Oxazolines of 2-(alkylthio)succinic acids as an additive for drilling muds

Aqueous drilling muds are improved in lubricity by the presence of at least an effective amount of an oxazoline of a C.sub.6 to C.sub.50 2-(alkylthio)succinic acid or anhydride.

This invention relates to aqueous drilling fluids. More particularly, this 
invention relates to aqueous drilling fluids having incorporated therein a 
minor amount of an oxazoline of 2-(alkylthio) diacids which are especially 
effective as stable lubricity modifiers for drilling fluids. In another 
embodiment this invention is directed to an improved drilling operation 
employing the modified drilling fluids described above. 
BACKGROUND OF THE INVENTION 
In a drilling operation, such as in a rotary drilling operation, a drilling 
fluid is forced down the drill string, about the drill bit at the bottom 
of the borehole and then back up to the surface. The drilling fluid 
employed in such a drilling operation usually is an aqueous drilling fluid 
and is compounded of various materials in order to impart certain 
desirable physical and chemical properties to the drilling fluid. For 
example, there is usually incorporated in an aqueous drilling fluid a 
hydratable clayey material, such as a bentonite clay, to impart desirable 
viscosity and gel strength properties to the drilling fluid so as to 
better enable the drilling fluid to carry away the drilling cuttings from 
the bottom of the borehole. Other materials such as weighting agents, 
e.g., barium sulfate, are employed to increase the density of the drilling 
fluid so as to make the drilling operation more effective and safer by 
overcoming the fluid pressure within the formation being drilled. Other 
materials such as water loss improving agents, e.g., 
carboxymethylcellulose, hydrolyzed starch, etc. are added to reduce the 
loss of fluid from the drilling fluid into the formation during the 
drilling operation. Still other materials such as corrosion inhibitors, 
bactericides and drill bit lubricants are incorporated in the drilling 
fluid in order to improve the drilling operation and the drilling fluid. 
Although a wide variety of materials designed to increase the lubricity of 
aqueous drilling fluids have been proposed and used in the field such as: 
vegetable oils including soybean and rice oil; tall oil; sodium salts of 
petroleum sulfonic acids and resin acids (see U.S. Pat. No. 4,064,056); 
polyethoxylated tetralkylacetylenic diols; the reaction products of 
thio-bis-alkanols mono- and di-ester and C.sub.12 -C.sub.50 alkyl succinic 
acid or anhydride (see U.S. patent application Ser. No. 277,053, filed 
June 24, 1981 of common assignee); and, C.sub.1 -C.sub.31 thioglycolic 
acid oxazolines (see U.S. patent application Ser. No. 428,826), filed 
Sept. 30, 1982 of common assignee), it remains essential that lubricity of 
said drilling fluids be further improved to reduce the energy requirement 
of said drilling and abrasion of the drilling equipments. 
It is therefore an object to provide an additive composition for drilling 
fluids that reduces the drilling torque. 
SUMMARY OF THE INVENTION 
It has been discovered that the addition of a minor amount of mono- or 
bis-oxazoline of an alkylthiosuccinic acid or anhydride and mixtures 
thereof, formed by the reaction of (a) a 2-(alkylthio) succinic acid or 
anhydride or mixtures thereof wherein the aliphatic hydrocarbon group 
contains a total of from 6 to 50, preferably 8 to 30, optimally 14 to 22, 
carbon atoms; with (b) 1 to 2 moles, per mole of the thiosuccinic acid or 
anhydride of a 2,2-disubstituted-2-amino-1-alkanol containing a total of 4 
to 8 carbon atoms to an aqueous drilling fluid substantially increases the 
lubricity of said drilling fluid as measured, for example, by torque 
reduction. 
Useful are aqueous drilling fluids containing from 0.1 to 10, preferably 
0.5 to 5, optimally 1 to 3, pounds per barrel of drilling fluid of a mono- 
or bis-oxazoline obtained from an alkylthiosuccinic acid or anhydride 
reacted with from 1 to 2 moles of said amino alkanol. These oxazolines 
have the structural formula: 
##STR1## 
where R represents an alkyl group of 6 to 50 carbons and X is selected 
from the group consisting of an alkyl or hydroxyalkyl group and preferably 
at least one of the X substituents being a hydroxy alkyl group of the 
structure --(CH.sub.2).sub.n OH where n is 1 to 3. 
DETAILED DESCRIPTION OF THE INVENTION 
As used herein, the term "monooxazoline" refers to products made from 
equimolar proportions of said thiosuccinic acid or anhydride and amino 
alkanol, that is, one free carboxyl group remains, while the term 
"bis-oxazoline" as used herein refers to those products wherein each 
carboxyl group of the 2-(alkylthio)succinic acid or anhydride is converted 
to oxazoline by reaction with the amino alkanol. 
