EA042226B1 - DRILLING COMPOSITION FOR WELLBORE - Google Patents

Description

Cross-reference to related applications

This application claims the priority and benefit of U.S. Provisional Application No. 62/778363, filed Dec. 12, 2018, which is incorporated herein by reference in its entirety.

Technical field

This invention relates to drilling compositions, such as compositions used for drilling wells containing natural resources.

State of the art

Wells may be drilled to extract natural resources such as oil, gas or water. The wellbore is surrounded by a formation, such as shale or clay, which can affect the stability of the wellbore. For example, the formation may exert pressure on the wellbore, or fluids from the formation may enter the wellbore. The formation may contain permeable regions, and fluids injected into the wellbore may enter the permeable regions, resulting in filtration of the drilling fluid. Such filtration of the drilling fluid can affect the efficiency of drilling, may result in the displacement of drilling fluids and affect the stability of the formation.

Drilling compositions, such as drilling fluids or drilling fluids, can be used to facilitate the drilling of wellbores. The drilling fluid or mud may be distributed and circulated through the wellbore to provide functions such as cooling and lubricating the drilling equipment, or to remove cuttings and clean the wellbore. In addition to performing these functions, drilling compositions can also help improve formation stability.

The essence of the invention

This Summary is provided to introduce various concepts in a simplified form, which are further described below in the Detailed Description. It is intended that this Summary section is not intended to identify required or key features of the claimed subject matter, but this section does not limit the scope of the claimed subject matter.

In aspects, this invention describes drilling fluid compositions. The drilling fluid compositions can be used in wellbore drilling processes, for example, to form oil wells. In one aspect, sodium asphalt sulfonate (SAS; sodium asphalt sulfonate), a salt of asphalt, can be used to control drilling fluid filtration and lubricity of drilling fluid compositions. In addition, SAS can seal micro-fractures in shale, which can ensure formation stability. Powdered rubber latex has been found to have synergistic effects in combination with SAS, eg more than additive effects, and this combination helps control mud filtration, lubricity and formation stability. For example, the addition of both powdered rubber latex and SAS in a drilling fluid composition provides relatively higher lubricity, less mud filtration, better sealing of microfractures in the shale, and formation stability than using similar concentrations of SAS alone or powdered latex. In some aspects, synergistic effects are enhanced by using a concentration of SAS that is greater than or equal to the concentration of latex.

In one aspect, this invention describes a drilling fluid composition having a first concentration of latex powder and a second concentration of SAS. The second concentration of SAS (by weight, eg lbs/bbl) may be greater than or equal to the first concentration of latex (by weight, eg lbs/bbl). In some examples, the second concentration of SAS (by weight) may be greater than the first concentration of latex (by weight).

Both the summary of the invention and the following detailed description provide examples that are provided solely as an explanation of the present invention. Accordingly, the foregoing summary of the invention and the following detailed description should not be considered limiting. In addition to the features and variations provided herein, additional features or variations may be suggested, such as, for example, various feature combinations and subcombinations thereof set forth in the Detailed Description.

Brief description of graphic materials

In FIG. 1 is a graph illustrating the reduced filtration of high temperature high pressure (HPHT) mud at 121°C (250°F) for an aqueous mud composition containing both sodium asphalt sulfonate (SAS) and powdered latex, compared to compositions that do not contain one or both of the SAS or latex.

In FIG. 2 is a graph illustrating reduced mud filtration in a permeability plugging test (PPT) at 121°C (250°F) for water-based mud compositions containing both SAS and latex powder, and having a higher mass concentration of SAS than powdered latex, compared to compositions that do not contain one or both of SAS or latex.

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In FIG. 3 is a graph illustrating the reduced filtration of drilling fluid at

PPT at 163°C (325°F) for water-based drilling fluid compositions containing both SAS and powdered latex, and having a higher mass concentration of SAS than powdered latex, compared to compositions that do not contain one or both in SAS or latex.

In FIG. 4 is a graph illustrating mud filtration at PPT at 163°C (325°F) for water-based mud compositions containing both SAS and powdered latex and having a higher mass concentration of SAS than powdered latex, according to compared to compositions that do not contain one or both of SAS or latex.

In FIG. 5 is a graph illustrating the reduced PPT mud filtration over time for water-based mud compositions containing both SAS and latex powder and having a higher mass concentration of SAS than latex powder compared to compositions that do not contain SAS or latex at various temperatures (121, 135 and 149°C (250, 275 and 300°F)).

In FIG. 6 is a graph illustrating the reduced mud filtration at PPT at 135°C (275°F) for water-based mud compositions containing both SAS and various types of powdered latex and having a higher mass concentration of SAS than powdered latex, compared to compositions that do not contain SAS.

In FIG. 7 is a graph illustrating the reduced mud filtration at PPT at 135°C (275°F) for oil-based mud compositions containing both SAS and latex powder and containing SAS at a mass concentration greater than or equal to that of the powdered latex. latex, compared to compositions that do not contain one or both of the SAS or latex.

In FIG. 8 is a graph illustrating reduced drilling fluid filtration at PPT at 149°C (300°F) for oil-based drilling fluid compositions containing both SAS and powdered latex, and containing SAS in a mass concentration that is equal to the concentration of powdered latex, compared to compositions that do not contain one or both of SAS or latex.

In FIG. 9 is a graph illustrating the reduced drilling fluid filtration at PPT at 149°C (300°F) for oil-based drilling fluid compositions containing both SAS and latex, and containing SAS in a mass concentration that is equal to the concentration of powdered latex, according to compared to compositions that do not contain one or both of SAS or latex.

In FIG. 10 is a graph illustrating reduced mud filtration at PPT and rapid leachate loss at 135°C (275°F) for water-based mud compositions containing both SAS and latex powder and containing SAS at a mass concentration greater than than powdered latex, compared with compositions containing other additives.

In FIG. 11 is a graph illustrating reduced mud filtration at PPT and rapid leachate loss at 149°C (300°F) for oil-based mud compositions containing both SAS and latex powder and containing SAS at a mass concentration greater than than powdered latex, compared with compositions containing other additives.

In FIG. 12 is a graph illustrating API and HPHT filtrate volumes at 191°C (375°F) for water-based drilling fluid compositions containing both SAS and latex powder and containing SAS at a mass concentration greater than latex powder, compared to compositions that do not contain one or both of SAS or latex.

In FIG. 13 is a graph illustrating the change in coefficient of friction with torque for oil-based drilling fluid compositions containing a solid lubricant.

In FIG. 14 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions with and without solid lubricant.

In FIG. 15 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions excluding and containing solid lubricant and particle friction reducing material.

In FIG. 16 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions excluding and containing solid lubricant and organophilic clay.

In FIG. 17 is a graph illustrating the coefficient of friction versus time for a base oil based drilling fluid composition.

In FIG. 18 is a graph illustrating the coefficient of friction versus time for a base oil drilling fluid composition containing a solid lubricant.

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In FIG. 19 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions without lubricant, containing a solid lubricant, and containing two different liquid lubricants.

In FIG. 20 is a graph illustrating the change in weight up and weight down a horizontal section as a function of depth.

Detailed description of the invention

It should be understood that the present invention is not limited in its application to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings.

Definitions.

For a clearer understanding of the terms used in this document, the following definitions are given. Unless otherwise indicated, the following definitions apply to the present description. If any term is used in the description which is not specifically defined herein, the definition given in the IUPAC Compendium of Chemical Terminology, 2nd ed (1997) may be used, provided that such definition does not conflict with any other description or definition, used herein, or does not render undefined or invalidate any claim to which this definition refers. In the event that any definition or use given in any document incorporated herein by reference conflicts with a definition or use given herein, the definition or use given herein shall take precedence.

Although the compositions and methods are described as including various components or steps, these compositions and methods can also essentially consist of or consist of various components and steps, unless otherwise indicated.

The singular is meant to include plural alternatives, such as at least one. As used herein, the terms including, together with, and having are defined as containing (i.e., as open statements) unless otherwise indicated.

Various numerical ranges are disclosed herein. If Applicant discloses or claims a range of any type, then Applicant does so in order to disclose or claim separately each possible numerical value that can reasonably be included in the specified range, including the end values of the range, as well as any subranges and combinations of subranges included in the specified range, unless otherwise indicated. For example, when disclosing a population average particle size of about 70 microns to about 100 microns, Applicant does so to list individually 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, ..., 98, 99, 100, including any single integer from 70 to 100 inclusive, subranges, and combinations of subranges included therein, and these ways of describing such ranges are interchangeable. In addition, all numerical end values of the ranges disclosed herein are approximate, unless special condition states otherwise. As a typical example, if Applicant discloses in an aspect of this invention that one or more drilling fluid compositions have a plastic viscosity in the range of 20 to 30 centipoise, this range should be understood to include viscosities in the range of about 20 centipoise to about 30 centipoise.

Values or ranges may be expressed herein as about, from about one particular value, and/or to about another particular value. If the specified values or ranges are expressed in this way, then other disclosed implementation options include a specific specified value, from one specific value and/or to another specific value. Similarly, it should be understood that if values are expressed as an approximation using the preceding definition of about, then the particular value constitutes another implementation. In addition, it should be understood that a number of meanings are disclosed herein and that each meaning is also disclosed herein as being about that specified particular value in addition to the specified value itself. In another aspect, the use of the term about means ±20% of the declared value, ±15% of the declared value, ±10% of the declared value, ±5% of the declared value, ±3% of the declared value, or ±1% of the declared value.

Applicant reserves the right to remove or exclude any individual members of any such group of values or ranges, including any subranges or combinations of subranges within said group that may be claimed under the range or in any similar manner, if for any reason the applicant chooses to claim the present invention in its entirety, for example, in order to take into account materials that the applicant may not have been aware of at the time of filing the application. In addition, the applicant reserves the right to delete or exclude any individual substituents, analogs, compounds, ligands, structures or groups thereof, or any elements of the claimed group, if for any reason the applicant decides to claim the present invention is not in full , for example, in order to take into account materials that the applicant may not have known about at the time of application.

The term latex refers to an emulsion of one or more polymers in a solvent such as water.

The term latex powder refers to a powder obtained by drying or dehydrating latex.

The term asphaltsulfonate refers to sulfonated asphalt obtained by treating asphalt with a sulphurizing agent.

The term sodium asphaltsulfonate (SAS) refers to the sodium salt of asphaltsulfonate.

The term substituted in the context of describing a group, for example, in relation to a substituted analogue of a particular group, is intended to describe a compound or group in which any non-hydrogen moiety formally replaces a hydrogen in that group or compound, and is not intended to be limiting. A compound or group may also be referred to herein as unsubstituted, or as equivalent terms, such as unsubstituted, that refer to the parent group or compound. The term substituted is non-limiting and includes inorganic substituents or organic substituents, as indicated and as understood by a person skilled in the art.

While any methods and materials similar or equivalent to those described herein may be used to practice or test the present invention, exemplary methods and materials are described herein.

The abstract of this application is not intended to be used in interpreting the scope of the claims or to limit the scope of the subject matter disclosed herein, but rather to satisfy the requirements of 37 C.F.R. § 1.72(b) to enable the U.S. Patent and Trademark Office and the public at large to quickly determine, at a glance, the nature and substance of a technical disclosure. In addition, any headings that may be used herein are also not intended to be used to interpret the scope of the claims or to limit the scope of the subject matter disclosed herein. Any use of the past tense to describe any example indicated as constructive or as an example of possible use is not intended to indicate that the constructive example or example of possible use has actually been implemented.

All publications and patents mentioned herein are incorporated herein by reference for the purposes of describing and disclosing, for example, the structures and methodologies described in such publications that can be applied in connection with the invention described herein. The contents of the publications discussed in this document are given only as of the date of filing of this application. Nothing in this document should be construed as an admission that the inventors are not entitled to date the invention of an earlier publication by reference to an earlier invention.

