HU187707B - Method for eliminating the gel state of fluid systems used at hydraulic ledge blasting - Google Patents

Abstract

The present invention relates to a method for eliminating the gel state of fluids used in hydraulic fracturing. The essence of the process is that the water-soluble carboxymethylcellulose, carboxymethyl starch, polysaccharide, poly (acrylamide), poly (acrylamide) polyacrylic acid copolymer, partially or wholly hydrolyzed poly (acrylamide), polyacrylic acid used in the fracturing process are used. alkaline salt or guar gum-based aqueous fracturing liquid 0.1 l fi. alkaline hypochlorite is added. -1-

Description

Hydraulic rock fracturing is one of the most commonly used methods for increasing the yield of oil, natural gas, or water wells, which results in an increase in the permeability of the storage formations and in the range of production zones.

As a result of domestic and foreign research, there are many types of fluid suitable for fracturing which meet the physical and chemical requirements of fracturing fluids, such as theological, filtration, heat resistance, etc.

However, a problem has so far caused great difficulty in carrying out the fracturing operation. The problem is that whatever fracturing fluid does not decompose at the temperature of the formation to be fractured, it is almost impossible to bring it back to the surface by completing the fracturing operation. If the rupture fluid remains in the formation after rupture, the permeability of the formation is impaired and the pores clogged. Obviously, recovering as much of the fracturing fluids as possible is a very important task. This goal can only be achieved by reducing the viscosity of the bursting fluid, which is usually from 5,000 to 15,000 mPas, or eliminating this state when the liquid is semi-solid. The resulting low viscosity diluted liquid is refluxed back to the perforator and can be easily processed, e.g. by piston - can be brought to the surface.

Gel breaking with ethyl formate, ethyl chloroacetate, methyl acetate or ethyl acetate is known to solve the above problem. Such a procedure is described in U.S. Patent No. 3,960,736. U.S. Pat.

In this case, due to the layer temperature in the formation, the bursting fluid is decomposed by acid hydrolysis and thus its original viscosity is greatly reduced.

In the case of polysaccharide-based bursting gels, persulphate gel breakage is used. Such a solution is disclosed in U.S. Patent No. 4,250,044. See U.S. Patent No. 4,800,800.

No. 800,371. Dutch Patent Specification [C. THE.

95, 9705 (1981), describes a cross-linked, water-soluble hydroxyethylcarboxyethylcellulose as a film-breaking liquid.

Two grades of adjustable viscosity hydroxypropyl guar gum based fluid are described in C. A. 96 (1982) 37,968.

No. 3,451,480. U.S. Pat. No. 4,198,198 to Diacetone-Acrylamide and Acrylamide Copolymer [C. A. 71, 51,929 (1969)],

No. 3,818,991. United States of America and U.S. Patent No. 1,003,629. U.S. Patent Nos. 4,119,125 to 5,102,115 to 4, 6, 7, 8 and 9 describe a solution for reducing the viscosity of a liquid with hydrazine or hydroxylamine [C. A. 81 (1974) 138,422 t and 87 (1977) 55,603 a].

The above procedures are very costly and not suitable for use with any bursting fluid. It should be noted here that the persulphate degradation is effective only for carboxymethylcellulose, with no degradation when using polyacrylamides, polyacrylates and guar gum.

We have found that when carboxymethylcellulose, carboxymethyl starch, polysaccharide, and poly (acrylamide), poly (acrylamide) polyacrylic acid copolymer are partially or fully hydrolyzed poly (acrylamide) and alkali polyacrylate or guar. Sodium hypochlorite or potassium hypochlorite is added to the gum-based fracturing fluids, and upon completion of the fracturing process (about 2 hours), the initial viscosity of the fracturing fluid (50-1500 mPas) is reduced to about 5-10 mPas by oxidation at the formation temperature. without sedimentation.

The amount of alkali hypochlorites used will depend upon the nature and, if appropriate, the concentration of the fracturing fluid used. Our experiments have shown that 0.1-1% by weight of sodium hypochlorite should be used to achieve the desired goal.

The recovery of the fracturing fluid treated with our proposed hypochlorite solution is no longer a technological problem.

The technological order of hypochlorite gel breakage or viscosity reduction is as follows:

- selection of fluid type capable of fracturing the formation to be fractured;

- preparation of the bursting fluid according to the technology;

- adding hypochlorite to the prepared working fluid in the required amount with vigorous stirring;

applying the thus prepared fracturing fluid to the fracturing operation;

- recovering the decomposed rupture liquid to the surface.

Our studies have shown that hypochlorite-treated fracturing fluids can be stored for at least ten days if not used immediately.

No decomposition or viscosity change is observed at any temperature of about 24 ° C for any type of bursting fluid.

The efficiency of our procedure is demonstrated by the data presented in the attached tables.

Rheological investigations were performed on a Fann 35 SA rotary viscometer. At room temperature (24 'C), measurements were made under laboratory conditions at 100-125-150'C in a Baron Roller Owen rotary autoclave for five hours. 1 and

The data in Table 2 show the change in rheological parameters as a function of temperature. The five hour measurement interval is ideal because in technological practice it is approx. after five hours, recovery of the used operating fluid will begin.

The efficiency of our procedure is also demonstrated by the attached diagrams. These graphs show viscosity change curves as a function of temperature. For comparison, the decrease in viscosity of the hypochlorite-treated fracturing fluid and the treatment fluid is shown as a function of the increase in temperature.

Our procedure is simpler and therefore more economical than known foreign methods.

