RU2615543C2 - Energy-gas-forming composition and processing technology of bottom-hole zone of productive stratum - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: treatment method of bottom-hole zone of productive stratum comprises separate injection of binary mixture components - energy-gas-forming composition and the combustion initiator - through various channels of double-row lift of pump-compressor tubing joint column and initiation of the heat and gas emission process, energy-gas-forming composition is an aqueous solution containing ammonium salts of strong mineral acids, alkali metal nitrite, a stabiliser for maintaining neutral or alkaline medium - ammonia water, or alkali, or soda ash, or pyridine. Energy-gas-forming composition is pumped by an inner row of pipes, where a fire safety device is mounted above the mixing zone of energy-gas-forming composition and combustion initiator. Energy-gas-forming composition is injected in portions of 0,5-1,5 m³, which are alternated with portions of 0,2-0,5 m³ of 15-20% aqueous urea solution to prevent excessive temperature rise in the reaction zone, formalin or acid are used as the combustion initiator.

EFFECT: removal of paraffin deposits, tar and mud solution residues from the bottom-hole zone of the stratum, increased mobility of oil in the bottom-hole zone, ensuring of failure-free operation.

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Description

The invention relates to the oil and gas industry, in particular to compositions and methods for thermogasochemical treatment of the bottom-hole zone of wells in carbonate and terrigenous strata.

The invention can be used to increase the permeability of the bottom-hole zone of a productive formation in order to increase well productivity in oil, gas and gas condensate production, to increase the injectivity of injection wells, and also to increase oil and gas recovery.

A known method of thermogasochemical effects (THHV) on the bottomhole formation zone, in which under the pressure of the gases generated during the combustion of the powder charge at the bottom of the well, the formation ruptures under the pressure of powder gases (N.G. Sereda, V.A. Sakharov, A.N. Timashev, Companion of the oilman and gasman, Moscow, Nedra, 1986, UDC 622.276 + 622.279, p. 315). In this method, the powder charge is delivered to the bottom of the well on the wireline.

During the combustion of the powder charge, the formation of powder gases occurs, which act on the bottomhole formation zone.

The main disadvantages of the method are:

1. Use as an initiator of explosives;

2. The complexity of the method;

3. The impact of high pressures on the wellhead and the cased hole, which can lead to disruption of both the column itself and the annular cement stone, and the equipment lowered into the well.

There is a method of thermochemical treatment of the bottom-hole zone of a formation by pumping into this zone a suspension of granular magnesium and ammonium nitrate in a hydrocarbon-based fluid, followed by pumping a solution of hydrochloric acid into the formation (A.S. 640023). In this case, hydrochloric acid, interacting with magnesium, increases the temperature of the acid and initiates the decomposition of ammonium nitrate. The main sources of heat are: the reaction of magnesium with hydrochloric acid and the decomposition of ammonium nitrate. At the last stage of the method, a mixture of gases, hydrogen and oxygen and nitric oxide may explode, which may adversely affect the state of the cement ring and production casing in the processing interval.

Known methods for thermochemical treatment of the bottom-hole formation zone by injecting GOS fuel-oxidizing compositions into this zone followed by the introduction of combustion initiators: tableted aluminum and chromium oxide powders (Patent RU 2126084); tablets from a mixture of sodium borohydride and sodium peroxide (Patent RU 2154733), a method for treating the bottom-hole zone of a formation by sequentially injecting a mixture of magnesium and propant with liquids based on carbon or water, GOS and acid composition (Patent RU 2440490). The main disadvantages of the above methods are:

1. The use of water-insoluble solids, which limits their penetration into the bottomhole formation zone;

2. The reaction occurs in contact with the initiator of the reaction in the column, which negatively affects the technical condition of the underground equipment.

The closest method for thermochemical treatment of the formation involves the separate injection of components of the GOS fuel and oxidizing composition and IG initiator, through two tubing tubing coaxially located relative to each other. In this case, the end of the external tubing is lowered below the end of the internal tubing by a distance sufficient to ensure the contact time of GOS and IG in the reaction volume. GOS is fed into the treated zone of the oil reservoir only through the annular space between the external and internal tubing, and IG is supplied through the internal tubing. GOS - an aqueous solution with a pH of 4-7, including, by weight. %: saltpeter 5-25, urea-ammonia mixture KAS-32 - the rest; IG - an aqueous solution with a pH of 12-14, including, by weight. %: alkali metal nitrite 15-45, water - the rest, or alkali metal borohydride 15-45, alkali 3-45, water - the rest, and the mass of the IG containing alkali metal nitrite is 1-80% of the mass of GOS, the mass of IG containing alkali metal borohydride is 1-30% by weight (RU 2401941). This method is accepted by us as a prototype.

In the prototype as GOS, i.e. the main source of thermal energy are aqueous solutions of ammonium nitrate or water-soluble combustible compositions of organic origin.

This method has several significant disadvantages:

1. GOS based on ammonium nitrate goes into the stage of continuous reaction, with the release of thermal energy and gases, only when the temperature reaches at least 200 ° C, i.e. in order for the reaction to proceed, it is necessary to heat the solutions and the surrounding rock with another energy source to 200 ° C.

