MXPA99007467A - Aphron-containing well drilling and servicing fluids - Google Patents

Abstract

The invention provides a method and fluid for drilling or servicing a well in a subterranean formation containing lost circulation zones or depleted, low pressure reservoirs. The fluid comprises an aqueous liquid having dispersed therein a polymer which increases the low shear rate viscosity of the fluid to the extent that the thixotropic index of the fluid is at least about 10 and a surfactant, and wherein the fluid contains less than about 15%by volume of aphrons preferably generated by the turbulence and pressure drop as the fluid exits the drill bit in the vicinity of the formation. The method of drilling a wellbore in a subterranean formation comprises continuously circulating, while drilling, such a drilling fluid.

Description

FLUIDS OF DRILLING AND REPAIR OF WELLS CONTAINING APHRON Background of the Invention The formation of damage due to the invasion of drilling fluids is a well-known problem. Many areas contain the formation of clays that hydrate when put in contact with water as the filtered liquid from drilling fluids. Hydrated clays tend to block production areas, mainly sands, so oil and gas can not be moved to the drilling and be produced. The solids also damage such areas, which are transported to the openings with the fluid. The movement of drilling fluids and filtering through such openings also causes the discharge and migration of solids at the formation site. Such solids can deposit and block the movement of the hydrocarbons produced. The invasion is due to the differential pressure of the hydrostatic column, which is generally greater than the pressure of the formation, especially in areas of low pressure or depleted areas. The invasion is also due to the openings in the rock and the ability of the fluids to move REF .: 29542 through the rock, the porosity and the permeability of the area. Due to such differential pressure, drillers have long used filtering control mechanisms to 'control the movement of fluids and drilling filtrate in and through the forming openings. This mechanism involves the addition of particles to the drilling fluid, such particles then being deposited on the perforation wall when drilling and drilling. Such particles are generally a combination of bentonite, starch, lignins, polymers, barium sulfide and perforation solids. The above materials are used to seal and seal the perforation due to the size and shape of the particle, and part of the control is also due to the viscosity of the filtrate when the water-soluble polymers are used. Although the wall cake forms a semipermeable barrier, some of the filtrate moves through and into the zone before and after the wall cake is formed. Therefore, the control of the wall cake is not complete and a part of the filtered water can be put in contact with the production zone. Another drawback of the mud of the wall cake is that when the filtrate moves, the solids are sieved and left in the cake or bark.