The following procedure is illustrated by some examples.

EXAMPLE 1 0.1% Sodium Hypochlorite in 10% solution was added to a% carboxymethylcellulose-based aqueous film breaker at least half an hour before use with vigorous stirring. The resulting liquid has a pH of 6.5.

EXAMPLE 2 0.2% NaOCl (pH 6.5) was stirred for 40 minutes prior to the start of the process, to a% aqueous carboxymethyl starch based fluidizing fluid.

Example 3

0.3% sodium hypochlorite (pH 9) was added to the - 0.25% - polyacrylamide based fracturing fluid used in drilling practice.

Example 4

To a 0.5% alkali polyacrylate based fracturing fluid was added 0.4% potassium hypochlorite as above (pH 9.5).

EXAMPLE 5 0.5% sodium hypochlorite (pH 9) was added to a tear guar gum based tear liquid.

Example 6

0.8% sodium hypochlorite (pH 10) was added to the poly (acrylamide) (0.1%) and polyacrylic acid (0.2%) layer fracturing fluid.

Example 7

To a 0.15 wt% hydrolyzed polyacrylamide based aqueous fracturing fluid was added 0.65 wt% sodium hypochlorite (pH 10).

EXAMPLE 8 ^15% by weight, polyacrylic acid-based fracturing fluid, 0.45% by weight of sodium hypochlorite were mixed (pH 'l).

Example 9

0.9% by weight of carboxymethyl starch for 0.2% by weight of polyacrylic acid:

0.3% sodium hypochlorite was added.

Example 10 30

A fracturing fluid was prepared containing 0.4% by weight of guar gum and 0.6% by weight of poly (acrylamide). 0.25% sodium hypochlorite was used to break the gel.

The test data for the liquids produced are shown in the following tables.

Viscosity values and movement resistance data were performed according to the specifications of American Petroleum Instituute RP 39.

The factor 'n' in the tables is the dimensionless factor (r = shear stress, S = shear rate) in the Ostwald de Vaele formula (r = K S) for describing the flow properties, K pe45 dig is the consistency index.

/. spreadsheet

Gel fracture assay of different types of fracturing fluids at 0.55% NaOCl

First example Example 2 based on polysaccharides Example 3 hydrolyzed poly (acrylic amide) based 24 ° C 100 ° C 125 C'150 C ° 24 C ' 100 ° C 125 ° C '150C'24'C 100'C 125' Cl50 'C Apparent viscosity, mPas 150 72.5 20 3 50 11 6 3 150 13 6 2 Plastic bag, mPas viscosity 150 40 13 2 28 6 4 2 150 6 4 1 Motion (0 ') Pa resistor. 23 81.8 3.07 0.26 10.3 2.5 0.26 0.26 36.7 2.04 0.26 0.26 Motion (10 ') Pa resistor, 25.5 97.0 3.34 0.26 15.3 4.6 0.26 0.26 45.9 25.5 0.26 0.26 pH 6.5 6.5 6.5 6.5 6.5 6.5 6.4 6.5 10 10 10 10 n factor - 0.46 0.57 0.58 0.47 0.46 0.58 0.58 - 0.38 0.58 0.42 K - 28.4 3.91 0.52 18.51 4.5 0.52 0.52 - 9.26 0.52 1.11

, 187,707

Table 2

Example 5 Example 8 24 'C 100 'C 125 'C 150'C 24'C 100 'C 125 'C 150'C apparent viscosity, mPas 150 115 41 2 60 34.5 11 2 Plastic viscosity, mPas 150 60 26 1 38 27 6 1 Motion resistance (0 '), Pa 71.5 18.40 25.5 0.26 10.2 2.0 2.5 0.26

Motion resistance (10 '),

Pa 91.9 204.4 30.6 0.26 14.3 4.6 0.26 0.26 PH 9 9 9 9 11 11 11 11 n factor - 0.43 0.60 0.42 0.54 0.72 0.46 0.42 K - 55.19 6.27 1.11 13.24 2.42 4.5 1.11

Table 3

Gel fracture test of different types of rupture fluids with NaOCl equivalent to 0.75 kg Cl ₂ / m ³

Example 7 Example 8 Example 5 24 C ' 100 C ' 125 C ' 24 C ' 100 C ' 125 C ' 24 C ' 100 C ' 125 'C- Apparent viscosity. mPas 150 2.0 2.0 150 150 92.5 150 2.0 2.0 Plastic viscosity, mPas 150 L0 1.0 150 150 25 150 1.0 1.0 Motion resistance (0 '), Pa 36.7 - - 23 13.8 18.4 71.5 - - Motion resistance (10 '), Pa 45.9 - - 25.5 23 20.4 91.9 - - pH 10 6.5 6.5 11 11 11 9 6.5 6.5 n factor - 0.12 0.12 - - 0.76 - 0.12 0.12 K - 0.16 0.16 - - 275.5 - 0.16 0.16

A patent claim

Claims (1)

A patent claim Elimination gélállapotának fluids used in the methods of hydraulic fracturing, characterized in that used in the fracturing operation, polysaccharides - preferably carboxymethyl cellulose, carboxymethyl starch, guar ₅ gum -, poly (acrylamide), poly (acrylamide) acrylic acid copolymer , alkali salt of polyacrylic acid or hydrolyzed poly (acrylamide), or a mixture thereof, based on an aqueous solution of the blasting liquids, 0.1 to 1 wt.% of alkaline hypochlorite is added with stirring.