RU2566543C1 - Treatment method of bottom-hole zone for high-viscous oil formation with combustible oxidation compound - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes running in tubing to the well, injecting combustible and oxidizing composition (COC) to the tubing, running in ignition source at a cable to the tubing to COC interval, delivering control signal to the cable and igniting COC. At the wellhead bottom of the tubing string is equipped with a combustion chamber with burner. At that upstream the combustion chamber the tubing string is equipped with a packer, run in the tubing string to the well so that the packer is set at distance of 30 m above the formation roof. Thereafter through the tubing string at electrical cable combined with fibre-optic cable the ignition source is run in up till it contacts the burner, then injection of COC is started to the tubing string with permanent rate. At that COC of the following composition is used in wt %: ammonium nitrate - 45.5; 2% aqueous solution of polyacrylamide - 19.5; potassium bichromate - 5; ethylene glycol - 30. When COC reaches the burner of combustion chamber the electric igniter is actuated by control signal sent to the electric cable, COC ignition takes place in the burner of combustion chamber. Ignition and commencement of COC combustion in the combustion chamber is monitored. Thereupon the electric cable combined with fibre-optic cable is removed from the tubing string, the packer is set in the well, COC combustion and heating of high-viscous oil is continued till viscosity decreases up to the value sufficient for product extraction with pump equipment.

EFFECT: improved efficiency in heating of high-viscous oil formation and reliability of the method implementation.

2 dwg

Description

The invention relates to the oil industry and can be used for treating a formation with highly viscous oil with heated gas generated during the combustion of a liquid fuel-oxidizing composition (GOS).

A known method of processing the bottom-hole zone of a formation with a liquid combustible-oxidizing composition (patent RU No. 2459946, IPC E21B 43/263, published in Bulletin No. 24 of 08/27/2012), comprising placing the GOS in the well, installing the GOS combustion initiator by lowering it is in a sealed container, while the GOS is placed in the well by delivering it with the chasing container on the cable and pouring the GOS as a single mass into the face to the bottom of the processing interval, the combustion initiator is delivered in the sealed container by a cable to the gran the interface between the GOS and the well fluid, with a low-gas, slow-burning and high-temperature solid composition, for example, based on iron-aluminum termite, being used as a combustion initiator in a sealed container, then the combustion initiator is directly triggered from a source of electricity supplied through a cable cable from the wellhead, with the possibility of layer-by-layer combustion of GOS.

The disadvantages of the method:

- firstly, the low efficiency of heating the reservoir with high viscosity oil, since the bulk of the heat that is released during the combustion of the GOS "goes" into the annulus of the well, without penetrating deep into the reservoir with high viscosity oil, so the treated formation is heated only in the bottomhole zone of the well ;

- secondly, the low reliability of the implementation of the method, due to the failure of the container-bailer on the cable-cable at the bottom of the well and, as a result, the inability to pour the GOS from the container-bailer to the bottom of the well;

- thirdly, the low quality of the treatment of a highly viscous oil formation due to pouring a limited amount of GOS on the bottom of the well to the bottom of the processing interval with its subsequent ignition, therefore, the time during which the estimated amount of GOS is burned may not be enough to warm the formation;

- fourthly, the uncontrolled process of ignition and the start of combustion of GOS, leading to the creation of an explosive situation in the well;

- fifthly, it is impossible to use GOS, for which a liquid composition consisting of wt. % of ammonium nitrate - 60.4; glycerol - 10 and water - 29.6, density 1390 kg / m ³ , in the winter period of time, since one of the main components is water, which freezes at a negative temperature.

The closest in technical essence and the achieved result is a method of treating a formation with a liquid combustible-oxidizing composition (patent RU No. 2092682 IPC E21B 43/263, publ. In bulletin No. 28 of 10/10/1997), containing placement in the well of GOS, installation it contains a thermal energy source for igniting the GOS by lowering it into the well, supplying a control signal to turn on the heat energy source and igniting the GOS due to heat generation in the heat energy source, and the GOS is placed in the well by lowering the pumping unit to the bottom of the well compressor pipes (tubing), injecting the estimated amount of GOS into the deflated tubing, pushing the GOS to the processing zone and then raising the tubing from the GOS location, and the heat source is installed at a depth of 10-50 m from the upper GOS border, while the source thermal energy use a source with energy release (E, MJ), the minimum value of which is determined from the expression E = k · (T _p -T ₀ ), where k is approximately 0.1-0.125 MJ / K; T _p - the temperature of the beginning of the intensive decomposition of the most heat-resistant component of GOS, K; T ₀ - initial GOS temperature in the ignition zone, K; moreover, when the GOS is located in the well for a long time before the ignition is ignited, a separation fluid is used, and its density should not be higher than the GOS density and not lower than the density of the well fluid, and when the treatment zone is far from the bottom of the well, a restriction screen is installed at the lower boundary of the GOS placement. The tubing is lowered to pump the GOS to the restriction screen. To prevent water hammer on wellhead equipment, part of the well fluid is removed from the well before igniting the GOS. As a source of thermal energy, a powder charge of ballistite or mixed solid fuel weighing at least 7 kg is used.

