MXPA00000975A - Fluid loss control additives and subterranean treatment fluids containing the same - Google Patents

Abstract

Selectively cross-linked starches are disclosed that are useful as fluid loss control additives in subterranean treatment fluids comprising starches that are cross-linked to a Brabender peak viscosity of about 800 to about 1250 Brabender units after about 40 to about 70 minutes at about 92°C and provide good fluid loss control over a temperature range of from about 20°C to about 160°C (68°F to 320°F).

Description

ADDITIVES OF CONTROL OF LOSS OF FLUID AND FLUIDS OF UNDERGROUND TREATMENT THAT CONTAIN THEMSELVES BACKGROUND OF THE INVENTION 5 FIELD OF THE INVENTION This invention relates to interlaced starches which are useful as fluid control control additives in aqueous basement treatment fluids, such as drilling, reconditioning and completion fluids.

RELATED PREVIOUS TECHNIQUE The interlaced starches of this invention can be used advantageously in oil field applications. Specifically, starches can be incorporated into fluids used in operations when there is contact with an underground formation. Drilling, reconditioning, and completion fluids are examples of fluids used in underground formations. The two drilling fluids can be used for any of several functions that allow to evaluate or produce a deposit (formation) for oil, gas or water. The drilling fluid can be pumped inwards of the drill hole during drilling to cool the bit and buff rock particles that are cut by the bit. Frequently, a "drilling" lubricating fluid is used when drilling the production zone. The reconditioning fluids can be used to perform one or more of several corrective operations in an oil well in production in order to restore or increase production. Among the reconditioning operations are, but not limited to, increase the depth, retroteponar, extract and reinsert a casing, cement under pressure, dynamite and acidify. Completion fluids can be used to perform one or more of a variety of applications in oilfields such as, for example, but not limiting, cementation, use of spacers, drilling, gravel filtration, installation of tubing, widening of the bottom of the perforations, facing, 'in addition to a variety of simulation techniques such as acidification and the like. Underground treatment fluids are used in well operations, particularly in oil well operations, for various purposes. Underground treatment fluids are usually prepared where the well is located by adding an agent of viscosity in a base fluid. The viscosity agent thickens or increases the viscosity of the base fluid, thereby increasing the ability of the fluid to suspend or buff rock particles. The underground treatment fluid may also advantageously contain other additives used in the form ^ g ^^^ ^^^^^^ wÉ ^ gj ^ jj ^^ * ^^^ i ^ y ^ conventional in well treatment operations, as necessary, based on the specific requirements of the site and conditions environmental A common problem related to the use of underground treatment fluids is the loss of fluid in the formation surrounding the vicinity of the borehole. Fluid loss control additives are added to the underground treatment fluids to limit the exposure of the formation and also to control the filtration of the liquid components into the surrounding underground formation. As a result, underground treatment fluids that are most useful in well operations have the ability to retain a lot of water. It is desirable that the underground treatment fluid retain a high water retention capacity under adverse environments encountered during its use. For example, there are high temperature conditions in deep wells, where operating temperatures often exceed 121 ° C. In shallow wells there are low temperature conditions, as in the areas of a well that are closer to the surface of the earth. By using underground treatment fluids containing brine, high salinity conditions are created. Consequently, the fluid loss control additive must It must be stable over a wide range of temperatures and must function properly in high or low salinity environments. Natural starches are a well-known type of material and very useful as fluid loss control additives. However, also ? *5" '^ * ^ * ** * ^^ ¡¡¡^ ^ ¿it is well known that starches do not have long-term stability and tend to degrade when exposed to high temperatures. For example, at temperatures exceeding 107 ° C, natural or conventional starches begin to degrade and fail to provide adequate fluid loss control. Various approaches have been followed to increase the stability of the starches in order to obtain more stable drilling fluids. For example, U.S. Patent No. 4,090,968 discourages the use of quaternary ammonium starch derivatives as fluid control additives having stability at elevated temperatures. These derivatives were made by a reaction of the starch with epichlorohydrin and a tertiary amine. A three-component thixotropic fluid for well drilling, consisting of an interlaced potato starch, a heteropolysaccharide derived from a carbohydrate by bacteria of the genus Xanthomonas, and hydroxyethylcellulose, which allows better control of water loss, is described in FIG. U.S. Patent No. 4,422,947. U.S. Patent No. 4,652,384 discloses the use of selected interlaced starches to provide control of fluid loss at elevated temperatures. Starch, which is entangled to a fairly high degree under specific conditions, must be activated at elevated temperatures for more than four hours in order to achieve the necessary efficiency.

