CN101124307A - Additives to reduce drill string torque - Google Patents

Abstract

A method of reducing the torque of a drill string used in drilling a subterranean well that includes injecting into the drilling fluid a composition including a base fluid and a polymer coated colloidal solid material. The polymer coated colloidal solid material includes: a solid particle having an weight average particle diameter (d5o) of less than ten microns, and a polymeric dispersing agent coated onto the surface of the solid particle during the cominution (i.e. grinding) process utilized to make the colloidal particles. The polymeric dispersing agent may be a water soluble polymer having a molecular weight of at least 2000 Daltons. The solid particulate material may be selected from materials having of specific gravity of at least 2.68 and preferably the solid particulate material may be selected from barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine, siderite, strontium sulfate, combinations and mixtures of these and other similar solids that should be apparent to one of skill in the art.

Description

Additives to reduce drill string torque

Background technique

When drilling oil and gas wells, fluid formulations with various properties (including lubricity) are pumped downhole through the drill string and ejected through nozzles in the drill bit, so that the drilling fluid passes through the annulus between the rotating drill string and the rock formation upward circulation. The function of these drilling fluids, or "muds," is to cool and lubricate the drill bit and drill string, carry cuttings from the drilling process to the surface, control and reduce fluid loss into the formation, and support and protect the borehole until the metal casing is in place Glue firmly (ie, create a stable hole).

Mud lubricity (to minimize torque and drag) and mud toxicity (for wells in environmentally sensitive areas such as offshore drilling) are major concerns when selecting a drilling fluid formulation. Most drilling fluids can be classified into two main categories: water-based or oil-based. Most of the drilling fluids used today are water based, ie they contain water as the continuous external phase. Despite the performance advantages of oil-based drilling fluids comprising so-called synthetic-based fluids, their disadvantages are higher cost and difficulty in achieving environmental protection in certain regions of the world.

The lubricity of a drilling fluid is an important factor in drilling economics as measured by determining the effect of the drilling fluid on the coefficient of friction between moving parts such as the drill string and surfaces in contact with the moving parts. The lower the coefficient of friction, the greater the lubricity. The lubricity of a drilling fluid determines the fluid's ability to reduce torque and drag during drilling operations.

The prior art is replete with reports of various lubricants used to reduce drill string torque. For example, various types of hydrocarbons, synthetic oils, esters, fatty acids, natural oils, soaps, and other compounds have been added to drilling fluids to help reduce torque. Organic oil-based lubricants are often added to water-based drilling fluids to reduce the coefficient of friction. Reducing the coefficient of friction during drilling is particularly important in drilling operations where the wellbore is not vertical. Emulsifiers or surfactants are often added to drilling fluids to keep these water-insoluble oil-based lubricant components suspended as droplets in the water-based fluid and prevent them from separating and merging. These lubricants may increase the toxicity and irritation levels of the fluid.

In addition to fluid lubricants, micron-sized solid particles or beads can also be added to water-based drilling fluids to improve their lubricity. Some representative examples of this type of lubricant system are: (1) thermally stable and chemically inert ceramic balls that are resistant to wear and fracture; (2) plastic beads, for example, made of a copolymer of divinylbenzene and styrene (3) bead-shaped magnetic particles coated with plastic to facilitate movement and circulation of these bead compositions; (4) chemically resistant soda-lime-silica glass beads; (5) elastic graphitic carbon particles (6) Cellulose, peat or bagasse containing adsorbed oil-based fluid lubricants; (7) Mixtures of graphite, silicate and silicone materials. A general difficulty with the solid lubricants described above is the environmental concerns and loading of the solid material by the drilling fluid when using water-based drilling fluids. Furthermore, it should be appreciated that the addition of solid materials that do not contribute to the weight gain of the fluid may lead to underweight fluid uplift problems associated with spillage or wall collapse. A further problem encountered with solid lubricants is that the small diameter holes present in the valves and other flow and pressure control devices used may not allow the use of solid particle lubricants because these materials obstruct and plug the narrow restrictions. A more serious problem is that the solids may be difficult to remove from the wall holes, thereby leading to the formation of damage. Despite continued efforts in this field, there remains and exists an unmet need for a fluid that reduces drill string torque without exhibiting problems of solids settling, high viscosity, toxicity, and overall fluid weight reduction.

Contents of the invention

The present invention relates generally to fluids for reducing drill string torque, and methods of making and using such fluids. The fluids of the present invention include a polymer-coated colloidal solid material that has been coated with the added polymer during comminuting (ie, grinding) to prepare the polymer-coated colloidal solid material.

One illustrative embodiment of the invention includes a method of reducing torque in a rotating drill string assembly. In this illustrative method, the method includes injecting into a drilling fluid a composition comprising a base fluid and a polymer-coated colloidal solid material. The polymer-coated colloidal solid material includes: solid particles coated with a polymer dispersant adsorbed on the surface of the solid particles. The polymeric dispersant is adsorbed onto the surface of the solid particles during comminution (ie, grinding) used to prepare the polymer-coated colloidal solid material. The base fluid used in the above illustrative embodiments may be an aqueous fluid or an oily fluid, preferably selected from the group consisting of: water, brine, diesel oil, mineral oil, white oil, n-paraffin, synthetic oil, saturated and unsaturated poly(alpha - olefins), fatty acid carboxylates, and combinations and mixtures of these and similar fluids that should be apparent to those skilled in the art. Suitable and illustrative colloidal solids are selected such that the solid particles consist of a material having a specific gravity of at least 2.68, preferably selected from the group consisting of: barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine , meteoric iron, strontium sulfate, combinations and mixtures of these substances and other suitable substances that should be known to those skilled in the art. In a preferred illustrative embodiment, the polymer-coated colloidal solid material has a weight average particle size ( _d50 ) of less than 10 microns. Another preferred illustrative embodiment is that at least 50% of the solid particles are less than 2 microns in diameter, more preferably at least 80% of the solid particles are less than 5 microns in diameter. Alternatively, more than 25% of the solid particles are less than 2 microns in diameter, more preferably more than 50% of the solid particles are less than 2 microns in diameter. In a preferred illustrative embodiment, the polymeric dispersant used is a polymer having a molecular weight of at least 2,000 Daltons. In another more preferred illustrative embodiment, the polymeric dispersant is a homopolymer or copolymer of monomers selected from the group consisting of acrylic acid, itaconic acid, maleic acid or anhydride, hydroxypropyl acrylate vinyl sulfonate Acid, acrylamido 2-propanesulfonic acid, acrylamide, styrenesulfonic acid, acrylate phosphate, methyl vinyl ether and vinyl acetate, among which the acid monomer can also be neutralized to form a salt.