The disadvantages of the method:

- firstly, the low efficiency of heating the reservoir with high viscosity oil, since the bulk of the heat that is released during the combustion of the GOS "goes" into the annulus of the well, without penetrating deep into the reservoir with high viscosity oil, so the treated formation is heated only in the bottomhole zone of the well ;

- secondly, low implementation reliability due to the fact that GOS is forced from the tubing into the wells, therefore, GOS can leak through a restriction screen or a disturbance in the well, as well as GOS absorption through perforation intervals into the formation during its sale;

- thirdly, the low quality of the treatment of a formation with high viscosity oil by heating, due to the injection and sale in the interval of the treated formation of the estimated (limited) amount of GOS, so the time during which the estimated amount of GOS is burned may not be enough and the formation will not heat up to temperature necessary to dilute highly viscous oil, for example, due to incomplete combustion of GOS. In addition, GOS combustion occurs below the intervals of perforation of the treated formation, which reduces the efficiency of heat penetration deep into the formation with high viscosity oil;

- fourthly, the uncontrolled process of ignition and the start of combustion of the gas treatment plant, which can lead to the creation of a fire and explosive situation in the well;

- fifthly, it is necessary to prepare the well before processing the formation, namely, to establish a restriction screen in the form of an artificial bottom (packer plug, cement bridge) below the treated formation. This leads to a higher cost of implementing the method;

- sixth, the impossibility of using standard GOS at low (negative) temperatures, since one of their main components is water.

The technical objectives of the invention are to create conditions for effective heating of a formation with highly viscous oil, as well as a reliable and high-quality method of treating a formation with highly viscous oil by heating with gases generated during the operation of the GOS, with the ability to control the ignition and the start of the GOS combustion, and also to exclude the installation of a restriction screen below the treated reservoir and the development of the composition of GOS, allowing its use in the winter period of time.

The stated technical problems are solved by the method of processing the bottom-hole zone of the formation with highly viscous oil with a combustible-oxidizing composition - GOS, including the descent of the tubing string into the well - tubing, injection into the tubing string of the GOS, launching the ignition source on the cable into the tubing string in the GOS interval, feeding control signal to the cable and ignition GOS.

What is new is that at the wellhead, the bottom of the tubing string is equipped with a combustion chamber with a burner, and the tubing string is equipped with a packer above the combustion chamber, the tubing string is lowered into the well so that the packer is 30 m above the formation roof, and then along the tubing string into the combustion chamber on an electric cable combined with a fiber optic cable, the ignition source is lowered - an electric igniter until it contacts the burner, the GOS is pumped into the tubing string at a constant flow rate, and the GOS of the following composition is used, wt.%:

- ammonium nitrate - 45.5;

- 2% aqueous solution of polyacrylamide - 19.5;

- potassium dichromate - 5;

- ethylene glycol - 30,

upon reaching the GOS, the burners of the combustion chamber activate the electric igniter by supplying a control signal to the electric cable, the GOS is ignited in the burner of the combustion chamber, the ignition and the start of combustion of the GOS in the combustion chamber are controlled, and then the electric cable combined with the fiber optic cable is removed from the tubing string , packer is planted in the well, GOS is continued to be burned and high-viscosity oil is heated in the formation with its viscosity reduced to a value sufficient for production selection Pines equipment.

In FIG. 1 and 2 schematically and sequentially depicts a method of processing the bottom-hole formation zone with high-viscosity oil with a combustible-oxidizing composition.

At the wellhead 1 (see FIG. 1), the bottom of the tubing string 2 is equipped with a combustion chamber 3 with a burner 4. As the tubing string, for example, a 60 mm tubing string is used according to GOST 633-80. As a combustion chamber 3, a pipe segment with a diameter of 102 mm and a wall thickness of 6.5 mm is used according to GOST 633-80.

