DESC:FIELD OF THE INVENTION
The present invention relates to powdered lubricant additive compositions comprising a liquid lubricant blended with inert solid substrate. The solid lubricant additive compositions thus obtained are advantageously employed in drilling fluids. This invention is a modification of Indian Patent Application no.1468/MUM/2015 filed on April 8, 2015 and titled “Solid Invert Emulsion Drilling Fluid Additives, Methods for Preparation and Use in Oil-Based Drilling Fluids”.

BACKGROUND OF THE INVENTION
Drilling fluids are used during drilling of an oil well in rotary drilling. Two types of drilling fluids are mainly utilized, water based drilling fluids and oil based drilling fluids. Water based drilling fluids utilise water as base fluid and in oil based drilling fluids, oil is used as the base fluid. Various types of water based and oil based drilling fluids are developed and utilized in drilling operations.
Drilling fluids have many functions, such as removing drill cuttings from the drill area and carrying them to the surface where they can be separated. Drilling fluids also form a filter cake to seal and prevent fluid losses to stabilize the well bore. Drilling fluids additionally provide mud weights to balance the differential pressure, cool the drill bits and provide lubricity. Various types of additives are used to impart these properties to drilling fluids.
Lubricants are added to drilling fluids to reduce the torque and drag caused by friction between drill string, drill bit and formation. Many types of lubricants have been developed and utilised in drilling fluids. Lubricants can either be in solid or liquid form. Liquid lubricants such as hydrocarbons, fatty acid esters, fatty acids, surfactants and many other organic compounds are developed and used in the manufacture of conventional lubricant additives. Solid lubricants such as graphite, hollow glass beads, spherical solid particulates and polymers have been developed and utilized in drilling fluids. However, solid lubricants have many limitations, such as stability under pressure of hollow glass beads and problems in fluid formulations in graphite due to high surface area. Additionally, the size of the particulates creates problems for sifting with screen shakers. Another disadvantage noted is that large amounts of solid lubricants are required to impart reasonable lubricity to drilling fluids, thereby increasing the cost of production.
Liquid lubricants have their own shortcomings such as, handling in cold weather and logistic and environmental impacts.
When liquid lubricants containing fatty acids, sulfurized fatty acids, soaps of sulfurized and non-sulfurized fatty acids and esters of fatty acids are contaminated with monovalent or divalent ions, insoluble alkali monovalent or divalent ion soaps are formed and separate from the drilling mud. The greasing out of the alkali metal ion soap causes severe impediments to the control of the mud. If such greasing out occurs in drilling muds containing weighing agents, the greasing out causes accumulation of the weighing agent, which then sinks to the bottom of the mud pit, and is lost from the mud system. The resulting loss of mud density may cause blow out of the well.
It is observed that when drilling mud containing monovalent or divalent ions is free of weighting agents, the resulting insoluble soap floats on the surface of the mud in the mud pit. This insoluble calcium soap plugs the shale shaker and thereby interferes with the separation of the cuttings from the drilling mud. This further results in the extreme pressure additive not being drawn up by the mud pumps and incorporated in the drilling mud for circulation to the bit for lubrication.
Therefore, there is a need for new and improved lubricants to overcome the limitations of such traditional lubricants.
This invention resides in water based drilling mud compositions containing fatty acids, rosin acids and the sulfurized derivatives of the compounds named above in concentrations sufficient to impart lubricating properties to drilling muds.
With respect to lubricant additives used in water based drilling fluids, various formulations are described in the art.
US3048538 describes a water-base drilling fluid having extreme pressure lubricating properties consisting essentially of water and an extreme pressure lubricant additive selected from the group consisting of fatty acids having at least 8 carbon atoms per molecule, sulfurized fatty acids having at least 8 carbon atoms per molecule, alkali metal soaps of fatty acids and alkali metal soaps of sulfurized fatty acids, available calcium ions in a concentration above about 150 parts per million high enough to form insoluble curds of calcium soap, and a non-ionic surface active agent selected from the group consisting of polyoxyethylene derivatives of alkyl phenols, polyoxyethylene derivatives of alkyl glycols, and polyoxyethylene derivatives of anhydroalkitol esters in a concentration adequate to disperse the calcium soap in the drilling fluid.
Though the lubricant additive of US3048538 is meant to disperse the calcium soap in the drilling fluid, the use of surface active agents to prevent greasing could result in foaming and be detrimental to the stability of the drilling fluid. Further, US3048538 does not describe a powder-form lubricant additive as the present invention.
US4802998 describes powder-form lubricant additives for water-based drilling fluids which include highly dispersed silica’s, one or more fatty acid alkyl esters of the formula R.sup.1 COOR.sup.2 (I) and, optionally, other additives known for lubricating purposes, and the use of these powder-form additives in drilling fluids for oil well and mine drilling.
Though the lubricant additive of US4802998 is in powder-form, it contains fatty acid alkyl esters and may contain metal soaps, both of which are not known to cause greasing out of the drilling fluid. The powder-form lubricant additive of US4802998 in effect, does not provide solutions to the problem of greasing out that is solved by the present invention.
The powdered lubricant of the present invention is particularly effective in a drilling mud composition that contains monovalent or divalent ions enough to react with the lubricating additive and form dispersible and non-greasing type insoluble soaps.
This invention also contemplates inert filler acting as a dispersing agent to avoid formation of greasing and cheesing.
The present invention helps in dispersion and avoidance of greasing thereby eliminating the conventional use of surfactants.

