RU2241818C2 - Method for liquidating complications in wells - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes pumping of fresh water buffer into the well, dispersing water-swelling polymer in fresh water, pushing by fresh water and delay, buffer of fresh water should be in amount no less than amount of water-swelling polymer dispersion, after delay cementing solution is additionally pumped, and concentration of water-swelling polymer in percents in said dispersion is determined in accordance to acceleration of length with complication to be isolated, which is characterized by excessive pressure in MPa at said length when pumping fresh water buffer with productiveness 20 m³/h, accordingly, MPa-% : (15-12)-(0.2-0.3); (12-8)-(0.3-0.5); (8-6)-(0.5-1); (6-2)-(1-5); (2-1)-(5-10); (0.5-1)-(10-30). If length to be isolated contains cracked, cavernous and porous environments and also is subject to excessive pressure of 1-12 MPa filler is additionally injected into cementing solution while pressure on well mouth is constant. Said dispersion of polymer and fresh water for pushing may additionally be injected with filler while pressure on well mouth is constant. Pumping may be performed via tubing pipes, with behind-pipe space closed in the moment of outlet of cement determined by equality of pressure in tubing pipes and behind-pipe space. When isolating a length of low-porous and low-cracked environments with excessive pressure of 15 MPa said water-soluble gelatinous polymer may be used. When isolating watered complications, additionally after buffer of fresh water dispersion of water-soluble polymer in liquid inert to it may be pumped with pumping before or after it of dispersion of first and second buffers of liquid also inert to it, while second buffer contains filler - rubber crumb. When several watered portions are present in layers, multiple pumping of fresh water dispersions of water-swelling polymers is performed and of inert liquid with appropriate buffers.

EFFECT: higher efficiency.

7 cl, 5 ex

Description

The invention relates to the elimination of complications in wells during construction, drilling, operation, repair, refurbishment of oil, gas and water wells.

A known method of isolating absorption zones in the well, including the injection into the well of grouting material based on acrylic polymers and their derivatives [SU No. 1559114, publ. 1990]. These water-soluble polymers are used in water-insulating compositions in combination with electrolytes, forming either sediments (gels) or viscoelastic clogging masses that are stable in the environment of mineralized and fresh waters. However, a “cross-linked” polymer, when pumped into the rock isolation interval, passes through the pores in trickles and acquires their cross-sectional shape, which subsequently does not increase the resistance to water effects.

In addition, the introduction of electrolytes into the polymer solution on the surface makes it difficult to pump it into the well. Consecutive injection of electrolytes and polymer solution to mix them in the reservoir does not bring the desired results.

The closest technical solution chosen for the prototype is a method of eliminating the zones of complications in the well, which includes injecting fresh water buffer, dispersion of water swelling polymer in fresh water, selling fresh water and aging (RU No. 2164594, published March 27, 2001).

Due to insulating work in wells with a depth of 3000 m and more, the injection of an aqueous dispersion of <10% of a water-swelling polymer becomes impossible due to high pressures when selling the dispersion along tubing. The pressure when pumping to a depth of 2500-3000 m can reach more than 400 kgf / cm ² . At these pressures, an emergency occurs. The column is a clogged mass of swollen GNP. Therefore, in such a situation, it is necessary to raise the entire tubing string, squeezing alternately GNP from each pipe. Such an emergency response usually requires 24-48 hours.

It is impossible to apply GNP with a concentration of 10% in fresh water through long flexible pipes (coiled tubing), because high hydraulic pressures occur.

According to the invention, the possible concentration of GNP when applied through flexible pipes with an inner diameter of 38 mm is 0.3-0.5%, which, as practice has shown, does not exceed the working pressure for them of 100-200 kgf / cm ² .

When eliminating catastrophic absorption at shallow depths, for example when drilling under a conductor, a concentration of water-swelling polymer in fresh water of up to 20% may not always be successful, because water flows, high cavernosity leads to dilution of the water dispersion of GNP and the absence of a result as a result.