Other fluid combinations have been developed for the treatment of wells, incorporating Xanthomonas gum and a hydroxypropyl starch, entangled with epichlorohydrin, as described in U.S. Patent No. 4,822,500. This combination of additives in particular interacts synergistically to increase suspension characteristics and reduce fluid loss. U.S. Patent No. 5,009,267 discloses fluid loss control additives for fracture fluids composed of combinations of two or more modified or crosslinked starches, or combinations of one or more natural starches with one or more modified starches. Although many of the interlaced starch compositions described above offer improvements over conventional starches, the industry still requires a starch additive that can be easily dispersed and that provides good fluid loss control over a wide range of temperatures, while retaining also its stability in fluids containing brine.

Hl ^ j BRIEF DESCRIPTION OF THE INVENTION This invention relates to interlocked starches in the form • Selective and combinations of these interlaced starches which are useful as fluid loss control additives and which provide good control of fluid loss over a wide range of temperatures. More specifically, this invention relates to fluid loss control additives for use in underground treatment fluids containing starches that have been entangled and having a Brabender viscosity peak of about 800 and up to about 1250 Brabender units after 40 to about 70 minutes, at about 92 ° C, and provides good control of fluid loss over a wide temperature range of between about 20 ° C to about 160 ° C . This invention also relates to selectively entangled starches that are spray dried to further improve their properties. In addition, this invention covers underground treatment fluids containing the defined interlaced starches.

DETAILED DESCRIPTION OF THE INVENTION In this invention, the ability to provide a fluid loss control additive that is effective over a wide range of temperatures is demonstrated by the use of a selectively crosslinked starch. This result is surprising and unexpected, as can be seen in the specialized literary production and in the products available on the market that show the use of various modified starches and starches, and none of which mentions the specific starches of this invention or achieves the degree of fluid loss control achieved in a wide range of 5 temperatures. An important feature of this invention is the amount of entanglements to which the starch is exposed, that is, the amount of treatment or the degree of entanglement. Although it is difficult to measure this characteristic of the treated starch, particularly at low levels, one of the best ways to determine the amount of interlacing is to measure the viscosity of the starch. It is well known to measure the viscosity of the interlaced starch using a visco-amyl graph of C. W. Brabender. By means of this measuring device and method, the starches of this invention are interlaced to obtain a Brabender viscosity peak of around 800 to about 1250, preferably around 920 to about 1150 Brabender units after about 40 to about 70 minutes at about 92 ° C. The test procedure to measure this characteristic is described below. The interlaced starches used in this invention can include starches treated with various multifunctional crosslinking agents. More specifically, the crosslinking agents used in this invention include epichlorohydrin, phosphorus oxychloride, adipic-acetic anhydrides and sodium trimetaphosphate. Epichlorohydrin and Phosphorous oxychloride are the preferred entanglement agents and epichlorohydrin is the most preferred agent. The starches that can be used as a base material in the manufacture of the interlaced starches of this invention can be derived from any vegetable source including corn, potatoes, wheat, rice, sago, tapioca, waxy corn, waxy rice and sorghum. Also useful are the conversion products derived from any of the above-described base materials, including oxidized starches, which are treated with oxidants such as sodium hypochlorite, and low boiling or fl ow starches, created by enzyme conversions or by a mild acid hydrolysis. The preferred starches are corn, waxy corn, potato, wheat and tapioca, with special preference for waxy corn. The interlaced starches of this invention are generally made using known techniques by reacting the starch with a relevant interlacing agent in an aqueous solution under alkaline conditions. The desired interlaced starches will have a relatively low degree of specified entanglement, defined by Brabender viscosity as described above. The amount of interlacing agent used to achieve this degree of entanglement will change to some extent depending on the conditions and materials used. Commonly, the amount of crosslinking agent used is about 0.05% to 0.15%, and preferably about 0.1%, by weight of the starch.

