AU715752B2 - Well drilling and servicing fluids and methods of reducing fluid loss and polymer concentration thereof - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Applicant(s): TEXAS UNITED CHEMICAL COMPANY, LLC Actual Inventor(s): James W Dobson;, Paul D Kayga and Jesse C Harrison Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 3128 Australia Title: WELL DRILLING AND SERVICING FLUIDS AND METHODS OF REDUCING FLUID LOSS AND POLYMER CONCENTRATION

THEREOF

The following statement is a full description of this invention, including the best method of performing it known to me/us:- WELL DRILLING AND SERVICING FLUIDS AND METHODS OF REDUCING FLUID LOSS AND POLYMER CONCENTRATION

THEREOF

Prior Art The use of fluids for conducting various operations in the boreholes of subterranean oil and gas wells which contact a producing formation are well known. Thus drill-in fluids are utilized when initially drilling into producing formations. Completion fluids are utilized when conducting various completion operations in the producing formations. Workover fluids are utilized when conducting workover operations of previously completed wells.

One of the most important functions of these fluids is to seal off the face of the wellbore so that the fluid is not lost to the formation. Ideally tiffs is accomplished by depositing a filter cake of the solids in the fluid over the surface of the borehole without any loss of solids to the formation. In other words, the solids in the fluid bridge over the formation pores rather than permanently plugging the pores. This is particularly critical in conducting horizontal drilling operations within the producing formations.

Many clay-free fluids have been proposed for contacting the producing zone of oil and o• gas wells. See lot example the following U.S. Patents: Jackson et al. 3,785,438; Alexander 3,872,018; Fischer et al. 3,882,029; Walker 3,956,141; Smithey 3,986,964; Jackson et al.

4,003,838; Mondshine 4,175,042; Mondshine 4,186,803; Mondshine 4,369,843; Mondshine 4,620,596; and Dobson, Jr. et al. 4,822,500.

These fluids generally contain polymeric viscosifiers such as certain polysaccharides or polysaccharide derivatives, polymeric fluid loss control additives such as lignosulfonates, polysaccharides or polysaccharide derivatives, and bridging solids. As disclosed in Dobson, Jr. et al. U.S. Patent No. 4,822,500, the polymeric viscosifier and the polymeric fluid loss control additive may synergistically interact to provide suspension and fluid loss control in such fluids.

After the wellbore fluid has completed its desired functions, it is desirable to remove the filter cake before placing the well on production. The filter cake contains the polymers and bridging solids present in the wellbore fluid as well as any other non-soluble solids present therein. One such method of removing the filter cake is disclosed in Mondshine et al.

U.S. Patent No. 5,238,065. This method comprises contacting the filter cake with an acidic brine fluid containing certain peroxides for a period of' time sulficient to decompose the polysaccharide polymers in the filter cake, and preferably thereafter contacting the filter cake with a fluid in which the bridging particles are soluble.

Summary of the Invention 10 The present approach provides a method of reducing the fluid loss of well drilling and servicing fluids which contain at least one polymeric viscosifier, at least one polymeric fluid loss control additive, and a water soluble bridging agent suspended in an aqueous liquid in which the bridging agent is not soluble, a method of reducing the concentration of polymer required to provide a desired degree of fluid loss control to such fluids, well 15 drilling and servicing fluids having decreased fluid loss and/or polymer concentration therein, and a water soluble bridging agent fbr well drilling and servicing fluids in which the concentration of particles less than about 10 [tm is greater than about 10% by weight. The invention includes incorporating in the fluid the particulate, water soluble, bridging agent in which the concentration of particles less than about 10 ltn is greater than about 10% by S 20 weight of the bridging agent, most preferably at least about 12%.

In accordance with the invention, there is provided a particulate water soluble salt bridging agent for well drilling and servicing fluids which has a particle size distribution such that at least about 10% by weight of the particles thereof are less than about 10 micrometers.

The bridging agent can have a particle size distribution wherein f1or about 5% to about 30% of the particles thereof are less than 5 tirn; from about 10% to about 50% of the particles thereof are less than about 10 jin; from about 15% to about 60% of the particles thereof are less than about 15 im; from about 25% to about 70% of the particles thereof are less than about 20 [tim; fi-om about 45% to about 80% of the particles thereof are less than about 30 [tnm from about 55% to about 90% of the particles thereof are less than about [tin; from about 60% to about 95% of the particles thereof are less than about 44 [rin; from about 65% to about 95% of the particles thereof are less than about 50 jin; and from about to about 100% of the particles are less than about 80 jtm.

10 Alternatively the bridging agent of can have a particle size distribution wherein from about 5% to about 25% of the particles thereof are less than about 5 im; fiom about 12% to about 45% of the particles thereof are less than about 10 .tin; firom about 20% to about of the particles thereof are less than about 15 Irmn; fiom about 30% to about 65% of the particles thereof are less than about 20 !tin; from about 50% to about 75% of the particles 15 thereof are less than about 30 [LM; firom about 60% to about 85% of the particles thereof are less than about 40 Itm; from about 65% to about 90% of the particles thereof are less than about 44 [tim; from about 70% to about 95% of the particles thereof are less than about tun; and from about 85% to about 100% of the particles are less than about 80 Vtm. The bridging agent can have the salt being sodium chloride.

In another aspect of the invention there is provided a method of reducing the fluid loss of well drilling and servicing fluids which contain at least one polymeric viscosifier, at least one polymeric fluid loss control additive, and a water soluble salt bridging agent suspended in ST 3 /V7a saturated salt solution in which the bridging agent is not soluble, which includes providing said bridging agent with a particle size distribution such that at least 10% of the particles thereof are less than about 10 micrometers.

The method can have the bridging agent with a particle size distribution wherein from about 5% to about 30% of the particles thereof are less than 5 run; from about 10% to about of the particles thereof are less than about 10 p~m; from about 15% to about 60% of the particles thereof are less than about 15 upn; fiom about 25% to about 70% of the particles thereof are less than about 20 pmn; from about 45% to about 80% of the particles thereof are less than about 30 inm; from about 55% to about 90% of the particles thereof are less than 10 about 40 rpn; from about 60% to about 95% of the particles thereof are less than about 44 n; from about 65% to about 95% of the particles thereof are less than about 50 pim; and from about 80% to about 100% of the particles are less than about 80 pm.

Alternatively the method can have the bridging agent with a particle size distribution from about 5% to about 25% of the particles thereof are less than about 5 pm; from about g 15 12% to about 45% of the particles thereof are less than about 10 pm; from about 20% to

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about 50% of the particles thereof are less than about 15 pmi; fiom about 30% to about of the particles thereof are less than about 20 rnm; from about 50% to about 75% of the particles thereof are less than about 30 prm; from about 60% to about 85% of the particles thereof are less than about 40 lipm; from about 65% to about 90% of the particles thereof are less than about 44 ptim; from about 70% to about 95% of the particles thereof are less than about 50 prm; and from about 85% to about 100% of the particles are less than about 80 pm.