The present invention generally relates to drilling compositions, such as compositions used for drilling wells containing natural resources. The drilling compositions contain a powdered latex and at least one asphalt sulfonate salt, such as sodium asphalt sulfonate (SAS).

Latex is an emulsion of one or more polymers in water or an aqueous medium and may be natural or synthetic. In some examples, the latex includes an emulsion of a synthetic copolymer. For example, the latex may include an emulsion of a styrene-butadiene copolymer in an aqueous medium. Natural or synthetic latex may contain dispersed polymer particles. The properties of the latex may depend, inter alia, on the degree of crosslinking in the polymer.

Powdered latex can be formed from the latex, for example, by drying, dehydrating or dehydrating the latex to isolate or remove water from the emulsion to leave dispersed particles or agglomerates of one or more polymers. Thus, the latex powder may comprise a powder of polymer particles separated from the aqueous medium of the latex, for example by drying. Drying may include spray drying.

The properties of the latex powder can be controlled by adjusting the properties of the latex from which the latex powder is made. For example, the degree of crosslinking, concentration, solvent density, drying rate, or other parameters may ultimately determine the properties of the latex powder. The latex powder is dispersible or soluble in water-based and oil-based carriers and is suitable for use in drilling fluid compositions, eg, water-based drilling fluid compositions and oil-based drilling fluid compositions.

The latex powder may contain at least one of a styrene-butadiene copolymer or a vinyl acetate-ethylene copolymer. In some aspects, the latex powder consists or essentially consists of a copolymer of styrene and butadiene. In some aspects, the latex powder consists or essentially consists of a copolymer of vinyl acetate and ethylene. The latex powder may have any suitable population average particle size and particle size distribution. For example, the latex powder may have an aggregate mean particle size in the range of about 0.150 microns to about 150 microns. In some aspects, the latex powder has a population average particle size in the range of about 70 microns to about 100 microns, or in the range of about 80 microns to about 90 microns. In some aspects, the population average particle size may be about 85 microns. The population mean particle size may be the size

D50 measured by laser diffraction.

The D10, D50, and D90 values represent the 10th, 50th, and 90th percentiles of the particle size distribution (PSD), respectively, when measured by volume. That is, for example, the D10 value on the particle size distribution curve is such that 10% of the particles are smaller and 90% larger than the particle size at the applicable measurement point. Similarly, the D50 and D90 values are those values on the particle size distribution curve at which, respectively, 50% or 90% of the particles are smaller than the particle size at the corresponding measurement point. For example, for a particular sample, if D50=90 µm, there are 50% of particles that are larger than 90 µm and 50% of particles that are smaller than 90 µm. Methods that can be used to determine the particle size distribution (PSD) of powdered latex materials for use in accordance with the present invention include any of the standard methods for determining particle size distributions of particulate materials in a specific size range (for example, from 0.1 to 200 µm), including, without limitation, gravity fluid settling methods as described in ISO 13317 and sieving/settling methods such as those described in ISO 1 1277, as well as spectral, acoustic, and laser diffraction methods, as appropriate, and combinations thereof.

Asphalt refers to hydrocarbon materials containing bitumen components, for example one or more of naphthenes, polar aromatics, saturated hydrocarbons, or asphaltenes. Asphalt may be obtained from natural sources or may be obtained by refining petroleum through one or more distillation, precipitation, cracking, oxidation or other operations. The asphalt may include one or more of asphaltenes, maltenes, oxidized asphalt, residual oils without additives, distillation residues, bottoms, cracking residues, asphalt bitumens, or combinations thereof.

Various high molecular weight asphalt compounds are usually divided into 4 fractions: saturated hydrocarbons, aromatic hydrocarbons, resins and asphaltenes. The asphaltene fraction is determined gravimetrically and is defined as the hexane-insoluble asphalt fraction. The other fractions were separated by column chromatography using a capillary silica column and increasing the polarity of the solvent to elute the appropriate fractions. The asphaltene fraction is soluble in highly polar solvents such as toluene. Asphalts vary considerably in composition and physical properties depending on the source of the crude oil and the refining process. Asphalt can be oxidized to increase the softening point. It is insoluble in water.

Natural asphalts such as Gilsonite® (American Gilsonite Company, Houston, Texas), collectively known as uintaite, petroleum bitumen, or asphaltite, are similar to petroleum asphalt and have similar properties. Gilsonite® is often used in drilling fluids due to its high softening point.

Polymer-modified asphalts are petroleum-based asphalts that have been blended with synthetic polymers such as SBS, EVA, or rubber to improve their performance in certain applications, especially road surfaces.

Asphaltsulfonate (also known as sulfonated asphalt) can be formed by sulfonating asphalt with a sulphurizing agent. The sulfonating agents may include one or more of fuming sulfuric acid, chlorosulfonic acid, concentrated sulfuric acid, or sulfur trioxide. The asphalt sulfonate can be obtained by forming a mixture of asphalt and solvent and exposing the mixture to a sulphurizing agent. The solvent may include hexane. After sulfonation, the resulting product can be neutralized to form a salt and subsequently separated from the solvent. Neutralization can be carried out using a basic compound such as sodium hydroxide or potassium hydroxide. When neutralized with sodium hydroxide, sodium asphaltsulfonate is formed, and when neutralized with potassium hydroxide, potassium asphaltsulfonate is formed. The asphalt sulfonate may have different properties and contain a mixture or combination of materials depending on the parameters of the sulfonation process, such as the degree of sulfonation or the type of sulfonating agent used.

The term sodium asphaltsulfonate (SAS) refers to the sodium salt of asphaltsulfonate. While this invention relates to SAS, in the examples SAS may be replaced or combined with one or more different asphalt sulfonate salts, such as potassium salt, calcium salt, lithium salt, or other suitable asphalt sulfonate salt. Unlike asphalt, which is neither anionic nor water soluble, sodium asphaltsulfonate can be anionic and water soluble, such as at least 70% or at least 80% water soluble. For example, sodium asphaltsulfonate can be prepared by reacting asphalt (diluted with heptane) with sulfur trioxide to form sulfonic acid. Acid can be neutralized with alkali (50%

NaOH) to form the sodium salt. This product is water soluble and no longer has the softening point or other characteristics of asphalt.

Soltex® (Drilling Specialties Company, Woodlands, Texas) is an example of sodium asphaltsulfonate. It does not exhibit the typical properties of asphalt, does not melt and does not have a softening point, unlike asphalt and other natural bituminous products, which soften and melt.

Drilling compositions containing both powdered latex and SAS may exhibit one or more of more mud filtration compared to compositions that do not contain one or both of powdered latex or SAS. Mud filtration can be determined using High Temperature High Pressure Mud Filtration Tests (HPHT), Plugging Permeability Tests (PPT), or Rapid Loss Loss Fluid Loss according to protocols established by the American Petroleum Institute (API; American Petroleum Institute). Drilling compositions containing both latex powder and SAS can provide better lubrication, such as a lower coefficient of friction, than compositions that do not contain either or both of the latex or SAS. The drilling compositions of the present invention may also contribute to formation stability and cuttings removal. The synergistic effects resulting from the combination of latex powder and SAS are applicable to drilling fluid compositions, including petroleum-based carriers or water-based carriers. Without being limited by theory, it can be said that the chemical bonding or networking may result from the combination of powdered latex and SAS, which may lead to a synergistic effect.

In aspects, compositions containing both powdered latex and SAS and having a higher mass concentration of SAS than powdered latex may exhibit lower mud filtration, higher lubricity, and higher formation stability compared to compositions containing other relative concentrations. SAS and powdered latex.

In one aspect, the drilling fluid composition has a first concentration of powdered latex and a second concentration of SAS. In some aspects, the second SAS concentration may be greater than or equal to the first latex concentration. In some such aspects, the second concentration of SAS may be greater than the first concentration of latex. For example, the second concentration of SAS may be greater than the first concentration of latex by a predetermined threshold, such as at least 0.1 lb per barrel (lb/bbl), at least 0.25 lb/bbl, at least 0.5 lb/bbl, at least 1.0 lb/bbl, at least 1.5 lb/bbl, at least 2 lb/bbl, at least 2.5 lb/bbl, at least 3 lb/bbl, at least 3.5 lb/bbl, at least 4 lb/bbl, or at least 5 lb/bbl. In other examples, the second SAS concentration may be substantially the same as the first latex concentration. Also in other examples, the second concentration of SAS may be lower than the first concentration of latex.

In one aspect, the drilling fluid composition has a first concentration of powdered latex and a second concentration of SAS, wherein the second concentration of SAS is greater than or equal to the first concentration of latex.

The latex powder and SAS may be dispersed or solubilized in a carrier, such as an aqueous or petroleum based carrier, to form a drilling fluid composition. In some examples, the additive composition added to the drilling fluid composition or to the carrier composition may contain powdered latex and SAS in accordance with the present invention. The additive composition may also contain one or more additives, for example one or more of asphalt, Gilsonite® (or uintaite), lignite, or any other suitable drilling composition additive.

In some aspects, the drilling fluid composition contains an aqueous carrier and has a second concentration of SAS that is greater than or equal to the first concentration of latex powder. In some such aspects, the second concentration of SAS in the drilling fluid composition may be greater than the first concentration of the latex. Drilling fluid compositions containing an aqueous carrier in accordance with such aspects may exhibit lower drilling fluid filtration than compositions that do not contain either or both of powdered latex or SAS. For example, in some such aspects, the drilling fluid composition has an average high temperature high pressure (HPHT) drilling fluid filtration at 121 °C (250 °F) and 500 psi (psi) of less than or about 20 ml when tested according to the American Petroleum Institute (API) test 13B-1. In some such aspects, the drilling fluid composition may have an average drilling fluid filtration at HPHT at 121°C (250°F) and 500 psi. inch less than or about 18 ml, or less than or about 15 ml, or less than or about 12 ml.

In some such aspects, the drilling fluid composition has an average filtration in the Well Plugging Permeability Test (PPT) at 121°C (250°F) with a 12 micrometer filter disc of less than or about 18.0 ml when tested according to with API 13B-1 test.

In some such aspects, the drilling fluid composition has an average filtration at a PPT of less than or about 16 ml, or less than or about 15 ml, or less than or about 12 ml.

Drilling fluid compositions containing an aqueous carrier according to such aspects may exhibit higher lubricity than compositions that do not contain either or both of powdered latex or SAS. For example, in some such aspects, the drilling fluid composition has a coefficient of friction of less than or about 0.40 at 250 lb-ft of torque. In some such aspects, the drilling fluid composition may have a coefficient of friction less than or about 0.35, or less than or about 0.30, or less than or about 0.25.

Drilling fluid compositions containing an aqueous carrier in accordance with the present invention may exhibit rheological properties (eg, one or more of plastic viscosity, yield strength, or static shear stress) suitable for drilling. For example, a drilling fluid composition according to some such aspects has a plastic viscosity at 49° C. (120° F.) in the range of about 10 centipoise to about 30 centipoise when tested in accordance with the American Petroleum Institute (API) test 13B-1. In some such aspects, the drilling fluid composition has a plastic viscosity in the range of about 10 centipoise to about 15 centipoise, or about 10 centipoise to about 20 centipoise, or 15 centipoise to about 20 centipoise, or about 15 centipoise to about 30 centipoise, or from about 20 cP to about 30 cP.

In some such aspects, the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 10 lb/100 sq. ft to about 45 lbs/100 sq. feet when tested in accordance with the American Petroleum Institute (API) test 13B-1. In some such aspects, the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 10 lb/100 sq. feet to about 20 pounds/100 sq. feet, or from about 20 lbs/100 sq. ft to about 45 lbs/100 sq. feet, or from about 10 lbs/100 sq. feet to about 30 pounds/100 sq. feet, or from about 15 lbs/100 sq. feet to about 20 pounds/100 sq. feet, or from about 15 lbs/100 sq. feet to about 30 pounds/100 sq. feet, or from about 30 lbs/100 sq. ft to about 45 lbs/100 sq. ft.

