Gelable compositions of water soluble polymers

Abstract: A gelable composition and process are disclosed that delay the gelation and increase the gel strength of gelled water soluble acrylamide-containing polymers contains: (1) a water dispersible first crosslinking compound selected from the group consisting of p -aminosalicylic acid, furfuryl alcohol, RArOC(O)R' and HOArC(O)OR'' wherein Ar represents a phenyl group which can be substituted or non-substituted; R is a hydrogen or a carboxylic group; R' is a C₁-C₆ alkyl; R'' is a hydrogen, a phenyl group, or a C₁-C₆ alkyl; and when R is a carboxylic group, R and C(O)OR'' can be at ortho, meta, or para position with respect to the OC(O)R' group and the OH group, respectively; (2) a water dispersible second crosslinking compound selected from the group consisting of aldehydes and aldehyde-generating compounds; (3) a water soluble acrylamide-containing polymer; and (4) water.

Description: Field of the Invention The present invention relates to gelation of water soluble polymers by organic cross linking agents and to a gelable composition that increases the gel strength of the gelled water soluble polymers. Background of the Invention It is well known to those skilled in the art that gelled water soluble polymers are useful in enhanced oil recovery operations. They have been used to alter the permeability of underground formations in order to enhance the effectiveness of water flooding operations. The polymers along with an appropriate crosslinking agent are injected in an aqueous solution into the formation. They percolate into and gel in the regions having the highest water permeability. Any fluids injected into the formation in subsequent flooding operations will then be diverted away from the gels into regions of the formation having a lower water permeability. A water-dispersible phenolic compound and a water-dispersible aldehyde have been used together as crosslinking agents for the gelation of water soluble polymers in enhanced oil recovery operations. For example, U.S. Pat. No. 4,799,548 discloses using a phenolic compound and an aldehyde for the formation of gelled water soluble polymers. However, the water soluble polymers gel fairly quickly, together with these compounds, after being injected into the formation. Quite often only the regions near the well bore are treated because the polymers gel before they have an opportunity to permeate throughout the entire formation. Furthermore, the polymers form gels that do not withstand the reservoirs' high temperature and high salinity environment over a long period of time to effectively alter the permeability of the underground formations. These gelled polymers are exposed to numerous mechanical forces within the formation which tend to promote the breakdown of the gels. When the gels break down, oil production decreases and it is necessary to retreat the formation with more water soluble polymers. EP-A-0 390 137 and EP-A-0 280 083 relate to compositions comprising an aldehyde, a water soluble acrylamide-containing polymer, water, and a crosslinker being a salicylic acid derivative selected from salicylamide and acetylsalicylic acid, and a phenolic compound, respectively. EP-A-0 475 375 which has to be considered as prior art under Article 54(3) EPC, discloses a composition which contains, apart from a water soluble acrylamide-containing polymer and water, an aminobenzoic acid compound and a water dispersible aldehyde. None of these references discloses the use of hexamethylenetetramine as crosslinking compound. EP-A-0 447 967 refers to a composition comprising as crosslinking compounds a furan derivative and a water dispersible aldehyde. It would therefore be a significant contribution to the art to have a composition that would delay the rate of gelation of the water soluble polymers and a process that would increase the gel strength of water soluble polymers. Summary