MX2014009650A - Degradable fluid sealing compositions having an adjustable degradation rate and methods for use thereof. - Google Patents

Abstract

When performing subterranean treatment operations, it can be desirable to temporarily divert or block fluid flow by forming a degradable fluid seal. Methods for forming a degradable fluid seal can comprise: providing a sealing composition comprising : a degradable polymer, and a water-soluble material comprising a first portion and a second portion of rigid particulates, each portion having a sealing time and a particulate size distribution associated therewith, the particulate size distributions of the first portion and the second portion differing from one another; determining an amount of the first portion relative to the second portion needed to produce a degradable fluid seal having a desired sealing time that is different than that of the sealing time of either the first portion or the second portion; introducing the sealing composition into a subterranean formation; and allowing the sealing composition to form a degradable fluid seal in the subterranean formation.

Description

SEALING COMPOSITIONS OF DEGRADABLE FLUIDS THAT HAVE ADJUSTABLE DEGRADATION SPEED AND METHODS FOR USE FROM THE SAME FIELD OF THE INVENTION The present disclosure relates to methods and compositions for blocking and diverting fluids in underground formations, and, more specifically, to treat operations that form a seal of. temporary fluid in one. underground formation.

BACKGROUND OF THE INVENTION The fluids. of treatment can be used in a variety of underground operations. Such underground operations may include, without limitation, drilling operations, stimulation operations, production operations, remediation operations, sand control treatments and the like. As used herein, the terms "treat," "treatment," and "treat" refer to any underground operation that uses a fluid in conjunction with achieving a desired function and / or for a desired purpose. The use of these terms does not imply any particular action by him. treatment fluid. Illustrative processing operations may include, for example, fracturing operations, gravel packing operations, acidification treatments, scale elimination and dissolution, consolidation treatments, and the like.

When performing these and other underground treatment operations, it may sometimes be desirable to temporarily or permanently divert or block the flow of a fluid within at least a portion of the underground formation. Blocking or diversion of the fluid can be considered by itself a treatment operation. The blocking and diverting operations of illustrative fluids may include, without limitation, fluid loss control operations, elimination operations, compliance control operations, and the like. The fluid that is blocked or diverted can be a formation fluid that occurs natively in the underground formation, such as oil, gas, or water. In other cases, the fluid that is blocked or diverted may be an underground treatment fluid, which includes the types mentioned above. In some cases, the treatment fluids can be made to be self-diverted, such that they are directed to a desired location within the underground formation.

Providing control, effective fluid loss during underground treatment operations can be highly desirable. "Fluid loss," as used in the present, refers to unwanted migration or loss of fluids in an underground formation and / or a particle package. Fluid loss can be problematic in a number of underground operations including, for example, drilling operations, fracturing operations, acidification operations, gravel packing operations, repair operations, chemical treatment operations, cleaning operations, well drilling, and the like. In fracturing operations, for example, fluid loss in the formation matrix can sometimes result in incomplete fracture propagation.

The bypass agents can function in a similar manner with fluid loss control agents, but may involve a somewhat different approach. The diverting agents can be used to seal a portion of the underground formation. By sealing a portion of the underground formation, a treatment fluid can be diverted from a highly permeable portion of the subterranean formation to a portion of lower permeability, for example. Corking or sealing agents can similarly be used as diverting agents, except that they are generally used to seal the wellbore to provide zonal isolation.

When only a blockage or temporary diversion of fluids is desired, a fluid seal within a formation Underground can be removed to allow fluid flow to resume. In some cases, an external degrader can be introduced to the underground formation to eliminate the fluid seal. The external degrading agent can be introduced to the underground formation after the fluid seal is no longer. necessary (for example, after performing a treatment operation). The use of an external degrader in a separate cleaning operation can add the time and expense necessary to produce a fluid from the underground formation. In other cases, a fluid seal may comprise a substance that is natively unstable, such that the fluid seal degrades and / or dissolves over time to allow fluid flow to resume. When it depends on the natural degradation rate of a fluid seal, undesirable slow degradation can again be added for the time and expenses of production operations.

The gelled polymers can be used to form a fluid seal in underground operations. As used herein, a "gelled polymer" refers to a polymer in semi-solid form having at least a portion of its polymer chains crosslinked with one another by means of a crosslinking agent. A gelled polymer has a rheological production point. It must be understood in the following description that any reference to a gelled polymer refers to a polymer that is crosslinked. Crosslinked polyacrylamide, other acrylamide-containing polymers, and hydrolyzed or partially hydrolyzed variants thereof are illustrative examples of gelled polymers that can be used in underground operations.

Various modes of crosslinking can be used to form the crosslinks in a gelled polymer. The crosslinks may be in the form of a covalent bond or a non-covalent link interaction. They can be temporary or permanent. Chromium and other transition metal ions can be used to crosslink polymers containing acrylamide. Polymer gels formed using such crosslinking agents have proven to be unsuitable at higher temperatures (e.g., above about 80 ° C) due to uncontrolled crosslinking speeds (e.g., short gel times), agent precipitation of crosslinking, polymer degradation, and the like. In addition, chromium and certain other transition metal ions can have an undesirable environmental impact. Polymers containing acrylamide can also be crosslinked with polyalkylene imines and polyalkylene polyamines. Depending of the type and concentration of crosslinking agent used, the gel times and gel strengths of the gelled polymers can be affected.

The gelled acrylamide-containing polymers can be particularly effective for blocking and diverting fluids in lower permeability formations (e.g., formations having a permeability of about 0.1 dar'cy (D) or less). As the formation permeability increases, gels containing acrylamide-containing polymers can become less effective due to their reduced ability to block larger pore throats which may be characteristic of higher permeability formations. For example, above about 0.1 D, and particularly above about 0.5 D, gelled acrylamide-containing polymers may be less effective at blocking or diverting fluid flow at normal operating temperatures and pressures. To block these larger pore grooves in higher permeability formations, particle material can be added to polymers containing gelled acrylamide as a bridging agent.

SUMMARY OF THE INVENTION The present disclosure relates to methods and compositions for blocking and diverting fluids in underground formations, and, more specifically, to treating operations that form a temporary fluid seal in an underground formation.

In some embodiments, the present disclosure provides a method comprising: providing a sealing composition comprising: a degradable polymer, and a water soluble material, comprising a first portion of rigid particles and a second portion of rigid particles, each portion of rigid particles having a sealing time and a particle size distribution associated therewith, the particle size distributions of the first portion of rigid particles and the second portion of rigid particles differing from each other; determining an amount of the first portion of rigid particles relative to the second portion of rigid particles in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of rigid particles or the second portion of rigid particles; introducing the sealing composition into an underground formation; Y allow the sealing composition to form a degradable fluid seal in the underground formation.