The objective of the invention is to increase the efficiency of eliminating complications in the well by ensuring the full use of the potential of the swellable polymer to swell. The problem is solved due to the fact that in the method of eliminating complications in the well by isolating the complication site, which includes injecting fresh water buffer into the well, dispersing water swelling polymer in fresh water, pumping with fresh water and holding, the buffer from fresh water should be at least the volume of the specified dispersion of the water-swellable polymer, after exposure, an additional injection of cement mortar is performed, and the concentration of the water-swellable polymer (%) in the specified dispersion is determined in accordance with the injectivity Tew insulated portion complications characterized by excess pressure (MPa) at said portion when injected fresh water buffer with a capacity of 20 m ³ / h respectively (MPa) - (%): (15-12) - (0.2-0.3) ; (12-8) - (0.3-0.5); (8-6) - (0.5-1); (6-2) - (1-5); (2-1) - ( 5-10); (0.5-1) - (10-30).

In the presence of fractured-cavernous and porous media in the insulated area and an excess pressure of 1-12 MPa on it, a filler is additionally introduced into the cement slurry at a constant pressure at the wellhead. In the specified polymer dispersion and fresh water for sale, you can additionally enter the filler at a constant pressure at the wellhead. Injection can be carried out through tubing (tubing), the annulus at the same time overlap at the time of cement output, determined by the equality of pressure in the tubing and annulus. When isolating a portion of finely porous and finely fractured media at an overpressure of 15 MPa, the indicated water-soluble gel-type polymer can be used. When isolating the irrigated area of complications, in addition to the fresh water buffer, it is possible to inject a dispersion of a water-soluble polymer in an inert liquid to it, and before and after this dispersion, the first and second buffers can also inject inert liquid, and a filler, rubber crumb, is introduced into the second buffer.

In the presence of several layer-by-layer irrigated plots, multiple sequential injection of dispersions of water-swelling polymers in fresh water and an inert liquid with appropriate buffers is performed.

Due to the indicated features of the method in which cement mortar is injected followed by filled swellings of a dispersion of water-swelling polymer with buffers, with a break between them in time equal to the time required for the polymer to swell in the well or in the formation until its full potential for swelling is used, taking into account the optimal the choice of the concentration of the water-swellable polymer in the dispersion with respect to the injectivity of the well and the dispersion medium itself, for example fresh water or inert to the water-swellable polymer py medium such as glycerin, synthetic fatty acid esters, glycol esters, alkylphenols, alkylbenzenes, low viscosity oils, etc.

A new qualitative effect is achieved by maintaining the ability of the dispersion of the water swellable polymer to maximize the use of its potential for swelling. The process of swelling of a water-swelling polymer occurs until its full swelling potential is reached, which means maximizing its clogging properties to ensure a reliable barrier screen on the path, for example, water entering the well due to the rising water cone of the bottom water or when isolating the underlying aquifer with washed channels in the annulus through which water enters the oil reservoir.

During the construction, operation of wells, as well as their repair, they face a wide variety of complications: watering wells, fluid flows through the annulus, gaps in the threaded joints of the casing pipes, cracks in the pipes opposite the permeable formations or in intervals, lack of support for the casing, etc. .d.

When eliminating the complications in the wells associated with the manifestation of fluids, they are primarily assessed by the injectivity of the fluid at a certain productivity of its injection. Most often, the liquid is pumped with a capacity of 20 m ³ / h. At the same time, the value of excess pressure on the site of complications or violations of the casing lining, etc., is noted.

Based on the analysis of insulation work materials in the wells, the range of use of the dispersion of the water-swelling polymer was determined taking into account its concentration in the dispersion medium and the pressure in the well when liquid is injected into it with a capacity of 20 m ³ / h.

Of the most widely known polymers on this basis is the AK-639 water-swellable polymer, which is a powder or small particles of a gel. Water-swelling polymer absorbs water to a certain limit, without passing into a fluid state. In this case, the elastic chains and bonds of the molecules unwind and straighten.

The time of complete swelling of the polymer in fresh water with the full use of its potential for water absorption depends on its type, as well as the dispersion of the powder or gel particles.

The average time required to use the full potential for swelling in fresh water for various types, for example AK-639 water-swelling polymer, is:

- for granular - 24 hours (particle size 2 mm);

- finely ground - 16 hours (particle size 0.3 mm);

- for gel - 8-12 hours (particle size 2-3 mm).