In addition to utilizing the a? || jj & it is selectively entangled as defined herein, it has been found that pregelatinization of starches using a spray-drying process results in a product with improved characteristics. It is believed that spray-dried starches have a more uniform particle size which leads to a more uniform and controlled thickening. The use of the pregelatinization methodology by spray drying produces starches that have a uniform particle size, avoiding the degradation, often important, that occurs when dehydrating and getalinizing the starch by means of drum drying or extrusion methods. The pregelatinization of the interlaced starches of this invention can be achieved by the spray dehydration method using a simple or dual spray / vapor injection process, described in U.S. Patent No. 4,280,851, U.S. Patent No. 4,600,472 or U.S. Patent No. 5,149,799, the disclosures of which are appended hereto by reference. In this process, a mixture of granulated starch is cooked or gelatinized in an atomized state. The starch that will be cooked is injected through the nozzle of an atomizer into a steam that has been atomized in order to heat the starch to a suitable temperature to gelatinize it. A closed chamber surrounds the injection nozzles of the atomizer and the heating medium and delimits an opening located so as to allow the vaporized and heated starch to escape from the chamber. The arrangement is such that the time elapsed between the passage of the starch vapor through the chamber, that is, the atomization chamber and through the exhaust opening, defines the gelatinization time of the starch. The resulting spray dried dehydrated pregelatinized starch is a uniformly gelatinized starch in the form of serrated spheres, with the majority of granules intact and intact and swelling upon rehydration. The nozzles that should be used in the preparation of these starches are described in U.S. Patent No. 4,610,760, which is incorporated herein by reference. The steam injection / dual atomization process as described above can be described more specifically as the pregelatinization of the starch by: a) mixing the starch in an aqueous solvent, b) atomizing the mixture into a closed chamber, and c) interpolating a heating medium in the atomized mixture inside the closed chamber to cook the starch, and the size and shape of the chamber must be adequate to be able to maintain a control of the temperature and humidity of the starch for a sufficient period of time for this be cooked A simple steam injection / atomization process for cooking and drying the spray starch is described in the aforementioned U.S. Patent No. 5,149,799 and comprises of: a) suspending the starch in an aqueous medium, Í- Á: - £ i £ dj ks ta¿j i | b) pouring a jet of the starch suspension at a pressure of between 3.515 kg / cm2 gauge at 17.575 kg / cm2 gauge into a spray chamber inside a nozzle, c) injecting a heating medium into the atomizing chamber at a pressure of between 3.515 kg / cm2 gauge and 17,575 kg / cm2 gauge, d) cooking and atomizing the starch suspension simultaneously, while the heating medium forces the starch out through the exhaust opening to the bottom of the chamber, and e) dehydrate the atomized starch. It is further noted that it is possible to use combinations of selected interlaced starches. For example, a combination of an entangled starch of epichlorohydrin together with an interlaced starch of phosphorus oxychloride can be used. The proportions of the two intertwined starches are not limited to, but in general are, a weight ratio of about 4: 1 to a ratio of 1: 4 of crosslinked starch of epichlorohydrin to the crosslinked starch of phosphorus oxychloride. Preferably, the combination comprises a mixture of about 1: 1, by weight, of the starches. The combinations of the intertwined starches of epichlorohydrin and phosphorus oxychloride can be prepared by dry mixing the spray dried starches and prepared separately. Also, the combinations can be prepared simultaneously by dehydrating by wet mixtures of the interlaced starches.

The interlaced starches of this invention are employed in underground treatment fluids in an amount sufficient to provide fluid loss control and reduce fluid loss over a wide range of temperatures. The effective amount of interlaced starches will vary depending on the other components of the underground treatment fluid, as well as the geological characteristics and conditions of the underground formation in which it is used. Typically, the interlaced starch fluid loss control additive can be used in an amount of about 2,853 to about 28.53 kilograms per m 3 of the underground treatment fluid, preferably from about 8,559 to about 17,118 kg / m 3 (of about 3 about 6 pounds per barrel). The term "barrel", as used herein, means a barrel containing 158.76 liters of fluid. In addition to the interlaced starches, the underground fluids may contain other components such as a base fluid and often a viscosity agent. The base fluid may be an aqueous system containing fresh water, salt water and / or brine. Brine is a solution ^ aqueous salt containing soluble salts of potassium, sodium, calcium, zinc and / or cesium and the like. The viscosity agent may be xanthan gum, guar gum, other polymers and / or clays such as bentonite and / or mixtures of these materials and similar materials. Other additives known for use in these subterranean fluids include, but are not limited to, corrosion inhibitors, antioxidant oxygen scavengers, biocides, fracturing agents, surfactants as well as mixtures thereof and the like. 1i i ^ ltMfe «M ^ iii Oxygen scavengers and antioxidants can be added to underground treatment fluids to reduce the deleterious effects of oxygen, that is, the oxidative degradation of the fluid loss control additive, viscosity agent and / or other additives. Illustrative oxygen scavengers include sodium sulfite, sodium dithionite, potassium metabisulfite, and the like. Illustrative antioxidants include magnesium oxide, triethanolamine (TEA), tetraethylenepentamine (TEPA), and the like. The addition of oxygen scavengers or antioxidants to underground treatment fluids can provide fluids having increased viscosity properties and fluid loss control, such that the excellent fluid loss control can be maintained over a wide temperature range. The amounts or proportions of each of the components and additives used in the underground treatment fluid will vary greatly depending on the intended use and purpose of the treatment fluid as well as the geological characteristics and conditions of the underground formation in which it is employed. the fluid. Nevertheless, the amount of base fluid generally present in the fluid is from about 25% to about 99% of the fluid. The viscosity agent may be present in an amount of from about 0% to about 20% by weight of the fluid. Other additives, such as those listed above may be present in a treatment fluid generally in an amount of from about 0% to about 10% by weight of the fluid.