In some such aspects, the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) in the range of about 2.0 lb/100 sq. ft to about 6.5 lb/100 sq. feet when tested in accordance with the American Petroleum Institute (API) test 13B-1. In some such aspects, the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) ranging from about 2.5 lb/100 sq. ft to about 6.5 lb/100 sq. ft., or from about 2.0 lbs/100 sq. ft to about 3.0 lb/100 sq. ft., or from about 5.0 lbs/100 sq. ft to about 6.5 lb/100 sq. feet, or from about 5.5 lbs/100 sq. ft to about 6.5 lb/100 sq. ft.

In some such aspects, the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 12 lbs/100 sq. feet when tested in accordance with the American Petroleum Institute (API) test 13B-1. In some such aspects, the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 5 lbs/100 sq. feet, or from about 2 pounds/100 sq. feet to about 10 pounds/100 sq. feet, or about 3 pounds/100 sq. feet to about 10 pounds/100 sq. feet, or about 5 pounds/100 sq. feet to about 10 pounds/100 sq. feet, or about 5 pounds/100 sq. ft to about 12 lbs/100 sq. ft.

Drilling fluid compositions containing an aqueous carrier may have any suitable first concentration of latex powder and second concentration of SAS. In some such aspects, the second concentration of SAS may be greater than or equal to the first concentration of latex powder. In some such aspects, the first concentration of powdered latex is at least 1 lbw per barrel (lbw/bbl) and the second SAS concentration is at least 2 lbw/bbl. In some such aspects, the first concentration of latex powder may range from about 1.5 lbs/bbl to about 2.5 lbs/bbl and the second SAS concentration may range from about 2.5 lbs/bbl to about 3.5 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 2 lbs/bbl and the second concentration of SAS may be about 3 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 1.5 lbs/bbl, while the second concentration of SAS may be about 4.5 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 1.2 lbs/bbl, while the second concentration of SAS may be about 4.8 lbs/bbl. In some such aspects, the first concentration of latex powder may be about 1.8 lbs/bbl, while the second concentration of SAS may be about 4.2 lbs/bbl.

The drilling fluid compositions containing aqueous carriers of the present invention may be prepared using any suitable method. In aspects, the method includes dispersing a first predetermined amount of latex powder and a second predetermined amount of SAS in an aqueous vehicle to form an aqueous drilling fluid.

The water-based drilling fluid may contain any drilling composition in accordance with the present invention containing a water-based carrier.

In some aspects, the drilling fluid composition contains an oil-based carrier and has a second concentration of SAS that is greater than or equal to the first concentration of latex powder. In some such aspects, the second concentration of SAS in the drilling fluid composition may be greater than the first concentration of the latex. Drilling fluid compositions containing an oil-based carrier, in accordance with such aspects, may exhibit less drilling fluid filtration than compositions that do not contain one or both of powdered latex or SAS. For example, in some such aspects, a drilling fluid composition containing an oil-based carrier has an average drilling fluid filtration in a plugging permeability test (PPT) at 121°C (300°F) with a 55 micrometer filter disc of less than or about 1 .06 ml when tested in accordance with the American Petroleum Institute (API) test 13B-2. In some such aspects, a drilling fluid composition comprising an oil-based carrier has an average drilling fluid filtration at PPT at 135°C (275°F) of less than or about 3.3 ml or less or about 3.0 ml or less or about 2.5 ml. In some such aspects, a drilling fluid composition comprising an oil-based carrier has an average drilling fluid filtration at PPT at 149°C (300°F) with a 40 micrometer filter disc of less than or about 3.3 ml, or less than or about 3. 15 ml or less or about 3.00 ml.

Drilling fluid compositions containing an oil-based carrier in accordance with such aspects may exhibit higher lubricity than compositions that do not contain one or both of powdered latex or SAS.

Drilling fluid compositions containing an oil-based carrier according to the present invention may exhibit rheological properties suitable for drilling. For example, a drilling fluid composition according to some such aspects has a plastic viscosity at 49°C (120°F) in the range of about 10 centipoise to about 30 centipoise when tested in accordance with API test 13B-2. In some such examples, the drilling fluid composition may have a plastic viscosity in the range of about 10 centipoise to about 15 centipoise, or in the range of about 12 centipoise to about 20 centipoise, or in the range of about 15 centipoise to about 20 centipoise, or in the range of about 15 centipoise to about 25 centipoise, or in the range of about 15 centipoise to about 30 centipoise.

In some such aspects, the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 5 lb/100 sq. ft to about 12 lbs/100 sq. feet when tested in accordance with API test 13B-2. In some such aspects, the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 5 lb/100 sq. feet to about 10 pounds/100 sq. ft., or from about 5 lbs/100 sq. ft to about 8 lbs/100 sq. ft., or from about 8 lbs/100 sq. ft to about 12 lbs/100 sq. ft., or from about 5 lbs/100 sq. ft to about 6 lbs/100 sq. ft.

In some such aspects, the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 12 lbs/100 sq. feet when tested in accordance with API test 13B-2. In some such aspects, the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 11 lbs/100 sq. ft., or in the range of about 2 lbs/100 sq. feet to about 10 pounds/100 sq. ft., or in the range of about 5 lbs/100 sq. ft to about 12 lbs/100 sq. ft., or in the range of about 2 lbs/100 sq. ft to about 5 lbs/100 sq. ft.

In some such aspects, the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 40 lbs/100 sq. feet when tested in accordance with API test 13B-2. In some such aspects, the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. feet to about 10 pounds/100 sq. feet, or from about 2 pounds/100 sq. feet to about 20 pounds/100 sq. feet, or about 10 pounds/100 sq. feet to about 30 pounds/100 sq. feet, or from about 10 lbs/100 sq. feet to about 20 pounds/100 sq. feet, or about 20 pounds/100 sq. feet to about 30 pounds/100 sq. feet, or from about 10 lbs/100 sq. ft to about 40 lbs/100 sq. ft.

Drilling fluid compositions containing an oil-based carrier may have any suitable first concentration of latex powder and second concentration of SAS. In some such aspects, the second concentration of SAS may be greater than or equal to the first concentration of latex powder. For example, in some such aspects, the first concentration of powdered latex may be at least about 1 lb mass per barrel (lb mass/bbl), and the second concentration of SAS may be at least about 1 lb mass/bbl. In some such aspects, the first concentration of latex powder may be at least about 2 lbs/bbl and the second concentration of SAS may be at least about 2 lbs/bbl. In some such aspects, the first concentration of powdered latex may be at least about 1 lb mass/bbl and the second SAS concentration may be at least about 2 lb mass/bbl. In some such aspects, the first concentration of latex powder may be at least about 1 lb mass/bbl and the second SAS concentration may be at least about 3 lb mass/bbl. In some such aspects, the first concentration of powdered latex may be at least about 1 lb mass/bbl and the second SAS concentration may be at least about 4 lb mass/bbl. In some such aspects, the first concentration of powdered latex may be at least about 1.5 lbs/bbl and the second concentration of SAS may be at least about 2.5 lbs/bbl. In some such aspects, the first concentration of latex powder may be at least about 1.2 lbs/bbl and the second concentration of SAS may be at least about 4.8 lbs/bbl. In some such aspects, the first concentration of latex powder may be at least about 1.5 lbs/bbl and the second concentration of SAS may be at least about 4.5 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 1 lb mass/bbl and the second concentration of SAS may be about 3 lb mass/bbl. In some such aspects, the first concentration of powdered latex may be about 1.2 lbs/bbl and the second concentration of SAS may be about 4.8 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 1.5 lbs/bbl and the second concentration of SAS may be about 4.5 lbs/bbl. In some such aspects, the first concentration of latex powder may be about 1.8 lbs/bbl and the second concentration of SAS may be about 4.2 lbs/bbl. In some such aspects, the first concentration of powdered latex may be about 2 lbs/bbl and the second concentration of SAS may be about 3 lbs/bbl. In some such aspects, the first concentration of latex powder may be in the range of about 1.5 lbs/bbl to about 2.5 lbs/bbl and the second SAS concentration may be in the range of about 1.5 lbs/bbl to about 2.5 lbs/bbl. In some such aspects, the first concentration of latex powder may be about 2 lbs/bbl and the second concentration of SAS may be about 2 lbs/bbl.

Drilling fluid compositions containing petroleum-based carriers of the present invention may be prepared using any suitable method. In aspects, the method includes dispersing a first predetermined amount of latex powder and a second predetermined amount of SAS in an oil-based carrier to form an oil-based drilling fluid. An oil-based drilling fluid may include any drilling composition in accordance with the present invention containing an oil-based carrier.

The drilling fluid compositions of the present invention may include a ready-to-use drilling fluid composition or may refer to an additive drilling fluid composition that must be added to a carrier or drilling fluid prior to use. For example, drilling fluid additive compositions may include a mixture of powdered latex and SAS. For example, such drilling fluid additive compositions may include mixtures of powdered latex and SAS such that adding a given amount of drilling fluid additive compositions to a carrier results in a drilling fluid composition having concentrations of powdered latex and SAS in accordance with the present invention.

Blends of powdered latex and SAS (and including additional optional components in accordance with the present invention) can be described as a solid lubricant, a solid lubricant, or a solid lubricant, since such mixtures can be substantially solid compared to conventional liquid lubricants. Thus, in embodiments, the drilling fluid additive compositions may include a solid lubricant composition. For example, the drilling fluid additive composition or solid lubricant composition may contain SAS and powdered latex. In some embodiments, the additive drilling fluid composition or solid lubricant composition consists essentially of SAS and latex powder. In some embodiments, the additive drilling fluid composition or solid lubricant composition consists of SAS and latex powder.

The drilling fluid additive compositions may contain SAS and powdered latex in the form of a 50/50 SAS-latex blend, a 60/40 SAS-latex blend, a 70/30 SAS-latex blend, an 80/20 SAS-latex blend, or a 90/SAS-latex blend. 10. The ratio refers to the relative concentrations of SAS and latex, and mixtures may optionally contain other components or additives.

Drilling compositions in accordance with the present invention may provide one or more

- 9 042226 from better control of mud filtration, plug permeability testing, formation stability and lubricity, and can also reduce logistical and material handling work at the well site.

Examples

The present invention is further illustrated by the following examples, which should in no way be construed as limiting the scope of the present invention. Upon reading the description provided herein, one skilled in the art will be able to propose various other aspects, embodiments, modifications, and equivalents without departing from the spirit of the present invention or the scope of the appended claims.

General provisions.

Mud filtration was determined using the High Temperature High Pressure Drilling Fluid Filtration Test (HPHT) and Plug Permeability Test (PPT) protocols in accordance with the American Petroleum Institute (API) test kit 13B-1 for compositions containing a carrier. water-based, and a set of test modes 13B-2 for compositions containing an oil-based carrier. Unless otherwise noted, latex blend or SAS latex refers to a blend of SAS and XP-211 styrene-butadiene copolymer latex, also known as Axilat™ PSB 150 (Synthomer, Roebuck, South Carolina).

Example 1

The properties of water-based drilling fluid compositions having various concentrations of powdered latex and sodium asphalt sulfonate (SAS) were evaluated. The base drilling fluid composition contained 7.0 lbs/bbl (lb/bbl) bentonite, 2 lbs/bbl polyanionic cellulose, 0.75 lbs/bbl biopolymer, 10 lbs/bbl Rev Dust™ inert material ( Milwhite, Inc., Brownsville, Texas), 0.5 lbs/bbl of caustic soda and 2 lbs/bbl of sodium sulfite. The base composition had a density of 8.6 lbs/gal.

Four samples were prepared: A1) base, B1) base with 6 lbs/bbl SAS, C1) base with 4 lbs/bbl latex powder and D1) base with 3 lbs/bbl SAS and 2 lbs/bbl latex powder (SAS-latex mix 1.5:1 or 60/40). The samples were hot rolled for 16 hours at 121°C (250°F). The rheological properties of the samples, such as plastic viscosity, yield strength and static shear stress, were determined using a rotational viscometer and are presented in table. 1.