of the Invention It is an object of the present invention to provide a composition for delaying the rate at which water soluble polymers are gelled by organic crosslinking agents. It is also an object of the present invention to provide a composition having increased gel strength of the water soluble polymer gels. It is a further object of the present invention to provide a gel composition of water soluble polymers that can withstand high temperature over a long period of time. The present invention has the advantage of using environmentally substantially less toxic crosslinking agents. Other objects, features, advantages and aspects of the present invention will become apparent as the invention is more fully described in the following disclosure and claims. According to the present invention, a gelable composition is provided as defined in claim 1. According to another embodiment, the present invention comprises the use of a compound according to the invention as defined in claim 13, for reducing the permeability of watered-out or oil-depleted zones in high temperature subterranean formation. Detailed Description of the Invention The first crosslinking compound useful for the present invention is water soluble and is selected from the group consisting of aspirin, p -aminosalicylic acid, RArOC(O)R' and HOArC(O)OR" where Ar is a phenyl group; R is a hydrogen or a carboxylic group; R' is a C₁-C₆ alkyl; and R" is a hydrogen, a phenyl group or a C₁-C₆ alkyl. The term "water soluble" used herein is to describe a component of the composition that is truly water soluble or is dispersible in water to form a stable suspension. Suitable first crosslinking compounds include, but not limited to, p -aminosalicylic acid, phenyl acetate, phenyl propionate, phenyl butyrate, salicylic acid, phenyl salicylate, aspirin, p -hydroxybenzoic acid, methyl p -hydroxybenzoate, methyl o -hydroxybenzoate, ethyl p -hydroxybenzoate, o -hydroxybenzoic acid, hexyl p -hydroxybenzoate, and mixtures thereof. Presently preferred water soluble first crosslinking compounds are phenyl acetate, phenyl salicylate, and methyl p -hydroxybenzoate. As the second crosslinking compound in the present invention hexamethylenetetramine is used. The water soluble first crosslinking compound is present in the composition in the range of from 0.005 to 5.0 weight percent, preferably from 0.01 to 2.0 weight percent, and most preferably from 0.03 to 1.0 weight percent based on the total weight of the composition. The second crosslinking compound is present in the composition in the range of from 0.005 to 5.0 weight percent, preferably from 0.01 to 2.0 weight percent, and most preferably from 0.03 to 1.0 weight percent. As used in this application, the term "water soluble acrylamide-containing polymer" refers to those polymers which are homopolymers, copolymers, or terpolymers, and are truly water soluble or those which are dispersible in water or other aqueous medium to form a colloidal suspension which can be pumped into a formation and gelled therein. The water soluble acrylamide-containing polymers which are suitable for use in the present invention include those which contain from 5 to 100 mole percent of at least one monomer of the formula: wherein R₁, R₂, and R₃ are selected from the group consisting of hydrogen or alkyl groups containing from 1 to 3 carbon atoms, of which acrylamide and methacrylamide are the preferred examples; and from 0 to 95 mole percent of at least one monomer selected from the group consisting of; (a) those monomers represented by the formula: wherein R₄ is selected from the group consisting of hydrogen or alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from the group consisting of alkylene radicals containing from 1 to 6 carbon atoms or an arylene radical containing from 6 to 10 carbon atoms, and M is selected from the groups consisting of hydrogen, ammonium, potassium, or sodium, of which 