RU2544944C2 - Method for removing sand-clay plug in well and its development under conditions of abnormally low formation pressures - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: hydraulic hammer is installed on the lower end of a flexible pipe and lowered to a well to a location place of a sand-clay plug. A coiled tubing unit is located on the well head. A bench of foam-forming liquid (FFL) of design length is formed in an axial duct of the flexible pipe. Mechanical action on the sand plug surface is performed by the hydraulic hammer at its movement and pumping through it of FFL benches with further generation of foam in inter-pipe space in each bench by bubbling through it of a bench of gas supplied from the axial duct of the flexible pipe through the hammer. After the plug is removed, development of the well is performed by continuous supply of gas to the axial duct of a flexible string of pipes and by invoking an influx at reduction of pressure below the formation one.

EFFECT: improving efficiency of removal of a sand-clay plug and development of a well.

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Description

The invention relates to the oil and gas industry and may find application in underground, overhaul and well development using coiled tubing installations.

A device for flushing wells with aerated liquids is known (see as.with. No. 1613567, M C. EV 21/00). The device is designed to control the washing process under conditions of washing fluid absorption, depending on the depth of the well and the power of accumulated sludge in the axial channel of the pipe tubing and the wellbore.

A known method of washing sand plugs in the conditions of well repair (see US Pat. RF No. 2.188.304 M class E21B 37/00; 19/22, publ. 08.27.2002).

The washing method is carried out in the following sequence. After installing the coiled tubing unit and the necessary equipment, a flushing fluid with the addition of a surfactant is prepared.

Supply a flexible pipe equipped with a hydraulic nozzle, adjustable speed in the axial channel of the tubing lift column to the location of the sand plug. In this case, the nozzle is above its level. Reduce the feed rate of the flexible pipe V = 0.001 m / s and pump the foaming liquid, with the presence of circulation through the flame of the torch on the flare line. The hydraulic monitor nozzle (destructive tool) is brought to a plug with a low feed rate of a flexible pipe with axial load transfer to the nozzle within Q = 300 ÷ 500 ns.

The steady-state flushing parameters are maintained to control the flushing fluid pressure and axial load. A sand plug is washed with mechanical particles rising from the well at a sufficient upward velocity in the annular space of the well. When using foaming liquids with a high degree of aeration, the upward velocity is assumed to be V = 0.1 ÷ 0.4 m / s. In this case, the injection pressure of the washing liquid is determined from the condition of reducing the fatigue wear of the flexible pipe and should not exceed ΔР = 21 MPa.

When washing a sand plug, the area of the passage section of the nozzle on the flow line is set less than the area of the passage channel of the narrowest section of this line.

After the destruction of the sand plug is completed, the well is flushed with one and a half times the volume of the working fluid from the volume of the axial channel of the pipe lift string and the flexible string is purged with gas, with the well being drilled to the flare line.

The disadvantages of the method include:

- limitation on the throughput of the flexible pipe string due to high hydraulic losses, which reduces the efficiency of the process of destruction of sand plugs and removal of mechanical particles to the surface. This is due to the fact that it is difficult to obtain a high upstream velocity sufficient to transport particles to the surface.

In the case of using multiphase foams as a working agent, which have a greater bearing capacity than liquid, mechanical impurities can be removed, but when pumping the latter along the axial channel of a flexible pipe string, higher hydraulic losses occur, which also reduces the efficiency of the process. It should also be noted that the impact of the foam flow on the surface of the sand cork in order to destroy it has a very low efficiency.

There is a method of direct washing of sand plugs in a well (see AS No. 1.234.576, M class E21B 21/00, publ. 30.05.86, bull. No. 20).

The method is carried out by lowering the pipes to the plug and flushing it through a check valve after building each pipe.

Washing is carried out with partial removal of sand to the surface. The growth of the next pipe is carried out after raising the sand pulp to a height greater in distance, which is the largest sand particle during the time of the pipe building. After washing the sand cork with the full size of the approved pipe, circulation continues until a buffer zone is created from the washing liquid under the weighed sand pulp of the calculated height that prevents particles from settling on the bottom, with the re-formation of the sand cork.

After completion of the screwing, circulation and pipe tolerance are continued. Complete removal of washed-out sand pulp is carried out only after the pipes reach the bottom of the well.