The above causes the cake to become thicker and may lead to a differential fixation of the sounding column. The latest technology has seen the development of fluids with low shear velocity viscosity (LSRV). The LSRV is created by the addition in water of specialized polymers or brine to form a drilling fluid. Such polymers have the unique ability to create an extremely high viscosity at low shear rates. Such LSRV fluids have been widely used due to their transportation capacity and their solids suspension capacity. These have been accepted as a way to minimize cuttings from bedding in high-angle and horizontal wells, and as a way to reduce the release of barium sulphide in high-weight muds. Recent studies and field experience indicate that such LSRV is useful in controlling the invasion of drilling fluids and filtering by creating a high resistance to movement in the formation openings. Since the fluid moves at a very slow speed, the viscosity becomes very high, and the drilling fluid is contained within the perforation with very little penetration. This has been beneficial for the protection of areas against damage, as well as in the reduction of differential fixation in such fluids. See for example the article entitled "Drill-in Fluids Improve High Angle Well Production", supplement of the Petroleum Engineer International, March 1995. The loss of circulation is also a serious problem in rotary drilling. The loss of circulation occurs when the differential pressure of the hydrostatic column is much higher than the formation pressure. The openings in the rock can accept and store the drilling fluid so that nothing returns to the surface to recirculate. The fluid is lost inside the perforation and can be a serious and dangerous problem. The loss of circulation can lead to drilling instability, perforation tube malfunction and loss of well control. At least, it stops drilling operations and requires expensive replacement of the volume to be used. In addition to the volume of fluid that is lost, expensive lost circulation materials (LCM) are required. These are generally fibrous, granulated or fritted materials, such as fibers, wood fibers, cottonseed husks, walnut shells, mica, cellophane and various other materials. Such LCM materials are added to the fluid system so that they can be transported to the loss and charge zone to form a bridge in which other materials can begin to build and seal. Such LCM materials are harmful to the zones, and because they must be transported several times in the drilling fluid to maintain circulation, the removal of the solids is stopped, resulting in a highly solid mud. Methods for correcting the loss of circulation of the drilling fluids to oxygenate the drilling fluids are described in U.S. Patents 2,818,230 (Davis) and 4,155,410 (Jackson). The use of the unbalanced perforation that has increased the development of low pressure formations has become more important. Horizontal drilling, in particular, has increased the need to drill in areas that are not only low pressure, but highly fractured or permeable. Exposure to numerous fractures or openings that have low formation pressures has increased the problem of circulation loss and invasion formation. The need for drilling tools several times prevents the use of bridging materials to stop such losses. This has led to the use of unbalanced drilling techniques to control losses and invasion of such areas. Some of such techniques include the use of air drilling fluids, water spray and foam. Problems with such fluids include the cleaning of the orifice, the control of fluid formation, corrosion, and the requirements of expensive and difficult-to-achieve equipment, such as compressors and thrusters. Such fluids can not be put back into circulation and must be generated constantly as the drilling proceeds.