The 2-(hydrocarbylthio)succinic acids or anhydrides are known in the art 
and the commonly used anhydride may be represented by the formula: 
##STR2## 
wherein R is C.sub.6 -C.sub.50 aliphatic group, such as in alkyl, alkenyl, 
isoalkyl, isoalkenyl or cycloalkyl hydrocarbyl groups. Mercaptans derived 
from oligomers containing 6 to 50 carbon atoms are also suitable as the 
2-alkyl group such as oligomers of C.sub.2 -C.sub.5 monoolefins such as 
isobutene. 
The aliphatic hydrocarbyl group may be an unsubstituted hydrocarbon group 
or it may contain substituents such as chlorine, bromine, phosphorous or 
oxygen which will not affect the utility of the final mono- or bis 
oxazoline product. 
These compounds may be prepared by the reaction of maleic anhydride with 
thiols using techniques known in the art. The 2-(alkylthio)succinic acids 
are readily produced by hydrolysis of the corresponding anhydride. 
Especially preferred in preparing the novel mono- and di-ester compounds 
of the present invention are 2-(C.sub.18 -C.sub.22 alkylthio)succinic 
anhydrides, such as 2-(octadecylthio)succinic anhydride. 
The term amino-alkanol as used herein is understood to represent those 
oxazoline-forming nitrogen compounds, i.e., a 
2,2-disubstituted-2-amino-1-alkanol containing a total of 4 to 8 carbon 
atoms, and which can be represented by the formula: 
##STR3## 
wherein X is an alkyl or hydroxy alkyl group and preferably at least one 
of the X substituents being a hydroxy alkyl group of the structure 
--(CH.sub.2).sub.n OH, wherein n is 1 to 3. 
Examples of such 2,2-disubstituted amino alkanols, include 
2-amino-2-methyl-1-propanol (hereinafter designated also as AMP), 
2-amino-2-methyl-1,3-propanediol (hereinafter designated also as AMPD), 
2-amino-2-hydroxymethyl-1,2-propanediol (also known as 
tris-hydroxyaminomethane or THAM), 2-amino-2-ethyl-1,3-propanediol 
(hereinafter designated also as AEPD), etc. Because of its effectiveness, 
availability, and cost, the THAM is particularly preferred. 
By sharp contrast, it has been found that other amino alcohols such as 
ethanolamine, propanolamine and butanolamine which lack 
2,2-disubstitution, do not afford oxazoline products. 
The formation of the novel oxazoline materials in substantial yield, can be 
effected by adding from one to two moles of the aforesaid 
2,2-disubstituted-2-amino-1-alkanol per mole of the 2-(alkylthio)succinic 
anhydride with or without an inert diluent, and heating the mixture at 
100.degree.-240.degree. C., preferably 170.degree.-220.degree. C., until 
reaction is completed as indicated by infrared analysis of the product 
showing maximal absorption for oxazoline and/or by the cessation of 
evolution of water. 
Although not necessary, the presence of small amounts such as 0.01 to 2 
wt.%, preferably 0.1 to 1 wt.%, based on the weight of the reactants, of a 
metal salt can be used in the reaction mixture as a catalyst. The metal 
catalyst can later be removed by filtration or by washing a hydrocarbon 
solution of the product with a lower alcohol, such as methanol, ethanol, 
isopropanol, etc. or an alcohol/water solution. 
Alternatively, the metal salt can be left in the reaction mixture, as it 
appears to become stably dispersed, or dissolved, in the reaction product, 
and depending on the metal, it may even contribute performance benefits to 
the drilling mud. 
Inert solvents which may be used in the above reaction include hydrocarbon 
oils, e.g. mineral lubricating oil, kerosene, neutral mineral oils, 
xylene, halogenated hydrocarbons, e.g., dichlorobenzene, tetrahydrofuran, 
etc. 
Metal salts that may be used as catalysts in the invention include 
carboxylic acid salts of Zn, Co, Mn and Fe. Metal catalysts derived from 
strong acids (HCl, sulfonic acids, H.sub.2 SO.sub.4, HNO.sub.3, etc.) and 
bases, tend to diminish the yield of the oxazoline products and instead 
favor imide or ester formation. For this reason, these strong acid 
catalysts or basic catalysts are not preferred and usually will be 
avoided. The carboxylic acids used to prepare the desired catalysts, 
include C.sub.1 to C.sub.18, e.g., C.sub.1 to C.sub.8 acids, such as the 
saturated or unsaturated mono- and dicarboxylic aliphatic hydrocarbon 
acids, particularly fatty acids. Specific examples of such desired 
carboxylic acid salts include zinc acetate, zinc formate, zinc propionate, 
zinc stearate, manganese(ous) acetate, iron tartrate, cobalt(ous) acetate, 
etc. Completion of the oxazoline reaction can be readily ascertained by 
using periodic infrared spectral analysis to observe maximal oxazoline 
formation (C.dbd.N absorption band at 6.0 microns) and/or by the cessation 
of water evolution. 