The invention also relates to a lubricating composition comprising a base fluid and a polymer coated colloidal solid material. The polymer-coated colloidal solid material is formulated to comprise solid particles coated with a polymeric dispersant adsorbed on the surface of the colloidal solid particles.

These and other features of the invention are set forth more fully in the following description of preferred or illustrative embodiments of the invention.

Description of drawings

Reference is made to the accompanying drawing, which is a graphical representation of the particle size distribution of the colloidal barite of the present invention compared to API barite.

Detailed ways

A novel and novel aspect of the present invention resides in the dual role played by the colloidal particles in the drilling fluid. That is, the polymer-coated colloidal particles can act as both weighting agent and lubricant. This duality of the materials is novel to the drilling industry because weighting agents and lubricants have previously performed distinct functions.

Those skilled in the art will appreciate that the solid lubricants of interest above generally have lower densities than traditionally used weighting agents. For example, mineral-derived graphite has a specific gravity of about 2.09 to 2.25. In contrast, conventional weighting agents such as barite have a specific gravity of about 4.50 and hematite has a specific gravity of about 5.3. According to a preferred embodiment of the invention, the lubricating/weighting agent of the invention is formed from particles consisting of a material having a specific gravity of at least 2.68. In this way, the particles can function as a combination lubricant and weighting agent. The material forming colloidal solid particles with a specific gravity greater than 2.68 included in one aspect of the present invention includes one or more materials selected from but not limited to the following: barium sulfate (barite), calcium carbonate, dolomite, ilmenite , hematite or other iron ores, olivine, meteorite, strontium sulfate. Generally, the lowest viscosity of a wellbore fluid at any particular density is obtained using the highest density of colloidal particles. However, other considerations may influence product selection, such as cost, local availability, and energy required for grinding.

It will also be appreciated by those skilled in the art that conventional weighting agents such as crushed barium sulfate ("barite") have shown minimal effectiveness in reducing drill string torque. Physically, conventional weighting agents take advantage of their high density and exhibit an average particle size (d ₅₀ ) of 10 to 30 microns. It should be well known to those skilled in the art that the properties of traditional weighting agents, especially barite, depend on strict quality control parameters established by the American Petroleum Institute (API). To adequately suspend these materials, it is necessary to add gelling agents or viscosifiers such as bentonite to water-based fluids, or to add organically modified bentonites to oil-based fluids. Polymeric tackifiers such as xanthan gum are often added to reduce the settling velocity of traditional weighting agents. It was therefore very surprising that the product of the present invention comprising solid colloidal particles coated with a polymeric deflocculant or dispersant provides a fluid containing high density solids which also reduces the torque without increasing settling or sinking.

The additives of the present invention comprise dispersed solid colloidal particles coated with a polymeric deflocculant or dispersant. The tiny particle size will produce a suspension or slurry which will exhibit a reduced tendency to settle or sink, while the polymeric dispersant on the particle surface controls particle-particle interactions. It is the combination of small particle size and control over colloidal interactions that reconcile the two goals of high density and high lubricity.

According to the present invention, the polymeric dispersant is coated on the surface of the weighting particles during the process used to form the colloidal particles. It is believed that during the attrition process, newly exposed particle surfaces become coated with polymer, thereby giving rise to the properties exhibited by the colloidal solids of the present invention. Experimental data has shown that colloidal solid material produced in the absence of a polymeric dispersant results in a concentrated slurry of small particles, which is an unpumpable paste or gel. According to the teaching of the present invention, the polymeric dispersant is added during the milling process. It is believed that this difference provides a favorable improvement in the dispersion state of the particles compared to the case of post-addition of the polymeric dispersant to the fine particles. According to a preferred embodiment, the polymeric dispersant is selected to provide a suitable colloidal particle-particle interaction mechanism so as to make it resistant to common wellbore range contaminants, including salt saturated ones.

Methods of comminuting solid materials to obtain solid colloidal particles of the invention are known, for example from the specification of British Patent 1,472,701 or 1,599,632. The mineral in aqueous suspension is mixed with a polymeric dispersant and then milled in an agitated fluidized bed of particulate milling media for a time sufficient to provide the desired particle size distribution. An important preferred embodiment aspect of the invention is the presence of a polymeric dispersant during the "wet" grinding step of the mineral. This prevents new crystal surfaces formed during the grinding step from forming aggregates that would not be broken up as easily if these aggregates were later treated with a dispersant.

A preferred embodiment of the present invention is that the colloidal solid particles have a weight-average particle diameter (d ₅₀ ) of less than 10 microns. Another preferred illustrative embodiment is that at least 50% of the solid particles have a diameter of less than 2 microns, more preferably at least 80% of the solid particles have a diameter of less than 2 microns. Alternatively, in an illustrative embodiment, the particle size distribution is such that more than 25% of the solid particles are less than 2 microns in diameter, more preferably more than 50% of the solid particles are less than 2 microns in diameter. This will enhance the settling or sinking stability properties of the suspension without increasing the viscosity of the fluid to such an extent that it cannot be pumped.

The polymer-coated colloidal particles according to the invention can be provided as a concentrated slurry in an aqueous medium or an oily fluid. In the latter case, the oily fluid should have a dynamic viscosity of less than 10 centistokes (10 mm2/sec) at 40°C and, to be on the safe side, have a flash point above 60°C. Suitable oily fluids are, for example, diesel oil, mineral or white oil, n-paraffinic or synthetic oils such as alpha-olefin oils, ester oils or poly(alpha-olefins).

When the polymer-coated colloidal particles are provided in an aqueous medium, the dispersant can be, for example, a water-soluble polymer having a molecular weight of at least 2,000 Daltons. The polymer may be a homopolymer or copolymer of any monomer selected from (but not limited to) the following: acrylic acid, itaconic acid, maleic acid or anhydride, hydroxypropyl acrylate ethylene sulfonic acid, acrylamido 2-propane Sulfonic Acid, Acrylamide, Styrene Sulfonic Acid, Acrylic Phosphate, Methyl Vinyl Ether and Vinyl Acetate. Acid monomers can also be neutralized to form salts, such as sodium salts.

It has been found that moderate molecular weight polymers (eg, in the range of 10,000 to 200,000) can be used effectively when the dispersant is added during comminution (ie, grinding). Medium molecular weight dispersants have the advantage of being less sensitive to contaminants such as salts, clays and therefore well suited for wellbore fluids.