OBJECTS OF THE INVENTION
1) To provide powdered lubricant additives for oil field application
2) To provide powdered lubricant additives for drilling operation.
3) To provide powdered lubricant additives for water based drilling fluid.
4) To provide powdered lubricant additives for water based drilling fluid containing inorganic salts.
5) To provide powdered lubricant additives for water based drilling fluid containing divalent cations.
6) To provide powdered lubricant additives which are dispersible in divalent ions without cheesing and greasing.
7) To provide powdered lubricant additives that eliminates the use of surfactants to avoid greasing of water based drilling fluids.
8) To provide powdered lubricant additives which are essentially free from fatty esters and metal soap.
9) To provide powdered lubricant additives which are stable under pressure.
10) To provide powdered lubricant additives which obviate the deficiency of conventional solid lubricants due to high surface area.
11) To provide powdered lubricant additives that do not need to be used in large quantities thereby reducing the cost of production of the drilling fluid.
12) To provide powdered lubricant additives which overcome the disadvantage of liquid lubricants, such as handling in cold weather and logistic and environmental impacts.

SUMMARY OF THE INVENTION
The invention relates to powdered lubricants for water based drilling fluids. Conventional liquid lubricants containing particularly divalent ions have the tendency to grease out. The powdered lubricants have excellent dispersion properties and hence do not grease out, when added to the drilling mud in the concentrations, preferably of the order of about 3% or less. The powdered lubricant is a combination of inert fillers with fatty acids that are essentially free from fatty acid esters and metal soaps and have organic acids containing C10-C24 alkyl groups fatty acids. The improved lubricating properties of the drilling muds result in greatly increased life of the rotary drilling bits and marked reduction in torque required to rotate the bit. Solid powdered additives compositions greatly reduce transportation costs and simplify the logistics and environmental concerns associated with shipping large volumes of liquids and overcome the pour point issues associated with liquid additives.

STATEMENT OF THE INVENTION
The present invention describes a powdered lubricant additive that does not grease or cheese out in the presence of mono, di or trivalent ions in water based drilling fluids. The powdered lubricant additive includes a combination of fatty acids with inert fillers. The fatty acids are essentially free from fatty acid esters and metal soaps, said fatty acids having organic acids containing C10-C24 alkyl groups fatty acids.
The present invention further envisages a water-based drilling fluid having lubricating properties comprising water, viscosifiers, weighing agents, fluid loss control agents, calcium ions in concentration greater than 150 parts per million and the powdered lubricant additive described above.
The present invention also contemplates a rotary method for drilling a well through calcium-containing formations in which the water based drilling fluid as described above is circulated down the well, said drilling fluid having calcium soaps dispersed therein.