The amount of the mono- or bis-oxazoline added to the well drilling fluid 
may be only a minor but sufficient amount to substantially increase the 
lubricity of the said drilling fluid as measured, for example, by torque 
reduction. The amount to be added to the well drilling fluid is in the 
range of from 0.1 to 10, preferably 0.5 to about 5, pounds per barrel of 
drilling fluid, optimally from about 1 to about 3 pounds per barrel. 
It has been found that the drilling fluids of the present invention exhibit 
a high degree of lubricity and little or no abnormal distortion of mud 
properties. 
The additives are generally introduced into the drilling mud as a 
hydrocarbon solution containing broadly from at least 2 to 99, preferably 
30 to 70, optimally 40 to 50, weight % additive based on the total weight 
of the solution. The additive can also be introduced neat, i.e., only 
additive, in the drilling mud when significantly dispersible in the 
aqueous mud. If desired, other additives such as water loss improving 
agents, corrosion inhibitors, bactericides, etc. can be introduced as part 
of the additive-solvent package into the drilling mud. 
Suitable hydrocarbon solvents include: mineral oils, particularly those 
paraffin base oils of good oxidation stability with a boiling range of 
from 200.degree. C. to 400.degree. C. such as Mentor 28.RTM. sold by Exxon 
Chemical Americas, Houston, Tex.; diesel and gas oils; and heavy aromatic 
naphtha. Preferred are those above-referenced paraffin base oils.

The invention is further illustrated by the following Examples which are 
not to be considered as limitative of its scope. 
EXAMPLE 1 
Preparation of the monooxazoline from tris-(hydroxymethyl)amino methane 
(hereinafter THAM) and 2-(octylthio)succinic acid. 78.6 g (0.3 mole) of 
2-(octylthio)succinic acid, and 36.39 (0.3 mole) of THAM were added to a 
reaction flask containing 20 ml of xylene. The mixture was heated to 
reflux until all of the water of reaction was collected in the moisture 
trap. The xylene was removed and a glossy type solid was obtained. The 
infrared spectrum of the solid featured intense ester and oxazoline 
absorption bands. Analytical data supports and oligomeric ester of the 
following monomeric structure 
##STR4## 
EXAMPLE 2 
This example shows the preparation of a bis-oxazoline derived from the 
reaction of 2-amino-2-ethyl-1,3-propanediol (hereinafter AEPD) and 
2-(octadecylthio)succinic acid. 68.8 g (0.17 mole) of 
2-(octadecylthio)succinic acid and 40.7 g (0.34 mole) of AEPD were added 
to 200 ml of xylene in a reactor fitted with a Dean Starke water trap. The 
mixture was refluxed until all the water of reaction was collected in the 
moisture trap (about 3 hours). The xylene was removed and an oily 
substance was obtained. A white solid formed upon cooling at room 
temperature. The infrared spectrum of the crude solid showed an intense 
oxazoline absorption band at 6.0 microns. It analyzed for 65.95% C, 
10.66%H, 5.26% N and 5.25% S. Theory requires 67.60% C, 10.56%H, 4.93% N 
and 5.63% S. Spectral and analytical results are equivalent to 
n-octadecylthioethane-1,2-diyl-bis (5-ethyl-5-hydroxymethyl-2-oxazoline) 
which is believed to have the following structure. 
##STR5## 
EXAMPLES 3-16 
Numerous other mono and bis oxazolines were prepared according to the 
procedures of Examples 1 and 2. The reactants are described by name 
whereas the product is inferred by reference to Example 1 or 2 and 
physical data in the following Table I. 
TABLE I 
__________________________________________________________________________ 
Process 
Ex. 
2-(alkylthio)sucinnic acid Reactants 
alkanol 
Acid to Alkanol Mole Ratio 
To Ex.According 
##STR6## 
__________________________________________________________________________ 
3 octyl THAM 2:1 2 brown glassy solid, 
mp 33-40.degree. C. 
4 octyl THAM 1:1 1 brown glassy solid 
5 octyl AMPD 2:1 2 heavy slight brown oil 
6 octyl AMP 2:1 2 dark brown thick liquid 
7 octyl AEPD 2:1 2 light brown oil 
8 octyl AEPD 1:1 1 light brown oil 
9 octadecyl THAM 2:1 2 gold waxy solid, 
mp 57-69.degree. C. 