In other embodiments, the present disclosure provides a method comprising: providing a sealing composition comprising: particles of a gelling degradable polymer, and a water soluble material comprising rigid particles having a sealing time and a size distribution of particle associated therewith, the particle size distribution of the water-soluble material which differs from that of a water-soluble material without equal glueing; determining a particle size distribution of the rigid particles necessary to produce a degradable fluid seal having a desired sealing time; introducing the sealing composition into an underground formation; forming a degradable fluid seal in the underground formation of the sealing composition; performing a treatment operation in the underground formation while the degradable fluid seal is intact; and allow the degradable fluid seal to degrade.

In yet other embodiments, the present disclosure provides a method comprising: providing a plurality of degradable polymer particles gelled; provide a first portion of a soluble material in water and a second portion of a water soluble material, each portion comprises rigid particles and each portion has a sealing time and a particle size distribution associated therewith, the particle size distributions differing. one from the other; mixing the first portion of the water-soluble material and the second portion of the water-soluble material with the plurality of gelled degradable polymer particles, thereby forming a sealing composition; determining an amount of the first portion of the water-soluble material relative to the second portion of the water-soluble material in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of the water-soluble material or the second portion of the water-soluble material; and introducing the sealing composition into an underground formation to form a degradable fluid seal therein.

The features and advantages of the present disclosure will be readily apparent to one having ordinary skill in the art upon reading the description of the preferred embodiments that follow.

BRIEF DESCRIPTION OF THE FIGURES The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive modalities. The subject matter described is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to one who has ordinary experience in the art and who has the benefit of this description.

FIGURE 1 shows a fluid penetration plot illustrative of a treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 14.3% in. weight of the polyvinyl alcohol particles have a particle size < 125 microns and 85.7% by weight of the polyvinyl alcohol particles have a particle size between 125 microns and 355 microns.

FIGURE 2 shows a fluid penetration graph illustrative of a treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 18.6% by weight of the polyvinyl alcohol particles have a particle size < 125 microns and 81.4% by weight of the polyvinyl alcohol particles have a particle size between 125 microns and 355 microns.

FIGURE 3 shows a fluid flow chart illustrative of a treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 21.4% by weight of the polyvinyl alcohol particles have a particle size < 125 microns and 78.6% by weight of the polyvinyl alcohol particles have a particle size between 125 microns and 355 microns.

FIGURE 4 shows a fluid penetration graph illustrative of a treatment fluid containing crosslinked polyacrylamide particles and polyvinyl alcohol particles in which 28.6% by weight of the polyvinyl alcohol particles have a particle size < 125 microns and 71.4% by weight of the polyvinyl alcohol particles have a particle size between 125 microns and 355 microns.

DETAILED DESCRIPTION OF THE INVENTION The present disclosure relates to methods and compositions for blocking and diverting fluids in underground formations, and, more specifically, to treating operations that form a temporary fluid seal in an underground formation.

As previously described, the degradable polymers gelled can be used for the blocking and diversion of fluids in an underground formation. In low permeability formations, the gelled polymer alone may be suitable for this purpose. In higher permeability formations, however, the particles of a bridging agent can be used in combination with the gelled polymer so that the broader pore grooves in the formation can be sealed. The bridging agent particles may comprise a rigid material. As used herein, the term "rigid" refers to a shape of particles that is substantially non-flexible and substantially maintains its shape when subjected to tension. Rigid particles suitable for use in the present embodiments are described in more detail hereinafter.

Not only can rigid bridging particles desirably facilitate the use of gelled polymers for fluid deflection and sealing applications in the upper ground permeability formations, but the presence of the bridging particles themselves can alter the rate of degradation of a seal. of degradable fluid formed thereof. In the case of crosslinked polyacrylamide such as gelled polymer and polyvinyl alcohol as rigid bridge particles, this The result is particularly surprising, since an aqueous polyvinyl alcohol solution is non-buffering and produces a pH range (eg, -5.5 - 7.5) which by itself does not. appreciable impact on the rate of degradation of the crosslinked polyacrylamide. Unless otherwise specified herein, a fluid seal will be considered to degrade when it is no longer impervious to a fluid of interest. After a failure of the fluid seal, the seal may further experience degradation and / or dissolution, as described below. A sealing time of the fluid seal may be a function of its rate of degradation, which may be a function of, among other things, the rate of degradation of the gelled polymer, the dissolution or rate of degradation of the rigid bridging particles, hydrophobicity or hydrophilicity of rigid bridging particles and / or gelled polymer, p'H and temperature conditions, and the presence of other materials that can accelerate or reduce the rate of degradation. As used herein, the term "sealing time" refers to a period of time during which a seal is substantially impervious to a fluid.

Surprisingly it has been found that the rate of degradation of a fluid seal comprising a polymer degraded gelling agent can be further altered by using rigid bridging agent particles having a different particle size distribution which makes it a similar unglued bridging agent. As used herein, the term "unglued" refers to the distribution of native particle size obtained when a material is synthesized. By classifying a sample of rigid bridging agent particles, the rate of degradation of a fluid seal formed therefrom can be desirably altered compared to that obtained using a comparable amount of unglued rigid bridging agent particles. The rigid bridging agent particles having two or more different particle size ranges can also be combined to create a custom particle size distribution suitable to produce a desired degradation rate. By adjusting the relative amounts of the two or more different relative particle size ranges to each other, the degradation speed of the fluid seal can also be altered. Although the use of rigid bridging agent particles in a degradable fluid seal may be particularly advantageous in the upper underground permeability formations (e.g., around 0.5 D or greater), it must be recognized that the above benefits can also be realized in underground formations that have a lower permeability.

The ability to alter the rate of degradation of the fluid seal can be especially beneficial when it is desired to resume fluid flow or complete the diversion of fluids before the degradation of the natural fluid seal occurs. In addition, by 'altering the rate of degradation of the fluid seal from within, instead of using an external degradant in a cleaning fluid, the cost of the goods can be minimized and the time lost during cleaning operations can be avoided. . Therefore, by keeping the fluid seal intact only for as long as it is functionally necessary, the formation can be returned to production more quickly, thus allowing savings of beneficial costs to be made.

More specifically, it has been found that the combination of the gelled degradable polymer particles and the rigid particles of a water-soluble material can form the seals of degradable fluid whose rate of degradation can be altered by varying the size distribution of the rigid particles. . As used herein, the term "water-soluble" refers to a material that is itself soluble in water or becomes soluble in water upon undergoing chemical transformation.