The time required for a complete swelling of a water-swellable polymer depends to some extent on the quality of fresh water and the storage time of the polymer. Therefore, before its use, control measurements are carried out and, guided by them, the specified time is set for the complete swelling of the water-swelling polymer in fresh water.

When working to eliminate the complications associated with the isolation of aquifers or flooded formations, data from hydrodynamic studies are used. After processing this data, it is established which type of rock of the medium is to be isolated.

The flow of fluid through a fractured cavernous medium obeys the law:

(1)Q ₁ = K ₁

(1)

The flow of fluid through porous areas occurs according to the law:

Q ₂ = K ₂ Δ P (2)

In the third medium, represented by finely porous, finely fractured media, fluid flow occurs with overcoming the initial pressure gradient by the formula:

Q ₃ = K ₃ Δ P ² (3)

In the above formulas, the notation is as follows:

Q is the fluid flow rate;

DR - differential pressure;

K ₁ ; K ₂ ; To ₃ - pickup factors.

Examples of the application of the method.

Example 1

In the well, a violation of the lining and column section was detected, the injectivity of which when water is pumped through tubing into it using a cementing unit CA-320 with a capacity of 20 m ³ / h occurs at a pressure of 7.0 MPa.

Fluid injection with different capacities showed that the pressure at the mouth changes in direct proportion to the fluid injection rate, i.e. in the well, through violation in the casing lining, it will be necessary to isolate the rock adjacent to it in this interval, which is represented by the second medium - a porous medium according to formula 2.

To eliminate the violation, the first fresh water buffer is pumped into the well with a closed annulus in an amount not less than the volume of water dispersion of the water-swelling polymer injected after it, then the second buffer from fresh water. When half the volume of the aqueous dispersion of the water-swellable polymer was injected, the pressure at the mouth did not change. Therefore, in the second part of the aqueous dispersion of the water-swellable polymer and in the second buffer, fillers of the type of fine rubber crumb are introduced, in addition to rubber crumb, crushed waste of automobile tires, crushed waste of rubber products, cord fiber, etc. can also be used. The aqueous dispersion of the water swellable polymer extrudes into the disturbance interval. After that, the well is closed for a time sufficient to ensure complete swelling of the polymer in the well.

The total swelling time of a polymer such as AK-639 depends on the brand of product. For example, a granular water-swellable polymer is taken.

Preliminary control measurements found that for granular AK-639 this time was about 24 hours

After sustaining the time required for the swelling of the water-swelling polymer in the well, the cement is injected. Initially, the injection is performed with the annulus open. When, according to the calculation, the pressure of the liquid columns in the tubing is equal to the pressure of the liquid column in the annulus, it is shut off, but according to the calculation, the cement mortar should be at the outlet of the tubing.

The cement slurry is forced into the disturbance interval without any intermediate portion of water in the isolation interval.

The amount of water-swellable polymer for the preparation of cement dispersion was selected based on practical experience in this oil region.

Example 2

In the well, the disturbance is represented by a large crack, through which the fluid passes behind the column into the fractured rocks. The injectivity of these rocks is presented by the following data. When water is pumped through it with a capacity of 20 m ³ / h, the pressure at the wellhead rises to 13.0 MPa.

To eliminate the violation, an aqueous dispersion of a water-swelling polymer with a concentration of 0.3 and a cement mortar without fillers are pumped into the well according to the same scheme as in Example 1. The difference is that in this case a packer with a retractable central pipe is used. The buffer, the dispersion of the water-swellable polymer and the buffer are injected with a nozzle inserted into the packer.

The whole composition is squeezed as calculated below the packer. Then the water-swellable polymer is aged over time.

The tubing is lifted so that the central pipe leaves the packer. At the same time, the valve closes in the packer.

In this position, with an open annulus, cement mortar is pumped into the pipes. By calculation, it is forced to exit from the central pipe. After this, the pipes are allowed down. The central nozzle enters the nozzle, opens the valve, and the cement slurry is forced into the under-packer space. The operation ends after the cement grout is pushed and the central pipe from the packer is lifted.

Example 3

The well was partially flooded due to the approaching water from the contour water flooding. The injectivity of the well when injecting water into it was determined as follows: when injecting water with a productivity of 20 m ³ / h, the pressure at the wellhead was 2.0 MPa.