The disadvantages of the method include:

- the complexity of the control process of erosion and removal of sand particles to the surface;

- in the presence of low and abnormally low reservoir pressure, washing liquid is absorbed, which will negatively affect the whole process, since the upward flow rate of washing liquid uncontrollably changes to a smaller side. At the same time, there is a possibility of deposition of mechanical particles and sticking of washing pipes.

After completing the washing process of the sand plug, it is necessary to carry out the well development process. To do this, it is necessary to carry out the killing of the well, with the rise of the flushing pipes.

Re-equipment of the well and its development is carried out as a separate technological operation.

A known method of destruction and removal of sand and clay plugs (see. To the method of removing the problems of operation and overhaul of wells in fields and underground storage facilities. Collection of scientific papers of OJSC "SevkavNIPIgaz". Stavropol: - 2003 S.162-171. Pilot-industrial tests of technology and technical means for the removal of clay sand plugs in the conditions of “ANPP” R. A. Gasumov, V. A. Mashkov, A. A. Singurov and others), adopted as a prototype.

The efficiency of the destruction of sand-clay plugs increases dramatically when using special hydraulic shock devices (see, for example, US Pat. RF No. 2446271 C2 37/00 (2006.01). Publish. March 27, 2012, bull. No. 9).

The hydropercussion device is included in the flexible pipe string of the coiled tubing unit. A pack of foam-generating fluid (POG) with high-pressure gas from a booster unit is fed into the string of flexible pipes.

When pumping the working fluid at the calculated pressure drop, the external crown sharply moves towards the sand-clay plug while maintaining the flow of working fluid to the nozzles of the external impactor. Thus, the hydromonitor effect of the jet of working fluid is used. Due to the ejection of fluid through the axial channel of the seat with a sharp increase in flow, a pressure drop occurs in the axial channel of the flexible pipe string, which leads to the return of the projectiles by the compressed springs to their original position.

RAP was supplied in such a volume so as not to plug the well. The resulting aerated fluid in the annulus of the borehole is a fluid with a lower density than the original fluid, which allows for a hydromonitor effect on the nozzle. Aerated liquid at the exit of the nozzle forms a foam, which allows to increase the effect of washing and removal of mechanical particles to the surface.

Existing methods of foaming allow to realize the technology in full.

The disadvantages of the method include:

- since a sufficiently large volume of aerated fluid is supplied to the well, a column with a hydrostatic pressure exceeding the reservoir is formed in the annulus, which at low reservoir pressure facilitates the penetration of the latter into the reservoir and the deterioration of its filtration characteristics in the bottomhole zone. This situation requires additional work time for well development.

By reducing the hydrostatic pressure in the column of aerated liquid of sufficiently high power by sparging gas through it, in this case it is difficult to obtain foam. This in turn reduces the efficiency of the process of transporting mechanical particles to the surface by an upward flow of aerated liquid.

After washing the sand-clay cork using coiled tubing, it is necessary to carry out the process of development and commissioning of the well.

A known method of well development (see US Pat. RF. No. 2.127.805, M class. EV21B 43/25, publ. March 20, 1999) after drilling and capital repairs. SUMMARY OF THE INVENTION — A tubing string is installed in a well and the well fluid is displaced into the annulus by gas injection. The annular space is closed at the moment the level drops to the tubing shoe.

A portion of the surfactant solution is fed into the tubing string with the creation of a buffer zone while continuing to pump gas until the well fluid is completely aerated in the pore space according to the formula.

A call of inflow is carried out with minimal depressions on the reservoir.

The disadvantages of the method include:

- uncontrolled and incomplete displacement of a portion of surfactants deep into the reservoir with the possibility of a breakthrough of the injected gas in the interlayers with the highest permeability. Thus, complications may arise in the future during well development, since it is difficult to free the bottom-hole zone from the well fluid.

Full carbonation of a sufficiently powerful pack of formation fluid in the bottomhole zone and annulus takes place over a sufficiently long period of time. The inflow of formation fluid from the well by reducing the overpressure in the tubing string is called before the well fluid is carbonated in the pore space of the bottomhole zone when creating a buffer zone from the surfactant solution.