2-acrylamido-2-methylpropane sulfonic acid or sodium 2-acrylamide-2-methylpropane sulfonate are the preferred examples; or (b) monomers represented by the formula: where R₆, R₇ and R₈ are independently selected from the group consisting of hydrogen or alkyl groups containing from 1 to 2 carbon atoms of which N-vinyl-2-pyrrolidone is the preferred example; or (c) at least one monomer selected from the group consisting of acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, N,N-dimethylacrylamide, sodium vinylbenzylsulfonate, potassium vinylbenzylsulfonate, vinylacetate, acrylonitrile, methacrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, (acryloyloxy-ethyl)diethylmethylammonium methyl sulfate; or (d) mixtures thereof. The polymerization of any of the above described monomers and their resulting polymers are well known to those skilled in the art. There are numerous references which disclose methods of polymerizing these monomers. For example, See US-A-4 244 826. The manner in which these monomers are polymerized into water soluble acrylamide-containing polymers or the resulting polymer is not critical to the practice of the present invention. Polymerization can be initiated by chemicals, irradiation, or any other techniques known to those skilled in the art. The molecular weight of the water soluble acrylamide-containing polymers utilized in the present invention is not critical. It is presently preferred, however, that the polymer have a molecular weight of at least about 100,000 and more preferably 100,000 to 20,000,000. The upper limit is not critical as long as the polymer is still water dispersible and can be pumped into the formation. The presently preferred class of water soluble acrylamide-containing polymers are those selected from the group consisting of homopolymers of acrylamide, homopolymers of methacrylamide, copolymers of acrylamide and acrylic acid, copolymers of methacrylamide and acrylic acid, copolymers of acrylamide and potassium acrylate, copolymers of acrylamide and sodium acrylate, copolymers of acrylamide and N,N-diaethylacrylamide, copolymers of acrylamide and methacrylamide, copolymers of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, copolymers of acrylamide and N-vinyl-2-pyrrolidone, terpolymers of acrylamide, N,N-dimethylacrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, and terpolymers of acrylamide, N-vinyl-2-pyrrolidone, and sodium 2-acrylamido-2-methylpropane sulfonate. The ratio of the monomers in the above-described polymers is not critical; provided however, that at least 5 mole % of acrylamide or methacrylamide is present in the above-described polymers. Particularly preferred are homopolymers of acrylamide, copolymers of acrylamide and sodium acrylate, copolymers of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, copolymers of acrylamide and N-vinyl-2-pyrrolidone, and a terpolymers of N-vinyl-2-pyrrolidone, acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate. However, other polymers with more subunits may also be utilized in the practice of this invention. Additionally, within the scope of this invention is the use of combinations of homopolymers, copolymers, terpolymers, and tetrapolymers utilizing the above listed monomers. The water soluble acrylamide-containing polymer is present in the composition in the amount of from 0.05 to 10 weight percent, preferably from 0.1 to 5 weight percent, and most preferably from 0.2 to 4 weight percent. The concentration of polymer in the composition depends to some degree upon the molecular weight of the polymer. A high molecular weight results in a higher viscosity of the resulting gel for a particular concentration of polymer. Water generally makes up the rest of the inventive composition. Any suitable method can be employed for preparing the composition of the invention. Thus, any suitable mixing technique or order of addition of the components of the composition