Table 1 Rheology (49°C (120°F)) A1 (base) IN 1 (SAS) C1 (latex) D1 (SAS latex 60/40) Viscosity at 600 rpm (cP) 41.50 37.50 44.00 38.10 Viscosity at 300 rpm (cP) 26.50 24.10 28.10 24.60 Viscosity at 200 rpm (cP) 20.00 18.70 21.80 18.90 Viscosity at 100 rpm (cP) 12.90 12.10 14 12.50 Viscosity at 6 rpm (cP) 1.90 1.90 2.40 2.20 Viscosity at 3 rpm (cP) 1.40 1.30 1.90 1.70 Plastic viscosity (cP) 15.00 13.40 15.90 13.50 Yield Strength (lb/100 sq. ft) 11.50 10.70 12.20 11.10 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 2.1/2.7 2.0/3.5 2.4/3.0 2.3/2.5 API filtrate (ml) 8.10 8.22 7.43 6.93 pH 8.27 7.81 8.51 7.94

HPHT mud filtration and formation filtrate fast loss for four samples were determined using the API test kit 13B-1. The results are presented in table. 2.

- 10 042226

table 2

Mud Filtration at HTHP (mL) at 121 °C (250 °F) A1 (base) IN 1 (SAS) C1 (latex) D1 (SAS latex 60/40) minutes 1 3.18 2.28 2.35 17.10 5 7.36 4.93 5.23 3.95 7.5 10.74 6.10 6.47 4.79 10 12.64 7.15 7.54 5.48 15 14.74 8.91 9.36 6.87 20 16.65 10.42 10.87 7.88 25 18.27 11.80 12.24 8.65 thirty 19.56 13.08 13.51 9.42 Drilling Fluid Filtration at HTHP (mL) 39.12 26.16 27.02 18.84 Rapid loss of formation filtrate 0.0 oh oh oh oh 0.1

The results of the HPHT test are shown in FIG. 1. In FIG. 1 is a graph illustrating the reduced filtration of high temperature high pressure (HPHT) mud at 121°C (250°F) for a water-based mud composition containing both sodium asphalt sulfonate (SAS) and latex powder compared with compositions that do not contain one or both of SAS or latex. Sample D1 showed a 28% reduction in HPHT mud filtration compared to Sample B1 and 30% compared to Sample C1.

The coefficient of friction (CoF; coefficient of friction) was determined for Al-DI samples. CoF can be determined using any of several methods, including a lubricity tester (OFI Testing Equipment, Houston, TX), a lubricity tester (OFI Testing Equipment, Houston, TX), or a tribometer ( Nanovea, Irvine, California). The recalculated results (IOOxCoF) are presented in Table. 3.

Table 3

Torque (in-lb) A1 (base) Bl(SAS) Cl (latex) DI (SAS latex 60/40) 100 x CoF 100 4.1 2.5 20.2 17.1 150 3.1 9.5 29.3 25.1 200 3.4 7.2 37.3 31.5 250 8.0 5.0 43.1 38.6 300 350 5.9 43.4 47.1 45.4 400 66.0

Sample D1 (SAS-latex 60/40) showed a CoF that was typically lower than Samples Bl (SAS) and C1 (latex), for example, at 250 in-lbs of torque.

Example 2

The properties of water-based drilling fluid compositions having various concentrations of powdered latex and sodium asphalt sulfonate (SAS) were evaluated. The base mud composition contained 7.0 lbs/bbl bentonite, 2 lbs/bbl polyanionic cellulose, 0.75 lbs/bbl biopolymer, 10 lbs/bbl Rev Dust™ inert material (Milwhite, Inc., Brownsville , Texas), 0.5 lbs/bbl caustic soda, 2 lbs/bbl sodium sulfite, and 20 lbs/bbl barite. The base composition had a density of 9.0 lb/gal.

- 11 042226

Six samples were prepared: A2) base, B2) base with 6 lbs/bbl SAS, C2) base with 6 lbs/bbl latex powder, D2) base with 1.5 lbs/bbl SAS and 4.5 lbs. /bbl latex powder (SAS-latex mix 25/75 or 1:3), E2) base with 3.0 lbs/bbl SAS and 3.0 lbs/bbl latex powder (SAS-latex 50/50 or 1 :1) and F2) base with 4.5 lbs/bbl SAS and 1.5 lbs/bbl latex powder (75/25 or 3:1 SAS-latex mix). The samples were subjected to hot rolling for 16 hours at 121°C (250°F). The rheological properties of the samples were determined, which are presented in table. 4.

Table 4

Rheology (49°C (120°F)) A2 (base) B2 (SAS) C2 (latex) D2 (25/75 SAS latex) E2 (SAS latex 50/50) F2 (SAS latex 75/25) Viscosity at 600 rpm (cP) 74.90 65.50 81.00 68.40 81.60 75.20 Viscosity at 300 rpm (cP) 51.20 45.50 24.10 46.70 55.10 51.10 Viscosity at 200 rpm (cP) 41.00 40.50 18.70 37.60 45.30 43.20 Viscosity at 100 rpm (cP) 27.90 24.50 12.10 26 31 29.70 Viscosity at 6 rpm (cP) 6.90 6.00 1.90 7.00 8.20 7.60 Viscosity at 3 rpm (cP) 4.80 4.20 1.30 5.80 6.60 6.00 Plastic viscosity (cP) 23.70 20.50 13.40 21.70 26.50 24.10 Yield strength (lb/100 sq. ft) 27.5 15.60 10.70 25.00 28.60 27.00 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 5.1/12.0 3.3/9.5 2.0/3.5 5.9/11.3 6.5/12.7 5.8/11.7

Mud filtration at PPT and fast loss of formation filtrate for six samples was determined at 121°C (250°F) and with a 12 micron disc using the 13B-1 API test kit. The results are presented in table. 5.

- 12 042226

Table 5

Mud Filtration at PPT at 121°C (250°F) A2 (base) B2 (SAS) C2 (latex) D2 (SASlatex 25/75) E2 (SAS latex 50/50) F2 (SAS latex 75/25) minutes 1 2.97 2.97 1.59 2.88 2.02 1.75 5 5.07 4.72 3.79 4.89 4.01 3.45 7.5 5.99 5.51 4.81 5.87 4.73 4.53 10 6.58 6.26 5.38 6.66 5.39 5.00 15 8.15 7.46 6.35 7.86 6.77 5.97 20 9.03 8.39 7.77 9.01 7.90 6.96 25 10.24 9.71 8.79 9.85 8.63 7.92 thirty 11.02 10.28 9.56 10.63 9.66 8.70 PPT (ml) 22.04 20.56 19.12 21.26 19.32 17.40 Rapid absorption of formation filtrate (ml) 2.2 0.0 oh oh 0.1 oh oh oh oh

In FIG. Figure 2 is a graph illustrating the reduced mud filtration in a plugging permeability test (PPT) at 121°C (250°F) for water-based mud compositions containing both SAS and latex powder and having a higher concentration of SAS. than powdered latex, compared to compositions that do not contain one or both of the SAS or latex. Sample F2 (SAS latex 75/25) showed a reduction in drilling fluid filtration at PPT relative to both samples B2 (SAS) and C2 (latex), and also relative to samples D2 (SAS latex 25/75) and E2 (SAS latex 50 /50).

Example 3

The properties of water-based drilling fluid compositions having various concentrations of powdered latex and sodium asphalt sulfonate (SAS) were evaluated. The base mud composition contained 7.0 lbs/bbl bentonite, 2 lbs/bbl polyanionic cellulose, 0.75 lbs/bbl biopolymer, 10 lbs/bbl Rev Dust™ inert material (Milwhite, Inc., Brownsville , Texas), 0.5 lbs/bbl caustic soda, 2 lbs/bbl sodium sulfite, and 20.6 lbs/bbl barite. The base composition had a density of 9.0 lb/gal.

Six samples were prepared: A3) base, BT) base with 6 lbs/bbl SAS, C3) base with 6 lbs/bbl of latex powder, D3) base with 1.5 lbs/bbl SAS or 4.5 lbs. latex powder (28/75 or 1:3 SAS-latex mix), E3) base with 3.0 lbs/bbl SAS and 3.0 lbs/bbl latex powder (50/50 or 1 SAS-latex mix) :1), F3) base with 4.5 lbs/bbl SAS and 1.5 lbs/bbl latex powder (SAS-latex mix 75/25 or 3:1), G3) base with 3.6 lbs/bbl bbl and 2.4 lbs/bbl latex powder (mixture of SAS-Latex 60/40 or 1.5:1), NC) base with 4.2 lbs/bbl and 1.8 lbs/bbl latex powder (blend SAS latex 70/30 or 2.33:1). The samples were subjected to hot rolling for 16 hours at 121°C (250°F). The rheological properties of samples A3-F3 were determined, which are presented in table. 6.

-13042226

Table 6

Rheology at 49°C (120°F) AZ (base) vz (SAS) sz (latex) D3 (SASlatex 25/75) EZ (SASlatex 50/50) F3 (SAS latex 75/25) Viscosity at 600 rpm (cP) 74.90 65.50 81.00 68.40 81.60 75.20 Viscosity at 300 rpm (cP) 51.20 45.50 24.10 46.70 55.10 51.10 Viscosity at 200 rpm (cP) 41.00 40.50 18.70 37.60 45.30 43.20 Viscosity at 100 rpm (cP) 27.90 24.50 12.10 25.90 31.30 29.70 Viscosity at 6 rpm (cP) Viscosity at 3 rpm (cP) 6.90 4.80 6.00 4.20 1.90 1.30 7.00 5.80 8.20 6.60 7.60 6.00 Plastic viscosity (cP) 23.70 20.50 13.40 21.70 26.50 24.10 Yield strength (lb/100 sq. ft) 27.50 15.60 10.70 25.00 28.60 27.00 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 5.1/12.0 3.3/9.5 2.0/3.5 5.9/11.3 6.5/12.7 5.8/11.7

The coefficient of friction (CoF) was determined for samples A3-H3. The recalculated results (100xCoF) are presented in Table. 7.

Table 7

Torque (in lb) AZ VZ (base) (SAS) NW (latex) D3 E3 (SAS-(SAS- latex latex 25/75) 50/50) F3 (SAS latex 75/25) G3 (SAS latex 60/40) NZ (70/30 SAS latex) CoFх100 100 17.8 17.5 14.8 16.6 16.50 15.30 16.6 14.00 150 25.4 24.4 23.4 23.9 23.50 22.40 24.1 22.60 200 31.9 31.8 30.7 31.1 31.50 29.80 31.1 30.70 250 41.2 40.2 39.2 37.8 39.70 37.20 38.8 38.60 300 52.7 48.0 47.4 45.4 47.70 44.40 47.0 45.10 350 67.80 60 55.7 54 56 51.80 55 53.70 400 63.7 62 63.00 65 62.90 450 65.7 71.30

Samples F3 (SAS latex 75/25), G3 (SAS latex 60/40) and H3 (SAS latex 70/30) showed a CoF that was generally lower than samples B1 (SAS) and C1 (latex ), for example, at 250 in-lbs of torque.

Example 4

The properties of water-based drilling fluid compositions having various concentrations of powdered latex and sodium asphalt sulfonate (SAS) were evaluated. The base composition was made in the same manner as described in EXAMPLE 3. Four samples were prepared: A4) base, B4) base with 6 lbs/bbl SAS, C4) base with 6 lbs/bbl latex powder, and D4) base with 4 8 lbs/bbl SAS and 1.2 lbs/bbl latex powder (80/20 or 4:1 SAS-latex mix). The samples were hot rolled for 16 hours at 121°C (250°F). The rheological properties of samples A4-D4 were determined, which are presented in table. 8.