Underground treatment fluids for specific purposes require special additives. For example, drilling fluids may also have weighting agents such as barite to control formation pressure. Further information on the composition of drilling fluids can be found in the fifth edition (1988) of "Compositon and Properties of Drilling and Completion Fluids" by Darley and Gray, the description of which is incorporated herein by reference. Oil well cement suspensions can also be classified as underground fluids and often contain Portlan cement, accelerator retarders and similar products. The weighting agents in drilling fluids and cementing agents in slurries or separating fluids may be used in amounts of up to 50% or more, by weight of the fluid, depending on the requirements of the geological formation. Additional information on the composition of cement suspensions can be found in the SPE monograph of 1987 on "cementing" by D.K. Smith, whose description is incorporated herein by reference. The acidifying fluids will include acid, typically in amounts of about 1% about 37% by weight, to record the formation. The 1979 SPE monograph "Acidizing Fundamentals" by Williams et al., The disclosure of which is incorporated herein by reference, further describes the uses and composition of acidifying fluids. Similarly, other additives of special purpose could be used for other applications. The underground treatment fluids of this invention contain the interlaced starch or starch mixture and any viscosity agent, ta * ^. . ^^^^^ base fluid and other additive components, present in such proportions as are appropriate for the specific well site as determined by those skilled in the art. For example, a typical drilling fluid containing the fluid loss control additives of the present invention can be prepared by mixing 1,816 kg of the interlaced starch of this invention, 0.363 kg of the high viscosity polyanionic cellulose, 0.499 kg of rubber of xanthan and 22.7 kg of calcium carbonate in a barrel (158.76 I) of water or brine. As described above, the interlaced starch fluid loss additives of this invention provide good control of fluid loss over a wide temperature range and in an environment where tolerance to salinity, shear stress and high temperature is often required. , although the degree of fluid loss is a relative term depending on the actual operating conditions, a fluid loss of less than about 100 g, as shown by the API low-temperature-low pressure (LTLP) tests and the API high temperature-high pressure (HTHP) tests as described below, have been obtained when using the interlaced starch additives of this invention. It has been found that this level of fluid loss control occurs over a wide range of temperatures from about 20 ° C to about 150 ° C in the moderate to high salinity environment of seawater or saturated sodium chloride solution, used as base fluids. The addition of oxygen scavengers or antioxidants to the underground treatment fluids containing the interlaced starches of this invention can provide increased fluid loss control in a My range of temperature range is, for example, up to 160 ° C. The use of higher concentrations of fluid loss control additives and / or viscosity agents in the underground treatment fluids of this invention can similarly increase the control of fluid losses at very high temperatures. The following examples have been designed as an illustration of certain preferred embodiments of the invention and a limitation of the invention is not implied. In these examples, the concentration of reactants and components of the composition are expressed as parts by weight, unless otherwise indicated. All temperatures are reported in degrees centigrade unless otherwise specified. The following test procedures were used to evaluate the interleaved starch fluid loss control additives according to this invention. 15 Brabender viscometer test In this procedure a Visco-Amylo graph of Brabender. This is a standard device, easily available in the market and is a rotary cup twist vicosimeter of record, which measures and records the Viscosity evident at fixed temperatures or varied temperature at a uniform speed. The procedure to evaluate the interlaced starch is the following: ? j & 1) A sample of the interlaced starch, before pregelatinization by spray drying, is suspended in a solution containing distilled water and glacial acetic acid ( 2.06% by weight of the total charge) at a content of 6.0% anhydrous solids by total weight. 2) The sample is transferred to a brabender cup. The cup is then inserted into the viscosity, 3) The glass / mercury thermoregulator is set at 92 ° C and the sample is heated at a rate of four degrees per minute at 92 ° C. The sample is then maintained at approximately 92 ° C until it reaches the peak viscosity, and 4) Peak viscosity is recorded. Also recorded is the time in minutes, required for the sample to reach the peak viscosity after reaching 92 ° C (ie, the total time the sample is at 92 ° C until the sample reaches peak viscosity).