to each other can be employed. However, it is generally preferred that the polymer be dispersed in water before contacting the polymer with the other components. The mixing order can vary with the type of polymer used. The use of gelled polymers to alter the water permeability of underground formations is well known to those skilled in the art. Generally, an aqueous solution containing the polymer and a crosslinking agent is pumped into the formation so that it can diffuse into the more water permeable portions of the formation and alter that water permeability by gelling therein. The present invention can be used in a similar manner. An aqueous solution containing the water soluble acrylamide-containing polymer, the first crosslinking compound, and hexamethylenetetramine can be pumped into the formation so that it alters the water permeability of the formation in a similar manner when gelation takes place. The present invention's advantage lies in the fact that, since the gelation of the polymer is delayed, the polymer has an opportunity to travel farther into the formation and effect the water permeability of portions of the formation that would normally go untreated due to their distance from the injection site. In addition, the resulting gel exhibits improved strength. The nature of the underground formation treated is not critical to the practice of the present invention. The composition of the present invention can be used in or can be injected into, fresh water, salt water, or brines, as well as at a temperature range of from 21 to 204°C (70 to 400°F), preferably from 66 to 177°C (150 to 350°F), and most preferably 93 to 149°C from (200 to 300°F). The following specific examples are intended to illustrate the advantages of this invention, but are not intended to unduly limit this invention. Example I (Comparative) The purpose of this example is to illustrate the gelation of a water-soluble polymer by phenol and formaldehyde and to use this example as a control. A 0.7 percent solution of a terpolymer composed of 30 wt% of N-vinyl-2-pyrrolidone, 15 wt% of acrylamide, and 55 wt% of sodium 2-acrylamido-2-methylpropane sulfonate was prepared by mixing 11.3 ml of an inverse emulsion which contained 32.4 wt% of the active terpolymer with 500 ml of synthetic sea water. The synthetic sea water used has the following formula: NaHCO₃ 3.69 grams Na₂SO₄ 77.19 grams NaCl 429.00 grams CaCl₂·2H₂O 29.58 grams MgCl₂·6H₂O 193.92 grams distilled H₂O q.s. to 18 liters An aliquot of 88% phenol (0.233 g) and 0.511 ml of 37% formaldehyde were added to 100 ml of the polymer and synthetic sea water mixture described above, to provide a concentration of 2,000 ppm each of phenol and formaldehyde. Similarly, 0.582 g of phenol and 1.278 ml of formaldehyde were added to 100 ml of the polymer and synthetic sea water mixture to generate a concentration of 5,000 ppm each of phenol and formaldehyde. Then 20 ml samples of each solution were placed in three ampules (2.2 cm by 22.5 cm). The six ampules were sealed under nitrogen and then placed upright in compartmented aluminum boxes with relief holes and placed in ovens heated to and held at 93°C, 121°C, and 149°C (200°F, 250°F, and 300°F). Periodically, the ampules were removed from the oven and the mechanical strength of the gels was determined behind a protective shield. As crosslinking developed, small microgels or granules began to appear, i.e., a very slight gel formed. Continued growth of the microgels to globule occurred next, referred to as slight gel. Larger gel masses next appeared, referred to as partial gel, followed by the development of stronger gels with measurable tongue lengths. The tongue lengths were measured by placing each ampule horizontally behind a shield for safety, allowing the hot gelling composition to move to its equilibrium position and then measuring the length of the tongue formed. As gelation progressed with time, stronger