Pickup is very intense. Therefore, a water-swelling polymer of a high concentration of 10% in a liquid inert to it, for example, in technical glycerin, was used. It is assumed that in the water-saturated part the water-swelling polymer will swell, and where at least part of the oil is located, it will remain neutral and will be washed during development.

As in example 1, fresh water buffers are pumped before and after the water swellable polymer. It is assumed that fresh water buffers will enter the flooded canals, as they will be prevented from entering the oil channels by the large difference in their surface tension.

Further insulating work is consistent with the scheme in 1 example.

Example 4

When drilling under a conductor near the surface, an aquifer with karst cavities was opened.

The injectivity of the well is characterized as follows.

When water is injected into the well with a capacity of 20 m ³ / h at the wellhead, the pressure is in the range of 0-5 MPa.

To eliminate the absorption, a stream of fresh water is directed into the open hole of the well. First, a buffer is pumped, then, under a stream of water or through an ejector, a water-swelling polymer with a concentration in the range of 20-30% is introduced into it. After the introduction of the aqueous dispersion with the water-swellable polymer in the operation, a temporary break is made for the polymer to swell until its full potential for swelling is used. After a break, cement slurry is pumped into the well.

Example 5

In the well, it is necessary to isolate the interval at which water injection occurs only after application of an excess pressure of 5.0 MPa.

At the beginning of the operation, the injectivity of the well was determined when water was pumped into it with a capacity of 20 m ³ / h. During the study, the following filtration mode was established: when water was pumped with a capacity of 20 m ³ / h, the pressure at the mouth was set at 15 MPa.

The complication is eliminated according to the usual scheme, as in examples 1, 2, but an aqueous dispersion of a water-swelling gel-type polymer with a concentration in the range of 0.5-1.0% (in terms of dry matter) is used. Moreover, the injection of an aqueous dispersion of a gel water-swelling polymer is performed at a pressure exceeding the initial pressure gradient at which the well begins to receive fluid.

The technical and economic effect of the proposed method is to ensure reliable elimination of complications during various types of work in the well: during construction, operation and repair of wells, significant savings in grouting materials and time.

Claims (7)

1. A method for eliminating complications in a well by isolating a complication site, including injecting a fresh water buffer into a well, dispersing a water-swelling polymer in fresh water, pumping with fresh water and holding, characterized in that the fresh water buffer must be at least equal to the volume of the specified dispersion water-swellable polymer, after exposure, an additional injection of cement mortar is performed, and the concentration of water-swellable polymer (%) in the specified dispersion is determined in accordance with the injectivity of the insulated area complications characterized by excessive pressure (MPa) in the indicated area when injecting a fresh water buffer with a capacity of -20 m ³ / h, respectively, (MPa) - (%): (15-12) - (0.2-0.3); (12-8) - (0.3-0.5); (8-6) - (0.5-1); (6-2) - (1-5); (2-1) - (5-10); (0.5-1) - (10-30). 2. The method according to claim 1, characterized in that in the presence of a fractured-cavernous and porous media in the insulated area and an excess pressure of 1-12 MPa on it, a filler is additionally introduced into the cement mortar at a constant pressure at the wellhead. 3. The method according to claim 1 or 2, characterized in that the filler is additionally introduced into said polymer dispersion and fresh water for sale at a constant pressure at the wellhead. 4. The method according to claim 1, characterized in that the injection is carried out through tubing, the annulus is blocked at the time of cement output, determined by the equality of pressure in the tubing and annulus. 5. The method according to claim 3, characterized in that when isolating a portion of finely porous and finely fractured media at an overpressure of 15 MPa, the indicated water-soluble gel-type polymer is used. 6. The method according to claim 1, characterized in that, when isolating the irrigated plot of complications, in addition to the fresh water buffer, a dispersion of a water-soluble polymer in an inert liquid is pumped with, and before and after this dispersion the first and second buffers are also inert liquid, and a filler, rubber crumb, is introduced into the second buffer. 7. The method according to claim 6, characterized in that in the presence of several layer-by-layer irrigated plots, multiple sequential injection of dispersions of water-swelling polymers in fresh water and an inert liquid with appropriate buffers is performed.