2. This reaction, as is known, does not proceed in limited sizes that are less than critical, that is, cannot flow in pores and fractures of the reservoir.

3. The reaction proceeds in the production casing, which often leads to damage to the casing, cement stone or underground tubing equipment, packer, etc.

All these disadvantages are absent in the proposed method for processing the bottom-hole zone and the proposed compositions. Safety measures are provided to ensure safe and trouble-free operation in the wells.

The technical result is achieved by the fact that in the method of processing the bottom-hole zone of the reservoir, including the separate injection of the components of the binary mixture — the gas-forming composition and the combustion initiator — through different channels of the double-row elevator of the tubing string of the tubing, they initiate the heat and gas evolution process, according to the invention, the gas-generating the composition is an aqueous solution containing ammonium salts of strong mineral acids, alkali metal nitrite, stabilizer to maintain neutral of an alkaline or alkaline medium — ammonia water, or alkali, or soda ash, or pyridine, an energy-gas-generating composition is pumped along the inner row of pipes, on which a fuse is installed above the mixing zone of the energy-gas-forming composition and the combustion initiator, and the energy-gas-generating composition is injected in portions of 0.5 1.5 m ^3, which alternate with portions of 0.2-0.5 m ³ 15-20% strength aqueous solution of urea, to prevent excessive temperature rise in the reaction zone, as initiator mountain Ia formalin or acid.

The method is based on the use of binary mixtures, the reaction between the constituent substances that occur in the following sequence:

1. The exchange reaction between sodium nitrite and ammonium salts with the formation of ammonium nitrite, which is stable only in a neutral and alkaline environment, ie at pH 7 or more.

2. In an acidic environment at pH less than 7, ammonium nitrite decomposes with the formation of water and nitrosine.

3. Nitrazine in an acidic environment breaks down into nitrogen and water with the release of a large amount of thermal energy.

Binary mixtures used in the proposed method include the main energy-gas-forming composition - a solution consisting of two main substances: sodium nitrite and ammonium salts. To stabilize, a stabilizer is introduced into the solution — a reagent that holds the pH of the solution; the pH of the solution is at least 7.

The main gas-forming composition:

1. Water-soluble salts of ammonium (hydrochloric, nitric or organic salts). Preferred use ammonium nitrate 100 pieces 2. Sodium nitrite 69 pieces 3. Stabilizer (ammonia water) (in the summer of 10 parts, in the winter of 6 parts) 10 ÷ 6 parts 4. Water 112 pieces Initiator: 1. Formalin (mineral or organic acids) 10 ÷ 25 parts

Ammonia water is used as a stabilizer. Ammonia water is introduced in the preparation of the composition after dissolving the ammonium salt before dissolving sodium nitrite. Instead of ammonia water, as a stabilizer, you can use any alkali, soda ash or pyridine. All of the above substances maintain the pH of the solution at 7, which ensures the stability of the composition.

For reactions in the prepared aqueous saline, an initiator is required. Initiator - a substance that reduces the pH of a solution below 7, i.e. increasing the acidity of the solution, which is a necessary condition for the reaction of the conversion of ammonium nitrite to nitrosamine. Various acids HCl, CH ₃ COOH, etc., or formalin — an aqueous solution of formaldehyde CH2O — are used as initiator. Formalin is not aggressive to steels and is more preferable. The optimal ratio of formalin solution and gas-forming composition in the mixing zone should be 1: 5.

When using formalin, reactions proceed in the following sequence:

1. NH ₄ NO ₃ + CH ₂ O (formalin) → CH ₂ NH + HNO ₃ ,

the formed nitric acid creates the acidic environment necessary for the following reactions to take place;

2. NH ₄ NO ₃ + NaNO ₂ ↔NH ₄ NO ₂ + NaNO ₃

In an acidic medium, which was formed in the first reaction, the second reaction proceeds actively with a shift to the right, i.e. with the formation of NH ₄ NO ₂ and NaNO ₃ ; and ammonium nitrite, in an acidic environment, turns into nitrosamine, an unstable substance that decomposes with the release of thermal energy and nitrogen.

3. NH ₄ NO ₂ → NH ₂ NO + H ₂ O

NH ₂ NO → N ₂ + H ₂ O + Q

where Q is the thermal energy of 300 kJ / mol (1118 kcal / kg).

This is the main reaction, generating a large amount of heat and gaseous nitrogen, removing colmatants - paraffin, resins, emulsions and drilling mud residues - from the bottomhole zone.

Other reactions take place in parallel. So, at a temperature of 200 ° C, excess ammonium nitrate decomposes:

NH ₄ NO ₃ = NO ₂ + 2H ₂ O + Q (36.8 kJ / mol)

A feature of the method is that the gas-forming composition and initiator are pumped through various channels of a double-row tubing elevator, and their mixing occurs in the bottomhole zone. After mixing the composition with the initiator, the binary mixture enters the reservoir, where the reaction proceeds until the complete decomposition of nitrosamine. The main energy-generating substance is sodium nitrite, which is converted to ammonium nitrite, which, in turn, is converted into nitrosine in an acidic medium, upon decomposition of which thermal energy is released.

