JPH0561436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition intended specifically for injection into the earth for filling or strengthening it. In particular, such compositions are used to create fluids for filling stalling locks in oil fields.

Generally, during oil recovery, a displacement fluid is injected under pressure, particularly through injection wells drilled into the oil field, to force residual crude oil contained in the stalling lock into the producing well.

To obtain the highest oil recovery, the permeability of the well must be homogeneous because otherwise the displacement fluid will find preferential passage through areas of high permeability without penetrating areas of low porosity. In order to eliminate this drawback, it is planned to fill the highly permeable zone before injection of the replacement fluid.

For this purpose, filling fluids containing gelatable compositions, such as those based on silica, are used.

Filling with silica gel is known and has been used for assisted oil recovery for many years (US Pat. No. 3,375,872). It is generally carried out in two steps, so that in a first step an aqueous solution of alkali metal silicate is injected into the oil field, and then in a second step a reactive substance is injected to gel the solution. .

It is known to provide various ratios of M ₂ O/SiO ₂ (M represents an alkali metal) and to use aqueous solutions of sodium, potassium or lithium silicates in variable concentrations from 0.1 to 10% by weight ( US Patent No.
No. 3805893, No. 3882938, No. 4004639, No.
4069869, 4081029).

Reactive gelling substances include mineral salts such as calcium chloride (U.S. Pat. No. 3,658,131), ammonium sulfate (U.S. Pat. No. 4,069,869), or organohalogenated derivatives such as trichloro, which can be decomposed by hydrolysis upon release of hydrogen acid. Sodium acetate (US Pat. No. 4,293,440), or low molecular weight aldehydes such as formaldehyde, glyoxal (US Pat. No. 4,069,869), which yields carboxylic acids by the Canitzaro reaction.

Although such filling in each method has substantially improved production in old oil fields, the ever-increasing cost of oil products in recent years has led to research to find more efficient filling with fluids.

The problem to be solved is to provide a stable gel with high sealing ability, i.e. as low as possible shrinkage and syneresis phenomenon, and to provide a stable gel with high sealing ability, i.e. as low as possible shrinkage and syneresis phenomenon, which can be applied to deep oil fields at variable temperatures from 40°C to more than 100°C for several minutes to several minutes. The objective is to obtain at best cost a filling fluid that gels in a controllable time that can be varied over time.

Gels from the gelation of aqueous solutions of organic polymers such as polysaccharides or polyacrylamides (Chemical Engineering Review January 24, 1977, pp. 12-13) generally degrade gradually over time. and must therefore be removed.

There is therefore a need for silica-based mineral polymer gels. In order to convert an aqueous solution of alkali metal silicate into a silica polymer gel, it is necessary to use a reactive gelling substance, referred to in the art as a curing agent, and the amount of gel obtained depends in part on it. ing. When such reactive gelling substances are metal salts or acids, premature gelation is obtained and the gel is therefore poorly dispersed in the stalling lock.
Its increased viscosity makes injection of filler difficult or even impossible.

Replacement of metal salts or acids by organohalogenolytic decomposition products with hydrolytic release of hydrogen acids practically does not result in gels, and non-interfering silica masses provide high syneresis rates due to too high acidity. bring about. Curing agents based on low molecular weight aldehydes have an unacceptable curing time that is too long in the case of formaldehyde and too short in the case of glyoxal, in both cases from 40 °C to Although it is possible to adjust the temperature to a variable temperature of 100℃ or more, it is difficult.

It is therefore an object of the present invention to provide a satisfactory solution to the above-mentioned problem, namely to provide a non-toxic, high-quality solution based on aqueous solutions of alkali metal silicates, which are injected into the earth for the purpose of consolidating or sealing the earth. Cheap gels of sealing ability can be made, with low shrinkage, low syneresis rate, stable over time even when subjected to high temperatures and pressures, and at temperatures above 40-100 °C for several minutes. The object is to provide a fluid composition with an adjustable curing time of several hours.

However, the present invention surprisingly provides that a mixture of formaldehyde, glyoxal or a mixture of glyoxal and formaldehyde, a water-soluble aminoplast resin which is a condensation product of urea, and an aqueous solution of an alkali metal silicate can be used at high temperatures and pressures. It has been found to make such silicage gels that are stable, non-toxic, inexpensive, highly sealable, have low shrinkage, low syneresis rates and high curing times.