However, forcing a wellbore fluid into a reservoir may lead to a change in the capacitance-filtration characteristics and complications in causing an inflow of formation fluid. At low and abnormally low reservoir pressures, it is more than problematic to master a well in this way due to the presence of high hydrostatic pressure in the annulus.

A known method of well development (see AS No. 1.765.375, M class E21B 43/25, publ. 09/30/92, bull. No. 36).

The invention is implemented by pumping into the annulus of a multi-stage cushion of gas and thickened liquid, bringing it to the shoe of the tubing. At each stage, the pressure of the gas pad exceeds the above column of thickened liquid. Then, air (gas) is discharged with the removal of the above column of thickened fluid from the annulus. This is facilitated by the pressure of the liquid column in the tubing, which exceeds the pressure in the annulus.

The annulus discharge time is controlled by the installation of nozzles or by stepwise stops of the discharge process. The pressure of the liquid column in the tubing exceeds the pressure in the annulus by the amount of excess pressure. During discharge, the fluid moves from the tubing cavity to the annulus. The use of thickened liquid reduces the rate of rise of gas bubbles, which contributes to the existence of piston displacement.

The height of the column of thickened liquid (Nzh) is taken from the condition that the hydrostatic pressure is less than the gas pressure in the air pack.

The disadvantages of the method include:

- it is difficult to control the process, because you have to constantly monitor the height of the pack of thickened liquid. To aerate (foaming) such a large pack of thickened fluid in the annulus of the well in a short period of time seems problematic.

A known method of well development (see AS No. 872.732 M class E21B 43/25, publ. 18.10.81, bull. No. 38).

The essence of the method is the creation of depression on the productive horizon by injection into pipes of gas cushions and squeezing liquid. When developing wells with productive formations having low reservoir pressure and low permeability, after each extrusion of the gas cushion to the calculated depth, the squeezing fluid is discharged, and the released volume of the pipes is again filled with a gaseous agent, which is pressed to the next estimated depth, determined by the mathematical dependence. To separate the squeezing liquid and the gas cushion, a separation plug is placed between them.

The implementation of the method allows to obtain both a smooth and a sharp decrease in level.

According to the authors, it is possible to provide a dynamic impact on the test horizon, which allows for inflow even from formations with low hydrodynamic characteristics, with the possibility of good cleaning of the bottomhole zone and increase production capabilities of the well.

However, the method of well development cannot be applied in wells having a dense sand-clay plug in the axial channel of the pipe tubing string. For this, it is necessary to carry out work on its removal with the re-equipment of the wellhead for its development. This requires additional work time.

The development of the well in batches of liquid and gas, separated by plugs, requires additional operations to remove them from the axial channel of the elevator column to ensure the future production of formation fluid.

Filling the vacant space with high-pressure gas also requires additional working hours, which reduces the efficiency of the development process.

The technical result that can be obtained by implementing the invention is as follows:

- the possibility of alternating supply of packs of foaming fluid and packs of gas through the axial channel of a flexible pipe string equipped with hydraulic hammers, while maintaining a clear structure of the flow of fluids to the location of the hydraulic hammer;

- the possibility of generating shock pulses on the hammer and mechanical impact on the surface of the sand-hydrate plug in the axial channel of the pipes of the lift column;

- the ability to generate foam from each pack of foaming fluid in the annulus of the well by bubbling gas from the pack with the removal of mechanical particles of the destroyed plug to the surface;

- the ability to develop the well after the destruction and removal of the sand-clay plug by continuously supplying gas through the axial channel of the flexible pipe string to the axial channel of the lift column and causing inflow when the gas supply pressure is lower than the reservoir pressure.

The technical result is achieved by the fact that a flexible pipe string is introduced into the axial channel of the pipe tubing string, equipped with a hydraulic hammer, with axial movement and flow of the working fluid inside while maintaining a given depression on the formation.