The bridging agent can be sodium chloride and the polymeric viscosifier can be a xanthan 3a gum with the polymeric fluid loss control additive is a starch ether derivative.

The invention also provides a well drilling and servicing fluid which contains at least one polymeric viscosifier, at least one polymeric fluid loss control additive, and a water soluble particulate sized salt bridging agent suspended in an aqueous solution in which the bridging agent is not soluble, wherein the bridging agent has a particle size distribution such that at least about 10% of the particles thereof are less than about 10 micrometers. The bridging agent can have a particle size distribution wherein from about 5% to about 30% of the particles thereof are less than 5 tim; from about 10% to about 50% of the particles thereof are less than about 10 imn; from about 15% to about 60% of the particles thereof are 10 less than about 15 lrm; from about 25% to about 70% of the particles thereof are less than about 20 prm; from about 45% to about 80% of the particles thereof are less than about Hun; from about 55% to about 90% of the particles thereof are less than about 40 [tm; from about 60% to about 95% of the particles thereof are less than about 44 mn; from about to about 95% of the particles thereof are less than about 50 i.m; and from about 80% to S 15 about 100% of the particles are less than about 80 utn. In another form the bridging agent o has a particle size distribution wherein from about 5% to about 25% of the particles thereof are less than about 5 tm; from about 12% to about 45% of the particles thereof are less than about 10 Ltm; from about 20% to about 50% of the particles thereof are less than about im; from about 30% to about 65% of the particles thereof are less than about 20 um; from about 50% to about 75% of the particles thereof are less than about 30 p[m; from about to about 85% of the particles thereof are less than about 40 nm; from about 65%0 to about of the particles thereof are less than about 44 rim; from about 70% to about 95% of the particles thereof are less than about 50 [pm; and from about 85% to about 100% of the particles are less than about 80 Ilure.

Preferably the salt is sodium chloride, and the polymnelic viscosifier is a xanthan gumn and wherein the polymeric fluid loss control additive is a starch ether derivative.

TIhese and other objects of the invention will be obviouIs to one skilled in the art on reading this specification and the claim-s appended hereto.

While the invention is susceptible to5 various modifications and alternative forms, specific embodiments thereof will hereinaller be described in detail and shown by way of

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0 a *0 .0 0 0* 7 7I example. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the invention is to cover all modifications and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.

The compositions can comprise, consist essentially of, or consist of the stated materials. The method can comprise, consist essentially of, or consist of the stated steps with the stated materials.

Detailed Description of the Invention i ~We have now discovered that the fluid loss of certain polymer-containing, well drilling 10 and servicing fluids as set forth hereinafter can be decreased by incorporating therein a particulate, water soluble, ultra fine filtrate reducing agent having a particle size distribution such that at least 90% of the particles thereof are less than 10 micrometers and the average particle size is from about 3 to about 5 micrometers. Alternatively, we have discovered that for any desired degree of fluid loss control of certain polymer-containing well drilling and 15 servicing fluids, the polymer concentration can be decreased by incorporating in the fluids a ooooo particulate, water soluble, ultra fine filtrate reducing agent having a particle size distribution 5such that at least 90% of the particles thereof are less than 10 micrometers and the average particle size is from about 3 to about 5 micrometers.

Hereinafter the term "UFFRA" may be used herein and is intended to mean the particulate, water soluble, ultra fine filtrate reducing agent having a particle size less than micrometers equivalent spherical diameter and an average particle size from about 3 to about micrometers equivalent spherical diameter.

We have also discovered a further modification in that the fluid loss of certain polymer-containing, well drilling and servicing fluids as set forth hereinafter can be decreased by incorporating therein a particulate, water soluble, bridging agent in which the concentration of particles less than about 10 /am is greater than about 10% by weight of the bridging agent, most preferably at least about 12%. Alternatively, we have discovered that for any desired degree of fluid loss control of certain polymer- containing well drilling and servicing fluids, the polymer concentration can be decreased by incorporating in the fluids a particulate, water soluble, bridging agent in which the concentration of particles less than about 10 m is greater than about 10% by weight of the bridging agent, most preferably at least about 12%. Well drilling and servicing fluids having decreased fluid loss or polymer concentration therein are provided wherein the fluids contain abridging agent in which the concentration of particles less than about 10 Im is greater than about 10% by weight of the 10 bridging agent, preferably at least about 12% by weight.

Hereinafter the term "BAO/O10" may be used herein and is intended to mean the particulate, water soluble, bridging agent in which the concentration of particles less than about 10 VIm is greater than about 10% by weight of the bridging agent.

The well drilling and servicing fluids to which this invention pertains contain at least 15 one polymeric viscosifier or suspending agent, at least one polymeric fluid loss control additive, and a water soluble bridging agent suspended in an aqueous liquid in which the *"*bridging agent is not soluble. See for example U.S. patents 4,175,042 (Mondshine) and 4,822,500 (Dobson et each incorporated herein by reference.

The colloidal properties of polymers greatly affect the role of such polymers in well drilling and servicing fluids. They have a strong affinity for water. They develop highly swollen gels in low concentrations. Most polymers do not swell as much in salt water as they do in fresh water; however, they nevertheless provide slimy particles of such size as to resist the flow of water through a filter cake. These versatile polymers make practical the use of low-solids, non-dispersive well drilling and servicing fluids. The great diversity in composition and properties of the polymers used in well drilling and servicing fluids requires an examination of the factors involved in the selection of a polymer for a specific application.

Among the factors which affect performance are the effects of temperature, shear conditions, dissolved salts, pH, and stability to micro organisms. Other factors considered in choosing a polymer include ease of degradation, ease of handling and mixing, possible environmental and health effects, and the cost of the polymer.

Polymeric viscosifiers or suspending agents used in well drilling and servicing fluids include certain natural gums, synthetic gums (called biopolymers since they are produced by bacterial or fungal action on suitable substrates), polysaccharide derivatives, and synthetic 10 copolymers. Representative polymeric viscosifiers or suspending agents include xanthan S S gum; welan gum; gellan gum; guar gum; hydroxyalkyl guar gums such as hydroxypropyl guar, hydroxyethyl guar, carboxymethyl hydroxypropyl guar, dihydroxypropyl guar, and the like; cellulose ethers such as carboxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, and the like; polyacrylates; ethylene oxide polymers; and the like.

15 The preferred polymeric viscosifiers or suspending agents are xanthan gum, welan gum, gellan gum, hydroxyalkyl guar gum, high viscosity (high molecular weight) carboxymethyl cellulose, and mixtures thereof, most preferably xanthan gum.