DESCRIPTION OF THE INVENTION
A wide variety of commercially available liquid lubricant additives are suitable for making the solid free-flowing lubricants of this invention. The liquid lubricant additives are known or are generally prepared in accordance with conventional techniques, for instance, when making liquid lubricant, fatty acids and sulfurized fatty acids are used.
The process of manufacturing the liquid lubricants used in the compositions is known in the art.
The embodiments of the invention describe additives in free flowing powdered form that mitigate or eliminate the limitations or problems associated with liquid additives especially that of greasing out of monovalent or divalent ions contained in drilling mud.
The manufacturing process comprises of spraying /mixing different types of liquid lubricant additives individually at elevated temperature to a blend of inert fillers in specific proportions and of particular particle size in a blender for a specified time. The solid powdered additives thus obtained are controlled pulverized to obtain the final particle size that does not alter the performance of each individual additive. The solid lubricant additives obtained are added to drilling fluid compositions yielding drilling muds with improved performance.
Many compositions can be prepared according to this invention. It is contemplated that the ratios of the liquid additives to inert filler can vary depend upon final use and method of preparation. Ratio of the inert filler to the liquid additive in the powdered lubricant may vary from 10:90 to 90:10
It is noted that the lubricant and inert filler just added separately in the water based drilling fluid will still result in greasing.
The present invention envisages a powdered lubricant additive that does not grease or cheese out in the presence of mono, di or trivalent ions in water based drilling fluids. The powdered lubricant is made of (a) fatty acid that is essentially free from fatty acid ester and metal soap and (b) inert filler. The fatty acids are organic acids containing C10-C24 alkyl groups fatty acids which may be chosen from saturated and unsaturated fatty acids or vegetable oil fatty acid or sulfurized vegetable fatty acids or combinations thereof. The inert filler may be chosen from precipitated silica of particle size about 10-180 microns or diatomaceous earth of particle size about 10-200 microns or expanded perlite of particle size about 10-5000 microns or combinations thereof. Preferably, the ratio of the liquid additive to the inert filler in the powdered lubricant varies from 30:70 to 70:30.
The present invention further envisages a water-based drilling fluid having lubricating properties and made up of water, viscosifiers, weighing agents, fluid loss control agents, calcium ions and the powdered lubricant additive of the present invention in concentrations of about 0.25% to about 5% weight/volume of drilling fluid. Preferably the calcium ions are present in concentrations greater than 150 parts per million. Preferably, the powdered lubricant additive is present in concentrations of about 1% to about 3% weight/volume of drilling fluid. The viscosifier may be chosen from bentonite, xanthan gum, clay or polymers. The weighing agent may be barite or hematite or calcium carbonate. The fluid loss reducer may be chosen from starch, carboxy methylated starch, polyanionic cellulose or polymeric fluid loss additive.
The present invention also envisages a rotary method for drilling a well through calcium-containing formations in which the water based drilling fluid of this invention having calcium soaps dispersed therein is circulated down the well and back to the surface and contacted with the drill bits.

Some of the embodiments according to the invention are described as follows:
Embodiment I:- In one embodiment, the present invention is a method of preparing a solid lubricant which is used as an extreme pressure lubricant in water based drilling mud. The method comprises spraying liquid extreme pressure lubricant at temperature of about 70-150°C on inert filler at the rate of about 2-8 LPM.
The method of preparing the solid lubricant involves spraying heated liquid lubricant comprising of a blend of (1) sulfurized fatty acid (2) non-sulfurized fatty acid and (3) a hydrocarbon on inert solid filler, such as precipitated silica of particle size 10-180µm, diatomaceous earth of particle size 10-200 µm or expanded perlite of particle size 10-5000 µm. The mixture is blended, dried and cooled to obtain the solid lubricant that is further pulverized to particle size of about 500 µm to provide the dried lubricant powder.
An illustrative example of a liquid lubricant is Gel EP Torque Reducer which is commercially available from GUMPRO Drilling Fluids Pvt. Ltd.