When the colloidal particles are provided in an oily medium, the dispersant can be selected from, for example, carboxylic acids having a molecular weight of at least 150 such as oleic acid, and polybasic fatty acids, alkylbenzenesulfonic acids, alkanesulfonic acids, linear alpha-olefinsulfonic acids Or alkaline earth metal salts of any of the above acids, phospholipids such as lecithin, synthetic polymers such as Hypermer OM-1 (trade name of ICI).

Although not meant to be bound by any particular theory of action, it is believed that the formation of colloidal solid materials by high-energy wet processes is more efficient when grinding is performed at high densities (typically greater than 2.1 sg, preferably 2.5 sg), where the median API barite with a particle size of 25-30 microns is reduced to a median particle size of less than 2 microns. At these high densities, the volume or mass fraction of barite is very high. For example, at a specific gravity of 2.5, 100 kg of final product contains approximately 78 kg of barite. However, the resulting slurry remained fluid. The presence of surface active polymers during the pulverization process is an important factor in achieving the results of the present invention. Furthermore, the surface active polymer is designed to adsorb onto the surface sites of the barite particles. In the attritor, when the mass fraction of barite is very high, the polymer readily finds its way onto the surface of the newly formed particles. Once the polymer "discovers" the barite - which has every opportunity to do so in the mill environment - the combination of a wet mill with an extremely high energy environment (which can reach 85-90 °C), this effectively ensures that the polymer "covers" around the colloidal-sized barite. As a result of this process, it is speculated that there are no polymer "loops" or "tails" for the barite to attach, block or wrap around adjacent particles. Therefore, it is speculated that the high energy and high shear forces of the milling process ensured that the polymer was permanently retained on the barite so that the polymer did not desorb or loosen.

This theory of action is supported by the observation that adding the same polymer to the same mass fraction of colloidal barite at room temperature and mixing with common laboratory equipment gives very different results. Under such conditions, it is believed that the polymer will not attach itself properly to the surface. This can be attributed to the presence of hydrates or other molecular spheres that occupy surface binding sites. Thus, the polymeric dispersant does not permanently "anneal" on the surface and, therefore, the rheology of the suspension is very high. It has also been observed that the suspension may not be as resistant to other contaminants as the polymer tends to detach itself from the barite and instead adsorbs to these more reactive sites.

The following examples serve to illustrate the properties and performance of the drilling fluids of the present invention, but the invention is not limited to the specific implementations shown in these examples. All tests are performed in accordance with applicable API RP13B. Mixing was done on a Silverson L2R or Hamilton Beach Mixer. Viscosities (RPM's) and other rheological properties at various shear rates were obtained using a Fann viscometer. Mud weight is checked using a standard mud scale or analytical balance. Fluid loss is measured using standard API fluid loss cells.

When expressing metric equivalents, use the following US to metric conversion factors: 1 gallon = 3.785 liters; 1 pound = 0.454 kilograms; 1 pound per gallon (ppg) = 0.1198 grams per cubic centimeter; 1 barrel = 42 gallons; Barrel (ppb) = 2.835 kg/m3; 1 lb/100 square feet = 0.4788 Pa.

These tests have been carried out using different grades of ground barite: standard grade API barite with a weight average particle size ( _D50 ) of approximately 20 microns; untreated barite (M) with an average size of 3 to 5 microns , prepared by grinding/grinding barite in dry state and in the absence of dispersant; and colloidal recrystallization according to the invention with polymeric dispersant added during "wet" grinding stone. Those skilled in the art will appreciate that other particulate materials may be used in the practice of the present invention.

A representative sample of the particle size distribution is shown in Figure 1. As shown in Figure 1, those skilled in the art will understand and appreciate that the particle size distribution of the colloidal barite particles of the present invention is very different from API barite. In particular, one should be able to determine that more than about 90% (volume percent) of the colloidal barites of the present invention have a particle size of less than about 5 microns. In contrast, in the API specification, less than 15% by volume of the particles have a particle size smaller than 5 microns.

The polymeric dispersant is IDSPERSE ^™ XT, an anionic acrylic terpolymer with a molecular weight in the range of 40,000-120,000, bearing carboxylate and other functional groups, commercially available from MI LLC, Houston, Texas The company gets. Advantages of this preferred polymer are that it is stable at temperatures up to 200°C, is resistant to a wide range of contaminants, provides good filtration properties, and does not readily desorb from particle surfaces.

The following examples illustrate the dual role of the lubricant as a weighting agent and as a lubricant (ie, torque reducer).

Example 1

A 22 ppg [2.63 g/cm3] fluid based on barium sulfate and water was prepared using standard barite and colloidal barite according to the invention. A 22 ppg slurry of API grade barite and water was prepared without the addition of gelling agent in order to control particle interactions (fluid #1). Fluid #2 was also based on standard API barite, but post added 2 lbs/barrel (5.7 kg/m3) IDSPERSEXT. Fluid #3 is 100% novel lubricant/weighting agent containing 67% w/w particles smaller than 1 micron in size and at least 90% smaller than 2 microns. The results are provided in Table I.

Table 1

# Viscosity at various shear rates (rpm of agitation): dial reading or "Fann units" plastic viscosity Yield point 600rpm 300rpm 200rpm 100rpm 6rpm 3rpm mPa.s 1b/100ft ² (Pa) 1 250 160 124 92 25 16 90 70(34) 2 265 105 64 26 1 1 160 -55(-26) 3 65 38 27 17 3 2 27 11(5)

For Fluid #1, the viscosity was very high and the slurry was observed to filter very rapidly. (If further material is added to reduce fluid loss, the viscosity will also increase further). The system visibly settled over 1 hour with a large amount of free water (calculated as 10% of initial volume).

Post-addition of 2 lb/barrel [5.7 kg/cm3] of IDSPERSE XT (Fluid #2) to conventional API barite reduced low shear rate viscosity by controlling interparticle interactions. However, due to particle concentration and average particle size, the fluid exhibits dilatency indicated by high plastic viscosity and negative yield point. This has a considerable effect on the pressure reduction of these fluids when pumped. That is, the ability to pump such fluids is greatly reduced due to the high viscosity. Fluid #2 settled immediately upon standing.

In contrast, Fluid #3 exhibited an excellent low plastic viscosity. The presence of the polymeric dispersant controls the interparticle interactions such that Fluid #3 is pumpable and not a gel. Also, the much lower average particle size stabilizes the flow pattern, which is now stratified at 1000s ^-1 , as evidenced by the low plastic viscosity and positive yield point.