Polymeric fluid loss control additives used in well drilling and servicing fluids include pregelatized starch, starch derivatives, cellulose derivatives, lignocellulose derivatives, and synthetic polymers. Representative starch derivatives include: hydroxyalkyl starches such as hydroxyethyl starch, hydroxypropyl starch, hydroxyethyl carboxymethyl starch, the slightly crosslinked derivatives thereof, and the like; carboxymethyl starch and the slightly crosslinked derivatives thereof, cationic starches such as the tertiary aminoalkyl ether derivatives of starch, the slightly crosslinked derivatives thereof, and the like. Representative cellulose derivatives include low molecular weight carboxymethyl cellulose, and the like.

Representative lignocellulose derivatives include the alkali metal and alkaline earthmetal salts of lignosulfonic acid and graft copolymers thereof. Representative synthetic polymers include partially hydrolyzed polyacrylamides, polyacrylates, and the like. The preferred polymeric fluid loss control additives are the starch ether derivatives such as hydroxyethyl starch, hydroxypropyl starch, dihydroxypropyl starch, carboxymethyl starch, and cationic starches, and carboxymethyl cellulose. Most preferably the polymeric fluid loss control additive is a starch ether derivative which has been slightly crosslinked, such as with epichlorohydrin, phosphorous oxychloride, soluble trimetaphosphates, linear dicarboxylic 10 acid arthydrides, methylenebisacrylamide, and other reagents containing two or more functional groups which are able to react with at least two hydroxyl groups. The preferred crosslinking reagent is epichlorohydrin. Generally the treatment level is from about 0.005% to 0.1% of the starch to give a low degree of crosslinking of about one crosslink per 200 to *e 1000 anhydroglucose units, In accordance with the teachings of co-pending U.S. patent 15 application Serial Number 08/512676 filed 08/08/95, the starch or starch derivative can be partially hydrolyzed to decrease the degree of polymerization thereof.

S9 The bridging agents useful in this invention are bridging agents known in the art which are modified to increase the concentration of particles therein which have a particle size less than about 10 pm. They are solid, particulate, water soluble salts the particles of which have been sized to have a particle size distribution sufficient to seal off the pores of the formations contacted by the well drilling and servicing fluid. The bridging agent must not be soluble in the liquid used to prepare the fluid. Representative water soluble salts include sodium chloride, potassium chloride, calcium chloride, sodium formate, potassium formate, sodium bromide, potassium bromide, calcium bromide, sodium acetate, potassium acetate, and the like. The preferred bridging agent is sodium chloride.

It is preferred that the liquid comprises a saturated solution of one or more water soluble salts, such as the chloride, bromide, formate or acetate salts of sodium, potassium, or calcium, most preferably sodium chloride, sodium bromide, or calcium chloride.

The UFFRA of this invention may be any solid, particulate, water soluble salt having the required particle size which is insoluble in the liquid used to prepare the well drilling and servicing fluid. It may for instance be a bridging agent which has been ground to the extremely ultra fine particle size required. The preferred UFFRA is sodium chloride.

10 The concentration of UFFRA must be sufficient to reduce the fluid loss of the well S" drilling and servicing fluid in which it is incorporated. Generally, a concentration of UFFRA from about 2.5 kg/m 3 to about 85 kg/m 3 will be used, preferably from about 5 kg/m 3 to about kg/m 3 The addition of the UFFRA to the well drilling and servicing fluid does not appreciably 15 effect the viscosity of the fluid at circulating shear rates; however, the low shear viscosity and hence the suspension properties of the fluid is generally increased. The polymeric filtrate reducing agents of the prior art are hydratable colloids and increase the viscosity of the fluid at all shear rates.

The BAIO/10 of this invention may be any solid, particulate, water soluble salt having the required particle size which is insoluble in the liquid used to prepare the well drilling and servicing fluid. It may for instance be a bridging agent which has been ground to the particle size required. Alternatively, a finely ground salt can be added to a salt having a low concentration of particles less than about 10 p.m in order to provide the bridging agent having at least about 10% of the particles thereof less than about 10 pm.

The bridging agent of this invention preferably has a particle size distribution such that: from about 5% to about 30% of the particles thereof are less than about 5 im; from about to about 50% of the particles thereof are less than about 10 lim; from about 15% to about 60% of the particles thereof are less than about 15 im; from about 25% to about of the particles thereof are less than about 20 im; from about 45% to about 80% of the particles thereof are less than about 30 im; from about 55% to about 90% of the particles thereof are less than about 40 lim; from about 60% to about 95% of the particles thereof are 'i I"i less than about 44 jm; from about 65% to about 95% of the particles thereof are less than about 50 jm; and from about 80% to about 100% of the particles are less than about 80 pm.

10 Most preferably, the BAIO/10 of this invention has a particle size distribution such that: from about 5% to about 25% of the particles thereof are less than about 5 jm; from about 12% to about 45% of the particles thereof are less than about 10pm; from about 20% to S.i about 50% of the particles thereof are less than about 15m; from about 30% to about of the particles thereof are less than about 20 pm; from about 50% to about 75% of the of th15 particles thereof are less than about 30 pm; from about 60% to about 85% of the particles thereof are less than about 40 *m from about 65% to about 90% of the particles thereof are less than about 44 im; from about 70% to about 95% of the particles thereof are less than about 50Lm; and from about 85% to about 100% of the particles are less than about 80 pm.

The concentration of BAIO/10 must be sufficient to bridge, seal off, and reduce the fluid loss of the well drilling and servicing fluid in which it is incorporated. Generally, a concentration of BAIO/10 from about 14 kg/m 3 to about 570 kg/m 3 will be used, preferably from about 28 kg/m 3 to about 428 kg/m 3 Well drilling and servicing fluids as described herein having a desired degree of filtration control can be formulated to contain less polymer by incorporating the UFFRA or in the fluids. This results in a fluid having a lower viscosity at circulating shear rates, and a lower cost. Polymer concentrations may be reduced by up to about 50% in specific fluid formulations. The reduction in polymer concentration also provides for more efficient filter cake removal from the sides of the borehole in hydrocarbon producing formations. Filter cakes containing less polymer are more easily decomposed when utilizing polymer degrading compositions, such as those disclosed in Mondshine et al. U.S. Patent No.

5,238,065. This results in: decreased clean-up time and hence lower cost to remove the filter 10 cake; and the use of lesser strength polymer decomposing compositions, and hence decreased corrosion rates and decreased corrosion inhibitor requirements. Higher density fluids, formulated with inert weighting solids, can be obtained due to the reduced viscosity provided .9 o by the decreased polymer concentrations.

,i These and other benefits and advantages of the invention will be obvious to one skilled in the art upon reading the foregoing description of the invention.