Table 8

Rheology at 49°C (120°F) A4 (base) B4 (SAS) C4 (latex) D4 (SASlatex 80/20) Viscosity at 600 rpm (cP) 94.30 79.00 87.90 38.10 Viscosity at 300 rpm (cP) 64.80 54.60 61.60 24.60 Viscosity at 200 rpm (cP) 51.50 43.70 52.10 18.90 Viscosity at 100 rpm (cP) 35.60 30.50 36.70 12.50 Viscosity at 6 rpm (cP) 7.80 7.50 10.50 2.20 Viscosity at 3 rpm (cP) 6.10 5.70 8.30 1.70 Plastic viscosity (cP) 29.50 24.40 26.30 13.50 Yield Strength (lb/100 sq. ft) 35.30 30.20 35.30 11.10 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 6.4/13.8 6.1/12.4 8.5/17.9 2.3/2.5

Mud filtration at PPT and fast loss of formation filtrate for four samples were determined at 163°C (325°F) using the 13B-1 API test kit. The results are presented in table. 9.

Table 9

Filtration of mud at PPT at 163 °C (325 °F) A4 (base) B4 (SAS) C4 (latex) D4 (SAS latex 80/20) minutes 1 4.60 4.67 3.80 2.76 5 8.16 7.76 6.47 5.84 7.5 10 9.40 10.70 9.15 10.49 8,I 9 7.03 8.39 15 13.31 12.09 11.04 10.07 20 15.21 13.67 12.73 11.65 25 17.05 15.31 14.19 12.88 thirty 18.10 16.65 15.60 13.86 PPT (ml) 36.20 33.30 31.20 27.72 Rapid absorption of formation filtrate (ml) h, o 3.7 1.7 0.6

In FIG. 3 is a graph illustrating the reduced mud filtration at PPT at 163°C (325°F) for water-based mud compositions containing both SAS and latex powder and having a higher concentration of SAS than latex powder compared with compositions that do not contain one or both of SAS or latex.

In FIG. 4 is a graph illustrating PPT mud filtration at 163°C (325°F) for water-based mud compositions containing both SAS and latex powder and having a higher concentration of SAS than latex powder compared to compositions that do not contain one or both of SAS or latex.

Sample D4 with 80/20 SAS-latex blend generally showed a decrease in PPT ghb compared to samples A4 (base), B4 (SAS), and C4 (latex).

- 15 042226

Example 5

The properties of water-based drilling fluid compositions having various concentrations of powdered latex and sodium asphalt sulfonate (SAS) were evaluated. Mud filtration at PPT for base sample A4 from Example 4 and sample D4 containing SAS-latex 80/20 blend were determined at 121, 135, and 149°C (250, 275, and 300°F). Drilling fluid filtration at PPT and fast loss of filtrate by the formation in the case of samples A4 and D4 are presented in Table. 10.

Table 10

Drilling fluid filtration at PPT A4 (base) D4 (SASlatex 80/20) A4 (base) D4 (SASlatex 80/20) A4 (base) D4 (SASlatex 80/20) Temperature 121°C (250 121°C 135°C (275 135°C 149°C (300 149°C (300 minutes °F) (250°F) °F) (275°F) °F) °F) 1 3.31 1,I 3.32 2.66 3.83 2.80 5 6.59 3.99 6.74 5.69 7.87 6.16 7.5 7.92 4.99 8.41 6.65 9.90 8.06 10 9.16 5.96 9.59 8.15 11.61 9,P 15 11.05 8.12 12.05 10.27 14.15 11.61 20 12.67 10.34 14.24 12.05 16.54 13.63 25 14.37 10.73 16.09 13.60 18.74 15.40 thirty 15.77 12.50 17.63 14.49 20.32 16.96 PPT 31.54 25.00 35.26 28.98 40.64 33.92 Rapid loss of formation filtrate 0.9 0.0 oh oh oh oh oh oh 0.00

In FIG. 5 is a graph illustrating the reduced filtration of drilling fluid at

PPT for water-based mud compositions containing both SAS and latex powder and having a higher concentration of SAS than latex powder compared to compositions that do not contain SAS or latex at various temperatures of 121, 135 and 149°C (250, 275 and 300°F)).

As can be seen from Table. 10 and FIG. 5, the 80/20 SAS-latex drilling fluid was stable at 121 to 149°C (250 to 300°F).

Example 6

The properties of water-based drilling fluid compositions containing the same SAS-to-latex ratio but different types of powdered latex were evaluated. A base composition was made in the same manner as described in Example 3. Four samples were prepared: A6) base, B6) base with 4.8 lbs/bbl SAS and 1.2 lbs/bbl Type A (styrene copolymer) latex powder and butadiene, Axilat™ PSB 150, also known as XP-211, Synthomer, Roebuck, SC) (80/20 or 4:1 SAS-latex blend), C6) base with 4.8 lbs/bbl SAS and powdered type B latex 1.2 lbs/bbl (VAE-RS 1220, Riteks, Houston, TX) (80/20 or 4:1 SAS-latex mix) and D6) base 4.8 lbs/bbl SAS and 1, 2 lbs mass/barrel type C latex powder (VAE-RS 1420, Riteks, Houston, TX) (80/20 or 4:1 SAS-latex mix). The samples were hot rolled for 16 hours at 121°C (250°F). The rheological properties of samples A6-D6 were determined, which are presented in table. eleven.

- 16 042226

Table 11 Rheology at 49°C (120°F) Ab (base) Wb (SAS-latex A 80/20) C6 (SAS-latex B 80/20) D6 (S AS-latex From 80/20) Viscosity at 600 rpm (cP) 68.7 61.0 55.6 52.6 Viscosity at 300 rpm (cP) 47.4 41.4 38.1 35.7 Viscosity at 200 rpm (cP) 38.1 33.4 31.0 29.2 Viscosity at 100 rpm (cP) 26.4 23.2 21.5 19.5 Viscosity at 6 rpm (cP) 7.1 6.8 6.2 5.5 Viscosity at 3 rpm (cP) 6.0 5.7 5.0 4.1 Plastic viscosity (cP) 21.3 19.6 17.5 16.9 Yield Strength (lb/100 sq. ft) 26.1 21.8 20.6 18.8 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 5.7/13.1 5.2/10.6 4.7/9.2

PPT drilling fluid filtration and fast filtrate losses for samples A6-D6 were determined at 135°C (275°F) and are presented in Table 1. 12.

Table 12 Filtration of mud at PPT at 135 °C (275 °F) Ab (base) Wb (SAS-latex A 80/20) C6 (SAS-latex B 80/20) D6 (SAS latex C 80/20) minutes 1 3.83 2.80 3.34 2.99 5 7.87 6.16 6.43 6.62 7.5 9.90 8.06 7.67 9.75 10 11.61 9,I 9.05 8.87 15 14.15 11.61 11.64 1.12 20 16.59 13.63 12.76 12.95 25 18.74 15.40 14.24 14.54 thirty 20.32 16.96 15.24 15.42 PPT (ml) 40.64 33.92 30.48 30.84 Rapid absorption of filtrate by the formation (ml) 0.0 0.0 1.2 0.6

In FIG. 6 is a graph illustrating the filtration of drilling fluid during PPT at

135°C (275°F) for water-based drilling fluid compositions containing both SAS and various types of powdered latex and having a higher concentration of SAS than powdered latex compared to compositions that do not contain SAS.

Different types of powdered latex in SAS-latex mixtures exhibited generally similar properties and showed generally similar mud filtration reduction in PPT.

Example 7

The properties of oil-based drilling fluid compositions having various concentrations of SAS and latex were evaluated. The base drilling fluid composition contained 5.0 lbs/bbl of oleophilic clay, 6.0 lbs/bbl of primary emulsifier, 6.0 lbs/bbl of water repellant, 0.5 lbs/bbl of solids Rev Dust™ (Milwhite , Inc., Brownsville, Texas), 25% calcium chloride, 144.3 lbs/bbl barite, 6.0 lbs/bbl lime, and had an oil-to-water ratio of 85/15. The base composition had a density of 11.0 lbs/gal.

- 17042226

Five samples were prepared: A7) base, B7) base with 2.0 lbs/bbl latex powder, C7) base with 4.0 lbs/bbl SAS, D7) base with 3.0 lbs/bbl SAS and 1 .0 lbs/bbl latex powder (SAS-Latex 75/25 or 3:1 mix) and E7) base with 2.0 lbs/bbl SAS and 2.0 lbs/bbl latex powder (SAS-latex 50 mix) /50 or 1:1). The samples were subjected to hot rolling for 16 hours at 121°C (250°F). The rheological properties of samples A7-E7 were determined, which are presented in table. 13.

Table 13

Rheology at 49°C (120°F) A7 (base) B7 (latex) C7 (SAS) D7 (SAS latex 75/25) E7 (SAS latex 50/50) Viscosity at 600 rpm (cP) 63.6 65.0 54.5 60.1 64.7 Viscosity at 300 rpm (cP) 36.4 40.1 29.6 33.0 35.3 Viscosity at 200 rpm (cP) 30.6 32.3 23.0 22.8 24.7 Viscosity at 100 rpm (cP) 20.0 21.5 13.1 12.8 14.3 Viscosity at 6 rpm (cP) 10.4 10.8 3.2 3.2 5.7 Viscosity at 3 rpm (cP) 9.5 10.7 2.7 2.2 5.3 Plastic viscosity (cP) 27.2 24.9 25.0 27.1 29.4 Yield strength (lb/100 sq. ft) 9.2 15.2 4.6 5.9 5.9 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 17.3/34.3 8.4/32.8 2.6/24.2 2.7/27.1 10.6/35.9 Electrical stability(V) 1480 1548 1500 992 965

PPT drilling mud filtration and fast circulation for samples A7-E7 were determined at 135°C (275°F) and are shown in Table 1. 14.

- 18 042226

Table 14

Mud Filtration at PPT at 135°C (275°F) A7 (base) B7 (latex) C7 (SAS) D7 (SAS latex 75/25) E7 (SAS latex 50/50) minutes 1 1.05 1.01 0.47 0.34 0.42 5 1.20 1.73 0.76 0.63 0.72 7.5 2.40 2.08 0.95 0.74 0.84 10 2.57 2.34 1.07 0.88 1.00 15 3.44 2.78 1.28 1.10 1.21 20 3.97 3.19 1.44 1.25 1.37 25 4.32 3.59 1.59 1.38 1.57 thirty 4.69 3.91 1.68 1.51 1.65 PPT (ml) 9.38 7.82 3.36 3.02 3.30 Rapid absorption of filtrate by the formation (ml) 0.0 0.6 0.4 0.1 0.2

In FIG. 7 is a graph illustrating reduced mud filtration at PPT at 135°C (275°F) for oil-based mud compositions containing both SAS and powdered latex and containing SAS at a concentration greater than or equal to that of powdered latex, compared to compositions that do not contain one or both of SAS or latex.

Samples D7 (SAS latex 75/25) and E7 (SAS latex 50/50) showed lower mud filtration at PPT and faster leachate loss compared to samples A7 (base), B7 (latex) and C7 (SAS ).

Example 8

The properties of oil-based drilling fluid compositions having various concentrations of SAS and latex were evaluated. The base drilling fluid composition contained 4.3 lbs/bbl oleophilic clay, 4.25 lbs/bbl primary emulsifier, 0.8 lbs/bbl water repellent, 1.0 lbs/bbl secondary emulsifier, 21.50 lbs/bbl secondary emulsifier, bbl calcium chloride, 53 lbs/bbl barite, 1.86 lbs/bbl lime and had an oil-to-water ratio of 85/15. The base composition had a density of 9.33 lbs/gal.

Four samples were prepared: A8) base, B8) base with 2.0 lbs/bbl latex powder, C8) base with 4.0 lbs/bbl SAS, D8) base with 2.0 lbs/bbl SAS and 2 .0 lbs/bbl latex powder (50/50 or 1:1 mix of SAS-latex). The samples were hot rolled for 16 hours at 121°C (250°F). Rheological properties of samples A8-D8 were determined and presented in table. 15.