Embodiment II:- Another embodiment of the present invention is a process for preparing solid general purpose lubricant additive. The method comprises spraying liquid lubricant additive at temperature of about 70-150°C on inert fillers at the rate of about 2-8 LPM.
The method of preparing the solid lubricant additive involves spraying lubricant additive consisting of blend of (1) non-sulfurized vegetable oil and (2) hydrocarbon on inert solid filler such as precipitated silica of particle size 10-180µm, diatomaceous earth of particle size 10-200 µm & expanded perlite of particle size 10-5000 µm. The method further comprises blending, drying and cooling the mixture to obtain the solid lubricant additive which is further pulverized to particle size of about 500 µm to provide the lubricant additive powder.
A commercially available liquid General Purpose Liquid Lubricant additive is Gel GP Lube from GUMPRO Drilling Fluids Pvt. Ltd.

In the present invention lubricant additives are added in the drilling muds in concentration ranging from about 0.25% - 3.0%.
The monovalent or divalent ions causing the formation of the insoluble curds of monovalent or divalent soaps may be added to the drilling mud to give the desired properties. Divalent ions may also have been introduced into the drilling mud as a contaminant as result of penetrating formations or encountering brines.
Laboratory experiments were carried out on drilling mud compositions to determine the effectiveness of dispersants in drilling muds containing monovalent and divalent ions. The test procedure was to prepare a drilling mud and dose it separately with conventional liquid lubricant and the powdered lubricant of the present invention. The resultant drilling mud was tested in each case. The percentage lubricity/torque reduction and greasing out of monovalent and divalent ions was observed for the conventional liquid lubricants and the powdered lubricants of the present invention.
The improved and advantageous properties of the powdered lubricants of the invention are effectively demonstrated by the experiments reported in the ensuing examples.
The following terms/abbreviations used in describing the results of experimentation are explained as follows:
“EPTR” - Extreme Pressure Torque Reducer
“Liquid EPTR” - conventional Liquid Extreme Pressure Lubricant.
“Powder EPTR” - powdered Extreme Pressure Lubricant of the present invention.
“GP Lube”- General Purpose Lubricant
“AHR” - After Hot Rolling temperature.
“Powder GP LUBE” - Powdered General Purpose Lubricant additive of the present invention.
“Liquid GP LUBE” - conventional Liquid General Purpose Lubricant.

Example 1: KCl Mud System
MUD FORMULATION
Hot Rolling For Four Hrs @ 150°F and 250 °F
KCl System
Base Mud Formulation
Sr. No. Product Specific Gravity Gms Ml Wt %
1 Pac LV 1.6 2 1.25 0.36
2 Xanthan Gum 1.6 1.2 0.75 0.21
3 Starch 1.6 2 1.25 0.36
4 CaCO3-50 2.6 8.45 3.25 0.93
5 KCl 2.47 104.39 40.15 11.47
6 Monoethanol Amine 1.00 0.35 0.35 0.10
7 Biocide 1.00 0.35 0.35 0.10
8 Fresh Water 1 302.654 302.654 86.47
Total 421.4 350.0 100.00

Lubricity and Greasing for the above mud system is studied for 1%, 2% and 3% lubricant dosage.
1. Comparison of the Lubricity and Greasing of Liquid V/s Powder Extreme Pressure Torque Reducer(EPTR):-
% Reduction in Lubricity Coefficient
LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR
1% Dosage 2% Dosage 3% Dosage
AHR- 150 °F 80.69 24.02 76.97 59.52 79.26 62.86
AHR-250 °F 80.69 78.74 76.97 76.02 77.04 74.58
Observation on greasing
Greasing Observed No Greasing Greasing Observed No Greasing Greasing Observed No Greasing

Conclusion:-
The lubricity of Powder EPTR which is the powdered lubricant of the present invention, increases with increase in dosage at Hot Rolling Temp of 150 °F whereas at 250 °F the lubricity of the Powdered lubricant is comparable to that of Liquid Lubricant. It is observed that the inert filler acts as a good dispersing agent and the powdered lubricant of the present invention prevents greasing out in the drilling mud.