S: .In order to more completely describe the invention, the following non-limiting o examples are given. In these examples and this specification, the following abbreviations may be used: API American Petroleum Institute; PSS Particulate Sized Salt (NaC1); ECHXHPS epichlorohydrin crosslinked hydroxypropyl starch; UFS Ultra Fine Salt (NaC1); PSC particulate sodium chloride; S.G. specific gravity; bbl= 42 gallon barrel; lb/bbl pounds per barrel; hr hours; g gram; cc cubic centimeters; °F degrees Fahrenheit; lb/gal pounds per gallon; percent by weight; mm millimetres; jim micrometer (micron); kg/m 3 kilogram per cubic meter; Tr Trace; PV API plastic viscosity in centipoise; YP API yield point in pounds per 100 square feet; Gel minute gel strengths in pounds per 100 square feet; LSRV Brookfield low shear viscosity at 0.3 revolutions per minute, in centipoise; HTHF high temperature, high pressure; NC No Control.

The plastic viscosity, yield point, and gel strengths were obtained by the procedures set forth in API's Recommended Practice 13B-I. The LSRV was obtained for the fluids using a Brookfield Model LVTDV-I viscometer having a number 2 spindle at 0.3 revolutions per minute. The LSRV is indicative of the suspension properties of the fluid, the larger the LSRV, the better is the suspension of solids in the fluid. All high temperature, high pressure a (HTHP) filtration data were obtained by a modified API filtration test. Thus to an API high temperature filtration cell with removable end cages is added a screen having 44 micron openings. There is then added 67.5 grams of a sized sand to produce a 1.5 cm sand bed. The sized sand has a particle such that all of the sand passes through a screen having 177 micron openings and is retained on a screen having 125 micron openings. The fluid to be tested is poured along the inside edge of the filtration cell so as not to disturb the sand bed. The filtration test is then conducted for 30 minutes at the desired temperature of 250°F under a pressure differential of 17.59 kg/cm 2 (250 pounds per square inch) supplied by nitrogen.

The particle size of the sized salt bridging agents disclosed in tiffs specification and the claims were measured with Malvern Instruments, Inc. MASTERSIZER E particle size analyzer. The bridging agents were suspended in a saturated sodium chloride solution.

UFFRA Examples Brine A is a 10.0 lb/gal NaCI brine. Brine B is a 12.5 lb/gal NaBr brine. The particulate sized salt (NaCI) bridging agents used in the examples have the particle size distribution set forth in Table A. These were determined utilizing an ALPINE Micron Air Jet Sieve TM. The size of the sieve openings in micrometers (microns) for the various sieve mesh sizes set forth herein are as follows: 100 mesh 149 microns, 200 mesh 74 microns, 325 mesh 44 microns, 450 mesh 32 microns, and 635 mesh 20 microns. Thus a particle size designation of +100 mesh indicates that the particles are >149 microns (greater than 149 microns). A particle size designation of 100/200 mesh indicates that the particles are <149 microns (less than 149 microns) and >74 microns. A particle size of 200/325 mesh indicates that the particles are <74 microns and >44 microns. A particle size of 325/450 mesh indicates that the particles are <44 microns and >32 microns. A particle size of 450/635 mesh indicates that the particles are <32 microns and >20 microns. A particle size of -635 mesh indicates that the particles are <20 microns.

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10 The Ultra Fine Salt (NaC1) filtrate reducing additive of this invention has a size distribution such that about 90% of the particles are less than 10 micrometers equivalent spherical diameter and an average particle size from about 3 to about 5 micrometers equivalent spherical diameter. Specifically, the UFS has a size distribution such that about of the particles are less than 18 micrometers, about 91.7% of the particles are less than 10.5 micrometers, about 81% of the particles are less than 7.5 micrometers, about 62.7% of oa the particles are less than 5.0 micrometers, about 50% of the particles are less than 3.75 micrometers, about 31% of the particles are less than 2.2 micrometers, about 20.5% of the a.

particles are less than 1.5 micrometers, and about 10% of the particles are less than 0.93 micrometers, and the average particle size is 3.76 micrometers.

The particulate sodium chloride samples evaluated for comparison with the ultra fine sodium chloride of this invention have the following particle sizes. PSC #1 98.6% 37.8 m, 84.6% 25.5 m, 49.7% 17.1 m, 17.6% 11.5 m, 3.2% 7.8 m, and the average particle size is 17.2 micrometers. PSC #2 99.9% 83.3 m, 94.7% 56.1 m, 59.7% 37.8 m, 15.1% 25.5 m, 0.6% 17.1 m, and the average particle size is 35.1 micrometers.

Table A Particle Size Distribution Particulate By Weight Retained Sized Salt +100 100/200 200/325 325/450 450/635 -635 PSS #1 Tr Tr 2 4 25 69 PSS #2 1 9 17 12 23 38 PSS #3 0 1 7 10 23 59 PSS #4 2 9 19 12 22 36 Example I A series of well drilling and servicing fluids were prepared having the compositions set forth in Table 1. These were evaluated for API rheology, low shear viscosity, pH and HTHP filtration characteristics. The data obtained are given in Table 1.

Example II A series of well drilling and servicing fluids were prepared wherein the concentrations of the polysaccharides, particulate sized salt bridging particles, and the ultra fine salt of this invention were varied. These fluids were evaluated for their high temperature, high pressure aa*filtration characteristics using the procedure disclosed herein. The data obtained are given in Tables 2, 3, and 4.

The fluids which did not contain any ultra fine salt, as required by this invention, are prior art control fluids. Comparison of the data for the fluids of this invention with the data for the control fluids indicates the lower fluid losses for the fluids of this invention or the ""*lower polymer concentrations required in the fluids of this invention for equal fluid loss control.

Example III Well drilling and servicing fluids having the compositions set forth in Table 5 were prepared and evaluated for their high temperature, high pressure filtration characteristics using the procedure disclosed herein. The data obtained are given in Table Compositions containing the ultra fine sodium chloride filtrate reducing agent of this invention (UFS) can be compared with particulate sodium chloride having a larger particle size distribution (PSC #1 and PSC The data readily indicates that the ultra fine salt of this invention reduced the fluid loss while the salt samples having the larger particle size did not reduce the fluid loss or even increased it.

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a Fluid Composition Brine A, bbl Brine B, bbl Xanthan Gum, lb/bbl ECHXFIPS, lb/bbl MgO, lb/bbl PSS lb/bbl UFS, lb/bbl Density, lb/gal Rheology 600 rpm 300 rpm 200 rpm 100 rpm 6 rpm 3 rpm Pv 18 YP 24 10 sec./lO min. Gels

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30 min., cc Cake Thickness, 1/32" #1 0.96 0 1.25 3.75 0 28 0 10.3 53 37 31 24 10 9 11/14 34200 8.10 Trace 5.25 2 #2 0.96 0 1.25 3.75 0 22.4 5.6 10.3 56 39 33 25 11 9 16 21 11/14 37300 7.95 0 2.4 2 Table 1 #3 0.96 0 1.25 3.75 0 19.6 8.4 10.3 54 38 32 24 11 9 17 22 11/15 38700 8.0 0 2.5 2 0.94 0 1 3 0 46 0 10.5 44 31 25 18 8 6 16 22 8/10 16800 7.1 2.0 14.5 3 0.94 0 1 3 0 32.2 13.8 10.5 45 31 25 19 8 7 13 18 8/10 18400 7.2 1.6 3.4 1 0.94 0 1 3 0 27.6 18.4 10.5 44 31 25 19 8 7 14 17 8/10 18300 7.2 1.0 5.1 3 0.94 0 1 6 0 46 0 10.5 42 26 9 13 18 9/12 26500 7.9 3.6 2 #4 #5 #6 #7 Table 1 (cont'd) a a.

