RU2451174C1 - Method of hydraulic breakdown of formation - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: method of formation hydraulic breakdown (FHB) consists in descending the tubing casing (TS) into hydraulic breakdown zone, pressurisation of casing string annulus by packer, pumping of gas, breakdown agent under pressure through TS. Note that the gas is supplied together with the breakdown agent that is crude oil. Propping agent is supplied after breakdown agent pumping. Note that the gas is inert and it is pumped at 20-30% of breakdown agent volume at a pressure 8 MPa. As propping agent there used is acid-oil emulsion fluid with adding of inert gas at 20-30% of propping agent volume at a pressure 9 MPa. After that the pumping cycle of breakdown agent with gas and propping agent is repeated 3-6 times. Before development the process fluid with inert gas is pumped into tubing casing at 10 MPa in the volume of 20-30% of total volume equal to 1.5-fold inner volume of tubing casing with the following technological exposure for 2-3 h. Note that breakdown agent and propping agent are pumped by equal portions of total volume in each cycle.

EFFECT: simplification of FHB technological process.

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Description

The invention relates to the oil industry and may find application in hydraulic fracturing of oil reservoirs mainly in carbonate rocks.

A known method of hydraulic fracturing (RF patent No. 2122633, IPC 8 E21B 43/27, publ. 1998), which includes injecting into the formation at a pressure above the fracturing pressure of acid agents and proppant.

The disadvantage of this method is that it does not allow to increase the productivity of wells and to develop for injection wells in clay reservoirs and low-power sandstones, in addition, the process of implementing the method differs in the duration of the process and high cost.

Also known is a method of hydraulic fracturing (RF patent No. 2109935, IPC 8 E21B 43/26, published in Bulletin No. 16 of 04/27/1998) by pumping a fracturing fluid into the reservoir with injection as the first portion of the fluid with matting additives, which is used as a stabilized clay oil-water suspension, which is pumped in an amount sufficient to clog the cracks and restore the tightness of the annular cement stone, at a pressure of up to 0.9 from the design fracture pressure, and the stabilized clay oil-water slurry spenziyu used with the addition of iron oxide in an amount of 100-200 kg / m, a stable carboxymethylcellulose in an amount of 0.45-0.55% by volume, the clay stabilized water-in-suspension is pumped in a predetermined volume.

The disadvantages of this method are:

- firstly, the need to use high-pressure expensive pumping equipment, since batch injection of fracturing fluids occurs at high discharge pressures;

- secondly, the tightness of the annular cement stone is restored at a pressure of up to 0.9 from the design fracture pressure, which can lead to fracture of the production string in old wells, especially those subject to corrosion wear.

The closest in essence and the achieved result is a method of hydraulic fracturing in wells (patent RU No. 2219335, IPC 8 E21B 43/26, published in Bulletin No. 24 dated 08/27/2002), including the descent of the pipe string into the hydraulic fracturing zone, sealing annular space, injection of fluid fracturing under pressure, the implementation of hydraulic fracturing of the rock and the flow of proppant. Before the fracture fluid is injected from the interior of the casting column and its annulus, the borehole fluid is displaced by gas, after which the separation plug is placed in the casting string, and during the injection of the fracture fluid into the casting column, additional fluid is pumped into the annulus with a flow rate of Q2, determined from

,

,

where Q ₂ is the flow rate of the fluid pumped into the annulus;

Q ₁ - flow rate of the fracture fluid pumped into the casting column;

S ₂ - the flow area of the annulus of the well;

S ₁ - the flow area of the casting column.

At the same time, the annulus of the well is sealed at the wellhead after filling the annulus with additional fluid and its outflow is stopped during the injection of the fracturing fluid, and the proppant is supplied to the formation together with the fracturing fluid, and air is used as gas for displacing the borehole fluid, and glass or plastic beads with a size of 250-750 microns are used as a proppant, and the time of water hammer is controlled by changing the volume of gas plugs, and the fact of hydraulic fracturing is monitored at the wellhead at the end of the outflow of fluid from the annulus, after which they continue to push the estimated volume of the fracturing fluid containing the proppant into the fracturing zone.