- 19042226

Table 15

Rheology at 49°C (120°F) A8 (base) AT 8 (latex) C8 (SAS) D8 (SAS latex 50/50) Viscosity at 600 rpm (cP) 63.6 65.0 54.5 64.7 Viscosity at 300 rpm (cP) 36.4 40.1 29.6 35.3 Viscosity at 200 rpm (cP) 3.6 32.3 23.0 24.7 Viscosity at 100 rpm (cP) 20.0 21.5 13.1 14.3 Viscosity at 6 rpm (cP) 10.4 10.8 3.2 5.7 Viscosity at 3 rpm (cP) 9.5 10.7 2.7 5.3 Plastic viscosity (cP) 27.2 24.9 25.0 29.4 Yield Strength (lb/100 sq. ft) 9.2 15.2 4.6 5.9 Static voltage shear (lb/100 sq. ft) (10 seconds/10 minutes) 17.3/34.3 18.4/32.8 2.6/24.2 10.6/35.9 Electrical stability (V) 1480.0 1548.0 1500.0 965.0

PPT drilling mud filtration and fast circulation for samples A8-D8 were determined at 149°C (300°F) and are shown in Table 1. 16.

Table 16

Drilling Filtration A8 AT 8 C8 D8 solution at PPT at 149 (base) (latex) (SAS) (SAS latex °C (300 °F) 50/50) minutes 1 0.89 0.35 0.48 0.30 5 1.40 0.68 0.91 0.63 7.5 1.79 0.94 1.39 0.85 10 1.90 1.04 1.51 1.07 15 2.11 1.25 1.72 1.23 20 2.23 1.36 1.84 1.37 25 2.40 1.51 1.96 1.49 thirty 2.52 1.66 2.07 1.57 PPT (ml) 5.04 3.32 4.14 3.14 Rapid absorption 1.1 0.1 0.2 oh oh formation filtrate (ml)

In FIG. 8 is a graph illustrating the reduced mud filtration at PPT at 149°C (300°F) for oil-based mud compositions containing both SAS and powdered latex and containing SAS at a concentration that is equal to the concentration of powdered latex compared to compositions that do not contain one or both of SAS or latex.

Sample D8 (50/50 SAS-latex blend) showed reduced mud filtration at PPT compared to samples A8 (base), B8 (latex) and C8 (SAS).

Example 9

The properties of oil-based drilling fluid compositions having various concentrations of SAS and latex were evaluated. The base drilling fluid composition contained 4.0 lbs/bbl of oleophilic clay, 5 lbs/bbl of primary emulsifier, 4 lbs/bbl of water repellent, 25% calcium chloride, 302 lbs/bbl of barite, 4 lbs/bbl of lime and had the ratio oil-water 85/15. The base composition had a density of 13.6 lbs/gal.

- 20 042226

Four samples were prepared: A9) base, B9) base with 4.0 lbs/bbl latex powder, C9) base with 4.0 lbs/bbl SAS, D9) base with 2.0 lbs/bbl SAS

SAS and 2.0 lbs/bbl latex powder (50/50 or 1:1 mix of SAS-latex). The samples were hot rolled for 16 hours at 121°C (250°F). Rheological properties of samples A9-D9 were determined and presented in table. 17.

Table 17

Rheology at 49°C (120°F) A9 (base) B9 (latex) C9 (SAS) D9 (SAS latex 50/50) Viscosity at 600 rpm (cP) 142.7 185.0 138.2 161.4 Viscosity at 300 rpm (cP) 84.6 108.9 74.4 95.8 Viscosity at 200 rpm (cP) 64.7 81.2 60.4 74.1 Viscosity at 100 rpm (cP) 41.1 50.9 35.5 46.5 Viscosity at 6 rpm (cP) 12.8 14.8 10.3 14.1 Viscosity at 3 rpm (cP) 10.7 12.9 9.2 12.2 Plastic viscosity (cP) 58.1 76.1 54.4 65.6 Yield Strength (lb/100 sq. ft) 26.5 32.8 22.5 30.2 Static voltage shear (lb/100 sq. ft) (10 seconds/10 minutes) 11.7/14.5 14/18.2 5.6/14.2 13.1/16.4 Electrical stability (V) 339.0 399.0 400.0 428.0

Filtration at PPT and fast loss of filtrate for samples A9-D9 were determined at 149°C (300°F) and are presented in Table. 18.

and latex and containing SAS at a concentration that is equal to the concentration of powdered latex compared to compositions that do not contain one or both of SAS or latex.

Sample D9 (50/50 SAS-latex blend) showed reduced mud filtration at PPT compared to samples A9 (base), B9 (latex), and C9 (SAS).

Example 10

The properties of compositions of water-based drilling fluids containing various additives were determined. The main drilling fluid composition contained 7.0 lbs/bbl (lbs/bbl) bentonite, 2 lbs/bbl polyanionic cellulose, 0.75 lbs/bbl

- 21 042226 biopolymer, 10 lbs/bbl Rev Dust™ inert material solids (Milwhite, Inc.,

Brownsville, Texas), 0.5 lbs/bbl of caustic soda and 2 lbs/bbl of sodium sulfite. The base composition had a density of 9.5 lb/gal.

Ten samples were prepared: AJ) base, B10) base with 6 lbs/bbl of SAS mixed with causticized lignite (Soltex®, Drilling Specialties Company, Woodlands, TX), SC) base with 6 lbs/bbl of asphalt 1 (Anco Phalt™, Anchor Drilling Fluids, Tulsa, Oklahoma), D10) 6 lbs/bbl asphalt base 2 (Asphasol Supreme™, MI Swaco, Houston, TX), EY) 6 lbs/bbl asphalt base 3 (Baro- Trol® Plus, Halliburton, Houston, TX), F10) 6 lb.m base/bbl asphalt 4 (Martrol, Marbar SRL, Buenos Aires, Argentina), G10) 6 lb.m base/bbl asphalt 5 (NewPhalt™, Newpark Drilling Fluids, The Woodlands, TX) NY) 6 lbs/bbl Gilsonite 1 base (Super-Bore-Trol™, Servicios Petroleros ZV, Monterrey, Mexico), PO) 6 lbs/bbl Gilsonite 2 (Super Shield™, Patriot, Kenner, LA) and LO) base with 4.8 lbs/bbl SAS and 1.2 lbs/bbl powdered hot latex (latex blend) (SAS-latex blend 4:1 or 80/20). The samples were hot rolled for 16 hours at 121°C (250°F). PPT drilling mud filtration and fast loss of filtrate for the samples were determined at 135°C (275°F) and are presented in Table. 19.

Table 19

Mud Filtration at PPT at 135°C (275°F) AYu AT 10 SU D10 EY F10 G10 NUDE BY lo minutes 1 3.98 2.14 2.24 3.66 4.31 4.17 4.04 2.86 3.34 1.70 5 7.02 4.30 4.51 6.30 6.27 6.70 6.04 5.22 5.73 4.10 7.5 8.53 5.05 5.21 7.47 7.28 7.89 7.18 6.08 6.66 4.80 10 9.38 5.83 5.85 8.35 7.89 8.93 7.80 6.84 7.53 5.50 15 11.43 7.48 6.83 10.25 8.82 10.10 8.87 7.67 8.61 6.83 20 12.99 8.44 8.61 11.79 9.86 11.65 9.90 9.09 9.49 7.56 25 14.42 9.30 9.24 13.30 10.85 11.93 10.93 10.06 10.75 8.83 thirty 15.32 10.38 9.92 13.97 11.47 13.05 11.96 10.92 11.67 9.45 PPT (ml) 39.12 20.76 19.84 27.94 22.94 26.10 23.92 21.84 23.34 18.90 Rapid absorption of the filter by the formation (ml) 2.8 0.5 1.2 2.5 5.4 4.5 4.3 2.3 3.1 0.2

In FIG. 10 is a graph illustrating the reduced filtration of drilling fluid at PPT and the rapid loss of filtrate by the formation at 135°C (275°F) for water-based drilling fluid compositions containing both SAS and latex powder and containing SAS at a concentration that is greater than than powdered latex, compared with compositions containing other additives.

Sample J10, containing a mixture of SAS-latex, showed lower PPT mud filtration and faster filtrate losses than all other samples.

Example 11.

The properties of compositions of oil-based drilling fluids containing various

-22042226 additives. The base drilling fluid composition contained 9.0 lbs/bbl of oleophilic clay, 4.0 lbs/bbl of primary emulsifier, 6.0 lbs/bbl of water repellent, 20 lbs/bbl of Rev Dust™ inert material (Milwhite, Inc.) ., Brownsville, Texas), 161.2 lbs/bbl barite, 6.0 lbs/bbl lime, 2.0 lbs/bbl sodium sulfite, and had an oil-to-water ratio of 85/15. The base composition had a density of 11.0 lbs/gal.

Ten samples were prepared: A11) Base, B11) Base with 2 lbs/bbl Gilsonite 2 (BARABLOK™ Filtration Control Additive, Halliburton, Houston, TX), C11) Base with 2 lbs/bbl Asphalt 1 (Shale Inhibitor) BARO-TROL® PLUS, Halliburton, Houston, TX), D11) 2 lb. mass base/bbl of asphalt 2 (Carbo-Trol™ mud reducer, Baker Hughes, Houston, TX), E11) 2 lb. mass base/ Gilsonite 2 bbl (Ecco-Block™ Filtration Regulator, Baker Hughes, Houston, TX), F11) 1.6 lb wt/bbl SAS base and 0.4 lb wt/bbl latex powder (4:1 or 80/20 SAS/latex blend) ), G11) 2 lbs/bbl Gilsonite base 3 (Gilsonite® HT, American Gilsonite Company, Houston, TX), H11) 2 lbs/bbl SAS base, I11) 6 lbs/bbl Asphalt 3 base ( xylan) and J11) base with 4.8 lbs/bbl Gilsonite 4 (Versatrol™, MI Swaco, Houston, Texas). The samples were subjected to hot rolling for 16 hours at 121°C (250°F).

The rheological properties of the samples were determined at 66°C (150°F) and are presented in table. 20.

Table 20

Drilling fluid filtration at PPT at 149°C (300°F) AP vp joint venture D11 EP F11 G11 NO Ill L1 Viscosity at 600 rpm (cP) Viscosity at 300 rpm (cP) 47.9 27.6 48.9 26.3 50.8 31.0 48.4 28.8 52.4 31 50.3 27.7 51.8 thirty 54.4 32.2 59.5 29.6 49.9 28.9 Viscosity at 200 rpm (cP) 19.7 18.2 24.5 20.1 23.9 18.5 23.5 23.2 29.6 28.9 Viscosity at 100 rpm (cP) 13.5 12.0 16.2 13.7 14.9 12 14.7 14.6 13.7 13.1 Viscosity at 6 rpm (cP) 5.9 4.7 6.1 5.6 5.8 4.6 5.9 4.8 5.5 5.1 Viscosity at 3 rpm (cP) 5.5 4.3 5.7 5.4 5.4 4.2 5.5 4.6 5.2 4.8 Plastic viscosity (cP) 20.3 22.6 19.8 19.6 21.4 22.6 21.8 22.2 20.3 21 Yield Strength (lb/100 sq. ft) 7.3 3.7 P,2 9.2 9.6 5.1 8.2 10 9.3 7.9 static voltage shear (lb/100 sq. feet) (10 seconds/10 minutes) 7.4/9.9 6.8/8.9 8.2/11.1 7.6/10.7 7.5/9.9 7.2/11.6 7.7/10.4 6.9/11.7 7.3/10.3 7.1/10.3 Electrical stability (V) 1367 1513 1325 1364 1403 1804 1558 1944 1643 1680

- 23 042226

Sample F11, containing the SAS-latex mixture, showed higher electrical stability than all other samples, except for sample H11, containing SAS.

