Method of thermochemical fracturing

FIELD: mining.

SUBSTANCE: invention relates to mining and can be used for thermochemical fracturing. The method consists in use of energy of the oxidation reaction of gel-forming compound, initiated by the reaction initiator for fracturing, and proceeding in the bottom-hole area of layer remote from the well. At that the catalyst, the fuel and the initiator are used in the form of solutions in water.

EFFECT: increasing the efficiency of fracturing operations and creation of network of extended cracks which enables to increase significantly the productivity of oil and gas wells.

 

The invention relates to the oil and gas industry, in particular to a method of stimulation, and is intended to broaden and deepen the natural and education of artificial cracks, and can be used to increase the permeability zones of the reservoir and increasing the productivity of the reservoir in the oil, gas and gas condensate or injectivity of injection wells.

There is a method of hydraulic fracturing (fracking), which is designed to increase the permeability of the treated area bottom-hole formation zone (PPP). The essence of fracturing is the injection pressure in the bottomhole formation zone of the liquid, which fills the cracks and rasklinivanie them, as well as the formation of new cracks.

If this is introduced into the formed or enlarged cracks fixing material (e.g. sand), after removal of the pressure cracks are not closed. This method is expensive, time-consuming and requires special pumping equipment (I. Mishchenko. Downhole oil production. "Oil and gas state oil and gas University. I.M. GUBKIN. Moscow, 2007," UDC 622.276.5, str).

There is also known a method of thermochemical effects on the bottomhole formation zone (TREATMENT), in which under the pressure of the gases formed during the combustion at the well bottom powder ZAR is Yes, is fracturing (I. Mishchenko. Downhole oil production. "Oil and gas state oil and gas University. I.M. GUBKIN. Moscow, 2007," UDC 622.276.5, str). In this way the powder charge limited power is delivered downhole logging cable and has a low efficiency and success. Closest to the proposed invention, i.e. its prototype is "Method and composition for chemical initiation of combustion of an aqueous solution horseability composition under pressure processing layer", EN 2154733, IPC EV 43/263.

The invention uses the combustion of aqueous solutions horseability compounds(HOC), used to influence the reservoir pressure gaseous combustion products for excitation of wells by forming cracks or fracturing. In the way of "chemical initiating combustion of an aqueous solution horseability composition under pressure processing layer as the initiator-accelerator combustion using the composition obtained in the form of compressed tablets from a mixture of components of the following composition, wt.%: sodium borohydride 85-95, sodium peroxide 5-15. The initiator is used in amounts of 2-5 wt.% by weight aqueous solution STATE.

Examples of solutions of the STATE, in the prototype, are aqueous solutions based on ammonium nitrate and water-soluble combustible organic what about the origin. Such solutions do not contain toxic components that have a wide resource base, flammable and hazardous under normal conditions, have a low cost. For cracking pressure during combustion solutions GOS well exceed mountain pressure of 25-50 MPa, irreversible cracks are formed at a pressure of ~100 MPa.

This method has some significant drawbacks.

1. The oxidation reaction (combustion) occurs in the production string at pressures far exceeding the strength of the column, and at high temperatures, which leads to disruption as the columns of casing and cement, and lowered into the well hole equipment. Cracks in the layer, if formed that are small and do not lead to a significant increase in well productivity.

2. The invention uses the solid initiator of combustion, which requires special means of delivery to the place of his reaction.

3. Use the initiator of combustion in the form of tablets, requiring special devices for delivery to the combustion zone and geophysical station.

Solved technical problem - creating method that improves the efficiency of processing bottom-hole formation zone while increasing the safety of the process.

This goal is achieved by the fact that the STATE is pumped into the reservoir nagne what W it on the absorption and initiator of oxidative reactions, in the form of a solution, is pumped into the well after pumping water separator packs and introduced into the bottom zone, where the connection STATE with the initiator of the oxidation reaction. Mixing STATE and the initiator react, which occurs with the release of a large amount of gases and vapors. Gases and water vapor formed during the oxidation STATE and initiator, in the natural cracks and pores to create the pressure necessary to expand the existing cracks fracturing, i.e. the creation of new cracks. Download GOS in the bottom zone allows you to use more than in the prototype, the number of PES, i.e improves efficiency and prevents the influence of high pressure on the production casing. Research and calculations showed that the column affects the excess pressure of not more than 10% from the pressure in the reaction zone. The use of more STATE creates in the reservoir network of cracks great length, which greatly increases the effect of operations.

The use of liquid, in the form of an aqueous solution, the reaction initiator delivers it to the reaction zone, mixing with the STATE in the reservoir and the reaction in full. To prevent closure of cracks after the fall of pressure in the area of education and expansion of cracks in this zone is pumped acid the composition, intended for this type of rocks.

Thermochemical gap is made in the following sequence.

Prepared solutions of the STATE and the initiator of the oxidation reaction:

A. GOS is a solution of ammonia (sodium) nitrate in water, has the following composition (wt.%);

- nitrate50%÷60%;
- catalyst4%÷6%;
- fuel0%÷15%;
- restwater.

The catalyst is introduced into the solution to activate the oxidation reaction. As the catalyst used salts of copper chloride copper, copper sulphate and other salts of polyvalent metals.

