Ethers

Details Ethers Ethers

1998-04-13

2001-06-05

Tucker, Philip (Department: 1712)

Earth boring, well treating, and oil field chemistry

Earth boring

Contains organic component

C568S625000, C507S145000

Reexamination Certificate

active

06242389

ABSTRACT:

The present invention relates to ethers, in particular glycol ethers, and their uses in aqueous drilling muds.
Drilling fluids are used in the drilling of wells, such as oil or gas wells. They act as lubricant for the drilling process e.g. drilling bit, and remove the drill cuttings. The fluid is injected down the drillstring to the drill bit and removed whereupon it suspends the cuttings and carry them back to the surface, usually in the annulus between the outside of the drillstring and the well wall. At the surface, the cuttings are separated and the mud reused. The fluid is also usually weighted to increase its density in order to maintain a desired pressure down hole; the weighting can be achieved with insoluble solids such as barite or soluble solids such as alkali and alkaline earth metal salts e.g. halides.
Initially oil based fluids or muds (OBM) were used, but increasingly water based “muds” (WBM) are preferred as these can contribute less of an environmental problem than OBM. But WBM have a problem as the passage of the fluid up the outside of the drillstring can cause swelling of formation material such as clay or shale and its removal thereby enlarging the hole. To reduce this, shale inhibitors may be added to the WBM. Our EPA-495579 describes a WBM comprising a glycol or glycol ether, and a potassium salt in amount of 5-50ppb (pounds per barrel) (i.e. 14.3-143 g/l); these WBM have improved shale inhibition.
But potassium salts may have environmental disadvantages in relation to their effect on marine fauna so in some locations their level of use may be curtailed. However, we have found that replacement of the potassium chloride in the compositions of EP 495579 by other alkali or alkaline earth metal halides significantly reduces the shale inhibition activity.
Glycol ethers may now be found which can give at least as good shale inhibition effect in combination with alkali metal and alkaline earth metal halides as with potassium chloride. By this means the same base glycol ether can be used in locations allowing or not allowing potassium chloride, thereby reducing inventory costs.
The present invention provides a glycol ether block copolymer or mixture thereof of the formula I
R—O—[[—R
1
O]
m
[—R
11
O]
n
[—R
111
—O]
p
]H  I
wherein the —R
1
O and —R
11
O groups may be in either order attached to the R—O group, and the R
111
group, if any is spaced from the RO group by the R
11
O group and R
1
O group, and is different from the group R
11
or R
1
O to which it is bonded directly, R is an organic group e.g. a hydrocarbyl group, R
1
is an ethylene group, each of R
11
and R
111
, which are the same or different is a propylene or butylene group or R
111
may be an ethylene group, in is 1.0-10 or preferably is an average of 1.0-10, while n is 1.0-10 or preferably is an average of 1.0-10, p is 0 or an average of 0.5-5 and the sum of in and n is at least 3.0.
The group R may be an organic group of 1-12 carbons, in particular an organic hydrocarbyl group, especially an alkyl, group e.g. of 1-8 or 2-6 especially 1-4 carbons, an alkenyl group e.g. of 2-8 carbons, a cycloalkyl group e.g. of 5-7 carbons, an aryl group e.g. of 6-9 carbons, or aralkyl group e.g. of 7-10 carbons. The alkyl and alkenyl groups may be branched but are preferably linear.
Examples of the alkyl group are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec butyl, n-amyl, n-hexyl or noctyl while examples of the alkenyl group are vinyl, allyl and crotonyl. Examples of cyclo alkyl are cyclopentyl and cyclohexyl, example of aryl are phenyl, o-, m- or p- tolyl and xylyl, and examples of aralkyl are benzyl and 2-phenylethyl. The group R
1
is an 1,2-ethylene group. The group R
11
or R
111
may be a 1,3-propylene or 1,2-propylene (which is preferred) or 1,4-butylene or 1,2-butylene (i.e. 2-ethyl-1,2-ethylene or 1,3-butylene), while R
111
may also be a 1,2-ethylene group.