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pH HTHP Filtrate Spurt Loss, cc 30 min., cc Cake Thickness, 1/32" #8 0.75 0 0.25 8.75 0 190 0 12.0 118 73 56 35 6 4 45 28 5/5 3300 7.9 3.0 8.0 10 #9 0.75 0 0.25 8.75 0 180 10 12.0 117 73 56 35 7 5 44 29 5/6 5200 7.9 1.5 4.5 8 110 #11 #12 0.73 0.73 0.73 0 0 0 0.25 0.25 0.25 8.75 8.75 8.75 0 0 0 206 195.7 185.4 0 10.3 20.6 12.2 12.2 12.2 116 72 55 34 6 4 44 28 4/6 3600 7.75 2.3 5.9 10 120 74 57 36 6 4 46 28 4/6 5900 7.75 1.0 4.9 8 105 64 49 30 5 3 41 23 4/5 4500 7.75 3.3 5.5 8 #13 0 0.70 0.25 6.75 2 229 0 14.2 247 154 117 73 12 8 93 61 8/9 7100 8.5 2.9 4.0 8 #14 0 0.70 0.25 6.75 MgO, 2 217.5 11.5 14.2 262 164 125 78 13 8 98 66 8/10 7000 8.55 Tr 1.8 6 Table 1 (cont'd) Fluid Composition #15 #16 J17 #18 #19 Brine A, bbl 0 0 0 0 0 0 Brine B, bbl 0.70 0.65 0.65 0.65 0.65 0.65 Xanthan Gum, lb/bbl 0.25 0.25 0.25 0.25 0.25 0.25 ECHXHPS, lb/bbl 6.75 6.75 6.75 4.75 4.75 4.75 MgO, lb/bhl 2 2 2 2 2 2 PSS lb/bbl 206.1 270 256.5 270 256.5 243 UFS, lb/bbl 22.9 0 13.5 0 13.5 27 Density, lb/gal 14.2 14.5 14.5 14.5 14.5 14.5 Rheology 600rpm249 344 368 29 27 28 *300 rpm 154 220 230 177 168 172 200 rpm 117 166 174 132 126 129 100 rpm 74 104 110 80 78 79 6 rpm 12 14 18 12 12 12 3 rpm 8 11 12 8 8 8 PV 95 124 138 117 106 113 YP 59 96 92 60 62 59 10 sec,/l0min. Gels 8/10 12/14 12/14 8/9 8/11 8/10 LSV 7900 11100 10100 8800 10400 9500 pH 8.55 8.55 8.6 8.6 8.5 8.6 HTIP Filtrate Spurt Loss, cc Tr 1.8 0 2.0 1.5 30 mi., cc 1.4 3.8 0 9.5 6.5 7.8 Cake Thickness, 1/32" 6 9 7 16 14 Table 2 S. 4O

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954 555

B

Fluid Composition Brine A, bbl Xanthan Gum, lb/bbl ECHXIIPS, lb/bbl PSS lb/bbl TiES, lb/bbl Density, lb/gal HTHP Filtrate Spurt Loss, cc min., cc Fluid Composition Brine A, bbl Xanthan Gum, lb/bbl ECHXHPS, lb/bbl PSS lb/bbl TiES, lb/bbl Density, lb/gal HTHIP Filtrate Spurt Loss, cc min., cc #21 0.94 1.25 3.75 46 0 10.5 1.0 10.5 #27 0.94 1.25 3.75 46 0 10.5 1.75 16.0 #22 0.94 1.25 3.75 36.8 9.2 10.5 #23 0.94 0.94 1 1 3 3 46 36.8 0 9.2 10.5 10.5 1.0 1.0 18.0 9.0 0.94 1.25 2 46 0 10.5 2.25 17.25 0.94 1.25 2 36.8 9.2 10.5 12.0 1.25 4.75 #28 0.94 1.25 3.75 43.7 2.3 10.5 Tr 9.25 #24 #25 #26 #29 0.94 1.25 3.75 41.4 4.6 10.5 1.0 6.75 0.94 1.25 3.75 36.8 9.2 10.5 5.25 Table 3 Fluid Composition Brine A, bbl Xanthan Gum, lb/bbl ECLIXHPS, lb/bbl PS8 Ib/bbl UFS, lb/bbl Density, lb/gal HTHP Filtrate Spurt Loss, cc min., cc Cake Thickness, 1/32" #31 #32 #33 0.94 0.94 0.94 1.25 1.25 1 3.75 3.75 3 46 36.8 46 0 9.2 0 10.5 10.5 10.5 #34 #35 #36 0.94 1 3 36.8 9.2 10.5 1.0 8.5 1 0.94 1.25 2 46 0 10.5 5.5 21 2 0.94 1.25 2 36.8 9.2 10.5 7 4.25 18.0 3.25 22.5 3 a 9* S. S.

S S a *5OS S a *5 a *5*a a a a a. S S

S.

S

Go a Fluid Composition Brine A, bbl Xanthan Gum, lb/bbl ECHXHIPS, lb/bbl PSS lb/bbl IJFS, lb/bbl 20 Density, lb/gal HTHP Filtrate Spurt Loss, cc min., cc Cake Thickness, 1/32" #37 0.94 1.25 3.75 46 0 10.5 1.5 11.0 2 #38 0.94 1.25 3.75 36.8 9.2 10.5 2.0 4.5 1 Table 4 #39 0.94

I

3 46 0 10.5 1.5 18.5 1/40 #41 1/42 1#43 0.94 1 3 36.8 9.2 10.5 1.5 9.5 0.94 1.25 2 46 0 10.5 3.75 22.5 0.94 1.25 2 36.8 9.2 10.5 1.75 9.0 0.94 1.25 5.75 46 0 10.5 3 2 3 2 Table F-luid Composition: 0.94 bb] Brine A, 1.25 ECHXHiPS, indicated concentrations of PSS UFS, lb/bbl Xanthan Gum, 3.75 PSC and PSC #2.

lb/bbl Fluid No.

44 46 47 48 49 50 51 52 53 lb/bbl PSS #4 46 43.7 41.4 36.8 43.7 41.4 36.8 43.7 41.4 36.8 lb/bbl

UFS

0 2.3 4.6 9.2 0 0 0 0 0 0 lb/bbl PSC #1 0 0 0 0 2.3 4.6 9.2 0 0 0 lb/bbl PSC #2 0 0 0 0 0 0 0 2.3 4.6 9.2 HTHP Filtrate Spurt Loss cc Loss, cc 5 19.8 Tr 0 5.3 0 4.5 21.2 2 18.5 2 19.2 3.8 43.7 7.2 23.5 7.5 .9 9 9 .9

S.