,As the working fluid, a foaming liquid, for example sulfonol, is used, and the volume of each pack of foaming liquid is determined from the condition for obtaining its minimum length by the ratio

,

where Q is the second flow rate of the foaming liquid, cm ³ / s;

V _W - feed rate of the foaming liquid, cm / sec;

V _belly is the velocity of ascent of gas bubbles in the pack of fluid, cm / sec;

F _mp - the cross-sectional area of the axial channel of the flexible pipe, cm ² ,

moreover, the mechanical impact on the surface of the sand cork is carried out by a hydraulic hammer at the moment of its axial movement and pumping through it packs of foaming fluid with subsequent generation of foam in the annulus in each pack by bubbling through it a pack of gas supplied from the axial channel of the flexible pipe through a hydraulic hammer, and well development , after removing the sand plug, they are carried out by continuously supplying gas to the axial channel of the flexible pipe and causing inflow when the pressure is lower than the reservoir pressure.

When conducting patent research on the scientific, technical and patent literature, we did not find a description of the method in which the destruction and removal of dense sand-clay plugs are combined using coiled tubing, with the sequential supply of packs of foaming liquid and packs of gas through a flexible pipe string. Maintaining the necessary pressure drop on the hydraulic hammer, with the generation of hydrodynamic and mechanical effects on the surface of a dense sand-clay plug, at the time of passing through the device packs of foaming fluid.

No technology was found for alternately supplying a pack of foaming liquid and gas of calculated volumes under equal pressure through a flexible pipe with generation of foam at the bottom of the well while bubbling through each pack of foaming fluid in the annulus of gas from the axial channel of the flexible pipe string and the removal of mechanical particles to the surface along the annular annular the space organized between the inner surface of the flexible pipe string and the outer surface of the flexible pipe string of the coiled tubing installation.

Immediately after the destruction and removal of the dense sandy-clay plug, gas is continuously supplied through a flexible pipe string into the annulus with the depression maintained on the formation and the formation fluid inflow is caused.

Thus, the achieved technical result is due to unknown techniques and a set of techniques aimed at removing mechanical particles from the bottom of a gas well during oil production with preservation of depression on the formation and development of wells in one run ascent using a flexible pipe string of a coiled tubing unit equipped with a hydraulic hammer.

Implementation of the technology for removing a dense sand-clay plug from the axial channel of the pipe lift column and the perforation interval under the conditions of the ANPD is carried out using a flexible pipe of a coiled tubing installation. A hydraulic hammer of known design is installed at the lower end of the flexible pipe (see, for example, Pat. RF No. 2.242.585 M class E21B 37/00; 21/00), and wellhead equipment is mounted.

Fig. 1 - shows the technological scheme of the binding of wellhead equipment with equipment for the implementation of the process.

The well consists of a casing 1, with an elevator pipe 2 in the axial channel. In the axial channel of the pipe tubing string 2, a flexible pipe 3 is passed through the wellhead with a hammer 4 located on a dense sandy clay plug 5. In the axial channel of the flexible pipe 3 there are packs of foaming liquid 6 and packs of gas 7.

A flexible pipe 3 is wound onto the drum of a coiled tubing unit 8 and connected by a connecting pipe 9 to a dispenser - distributor 10, to which a pressure tank 11 is connected, for controlled supply of foaming liquid through the choke 12 to the dispenser - dispenser 10. The pressure tank 11 is connected to a container 13, s stock of foaming liquid.

The compressor 14 is connected by a pressure line 15 with a dispenser - distributor 10. The pressure line 15 is equipped with a safety valve 16 associated with the atmosphere. The annular space 17 between the tubing string 2 and the flexible pipe 3 is connected by a collector 18 with a torch.

The method of washing dense sandy clay cork 5 is as follows.

On the flexible pipe 3 of the coiled tubing unit 8, the hammer 4 is brought to the level of the sand-clay plug 5. From the dispenser-distributor 10, in which the calculated portion of the foaming liquid is accumulated and supplied through the throttle 12 under the influence of the gas pressure supplied through the pressure line 15, a portion of the foaming fluid (POG) through the pipeline through the connecting pipe 9 into the flexible pipe 3 on the drum of the coiled tubing unit 8, from where it is introduced into the well to obtain a pack 6 of foaming liquid of the estimated length. After the first pack of 6 foaming fluids is supplied, a portion of high pressure gas 7 is automatically fed under the same pressure with the burst of pack 6 of foaming fluid being forced through the axial channel of the flexible pipe 3 to the hammer 4. The number of such alternating packs of foaming fluid 6 and packs 7 of gas along the length of the flexible 3 pipes may be several.