In the block copolymers of formula 1 there are at least one R
1
O group and at least one R
11
O group, and a totality of at least 3 R
1
O and R
11
O groups; thus there may be a block of at least 2 R
1
O (or R
11
o) groups joined to at least 1 R
11
O (or R
1
O) groups respectively, preferably a block of at least 2 R
11
O (or R
1
O) groups. Thus in formula 1, (R
1
O)
m
preferably denotes a block of R
1
O groups bonded together, or (but preferably and) (R
11
O)
n
denotes a block of R
11
11
O groups bonded together.
In the copolymer, m is (or in the mixture thereof m is an average of) 1.0-10 e.g. 2.0-10, such as 2.5-5 or 2.5-4 especially 3-3.5. Most preferably the average m is derived from mixtures of individual copolymers, at least one of which preferably the majority of which and especially substantially all of which contain an integer value of m in the range 1-10. n is (or in the mixture thereof n is an average of) 1.0-10 e.g. 2-10 or 2-8 such as 2-6. Most preferably the average n is derived from mixtures of individual copolymers, at least one of which preferably the majority of which and especially substantially all of which contain an integer value of n in the range 1-10. p is 0 or an average of0.5-5.0. The ratio ofin to n may be 0.2-5:1, but is preferably 0.3-3:1 such as 0.4-2.4:1 especially 0.5-1.5:1.
The sum of m and n, or m, n and p (and especially the sum of the average m and average n, or sum of average m, average n and average p) may be 3-15, in particular 3-12, especially an average of 4-12 such as 4-10 or 5-8. The average molecular weight of the glycol ether may be 200-900, such as 250-600. The cloud point of the glycol ether in 3% (by weight) solution in distilled water, is usually more than 35° C. or 40° C. e.g. 40-100° C.
Particularly preferred are glycol ethers II of formula I with R as linear alkyl of 3-5 carbons especially 3 or 4, R
1
O bonded directly to RO—, R
11
as 1,2-propylene m as 2.5-4, e.g. 3-3.5, p as 0 and n as 2.0-6.0, such as 2.0-2.8 or especially 2.8-5.0 or 3.8-5.0. Preferred average molecular weights for said glycol ethers II are 300-500 such as 300-360 or 360-480 especially 420-480, while preferred values for m:n are 1.5-0.5:1, such as 1.5-1.1:1 or especially 1.1-0.6:1 such as 0.85-0.6:1, and preferably the sum of m and n is 5-8, in particular 5-6 or 6-8, especially 7-8.
The glycol ether may be present as a single molecule but is usually as a mixture of glycol ethers, especially with one particular R group and a range of numbers of one of the groups R
1
O or R
11
O which is spaced from the RO group by the other of the R
11
o and R
1
O. That other group may be present in a substantially single number e.g. 3 or 4, or may be itself in a range of numbers such as 2.5-6. The glycol ethers may be made (according to a further aspect of the invention) by stepwise reaction of a hydroxylic compound of formula ROH, with an alkylene oxide of 2-4 carbons of formula R
1
O or R
11
O, e.g. ethylene oxide, and then after reaction is substantially complete e.g. for the number of R
1
O (or R
11
O) units to be reacted with ROH, then the reaction product is reacted further with a second different alkylene oxide of 2-4 carbon atoms of formula R
11
O or R
1
O respectively e.g. propylene oxide, again until reaction is substantially complete. The alkylene oxide reactions are preferably performed in the presence of a catalyst e.g. a basic catalyst such as an alkali metal hydroxide, alkoxide (e.g. of 1-6 carbons such as methoxide or ethoxide) or carboxylate (e.g. alkanoate of 1-6 carbons such as formate or acetate) especially in weight amount of 0.01-10% by weight of the hydroxylic compound ROH such as 0.05-1%, or in weight amount of 0.01-5% by weight of the total of hydroxylic compound and alkylene oxide The stepwise reaction tends to produce glycol ethers with a wide range of numbers of —R
1
O— and —R
11
O groups.
Alternatively according to a process which is a second aspect of the invention, the hydroxylic compound ROH may be reacted with the first alkylene oxide to give a range of products with for example 1-4 alkyleneoxy units, and then by distillation the products with 1, o

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