gels and shorter tongue lengths were developed. Additionally, when some gels syneresed, liquid content in the ampules were measured by the length of the liquid with the ampules in vertical positions. The mechanical strength is expressed mathematically as Percent Gel Strength = (AL-TL) x 100 / AL where AL equals ampule length (in centimeters), and TL equals the tongue length of the gel measured in centimeters from the point at which the gel contacts the entire circumference of the tube to the farthest point to which the gel has spread. Thus the strongest gels would have a gel strength of 100% and the weakest gels would have a gel strength of 0. The tongue length results are shown in Table I. Table I shows that after 1535 days at 93°C (200°F) in the presence of 2,000 ppm each of phenol and formaldehyde, relatively poor gel (based on the gel length of 18.2 cm and the liquid height of 0.4 cm) developed. The higher the liquid, the more syneresis was. Syneresis is an undesirable characteristics. Similarly, at 5,000 ppm concentration each of phenol and formaldehyde, faster gelation occurred and shorter gels were formed. Table I also shows that, at higher temperature (121°C (250°F)) and at a given crosslinker concentration (2,000 ppm), the gelation rate increased resulting in decreased tongue length indicating improved gel strength. However, when the temperature was 149°C (300°F), excessive syneresis was observed in as short as 63 days (1.0 cm liquid) and then at 1109 days, the gel gave 4.0 cm of liquid indicating a severe syneresis. Example II (Comparative) This example demonstrates that replacing formaldehyde with an aldehyde precursor, hexamethylenetetramine (HMTA), resulted in comparable gelation. The runs were carried out the same as those described in Example I with the exception that HMTA was used in place of formaldehyde in the composition. The results are shown in Table II. Table II shows that the gels produced with HMTA and phenol as crosslinkers are very comparable in quality to those made with phenol-formaldehyde crosslinking system at equal concentrations and temperatures. Example III This example demonstrates that the invention composition comprising HMTA and methyl p -hydroxybenzoate produced superior gels to those made with phenol and formaldehyde (Table I) or with phenol and HMTA (hexamethylenetetramine) as crosslinkers (Table II). The runs were carried out the same as those described in Example I except that the crosslinking agents were methyl p -hydroxybenzoate and HMTA and that 3,500 ppm instead of 5,000 ppm concentration of crosslinkers was tested. The test results are shown in Table III. Gelation of 0.7% Terpolymer in Synthetic Seawater with Methyl p -Hydroxybenzoate and Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel Length (GL) in Centimeters Temp 93°C (200°F) 121°C (250°F) 149°C (300°F) X-linker Conc (ppm) 2,000 3,500 2,000 3,500 2,000 3,500 Aging Time (days) 0.2 T T T T VSG VSG 0.9 T T VSG-SG VSG-SG PG SG 1.0 T VT S-PG S-PG PG SG 1.2 T VT S-PG S-PG PG SG 3.9 VSG SG SG SG PG S-PG 6.9 SG S-PG SG S-PG PG 19.8 11.9 S-PG PG S-PG S-PG 16.9 11.2 18.1 PG 21.0 PG PG 16.5 3.9 21.9 PG 20.0 PG PG VSG 12.4 29.0 PG 16.8 PG 16.0 VSG 11.4GL 61.0 16.1 11.1 5.2 2.5 VSG 15.0GL+1.0L 71.0 16.0 11.1 4.0 2.3 VSG 15.0GL+1.7L 89.0 15.9 13.2 2.2 1.4 VSG-SG 19.0GL+1.0L 110.0 16.4 15.2 2.2 1.1 VSG 12.0GL+1.0L 120.0 16.4 15.1 2.5 1.6 VSG 14.1GL+1.5L 155.0 16.2 15.4 2.5 2.3 VSG 8.8GL+1.5L 279.0 13.0 8.5 3.5 0.0 NG 11.0GL+1.5L 383.0 12.7 7.3 4.7 3.4 Thin 16.5GL+2.0l 550.0 7.9 4.0 4.7 5.6 Thin 11.5GL+2.0L 775.0 2.1 1.8 4.4 2.6 Terminated Terminated 1022.0 2.7 1.8 3.2 2.6 - - T = Thick, VSG = Very Slight Gel, SG = Slight Gel, S-PG = Slight to Partial Gel, PG = Partial Gel, GL = Gel Length, L = the height of liquid separated from the gel, measured when ampule was at vertical position. The results shown in Table III show that substantially stronger (i.e. shorter tongue lengths) gels