D97 <-51 <-51
Flash Point, C ASTM D92 130 103
Saturates, wt% PCM 528 100 100
Paraffins, wt% PCM 528 100 100
~ s Aromatics, wt% PCM 528 0 0
Carbon Distribution ASTM D2887 C12 Czo C
As can be seen from the foregoing table, the drilling fluid
2o according to the instant invention had an aromatics level below 0.001 wt
%, and a pour point of less than -51°C. Accordingly, such fluids are
highly
beneficial for use in cold environments where conventional fluids tend
to congeal as opposed to disbursing.
2S ~x~ple 2
The fluid from Example 1, Sample 1 was subjected to a series
of tests to determine its toxicity, biodegradability and pollution potential.
i
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14
The fluid was tested based upon standards used in North America as well
as Europe. The results of the tests are set out in Table 2:
T~ < -
t
Results C
Europ..n PMCC6A m.fAod>1000 >t000
t9ib
1
Fneh Wehr ~~ North EP8 1IltM11
M~ian
>A00.000
Fbh
i~ W~ ~, ~ ~ Naefh EPS llRwtlll
Am.eian
Nol l.w.l
Aeerh. ALHn. Noe. ECSOe7~h.Ewop.en ISOVpIB t025>>1000 >t000
mpll
8k
l
(
.
ston.my
1901fC1171
~ E. ~ E Asaco newt
vEia~oN
~
Cap.pod (Aeaeu. ~ >Z000 >Z000
S.dkn.nt R.Work.r,1C30Ai0deys.m Ewop..nPARCOM 1996
tal2.~ >tt>DO
~o~Pod (Copih~
~ 8~ L. ~b't Narth EPIVEOOI1-90.OZ'7F>500
wtwrt.w,t Mtaian 000
t
. ~y, ,
opw emn,~
N~M~i~n EPS tIRAll~1Pass Pay
Blodearsdabilitv
~~h. eR.r 26 A.ys. !L Euopm Modw.d 8tum
Tat
66.1 6p
oECO ~s
Poiltttlott Potentlsl
Sh.M T.d NaM Mf.AanEPA proboa p
py
(tee 40
anptw
t Pstt
11g
CA 02300659 2000-03-10
The solid phase biodegradeability and sediment toxicity of
two samples of a blend of a hydroisomerized paraffin and a C16 Cls
internal olefin were tested to determine whether they comply with US
s EPA requirements. The results are shown in Table 3:
Component/Test Sample 1 Sample 2
1o IA35, wt%(1) 50 0
Clb Cl$ IO, wt%(2) 50 100
Sediment Toxicity,
LC50, ppm (3) >5021 4098
is
Solid Phase Biodegradability,
after 112days (3) 47 39
(1) IA35~ - a hydroisomerized C12 Czo paraffin
(2) IO - Internal Olefin
(3) Sediment Toxicity and Solid Phase Biodegradability test protocols are
described in 40 CFR 435, Vol 64, No 22, February 3, 1999
This example shows that the addition of an HHH Fluid
component to an internal olefin reduces the toxicity and increases the
biodegradability of the resultant drilling oil.