.9 9 9 9* 9. 9 .5aa 9* .9 9 9* 9 9.

*0*999 Examples Example 1 A series of particulate, water soluble, sodium chloride bridging agents were prepared by mixing together a commercial sample of Watesal A bridging agent with an ultrafine salt (NaCI). The particle size distribution was determined, and the pertinent data are set forth in Table A-2 through A-8, and summarized in Table A- 1.

Well drilling and servicing fluids were prepared by mixing together 336 cc of a saturated sodium chloride brine 1.25 g ofxanthan gum, 3.75 g of ECHXHPS, and 46.0 g of the bridging agents set forth in Table A-1 to A-8. Thus the fluids contained 10 1.25 Ib/bbl (3.57 kg/m 3 xanthan gum, 3.75 Ib/bbl (10.7 kg/m 3 ECHXHPS, and 46 Ib/bbl (131.4 kg/m 3 bridging agent. These fluids were evaluated for API rheology, low shear rate viscosity, pH, and HTHP filtration characteristics. The concentration of bridging particles, less than 10 pm in equivalent spherical diameter, present in the fluids was calculated using the data in table A-1. The data obtained are set forth in Table A-9.

U.

15 The data indicate that fluids containing bridging agents which contain greater than about 10% by weight of particles having a particle size of less than about 10 pm exhibit significantly reduced fluid loss as compared to the prior art fluids containing the prior art bridging agent.

Table A- I Table No. A-2 A-3 A-4 A-5 A-6 A-7 A-8 UFS 0 5 10 20 30 40 100 Average Particle Size At The In-dic-ated Of All -Particles 10% 11.98 8.92 5.07 3.40 3.21 1.92 1.44 32.60 30.59 26.21 23.07 20.19 10.79 6.76 60.98 58.67 53.40 51.80 48.49 43.43 14.34 Approximate Percent Of Particles Less Than The Indicated Particle Size 2 [in 3.2 3.6 5.0 6.1 6.5 10.5 14.5 5 Vtm 4.8 6.1 9.9 14.0 15A1 26.2 35.1 l0 [im 8.0 11.3 16.9 24.8 29.1 47.6 73.1 Vtm 14.1 18.5 25.4 34.3 39.9 59.4 91.4 Vtm 23.1 27.9 36.0 44.0 49.6 66.9 97.1 :30 jim 44.3 48.7 57.9 62.7 67.4 78.5 99.5 40 jim 63.9 67.4 75.4 77.8 81.4 87.3 99.8 S544 gim 83.6 73.7 81.9 82.7 85.8 90.2 99.9 Vim 89.9 81.2 86.8 88.2 90.7 93.5 100 100 100 100 100 100 100 100 *9*4q*

B

S

*5 S. *5

B

S

S.

S

5*S* 5554 5.55 *4.

5* 5 5* S S

S

S.5

S

S. 1 2 2 3 4 5 6 Table A-2 Prior Art Sized Salt (NaCI) Bridging Agent Particle Size.Range. [Im of Particles Low igh in Size Rang~ 1.00 1.00 1.23 0.52 1.23 1.51 0.49 1.51 1.86 0.42 1.86 2.30 0.36 2.30 2.83 0.33 2.83 3.49 0.33 3.49 4.30 0.38 4.30 5.29 0.48 5.29 6.52 0.64 6.52 8.04 0.91 8.04 9.91 1.42 9.91 12.21 2.35 12.21 15.04 3.86 [5.04 18.54 5.99 8.54 22.84 8.71 2.84 28.15 11.59 .8.15 34.69 13.90 4.69 42.75 14.61 2.75 52.68 13.32 2.68 64.92 10.53 4.92 80.00 7.24 of Particles High Size 1.63 2.14 2.63 3.05 3.41 3.74 4.07 4.46 4.94 5.58 6.49 7.92 10.26 14.12 20.11 28.81 40.40 54.30 68.91 82.24 92.76 100.00 0 040900

C

Oq 0 00 eq eq so

C

C

S C C. q

C

Sq..

C.

q.

q C p. *0 eq eq qCSqqC C C eq..

C q 5 C. C

C.

C

Particle Size Range. [yi Low High 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5.29 6.52 6.52 8.04 8.04 9.91 9.91 12.2! 12.21 15.04 15.04 18.54 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 Table A-3 Sample A-3 of Particles in Size Range 0.62 0.62 0.55 0.49 0.46 0.49 0.60 0.81 1.12 1.55 2.15 3.05 4.41 6.31I 8.70 11.25 13.32 13.90 12,50 9.48 5.89 of Particles <.High Size 1.70 2.32 2.93 3.49 3.98 4.44 4.94 5.54 6.36 7.48 9.02 11.17 14.22 18.63 24.95 33.65 44.90 58.22 72.12 84.62 94.11 100.00 9@*9u* 9. 0 9* *6 S. 99 9 9 9.

9. 0 *9 9

SO

S. S *5 0*

S.

S

S S S.

S

Particle Size Range. uIm Low High 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5,29 6.52 6.52 8.04 8.04 9.91 9.91 12.21 12.21 15.04 15.04 18.54 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 Table A-4 Sample A-4 of Particles in Size Ranve 0.81 0.85 0.86 0.87 0.93 1.06 1.25 1.49 1.76 2.09 2.64 3.59 5.13 7.21 9.66 11.88 13.00 12.29 9.92 6.81 3.73 of Particles High Size 2.20 3.01 3.86 4.72 5.59 6.52 7.58 8.83 10.32 12.07 14.17 16.80 20.39 25.51 32.73 42.38 54.26 67.26 79.55 89.46 96.27 100.00 0 000...

S

00 0 @0

S.

0@ 00 00 S 0 0000 00 S. 0 0000

OSSS

00

SO..

S

005S 00 5@ 0

S

*0 00

S

00005.

S

0000 e OS S 0 S.o.S.

0 Particle Size Range, urn Low High 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5.29 6.52 6.52 8.04 8.04 9.91 9.91 12.21 12.21 15.04 15.04 18.54 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 TFable Sample of Particles in-Size Range 1.00 1.12 1.22 1.33 1.49 1.74 2.05 2.44 2.86 3.29 3.76 4.40 5.37 6.72 8.42 10.06 11.08 10.83 9.12 6.29 3.07 of Particles Hig~h Size 2.34 3.34 4.46 5.68 7.01 8.50 10.24 12.29 14.73 17.59 20.88 24.64 29.04 34.41 41.13 49.55 59.61 70.69 81.53 90.65 96.93 100.00 a. a a a. 9 Particle Size Range. jim Low Higdi 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5.29 6.52 15 6.52 8.04 8.04 9.91 9.91 12.21 12.21 15.04 15.04 18.54 20 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 Table A-6 Sample A-6 of Particles in Size Rang~e 1.25 1.32 1.38 1.49 1.78 2.28 2.95 3.71 4.37 4.83 5.22 5.84 6.88 8.18 9.50 10.27 9.98 8.19 5.23 1.81 of Particles High Size 2.42 3.53 4.78 6.10 7.48 8.97 10.75 13.03 15.98 19.69 24.06 28.89 34.11 39.95 46.83 55.01 64.51 74.79 84,77 92.95 98.19 100.00

S

S

S

S.