No particular degree of water solubility is implied by the term "water soluble." The degradable fluid seals formed from the combination of gelled degradable polymer particles and rigid particles of a water-soluble material can be particularly advantageous for underground operations, since the fluid seals can be self-cleaning. That is to say, . fluid seals are not believed to leave a residue (damage) in the underground formation in the long term. Without being bound by theory or mechanism, it is believed that the degradable fluid seals described herein may begin to fail due to the dissolution of the water-soluble material. Either simultaneously with or subsequent to the dissolution of the water soluble material, the degradable polymer particles can degrade to form a substantially water-soluble material. Therefore, both components of the degradable fluid seal can become soluble in time. It should be noted that the degradation of the gelled degradable polymer does not necessarily have to take place by chemical degradation. For example, in some cases, degradation can. occur by physical or enzymatic (biological) transformations. In some cases, the degraded gelled polymer may simply become soluble in a fluid or erode over time such that the seal is stir gradually. Unless otherwise specified herein, the mechanism by which the degraded gelled polymer degrades can occur in any way. In the case of gelled polyacrylamide particles, degradation can occur more rapidly at alkaline pH values, but it can also be a component of solubilization or erosion to its degradation as well.

Particularly in embodiments in which gelled polyacrylamide particles are used, further control over the rate of degradation of the degradable fluid seal can be realized by adjusting the pH of a treatment fluid used to introduce the particles into an underground formation. For example, if more rapid degradation of the degradable fluid seal that can be made through altering the size distribution of the water soluble particles is desired, the pH of the treatment fluid can be increased. Specifically, in some embodiments, the pH of the treatment fluid can be increased using calcium carbonate or a comparable base, which can result in more rapid degradation of the polyacrylamide particles. Conversely, in embodiments in which the gelled polyacrylamide particles are used, if the slower degradation of the degradable fluid seal is desired, a treatment fluid having a pH lower can be used. Other types of materials may have different degradation characteristics. For example, esters can degrade more rapidly at any high or low pH, but degrade very slowly at intermediate pH (e.g., a pH of about 3 to about 6). In some embodiments, calcium carbonate particles or a comparable base can be included in the degradable fluid seal, such that a localized alkaline environment is formed to promote degradation, particularly by a fluid seal comprising gelled polyacrylamide particles. In some embodiments, the base particles may comprise the water-soluble material. In other embodiments, the base particles can be used in conjunction with another water-soluble material that can be degraded with a base.

In various embodiments, the sealing compositions described herein may comprise a degradable polymer and a water-soluble material comprising rigid particles, wherein the size distribution of the water-soluble material differs from that of a water-soluble material without glueing the same . As used herein, a "water-soluble material without equal glue" refers to a water-soluble material that has a substantially identical chemical composition, but a size distribution that differs from that of a classified water soluble material. That is, a classified water soluble material has a size distribution that differs considerably from that of a water soluble material as synthesized. In some embodiments, rigid particles having two or more different particle size ranges can be combined to form a water-soluble material having a particle size distribution that differs from that of the unglueable water soluble material. That is, in some embodiments, two or more portions of rigid particles, each having particle size distributions that differ from each other, may comprise the water-soluble material.

As one of ordinary skill in the art will recognize, there may be a distribution of particle sizes in a material, where the particle sizes can be grouped around a most probable value (ie, the mode value). In the absence of intervention factors, the particle size distribution can approximate a Gaussian distribution. However, as one of ordinary experience in the art will recognize further, the particle size distribution in a material is more frequently non-Gaussian, with the value of the way it is skewed to one side of the. value of the median, often with a tail in the distribution curve that favors larger particle sizes. Various techniques that will be familiar to one of ordinary skill in the art can be used to separate particles having different size ranges from one another (eg, sieving). In general, the classification of the water-soluble material used in the present embodiments can occur through any separation technique. of particle size, known or currently unknown.

When using classified particles, the classified particles can themselves have a particle size distribution. The particles that have two or more different intervals. of particle size can be combined with each other to produce a sample that has yet another particle size distribution. In general, when particles having different particle size ranges are combined with one another, the resulting sample will have a different particle size distribution than that of an unglued material of the same size. In addition, the particle size distribution of the combined sample can be further altered by using different quantities of each classified particle. In some modalities, there may be two or more local maxima within the particle size distribution of the combined sample. Two or more Local maxima can be observed if the particle size ranges are further apart from each other and / or if there are significant quantities of both particle size ranges present in the combined sample. For example, the particle size distribution of the combined sample can be bimodal, trimodal, or have a larger modality. In other modalities, there may be a single maximum within the size, particle distribution of the combined sample. A single maximum can be observed in the combined sample of classified particles if the particle size ranges are closer to one another, particularly overlap, and / or if there is a relatively small amount of at least one of the particles relative to the other . For example, the particle size distribution chart of the combined sample may show a vertical drop or as a characteristic, that is, not present in the particle size distribution chart of one of its components.

In some embodiments, the water soluble material used herein may comprise at least two different particle size ranges. Accordingly, the particle size distribution of the water-soluble material may differ from that of a water-soluble material without glueing the same. In general, the combination of two or more Different ranges of particle size of the water soluble material can produce a particle size distribution that has any size or shape. In some embodiments, the particle size distribution of the water-soluble material can have two or more local maxima. In other embodiments, the particle size distribution of the water-soluble material can have a unique maximum. In some embodiments, the particle size distribution of the water-soluble material can differ considerably from the particle size distribution of one or more of its components.

In some embodiments, the degradable polymer may comprise particles of a gelled degradable polymer. In some embodiments, the degradable polymer can be crosslinked. For example, in some embodiments, the gelled degradable polymer may comprise at least one cross-linked polymer such as, for example, a cross-linked polyacrylamide, a cross-linked polymethacrylamide, any hydrolyzed or partially hydrolyzed variant thereof, any copolymer thereof, any derived from them, and any combination thereof. As used herein, a partially hydrolyzed poly (meth) acrylamide will have at least a portion of its monomer units of acid-hydrolyzed (meth) acrylamide. (met) acrylic. Any variant of partially hydrolyzed polymer that remains gellable can be used in the present embodiments. In some embodiments, between about 1% and about 30% of the (meth) acrylamide monomer units can be hydrolyzed. In alternative embodiments, the non-particle versions of these degradable polymers can also be used. Techniques for preparing gelled polyacrylamide particles and other gelled polymers are described in detail in commonly owned United States of America Patent Application 13 / 190,509, filed July 26, 2011, which is incorporated herein by reference in its whole. In some embodiments, the particles can be produced by any combination of techniques including, for example, cutting; extruding through a die, filter, or the like; mix i high speed; homogenize; to combine; emulsify; and similar.

Examples of polymers containing acrylamide and methacrylamide suitable for use in the present embodiments are described in commonly owned US Pat. No. 6,176,315, which is incorporated herein by reference in its entirety. In some or other embodiments, suitable gelled degradable polymers can include degradable gelled polymers of stimuli. such as those described in commonly owned U.S. Patent 7,306,040, which is incorporated herein by reference in its entirety.

In some embodiments, the gelled degradable polymers used herein may include ethylenically unsaturated monomers such as, for example, ionizable monomers (e.g., 1-N, -diethylaminoethyl methacrylate, and the like); diallyldimethylammonium chloride; 2-acrylamido-2-methyl propane sulfonate; . acrylic acid; allylic monomers (for example, diallyl phthalate, diallyl maleate, allyl diglycol carbonate, and the like); vinyl formate; vinyl acetate; vinyl propionate; vinyl butyrate; crotonic acid; Itaconic acid; acrylamide; methacrylamide; methacrylonitrile; acrolein; methyl vinyl ether; ethyl vinyl ether; vinyl ketone; ethyl vinyl ketone; allyl acetate; allyl propionate; diethyl maleate; any derivative thereof; and any copolymer thereof.