BRIEF DESCRIPTION OF THE INVENTION A new fluid technique combines the use of polymers that generate a viscosity of low cutting speed with surfactants to form the "aphrons" of colloidal gas at a concentration of less than about 15% by volume in a perforation of recirculable well and repair fluid. The aphrons use encapsulated air available in most circulating fluids. The aprons reduce the density of the fluid and provide means of bridging and sealing the formations contacted by the fluid as the bubbles expand to fill openings exposed during drilling. The low shear rate polymers strengthen the microbubble and also provide resistance to movement within the formation, so that fluid losses are substantially reduced as the formation is drilled. In this way the loss of circulation is prevented. Any fluid entering the formation is clean and essentially free of solids, so that formation damage is significantly less than with fluids containing solids. Since no solid or particles are involved in this method, solids removal equipment can be used to keep the fluid as clean as possible. It is an object of the present invention to provide a perforation of recirculating wells and repair fluids having a viscosity of reduced improved cutting speed (hereinafter abbreviated as "ELSRV") containing aphrons. It is another object of the present invention to provide a method of bridging and sealing underground formations on the surface of the hole during well drilling and repair operations. These and other objects of the invention will be apparent to one skilled in the art upon reading the present specification and the claims. The method may comprise, consist essentially of, or consist of the steps mentioned with such materials. The compositions may comprise, consist essentially of, or consist of the materials mentioned.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The well drilling and repair fluids of the present invention may comprise an aqueous liquid having a water-soluble polymer hydrated therein and a surfactant. The polymers useful in the ELSRV fluids of the present invention are such that the ELSRV fluids have a "thixotropic index" of at least 10, wherein the thixotropic index is the ratio of the Brookfield viscosity of 0.5 rpm to the Brookfield viscosity of 100 rpm. . The thixotropic index is an indicator of the thinning characteristics of the fluid cut. The aqueous base fluid in which the low speed cutting modifying polymer is hydrated can be any aqueous liquid that is compatible with the polymer. In this way, the base liquid can be potable water, or soluble salts containing brine, such as sodium chloride, potassium chloride, calcium chloride, sodium bromide, potassium bromide, calcium bromide, zinc bromide, sodium formate, potassium formate, cesium formate and the like. The brine may contain one or more soluble salts at any desired concentration until saturation. The polymers useful in the ELSRV fluids of this invention comprise any water-soluble polymer that increases the viscosity of low fluid cutting speed to produce a fluid that exhibits a high yield stress and shear thinning behavior. Biopolymers produced by the action of bacteria, fungi or other microorganisms on a suitable substrate are particularly useful. Exemplary biopolymers are polysaccharides produced by the action of the bacterium Xanthomonas compestris, which is known as xanthan gum. It is commercially available from several sources including: Kelco Oil Field Group, Inc., under the trade names "Xanvix" and "Kelzan"; Rhone-Poulenc Chimie Fine, under the trade name "Rhodopol 23-p"; Pfizer Inc; under the trade name "Flocon 4800C"; Shell International Chemical Company of London, U.K, under the trade name "Shellflo ZA"; and Drilling Specialties Company; under the cocial name "Flo zan". See, for example, U.S. Patent No. 4,299,825 and U.S. Patent No. 4,758,356, each incorporated herein by reference. Other biopolymers useful in the fluids of the present invention are the so-called elastones, produced by fermentation with a microorganism of the Alcaligo genus. See, for example, U.S. Patent No. 4,342,866, incorporated herein by reference. Gellan gums are described in U.S. Patent No. 4,503,084, incorporated herein by reference. Scleroglucan polysaccharides produced by fungi of the sclerotium genus are described in U.S. Patent No. 3,301,848, incorporated herein by reference. The cocially available scleroglucan is sold under the trade names "Polytran" of the Pillsbury Company and "Actigum CS-11" of CECA S.A. The succinoglycan polysaccharides are produced by the cultivation of a Pseudomonas, Rizobio, Alcalígenos or Agrobacterium sludge species, that is, Pseudomonas sp. NCIB 11264, Pseudomonas sp. NCIB 11592 or Agrobacterium radiobacter NCIB 11883, or mutants thereof, as described in European Patent No. A40445 or A138255. The "cocially available succinoglycan biopolymer is sold by the Shell International Chemical Company of London UK, under the tradename" Shellflo-S. "The minimum polymer concentration required to increase the viscosity of the low fluid cutting speed can be determined by Routine tests In this way, the minimum concentration will be an amount sufficient to impart the viscosity of low desired cutting speed to the fluid, generally the fluids will contain a form of concentration of approximately 0.7 kg / m3 (0.25 ppb) to approximately 11.4 kg / m3 (4 ppb), preferably from about 1.4 kg / m3 (0.5 ppb) to about 7.1 kg / m3 (2.5 ppb) The water-based drilling fluids of this invention can generally contain well-known materials in the technique to provide various characteristics or properties to the fluid, in this way, fluids may contain one or more viscosifiers or agents uspensión in addition to the required polisácarido, agents of load, corrosion inhibitors, soluble salts, biocidas, fungicidas, additives of control of loss of filtration, agents of bridging, desfloculantes, additives of lubricity, additives of control of clay and other additives as wished . The drilling fluids may contain one or more materials that function as encapsulation or fluid loss control additives to further restrict fluid ingress to the contacted clay. Representative materials known in the art include partially solubilized starch, gelatinized starch, starch derivatives, cellulose derivatives, acid smoke salts (lignite salts), lignosulfonates, gums, water soluble synthetic polymers and mixtures thereof. The fluids of the present invention should have a pH in the range of about 7.0 to about 11, preferably from 8 to about 10.5. The pH can be obtained as is well known in the art, by the addition of the bases to the fluid, such as potassium hydroxide, potassium carbonate, potassium humate, sodium hydroxide, sodium carbonate, sodium humate, oxide of magnesium, calcium hydroxide, zinc oxide and mixtures thereof. The preferred base is magnesium oxide. The surfactants useful in the present invention for creating aphrons must be compatible with the polymers present in the fluid to create the desired low cutting speed viscosity. Thus, surfactants will generally be nonionic or anionic. A test procedure has been designed to determine whether a surfactant can be used in the present invention to generate the aphrons. The procedure is as follows: At a low temperature, the low pressure API filtration cell (practice 13 Bl recommended by API), the cylindrical body, which is made of Plexiglas with a thickness of 1.3 centimeters (0.5 inches), is add 200 grams of sand having a particle size on the scale from 50 meshes to 70 meshes (297 μm to 210 μm). The above provides a depth of sand bed of 2.1 centimeters. Filter paper is not used in the cell. 350 ce of the fluid to be tested are added slowly to the cell, the cell is attached, and 7.03 kg / cm3 (100 psi) of nitrogen pressure is applied. The pressure is released after the nitrogen expands through the bed for 30 seconds. By releasing the pressure, the sand bed expands in volume / height as the bubbles expand in the sand bed. The expansion is not uniform, and an average increase in bed height is obtained as measured on the wall of the cell and in the center of the sand bed. Surfactants that increase the bed of sand by at least 50% are considered as preferred for the generation of aphrons in the present invention. Test Fluid: contains 1.5 pounds per 42 gallon barrel (4,285 kg / m3) of xanthan gum hydrated in water and 1 pound per 42 gallon barrel (2,857 kg / m3) of the surfactant to be tested. The surfactant is dispersed in the dispersion of the xanthan gum by spatulation to prevent the generation of foam. The solid surfactants are first dissolved in a suitable dispersible or water soluble solvent before being added to the dispersion of the xanthan gum. The book by Felix Sebba entitled "Foams and Biliquid Foams - Aphrons" John Wiley & amp; amp;; Sons, 1987, incorporated herein by reference, is an excellent source in the preparation and properties of microbubbles. An aphron is made of a nucleus that is often spherical from an internal phase, usually liquid or gas, encapsulated in a thin watery crust. Such a shell contains surfactant molecules placed in such a manner that they produce an effective barrier against fusion with adjacent aphrons. When the aphrons are generated for the first time, they contain a wide-sized distribution that varies up to approximately 200 μm in diameter. At atmospheric pressure, the aprons of a very small diameter very quickly reduce the remaining aphrons in the scale of size from 25 μm to approximately 200 μm. ^ The above is due to the excess pressure within the aprons, which increases as the diameter of the aprons decreases. In this way, the smaller aphrons will tend to shrink in size when transferring their gas to the larger aphrons, which have a lower excess pressure. In the case of drilling wells and service fluids containing aphrons of the present invention, the aphrons are generated in the orifice as the fluid exits the drilling holes. The fluid is under a considerable pressure composed of hydrostatic pressure as well as the pressure loss created by the circulation system. It is believed that such fluid pressure compensates for the excess pressure within the aprons, so that smaller aprons of approximately 25 μm stabilize for a certain time until they circulate to the orifice. In this way, the aphrons are able to penetrate into the pore spaces of the exposed formation where they can expand, due to the low pore pressure within the formation and the sealing of the pore spaces from the entrance of any fluid. The microfractures and the like are filled with aphrons, which similarly expand within the formation to seal the microfractures.

