RU2181427C1 - Gel-forming composition for control of formation permeability - Google Patents

Abstract

FIELD: oil producing industry, particularly, compositions for performance of water shutoff operations. SUBSTANCE: offered gel-forming composition may be used in control of filtration flows of oil formations. Limiting of water inflows in oil and gas wells, elimination of overflows of water and gas, disconnection of separate inundated intervals of formation, equalization of absorption profile in injection wells in major repairs of well. Gel-forming composition includes aluminosilicate, inorganic acid and water. Aluminosilicate is used in form of rejected zeolite catalysts in production of zeolite catalysts. Acid is used in form of hydrochloric acid or used sulfuric acid with the following amounts of components, wt.%: rejected in production process zeolite catalysts 3- 8; hydrochloric acid or used sulfuric acid 6-12; the balance, water. EFFECT: higher efficiency of composition by regulation of time of gel formation, viscosity, increased structure strength, solution of ecological problem- utilization of wastes of petrochemical production process, transition from inorganic composition to ecological clean inorganic compositions. 4 cl, 2 ex

Description

 The invention relates to the oil industry, in particular to compositions for carrying out waterproofing works, and can be used in the regulation of filtration flows of oil reservoirs, during overhaul of wells.

 Currently, one of the main problems of the oil and gas industry is the flooding of production and injection wells as a result of breakthrough formation and bottom water.

 Technological practice shows that the greatest effect in the regulation of the filtration permeability of flooded layers is achieved using gel-like compositions. The most promising is the use of gel-forming compositions based on inorganic raw materials, in particular silicon-containing substances.

 Known gel-forming compositions based on various chemical reagents, in particular polymers (M. Surguchev, Secondary and tertiary methods of increasing oil recovery. - M .: Nedra, 1985), organosilicon water-insulating materials based on oligoorganoethoxychlorosiloxanes (trade name 119-204) (A. p. 1680949 AI from 09.30.91 BI 36; A.S. 1808998 BI 14 1993). Silicon-based gelling formulations are also known (US Pat. US 4,257,813, class 106-74; 4640361 class 116-258).

 From a wide variety of technologies based on the use of inorganic gels, one can cite a technology based on aluminum chloride (US Pat. RF 2061856 and 2066743). Technologies using pebble compositions are based on the ability of the aluminum salt - urea - water system to generate an inorganic gel directly in the formation (US Pat. RF 2055167). A gel-forming composition based on sodium silicates is also known, which is used to extract residual oil from highly flooded terrigenous formations, compositions based on derivatives of silicic acid (US Pat. RF 2065442).

 The disadvantages of the known compositions are their low efficiency due to the high gelation rate, high viscosity or low structural stability, as well as the high cost of gel-forming components, which significantly limits the scope of the compositions.

The closest technical solution is a gel-forming composition (Pat. RF 2089723), which includes hydrochloric acid, water and an additive from the class of aluminosilicates, which is used as nepheline in the following ratio of components, wt.%:
Nepheline - 4-10
Hydrochloric acid - 6-10
Water - Else
The disadvantages of this composition are the low gelation rate, insufficient strength of the obtained gels, a slight decrease in core permeability after pumping a gel-forming composition based on nepheline and hydrochloric acid into them.

 The objective of the invention is to increase the efficiency of the composition by adjusting the gelation time, viscosity, increasing the strength of the structure, solving the environmental problem - the disposal of waste from petrochemical industries, the transition from organic compounds to environmentally friendly inorganic.

This object is achieved in that the gel-forming composition for controlling the permeability of formations, including aluminosilicate, inorganic acid and water, contains zeolite catalysts rejected in the production as aluminosilicate and hydrochloric or sulfuric acid as acid in the following ratio of components, wt.%:
Zeolite catalysts rejected during production - 3-8
Hydrochloric or sulfuric waste acid - 6-12
Water - Else
The zeolite catalysts rejected during production have the following composition: SiО ₂ - 36; Al ₂ O ₃ - 23.0; Na ₂ O - 15.9, hazard class IV, are produced according to TU-2163-099-05766575-2000 with mineralization, the filtration rate increases, rheological indicators and lubricating ability deteriorate. The zeolite catalysts rejected during production are a batch of catalysts rejected in shape and size that cannot be used in further production.