*SS.S

Particle Size Range, 4Lm Low High 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5.29 6.52 6.52 8.04 8.04 9.91 9.91 12.21 12.21 15.04 15.04 18.54 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 Table A-7 Sample A-7 of Particles in Size Range 1.74 2.08 2.38 2.62 2.90 3.36 4.09 5.06 6.06 6.76 6.84 6.39 5.80 5.50 5.59 6.05 6.48 6.42 5.41 3.60 1.45 of Particles High Size 3.42 5.15 7.24 9.62 12.24 15.14 18.50 22.59 27.65 33.72 40.47 47.31 53.70 59.50 65.00 70.59 76.64 83.12 89.54 94.95 98.55 100.00

S.

9* Particle Size-Range. tm Low High 1.00 1.00 1.23 1.23 1.51 1.51 1.86 1.86 2.30 10 2.30 2.83 2.83 3.49 3.49 4.30 4.30 5.29 5.29 6.52 15 6.52 8.04 8.04 9.91 9.91 12.21 12.21 15.04 15.04 18.54 20 18.54 22.84 22.84 28.15 28.15 34.69 34.69 42.75 42.75 52.68 52.68 64.92 64.92 80.00 Table A-8 Sample A-8 of Particles in--Size Range 2.56 2.82 2.91 2.91 3.17 4.06 5.71 8.01 10.47 12,25 12.48 10.89 7.96 4.80 2.25 0.82 0.30 0.21 0.10 0 0 of Particles High Size 5.32 7.88 10.71 13.62 16.53 19.71 23.77 29.47 37.48 47.95 60.20 72.68 83.56 91.53 96.32 98.57 99.38 99.68 99.89 100.00 100.00 100.00 SamnpleA Approx. of Salt Particles <1 0 [un in Fluid 8.0 Salt Particles <1 0 [tin in Fluid, lb/bbl 3.7 Rheology Pv 16 TFable A-9 2 A-3 A-4 A-5 A-6 A-7 A-8 11.3 16.9 24.8 29.1 47.6 73.1 5.2 7.8 11.4 13.4 21.9 33 6 C.

CCC.

C

C

9* .C C

C

YP

10 Gels, 10 sec/I 10 min

LSRV

pH ITILP Filtrate Spurt Loss, cc 15 10 min., cc 20 min., cc mit., cc 24 11/15 30,900 7.9 2.0 3.5 5.0 7.25 16 24 11/14 30,000 8.1 1.25 2.5 3.5 5.5 16 27 11/15 31,700 8.0 0 2.0 3.5 4.25 17 27 1 2/I16 37,500 8.0 0 2.0 3.0 3.5 17 26 11/15 35,500 7.9 0 2.0 3.0 3.25 18 16 28 28 12/16 11/15 38,600 35,800 7.9 0 NC 1.75 2.5 3.25 Example 2 Well drilling and servicing fluids were prepared as in Example 1 except that the amount of the ECHXHPS fluid loss control agent was reduced to 2.0 g 2 Ib/bbl, 5.7 kg/m). The fluids were evaluated as in Example 1. The data obtained are set forth in Table B.

Comparison of the data with the data for Sample/Fluid A-2 of Table A-9 indicates that the concentration of the polymer fluid loss control additive can be decreased significantly by increasing the concentration of the bridging agent particles which are less than 10 .mun in size.

Example 3 Evaporated salt (NaCI) was ground to give the particle size distribution set forth in Table C. This bridging agent contained 12.8% of the particles less than about tm. A well drilling and servicing fluid was prepared and evaluated as in Example 1.

The data obtained are set forth in Table C.

S

S

S. S S S 5* 5 9* 5S 9 Sample/Fluid Approx. of Salt Particles <1 0 jim in Fluid Salt Particles <I10 [UUr in Fluid, lb/bbl Rheology Pv

YP

10 Gels, 10 sec/l10 min

LSRV

P[H

IITHP Filtrate Spurt Loss, cc 15 10 min., cc 20 1-iii., cc min., cc A-2 8.0 Table B A-3 A-4 11.3 16.9 A-5 24.8 A-6 29.1 A-7 47.6 3.7 5.2 13 20 10/13 23,900 8.1 4.0 9.0 12.0 15.0 13 19 9/12 23,500 8.0 3.5 6.0 7.75 10.0 A-8 73. 1 7.8 12 22 1 0/13 33,900 8.0 1.5 2.5 3.5 4.0 11.4 13.4 21.9 33.6 14 22 1 0/1 3 31,300 7.9 0.5 2.0 3.0 3.5 14 18 9/13 25,900 8.0 Tr 2.0 2.5 3.0 15 21 1 0/13 29,600 7.9 0 2.75 13 21 10/14 25,400 8.1

NC

t.

Table C *5

S

S

S

50 5* -Bridging Agent Average Particle Size At The Indicated Of All Particles 14 Vim 33.06 jimn =87.95 prm Approximate Percett Of Particles Less Than The Indicated Particle Size 2 jn 2.3% pin 6.3% 15 10 trn 12.8% 1 5 [unm 2 1 1 Vu-m 29.5% jim 45.4% Vum 59.2% 44 i 64.0% jiin 70. 1% jimn= 87. 1% Fluid Approx. of Salt Particles <1 0 [ill In Fluid Salt Particles <I10 i Rheo lgy

PV

Gels, 10 sec/l10min

LSRV

PH

HTItP Filtrate SIMLA LOSS, CC 1 0 mini, CC 20 ii, cc 30 mini, cc 12.8 5.9 23 10/13 30,000 1.75 6.75 If one considers the particle size distribution of an admixture of the particulate sized salts and the ultrafine salt of the Examples, the particle sizes in the following table can be calculated.

a.

.a a a a a a. a a Sized S~ Sample None PSS 91 PS5 #2 P55 #3 alt

UFS

0 100 100 0 Fluid Table Compositions 5 62.7 10 20 32 44 74 149 of Particle-, Indicated Ur nO TE 100 0 A 100 0 A 100 69 59* #1 PS5 #1 #1 15 PSS 91 #1 P55 #2 P55 #2 #2 PSS 93 28 29 2 22,24,26,30 3,5 6 11,14,17,19 12, 15,20 32,34,3 6 38,40,42 3.1 4.5 6.3 >:9 12.5* 18* 18.8* 27* 25 >3 6* 70.6 72.1 75.2 78.3 81.4 39.2* 42.4* 48.8 67.2 94.3 94.6 95.2 95.8 96.4 60.1* 62.2*~ 66.4* 85.6 98 100* 73* 9Q* 92 99* 98.1 100* 98.2 100* 98.4 100* 98.6 100* 98.8 100* 71.5* 89.6 73.0* 90.1* 76.0* 91.2* 93.6 99.2* >:3.1 6.3 12.5~ 12.5* >4.5 18" 18"' 98.1 98.2 98.4 100 '407E Data underlined meet the particle size distribution of preferred bridging agent 2 below.