Example 2

Experiments were performed to examine the effect of post-addition of selected polymeric dispersants to slurries containing weighting agents of the same colloidal particle size. Ground barite ( _D50-4 microns) and ground calcium carbonate (70 wt% particles smaller than 2 microns) were selected, both of similar particle size to the invention referred to herein. Slurries were prepared at equal particle volume fraction (0.282) and compared with the product of the invention (new barite). See Table II.

Rheology was measured at 120°F (49°C) and then 6ppb (17.2 kg/m3) of IDSPERSE XT was added. Finally the rheology of the resulting slurry was measured at 120[deg.]F with an additional API fluid loss test (see Table III).

Table 2

# Mineral Dispersant Density (ppg) volume fraction wt/wt 4 New type of barite Add at the same time as grinding 16.0[1.92g/cm ³ ] 0.282 0.625 5 Grinding barite do not join 16.0[1.92g/cm ³ ] 0.282 0.625 6 Grinding barite added later 16.0[1.92g/cm ³ ] 0.282 0.625 7 calcium carbonate do not join 12.4[1.48g/cm ³ ] 0.282 0.518 8 calcium carbonate added later 12.4[1.48g/cm ³ ] 0.282 0.518

table 3

# Viscosity at Various Shear Rates (rpm of Agitation): Dial Reading or "Fann Units" plastic viscosity Yield point API fluid loss 600rpm 300rpm 200rpm 100rpm 6rpm 3rpm mPa.s 1b/100ft ² 4 12 6 4 2 6 0 11 5 os os os os os os 6 12 6 4 2 6 0 all ¹ 7 os os 260 221 88 78 8 12 6 4 3 1 1 6 0 all ²

1 - Total fluid loss within 26 minutes 2 - Total fluid loss within 20 minutes

Post-addition of polymer did not bring about any filtration control as shown by total fluid loss in the API test.

Those skilled in the art will appreciate and know that the main valuable performance parameters are: low rheology including plastic viscosity (PV), yield point (YP), gel strength; minimal rheological change between initial and heat aged properties ; Minimal fluid loss and minimal sinking or settling. In the examples below, subsidence was quantified by separately measuring the density of the upper and lower halves of the aged fluid sample, and the dimensionless factor was calculated using the following equation:

Sinking factor = (upper half density)/(upper half density + lower half density)

A factor of 0.50 represents zero solids separation and no density change in all fluid samples. A sinkage factor greater than 0.52 is generally considered unacceptable solids separation.

Example 3

In the following example, two 13.0 ppg fluid formulations were compared, one weighted with conventional API barite and the other with polymer-coated colloidal barite prepared according to the teachings of the present invention ( PCC barite) was weighted as a 2.2 sg fluid slurry. The formulation contains other additives to provide additional control of: pH, fluid loss, rheology, inhibition of reactive shale and claystone. These additives are available from M-I Drilling Fluids.

product Fluid A Fluid B PCC barite lb/barrel API barite lb/barrel 320.0 238.1 Freshwater lb/barrel Soda Ash lb/barrel Celpol ESL lb/barrel Flotrol lb/barrel Defoamer NS lb/barrel KCl lb/barrel Glydril; MC lb/barrel Duotec NS lb/barrel 175.00.43.53.50.432.910.50.1 264.20.44.20036.110.51.4

The fluids were statically heat aged at 104°F for 48 hours and the following exemplary results were obtained.

FANN 35 reading (120) Fluid A Fluid B initial Ageing initial Ageing 600rpm300rpm200rpm100rpm6rpm3rpm 5636281954 6241332376 73524231119 65473929108 PV(cps)YP(pound/100 square feet) 2016 2120 2131 1829 10 Second Gels (lbs/100ft²) 10 Minute Gels (lbs/100ft²) 58 78 10 912 sinking factor 0.50 0.58

Reviewing the above results, one skilled in the art should appreciate that Fluid A formulated with polymer-coated colloidal barite had no solids separation, had a sink factor of zero, and had a rheological profile much lower than Fluids weighted with conventional API barite.

Example 4

In the following examples, a freshwater fluid at 14.0 ppg was chosen to compare the properties of fluids formulated with: polymer coated colloidal barite, uncoated colloidal barite, and traditional API barite. Fluid A was formulated with a polymer coated colloidal barite of the present invention. Fluid B was formulated with conventional API barite. Fluid C was formulated with commercial grade uncoated colloidal barite having a median particle size of 1.6 microns, available from Highwood Resources Ltd, Canada. A post-mill addition of the inventive coating polymer was also included in the formulations of Fluids B and C to keep the fluids in deflocculation conditions.

product Fluid A Fluid B Fluid C PCC barite lb/barrel API barite lb/barrel Sparwite W-5HB lb/barrel 407 300 310 Fresh Water lb/barrel Idsperse XTXCD Polymer lb/barrel DUAL-FLO lb/barrel Bentonite Clay lb/barrel 1820.5710 2766.00.6510 2746.20.5710

Samples of Fluids A, B and C were intentionally contaminated with bentonite to mimic the inclusion of natural drilling solids in the formulation. The samples were dynamically heat aged at 150°F for 16 hours. Exemplary and illustrative results after aging are shown below.

FANN 35 reading (100) Fluid A Fluid B Fluid C No bentonite With bentonite No bentonite With bentonite No bentonite With bentonite 600rpm300rpm200rpm100rpm6rpm3rpm 7448382786 7649392786 7851392786 205129100672019 9458452976 Out of scale Out of scale PV(cps)YP(pound/100 square feet) 2622 2722 2724 7653 3622 10 Second Gel (lb/100 sq ft) 10 Second Gel (lb/100 sq ft) 79 69 67 1720 67 API fluid loss (ml/30min) 3.5 3.0 4 3.9

Reviewing the above data, one skilled in the art will appreciate that the properties of Fluid A remain essentially the same, while Fluid B becomes very viscous, however, the rheology of Fluid C, formulated with uncoated colloidal barite, becomes too viscous after aging. So viscous that it cannot be measured.

Example 5

A further comparison was made between the polymer coated colloidal barite of the present invention and conventional API barite in a 14 ppg fluid where the yield point of the fluid had been adjusted to be equal for both fluids prior to aging.

product Fluid A Fluid B PCC barite (2.4sg) lb/barrel API barite lb/barrel 265 265 Freshwater lb/barrel Soda Ash lb/barrel KOH lb/barrel PolyPlus RD lb/barrel PolyPac ULDuovis lb/barrel KCl lb/barrel 2380.50.50.52.01.08.0 2930.50.50.52.00.758.0

The fluids were dynamically heat aged at 150°F for 16 hours. The table below shows exemplary results.