 The zeolite catalysts rejected during production are a light yellow powder containing granules of various shapes and sizes.

 Spent sulfuric acid - is produced according to TU-113-000203306-204-92 (production waste). It is a concentrated aqueous solution of sulfuric acid, with a mass fraction of acids in terms of sulfuric acid of at least 65%.

Hydrochloric acid - is produced according to TU 6-01-04689381-85-92. The liquid is yellow, with a density of 1.11 g / cm ³ , 22% concentration.

 The zeolite catalysts used in the studies used in the studies are readily soluble in inorganic acids to form a gelling composition. By varying the concentrations of the starting components, it is possible to obtain sufficiently dense gels with optimal gelation time, which allows them to be recommended for experimental work.

The developed gel-forming compositions based on zeolite catalysts rejected in the production and hydrochloric or spent sulfuric acid are a slightly yellowish solution with an initial viscosity of 1.5-2.5 mm ² / s, which reaches 30 mm ² / s, having a wide gelation time range of 2 hours to several days, at a concentration of 3 to 8 wt.% acid and 6 to 12 wt.% acid rejected in the manufacture of zeolite catalysts
The solution is prepared by conventional mixing of the components. In the process of laboratory research using modern methods and equipment, filtration characteristics were studied, as well as various properties of the resulting gel-forming solutions: the speed and completeness of dissolution of rejected zeolite catalysts in the production, depending on the time and intensity of mixing; study of factors affecting gelation time; determination of the strength characteristics of gels formed in various conditions.

Examples of the preparation of a gelling composition
Example 1 * (prototype, known composition)
7 g of nepheline, 7 g of hydrochloric acid (in terms of 100% dry matter) were dissolved in 86 g of water for 30 minutes, stirring with a magnetic stirrer. Then the solution was drained from the precipitate. The gelation time at 20 ^o C is 74 hours. Kinematic viscosity increased from 1.80 to 25.71 mm ² / s (Table 2).

Example 2
To prepare 100 g of solution (composition 4, table 1), a flask containing 5 g of zeolite catalysts rejected during production, 8 g of spent sulfuric acid (in terms of 100% dry matter) and 87 g of water are stirred on a magnetic stirrer for 5 minutes . In this example, the gelation time at a temperature of 20 ^o C was 30 hours, the kinematic viscosity increased from 1.94 to 28.80 mm ² / s (table. 3).

Example 3
A flask containing 5 g of zeolite catalysts rejected in the manufacture, 9 g of hydrochloric acid (in terms of 100% dry matter) and 86 g of water (composition 9, table 1) was stirred on a magnetic stirrer for 5 minutes. Then the solution is poured from the unreacted precipitate, poured into three tubes and put in thermostats to determine the gelation time at temperatures of 20, 45 and 60 ^o C.

We observe that at a temperature of 20 ^o C this composition solidifies after 40 hours, at 45 ^o C - after 21 hours, at 60 ^o C - after 8 hours. Kinematic viscosity increased from 1.85 to 29.12 mm ² / s (Table 2).

The experiments were carried out in a wide temperature range (from 20 to 60 ^o C) to study the effect of temperature on the stability and strength of the gel, the time and speed of gelation, viscosity characteristics, etc. The results are presented in table. 1-3.

 To determine the gelation time, a solution of the working acid concentration is poured onto a sample of zeolite catalysts rejected during production and mixed thoroughly for 10 minutes. The prepared gel-forming compositions are poured into test tubes and placed in a thermostat at a given temperature. For solutions with a short gelation time (at elevated temperature, high content of gelling components), the tubes are checked every 5 minutes. If the solution does not spread when the tube is tilted, then this time is considered the gelation start time. With an increase in gelation time, the intervals between observations increase. The determination of the gelation start time is carried out several times and an average value is selected.