As a burner 4 use any known device that allows you to burn GOS, for example a burner for burning gas and fuel oil (patent RU No. 2403498, IPC F23D 17/00, published in bulletin No. 31 dated 10.11.2010) or a burner for burning gas and fuel oil (Khzmalyan D.M., Kagan Y.N. Combustion theory and furnace devices. - M.: Energy, 1976. - P. 204).

Above the combustion chamber 3, the tubing string 2 is equipped with a packer 5. As a packer 5, any known packer is used to isolate the annular space 6 of the well 1 and maintain tightness in the interval of the packer landing in the range of temperatures perceived by it. The tubing string 2 is lowered into the well 1 so that the packer 5 is 30 m above the formation roof, and the burner 4 is located opposite the perforation intervals 7 of the treated formation 8. The height of the combustion chamber 3 is equal to the height - h of the treated formation 8, for example, h = 8 m .

A tee 9 is installed at the upper end of the tubing string 2. From above, through the tee string 9, along the tubing string 2 into the burner 4 of the combustion chamber 3 on an electric cable 10 combined with a fiber optic cable (not shown in Figs. 1 and 2), for example, using a geophysical elevator PKS - 5 (not shown in Figs. 1 and 2), the ignition source is lowered - an electric igniter 11 (see Fig. 1). Fiber optic cable is used according to GOST R52266-2004 “OPTICAL CABLES”.

The electrical cable 10 is sealed at the upper end of the tubing string 2 in the tee 9 using a lubricator 12. Any known wellhead cable sealant, for example, developed by the TatNIPIneft Institute (Bugulma, RT, Russia), is used as a lubricator 12.

At the wellhead 1, in the tank 13, the proposed GOS composition is prepared or delivered to the well in finished form and the GOS is poured into the tank 13, in the required quantity, for example 3 m ³ . To prepare GOS in the tank 13 add the following components, which are mixed in the tank,% wt .:

- ammonium nitrate - 45.5;

- 2% aqueous solution of polyacrylamide - 19.5;

- potassium dichromate - 5;

- ethylene glycol - 30.

To prepare 3 m ³ GOS use components in the following proportion, kg: ammonium nitrate - 1365; 2% aqueous solution of polyacrylamide - 585; potassium dichromate - 150; ethylene glycol - 900.

Ammonium nitrate is used as an oxidizing agent and is produced according to GOST 2-2013, and polyacrylamide is used as a stabilizing additive and is also a GOS thickener. Potassium dichromate is used to increase flammability, reduce initial ignition and complete combustion of fuel. Available in accordance with GOST 2652-78. Ethylene glycol is used as fuel and is produced according to GOST 19710-83.

This composition has a significant content of ethylene glycol, which leads to its use at low temperatures, since at such a content of ethylene glycol (30%) GOS does not freeze in the winter.

From the wellhead through the lateral branch of the tee 9 using the pump 14, they begin to continuously pump the GOS, for example, at a rate of 0.15 l / s, into the tubing string 2.

As the pump 14, any known pump is used, which supplies the GOS to the holes 15 of the burner 4 with a flow rate that allows the GOS to be maintained in a predetermined temperature range, for example, 800-900 ° C. For example, use the NSh-10 gear pump, creating a flow rate from 0 to 21 l / min.

Upon reaching GOS holes 15 of the burner 4, the electric ignitor 11 is activated by supplying a control signal to the electric cable 10 from the wellhead 1.

As a result of the supply of the control signal to the cable 10 in the electric igniter 11, a spark discharge occurs that ignites the GOS in the burner 4 of the combustion chamber 3 with the formation of an open flame from the holes 15 of the burner 4 in the interval of the treated formation 8.

The fiber optic cable controls the ignition of the GOS and the start of the combustion of GOS in the combustion chamber 3, and when the temperature in the combustion chamber 3 increases, the optical fiber cable sends a signal to the measuring equipment (not shown in Figs. 1 and 2) located at the wellhead 1. Temperature increase in the chamber Combustion 3 means that the ignition and combustion of the GOS have occurred.

When reaching a temperature of 150 ° C in the combustion chamber 3, for example, an electric cable 10, combined with an optical fiber cable, is depressurized at the wellhead 1; at the upper end of the tubing 2, the lubricator 12 is turned off. The electric cable 10, combined with the fiber optic cable and the electric igniter 11, is removed from the tubing string 2 (see Figs. 1 and 2).