FANN 35 reading (120) Fluid A Fluid B initial Ageing initial Ageing 600rpm300rpm200rpm100rpm6rpm3rpm 6442322264 6139322154 8050332464 7243322164 PV(cps)YP(pound/100 square feet) 2220 2217 3020 2914 10 Second Gels (lbs/100ft²) 10 Minute Gels (lbs/100ft²) 517 511 56 56 API fluid loss (ml/30min) 2.8 4.7 VST ppg 0.21 1.33

Reviewing the foregoing, it will be appreciated by those skilled in the art that polymer-coated colloidal barites have a lower plastic viscosity and are therefore more desirable. The Viscometer Sink Test (VST) is another method of measuring sink in drilling fluids, which is described by D. Jefferson in American Society of Mechanical Engineers Magazine (1991). As shown above, Fluid A containing the polymer-coated colloidal barite of the present invention has a lower VST value than Fluid B formulated with untreated API barite.

Example 6

The long term thermal stability of the colloidal barite fluid of the present invention is shown in the example below at 17.34 ppg. ECF-614 additive is an organophilic clay additive available from M-I Drilling Fluids.

product Fluid A PCC barite (2.4sg) lb/barrel fresh water lb/barrel ECF-614 lb/barrel 68253.52.0

The fluids were statically heat aged at 350°F for 4 days. The table below provides exemplary results.

FANN 35 reading (120) Fluid A initial Ageing 600rpm300rpm6rpm3rpm 1076475 452832 PV(cps)YP(pound/100 square feet) 4321 1711 10 Second Gels (lbs/100ft²) 10 Minute Gels (lbs/100ft²) 610 411 sinking factor 0.503

Reviewing the above data, one skilled in the art will understand and appreciate the long-term thermal stability of the colloidal barite fluids of the present invention.

Example 7

This test was performed to show the feasibility of a 24 ppg [2.87 g/cm3] slurry (0.577 volume fraction). Each fluid contains the following components: fresh water 135.4 grams, barite 861.0 grams, IDSPERSE XT 18.0 grams. The barite components vary in composition according to the table below.

Table IV

# API grade barite (%) Colloidal barite (%) 9 100 0 10 90 10 11 80 20 12 75 25 13 60 40 14 0 100

Table V

# Viscosity at various shear rates (rpm of agitation): dial reading or "Fann units" plastic viscosity Yield point 600 300 200 117 100 59 30 6 3 mPa.s 1b/100ft ² (Pa) 9 ^* os 285 157 66 56 26 10 3 2 10 245 109 67 35 16 13 7 3 2 136 -27(-13) 11 171 78 50 28 twenty three 10 7 3 2 93 -15(-7) 12 115 55 36 19 17 8 5 3 2 60 -5(-2) 13 98 49 34 twenty one 20 14 10 4 3 49 0 14 165 84 58 37 32 twenty two 18 5 3 81 3(-1.5)

^* os = out of scale

The data presented in Table V shows that API grade barite exhibits dilatancy, ie high plasticity and pronounced viscosity with negative yield point due to its particle size and high volume fraction required to achieve high mud weight.

The addition of fine grade substances tends to stabilize the flow state and maintain its layered state at higher shear rates: the plastic viscosity is significantly reduced and the yield point changes from negative to positive. The low shear rate viscosity (@3rpm) does not significantly increase due to colloidal barite.

These results show that the colloidal barites of the present invention can be advantageously used in combination with conventional API barites.

Example 8

Eighteen (18) lbs/gal [2.15 g/cc] lubricant/weighting agent slurries according to the present invention were formulated, subsequently contaminated with a range of common contaminants, and hot rolled at 300°F (148.9°C). The rheological results before hot rolling (BHR) and after hot rolling (AHR) are shown below. The system showed excellent stain resistance, low controllable rheology, and gave fluid loss control under standard API mud tests as shown in Table VI below: prepared using API conventional barite without polymer coating, etc. valence fluid set, as a direct comparison of the two particle types. (Table VII)

Table VI (new barite)

Viscosity (Fann units) at various shear rates (rpm of stirring) PV YP fluid loss 600 300 200 100 6 3 mPa.s 1b/100ft ² (Pa) ml Pollutant-free BHR twenty one 11 8 4 1 1 10 1(0.5) Contaminant-free AHR 18 10 7 4 1 1 8 2(1) 5.0 +80ppb NaCl BHR 41 twenty three 16 10 2 1 18 5(2.5) +80ppb NaCl AHR 26 14 10 6 1 1 12 2(1) 16 +30ppb OCMA ¹ BHR 38 twenty two 15 9 2 1 16 6(3) +30ppb OCMA AHR 26 14 10 6 1 1 12 2(1) 6.8 +5ppb Lime BHR 15 7 5 3 1 1 8 -1(-0.5) +5ppb Lime AHR 10 5 4 2 1 1 5 0 6.4

¹ OCMA = Ocma clay, a fine-grained spherical clay commonly used to replicate drilling solids contamination, obtained from shale deposits during drilling.

Table VII (Traditional API Barite)

Viscosity (Fann units) at various shear rates (rpm of stirring) PV YP fluid loss 600 300 200 100 6 3 mPa.s 1b/100ft ² (Pa) ml Pollutant-free BHR twenty two 10 6 3 1 1 12 -2 Contaminant-free AHR 40 twenty four 19 11 5 4 16 8 all ¹ +80ppb NaCl BHR 27 13 10 6 2 1 14 -1 +80ppb NaCl AHR 25 16 9 8 1 1 9 7 all ¹ +30ppb OCMA BHR 69 55 49 43 31 26 14 31 +30ppb OCMA AHR 51 36 31 25 18 16 15 twenty one all ² +5ppb Lime BHR 26 14 10 6 2 1 12 2 +5ppb Lime AHR 26 14 10 6 1 1 12 2 all ¹

All fluid loss within 1-30 seconds

All fluid loss within 2-5 minutes

A comparison of the two sets of data shows that the lubricating/weighting agent (novel particle) according to the present invention has considerably better fluid loss control properties when compared to conventional API barite. API barite has also shown susceptibility to drilling solids contamination, however the newer particle systems are more tolerant.

Example 9

Experiments were conducted to demonstrate the capability of the new lubricating/weighting agent on drilling muds formulated with densities greater than 20 lbs/gal [2.39 g/cm3].