Increases in vapor pressure due to pressure drops, temperature increases and cavity formation are common under drilling conditions. Certain solvents tmay be present in the fluid may also have the effect of vapor pressure to provide the gases needed to form the aphrons. The aprons are large enough to be observed without magnification, they can be observed visually in the fluid as it flows from the hole in the surface tholds the tanks ("holes") before recirculating again. The fluid usually flows through the screen to remove the perforation cuts. The screens having a thickness of 200 meshes (74 μm screen openings) can be used with the fluids of the present invention. Aprons larger than the size of the screen are removed from the fluid. If desired, the particle size of the aphrons in the fluid can be determined with several particle size analyzers tare commercially available. See for example the following articles: (i) "Microbubbles: Generation and Interaction with Colloid Particles", James B. Melville and Egon Matijevic, Chapter 14 in "Foams", R. J. Akers, editor, Academic Press, 1976; (2) "Separation of Organic Dyes from Wastewater by Using Colloidal Gas Aphrons", D. Roy, K.T. Valsaraj and S.A. Kottai, Separation Science and Technology, 27 (5), pp. 573-588 (1992). Such articles are incorporated herein by reference. When re-circulating through the drilling axis, and through the bit, the additional small aphrons tare generated according to the concentration of the surfactant are sufficient. It is desirable to add additional surfactants to the fluid continuously or intermittently until the desired amount of aphrons is produced. The amount of aphrons in the fluid depends on the density required. Generally the fluid contains less than 15% by volume of aphrons. Thus. The density of the circulation fluid can be monitored on the surface and the additional surfactant added necessary to maintain the desired density if the density is very high, and the weight material can be added if the density is very low. The amount of aphrons in the fluid can be determined by adding a known amount of a defoamer or other chemical to destabilize the crusts containing the surfactant and surrounding the aphrons. The measurement in the volume change of the fluid indicates the% by volume of aphrons in the fluid. The concentration of the surfactant required in any case is less than the critical micelle concentration (CMC) of the surfactant. Generally, a concentration of surfactant is from 0.015% by volume to approximately 0.15% by volume, depending on the particular surfactant present in the fluid, if required, preferably from about 0.03% to about 0.1% by volume, assuming tthe surfactant contains about 80% by weight solids. If desired, aphrons can be generated on the surface, using the methods and equipment described in the following U.S.A. Patents, incorporated herein by reference: Sebba Patent No. 3,900,420 and Michelsen Patent No. 5,314,644. The perforation of the well and the repair fluid containing the aphrons can then circulate continuously in the hole. The so-called water soluble polymer present in the fluid to drive the viscosity of low cutting speed of the fluid, also helps to stabilize the aphrons, thus helping to avoid coalescence. It is preferred tthe surfactant be added to the well bore and service fluid under pressure when pumping the surfactant into the fluid. If necessary, the air or other gas can be incorporated into the fluid to introduce more gas to form the aphrons as the fluid leaves the drilling hole in the bottom of the hole, since the fluid contains less than about 15% by volume of the aphrons (encapsulated air or gas). The following examples are illustrative of the present invention and are not considered as limiting. The Circulatory Preventive Fluid System Lost (hereinafter sometimes referred to as System "LCPF") is initially prepared containing 1.5-2.0 Ibm / bbl (4.285-5.714 kg / cm3) of xanthan gum biopolymer and 0.075% by volume of a mixture of non-surface active agents. ionic and anionic (80% concentration, by weight, in an aqueous solution). Such a surfactant mixture shows an average% increase in the sand bed test height of 55%. The biopolymer is hydrated in the fluid, and the surfactant is injected under pressure into the fluid in the feed column. The LCPF system has been evaluated as indicated in the Examples. The low shear velocity viscosity was increased to clean the hole and to create a resistance to movement in the formation, while the encapsulation of the polymer helped to provide the resistance to the wall of the bubble surrounding the aphrons produced in the hole as the LCPF system came out of the drilling hole. The surfactant solution allowed the aphrons to form, reducing the density of the fluid and providing the "bridging of the bubble" to seal the perforated formations. Example 1 BACKGROUND A horizontal re-entry well was planned in the Lodgepole formation in Billings County, North Dakota. The requirements of the drilling fluid were several. The fluid had to withstand the ability to carry out the cuts with a cutter while cutting the window. It also required a character of lubrication and stability in the execution of drilling operations during construction and lateral section, and the ability to provide invasion control during drilling of the Lodgepole production area. The prevention of the loss of circulation was obviously a necessity, since the pressure of the lower orifice was low and the formation was fractured. Due to drilling tools, MWD and existing motors, bridging materials can not be used to control losses. Another factor was the cold weather. The freezing temperatures require some salinity, so brine was used, and the resulting base fluid weighed 9.3 ppg. The fluid was then added to provide a measure of prevention of circulation loss and invasion control due to such an over-equilibrium condition. For these reasons, the well was planned using the LCPF system APPLICATION The LCPF system was prepared and put into circulation in the hole and drilling started. Laminating, opening and construction operations were carried out without any problem. The zone was drilled with the LCPF system containing approximately 7% by volume of aphrons having a density of 8.7 ppg. Such low density, together with the invasion control properties of the system allowed the operator to drill the zone successfully. The side wall was drilled as planned, without losses and with excellent hole conditions.