Packer 5 is planted (see Fig. 2) in well 1 and the annular space 6 is isolated above packer 5 in well 1. Packer 5 is planted 30 m above the treated formation, which eliminates the negative effect of high temperature in the burner interval 4 on the tightness of the packer 5.

The efficiency of heating the formation 8 with highly viscous oil increases, since the heat that is released during the GOS combustion, thanks to the packer 5 installed in the well 1 above the formation 8, does not "go" into the annular space 6 of the well 1, therefore, the bulk of the heat penetrates into the depth of the formation with high viscosity oil.

During the GOS combustion process, formation 8 is heated (see Fig. 2) both in height and in depth, while liquefying (reducing viscosity) of highly viscous oil in formation 8 occurs.

The reliability of processing a formation with highly viscous oil is increased due to the fact that in the proposed method the liquid GOS does not enter the bottom of the well, but burns 4 combustion chambers 3 in the burner, therefore, in comparison with the prototype, “leaving” (loss) of the non-ignited GOS through the restriction screen is excluded or a disturbance in the well, as well as the absorption of GOS at intervals of perforation into the formation during its sale. The quality of the reservoir treatment is improved due to the constant injection of GOS with a given flow rate, and not the limited volume of GOS, as described in the prototype. As a result of this, the formation is heated (processed) along its entire height and in depth, while the formation zones that are remote from the bottomhole zone of the well are covered by heating and cannot be heated when the prototype implements the method, while eliminating the risk of incomplete combustion of the GOS.

The implementation of the method is continued until the viscosity of high-viscosity oil in the formation 8 is reduced to a value of, for example, 150 cSt, which ensures its selection from the formation 8 by pumping equipment — a screw pump for pumping high-viscosity oil products. Then the tubing string 2 with the combustion chamber 3 and packer 5 is removed from the well. The pumping equipment, the screw pump for pumping high-viscosity oil products into the well 1 are lowered and liquefied high-viscosity oil is taken from the formation 8.

The use of an electric igniter as an ignition source eliminates the uncontrolled operation of a heat energy source (powder charge from ballistite or mixed solid fuel weighing at least 7 kg) for a long time, as described in the prototype, since the electric igniter is lowered into the well once for ignition GOS, after which it is removed from the well.

The proposed method eliminates the need for well preparation, namely, the installation of a restriction screen in the form of artificial bottom (packer plugs, cement bridge), eliminating the additional costs.

The GOS supplied through the tubing string burns down in the combustion chamber, generating heat, and is not forced to artificial bottomhole, as described in the prototype, which leads to a reduction in financial and material costs for the installation of the restriction screen and, as a result, cheaper implementation of the method.

The proposed method allows you to:

- increase the efficiency of heating the reservoir with high viscosity oil;

- to improve the reliability of the implementation of the method when processing a formation with high viscosity oil by heating;

- to improve the quality of processing a formation with high viscosity oil by heating deep into the formation;

- control the process of ignition and the beginning of the combustion of the fuel and oil state and exclude the creation of a fire and explosion hazardous situation in the well;

- exclude the creation of a restrictive screen in the form of artificial slaughter (packer plugs, cement bridge);

- use the composition of GOS in the winter time period.

Claims (1)

A method of treating a bottom-hole zone of a formation with a highly viscous oil with a combustible-oxidizing composition (GOS), including lowering a string of tubing (tubing) into a well, injecting a GOS tubing into a string, injecting an ignition source on a cable into a tubing string into the GOC, supplying a control signal on the cable and ignition of GOS, characterized in that at the wellhead the bottom of the tubing string is equipped with a combustion chamber with a burner, and above the combustion chamber, the tubing string is equipped with a packer, the tubing string is lowered into the well so that the packer is 30 m above of the formation roof, after which the ignition source — an electric igniter until contact with the burner — is lowered into the combustion chamber on an electric cable combined with a fiber optic cable, the GOS is pumped into the tubing string at a constant flow rate, and GOS of the following composition is used,% wt. :
ammonium nitrate - 45.5;
2% aqueous solution of polyacrylamide - 19.5;
potassium dichromate - 5;
ethylene glycol - 30,
upon reaching the GOS, the burners of the combustion chamber activate the electric igniter by supplying a control signal to the electric cable, the GOS is ignited in the burner of the combustion chamber, the ignition and the start of combustion of the GOS in the combustion chamber are controlled, and then the electric cable combined with the fiber optic cable is removed from the tubing string , packer is planted in the well, GOS is continued to be burned and high-viscosity oil is heated in the formation with its viscosity reduced to a value sufficient for production selection Pines equipment.

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