Prepare two 22 lb/gal [2.63 g/cc] mud systems with weighting agents consisting of 35% w/w new barite lubricant/weighting agent and 65% w/w API grade barite weighting agent (fluid #1) and 100% API grade barite (fluid #2), both containing 11.5 lb/gal [32.8 kg/m3] STAPLEX 500 (trademark Schlumbverger, shale stabilizer), 2 lb/gal [5.7 kg/m3] IDCAP (trade name Schlumbverger, Shale Inhibitor) and 3.5 lb/gal [10 kg/m3] potassium chloride. Other additives provided inhibition to the drilling fluid, but here the ability of the new formulation to accommodate any subsequently added polymers was demonstrated. Fluid hot rolling to 200°F (93.3°C). Results are provided in Table VIII.

Table VIII

Viscosity (Fann units) at various shear rates (rpm of stirring) PV Yield point fluid loss 600 300 200 100 6 3 mPa.s 1b/100ft ² (Pa) ml Before hot rolling (#1) 110 58 46 30 9 8 52 6(2.9) After hot rolling (#1) 123 70 52 30 9 8 53 17(8.1) 8.0 Before hot rolling (#2) 270 103 55 twenty three 3 2 167 -64(-32) After hot rolling (#2) os 177 110 47 7 5 12.0

os: out of scale

100% API grade barite has a very high plastic viscosity and is in fact disordered as demonstrated by the negative yield point. After hot rolling, the rheology was high off scale.

Example 10

This experiment demonstrates the ability of the novel lubricating/weighting agents of the present invention to reduce fluid viscosity. The lubricant/weighting agent is 100% colloidal barite according to the invention. Fluid #15 was based on synthetic oil (Ultidrill, a trademark of Schlumberger, a linear alpha-olefin with 14 to 16 carbon atoms). Fluid #16 was a water-based mud and included a viscosifier (0.5 ppb IDFLO, a Schlumberger trademark, a pure xanthan polymer) and a fluid loss control agent (6.6 ppb IDVIS, a Schlumberger trademark). Fluid #15 was hot rolled at 200°F (93.3°C) and Fluid #16 was heat rolled at 250°F (121.1°C). The results after hot rolling are shown in Table IX.

Table IX

Viscosities (Fann units) at various shear rates (rpm of stirring) PV gel ¹ Yield point 600 300 200 100 6 3 mPa.s 1bs/100ft ² (Pa) 1bs/100ft ² (Pa) #15: 3.6ppg [1.63g/cm ³ ] 39 27 twenty three 17 6 5 12 7/11 15 #16: 14ppg[1.67g/cm ³ ] 53 36 27 17 6 5 17 5/- 19

¹ A measure of the gelling and suspending properties of a fluid, measured at 10 seconds/10 minutes using a Fann viscometer.

Even though the formulation was not optimized, this experiment clearly shows that the novel lubricant/weighting agent provides a way to formulate brine-like fluids that can be used in slimhole applications and or coiled tubing drilling fluids. Rheological properties are improved by adding colloidal particles.

Example 11

Experiments were conducted to determine that the ability of the novel lubricating/weighting agent to formulate completion fluids is density controlled, and thus sediment stability is a major factor. The lubricating/weighting agent consisted of a novel colloidal barite according to the invention and 50 lb/barrel [142.65 kg/m3] standard API grade calcium carbonate, which acted as a bridging solid. Prepare fluid at 18.6 ppg [2.23 g/cm3] with 2 lb/barrel [5.7 kg/cm3] of PTS 200 (Schlumberger Trademark, pH buffer). Static aging tests were performed at 400°F (204.4°C) for 72 hours. The results are shown in the table below, showing good sedimentation stability and rheological properties before (BSA) and after (ASA) static aging.

Viscosity (Fann units) at various shear rates (rpm of stirring) PV YP free water* 600 300 200 100 6 3 mPa.s 1b/100ft ² (Pa) ml 18.6ppg BSA 37 twenty one 15 11 2 1 16 5(2.5) - 18.6ppg ASA 27 14 11 6 1 1 13 1(0.5) 6

^* Free water is the volume of clear water that appears on top of the fluid. The remaining fluid has a uniform density.

Example 12

This experiment demonstrates the ability of the new lubricant/weighting agent to formulate low density fluids and shows its resistance to pH changes. The lubricant/weighting agent consists of the novel colloidal barite according to the invention. The fluid was formulated with caustic soda at 16 ppg [1.91 g/cm3] to adjust the pH to the level required for fluid rheology and API filtration for subsequent experiments. The results shown in the table below show good resistance to pH changes and good rheological properties.

Viscosity (Fann units) at various shear rates (rDm of stirring) PV Yield point fluid loss pH 600 300 200 100 6 3 mPa.s 1bs/100ft ² (Pa) ml 8.01 14 7 5 3 7 0(0) 8.4 9.03 14 8 5 3 6 2(1) 8.5 10.04 17 9 6 3 8 1(0.5) 7.9 10.97 17 9 6 3 8 1(0.5) 7.9 12.04 19 10 7 4 1 1 9 1(0.5) 8.1

Example 13

This experiment demonstrates the ability of the new lubricant/weighting agent to formulate low rheology HTHP water-based fluids. The lubricating/weighting agent consisted of the novel colloidal barite according to the present invention and 10 lb/barrel [28.53 kg/m3] CALOTEMP (Schlumberger's trademark, fluid loss additive) and 1 lb/barrel [2.85 kg/m3] PTS 200 (Trademark of Schlumberger, pH buffer) composition. 17 ppg [2.04 g/cm3] and 18 ppg [2.16 g/cm3] static aged at 250°F (121°C) for 72 hours. The results shown in the table below show good sediment stability and low rheological properties in the filtration of subsequent experiments.

Density pH Viscosity (Fann units) at various shear rates (rpm of stirring) PV Yield point free water fluid loss ppg 600 300 200 100 6 3 mPa.s 1bs/100ft ² (Pa) ml ml 17 7.4 28 16 11 6 1 1 12 4(2) 10 3.1 18 7.5 42 twenty three 16 10 1 1 19 4(2) 6 3.4

Example 14

The following examples illustrate the ability of fluids formulated using the polymer-coated colloidal solid materials of the present invention to reduce drill string torque and thus act as lubricants.