TEST PROCEDURE FOR FLUID LOSS Fluid preparation The control additives for starch fluid loss were tested in two aqueous systems: sea water and 26% NaCl brine (w / w, saturated). Seawater was prepared by dissolving 18.88 g of dry "Sea-Salt" (ASTM D-1141-52, Lake Products Company, Maryland Heights, Missouri) in 450 g of prepared tap water (the tap water prepared is deionized water containing 1000 ppm NaCl and 110 ppm CaCl 2). The 26% NaCl base fluid was prepared by dissolving 141.4 NaCl in 398.6 g of deionized water. Before adding the salt, tap water or prepared deionized water was added to the Hamilton Beach malt mixer cups and mixed at about 4000 rpm with a Hamilton Beach malt mixer. An amount of 3.1383 kg / m3 of xanthan gum (1.43 g XCD, a product of NutraSweet Kelco Co., a unit of Monsanto Company, St. Louis Missouri) was added into each mixing cup and allowed to mix for a time of about 3 to 5 minutes. A drop of 5 M potassium hydroxide was added to each mixing cup to increase the pH to a value between 8.5-9 and the mixture was mixed for 20 minutes at 11,000 ± 200 rpm. At the end of the 20 minutes of mixing, the appropriate amount of either "Sea-Salt" or NaCl was added and the fluid was mixed for an additional 10 minutes at 11,000 rpm. 15 An amount of 2.2824 kg / m3 of AquaPAC®-Regular, which is a high viscosity polyanionic cellulose used to facilitate viscosity and filtration control (1.07 g, a product of Aqualon Co., Houston, Texas) and a sample of 11, 412 kg / m3 of starch (5.14 g), prepared as described below, were mixed dry with a spatula, then added to the fluid mixture. Mixing continued at 11,000 rpm for 15 minutes. The mixer was removed from the mixer and 142.65 kg / m 3 CC-103 (64.29 g, calcium carbonate, a product of ECC International Co., Sylacauga, Alabama) was added. The mixing cup was returned to the mixer and mixed for 5 more minutes at 11,000 rpm. Octanol (2 drops, foam remover) was added and the resulting mixture was mixed for one more minute. Finally, the pH of the fluid was adjusted with 5 M potassium hydroxide to obtain a pH between 8.5 and 9.

Low Temperature / Low Pressure API Fluid Loss Test Procedure (LTLP) Non-aged samples of the fluid prepared above were tested for fluid loss using a standard low temperature-low pressure fluid loss (LTLP) test from the Institute North American Petroleum (API) at room temperature (22.22 ° C). Samples of the test fluid (300 ml) were mixed again using a Hamilton Beach Mixer for approximately 1 minute to 11 minutes., 000 rpm, then emptied into an API fluid loss filter cell (Fann Instrument Company, Houston, Texas, Model 12B, No. 30501) at approximately 1.27 cm from the top of the cell. Before sealing the cell, an "O" ring and Wattman 50 filter paper were placed in it. The LTLP fluid loss test of the API was performed at room temperature in the following manner. The cell was placed on a filter press, preset at 7.03 kg / cm2 using nitrogen pressure, and pressurized for 30 minutes. The fluid that was lost from the pressurized cell was collected in a tared beaker and weighed. ^^ s ^ ßijfe ^ High Temperature / High Pressure Fluid Loss Test Procedure (HTHP) Before conducting the API HTHP Fluid Loss test, the samples were aged for 16 hours at elevated temperatures of 5 hours. next way.