*Data meet the particle size distribution of preferred bridging agent 3 below.

of Particles the indicated upn 5 10 20 30 40 Bridging Agent 1 2 44 50 5-30 10-50 5-25 12-45 25-70 45-80 55-90 60-95 65-95 80-100 30-65 50-75 60-85 65-90 70-95 85-100

Claims (12)

1. 2. The bridging agent of Claim I having a particle size distribution wherein from about to about 30% of the particles thereof are less than 5 iun; from about 10% to about of the particles thereof are less than about 10 rm; from about 15% to about 60% of the particles thereof are less than about 15 pm; from about 25% to about 70% of the particles thereof are less than about 20 pm; fiom about 45% to about 80 of the particles thereof are 10 less than about 30 fpm; from about 55% to about 90% of the particles thereof are less than about 40 pim; from about 60% to about 95% of the particles thereof are less than about 44 S pmi; fiom about 65% to about 95% of the particles thereof are less than about 50 lim; and from about 80% to about 100% of the particles are less than about 80 pm.
2. 3. The bridging agent of Claim 1 wherein said bridging agent has a particle size 15 distribution wherein fiom about 5% to about 25% of the particles thereof are less than about 5 p m; fiom about 12% to about 45% of the particles thereof are less than about 10 pim; from "about 20% to about 50% of the particles thereof are less than about 15 tm; from about to about 65% of the particles thereof are less than about 20 tnm; from about 50% to about 75% of the particles thereof are less than about 30 Itm; from about 60% to about 85% of the particles thereof are less than about 40 upm; from about 65% to about 90% of the particles thereof are less than about 44 rmn; from about 70% to about 95% of the particles thereof are less than about 50 pm; and from about 85% to about 100% of the particles are less than 34 about 80 urn.
3. 4. The bridging agent of Claim 1, 2, or 3 wherein the salt is sodium chloride. A method of reducing the fluid loss of well drilling and servicing fluids which contain at least one polymeric viscosifier, at least one polymeric fluid loss control additive, and a water soluble salt bridging agent suspended in a saturated salt solution in which the bridging agent is not soluble, which includes providing said bridging agent with a particle size distribution such that at least 10% of the particles thereof are less than about 10 micrometers.
4. 6. The method of Claim 5 wherein said bridging agent has a particle size distribution wherein from about 5% to about 30% of the particles thereof are less than 5 pmi; from about 0 10 10% to about 50% of the particles thereof are less than about 10 [Im; from about 15% to about 60% of the particles thereof are less than about 15 pIl; from about 25% to about S of the particles thereof are less than about 20 pin; from about 45% to about 80% of the particles thereof are less than about 30 tiun; from about 55% to about 90% of the particles thereof are less than about 40 linm; from about 60% to about 95% of the particles thereof are c.0 15 less than about 44 ltm; from about 65% to about 95% of the particles thereof are less than Sabout 50 p.n; and from about 8 0% to about 100% of the particles are less than about 80 rtm.
5. 7. The method of Claim 5 wherein said bridging agent has a particle size distribution from about 5% to about 25% of the particles thereof are less than about 5 fim; from about 12% to o* o about 45% of the particles thereof are less than about 10 ljm; from about 20% to about of the particles thereof are less than about 15 rpm; from about 30% to about 65% of the particles thereof are less than about 20 [tin; from about 50% to about 75% of the particles thereof are less than about 30 -un; from about 60% to about 85% of the particles thereof are less than about 40 pim; from about 65% to about 90% of the particles thereof are less than about 44 pim; from about 70% to about 95% of the particles thereof are less than about rim; and from about 85% to about 100% of the particles are less than about 80 tm.
6. 8. The method of Claim 5, 6, or 7 wherein said bridging agent is sodium chloride.
7. 9. The method of Claim 5, 6, or 7 wherein the polymeric viscosifier is a xanthan gum and wherein the polymeric fluid loss control additive is a starch ether derivative. A well drilling and servicing fluid which contains at least one polymeric viscosifier, at least one polymeric fluid loss control additive, and a water soluble particulate sized salt bridging agent suspended in an aqueous solution in which the bridging agent is not soluble, 0 10 wherein the bridging agent has a particle size distribution such that at least about 10% of the particles thereof are less than about 10 micrometers. I1. The well drilling and servicing fluid of Claim 10 wherein said bridging agent has a particle size distribution wherein fiomn about 5% to about 30% of the particles thereof are less than 5 tinm; from about 10% to about 50% of the particles thereof are less than about 15 inm; from about 15% to about 60% of the particles thereof are less than about 15 ltm; from 0 about 25% to about 70% of the particles thereof are less than about 20 uin; from about to about 80% of the particles thereof are less than about 30 itm; from about 55% to about O 90% of the particles thereof are less than about 40 ipm; from about 60% to about 95% of the particles thereof are less than about 44 onm; from about 65% to about 95% of the particles thereof are less than about 50 p.m; and fiom about 80% to about 100% of the particles are less than about 80 [um.
8. 12. The well drilling and servicing fluid of Claim 10 wherein said bridging agent has a article size distribution wherein from about 5% to about 2 5% of the particles thereof are 13 36 less than about 5 urn; from about 12% to about 45% of the particles thereof are less than about 10 iiun; irom about 20% to about 5 0 of the particles thereof are less than about umn; from about 30% to about 65% of the particles thereof are less than about 20 unm; from about 50% to about 75% of the particles thereof are less than about 30 lrm; from about to about 85% of the particles thereof are less than about 40 run; from about 65% to about 90% of the particles thereof are less than about 44 i.un; from about 70% to about 95% of the particles thereof are less than about 50 rm; and liom about 85% to about 100% of the particles are less than about 80 lure.
9. 13. The well drilling and servicing fluid of Claim 10, 1I, or 12 wherein the salt is sodium chloride.
10. 14. The well drilling and servicing fluid of Claim 10, 11, or 12 wherein the polymeric viscosifier is a xanthan gum and wherein the polymeric fluid loss control additive is a starch oo 0 ether derivative.
11. 15. A particulate water soluble bridging agent substantially as hereinbefore described with 5 reference to the examples on page 33 of the description.
12. 16. A method of reducing the fluid loss of well drilling and servicing fluids substantially as So" hereinbefore described with reference to the examples. Dated this 27th day of October 1999 PATENT ATTORNEY SERVICES Attorneys for TEXAS UNITED CHEMICAL COMPANY, LLC