Example 2 BACKGROUND A well was drilled in the Sprayberry area in western Texas. Circulation with serious losses was common during the drilling of the area. It was necessary to transport 12 lbm-bbl (34.3 kg / m3) or more of circulation material and divert the solids removal equipment. When the content of the lost circulation material dropped, the losses reoccurred. Mud problems and poor drilling conditions were common due to the formation of solids and the decision was made to replace the existing system with the LCPF system.

APPLICATION The LCPF system was prepared and put into operation in the hole to move the fluid in the hole and create aphrons in the fluid. The aphrons, approximately 12% in volume, helped to reduce the density from 9.2 to 8.2 ppg and formed a "Bubble Bridge", helping to stop the movement of the fluid in the zone of loss. Removal of the solids was resumed and the well was drilled to a total depth without any other loss. A subsequent well was drilled in the area using the LCPF system with no loss and no mud problems.

Example 3 Two re-entry wells were drilled in the North Texas area on a portion of the dolomitic reef. Such formation was highly vugular (geoda) with wide and interconnected openings. Severe losses have been experienced in this area.

A typical procedure was to drill in the area, and if there were, all the gains were lost. To regain the circulation medium, large volumes of drilling mud were pumped with high concentrations of bridging materials up to 35 lbm / bbl (100 kg / m3). In this area, the problem was characterized by the presence of a gas cover above the reef area that required 9.0 ppg of fluid to prevent the gas from entering. After careful evaluation of the severe problems in this area, a program was designed to obtain a successful drilling and evaluate these zones using the LCPF System.

APPLICATION The LCPF system was prepared and drilling started while the surfactant was injected.

When the appropriate aphrons were generated in the LCPF system, the system was weighed with barium sulfide at 9.0 ppg and the area was drilled without any loss of circulation. The logging and termination were easily accomplished and the wells began their production without requiring any cleaning or stimulation.

Example 4 A horizontal well was planned in the Sisquoc formation in Santa Barbara Co; California. The solutions to several problems were. crucial to the success of drilling such a well. The Sisquoc formation is a multi-layered zone, sensitive to water containing clays, schist and sand. The transversal horizontal perforation requires the inhibition for the stability of the schistose, the prevention of the formation of beds of cut in the lateral section and of the construction, and the capacity to maintain in circulation at a low pressure to the unconsolidated sands. The use of conventional loss circulation material was prohibited since the use of drilling navigation tools would require adequate drilling of the area. The invasion of the sensitive zone with solids and the lost fluid circulation material also stopped. For these reasons, the well was planned using the LCPF system.

APPLICATION The clay, schistose and multiple sand zones were drilled with the LCPF low density system. Such low density, together with the invasion control properties of the system allowed the operator to successfully perforate the zone. The intermediate part was drilled through the reactive and schistose clay beds while the construction angle at a 92 ° accommodation point where the housing was established, was made without problems. Previous wells experienced severe problems in drilling and in housing operation during such an interval. The side hole was drilled to more than 243.8 meters (800 feet) without losses and with good drilling conditions. A 6 5/8"slotted cover was placed on the bottom without any difficulty.

Example 5 Surfactants were monitored for use in the present invention using the procedure described hitherto. The average percent increased in sand bed height in the following way: Dioctyl Sodium Dioxide Sulfosuccinate Increased Surfactant 118.8. High expansion of the Chubb 96.4 National Foam. Alpha-63.7 olefin sulfonate 2, 4, 7, 9-tetramethyl-5-decin-56.0 4, -diol ethoxylated. Alcohol ethoxylates 56.0 linear Cg-Cn, avg. 6 moles EO / mol Sulfosuccinate 50.6 tetrasodium N- (1, 2-dicarboxyethyl) -N-octadecyl. Mixture of diethanolamides of 50.0 fatty acids. Naphthalene sulfonate of 38.1 diisopropyl sodium. Alcohol ethoxylates 38.1 linear C? 2-C? S, avg. 7 moles EO / mol Alkyl ether sulfate 28.6 modified. Ethoxylated 19.0 octadecylamine-octadecylguanidine complex Sesquistearate of 19.0 methyl glucoside ethoxylate (20 moles) 2, 4,7, 9-tetramethyl-5-. < 10 decina-4, 7-diol Ethoxylated Nonylphenol < 10 (1 mol) Sodium alkyl sulfate < 10 Block copolymer of < 10 polyoxypropylene-polyoxyethylene It is noted that in relation to this date, the best method known to the applicant for carrying out the aforementioned invention is that which is clear from the present description of the invention.

Claims (10)

CLAIMS Having described the invention as above, the following claims are claimed as property:

1. A method for drilling a well in an underground formation, characterized in that a drilling fluid circulates continuously in the well while the drilling is carried out, which comprises the use of a recirculating drilling fluid, an aqueous liquid containing dispersed in the well. same as a polymer that increases the viscosity of low stress velocity-cutting fluid to an extent that the thixotropic index is at least 10, at least one water-soluble surfactant and aphrons generated in the fluid, the drilling fluid contains less than approximately 15% by volume of aphrons.