When the foaming fluid passes through the hammer 4, the latter generates hydrodynamic impulses with mechanical action on the surface of the dense sand-clay plug 5 and its destruction.

The amount of volume of the foaming liquid in the pack 6 allows for multiple hydrodynamic and mechanical effects on the surface of a dense sand-clay cork with its destruction. Foaming fluid leaving the borehole from the hammer 4 is located in the borehole, a pack of gas 7 subsequently flows out of the hydraulic bumping unit 4 and acts on the foaming fluid in the annulus with its foaming. This ensures the capture of foam mechanical particles obtained by the destruction of the sand-clay cork, 5 and their transportation into the annular space. When the next pack of foaming liquid 6 approaches the hammer 4, hydrodynamic and mechanical impulses are generated again with the impact and destruction of the next section of the sand-clay plug. After the expiration of the pack 6 of the foaming fluid from the hammer 4, the gas flows again from the pack 7 with exposure to the foaming fluid with its foaming and lifting of the mechanical particles by the generated foam along the annulus.

As the sand-clay plug 5 is destroyed, the flexible pipe 3 with the hydraulic hammer 4 is moved down in the axial channel of the pipe riser 2, with tracking the surface of the destroyed sand-clay plug 5.

After removal of the sand-clay plug 5 from the axial channel of the lift pipe string 2, gas is supplied from the compressor 14 to the axial channel of the flexible pipe 3 with exit through the hammer 4 into the annulus between the lift column 2 and the flexible pipe 3.

Foam in the annulus is transported by gas at the wellhead where it is separated (the separator is not shown in Fig.), And gas is supplied through the manifold 18 to the flare for disposal.

Gas is pumped until the foam is completely removed from the annulus with pressure control at the wellhead. A smooth decrease in pressure below the hydrostatic and reservoir pressure causes gas to flow from the reservoir. After that, the flexible pipe 3 with the hydraulic hammer 4 is lifted from the well while maintaining the tightness of the system and the well is put into operation.

, связано с тем, чтобы сохранить четочную структуру ПОЖ потока по всей длине гибкой трубы 3 с доставкой до места расположения каждой пачки ПОЖ до гидроударника 4. Это позволит обеспечить эффективность генерации гидродинамических ударов воздействием на поверхность плотной песчано-глинистой пробки 5.The need to supply the estimated volume of foaming liquid into the axial channel of the flexible pipe with the formation of a packet of the estimated length in it, determined by the formula

, due to the fact that the clear structure of the RLF of the flow along the entire length of the flexible pipe 3 is maintained with delivery to the location of each pack of RLP to the hammer 4. This will ensure the effectiveness of the generation of hydrodynamic shocks by impacting the surface of a dense sandy clay plug 5.

The number of strokes generated by the hydraulic hammer 4 directly depends on the volume of the fluid in each pack 6 and is within n = 5 + 7 pulses.

Such a volume of coolant in each pack 6, after flowing into the annulus 17, forms a layer above the sand-clay plug 5 high enough to effectively purge gas from pack 7 through this layer, with the generation of foam in which mechanical particles are held. Foam with mechanical particles from the destroyed layer of sand-clay cork 5 through the annular space 17 is transported to the surface.

Claims (1)

A method of removing sand-clay plugs in the axial channel of an elevator pipe string at an abnormally low formation pressure using a flexible pipe string equipped with a hydraulic hammer, with its axial displacement and supplying the working fluid inside while maintaining a given depression on the formation, characterized in that as the working fluid a foaming liquid is used, for example, sulfanol, and the volume of each pack of foaming fluid is determined from the condition of obtaining its minimum length when transporting a pack of foaming fluid along a flexible pipe string, moreover, the mechanical impact on the surface of the sand plug is carried out by a hydraulic hammer at the moment of its axial movement and pumping through it packs of foaming fluid with subsequent generation of foam in the annulus in each pack by bubbling through it a pack of gas supplied from the axial channel of the flexible pipe through drummer, and well development after removal of the sand plug is carried out by continuously supplying gas to the axial channel of the flexible pipe string and causing inflow with a decrease in pressure tions below the formation.

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