Field experiment 1) A high-temperature and high-pressure well with a section of 311 mm was drilled to 5,121 meters at an inclination of 60 degrees using 1.8 kg/liter (15 lb/gallon) of invert oil (paraffin)-based drilling fluid. A polymer-coated colloidal solid of the present invention is added. The fluid was formulated as an 80:20 oil:water ratio drilling fluid with the following additional components added: Emul HT (27.0 lbs/barrel), Lime 8.1 lbs/barrel, EMI-783 (3.2 lbs/barrel), EMI -603 (3.5 lbs/barrel), VG Supreme (1.8 lbs/barrel). The fluid exhibits the following properties:

Fluid properties Fluid Weight (lbs/gallon) 14.58-15.08 Viscosity at 100rmp (lb/100ft²) 11-17 Viscosity at 3rmp (lb/100ft²) 2-3 Electrical Stability (Volts) 555-898 HTHP fluid loss (cubic centimeters/30 minutes) 2.0-3.4 LGS(lb/barrel) 10-70

The following observations were made on the fluid: the fluid system proved to be stable to a maximum downhole temperature of 166°C; there was no evidence of chip filling or mud weight changes during long-term static periods up to 82 hours; the plastic viscosity was initially 25 cps , with increasing mud weight and low-gravity solids, gradually increased to 41 cps at the end; the yield point remained constant throughout the work area, varying between 3 and 41 lbs/100 sq. ft. Amazingly, when compared to conventionally formulated fluids used in offset wells, the torque required to rotate the drill string assembly was reduced by 22% across overall intervals, and up to 25% in deviated well work areas. %.

Field experiment 2) use 1.6 kilograms per liter (13 pounds per gallon) oil base drilling fluid, offshore drilling large displacement 215.9 mm section in the North Sea oil reservoir, added the colloidal solid of polymer coating of the present invention in this drilling fluid and has the following recipe:

product fluid PCC barite lb/barrel fresh water barrel EDC99DW base oil barrel lime lb/barrel Versatrol lb/barrel bentonite 128 lb/barrel Emul HT lb/barrel 175.00.180.572.84.617.5

Fluids exhibit the following properties:

Viscosity (Fann units) at different shear rates (rpm of stirring) PV Yield point fluid loss 600 300 200 100 6 3 cps Lb/100ft ² (Pa) ml 62 36 26 16 4 3 26 10 2.1

The sections were drilled with mud weighing 13.2 lbs/gal and an oil:water ratio between 72:28 and 84:16. The water activity was varied between 0.89 and 0.82, and the electrical stability was controlled between 675 and 706 volts. Observations were: no subsidence or settling or changes in mud weight; picky (ie, finer screen) solids separation procedures could be used; no differential pressure sticking at 2,321 psi out of balance pressure in the lower part of the reservoir . The fluid system reduced torque in open boreholes by approximately 28% when compared to offshore drilling using conventional drilling fluids.

It will be understood and appreciated by those skilled in the art, considering the above data, that fluids comprising the polymeric dispersant-coated colloidal barite of the present invention reduce the amount of energy required to rotate the drill string when compared to conventionally formulated fluids. torque.

In view of the foregoing disclosure, those skilled in the art will understand and appreciate that an illustrative embodiment of the present invention includes a method of reducing drill string torque for drilling a subterranean well. In one such illustrative method, the method includes injecting into the drilling fluid a composition comprising a base fluid and a polymer-coated colloidal solid material. The polymer-coated colloidal solid material includes: solid particles with a weight-average particle diameter (d ₅₀ ) of less than 10 microns, and a polymer dispersant adsorbed on the surface of the solid particles during pulverization. The base fluid used in the above illustrative embodiments may be an aqueous fluid or an oily fluid, preferably selected from the group consisting of: water, brine, diesel oil, mineral oil, white oil, n-paraffin, synthetic oil, saturated and unsaturated poly(alpha -alkenes), esters of fatty acid carboxylic acids, and combinations and mixtures of these and similar fluids which will be apparent to those skilled in the art. Suitable and illustrative colloidal solids are selected such that the solid particles consist of a material having a specific gravity of at least 2.68, preferably selected from barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine, meteorite Iron, strontium sulfate, and combinations and mixtures of these materials with other suitable materials should be known to those skilled in the art. In a preferred and illustrative embodiment, the polymer-coated colloidal solid material has a weight average particle size (d ₅₀ ) of less than 2.0 microns. Another illustrative embodiment has at least 60% solid particles having a diameter of less than 2 microns, or alternatively more than 25% of the solid particles having a particle size of less than 2 microns. The polymeric dispersant used in one illustrative and preferred embodiment is a polymer having a molecular weight of at least 2,000 Daltons. In another preferred and illustrative embodiment, the polymeric dispersant is a water-soluble polymer, a homopolymer or copolymer of monomers selected from the group consisting of: acrylic acid, itaconic acid, maleic acid or anhydride, acrylic acid hydroxy Propyl vinyl sulfonic acid, acrylamido 2-propane sulfonic acid, acrylamide, styrene sulfonic acid, acrylate phosphate, methyl vinyl ether and vinyl acetate, where the acid monomers can also be neutralized to form a salt.

In addition to the above illustrative methods, the present invention also relates to a lubricating composition comprising a base fluid and a polymer-coated colloidal solid material. The polymer-coated colloidal solid material is formulated to include solid particles with a weight-average particle diameter (d ₅₀ ) of less than 10 microns, and a polymer dispersant coated on the surface of the solid particles. An illustrative embodiment includes a base fluid, which is an aqueous fluid or an oily fluid, and is preferably selected from the group consisting of water, brine, diesel oil, mineral oil, white oil, n-paraffins, synthetic oils, saturated and unsaturated poly(α-olefins) ), esters of fatty acid carboxylic acids, and combinations and mixtures of these and other similar fluids that should be apparent to those skilled in the art. In an illustrative embodiment, preferably the solid particles consist of a material having a specific gravity of at least 2.68, more preferably the colloidal solid is selected from the group consisting of barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine , meteoric iron, strontium sulfate, and combinations and mixtures of these and other similar solids that should be apparent to those skilled in the art. The polymer-coated colloidal solid material used in a preferred and illustrative embodiment has a weight average particle size (d ₅₀ ) of less than 2.0 microns. Another illustrative embodiment comprises at least 60% solid particles having a diameter of less than 2 microns, or alternatively more than 25% of the solid particles having a diameter of less than 2 microns. A polymeric dispersant is used in the preferred and illustrative embodiment and is selected such that the molecular weight of the polymer is preferably at least 2,000 Daltons. Alternatively, exemplary polymeric dispersants may be water-soluble dispersants that are homopolymers or copolymers of monomers selected from the group consisting of acrylic acid, itaconic acid, maleic acid or anhydride, hydroxypropyl acrylate vinyl sulfonate Acid, acrylamide 2-propanesulfonic acid, acrylamide, styrenesulfonic acid, acrylate phosphate, methyl vinyl ether and vinyl acetate, among which the acid monomer can also be neutralized to form a salt.