 A study of the effect of different temperatures on the gelation rate showed that with an increase in temperature, the gelation rate increases by 2-10 times. The gelation onset time also decreases by several times with increasing concentrations of the components of the gelling mixture, as can be seen from the table. 1.

The rheological and mechanical properties of the gels were studied by measuring the kinematic viscosity using a capillary viscometer and the dynamic viscosity of the gels at various shear stresses. The measurement results are summarized in table. 2 and 3. From the obtained experimental data, it is seen that the developed new gel-forming compositions based on zeolite catalysts and acids rejected in the production are low-viscosity fluids that are easily filtered in the pore reservoir and have an initial kinetic viscosity of 1.5-2.5 mm ² / s for several hours (before the start of gelation time). Over time, depending on the concentration of the starting components and temperature, due to the acceleration of the gelation process, the viscosity of the gel-forming composition begins to increase like an avalanche, and the liquid passes into a gel, reaching a viscosity of up to 30 mm ² / s (the limit value of viscosity, which could be determined using capillary viscometer, higher values were determined using a more advanced instrument "Reotest"). When maintaining the formed gels for two days, their strength increases. Thus, when using gel-forming compositions as a water-insulating material, it is necessary to create conditions for the formation of the gel in the reservoir and strengthen its structure (keep the wells at rest for 2-5 days).

The ultimate fracture stress (strength) of the gel formed was determined on a Reotest instrument by the value of the maximum stress from deformation (time) at the minimum (0.333 s ^-1 ) shear rate. The measurements were carried out at 20 ^o C.

Measurements of the dynamic viscosity on the Reotest instrument at various shear rates showed that the initial dynamic viscosity of the gels at low shear rates reaches 20,000 cps and higher. Upon reaching shear rates of 145 s ^{-1, the} dynamic viscosity decreases (Table 3) and remains constant in the range of 100-200 cps.

 Studies on the effect of elevated temperature on the viscosity and strength of gelling compositions have shown that increasing temperature only affects the rate of gel structure formation, the viscosity of the cured composition does not change, and the composition retains its properties.

 From the data table. Figure 3 shows that with a decrease in the concentration of zeolite catalysts rejected during production to 3%, the gel forms, but does not gain sufficient strength, as evidenced by small values of dynamic viscosity (Table 3), and the gel turns out to be loose, inelastic, losing at elevated temperatures and with time strength and stability.

 Laboratory tests for waterproofing were carried out on the installation UIPK (installation for the study of core permeability).

 The experiments were carried out in the following sequence: core samples were extracted and their gas permeability was determined. The core was saturated with water under vacuum. The core was placed in the core holder of the UIPK installation and its water permeability was determined, then a gel-forming composition was pumped into the core. The core was held for a certain time for the formation of the gel structure, after which its water permeability was determined. The results of laboratory studies of filtration are given in table. 4.

In General, based on studies of the properties of the gel-forming composition to control the permeability of the oil reservoir, it follows that the claimed composition:
1) has high filterability in porous media, which contributes to a deeper penetration of the gel-forming composition over long distances, to create an insulating screen of large radius;
2) has characteristics that are widely adjustable, which ensures more uniform coverage by the action of heterogeneous collectors;
3) is homogeneous, cures throughout the entire volume;
4) is technologically advanced, simple and convenient to prepare, has an adjustable gelation period, which makes it possible to exclude emergency situations during the injection process;
5) the components included in the composition are not scarce, have a low cost, because they are large-tonnage waste from petrochemical plants, and therefore, their use allows solving environmental problems of the disposal of production waste;
6) as shown by evaluative filtering experiments, the developed gel-forming compositions based on zeolite catalysts rejected in the production have good water-insulating properties and can be recommended for field tests in oil fields.

Claims (1)

A gel-forming composition for controlling the permeability of formations, including aluminosilicate, inorganic acid and water, characterized in that it contains zeolite catalysts rejected during production, and hydrochloric or spent sulfuric acid as acid in the following ratio of components, wt. %:
Zeolite catalysts rejected during production - 3-8
Hydrochloric or spent sulfuric acid - 6-12
Water - Else

Images