Hot rolling process The fluid containing the test starch sample was emptied in a 260 ml high temperature aging cell (Fann Instrument Co., Houston, Texas, Part Number 76000). The cell is made of stainless steel. The fluid filled the cell approximately 0.635 cm from the top of the cell. The cell was covered and the outlet cover was screwed. The cell was pressurized to approximately 10,545-14.06 kg / cm2 and then the valve stem was carefully squeezed. Afterwards, the cell was placed in the oven laminate (Fann Instrument Co., Houston, Texas, Part Number 7000) that had been preheated to test the temperature. The rolling mill is a standard API rolling mill with the exception that Eurotherm temperature controllers (Eurotherm Co., Reston, Virginia, Model 808) were added to reduce the temperature variation during aging. The cell was laminated to the test temperature for 16 hours (oveht). The sample was removed from the furnace, cooled to room temperature, depressurized, then tested for high temperature / high pressure (HTHP) fluid loss as described below. g ^ iÜ buate High Temperature / High Pressure API Fluid Loss Test (HTHP) Once the sample had cooled, it was placed in a cold 175 mL HTHP fluid loss cell (Fann Instrument Co., Number of 5 Part 38750) that contains a Wattman filter paper 50 (or equivalent). The lower valve stem of the cell was closed to prevent loss of fluid before heating. The top lid was attached and the cell was placed in a preheated cell clip. A nitrogen pressure line was attached to the upper valve stem and the cell was pressurized to approximately 14.06 kg / cm2 for prevent the fluid from boiling during heating. Once the cell reached the temperature, a condenser was added to the lower valve stem of the cell and a back pressure of 7.03 kg / cm2 of nitrogen pressure was added to the condenser. The lower valve stem of the cell was then opened to allow the loss of fluid and the pressure of the valve stem to occur.

Top 15 was increased to 42.18 kg / cm2 (to provide a pressure difference of . 15 kg / cm2). The loss of fluid was measured in a period of 30 minutes or until flfe the complete fluid loss occurred, whichever occurred first. The loss of fluid was measured by weight. The fluid loss reported was exactly twice the loss of fluid collected (according to API procedures) for compensate for the small surface area of the filter paper compared to the low temperature, low pressure fluid loss cell.

Differences between the LTLP and HTHP tests The tests were conducted according to the "API Recommended Practice, Standard Procedure for Field Testing Water-Based Drilling Fluids" (Standard Procedure for Fluid Field Test for Water-Based Drilling, of the Recommended Practice of API), API RP 13B-1, first edition, June 1, 1990. Tests for fluid loss at room temperature (22.22 ° C) were conducted using a low temperature / low pressure test procedure (LTLP) of the API (API Proc.RP 13B-1 Sec. 3.3). All fluid loss tests above room temperature were performed using the high temperature / high pressure test (HTHP) procedure of the API (Proc API RP 13B-1 Sec. 3.5). The HTHP test uses a different equipment than the LTLP test which considers the heating of the filter press and higher pressure differences. The HTHP test uses a pressure difference of 35.15 kg / cm2, while the LTLP uses a pressure difference of 7.03 kg / cm2. Also, the HTHP test uses filter paper that is half the surface area of the LTLP test and, therefore, the fluid loss reported for the HTHP test is double what was collected.

AND IpPLO 1 Preparation and testing of entangled starch of epichlorohydrin At room temperature, 1000 g of waxy corn starch was suspended with 1500 g of water. Sodium hydroxide was added slowly to the suspension, as a 3% solution, at a pH of about 12.0 (25 ml of the reaction suspension should require 18-20 ml of 0.1 N HCl to neutralize the phenolphthalein end point). Epichlorohydrin (0.13% by weight) was added to the suspension. The reaction mixture was allowed to react at 40 ° C for 17 hours, cooled to room temperature, and neutralized to a pH of 6.0 with a 10-30% solution of hydrochloric acid. The starch was then filtered, washed and dried to provide a dry, non-gelatinized powder. A sample of interlaced starch was analyzed to determine its peak viscosity using a Visco-Amylo Graph of C.W. Brabender as described above, and was found to have a peak viscosity of 1020 Brabender units after 52 minutes at 92 ° C. The dry interlaced starch was suspended in water at 20-30% anhydrous solids by weight. The starch was spray-dried to pregelatinize, using the procedure described above, and in U.S. Patent Nos. 4,280,851 and 4,600, 472. The resulting pregelatinized and dry powder was tested for fluid loss using both the LTLP fluid loss test of the API (temperature 22.22 ° C environment) like the f > 8kM ß of HTHP API, described above. The test was carried out both in seawater and in a saturated NaCl solution (26%) and showed the results shown in Tables 1 and 2 below.