The composition for underground injection according to the invention therefore comprises an aqueous solution of at least one water-soluble aminoplast resin which is a condensation product of formaldehyde, glyoxal or a mixture of glyoxal and formaldehyde and urea and an alkali metal silicate. Consisting of

The aqueous solutions of alkali metal silicates used are those commonly used in this field by those skilled in the art. For example, the composition according to the invention for 100 cm ³
Commercial aqueous solution of sodium silicate 10-30 cm ³ with a density of 1.36-1.38 and a weight ratio of SiO ₂ /Na ₂ O equal to 3.35.
Contains.

Experience shows that urea-glyoxal resins are particularly effective within the temperature range of 40-80°C, while urea-glyoxal-formaldehyde resins are well suited for higher temperatures of 80-100°C. For temperatures above 100°C, urea-formaldehyde resins are preferred.

Water-soluble aminoplast resins of this type are known and used in the textile industry as finishing resins, and some of them are listed in the literature, such as Textile Research Journal 1969, Vol. 39;
Pages 86-93; Encyclopedia of Chemical Technology 3rd Edition, Volume 2
pp. 454-456, 1979 New York City
Published by Willie & Sons.

These water-soluble aminoplast resins can be prepared by known methods, for example by adding urea to formaldehyde or glyoxal, or a mixture of glyoxal and formaldehyde, or continuously adding glyoxal to the resin in an aqueous medium at a pH of 5 to 9 at a temperature below 100°C. It is then condensed with formaldehyde. The molar ratio of each of these components can vary over a wide range, and in some cases these resins can be
It is generally obtained in the form of an aqueous solution in concentrations that can reach 70% by weight.

In simple laboratory tests, the type and amount of water-soluble aminoplast resin to be introduced into the aqueous solution of the alkali metal silicate in order to obtain a composition according to the invention with the desired curing time and syneresis rate at a constant temperature. can be easily determined.

These tests are carried out by introducing an aqueous solution of sodium silicate, ^e.g.
X g of water-soluble aminoplast resin and water to bring the final volume of the composition to 100 cm ³ are fed, generally at a constant temperature θ of 40-100°C. The time interval between hardening into a mass, which can be observed when the composition no longer flows when tipped over, and the previous production of the composition determines the hardening time. The syneresis rate was evaluated by measuring the volume of liquid separated from the gel after 5 days of storage at temperature θ and expressed in cm ³ per 100 cm ³ of gel.

Starting from laboratory tests, various curves are plotted, such as those that allow calculation of curing time depending on either the amount of water-soluble aminoplast resin used or the temperature. The very easy evaluation of water-soluble aminoplast resins as described above and the simplicity of testing for determination of cure time and syneresis rate can make problem-solving compositions according to the invention a reality.

For example, Alcofix NG, a commercially available urea-glyoxal-formaldehyde resin,
Using 5, 4 and 3 g of (ARKOFIX NG), respectively, it is possible to obtain a release syneresis rate of 0 and curing times of 80, 90 and 120 minutes at a temperature of 95° C. under the conditions described above. Under the same conditions, using 4 g of commercially available urea-formaldehyde resin with a molar ratio of formaldehyde to urea equal to 1.8
A cure time of minutes and a syneresis rate of 0 are obtained. Using 3 g of urea-glyoxal resin in the form of a 50% by weight aqueous solution with a molar ratio of glyoxal to urea equal to 2.1 at 40° C. under the conditions described above.
Curing times of 3 days at 60° C. and 95 minutes at 80° C. can be obtained, with a syneresis rate of less than 5% in all cases.

The composition of the invention is very easily obtained by simply mixing its constituent components. Typically, the selected water-soluble aminoplast resin is dissolved in the desired amount of a commercially available aqueous solution of alkali metal silicate, and the resulting solution is then brought to the desired concentration, if necessary.

As mentioned above, alkali metal silicates and urea-formaldehyde, urea-glyoxal,
The composition according to the invention, consisting of at least one water-soluble aminoplast resin of urea-glyoxal-formaldehyde condensation or urea-glyoxal-formaldehyde condensation, is suitable for filling porous bodies, in particular stalling locks in oil fields subjected to auxiliary recovery of oil. Particularly useful in making fluids. However, it can be successfully used in soil consolidation when building tunnels, dams and other underground structures of this kind.

Although the invention has been presented in purely illustrative form, it is in no way limited to it and it will be understood that useful modifications may be made thereto without departing from the scope of the invention.

Claims (1)

[Scope of Claims] 1. A composition for use in underground injection comprising an alkali metal silicate and at least one water-soluble aminoplast resin, wherein the water-soluble aminoplast resin contains formaldehyde, glyoxal and A composition characterized in that it is a condensation product of urea and an aldehyde selected from the group consisting of mixtures of glyoxal and formaldehyde. 2. A composition according to claim 1 for use in aiding oil recovery. 3. The composition according to claim 1, which is used to compact soil.