2. Comparison of the Lubricity and Greasing of Liquid V/s Powder General Purpose(GP) Lube:-
% Reduction in Lubricity Coefficient
LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE
1% Dosage 2% Dosage 3% Dosage
AHR-150 °F 76.96 70.24 80.6 75.00 78.18 68.59
AHR-250 °F 76.25 71.43 80.74 82.85 81.48 76.84
Observation on Greasing
Greasing Observed No Greasing Greasing Observed No Greasing Greasing Observed No Greasing

Conclusion:-
The lubricity of Powder GP Lube which is the powdered general purpose lubricant of the present invention, is comparable to conventional liquid general purpose lubricant. Inert filler acts as a good dispersing agent and greasing is not observed when the powdered general purpose lubricant of the present invention is used.

Example 2: CaCl2 Mud System
MUD FORMULATION
Hot Rolling For Four Hrs @ 150°F and 250 °F
CaCl2 System
Base Mud Formulation
Sr. No. Product Specific Gravity Gms ml Wt %
1 Pac LV 1.6 2 1.25 0.4
2 Tap Water 1 285.897 269.3782 77.0
3 CaCl2 3.1 183.465 59.179 16.9
4 Xanthan Gum 1.6 1.2 0.75 0.2
5 Starch 1.60 2 1.25 0.4
6 Calcium carbonate 50 2.6 4.239 17.69231 5.1
7 Monoethanol Amine 1 0.35 0.35 0.1
8 Biocide 1 0.35 0.5 0.1
Total 479.2 350.0 100
Lubricity and Greasing for the above mud system is studied for 1%, 2% and 3% lubricant dosage.
1.Comparison of the Lubricity and Greasing of Liquid V/s Powder Extreme Pressure Torque Reducer(EPTR) is:-
% Reduction in Lubricity Coefficient
LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR
1% Dosage 2% Dosage 3% Dosage
AHR- 150 °F 27.43 37.07 73.45 38.58 76.11 40.94
AHR-250 °F 29.34 29.89 75.00 40.22 78.26 42.52
Observation on Greasing
Greasing Observed No Greasing Greasing Observed No Greasing Greasing Observed No Greasing

Conclusion:- At 1% dosage, the lubricity of conventional liquid lubricant is comparable to that of the powdered extreme pressure lubricant of the present invention. At 2% and 3% dosage, the lubricity of the powdered lubricant is less than that of liquid lubricant. However, the inert filler acts as a good dispersing agent and greasing is not observed when the powdered extreme pressure lubricant is used.

2. Comparison of the Lubricity and Greasing of Liquid V/s Powder GP Lube:-
% Reduction in Lubricity Coefficient
LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE
1% Dosage 2% Dosage 3% Dosage
AHR- 150 °F 40.71 29.20 30.97 27.43 26.55 23.01
AHR-250 °F 9.78 40.22 7.60 41.30 3.26 39.13
Observation on Greasing
Greasing Observed No Greasing Greasing Observed No Greasing Greasing Observed No Greasing

Conclusion:- Lubricity of Powder GP Lube which is the powdered general purpose lubricant of the present invention, is greater than that of conventional Liquid General Purpose lubricant at Hot Rolling Temperature of 250°F, whereas at 150 °F it is comparable to that of the conventional Liquid General Purpose lubricant . Further, the lubricity remains consistent with varying dosages used. However, there is no greasing observed in the powdered general purpose lubricant since the inert filler acts a good dispersing agent.