TABLE 1 Loss of interlinked starch fluid of epichlorohydrin / sea water Temperature (° C) Loss of fluid (g) 22.22 6.4 37.77 6.9 65.55 12.5 79.44 18.5 107.22 46.1 121.11 45.7 132.22 57.0 143.33 64.8 Loss of interlinked starch fluid of epichlorohydrin / NaCl1 solution Temperature (° C) Loss of fluid (g) 22.22 4.9 37.77 6.9 65.55 9.1 10 79.44 21.3 107.22 48.7 121.11 64.7 132.22 55.0 137.77 15.3 15 1Saturated aqueous solution of NaCl (26%) EXAMPLE 2 Preparation and testing of interlinked phosphorus oxychloride starch At room temperature, 1000 g of waxy maize starch was suspended in an aqueous solution of sodium chloride (1500 g of water, 0.5% of NaCl by weight of the starch). A 3% solution of sodium hydroxide was added slowly to this suspension at a pH of ft? - «- approximately 12.0 (25 ml of the reaction suspension should require 16-18 ml of 0.1 N HCl to neutralize the phenolphthalein end point). Phosphorus oxychloride (0.1%) was added and the reaction mixture was allowed to react for 35 minutes. The resulting reaction mixture was neutralized to a pH of 6.0 with a 10-30% solution of hydrochloric acid. Then the starch was filtered, washed and dried. A sample of the interlaced starch was analyzed for its peak viscosity using a Visco-Amylo Graph of C.W. Brabender and was found to have a peak viscosity of 1000 Brabender units after 40 minutes at 92 ° C. The interlaced starch was spray dried and tested for fluid loss as in Example 1 with the results shown below in Tables 3 and 4.

TABLE 3 Loss of interlocked starch phosphorus oxychloride / seawater fluid Temperature (° C) Loss of fluid (g) 22.22 6.2 121.11 8.1 126.66 23.9 JÉÉfflflfr -r1 | i || r ^ "flh ^^ 3 TABLE 4 Loss of interlocked starch fluid of phosphorus oxychloride / NaCl1 solution Temperature (° C) Loss of fluid (g) 22.22 5.3 121.11 21.10 126.66 75.6"" Saturated aqueous solution of NaCl (26%) EXAMPLE 3 A mixture (ratio of 1: 1 by weight) of interlaced starch of epichlorohydrin (epi) and crosslinked starch of phosphorus oxychloride was made (both prepared as in examples 1 and 2), and tested for fluid loss in seawater and saturated NaCl solutions as in the previous examples. The results are shown in Tables 5 and 6 below.

TABLE 5 Loss of fluid in the mixture of intertwined epichlorohydrin / phosphorus oxychloride (1: 1) in seawater Temperature (° C) Loss of fluid (g) 22.22 6.9 37.77 6.1 65.55 15.7 121.11 33.8 143.33 47.9 TABLE 6 Loss of fluid in the mixture of intertwined epichlorohydrin / phosphorus oxychloride (1: 1) in a solution of NaCl1 Temperature (° C) Loss of fluid (g) 22.22 5.0 37.77 6.3 65.55 9.7 121.11 31.0"" Saturated aqueous solution of NaCl (26%) ¡G | g | g¡i agg? Other variations or modifications, which will be obvious to those skilled in the art, are within the scope and teachings of this invention. This invention should not be limited except by what is stated in the following claims.

Claims (28)

NOVELTY OF THE INVENTION CLAIMS

1. A fluid loss control additive for use in an underground treatment fluid to provide good fluid loss control at a temperature range of about 20 ° C to about 160 ° C consisting of an interlaced starch which has a Brabender peak viscosity of about 800 to about 1250 10 Brabender units after approximately 40 to approximately 70 minutes at approximately 92 ° C when subjected to a Brabender viscometer test.

2 - The fluid loss control additive according to claim 1, further characterized in that the starch is entangled with a The agent selected from the group consisting of epichlorohydrin, phosphorus oxychloride, adipic-acetic anhydride, and sodium trimetaphosphate.

3.- The fluid loss control additive in accordance with the • claim 2, further characterized in that the starch is selected from the group consisting of corn, waxy corn, potato, wheat and tapioca.

4. The fluid loss control additive according to claim 3, further characterized in that the interlacing agent is epichlorohydrin or phosphorus oxychloride. a ^ * ^^^ M6faJh *

5. - The fluid loss control additive according to claim 4, further characterized in that the starch is waxy corn.

6. The fluid loss control additive according to claim 3, further characterized in that the interlaced starch has a 5 Brabender peak viscosity from about 920 to about 1150 Brabender units after about 40 to about 70 minutes at about 92 ° C.