The second feature of the reactions in the proposed method is that the reactions proceed without preheating and have an induction period at a temperature of 20 ÷ 25 ° C - 4 minutes, this is the time from the moment of stirring until the temperature reaches 90 ° C, which eliminates premature development of the reaction in the column and is one of the measures to ensure the safety of work.

In addition to this safety measure, the method provides for the injection of an energy-generating composition along the inner row of pipes, on which a fire fuse is installed above the mixing zone of the composition and the initiator. The fuse prevents, in emergency cases, the spread of the redox reaction of nitrate inside the tubing and protects the pipe, packer and column from damage. The packer on the outer pipes is installed 40 ÷ 60 meters above the mixing zone, and it has a through hole, allowing the inner row of pipes to pass through it.

And the third safety measure in the method is that the energy-gas-forming composition is injected in portions of 0.5–1.5 m ³ , which are alternated with 0.2–0.5 m ³ portions of an aqueous 15–20% urea solution. A urea solution inhibits the development of an oxidative reaction and is a source of carbon dioxide during its dehydration in the formation. Carbon dioxide, when dissolved in oil, increases the mobility of oil, reducing its viscosity (L.K. Altunina, V. A. Kuvshinov, “Increasing Oil Recovery by Surfactant Compositions.” Novosibirsk, “SCIENCE”. Siberian Publishing Company RAS, 1995).

A swirler is installed at the end of the inner row of pipes, which provides the necessary mixing of the energy-gas-forming composition and the initiator.

The amount of energy-gas-forming composition used is calculated on the basis of the task facing the contractors. These compositions and methods apply:

a) for cleaning the bottomhole formation zone from resins and paraffins;

b) for the thermogasocyclic stimulation method.

When using the method for the removal of resins and paraffins, the calculation is made from the condition of heating the rock in a radius of 0.8 ÷ 1.2 meters from the well. To warm the rock at 60 ° C and to melt deposits in a radius of 0.8 ÷ 1.2 meters from the axis of the well, 1.5 ÷ 2.5 pore volumes are pumped into the well in this zone of the well.

Example.

The well has a productive capacity of 10 m. The porosity of the rock is 15%, a twofold volume within a radius of 1 meter from the axis of the well bore will be equal to:

2πR ² * 10 * 0.15 = 2 * 3.14 * 1 * 10 * 0.15-V _well = 9.06 m ³

where V _SLE - well volume in the productive zone is 0.36 m ³ .

The density of the gas-forming composition is 1400 kg / m ³ .

The mass of the composition is 9.06 * 1400 = 12684 kg or 12.684 t.

To prepare this composition you will need:

Ammonium nitrate 4,091 t Sodium nitrite 2.82 t Ammonia water 0.327 t Water 4,583 t (m ³ ) Initiator - formalin 0.614 t

Determine the required amount of thermal energy for heating the rock (cylinder, if the well volume is neglected) within a radius of 1 meter with a heat capacity of the rock of 700 kcal / m ³ heating it from 20 ° C to 80 ° C and applying an efficiency equal to 0.4:

14.13 * 700 * 60 / 0.4 = 1483650 kcal

The verification calculation determines the amount of thermal energy generated from the prepared composition as a result of the decomposition of nitrosine - it is 2164581.15 kcal, i.e. excess heat is enough to warm the rock in a radius of 1 meter.

Efficiency takes into account the loss of thermal energy in the adjacent formation and the heating of water in the solution and liquid in the pores of the formation to the required temperature. When the capacity of the reservoir is up to 10 meters, the efficiency is taken equal to 0.4 ÷ 0.6, and when the power is more than 10 meters, the efficiency is taken equal to 0.5 ÷ 0.7.

When using the method for cyclic impact on the formation, heating is carried out in a radius of 5 ÷ 8 meters from the axis of the well and for heating use an amount of solution equal to 1.5 pore volumes.

Claims (1)

A method for treating the bottom-hole zone of a productive formation, including the separate injection of binary mixture components — an energy-gas-generating composition and a combustion initiator — through different channels of a double-row elevator of a tubing tubing string, initiating a heat and gas evolution process, characterized in that the energy-gas-generating composition is an aqueous solution, containing ammonium salts of strong mineral acids, alkali metal nitrite, stabilizer to maintain a neutral or alkaline environment - ammonia water, silt and alkali, or soda ash, or pyridine, an energy-gas-generating composition is pumped along the inner row of pipes, on which a fire fuse is installed above the mixing zone of the energy-gas-forming composition and the combustion initiator, and the energy-gas-forming composition is injected in portions of 0.5-1.5 m ³ , which alternate with 0.2-0.5 m ³ portions ^{of an} aqueous 15-20% urea solution, to prevent excessive temperature increase in the reaction zone, formalin or acid is used as a combustion initiator.