were obtained, when compared with the results of Table I or II. Table III also shows that the composition containing 2,000 ppm each of methyl p -hydroxybenzoate and hexamethylenetetramine did not form strong (short tongue length) gels until after aging for over 550 days at 93°C (200°F) or over 71 days at 121°C (250°F). However, the results show that some syneresis occurred at 149°C (300°F). The results in Table III further demonstrate that HMTA and methyl p -hydroxybenzoate are effective crosslinking agents suitable for high temperature application to form strong gels and to delay gelling. Example IV This example illustrates an inventive gelable composition comprising an acrylamide-containing terpolymer, salicylic acid and HMTA forms strong gels. The runs were carried out the same as Example III except that methyl p -hydroxybenzoate was replaced by salicylic acid. The results shown in Table V again demonstrate that the inventive composition containing 2,000 ppm each of crosslinkers delayed gelling until after the composition was aged for over 31 days, and a very strong gel (0.7 tongue length) was formed after over 157 days at 121°C (250°F). Gelation of 0.7% Terpolymer in Synthetic Seawater with Salicylic Acid and Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel Length (GL) in Centimeters Temp 93°C (200°F) 121°C (250°F) 149°C (300°F) X-linker Conc (ppm) 2,000 3,500 2,000 3,500 2,000 3,500 Aging Time (days) 0.3 T T T T T T 0.8 T T T T T VT 1.0 T T T T T VT 1.2 T T T T T VT 1.8 T T T T T VT 2.2 T T T T VSG VSG 2.8 T T T T VSG-SG VSG-SG 3.1 T T T T S-PG S-PG 5.9 T T T T 6.6 12.0 8.9 T T T T 4.5 4.5 13.8 T T T T 3.9 1.7 16.9 T T T T 3.5 1.8 23.9 T T T T 10.8 2.5 31.0 Thin T T VSG 11.0 2.8 62.0 Thin T 6.2 18.7 6.8 4.7 91.0 Thin T 2.9 12.2 12.8 3.4 112.0 Thin T 2.3 6.3 12.8 3.6 122.0 Thin T 2.1 4.0 13.6 3.5 157.0 T VT 1.5 3.6 14.8 3.5 281.0 NG VT 0.7 2.0 19.0GL 9.5 384.0 NG VT 0.6 2.3 BG 6.5 582.0 VSG VT 0.6 1.9 BG 11.5 770.0 11.5 14.5 0.5 2.1 Terminated 11.5 1024.0 6.0 14.1+0.3L 0.5 2.2 12.2 T = Thick, VT = Very Thick, VSG = Very Slight Gel, BG = Broken Gel, S-PG = Slight to Partial Gel, VSG-SG= Very Slight Gel to Slight Gel, GL = Gel Length, L = the height of liquid separated from the gel, measured when ampule was at vertical position. Again, the results shown in Table IV demonstrate that gelation of the polymer was delayed and strong gels were formed, even at 149°C (300°F) (3,500 ppm concentration). Example V-VIII These examples further illustrate inventive gelable composition comprising an acrylamide-containing terpolymer and proper crosslinking compounds also form strong gels. The runs were carried out the same as those described in Example I except that the crosslinkers and their concentrations in Example I were replaced by those shown in Tables V-VIII. As shown in Tables V-VIII, some of the inventive compositions did not gel until after the compositions had been aged at high temperatures for months and eventually formed strong (short tongue length) gels, especially those comprising phenyl acetate and HMTA (Table VI), and phenyl salicylate and HMTA (Table VIII), at 121°C (250°F) formed gels having 0 tongue length. Gelation of 0.7% Terpolymer in Synthetic Seawater with Aspirin Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel Length (GL) in Centimeters Temp 93°C (200°F) 121 °C (250°F) 149°C (300°F) X-linker Conc (ppm) 2,000 3,500 2,000 3,500 2,000 3,500 Aging Time (days) 0.2 T T T T T T 0.8 T T T T T T 1.0 T T T T T T 1.2 T T T T T T 3.2 T T T VT T T 3.8 T T T VT T VSG 4.8 T T T T S-PG S-PG 7.9 T T T T VSG VSG 15.0 T T T T VSG VSG 47.0 T T 18.0 PG VSG VSG 57.0 T T 13.6 16.5 VSG VSG 75.0 Thin Thin 5.6 6.9 VSG-SG 5.5GL+5.0L 96.0 Thin Thin 4.0 4.4 VSG-SG 4.6GL+5.6L 106.0 Thin Thin 3.4 3.2 VSG-SG 5.5GL+5.0L 141.0 Thin Thin 3.4 2.6 VSG-SG 4.9GL+5.0L 369.0 Thin NG 2.3 1.9 Thin 3.3GL+5.2L 536.0 Thin S-PG 1.7 1.7 Thin 2.9GL+5.3L 762.0 Thin 13.2 2.2 2.3 Terminated 