In some embodiments, a crosslinking agent used to form the gelled degradable polymer may comprise an organic crosslinking agent. In some embodiments, the rate of degradation of the gelled degradable polymer can be altered by changing the identity and / or concentration of the crosslinking agent. Consequently, the rate of degradation of the fluid seal degradable can be further adjusted by altering the identity and / or concentration of the crosslinking agent in the gelled degradable polymer. · In some embodiments, the crosslinking agent itself can be degradable. Suitable degradable crosslinking agents may comprise degradable functional groups such as, for example, esters, phosphate esters, amides, acetals, ketals, orthoesters, carbonates, anhydrides, silyl ethers, alkene oxides, ethers, imines, ether esters , ester amides, ester urethanes, carbonate urethanes, amino acids, any derivatives thereof, or any combination thereof. The choice of the degradable functional groups used in the degradable crosslinking agent can be determined by the pH and temperature conditions under which the degradable fluid seal will be used, for example.

The size of the gelled degradable polymer particles is not believed to be particularly limited. In some embodiments, the gelled degradable polymer particles may vary between about 1 micron and about 10 mm in size. In other embodiments, the gelled degradable polymer particles may vary between about 10 microns and about 1 mm in size. In still other modulations, the gelled degradable polymer particles may vary between about 50 microns and about 500 microns in size. In some embodiments, the gelled degradable polymer particles may be at least about 50 microns in size, or at least about 100 microns in size in other embodiments.

In general, the rigid particles of any water soluble material can be used in the present embodiments. Both inorganic and organic water soluble materials can be used. Rigid particles are not particularly limited in shape, which may include various non-limiting forms such as, for example, platelets, chips, flakes, tapes, bars, strips, spheroids, toroids, pellets, tablets, needles, powders and / or similar. The choice of a suitable water-soluble material can be dictated by operational needs including, for example, dissolution rate, underground formation temperature and pH, availability of different ranges of particle size, chemical compatibility, environmental concerns, and the like. For example, if the water solubility of the water-soluble material is too great, premature failures of the degradable fluid seal may occur. Likewise, if the solubility in water is too low, the water soluble material can not sufficiently alter the rate of degradation of the seal of water. degradable fluid over that of its rate of natural degradation, even if the classified particles are used.

In some embodiments, a suitable water soluble material may comprise a water soluble polymer. Water soluble polymers that can form rigid particles can include, for example, polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, acetyl cellulose, hydroxyethyl cellulose, shellac, chitosan, chitin. , dextran, guar, xanthan, starch, scleroglucans, a diutane, poly (vinyl pyrrolidone), polyacrylamide, polyacrylic acid, poly (diallyldimethylammonium chloride), poly (ethylene glycol), poly (ethylene oxide), polylysine, polymethacrylamide, acid polymethacrylic, poly (vinylamine), any derivative thereof, any copolymer thereof, and any combination thereof. In some embodiments, the preceding polymers can be crosslinked to alter their rate of dissolution and / or their hydrophobicity. The crosslinking can also improve the rigidity of particles formed thereof. In other embodiments, fish eyes may be formed from the foregoing polymers to alter their rate of dissolution. The derivation and the degree of functionalization can also impact the water solubility and velocity of polymer dissolution in some cases. In some embodiments, the polymer can not become soluble in water until after the hydrolysis of at least a portion of its functional groups. The behavior can be seen in methyl cellulose, ethyl cellulose, and acetyl cellulose, for example.

In some embodiments, the water soluble material may comprise polyvinyl alcohol. The polyvinyl alcohol may be particularly advantageous for use in the present embodiments. The polyvinyl alcohol can be produced by at least partial hydrolysis of polyvinyl acetate or one as an acylated polymer. In some or other embodiments, polyvinyl acetate having a sufficient degree of hydrolysis to be at least partially soluble in water can be used. A major advantage of polyvinyl alcohol for use in the present embodiments is that it is non-toxic and biodegradable, which facilitates its use in the medical and textile industries, for example. Polyvinyl alcohol can be obtained in many forms including, for example, fibers, sheets, granules, drops, powders, and the like. In addition, polyvinyl alcohol can exist as an amorphous solid in an aqueous environment or becomes completely soluble depending on the solution conditions. Among the factors that can affect the rate of dissolution they include the degree of hydrolysis, the polymer molecular weight, crystallinity, polymer concentration, ionic strength, and the like.

In alternative embodiments, a degradable polymer can form rigid particles that can be used in place of rigid water-soluble particles. Degradation can occur by chemical, physical, or enzymatic means (biological), for example. Degradable polymers that can form rigid particles suitable for use in these alternative embodiments include, for example, polysaccharides (e.g., dextran, cellulose, guar, and derivatives thereof), chitin, proteins, aliphatic polyesters [e.g., poly (hydroxy alkanoates)], polyglycolic acid and other poly (glycolides), polylactic acid, and other poly (lactides) ), polyacrylamide and other polyacrylates, polymethacrylamide and other polymethacrylates, polyvinyl alcohol, poly (-hydroxy alkanoates) [e.g., ??? (β-hydroxy butyrate) and poly (-hydroxybutyrates-co ^ -hydroxyvalerate)], poly ' (hydroxybutyrates), poly (? -hydroxy alkanoates) [e.g., poly (β-propiolactone) and poly (e-caprolactone], poly (alkylene dicarboxylates) [e.g., poly (ethylene succinate) and poly (butylene succinate)] , poly (hydroxy ester ethers), poly (anhydrides) [eg, poly (adipic anhydride), .poly (suberic anhydride), poly (sebacic anhydride), poly (dodecanedioic anhydride), poly (maleic anhydride) and. poly (benzoic anhydride)], polycarbonates (for example, trimethylene carbonate), poly (orthoesters),. poly (amino acids), poly (ethylene oxides), poly (ether esters), ester polyamides, polyamides, poly (dioxepan-2-one), and polyphosphazenes. The combinations of these polymers and others can also be used in various modalities. In various embodiments, the homopolymers or copolymers of these various polymers can be used. The copolymers may include random, block, graft, and / or star copolymers in various embodiments.