PPT drilling mud filtration and fast loss of filtrate for the samples were determined at 149°C (300°F) and are presented in Table. 21.

Table 21

Mud Filtration at PPT at 149°C (300°F) AN IN AND SI D11 E11 F11 G11 NO Ill L1 minutes 1 2.23 1.63 1.43 1.48 1.62 1.20 1.74 1.50 1.44 1.40 5 2.76 2.32 2.65 2.62 2.16 1.87 2.67 1.94 2.13 1.88 7.5 3.26 2.85 3.15 3.02 2.57 2.14 3.07 2.46 2.48 2.32 10 3.62 3.06 3.87 3.49 2.74 2.55 3.87 2.64 2.74 2.59 15 3.95 3.39 4.54 3.99 3.01 2.76 3.67 2.95 3.11 2.96 20 4.21 3.59 4.97 4.45 3.24 3.01 4.03 3.24 3.45 3.22 25 4.51 3.85 5.37 4.82 3.52 3.24 4.35 3.52 3.70 3.45 thirty 4.77 4.09 5.73 5.09 3.83 3.50 4.70 3.80 4.07 3.65 PPT (ml) 9.54 8.18 11.46 10.18 7.66 7.00 9.40 7.60 8.14 7.30 Rapid absorption of filtrate by the formation (ml) 3.10 2.41 1.09 1.58 2.31 1.53 2.43 1.92 1.70 1.60

In FIG. 11 is a graph illustrating the reduced filtration of drilling fluid at

PPT and fast loss of filtrate at 149°C (300°F) for oil-based drilling fluid compositions containing both SAS and powdered latex and containing SAS at a concentration that is greater than powdered latex, compared to compositions, containing other additives.

Sample F11, containing a mixture of SAS-latex, showed lower mud filtration at PPT and faster loss of filtrate than all other samples.

Example 12.

The properties of water-based drilling fluid compositions having various concentrations of SAS and latex powder were evaluated. The base drilling fluid composition contained 5.0 lbs/bbl (lbs/bbl) bentonite, 17.5 lbs/bbl potassium chloride, 0.5 lbs/bbl at Polymer 1 HPHT, at Polymer 2 HPHT, 25% diluent , 50 lbs/bbl calcium carbonate and 0.75 lbs/bbl caustic. The base composition had a density of 10.0 lb/gal.

Three samples were prepared: A12) base, B12) base with 6 lbs/bbl SAS and C12) base with 4.8 lbs/bbl SAS and 1.2 lbs/bbl latex powder (80/20 SAS-latex blend) or 4:1). The samples were hot rolled for 16 hours at 121°C (250°F). The rheological properties of samples A12-C12 were determined, which are presented in table. 22.

- 24 042226

Table 22

Rheology at 49°C (120°F) A12 (base) B12 (SAS) C12 (SAS latex 80/20) Viscosity at 600 rpm (cP) 90.2 103.1 99.1 Viscosity at 300 rpm (cP) 62.4 78.4 70.4 Viscosity at 200 rpm (cP) 49.4 61.1 56.8 Viscosity at 100 rpm (cP) Viscosity at 6 rpm (cP) 34.6 6.7 43.1 9.5 40.1 8.1 Viscosity at 3 rpm (cP) 4.4 7.3 5.9 Plastic viscosity (cP) 27.8 29.7 28.7 Yield Strength (lb/100 sq. ft) 34.6 43.7 41.7 Static shear stress (lb/100 sq. ft) (10 seconds/10 minutes) 3.2/5.3 9.0/6.1 6.3/5.1

HPHT mud filtration and API mud filtration for samples A12-C12 were determined at 191°C (375°F) and are shown in Table 1. 23.

___________________________________________________________ Table 23

Filtration of drilling mud at HTHP at 191 °C (375 °F) A12 (base) B12 (SAS) C12 (SAS latex 80/20) minutes 1 3.68 3.40 3.31 5 5.82 5.39 5.23 7.5 10 6.83 7.35 6.30 7,I 6.19 6.91 15 8.69 8.45 8.32 20 9.82 9.68 9.48 25 10.79 10.68 10.46 thirty 11.60 11.50 11.25 NTNR (ml) 23.20 23.00 22.50 API filtrate (ml) 3.4 4.1 3.1

In FIG. 12 is a graph illustrating API and HPHT filtrate volumes at 191°C (375°F) for water-based drilling fluid compositions containing both SAS and powdered latex and containing SAS at a concentration that is greater than powdered latex, by compared to compositions that do not contain one or both of SAS or latex.

Sample C12 with a mixture of SAS-latex showed lower mud filtration at HPHT and lower mud filtration at API than the other samples.

Example 13

The properties of water-based drilling compositions containing various concentrations of SAS, powdered latex and liquid latex were determined. The base mud composition contained 7.0 lbs/bbl (lbs/bbl) bentonite, 17.5 lbs/bbl potassium chloride, 2 lbs/bbl SL Drispac® polymer (Drilling Specialties Company, Woodlands, TX), 0 .75 lbs/bbl of Flowzan® biopolymer (Drilling Specialties Company, Woodlands, TX) and 0.75 lbs/bbl of caustic. The base composition had a density of 9.2 lbs/gal.

Four samples were prepared: A13) base, B13) base with 6 lbs/bbl SAS, C13) base with 4.8 lbs/bbl SAS and 1.2 lbs/bbl latex powder (80/20 SAS-latex blend) or 4:1) and D13) base 9 lbs/bbl liquid latex. The samples were hot rolled for 16 hours at 66°C (150°F).

-25042226

The rheological properties and shale recovery of samples A13-D13 were determined, which are presented in table. 24.

Table 24

Rheology at 49°C (120°F) A13 (base) B13 (SAS) C13 (SAS powders various latex 80/20) D13 (liquid latex) Viscosity at 600 rpm (cP) 58.8 64.1 58 63.3 Viscosity at 300 rpm (cP) 39.8 44.5 39.8 42.1 Viscosity at 200 rpm (cP) 31.8 37.2 31.8 33.3 Viscosity at 100 rpm (cP) 22.3 26.6 22.3 22.3 Viscosity at 6 rpm (cP) 6.6 8.7 6.6 5.1 Viscosity at 3 rpm (cP) 5.2 6.7 5.2 3.7 Plastic viscosity (cP) 19 19.6 19 21.2 Yield Strength (lb/100 sq. ft) 20.8 24.9 20.8 20.9 Static voltage shear (lb/100 sq. ft) (10 seconds/10 minutes) 5.6/9.5 7.3/9.9 5.6/9.5 4.9/5.8 % oil shale recovery 75.82 68.07 91.7 88.95

Sample C13 with a mixture of SAS-powdered latex showed the highest shale recovery.

Example 14

Several field samples of oil-based mud (the first sample was an 82/18 OWR, 13.8 lb/gal 82/18 field mud sourced from the Eagle Ford area, and the second sample was 9.5 lb mass/gal OWR field mud sourced from the Rocky Mountains) were tested for lubricity using a variety of methods, including an extreme pressure (EP) lubricity meter and a dynamic lubricity meter. abilities (LEM; lubricant evaluation monitor). A solid lubricant (4:1 or 80/20 SAS-latex blend) was tested using a tribometer to obtain a continuous Stribeck curve that allows the lubricant to be evaluated over the entire lubricity regime. The CoF results using the EP lubricity meter were converted to calculate the Striebeck number to fit the curve. A decrease in CoF in the boundary lubrication region occurs when the borehole and bit/BHA roughnesses are in contact. This is due to the adsorption of the new solid state lubricant on the uneven surfaces, resulting in a smooth surface. The new solid lubricant has a wide particle distribution (PSD) to cover bumps of various sizes and heights. The Striebeck curves for the new solid lubricant show that the lubricant can reduce CoF in the boundary lubrication region where the frictional forces are highest compared to the base fluid and other fluid lubricants.

Lubricity meter for EP. The more common lubricity test measures the flow resistance of various lubricant additives. The standard lubricity index test is performed at 60 rpm with 150 in-lbs of force (equivalent to an intermediate fluid pressure of about 600 psi (4137 kPa)) and applied to two hardened steel surfaces, a rotating ring and fixed block. Friction is measured as CoF (μ). CoF between two solids is defined as the load friction force or the force perpendicular to the surfaces. CoF is independent of visible contact areas as long as this area is not small enough to break the film. The force to overcome friction will be the same for a small area as for a larger area. The force F required to slide the block and ring surfaces against each other at a given speed is measured by the force required to rotate the shaft of the test ring at a given rpm. Coefficient of friction (CoF; Coefficient of Friction), μ=meter reading/load or force.

- 26 042226

Measuring instrument for evaluating lubricity. The Lubricity Meter (LEM) is a laboratory device designed to evaluate lubricants by direct comparison. It determines the CoF between a replacement sample from a wellbore (casing, formation, sandstone, etc.) pressed against a rotating steel disk while immersed in a circulating test fluid cup. LEM measures relative coefficients of friction at ambient temperature and pressure. It is specifically designed to compare the lubricity of different fluid systems and/or fluid additives. The device may use friction materials such as sandstone or casing. The pneumatic plunger applies a side load by pressing the disc against the specimen, periodically renewing the test fluid by pulling the disc away from the specimen at preset intervals. The clamp allows you to test samples of casing, formation, sandstone, etc. in the same fixture. LEM has computerized data acquisition and control software. The user enters the parameters of rotation speed, side load and updates. Archived test databases provide access to historical data graphs that include: rotational speed (rpm), torque (in-lb), side load (lb) and CoF versus time. The test is started and the machine collects 600 data points or operates until the CoF values stabilize.

Tribometer. When lubrication is used to reduce wear/friction of moving surfaces, the lubrication contact at the interface can change from mode to mode, for example, operating in the modes of boundary, mixed and hydrodynamic lubrication. An important role in this process is played by the thickness of the liquid film, mainly determined by the viscosity of the liquid, the load applied at the interface, and the relative velocity between the two surfaces. The way lubrication regimes respond to friction is shown in the so-called Striebeck curve. The trobometer demonstrates a method capable of measuring a continuous Stribeck curve. Using advanced stepless speed control from 2000 to 0.01 rpm for 10 minutes, the software directly outputs the complete Stribeck curve. The simple initial setup only requires users to select the exponential rate mode and enter the start and end speeds, rather than running a series of tests or programming a step-by-step procedure at different speeds that requires data stitching for normal Stribeck curve measurements. The Striebeck curve plots CoF as a function of viscosity, speed and load. The vertical axis represents CoF and the horizontal axis is a parameter that combines other variables. Purpose of measurement: Stribeck curves were measured using two lubricating oils with different kinetic viscosities for comparison. A rod-disk tribometer equipped with a lubrication module was used. The rotation speed was reduced exponentially from 2000 rpm to 0.01 rpm to demonstrate the continuous measurement of the Stribeck curve and the precise sensitivity of the tribometer functionality.

Initial lubricity data were obtained using a standard EP lubricity meter. Typically CoF is determined based on a 150 in-lb torque load at 60 rpm rotation. However, when plotting CoF versus base fluid torque load and base fluid containing 2 and 3 lbs/bbl of solid lubricant (4:1 or 80/20 SAS-latex blend), the shape of the corrected curve had a characteristic profile. As seen in FIG. 13, the solid lubricant (4:1 or 80/20 SAS-latex blend) had a lower CoF at lower torque loads. In FIG. 13 is a graph illustrating the change in coefficient of friction with torque for oil-based drilling fluid compositions containing a solid lubricant.