2.5GL+4.5L 1008.0 Terminated 5.3 1.5 1.7 - 2.4GL+4.5L T = Thick, VT = Very Thick, VSG = Very Slight Gel, S-PG = Slight to Partial Gel, NG = No Gel, PG = Partial Gel, L = the height of liquid separated from the gel, measured when ampule was at vertical position. Gelation of 0.7% Terpolymer in Synthetic Seawater with Phenyl Acetate and Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel Length (GL) in Centimeters Temp 93°C (200°F) 121°C (250°F) 149°C (300°F) X-linker Conc (ppm) 1,950 3,400 1,950 3,400 1,950 3,400 Aging Time (days) 0.2 NG T T T VSG VSG 0.9 T T T T VSG VSG 1.2 T T VSG VSG VSG VSG 3.9 VSG VT VSG T VSG S-PG 7.9 VSG VSG VSG T VSG 7.2 11.2 VSG VSG VSG T S-PG 5.2 15.0 VSG-SG VSG VSG T S-PG 4.0 18.9 VSG-SG VSG VSG VSG PG 3.0 77.0 S-PG S-PG PG 1.7 6.9 2.0 127.0 S-PG PG+0.5L 3.8 0.0 7.5 0.0 153.0 PG PG+0.8L 2.8 0.0 15.8 3.5 197.0 PG 13.5GL+1.1L 1.8 0.2 17.5GL 3.2 246.0 PG 12.9GL+1.8L 1.8 0.2 17.5GL 3.8 298.0 12.0GL+2.3L 13.1GL+1.5L 1.3 0.0 PG 4.6 405.0 14.0GL+1.8L 11.7GL+1.8L 1.5 0.0 SG 11.5 510.0 14.0GL+2.1L 10.7GL+1.6L 1.2 0.0 Terminated 13.0+0.2L 677.0 14.0GL+2.2L 8.5GL+1.8L 1.7 0.0 - PG 898.0 11.1GL+2.1L 2.9 2.5 0.0 - BG 1142.0 6.1+2.1L 2.6 3.1 0.0 - Terminated T = Thick, VT = Very Thick, VSG = Very Slight Gel, S-PG = Slight to Partial Gel, PG = Partial Gel, BG = Broken Gel, GL = Gel Length, L = the height of liquid separated from the gel, measured when ampule was at vertical position. Gelation of 0.7% Terpolymer in Synthetic Seawater with 4-Aminosalicylic Acid and Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel length (GL) in Centimeters Temp 93°C (200°F) 121°C (250°F) 149°C (300°F) X-linker Conc (ppm) 2,000 3,500 2,000 3,500 2,000 3,500 Aging Time (days) 0.2 6.9 13.2 4.7 4.0 5.6 5.1 0.8 3.9 3.6 6.0 4.9 8.1 8.0 1.2 4.0 3.8 5.0 5.1 7.5 7.8 2.0 4.0 3.6 6.0 5.8 13.5 8.5 4.9 4.0 3.7 6.8 6.4 10.8 12.9 5.9 4.7 4.4 6.8 10.3 12.3 5.2 12.0 3.8 6.0 6.5 10.6 14.4 12.1 19.0 4.2 4.0 6.7 7.3 14.9 13.2 47.0 6.3 5.7 11.1 7.5 PG PG 75.0 5.2 9.4 8.4 7.2 PG+3.7L PG+3.5L 138.0 6.5 8.8 10.8 6.3 - - 239.0 4.2 3.7 5.7 7.3 Terminated Terminated 316.0 4.8 3.4 8.7 4.7 - - 359.0 4.3 3.9 12.5 4.8 - - 391.0 4.4 7.8 7.8GL+1.0L 7.3 - - 408.0 6.4 7.9 10.7GL+1.6L 7.2 - - 566.0 4.2 6.7 6.8GL+2.1L 8.7+0.1L - - 672.0 4.4 4.0 6.7GL+2.2L 9.0+0.1L - - 884.0 6.1 7.7 6.8GL+2.3L 2.6+0.1L - - PG = Partial Gel, L = the height of liquid separated from the gel, measured when ampule was at vertical position. Gelation of 0.7% Terpolymer in Synthetic Seawater with Phenyl Salicylate and Hexamethylenetetramine at 93°C, 121°C and 149°C (200°F, 250°F and 300°F) Tongue Length or Gel Length (GL) in Centimeters Temp 93°C (200°F) 121°C (250°F) 149°C (300°F) X-linker Conc (ppm) 1,950 3,400 1,950 3,400 1,950 3,400 Aging Time (days) 0.2 NG NG NG NG NG NG 0.9 NG NG NG NG VSG VSG 1.1 NG NG NG NG VSG VSG 1.9 NG NG NG NG VSG-SG VSG-SG 4.9 T T NG NG 7.7 7.8 8.9 T VSG T T 4.5 4.1 12.2 T VSG T T 4.0 3.4 16.0 T VSG NG NG 3.5 1.7 19.9 T VSG NG NG 3.0 0.9 77.0 T VSG 4.8 2.7 10.1 1.9 128.0 VSG VSG 1.9 0.0 3.6 0.0 162.0 VSG VSG 1.4 0.0 11.1 4.5 198.0 VSG VSG 1.3 0.3 11.1 1.8 247.0 VSG-SG S-PG 1.1 0.4 12.2 2.2 299.0 VSG-SG S-PG 0.6 0.0 12.9 2.1 406.0 NG NG 0.6 0.0 15.8 2.1 511.0 SG S-PG 1.0 0.0 PG 3.3 678.0 SG S-PG 0.9 0.0 BG 3.6+0.4L 899.0 SG SG 1.1 0.0 Terminated 8.9+0.4L 1142.0 Terminated Terminated 1.5 0.0 Terminated 9.5 T = Thick, VT = Very Thick, NG = No Gel, VSG = Very Slight Gel, VSG-SG = Very Slight Gel to Slight Gel, BG = Broken Gel, S-PG = Slight to Partial Gel, PG = Partial Gel, GL = Gel Length, L = the height of liquid separated from the gel, measured when ampule was at vertical position. The results shown in the above examples clearly demonstrate that the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned as well as those inherent therein. While modifications may be made by those skilled in the art, such modifications are encompassed within the present invention as defined by the specification and the claims.