Speed . degradation of a degradable polymer may depend at least in part on its skeleton structure. The degradability of a degradable polymer can be due to a chemical change, for example, which destroys the polymer structure or changes the solubility of the polymer such that it becomes more soluble than the precursor polymer. For example, the presence of hydrolyzable and / or oxidizable ligatures in the backbone can make a polymer degradable in one or more of the above ways. The rates at which the polymers degrade may depend on factors such as, for example, the unit of repetition, composition, sequence, length, molecular geometry, molecular weight, morphology (e.g. crystallinity, particle size, and the like), hydrophilicity / hydrophobicity, and surface area. In addition, exposure to conditions such as for example, temperature, humidity, oxygen, microorganisms, enzymes, pH, and the like can alter the rate of degradation. Knowing how the degradation rate is influenced by the polymer structure, one of ordinary skill in the art will be able to choose an appropriate degradable polymer for a given application. It should be noted that the above factors can also influence the rate of degradation of the gelled degradable polymers used in the present embodiments.

In still other alternative embodiments, a dehydrated compound may comprise the rigid particles. A dehydrated compound, particularly a dehydrated borate, can degrade over time as the dehydrated compound re-hydrates and becomes soluble. Exemplary dehydrated borates may include, for example, anhydrous sodium tetraborate (anhydrous borax) and anhydrous boric acid. These anhydrous borates and others are only slightly soluble in water. However, after exposure to underground temperatures, they can rehydrate slowly over time and become considerably more soluble. As a result of the increased solubility, the particles of anhydrous borate can degrade upon becoming soluble. The time required for anhydrous borates to become soluble can vary from about 8 hours to about 72 hours, depending on the temperature of the underground zone in which they are placed.

In modalities in one. Non-natural particle size distribution of rigid particles is used, the average particle size can vary between about 1 micron and about 5 mm. In some embodiments, the average particle size of the rigid particles may vary between about 10 microns and about 1 mm. In some embodiments, the average particle size of the rigid particles may vary between about 50 microns and about 750 microns. In some embodiments, the average particle size of the rigid particles may vary between about 100 microns and about 500 microns. In some embodiments, the particle size distribution of the rigid particles may fall within about 5% of the average particle size. In some embodiments, the particle size distribution of the rigid particles may fall within about 10% of the average particle size. In some embodiments, the particle size distribution of the rigid particles may fall within about 15% of the particle size medium. In some embodiments, the particle size distribution of the rigid particles may fall within about 20% of the average particle size. In some embodiments, the particle size distribution of the rigid particles may fall within about 25% of the average particle size. In some embodiments, the particle size distribution of the rigid particles may fall within about 30% of the average particle size.

In embodiments in which two or more portions of rigid particles combine to produce a "random" particle size distribution, the particles may again vary between about 1 micron and about 5 mm in size. In some embodiments, an average size of a first portion of rigid particles may be about 50 microns in size or less, and a second portion of rigid particles may be about 50 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 50 microns in size or less, and a second portion of rigid particles may be about 100 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 50 microns in size or less, and a second portion of Rigid particles can be around 150 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 50 microns in size or less, and a second portion of rigid particles may be about 200 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 100 microns in size or less, and a second portion of rigid particles may be about 100 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 100 microns in size or less, and a second portion of rigid particles may be about 150 microns in size or greater. In some embodiments, an average size of a first portion of rigid particles may be about 100 microns in size or less, and a second portion of rigid particles may be about 200 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 100 microns in size or less, and a second portion of rigid particles may be about 250 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 150 microns in size or less, and a second portion of Rigid particles can be around 150 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 150 microns in size or less, and a second portion of rigid particles may be about 200 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 150 microns in size or less, and a second portion of rigid particles may be about 250 microns in size or larger. In some embodiments, an average size of a first portion of rigid particles may be about 150 microns in size or less, and a second portion of rigid particles may be about 300 microns in size or larger.

In some embodiments, the first portion of rigid particles may have a smaller average particle size than does the second portion of rigid particles. In some embodiments, the first portion of rigid particles may have no particular lower limit in particle size, while the second portion of rigid particles may have a different upper and lower particle size. In some embodiments, the first portion of rigid particles may be about 50 microns in size or less. In some embodiments, the first portion of rigid particles It can be around 75 microns in size or less. In some embodiments, the first portion of rigid particles may be about 100 microns in size or less. In some embodiments, the first portion of rigid particles may be about 125 microns in size or less. In some embodiments, the first portion of rigid particles may be about 150 microns in size or less. In some embodiments, the first portion of rigid particles may be about 175 microns in size or less. In some embodiments, the first portion of rigid particles may be around 200 microns in size or less. In some embodiments, the second portion of rigid particles may vary between about 100 microns and about 500 microns in size. In some embodiments, the second portion of rigid particles may vary between about 150 microns and about 500 microns in size. In some embodiments, the second portion of rigid particles may vary between about 200 microns and about 500 microns in size. In some embodiments, the second portion of rigid particles may vary between about 250 microns and about 500 microns in size.

In various embodiments, the first portion of rigid particles and the second portion of rigid particles may be present, in a ratio ranging from around 1:19 and around 19: 1. In some embodiments, the first portion of rigid particles may comprise at least about 10% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 15% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 20% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 25% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 30% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 35% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 40% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 45% of the total rigid particles. In some embodiments, the first portion of rigid particles may comprise at least about 50% of the total rigid particles.

In some embodiments, the sealing compositions described above can be used in various underground treatment operations. Such operations may vary without limitation. The functions performed by the sealing compositions in underground operations may include, for example, loss of control fluid, diversion of fluids, control of compliance, and the like.

In some embodiments, the methods may comprise: providing a sealing composition comprising: a degradable polymer, and a water-soluble material comprising a first portion of rigid particles and a second portion of rigid particles, each portion of rigid particles having a sealing time and a particle size distribution associated therewith, the particle size distributions of the first portion of rigid particles and the second portion of rigid particles differing from each other; determining an amount of the first portion of rigid particles relative to the second portion of rigid particles in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of rigid particles or the second portion of rigid particles; introduce the sealing composition in an underground formation; and allowing the sealing composition to form a degradable fluid seal in the underground formation. In some embodiments, the methods may further comprise: performing a treatment operation in the underground formation while the degradable fluid seal is intact; and allow the degradable fluid seal to degrade.

In some embodiments, the methods may comprise: providing a sealing composition comprising: particles of a gelled degradable polymer, and a water soluble material comprising rigid particles having a sealing time and a particle size distribution associated with the same, the particle size distribution of the water-soluble material that differs from that of a water-soluble material without equal glueing; determining a particle size distribution of the rigid particles necessary to produce a degradable fluid seal having a desired sealing time; introducing the sealing composition into an underground formation; forming a degradable fluid seal in the underground formation of the sealing composition; perform a treatment operation in the underground formation while the degradable fluid seal is intact; and allow the degradable fluid seal to degrade.

In alternative embodiments of the above methods, a degradable polymer or an anhydrous borate may comprise the rigid particles instead of a water-soluble material.

In some embodiments, the sealing compositions may be introduced into an underground formation in a treatment fluid. In some embodiments, the treatment fluids may comprise an aqueous carrier fluid or a carrier fluid based on water. Suitable aqueous carrier fluids may include, for example, fresh water, salt water, brine (saturated salt water), sea water, produced water (that is, water of underground formation brought to the surface), surface water (eg, water). example, lake or river water), and return flow water (that is, water placed in an underground formation and then returned to the surface). In some embodiments, the treatment fluid may be gelled in order to better support the transport of the particles in the underground formation.