10 octadecyl AMPD 2:1 2 heavy brown oil 
11 octadecyl AMP 2:1 2 brown waxy solid 
12 octadecyl AEPD 2:1 2 brown waxy solid 
13 eicosanyl THAM 2:1 2 white solid 
14 eicosanyl AMPD 2:1 2 white solid 
15 eicosanyl AMP 2:1 2 oil/waxy solid 
16 eicosanyl AEPD 2:1 2 waxy solid 
__________________________________________________________________________ 
AMP = 2amino-2-methyl-1-propanol 
AMPD = 2amino-2-methyl-1,3-propane diol 
AEPD = 2amino-2-ethyl-1,3-propane diol 
THAM = trishydroxymethylaminomethane 
EXAMPLES 17-20 
The lubricity activity of the formulations of the invention are shown in 
Table II following by comparison with a base mud. The base mud is prepared 
from 20 to 25 pounds of bentonite [5 to 7 wt.%], 4 to 6 pounds of 
lignosulfonate [1 to 2 wt.%] and sufficient sodium hydroxide to adjust the 
pH to 9.5 to 10.5 per barrel of water. This is the basic drilling mud to 
which the lubricity additives taught here are added to produce the 
drilling muds of much enhanced lubricity as seen from the following Table 
II. 
The rheology data of Table I was determined on a Fann model 35 Viscosimeter 
purchased from Fann Industries of Houston, Tex. The torque data was 
determined on a Baroid Lubricity Tester available from the Baroid Division 
of N.L. Industries, Houston, Tex. 
Although the additive product of Example 2 showed the greatest torque 
reduction, the product of Example 9, i.e. 
n-octadecylthioethane-1,2-diyl-bis-[5,5-bis(hydroxymethyl)-2- oxazoline] 
and the product of Example 11, i.e. 
n-octadecylthioethane-1,2-diyl-bis(5,5-dimethyl-2-oxazoline) both showed a 
lubricity activity level characteristic of the products of the invention 
disclosed herein. 
Although the utility of the compounds of the invention has been directed to 
lubricity enhancement of drilling muds, each has utility requiring 
activity at a metal surface. The property of surface activity of these 
compounds and the thermal decomposition byproducts, e.g. the mono 
oxazoline species produces byproduct carboxyl moieties toward metal 
surfaces as film formers favors the use of each, alone or in combination 
in amounts ranging from 10 to 100 parts per million as a film former in a 
corrosion inhibitor formula for heat exchanger fluids in refinery 
equipment, in metal rolling mills as an anti spotting additive and in 
metal cutting fluids because of surface passivation and/or oxygen 
pacification. 
The compounds of the invention are particularly useful as oxidation 
inhibitors to protect fluids such as refinery feed stream subjected to 
high temperatures in heat exchangers. It is believed that the combination 
in one molecule of sulfur (provides oxidation inhibition) and the hydroxy 
oxazoline (provides surface activity) has special value in applications 
where oxidative degradation is a problem. In these applications, the 
compounds of the invention bring the oxidative inhibition of the sulfur to 
the region of maximum oxidative degradation which occurs adjacent to the 
metal surface. 
POST TREATMENT OF COMPOUNDS OF INVENTION 
Treatment of the reaction products at 2-(octadecylthio) glycolic acid and 
0.5 to 2 molar equivalents of tris-hydroxymethyl amino methane (THAM), for 
example, with tributyl phosphite affords an oxazoline phosphite ester 
derivative containing 0.1 to 1 wt.% phosphorous with antioxidant 
properties. 
Similarly, the boration using boric acid or ester of oxazolines from the 
reaction of 2-(octadecylthio) glycolic acid with 0.5 to 2 molar 
equivalents (THAM) gives more borate esters containing from 0.1 to 1 
weight percent of boron which feature anticorrosion activity in refinery 
feedstreams. 
Finally, the oxyalkylation of the oxazolines of the present invention with 
alkylene oxides provides novel derivatives adaptable to a variety of 
surfactant application, which require oxidation and corrosion control in 
oil field chemical applications. 
This invention in its broader aspect is not limited to the specific details 
shown and described, and departures may be made from such details without 
departing from the principles of the invention and without sacrificing its 
chief advantages. 
TABLE II 
______________________________________ 
Ex- Additive 
am- Lubricity 
Conc..sup.1 
Plastic 
Yield % Torque.sup.3 
ple Additive Lb/BBl Viscosity 
Point Gel.sup.2 
Reduction 
______________________________________ 
17 None -- 55 3 2-4 -- 
18 Product 2 46 14 3-4 46.8 
Ex. 2 
19 Product 2 48 13 2-3 54.7 
Ex. 9 
20 Product 2 64 35 4-7 40.7 
Ex. 11 
______________________________________ 
.sup.1 All additives added as a 50% concentrate in paraffinic hydrocarbon 
.sup.2 Deflection on Viscosimeter at rpm, initially and after 10 minutes 
.sup.3 As measured by Baroid Lubricity Tester relative to material of 
Example 17