Fuel is introduced into the STATE to increase the number of products of the reaction gases and water vapor in the case when there is a significant acceleration of the well and a portion of the reaction products rasshivaetsya, and the pressure can not reach the required gap size. As fuel in GOSA used etilenglikoli, urea, various alcohols. In the prepared STATE is entered 5-8% hydrochloric acid concentration of 24% to increase the acidity of the solution to values rn÷rn.

In the case of high priami the employment of the well it is reduced emulsions, Vasami or other blocking compounds.

B. As the initiator of the oxidation reaction used solutions of sodium nitrite, sodium borohydride, and other compounds having reducing properties. The selection of these substances and their concentration is carried out in each case before starting work, and these values depend on reservoir temperature, pressure and composition of the rocks occurring in the reservoir.

A solution of sodium nitrite is prepared from the calculation: 1 m3the solution contains 450-600 kg sodium nitrite.

If the initiator of oxidation reactions is used a solution of sodium borohydride (or other alkali metal), then the solution is prepared as follows.

1 m3water dissolve 100 kg of caustic soda, and cooled the solution to 20°C, dissolved 40-60 kg of sodium borohydride. rn÷rn.

The flow STATE is calculated on the basis of norms 0,2÷0,4 m31 meter penetrated formation thickness.

A solution of sodium nitrite is introduced into a solution of nitrate at a rate of 0.1-0.2 m3, borohydride of 0.05-0.1 m31 m3STATE.

1. In the well down underground following equipment:

- packer with hydrocoral;

- tubing up to the top of the perforated interval.

At the wellhead is installed wellhead equipment, operating pressure which should correspond to the pressure ODA is souki the production string and the expected pressure, occur when processing.

In order to protect the column from the high pressure on the annulus is set relief (vent) valve.

2. Is determined by the injection capacity of the well, and, if it exceeds 15-25 m3at 100 ATM for every 10 m of the perforation interval, produces a reducing injectivity of the injection interval of perforation reverse oil emulsion.

3. In the pumped well planned volume of a solution of nitrate, and through the separating pack of those. water volume 0,8÷1.4 m3injected estimated number of initiated oxidation reactions. The initiator zadumivaetsa in a fluid formation plugging wells in a volume of 5÷10% more than the volume of the pipe. The injection of the initiator into the reservoir needs to maintain at the highest possible speed without stopping.

4. After the process stops at the reaction of 3-5 hours in the well is pumped acid solution at the highest possible speed and zadumivaetsa in the reservoir for the expansion of cracks and prevent full closure.

Example 1

Planned thermochemical fracturing in the well at a depth of 2500 meters, having a perforation interval with a capacity of 25 meters. In the well deflated 73 mm tubing to a depth of 2470 m

The volume of the tubing 7460 litres.

For planned works is trebuetsya:

1. STATE0.3 m3*25=7.5 m3;

where is 0.3 m3- rate STATE 1 meter penetrated formation thickness;

- 25 - opened the seam thickness in meters.

Given that the density of STATE -1350 kg/m3and the weight of the STATE is equal to 1350*7,5=10125 kg

for preparation of STATE required:

Nitrate10125*0,55=5568,75 kg;
The catalyst is copper chloride10125*0,05=506,25 kg;
Fuel - carbamide10125*0,15=1518,75 kg;

Water must 2531,25 kg (liters).

2. To prepare a solution of a reaction initiator, dissolved in 1.3 m3water 120 kg of caustic soda and 72 kg of sodium nitrite.

The procedure works:

- pull underground equipment;

- prepare working solutions in the recipe above;

- upload the absorption of the STATE in the amount of 7.5 m3;

- upload the separating portion of water in a volume of 0.6 m3;

- upload the reaction initiator in the amount of 1.5 m3and to push water into the reservoir in the amount of 7.6 m3;

the reaction in the layer 3 hours;

to inject into the well 15 m3acid solution and push it in place is, procacau 10 m3the kill fluid.

Example 2

Well at a depth of 3500 m the perforation Interval 12 PM

In the well deflated 73 mm tubing to a depth 3475 m

The volume of the tubing 10.5 m3.

To prepare the solutions:

- STATE 4,8 m3weight 6480 kg, including:

ammonium nitrate 3440 kg

the catalyst 324 kg

the glycol 648 kg, water 2070 litres.

The initiating reaction 480 litres. Including:

caustic soda 45 kg,

borohydride 39 kg

the rest is water.

The procedure works:

- pull underground equipment;

- prepare working solutions in the recipe above;

- upload in the hole STATE in the amount of 4.8 m3;

- upload the separating portion of water in a volume of 0.6 m3;

- upload the initiator of the reaction in the volume of 0.48 m3and to push water into the reservoir in the amount of 11 m3;

the reaction in the layer 3 hours;

- injected into the well 10 m3acid solution and push it into the reservoir, procacau 15 m3the kill fluid.

thermochemical method of fracturing, which uses the energy of oxidation STATE, initiated by the initiator of the reaction, for fracturing and not flowing at the well bottom and bottom-hole remote from the well area of the reservoir, using a catalyst, fuel and initiator in the form of solutions in water.



 

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