7. The fluid loss control additive according to claim 6, further characterized in that the interlaced starch has a fluid loss of less than about 100 g when subjected to a low temperature-low fluid loss test. pressure (LTLP) or high temperature - high pressure (HTHP) of the North American Petroleum Institute, at a temperature range of approximately 20 ° C to approximately 160 ° C.

8. The fluid loss control additive according to claim 7, further characterized in that the entanglement agent is epichlorohydrin and the starch is waxy corn.

9. The fluid loss control additive according to claim 3, further characterized in that the crosslinked starch is a mixture of about 4: 1 to about 1: 4 by weight of crosslinked starch of epichlorohydrin and crosslinked oxychloride starch of phosphorus.

10. The fluid loss control additive according to claim 9, further characterized in that the interlaced starch is a mixture of about 1: 1 by weight of interlinked starch of epichlorohydrin and crosslinked starch of phosphorus oxychloride.

11. The fluid loss control additive according to claim 10, further characterized in that the starch that is in the entangled starch of epichlorohydrin and the crosslinked starch of phosphorus oxychloride is waxy corn starch.

12. The fluid loss control additive according to any of claims 1-11, further characterized in that the interlaced starch is pregelatinized by spray drying.

13. An underground treatment fluid composition that provides good fluid loss control at a temperature range from about 20 ° C to about 160 ° C consisting of a base fluid, a viscosity agent and an effective amount of a fluid loss control additive, which is an entangled starch with a Brabender peak viscosity of about 800 to about 1250 Brabender units after about 40 to about 70 minutes at about 92 ° C when subjected to the viscometer test of Brabender.

14. The underground treatment fluid composition according to claim 13, further characterized in that the underground treatment fluid is a drilling fluid, a fluid for reconditioning, or a completion fluid.

15. - The underground treatment composition according to claim 14, further characterized in that it is entangled with an agent selected from the group consisting of epichlorohydrin, phosphorus oxychloride, adipic-acetic anhydride, and sodium trimetaphosphate.

16. The underground treatment fluid according to claim 15, further characterized in that the starch is selected from the group consisting of corn, waxy corn, potato, wheat and tapioca.

17. The underground treatment fluid according to claim 16, further characterized in that the interlacing agent is epichlorohydrin or phosphorus oxychloride.

18. The underground treatment fluid according to claim 17, further characterized in that the starch is waxy corn.

19. The underground treatment fluid according to claim 16, further characterized in that the interlaced starch has a Brabender peak viscosity of about 920 to about 1150 Brabender units after about 40 to about 70 minutes at about 92 ° C.

20. The underground treatment fluid according to claim 19, further characterized in that the interlaced starch has a fluid loss of less than about 100 g when subjected to a low temperature-low pressure fluid loss (LTLP) test. or at high temperature - high pressure (HTHP) of the North American Petroleum Institute, at a temperature range of about 20 ° C to about 160 ° C.

21. The underground treatment fluid according to claim 20, further characterized in that the interlacing agent is epichlorohydrin and the starch is waxy corn.

22. The underground treatment fluid according to claim 16, further characterized in that the interlaced starch is present in an amount of about 2853 kg / m3 to about 28.53 kg / m3 of underground treatment fluid.

23. The underground treatment fluid according to claim 22, further characterized in that the interlaced starch is present in an amount of about 8.559 kg / m3 to about 17.118 kg / m3 of underground treatment fluid.

24. The underground treatment fluid according to claim 23, further characterized in that the interlacing agent is epichlorohydrin and the starch is waxy corn.

25. The underground treatment fluid according to claim 16, further characterized in that the interlaced starch is a mixture of about 4: 1 to about 1: 4 by weight of crosslinked starch of epichlorohydrin and crosslinked starch of phosphorus oxychloride.

26. The underground treatment fluid according to claim 25, further characterized in that the interlaced starch is a mixture of about 1: 1 by weight of crosslinked starch of epichlorohydrin and interlaced starch of phosphorus oxychloride.

27. The underground treatment fluid according to claim 26, further characterized in that the starch which is in the entangled starch of epichlorohydrin and the crosslinked starch of phosphorus oxychloride is waxy maize starch.

28. The underground treatment fluid according to any of claims 13-27, further characterized in that the interlaced starch is pregelatinized by spray drying. * m * í ^^ ~ t *? . > .. ^ J ^ -, ^. ^ ,,. ^ J e ^ .. ¡g- ^ ^ * > ^ *