Depending on the type of underground formation being treated and the intended type of treatment operation that is carried out, other components may optionally be included in the treatment fluid. Such components may include, for example, salts, pH control additives, surfactants, foaming agents, antifoaming agents, switches, biocides, cross-linking agents, additional fluid loss control agents, stabilizers, chelating agents, scale inhibitors, gases, mutual solvents, particles, corrosion inhibitors, oxidizing agents, reducing agents, antioxidants, relative permeability modifiers, viscosification agents, support particles, gravel particles, scale inhibitors, emulsifying agents, de-emulsifying agents, iron control agents, clay control agents, flocculants, scrubbers, lubricants, friction reducers, viscosifiers, agents of charge, hydrate inhibitors, consolidation agents, any combination thereof, and the like. A person having ordinary skill in the art, with the benefit of this disclosure, will recognize when such optional additives must be included in a treatment fluid, as well as the appropriate amounts to be included.

The methods described herein can be used in many different types of underground treatment operations. Such operations may include, but are not limited to, acidification operations, scale inhibition operations, water blocking operations, clay stabilizing operations, biocide operations, fracturing operations, fracturing-packing, and gravel packing operations.

In some embodiments, a treatment fluid used to introduce the sealing compositions into: an underground formation may have a basic pH. For example, a basic compound may be present in the treatment fluid. As one of ordinary skill in the art will recognize, the inclusion of a basic compound in the treatment fluid can promote the degradation of a degradable polymer, particularly a poly (meth) acrylamide. Suitable basic compounds that can be used to accelerate the degradation rate of a poly (meth) acrylamide can include, for example, calcium carbonate, calcium bicarbonate, calcium oxide, magnesium oxide, magnesium hydroxide, and the like. In some or other embodiments, the treatment fluid may contain an oxidant, which may also accelerate the rate of degradation of a poly (meth) acrylamide.

Also, in some embodiments, a treatment fluid used to introduce the sealing compositions into an underground formation may also contain an additive that accelerates the solubilization or degradation of the rigid particles. Suitable additives may include acids, acid-generating compounds (e.g., esters and orthoesters), bases, base-generating compounds, enzymes, oxidizers, solvents, oil, chelating agents, surfactants, azo compounds, buffers, catalysts, compounds that increase solubility, and the like. In other embodiments, the treatment fluids may also contain an additive that slows down the solubilization or degradation of the rigid particles. For example, for rigid particles that. degrade by oxidation, the treatment fluid may contain an antioxidant.

In some embodiments, the sealing compositions themselves may contain additional solid particles that accelerate the degradation rate of the degraded gelled polymer and / or the solubilization or degradation of the rigid particles. As previously described, the inclusion of other solid particles within the degradable fluid seal formed from the sealing compositions can create a localized chemical and / or physical environment that accelerates degradation or solubilization. Any of the above additives may be included as additional solid particles in the degradable fluid seals described herein.

Generally, sealing compositions can be introduced in any type of underground formation. In addition, the underground formation can have any permeability. However, as noted above, the Sealing compositions can be particularly useful in high permeability formations. In some embodiments, the underground formation may have a permeability of at least about 0.5 Darcy (D). In other embodiments, the underground formation may have a permeability of at least about 1 D, or at least about 5 D, or at least about 10 D, or at least about 50 D, or at least about 100 D In some embodiments, a high permeability underground formation may have at least some pore grooves in this having a nominal opening size of at least about 20 μta.

In some embodiments, the seal of degradable fluid formed in the underground formation can be dissolved in a fluid present therein. The fluid seal solution can occur during or after degradation of the degradable fluid seal is carried out. For example, partial dissolution of the degradable fluid seal may occur over time when the fluid seal fails. After the fluid flow continues in the formation, the failed seal may persist for some period of time but it returns. soluble after that. In some embodiments, the degradable polymer of the fluid seal may become soluble, leading to failure of the fluid seal, followed by solubilization of the particles rigid after that. In other embodiments, the rigid particles may be at least partially solubilized or degraded, leading to failure of the fluid seal, followed by degradation and solubilization of the gelled degradable polymer and solubilization of the remaining rigid particles thereafter. In some embodiments, the previous degradation and dissolution processes may occur concurrently.

In some embodiments, a seal time of the degradable fluid seal can be altered by changing the amount of the rigid particles having at least two different relative particle size ranges from one another. That is, the rate of degradation of the degradable fluid seal can be altered by changing the size distribution of the rigid particles, which can be realized by mixing two or more rigidly differentially classified particles with one another. Taking into account the benefit of the present disclosure, one having ordinary skill in the art will be able to determine an appropriate combination of rigid sized particles to produce a desired sealing time for a degradable fluid seal within an underground formation.

In some embodiments, the methods may comprise: providing a plurality of polymer particles degradable gelled; providing a first portion of a water soluble material and a second portion of a water soluble material, each portion comprising rigid particles and each portion having a sealing time and a particle size distribution associated therewith, the size distributions of particle differ from one another; mixing the first portion of the water-soluble material and the second portion of the water-soluble material with the plurality of gelled degradable polymer particles, thereby forming a sealing composition; determining an amount of the first portion of the water-soluble material relative to the second portion of the water-soluble material in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of the water-soluble material or the second portion of the water-soluble material; and introducing the sealing composition into an underground formation to form a degradable fluid seal in this. In some embodiments, the methods may further comprise: choosing the particle size distributions of the first portion of the water-soluble material and the second portion of the water-soluble material necessary to produce a degradable fluid seal having a desired sealing time .

To facilitate a better understanding of the present invention, the following examples of preferred embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES EXAMPLE 1: Degradation rates of degradable fluid seals containing chopped crosslinked polyacrylamide particles and polyvinyl alcohol particles.

A combination of chopped cross-linked polyacrylamide particles and polyvinyl alcohol particles was used to form a degradable fluid seal on a 90 micron (2.5"diameter) Aloxite disc.The fluid penetration time of the degradable fluid seal was evaluated In a high-temperature, high-pressure flow cell, the test was carried out at a differential pressure of 35.15 kg / cm2 (500 psi) and a temperature of 93.3 ° C (200 ° F). The degradable fluid seal (filter cake) was generated for 36 minutes at room temperature under a differential pressure of 35.15 kg / cm2 (500 psi) as a treatment fluid containing the particles flows through the Aloxite disc. Fluid loss was recorded with a graduated cylinder until the filter cake was blown completely.