The disadvantages of this method are:

- firstly, the complexity of the process, due to the fact that gas and liquid are pumped separately using a separation plug;

- secondly, after completion of the hydraulic fracturing process, the well is flushed, which does not allow qualitatively and completely to carry out the removal of reaction products and destruction from the collector;

- thirdly, for pumping a proppant, which is used as glass or plastic beads with a size of 250-750 microns, it is necessary to use high-pressure expensive pumping equipment, which is mainly intended for hydraulic fracturing in terrigenous rocks (sands, sandstones), and not carbonate ( dolomite limestone) rocks.

The objective of the invention is to simplify the process of hydraulic fracturing (Fracturing) in carbonate rocks, as well as improving the quality of hydraulic fracturing due to the qualitative and complete removal of the reaction products and destruction from the reservoir.

The problem is solved by the method of acid hydraulic fracturing, including the descent of the tubing string into the fracturing zone, sealing the annulus with a packer, injecting gas, fracturing fluid under pressure along the tubing string, fracturing the rock, delivering a proppant and subsequent well development .

What is new is that the gas is supplied together with the fracturing fluid, which is used as crude oil, and the proppant after the fracturing fluid is injected, the gas being inert and injected in a volume of 20-30% at a pressure of 8 MPa of the volume of the fracturing fluid, and as a proppant, an oil-acid emulsion is used with the addition of an inert gas in a volume of 20-30% at a pressure of 9 MPa from the volume of the proppant, after which the cycle of pumping the fracturing liquid with gas and the proppant is repeated 3-6 times, and before mastering in Onion tubing is pumped with an inert gas of technological fluid in a volume of 20-30% at a pressure of 10 MPa with a total volume equal to one and a half times the internal volume of the tubing string with subsequent technological holding for 2-3 hours, and in each cycle the fracturing fluid and the proppant are pumped in equal shares from total volume.

The figure provides a diagram of the implementation of the proposed method.

The proposed hydraulic fracturing technology (Fracturing) is used mainly in carbonate rocks in order to increase the productivity of wells by creating new and opening existing fractures for processing them with an acid emulsion at a considerable distance from the wellbore.

Before the implementation of the hydraulic fracturing process, installation and technological strapping of equipment is carried out, according to the figure.

The complex of special machinery and equipment according to the figure includes:

1 - well;

2 - capacity for fluid rupture of the estimated volume;

3 - capacity for proppant of the estimated volume;

4, 5 - pumping units, for example, type SIN 32 (GOST 12052-90);

6 - a control station, for example, produced by NPK Neftegeofizika LLC (Russian Federation, Republic of Bashkortostan, Ufa);

7 - block manifolds, for example manifolds (GOST 13862-90);

8 - gas compressor installation, for example, on the basis of the SD-9 / 101M station (Certificate of Conformity No. РОСС RU. АЯ 45В00533);

9 - pump unit, for example, type CA-320 (TU 4523-010-057336-2000).

The suction lines of pumping units 4 and 5 are mounted directly to tanks 1 (with a fracturing fluid) and 2 (with a proppant), respectively, and are connected to valves (not shown). The gas compressor unit 8, pump units 4 and 5 are connected through the manifold block 7. The control station 6 by hydraulic lines is connected to the pump units 4, 5, 9, as well as to the manifold block 7. The manifold block 7 is connected to the inside of the tubing string of well 1. After the installation of equipment and special equipment, as shown in the figure, proceed with hydraulic fracturing. The proposed hydraulic fracturing method involves lowering the tubing string with a packer into the fracturing zone, landing the packer (sealing annular space using a packer) (not shown).

Prior to hydraulic fracturing, the fracturing fluid (crude oil) is delivered to the well in tankers from the freight fleet and poured into tank 1, and the proppant is an oil-emulsion emulsion prepared, for example, on the basis of the NefteChemService enterprise and delivered to tanks 2 and poured into it.

Next, the fracturing fluid is injected - crude oil from the reservoir 2 using the pump unit 4 with the simultaneous start-up of the gas compressor unit 8 through the manifold block 7 with an inert gas flow rate, such as carbon dioxide, amounting to 20-30% of the planned volume of injection of the fracturing fluid in this cycle and further from the manifold block 7 under a pressure of 8 MPa, the fracturing fluid with gas is supplied to the tubing string of the well 1 and from there to the formation zone where hydraulic fracturing is performed (not shown). The carbon dioxide used is produced in accordance with GOST 8050-85.