Claims: A composition comprising: (1) a water soluble first crosslinking compound selected from acetylsalicylic acid, p-aminosalicylic acid, RArOC(O)R' and HOArC(O)OR", wherein Ar represents a phenyl group; R is hydrogen or a carboxylic group; R' is a C₁-C₆ alkyl; R" is a hydrogen, a phenyl group, or a C₁-C₆ alkyl; and when R is a carboxylic group, R and C(O)OR" can be at ortho, meta, or para position with respect to the OC(O)R' group and the OH group, respectively; (2) hexamethylenetetramine; (3) a water soluble acrylamide-containing polymer; and (4) water. The composition of claim 1 wherein said first crosslinking compound is selected from p-aminosalicylic acid, phenyl acetate, phenyl propionate, phenyl butyrate, salicylic acid, phenyl salicylate, acetylsalicylic acid, p-hydroxybenzoic acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, hexyl p-hydroxybenzoate, methyl o-hydroxybenzoate, and mixtures thereof. The composition of claim 2 wherein said first crosslinking compound is selected from phenyl acetate, phenyl salicylate, methyl p-hydroxybenzoate, and salicylic acid. The composition of any of the preceding claims wherein said first crosslinking compound is present in the composition in the range of 0.005 to 5.0 weight %, preferably 0.01 to 2.0 weight % and more preferably 0.03 to 1.0 weight %. The composition of any of the preceding claims wherein hexamethylenetetramine is present in the composition in the range of 0.005 to 5.0 weight %, preferably 0.01 to 2.0 weight %, and more preferably 0.03 to 1.0 weight %. The composition of any of the preceding claims wherein said polymer contains from 100 to 5 mole % of a monomer selected from those monomers represented by the general formula: wherein R₁, R₂, and R₃ are independently selected from hydrogen and alkyl groups containing from 1 to 3 carbon atoms, and from 0 to 95 mole % of a monomer selected from (a) those monomers having the general formula wherein R₄ is selected from hydrogen and alkyl radicals containing from 1 to 6 carbon atoms, R₅ is selected from alkylene radicals containing from 1 to 6 carbon atoms and an arylene radical containing from 6 to 10 carbon atoms, and M is selected from hydrogen, ammonium, potassium, and sodium; (b) a monomer represented by the general formula: wherein R₆, R₇, and R₈ are independently selected from hydrogen and alkyl radicals containing from 1 to 2 carbon atoms; (c) a monomer selected from acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, potassium methacrylate, ammonium methacrylate, N,N-dimethylacrlyamide, vinylsulfonic acid, sodium vinylsulfonate, potassium vinylsulfonate, ammonium vinylsulfonate, vinylbenzylsulfonic acid, sodium vinylbenzylsulfonate, potassium vinybenzylsulfonate, ammonium vinylbenzylsulfonate, vinylacetate, acrylonitrile, methyl acrylonitrile, vinyl alkyl ether, vinyl chloride, maleic anhydride, vinyl substituted cationic quaternary ammonium compounds, and (acryloyloxyethyl)diethylmethylammonium methyl sulfate; and (d) mixtures thereof. The composition of claim 6, wherein said polymer is selected from homopolymers of acrylamide, homopolymers of methacrylamide, copolymers of acrylamide and N-vinyl-2-pyrrolidone, copolymers of acrylamide and N,N-dimethylacrylamide, copolymers of acrylamide and methacrylamide, copolymers of acrylamide and acrylic acid, copolymers of acrylamide and sodium acrylate, copolymers of acrylamide and potassium acrylate, copolymers of methacrylamide and acrylic acid, copolymers of acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, terpolymers of N-vinyl-2-pyrrolidone, acrylamide and sodium 2-acrylamido-2-methylpropane sulfonate, and terpolymers of acrylamide, N,N-dimethylacrylamide and sodium 2-acrylamido-2-methylpropane sulfonate. The composition of claim 7, wherein said polymer is a terpolymer of N-vinyl-2-pyrrolidone, acrylamide, and sodium 2-acrylamido-2-methylpropane sulfonate. The composition of claim 8 wherein said terpolymer contains said monomers in a 30 : 15 : 55 weight % ratio. The composition of any of the preceding claims wherein said polymer is present in the composition in the range of 0.05 to 10 weight %, preferably 0.1 to 5 weight %, and more preferably 0.2 to 4 weight %. The composition of claims 4, 5 and 10 wherein said water makes up the rest of said composition. The composition of claim 11 wherein said water constitutes from 94 to 99.7 weight %. The use of the composition of any of claims 1 to 12 for reducing the permeability of watered-out or oil-depleted zones in a high temperature subterranean formation comprising injecting said composition into said formation which forms a gel in said formation. The use of claim 13 wherein said injecting is carried out in a subterranean formation at a temperature range of 66 to 177 °C, preferably 93 to 149 °C.

Inventors: ARAGHI-MORADI AHMAD, ARAGHI-MORADI, AHMAD
Applicants: PHILLIPS PETROLEUM CO, PHILLIPS PETROLEUM COMPANY
Application year: 1993
Main classification: E21B33
IPC codes: C08K5, C09K8