The polyacrylamide became degradable by incorporating a cleavage link in the polymer backbone in the form of a degradable crosslinking agent. The degradable polyacrylamide was prepared by polymerizing the acrylamide with a polyethylene oxide / diacrylate oligomer having a molecular weight of 258. The polymerization reaction was carried out at room temperature using potassium persulfate as an initiator in the presence of N, N, 1'-tetramethylethylenediamine. The resulting polymer gel was then bitten into 40 ppt PAC-R ™ filtration control agent (carboxylmethyl cellulose, commercially available from Halliburton Energy Services) when using a Silverson mixer. It operates at 6000 RPM for 1 min. The average size of the chopped particles was around 100 microns. The BARRACARB 150® bridging agent (CaC03, commercially available from Halliburton Energ Services) was added in the chopped gels to increase the rate of degradation.

The polyvinyl alcohol particles were CELVOL ™ 125, a highly hydrolyzed polyvinyl alcohol (99.3%) available from Celanese Corp. Two different particle size ranges were used, as obtained from milling and sieve-based size separation: 1) < 125 microns and 2) 125 microns - 355 microns. Various composition ratios of these classified particles of polyvinyl alcohol were used as set forth below.

A first treatment fluid was prepared in the following composition: 10% of degradable polyacrylamide gel particles in 400 mL of 40 ppt PAC-R ™ filtration control additive, also contains 0.05% by weight of BARRACARB 150® and 1.75% by weight of CELVOL ™ 125 additive. In this case, 14.3% by weight of the CELVOL ™ 125 additive had a particle size < 125 microns and 85.7% by weight had a particle size between 125 microns and 355 microns. FIGURE 1 shows a fluid penetration plot illustrative of a treatment fluid containing crosslinked polyacrylamide particles and polyvinyl alcohol particles in which 14.3% by weight of the polyvinyl alcohol particles had a particle size < 125 microns and 85.7% by weight of the polyvinyl alcohol particles had a particle size between 125 microns and 355 microns. As shown in FIGURE 1, after the initial formation period at room temperature, the fluid-degradable seal remained intact for more than 5 hours at 93.3 ° C (200 ° F) under a differential pressure of 35.15 kg / cm2 (500 psi).

A second treatment fluid was prepared in the following composition: 10% of degradable polyacrylamide gel particles in 400 mL of 40 ppt PAC-R ™ filtration control additive also containing 0.05% by weight of BARRACARB 150® and 1.75% by weight of CELVOL ™ 125 additive. in this case, 18.6% by weight of the CELVOL ™ 125 additive had a particle size < 125 microns and 81.4% by weight had a particle size between G25 microns and 355 microns. FIGURE 2 shows a graph of fluid penetration illustrative of a treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 18.6% by weight of the polyvinyl alcohol particles had a particle size < 125 microns and 81.4% by weight of the polyvinyl alcohol particles had a particle size between 125 microns and 355 microns. As shown in FIGURE 2, after the initial formation period at room temperature, the degradable fluid seal remained intact for about 140 minutes at 93.3 ° C (200 ° F) under a differential pressure of 35..15 kg. / cm2 (500 psi). After the fluid penetration occurred, the remaining degradable fluid seal was removed from the flow cell and placed in a glass bottle with 250 mL of 40 ppt PAC-R ™ filtration control additive, which was heated subsequently at 93.3 ° C (200 ° F). Within 15 hours, the stamp of degradable fluid had been completely removed as the remaining polyacrylamide gel particles were degraded and the polyvinyl alcohol particles were solubilized.

A third treatment fluid was prepared in the following composition: 10% polyacrylamide gel particles in 400 mL of 40 ppt of PAC-R ™ filtration control additive, also containing 0.05% by weight of BARRACARB 150® and 1.75 % by weight of CELVOL ™ 125 additive. In this case, 21.4% by weight of the CELVOL ™ 125 additive had a particle size < 125 microns and 78.6% by weight had a particle size between 125 microns and 355 microns. FIGURE 3 shows a fluid penetration plot illustrative of a treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 21.4% by weight of the polyvinyl alcohol particles had a particle size < 125 microns and 78.6% by weight of the polyvinyl alcohol particles had a particle size between 125 microns and 355 microns. As shown in FIGURE 3, after the initial formation period at room temperature, the degradable fluid seal remained intact for about 80 minutes at 93.3 ° C (200 ° F) under a differential pressure of 35.15 kg / cm2 ( 500 psi).

A fourth treatment fluid was prepared in the following composition: 10% polyacrylamide gel particles in 400 mL of 40 ppt of PAC-R ™ filtration control additive, also containing 0.05% by weight of BARRACARES 150® and 1.75 % by weight of CELVOL ™ 125 additive. In this case, 28.6% by weight of the CELVOL ™ 125 additive had a particle size < .125 microns and 71.4% by weight had a particle size between 125 microns and 355 microns. FIGURE 4 shows a fluid penetration graph illustrative of a. treatment fluid containing cross-linked polyacrylamide particles and polyvinyl alcohol particles in which 28.6% by weight of the polyvinyl alcohol particles had a particle size < 125 microns and 71.4% by weight of the polyvinyl alcohol particles had a particle size between 125 microns and 355 microns. As shown in FIGURE 4, after the period of initial formation at room temperature, the degradable fluid seal remained intact for about 30 minutes at 93.3 ° C (200 ° F) under a differential pressure of 35.15 · kg / cm2 (500 psi).

The previous series of tests illustrates that a combination of degradable polyacrylamide gel particles. Chopped and polyvinyl alcohol particles can be used to produce a degradable fluid seal. The speed in the which fluid seal fails and allows flow, fluid to resume can be altered by combining classified particles of polyvinyl alcohol in various relationships with one another.

Therefore, the present invention is well adapted to achieve the ends and advantages also mentioned as those inherent in this. The particular embodiments described above are illustrative only, as the present invention can be modified and practiced in different but obvious equivalent ways to those of skill in the art having the benefit of the teachings herein. In addition, the limitations that are intended for construction or design details herein are not shown, except as described in the claims below. It is therefore evident that the. Particular illustrative embodiments described above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively described herein may be suitably practiced in the absence of any element that is specifically not described herein and / or any optional element described herein. While the compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods may also "consist essentially of" or "consists of" the various components and steps. All numbers and ranges described above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is described, any number and any included range falling within the range is specifically described. In particular, each range of values (of the form, "from about a to about b," or, equivalently, "from about a to b," or, equivalently, "from about ab") described herein it is to be understood that it establishes each number and range encompassed within the wider range of values. Also, the terms in the claims have their ordinary, flat meaning unless otherwise explicitly and clearly defined by the patent. On the other hand, the indefinite articles "a" or "one," as used in the claims, are defined herein to understand one or more of one of the elements that it introduces. If there is any conflict in the uses of a word or term in this specification and one or more patents or other documents that may be incorporated herein by reference, definitions that are consistent with this specification shall be adopted.