After the calculated amount of the fracturing fluid has been pumped, the proppant of any known oil acid emulsion with the addition of an inert gas is pumped. For example, the composition of an oil emulsion may be as follows:

- 15% hydrochloric acid (HCl)  - 60% - oil  - 38% - emulsifier reagent "SD-L"  - 2%

Inhibited hydrochloric acid (HCl) is produced in accordance with TU 2122-205-00203312-2000 (Russian Federation, Republic of Bashkortostan, Sterlitamak). Emulsifier reagent "SD-L" is a multicomponent mixture of anionic and nonionic synthetic surfactants and target additives. It is used as an emulsifier (2-3%) of oil-acid emulsions during acid fracturing of carbonate formations. Issued in accordance with TU 2481-001-72650092-2005 NPO TatKhimProduct (Kazan, Republic of Tatarstan, Russian Federation).

Oil-acid emulsion treatment (NEM) is intended to deepen the acid effect on the carbonate formation. The proppant — oil-emulsion emulsion — is injected from the tank 3 using a pump unit 5 with simultaneous start-up of the gas compressor unit 8 through the manifold block 7 with an inert gas flow rate, such as carbon dioxide, amounting to 20-30% of the planned volume of proppant pumping in this cycle and further from the manifold block 7 under a pressure of 9 MPa, a proppant with gas is supplied to the tubing string of well 1 and from there to the fracturing zone.

Subsequently, the process of cyclic injection of the fracturing fluid and the proppant is repeated from 3 to 6 times. In each cycle, the fracturing fluid (crude oil) and the proppant (oil acid emulsion) are pumped in equal shares of the total volume. For example, if the total volume of the fracturing fluid is 30 m ³ and the number of cycles is 5, then the injection volume of the fracturing fluid in each cycle is 6 m ³ . Similarly, the volume of the proppant is determined, if the total volume of the proppant is 12.5 m ³ and the number of cycles is 5, the injection volume of the proppant in each cycle is 2.5 m ³ .

Before the completion of hydraulic fracturing, the last portion of oil acid emulsion inside the tubing string is sold to the hydraulic fracturing zone with process fluid, for example, fresh water with a density of 1000 kg / m ³ and in a volume equal to one and a half times the volume of the tubing string.

The process fluid is pumped from the measured tank (included in the CA-320 pump unit) using the pump unit 9 with the simultaneous start-up of the gas compressor unit 8 through the manifold block 7 with an inert gas flow rate of 20-30% of the planned volume of the fracture fluid in this cycle, and further from the manifold block 7 under a pressure of 10 MPa, the carbonated process fluid is fed into the tubing string of well 1 and pushes the last portion of the oil-acid emulsion into the formation zone, where hydraulic fracturing (not shown). Further, the well remains for the reaction of the oil-emulsion emulsion with the formation rock, usually for 2-3 hours. Next, the well is developed from the products of reaction and destruction, for example, swabbing using the PKS-5 geophysical elevator.

Swabbing is carried out before the expiration of the energy of the injected gas (carbon dioxide), usually within 6 hours. Then the packer is unpacked and the tubing string is removed to the surface.

The proposed method of hydraulic fracturing has a simple process, which reduces the cost and duration of its implementation, in addition, with successive cyclic injection of fracturing fluid and proppant into the reservoir with the addition of inert gas, both the expansion of the rock coverage area and the reservoir are saturated gas, which in turn, due to the energy of the injected gas, allows for better and faster subsequent development of the well from the reaction products, which increases The quality of hydraulic fracturing is due to the qualitative and complete removal of reaction products and destruction from the reservoir.

Claims (1)

The method of hydraulic fracturing, including the descent of the tubing string into the fracturing zone, sealing the annulus with a packer, injecting gas, fracturing fluid under pressure along the tubing string, fracturing the rock, supplying a proppant and subsequent well development, characterized in that the gas is supplied together with the fracturing fluid, which is used as crude oil, and the proppant after the fracturing fluid is injected, the gas being inert and pumped in a volume of 20-30% at a pressure of 8 MPa from the volume of the fracturing fluid, and an oil acid emulsion with the addition of inert gas in a volume of 20-30% at a pressure of 9 MPa of the volume of the proppant is used as a proppant, after which the cycle of pumping the fracturing fluid with gas and proppant is repeated 3- 6 times, and before mastering, a technological fluid with an inert gas is pumped into the tubing string in a volume of 20-30% at a pressure of 10 MPa with a total volume equal to one and a half times the internal volume of the tubing string with subsequent technological exposure for 2-3 , Wherein in each cycle of the fracturing fluid and proppant pumped in equal parts by volume.

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