Those skilled in the art should understand and realize that the present invention further includes a method for preparing the above-mentioned polymer-coated colloidal solid particles. Such an illustrative method includes: milling the solid particulate material and the polymeric dispersant for a time sufficient to achieve a weight average particle size (d ₅₀ ) of less than 10 microns; thus, the polymeric dispersant adsorbs to the solid particle surface. Preferably the illustrative milling process is performed in the presence of a base fluid. The base fluid used in one illustrative embodiment is an aqueous fluid or an oily fluid, and is preferably selected from water, brine, diesel oil, mineral oil, white oil, n-paraffins, synthetic oils, saturated and unsaturated poly(alpha- alkenes), esters of fatty acid carboxylic acids, and combinations thereof. In an illustrative embodiment, the solid particulate material is selected from materials having a specific gravity of at least 2.68, more preferably the solid particulate material is selected from barium sulfate (barite), calcium carbonate, dolomite, ilmenite, hematite, olivine rocks, meteorites, strontium sulfate, and combinations and mixtures of these and other similar solids that should be apparent to those skilled in the art. The method of the invention involves milling the solid in the presence of a polymeric dispersant. Preferably the polymeric dispersant is a polymer having a molecular weight of at least 2,000 Daltons. The polymeric dispersant in a preferred and illustrative embodiment is a water soluble polymer that is a homopolymer or copolymer of monomers selected from the group consisting of: acrylic acid, itaconic acid, maleic acid or anhydride, hydroxypropyl acrylic acid Ester vinyl sulfonic acid, acrylamide 2-propane sulfonic acid, acrylamide, styrene sulfonic acid, acrylate phosphate, methyl vinyl ether and vinyl acetate, among which the acid monomer can also be neutralized to form a salt.

Those skilled in the art will appreciate that the products of the above illustrative methods are considered part of the present invention. Also, one such preferred embodiment includes the product of the above illustrative method, wherein the polymer-coated colloidal solid material has a weight average particle size ( _d50 ) of less than 2.0 microns. Another illustrative embodiment comprises at least 60% solid particles having a diameter of less than 2 microns, or alternatively more than 25% of the solid particles having a diameter of less than 2 microns.

While the devices, compositions and methods of the present invention have been described in terms of preferred or illustrative embodiments, it will be apparent to those skilled in the art that modifications and variations as described herein can be made without departing from the concept and scope of the invention. method is changed. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention as outlined in the following claims.

Claims (21)

1. lubricating composition, it comprises base fluids and polymer coated colloidal solid material, wherein said polymer coated colloidal solid material comprises: weight average particle diameter (d ₅₀) less than 10 microns multiple solid particulates; And be adsorbed on polymeric dispersant on the described solid particles surface.

2. composition according to claim 1, wherein said base fluids are aqueous fluids or oily fluid.

3. composition according to claim 1, wherein said base fluids are selected from water, salt solution, diesel oil, mineral oil, white oil, n-paraffin, synthetic oil, saturated and undersaturated poly-(alpha-olefin), the ester of fatty acid carboxylate and their combination.

4. composition according to claim 1, wherein said multiple solid particulate is selected from barium sulfate (barite), lime carbonate, rhombspar, ilmenite, rhombohedral iron ore, peridotites, meteoric iron, Strontium Sulphate and their combination.

5. composition according to claim 1, the weight average particle diameter (d of wherein said multiple solid particulate ₅₀) less than 10 microns.

6. composition according to claim 1, wherein more than the particle diameter of 25% described multiple solid particulate less than 2 microns.

7. composition according to claim 1, wherein said multiple solid particulate is made up of at least 2.68 material proportion.

8. composition according to claim 1, wherein said polymeric dispersant are that molecular weight is at least 2,000 daltonian water-soluble polymers.

9. lubricating composition, it comprises base fluids and polymer coated colloidal solid material, wherein said polymer coated colloidal solid material comprises: multiple solid particulate; And the polymeric dispersant that is adsorbed on described solid particles surface, the particle diameter that wherein is less than 10% described solid particulate is greater than 10 microns.

10. composition according to claim 9, wherein said base fluids are aqueous fluids or oily fluid.

11. composition according to claim 9, wherein said base fluids are selected from water, salt solution, diesel oil, mineral oil, white oil, n-paraffin, synthetic oil, saturated and undersaturated poly-(alpha-olefin), the ester of fatty acid carboxylate and their combination.

12. composition according to claim 9, wherein said multiple solid particulate is selected from barium sulfate (barite), lime carbonate, rhombspar, ilmenite, rhombohedral iron ore, peridotites, meteoric iron, Strontium Sulphate and their combination.

13. composition according to claim 9, the weight average particle diameter (d of wherein said multiple solid particulate ₅₀) less than 10 microns.

14. composition according to claim 9, wherein more than the particle diameter of 25% described multiple solid particulate less than 2 microns.

15. composition according to claim 9, wherein said multiple solid particulate is made up of at least 2.68 material proportion.

16. being molecular weight, composition according to claim 9, wherein said polymeric dispersant be at least 2,000 daltonian water-soluble polymers.

17. lubricating composition, it comprises base fluids and polymer coated colloidal solid material, wherein said polymer coated colloidal solid material comprises: multiple solid particulate and the polymeric dispersant that is adsorbed on described solid particles surface, and wherein the diameter of at least 90% described solid particulate is less than 10 microns; And wherein said polymeric dispersant is that molecular weight is at least 2,000 daltonian water-soluble polymers.

18. composition according to claim 17, wherein said multiple solid particulate is selected from barium sulfate (barite), lime carbonate, rhombspar, ilmenite, rhombohedral iron ore, peridotites, meteoric iron, Strontium Sulphate and their combination.

19. composition according to claim 17, wherein more than the particle diameter of 25% described multiple solid particulate less than 2 microns.

20. composition according to claim 17, wherein said multiple solid particulate is made up of at least 2.68 material proportion.

21. method that in the rotary drill column assembly, reduces moment of torsion, described method comprises: inject the composition that comprises base fluids and polymer coated colloidal solid material in drilling fluid, wherein said polymer coated colloidal solid material comprises: with the solid particulate that is adsorbed on the polymeric dispersant bag quilt on the solid particles surface.

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