Example 3: NaCl Mud System
MUD FORMULATION
Hot Rolling For Four Hrs @ 150°F and 250 °F
NaCl System
Base Mud Formulation
Sr. No. Product Specific Gravity Gms Ml Wt%
1 Pac LV 1.6 2 1.25 0.36
2 Xanthan Gum 1.6 1.2 0.75 0.21
3 Starch 1.6 2 1.25 0.36
4 CaCO3-50 2.6 8.434 3.24 0.93
5 NaCl 2.79 97.054 34.792 9.94
6 Fresh Water 1.00 308.714 308.71 88.20
Total 419.4 350.0 100.00

1.Comparison of the Lubricity and Greasing of Liquid V/s Powder Extreme Pressure Torque Reducer(EPTR) :-
% REDUCTION IN LUBRICITY COEFFICIENT
LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR LIQUID EPTR POWDER EPTR
1% Dosage 2% Dosage 3% Dosage
AHR- 150 °F 76.0 77.2 80.0 72.0 79.5 74.4
AHR-250 °F 77.6 79.6 82.9 79.1 82.9 92.8
Observation on greasing
No Greasing No Greasing No Greasing No Greasing No Greasing No Greasing

Conclusion:-
Lubricity of the powdered extreme pressure lubricant of the present invention is comparable to conventional Liquid extreme pressure lubricant.
2.Comparison of the Lubricity and Greasing of Liquid V/s Powder General Purpose(GP) Lube is:-
% Reduction in Lubricity Coefficient- POWDER GP LUBE
LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE LIQUID GP LUBE POWDER GP LUBE
1% Dosage 2% Dosage 3% Dosage
AHR- 150 °F 82.29 60 83.42 78.49 84.00 83.87
AHR-250 °F 82.19 75 84.25 80.00 84.93 81.25
Observation on Greasing
No Greasing No Greasing No Greasing No Greasing No Greasing No Greasing

Conclusion:-
Lubricity of Powdered general purpose lubricant of the present invention is comparable to conventional general purpose lubricant.
The foregoing description of preferred embodiments of the present disclosure provides illustration and description, but is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure.
,CLAIMS:WE CLAIM:
1. A powdered lubricant additive that does not grease or cheese out in the presence of mono, di or trivalent ions in water based drilling fluids, comprising:
a. fatty acid that is essentially free from fatty acid ester and metal soap, said fatty acid comprising organic acids containing C10-C24 alkyl groups fatty acids; and
b. inert filler.
2. The powdered lubricant additive as claimed in claim 1 wherein the C10-C24 alkyl group fatty acids are selected from a group comprising saturated and unsaturated fatty acids, vegetable oil fatty acid, sulfurized vegetable fatty acids or combinations thereof.
3. The powdered lubricant additive as claimed in claim 1 wherein the inert filler is selected from a group comprising of precipitated silica of particle size about 10-180 microns, diatomaceous earth of particle size about 10-200 microns, expanded perlite of particle size about 10-5000 microns or combinations thereof.
4. The powdered lubricant additive as claimed in claim 1 wherein the fatty acid is present in the range of about 30% to about 70% by weight.
5. The powdered lubricant additive as claimed in claim 1 wherein the inert filler is present in the range of about 70% to about 30% by weight.
6. A water-based drilling fluid having lubricating properties comprising water, viscosifiers, weighing agents, fluid loss control agents and the powdered lubricant additive as claimed in claim 1 and having calcium ions present in concentration greater than 150 parts per million.
7. The water-based drilling fluid as claimed in claim 6 wherein the powdered lubricant additive is present in concentrations of about 0.25% to about 5% weight/volume of drilling fluid, effective to impart lubricity and disperse calcium soaps in the drilling fluid.
8. The water-based drilling fluid as claimed in claim 7 wherein the powdered lubricant additive is present in concentrations of about 1% to about 3% weight/volume of drilling fluid.
9. The water-based drilling fluid as claimed in claim 6 wherein: a. the viscosifier is selected from the group comprising of bentonite, xanthan gum, clay and polymers;
b. the weighing agent is selected from the group comprising of barite, hematite and calcium carbonate; and
c. the fluid loss reducer is selected from the group comprising of starch, carboxy methylated starch, polyanionic cellulose, polymeric fluid loss additive
10. A rotary method for drilling a well through calcium-containing formations in which the water based drilling fluid as claimed in claim 6 is circulated down the well and back to the surface, and contacted with the drill bits, said drilling fluid having calcium soaps dispersed therein.