Example 15

The results of the EP lubricity meter were then plotted to plot the Striebeck curve. The x-axis displays the Striebeck number=η*V/W calculated using RPM (60) and load torque with dynamic viscosity assuming 1 to observe the curve profile in another approach. The results are shown in FIG. 14 showing solid lubricant behavior (4:1 or 80/20 SAS-latex blend) at 2, 3, and 4 lbw/bbl in boundary lubrication mode at lower Striebeck numbers. The lubricant reduces the CoF at the boundary conditions compared to the base fluid. In FIG. 14 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions with and without solid lubricant. The base drilling fluid composition contained 8.2 lbs/bbl with a 90/10 OWR (oil to water ratio) of Gibson D822 oil (Gibson Energy, Houston, Texas).

The same method was used to calculate the Stribeck curve for the same fluid containing 10 lbs/bbl solids of inert Rev Dust™ (Milwhite, Inc., Houston, Texas). The effect on CoF of a sample with 2.0 lbs/bbl of lubricant is evident in the presence of

- 27 042226 simulated low density solid particles in boundary conditions. In FIG. 15 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions excluding and containing solid lubricant and particle friction reducing material. The base drilling fluid composition contained 8.2 lbs/bbl OWR 90/10 with Gibson D822 oil (Gibson Energy, Houston, Texas).

A different base fluid was used to test the lubricant and the results are shown in FIG. 16. The effect of lubricant on lubrication boundary conditions was noted when using mineral oil-based mud (OBM) with OWR 90/10 with 5.0 lbs/bbl organophilic clay. The base drilling fluid composition contained 8.2 lbs/bbl OWR 90/10 with HT 40 PureDrill™ oil (Petro-Canada, Mississauga, Canada). In FIG. 16 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions excluding and containing solid lubricant and organophilic clay.

Example 16

CoF was tested with a dynamic lubricity meter. Unlike the EP lubricity meter, where CoF was measured using the same film as the torque load was increased, the LEM contact between the rotor and block is constantly updated as fluid is circulated. The tests were carried out in several stages until a stable dynamic CoF was obtained.

A laboratory sample of OWR 85/15 and 11.0 lbs/gal diesel OBM and a base fluid sample with 2.0 lbs/bbl of solid lubricant were tested in the LEM. Although the measured CoF of both samples was 0.12, evaluation of the data showed that the liquid containing no solid lubricant had a higher static CoF compared to the liquid containing solid lubricant. The static CoF is the maximum peak observed in the initial part of each stage when the rotor begins to move in the boundary conditions.

Example 17.

The Striebeck curves of liquids containing a solid lubricant (mixture of SAS-latex 4:1 or 80/20) were compared with liquid lubricants and their performance under boundary conditions. The tribometer can create a continuous Striebeck curve when changing the rotation speed from 0.01 to 1000 rpm. For practical purposes, tool rotation speeds from 0.01 to 250 rpm were used. When measuring CoF values, a fixed load of 150 in-lbs was also selected.

The same fluid tested in the LEM was used to plot the Stribeck curves with a tribometer. Four tests were performed involving base fluid (BF) and base fluid samples containing 2.0 lbs/bbl of solid lubricant and 2 vol% of two fluid lubricants. The results are shown in FIG. 17, 18 and 19.

In FIG. 17 is a graph illustrating the coefficient of friction versus time for a base oil based drilling fluid composition. In FIG. 18 is a graph illustrating the coefficient of friction versus time for a base oil drilling fluid composition containing a solid lubricant. In FIG. 19 is a graph illustrating friction coefficient vs. Striebeck number for oil-based drilling fluid compositions without lubricant, containing a solid lubricant, and containing two different liquid lubricants.

Lubricant 2 (Torque-Buster, Franklin Well Services, Vincennes, Ind.) exhibited poor performance and adversely affected base fluid CoF. Lubricant 1 (Turbo-Lube, Farm-Oyl®, St. Paul, MN) performed better than Lubricant 2, providing a slight reduction in static CoF and similar CoF dynamics. The solid state lubricant contributed to the reduction of static and dynamic CoF across the entire RPM range.

The dynamic CoF of the base fluid from 2.0 lbs/bbl solid lubricant continuously decreases after 1.2 minutes. Conversely, of the fluid lubricants tested, one of the fluid lubricants did not show an improvement in CoF, static or dynamic, and the other had an adverse effect on CoF, both static and dynamic.

Without being limited by theory, the solid lubricant acts in a boundary lubrication mode to form a lubricating film that reduces the viscosity.

Example 18.

Field trials using the new solid lubricant were carried out in the Permian Basin using a water-based direct emulsion drilling fluid. The purpose of the field trial was to evaluate the potential replacement of OBM with direct emulsion drilling fluid and

- 28 042226 solid state lubricant (mixture of SAS-latex 4:1 or 80/20). The solid lubricant was added by applying pellets at a concentration of 3.0 lbs/bbl to reach a final concentration of 3.0 lbs/bbl in the circulating system. The operator increased the concentration to

6.0 lbs/bbl for total interval depth.

A snapshot of field trials conducted in the Permian Basin was evaluated. An overall increase in rate of penetration (ROP) of 6.0 lbm/bbl compared to 3.0 lbm/bbl of solid lubricant was noted and a similar torque load was maintained.

The top weight and bottom weight were recorded along the horizontal section. In FIG. 20 is a graph illustrating the change in top weight and bottom weight across a horizontal section as a function of depth. Although both top weight and bottom weight are expected to increase as depth increases, both curves show a decrease in both measurements. The trend of both curves becomes smooth when the solid lubricant concentration reaches 3.0 lb mass/bbl in the entire system.

The present invention has been described above with numerous aspects and embodiments, as well as specific examples. Many variations will be apparent to those skilled in the art in light of the above detailed description. All such obvious modifications are included within the full intended scope of the appended claims. Other aspects of the present invention may include, without limitation, the following aspects. Many aspects are described as including certain components or steps, but in the alternative, they may essentially consist of or consist of the specified components or steps, unless specifically indicated otherwise.

Claims (28)

CLAIM 1. The composition of the drilling fluid containing the first concentration of powdered latex; and a second concentration of sodium asphalt sulfonate (SAS), wherein the second concentration of SAS is greater than or equal to the first concentration of latex by weight, wherein the first concentration of powdered latex is at least about 1 lb mass per barrel (lb mass/bbl) relative to drilling fluid composition, and wherein the powdered latex contains at least one of a copolymer of styrene and butadiene or a copolymer of vinyl acetate and ethylene. 2. A drilling fluid composition according to claim 1, characterized in that the second concentration of SAS is greater than the first concentration of latex. 3. A drilling fluid composition according to any one of claims 1 and 2, wherein the latex powder has an aggregate average particle size in the range of about 70 microns to about 100 microns. 4. The drilling fluid composition of claim 3, wherein the population mean particle size is in the range of about 80 µm to about 90 µm. 5. A drilling fluid composition according to claim 4, characterized in that the population average particle size is about 85 microns. 6. The drilling fluid composition according to any one of claims 1 to 5, characterized in that the drilling fluid composition contains a water-based carrier, wherein the second concentration of SAS is greater than the first concentration of latex, and wherein the drilling fluid composition has an average filtration of the drilling fluid High Temperature High Pressure (HPHT) at 121°C (250°F) and 500 psi (psi) less than or about 20 ml when tested in accordance with the American Petroleum Institute (API) test 13B-1 ). 7. The drilling fluid composition of claim 6 having a friction coefficient of less than or about 0.40 at 250 lb-ft torque. 8. A drilling fluid composition according to claim 6 or 7, wherein the drilling fluid composition has an average filtration in a plugging permeability test (PPT) at 121°C (250°F) with a 12 micrometer filter disc of less than or about 18.0 ml when tested in accordance with API test 13B-1. 9. A drilling fluid composition according to any one of claims 6-8, wherein the drilling fluid composition has a plastic viscosity at 49°C (120°F) in the range of about 20 centipoise to about 30 centipoise when tested in accordance with Test 13B. -1 American Petroleum Institute (API). 10. A drilling fluid composition according to any one of claims 6-9, wherein the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 20 lb/100 sq. ft to about 45 lbs/100 sq. feet when tested in accordance with the American Petroleum Institute (API) test 13B-1. - 29 042226 11. The drilling fluid composition according to any one of claims 6-10, characterized in that the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) in the range of about 5.5 lbs/100 sq. ft to about 6.5 lb/100 sq. feet when tested as per test 13B-1 American Petroleum Institute (API). 12. A drilling fluid composition according to any one of claims 6-11, wherein the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 5 lb/100 sq. ft to about 12 lbs/100 sq. feet when tested in accordance with the American Petroleum Institute (API) test 13B-1. 13. The drilling fluid composition according to any one of claims 6-12, characterized in that the first concentration of powdered latex is at least 1 lb mass per barrel (lb mass/bbl), while the second concentration of SAS is at least 2 lb mass /barrel. 14. The drilling fluid composition of claim 13, wherein the first concentration of latex powder is in the range of about 1.5 lbs/bbl to about 2.5 lbs/bbl, wherein the second concentration of SAS is in the range of about 2.5 lbs/bbl to about 3.5 lbs/bbl. 15. The drilling fluid composition of claim 14 wherein the first concentration of powdered latex is about 2 lbs/bbl and the second concentration of SAS is about 3 lbs/bbl. 16. The drilling fluid composition of claim 13 wherein the first concentration of powdered latex is about 1.5 lbs/bbl and the second concentration of SAS is about 4.5 lbs/bbl. 17. The drilling fluid composition of claim 13, wherein the first concentration of powdered latex is about 1.2 lbs/bbl and the second concentration of SAS is about 4.8 lbs/bbl. 18. A method comprising dispersing a first predetermined amount of powdered latex and a second predetermined amount of SAS in an aqueous carrier to form an aqueous drilling fluid containing any of the compositions of claims 1-17. 19. The drilling fluid composition according to any one of claims 1 to 5, characterized in that the drilling fluid composition contains an oil-based carrier, while the drilling fluid composition has an average filtration of the drilling fluid in a well plugging permeability test (PPT) at 149° C (300°F) with 55 µm filter disc less than or about 1.06 ml when tested in accordance with API test 13B-2. 20. The drilling fluid composition of claim 19, wherein the drilling fluid composition has a plastic viscosity at 49°C (120°F) in the range of about 20 centipoise to about 30 centipoise when tested in accordance with API Test 13B-2. 21. A drilling fluid composition according to claim 19 or 20, wherein the drilling fluid composition has a yield strength at 49°C (120°F) in the range of about 5 lb/100 sq. ft to about 6 lbs/100 sq. feet when tested in accordance with API test 13B-2. 22. A drilling fluid composition according to any one of claims 19-21, wherein the drilling fluid composition has a 10 second static shear stress at 49°C (120°F) in the range of about 2 lb/100 sq. ft to about 11 lbs/100 sq. feet when tested in accordance with API test 13B-2. 23. A drilling fluid composition according to any one of claims 19-22, wherein the drilling fluid composition has a 10 minute static shear stress at 49°C (120°F) in the range of about 10 lb/100 sq. ft to about 40 lbs/100 sq. feet when tested in accordance with API test 13B-2. 24. A drilling fluid composition according to any one of claims 19-23, wherein the first concentration of powdered latex is at least about 1 pound mass per barrel (lb mass/bbl), while the second concentration of SAS is at least about 1 pounds mass/barrel. 25. The drilling fluid composition of claim 24 wherein the first concentration of latex powder is about 1 lbw/bbl and the second concentration of SAS is about 3 lbw/bbl. 26. The drilling fluid composition of claim 24, wherein the first concentration of powdered latex is in the range of about 1.5 lbs/bbl to about 2.5 lbs/bbl, wherein the second concentration of SAS is in the range of about 1.5 lbs/bbl to about 2.5 lbs/bbl. 27. The drilling fluid composition of claim 24, wherein the first concentration of latex powder is about 2 lbs/bbl and the second concentration of SAS is about 2 lbs/bbl. 28. A method for drilling a well in subterranean formations, comprising dispersing a first predetermined amount of powdered latex and a second predetermined amount of SAS in a carrier in an oil - 30 042226 base to form an oil-based drilling fluid containing a composition according to any one of claims 1-5 and 19-27.