The method according to claim 1, characterized in that the aprons are generated with the circulation of the fluid through the drill pipe and through the openings in the auger where the aprons are generated by the pressure drop according to the fluid it comes out of the trephine and comes into contact with the formation that is being drilled.

3. The method according to claim 1, characterized in that a gas is mixed with the fluid.

4. The method according to claim 1, characterized in that the surfactant provides an average percentage expansion of a sand bed of at least about 50% when evaluated according to the following test procedure: at a low temperature, cell API filtration of low pressure (practice 13 Bl recommended by API), to the cylindrical body which is made from Plexiglas with a thickness of 0.5 inches (1.3 centimeters), 200 grams of sand having a particle size in the 50 mesh to 70 mesh range (297 μm to 210 μm); the above provides a sand bed depth of 2.1 centimeters; no filter paper is used in the cell; 350 cc of the fluid to be tested is slowly added to the cell, the cell is assembled, and 7.03 kg / cm2 (100 psi) of nitrogen pressure is applied; the pressure is released after nitrogen is blown through the bed for 30 seconds; by releasing the pressure, the sand bed expands in volume / height as the bubbles in the sand bed expand; the expansion is not uniform, and an average increase in bed height was obtained as measured on the wall of the cell and in the center of the sand bed; wherein the test fluid comprises 4.285 kg / cm3 of the xanthan gum well hydrated in water and 2.857] q / mJ ie surfactant to be tested, wherein the surfactant is propagated in the dispersion of the Xanthan gum by a very low shear mixing mixture to avoid foaming.

5. The process according to claim 1, 2, 3 or 4, characterized in that the surfactant is injected into the drilling fluid under pressure.

6. The process according to claims 1, 2, 3 or 4, characterized in that the polymer is a biopolymer.

7. Drilling fluid and well repair that can circulate continuously in a hole and that is characterized in that it comprises an aqueous liquid, a polymer that increases the viscosity of low shear rate of the fluid to the extent that the thixotropic index of the fluid is of at least 10, a surfactant, and aphrons that are generated in the encapsulation of the gas in the fluid by a thin crust containing an aqueous surfactant wherein the molecules of the surfactant are positioned in such a way that they produce a effective barrier against fusion with the adjacent aphrons, the fluid contains less than about 15% by volume of aphrons.

8. The drilling and repair fluid according to claim 7, characterized in that the polymer is a biopolymer.

9. The drilling and repair fluid according to claim 7 or 8, characterized in that the surfactant provides an average percentage expansion of a bed of sand of at least about 50? when evaluated in accordance with the following test procedure: at a low temperature, a low pressure API filtration cell (practice 13 Bl recommended for API), to the cylindrical body that is made of Plexiglas of 1.3 centimeters (0.5 inches) of thickness, 200 grams of sand having a particle size in the range of 50 mesh to 70 mesh (297 μm to 210 μm) are added; the above provides a sand bed depth of 2.1 centimeters; filter paper is not used in the cell; 350 ce of the fluid to be tested are added slowly to the cell, the cell is assembled, and 7.03 kg / cm2 (100 psi) of nitrogen pressure is applied; the pressure is released after the nitrogen is blown through the bed for 30 seconds; by releasing the pressure, the fluid bed will expand in volume / height as the bubbles expand in the sand bed; the expansion is not uniform, and the average increase in bed height is obtained as measured in the wall of the cell and in the center of the sand bed; wherein the fluid bed comprises 4,285 kg / m3 of the well xanthan gum, hydrated, in water and 2857 kg / m of the surfactant to be tested, wherein the surfactant is propagated in the gum dispersion of xanthan by means of a mixing of,. ) very low shear to avoid the formation of a foam.

10. In a method of drilling or repairing a well in an underground formation containing areas of lost or depleted circulation, reservoirs of low pressure where a drilling fluid or well repair is circulated within the borehole, the method of prevention d ". ' to loss of circulation in the same, fil to use drill hole and repair of the well, the fluid according to claims 7, 8 or 9.