Claims (23)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as novelty, and therefore the content of the following is claimed as property: CLAIMS

1. A method, characterized in that it comprises: providing a sealing composition comprising: a degradable polymer, and a water-soluble material comprising a first portion of rigid particles and a second portion of rigid particles, each. portion of rigid particles has a sealing time and a particle size distribution associated therewith, the particle size distributions of the first portion of rigid particles and the second portion of rigid particles differ from one another; determining an amount of the first portion of rigid particles relative to the second portion of rigid particles in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of rigid particles or the second portion of rigid particles; introducing the sealing composition into an underground formation; and allowing the sealing composition to form a degradable fluid seal in the underground formation.

2. The method according to claim 1, characterized in that the water soluble material comprises a water soluble polymer.

3. The method according to any of the preceding claims, characterized in that the water-soluble polymer comprises at least one polymer selected from the group consisting of polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, acetyl cellulose, hydroxyethyl cellulose, shellac, chitosan, chitin, dextran, guar, xanthan, starch, a scleroglucan, a diutane, poly (vinyl pyrrolidone), polyacrylamide, polyacrylic acid, poly (diallyldimethylammonium chloride), poly (ethylene glycol) ), poly (ethylene oxide), polylysine, polymethacrylamide, polymethacrylic acid, poly (vinylamine), any derivative thereof, any copolymer thereof, and any combination thereof.

4. The method of. according to any of the preceding claims, characterized in that the degradable polymer comprises particles of a gelled degradable polymer.

5. The method according to any of the preceding claims, characterized in that the degradable polymer comprises at least one crosslinked polymer selected from the group consisting of a crosslinked polyacrylamide, a crosslinked polymethacrylamide,. any hydrolyzed or partially hydrolyzed variant thereof, any derivative thereof, any copolymer thereof, and any combination thereof.

6. The method of conformance, with any of the preceding claims, characterized in that the degradable polymer comprises at least one crosslinked polymer selected from the group consisting of a crosslinked polyacrylamide, a crosslinked polymethacrylamide, any hydrolyzed or partially hydrolyzed variant thereof, any derivative thereof, any copolymer thereof, and any combination thereof.

7. The method according to any of the preceding claims, characterized in that the sealing composition is introduced into the underground formation in a fluid, of treatment having a basic pH

8. The method of compliance with any of the preceding claims, characterized in that at least a portion of the underground formation has a permeability of at least about 0.5 D.

9. The method according to any of the preceding claims, characterized in that it further comprises: perform a treatment operation in the underground formation while the degradable fluid seal is intact; Y allow the seal of degradable fluid to degrade.

10. A method, characterized in that it comprises: providing a sealing composition comprising: particles of a gelled degradable polymer, and . a water-soluble material comprising rigid particles having a sealing time and a particle size distribution associated therewith, the particle size distribution of the water-soluble material differs from that of a water-soluble material without glueing same; determining a particle size distribution of the rigid particles necessary to produce a degradable fluid seal having a desired sealing time; introducing the sealing composition into an underground formation; form a degradable fluid seal in the formation underground sealing composition; perform a treatment operation in the underground formation while the degradable fluid seal is intact; Y allow the seal of degradable fluid to degrade.

11. The method according to claim 10 characterized in that, during or after degrading, the degradable fluid seal dissolves in a fluid present in the underground formation.

12. The method according to claim 10 or 11, characterized in that the water-soluble material comprises a first portion of rigid particles and a second portion of rigid particles, each portion having a sealing time and a particle size distribution associated therewith, the particle size distributions of the first portion of rigid particles and the second portion of rigid particles differ from one another.

13. The method according to claim 12, characterized in that a sealing time of the degradable fluid seal can be altered by changing an amount of the first portion of rigid particles relative to the second portion of rigid particles.

14. The method according to claim 10, 11, 12, or 13, characterized in that the water soluble material comprises a water soluble polymer.

15. The method according to claim 14, characterized in that the water-soluble polymer comprises at least one polymer selected from the group consisting of polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, acetyl cellulose, hydroxyethyl cellulose, shellac, chitosan, chitin, dextran, guar, xanthan, starch, a scleroglucan, a diutane, poly (vinyl pyrrolidone), polyacrylamide, polyacrylic acid, poly (diallyldimethylammonium chloride), poly (ethylene glycol), poly (ethylene oxide), polylysine, polymethacrylamide, polymethacrylic acid, poly (vinylamine), any derivative thereof, any copolymer thereof, and any combination thereof.

16. The method according to claim 10, 11, 12, 13, 14, or 15, characterized in that in the present the gelled degradable polymer comprises at least one crosslinked polymer selected from the group consisting of a crosslinked polyacrylamide, a crosslinked polymethacrylamide, any hydrolyzed or partially hydrolyzed variant thereof, any derivative thereof, any copolymer thereof, and any combination thereof.

17. The method according to claim 16, characterized in that the sealing composition is introduced into the underground formation in a treatment fluid having a basic pH.

18. The method according to claim 10, 11, 12, 13, 14, 15, 16, or 17 ,. characterized in that at least a portion of the underground formation has a permeability of at least about 0.5 D.

19. A method, characterized in that it comprises: providing a plurality of gelled degradable polymer particles; providing a first portion of a water soluble material and a second portion of a water soluble material, each portion comprising rigid particles and each portion having a sealing time and a particle size distribution associated therewith, the size distributions of particle differ from one another; Mix the first portion of the. water soluble material and the second portion of the water soluble material with the plurality of gelled degradable polymer particles, thereby forming a sealing composition; determining an amount of the first portion of the water soluble material relative to the second portion of the water soluble material in the sealing composition necessary to produce a degradable fluid seal having a desired sealing time that is different from the sealing time of either the first portion of the water soluble material or the second portion of the water soluble material; and introducing the sealing composition into an underground formation to form a degradable fluid seal thereon.

20. The method according to claim 19, further characterized in that it comprises: choosing the particle size distributions of the first portion of the water-soluble material and the second portion of the water-soluble material necessary to produce a degradable fluid seal having a desired sealing time.

21. The method according to claim 19 or 20, characterized in that the water soluble material comprises a water soluble polymer.

22. The method according to claim 21, characterized in that the water soluble polymer comprises at least one polymer selected from the group consisting of polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, acetyl cellulose, hydroxyethyl cellulose, shellac, chitosan, chitin, dextran, guar, xanthan, starch, a scleroglucan, a diutane, poly (vinyl pyrrolidone), polyacrylamide, polyacrylic acid, poly (diallyldimethylammonium chloride), poly (ethylene glycol), poly (ethylene oxide), polylysine, polymethacrylamide , polymethacrylic acid, poly (vinylamine), any derivative thereof, any copolymer thereof, and any combination thereof.

23. The method according to claim 19, 20, 21, or 22, characterized in that the gelled degradable polymer comprises at least one crosslinked polymer selected from the group consisting of a crosslinked polyacrylamide, a crosslinked polymethacrylamide, any hydrolyzed or partially hydrolyzed variant of the same, any derivative thereof, any copolymer thereof, and any combination thereof.