RU2278251C2 - Method to apply action to production reservoir and walls in wells - Google Patents

Abstract

FIELD: production of liquid and gaseous substances from wells, particularly to treat reservoirs containing oil, gas, water or solutions to clean fluid drainage zone of mud and to create additional cracks in the zone, to clean inner surfaces of pipe or pipe strings inside wells of deposits, rust and scale.

SUBSTANCE: method involves filling well or well part with liquid; initiating blast waves in liquid; injecting aqueous clay suspension containing 10-15% of solid phase in productive reservoir opening interval or in pipe string; holding the suspension at rest to develop strength of coagulation gel structure; repeatedly initiating periodical pressure jumps, namely blast waves in suspension so that pressure jump frequency is enough for full coagulation structure recovery between pressure jumps.

EFFECT: possibility to perform rock fracturing simultaneously with cleaning of reservoir fluid filtering zone.

3 cl, 1 dwg

Description

The present invention relates to the field of production of liquid or gaseous fluids from wells, and more particularly to methods for influencing reservoirs containing, in particular, oil, gas, water or solutions, in order to clean the drainage zone from muds and create additional cracks in it to improve the flow of formation fluids. This technology can also be used to clean the inner surface of pipes and pipe columns in wells from various deposits, corrosion residues and scale.

A known method of stimulating the formation [1], including creating a shock wave in the near-wellbore zone of the well by raising a column of wellbore fluid from the under-packer zone to the over-pack jet pump, followed by communication of the over-packer cavity with the bottom of the well by relieving pressure from the packer.

The common disadvantages of this method include the following:

1) the complexity of its implementation (installing a packer, jet pump, hydraulic units for pumping liquid, etc.);

2) it creates hydraulic fracturing, but is not able to clean it to decolmatize fluid supply channels;

3) lack of efficiency and significant energy costs.

There is a method of increasing oil and gas recovery of productive formations in wells [2], the impact on them of shock waves initiated by electro-hydraulic means. This method as the closest to the claimed adopted by us for the prototype.

The main disadvantages of the prototype are:

1) the complexity of the implementation (the need to supply high voltage to the bottom of the well);

2) a small radius of impact;

3) the depth limit according to hydrostatic conditions, where rupture of the liquid is no longer possible;

4) high power consumption.

The objective of the invention is to be able to produce not only rock fracturing in the vicinity of the wellbore using shock waves, as is the case in the analogue and prototype cases, but also at the same time to realize the effect of clearing the formation fluid filtration zone into the well from muds (clay particles, sand, drop water, insoluble salts, paraffin deposits, etc.).

A separate task is the cleaning in this way of the inner surface of the pipes in the wells from various kinds of deposits.

The tasks are solved by the fact that in the method of influencing productive formations and walls in the well, including filling the well or part of it with liquid and initiating shock waves in it, a clay suspension is pumped into the interval of opening of the productive formation or in a pipe string, the concentration of which is selected from the condition of it flow at the maximum solids content, then leave it alone until the coagulation structure is fully set, after which a shock wave is initiated in it and then the process is repeated uh. In this case, high-colloidal clay or clay powders of the bentonite type are used to prepare the clay suspension, and a dispersed gas phase is introduced into the clay suspension to enhance the compressibility of the medium into the clay suspension.

Initiation of shock waves in a well can be carried out in various ways:

- with the help of a high-voltage electric discharge, launched on the cable;

- by the method of rushing diaphragms mounted on the bottom;

- microexplosions of small explosive charges;

- using the device shown in the drawing, which is called the pulsator.

The device (impulse) consists of a system of pipes (1) interconnected on tapered threads, the column of which descends into the well (2). Washers (3) are installed in the column connectors, having calibrated holes, the passage diameter of which is 0.1 mm less than the diameter of the working balls (4). The distance (1) between the washers (3) is calculated and selected so that the time of the ball (4) to fall after breaking one of the washers onto the next in a viscous and thixotropic medium of a clay suspension is equal to the time of complete restoration of the structure of this suspension. If necessary, the lower washer is replaced by a spider (5) for the possibility of raising the working ball (4) from the well.

The device (impulse) works as follows. It is lowered into the well on a pipe string (detachable or one-piece - such as coiled tubing) and is installed above the formation perforation zone or directly in it.

After lowering the pipe string (1) to the bottom, the clay suspension is injected into the well to the required height, then the working ball (4) is dropped inside the pipe string and it is expected to land on the upper washer (3). After that, using hydraulic units create high pressure in the cavity of the column (1). Under pressure, the ball is forced through a calibrated hole in the washer (3). At the moment the ball is ejected from the hole, a pressure jump occurs - a shock wave that propagates downward and leaves the pipes into the well cavity. The ball at this time drops to the next in order washer and the pulse generation process is repeated.

The distance between the washers must be calculated so that during the lowering of the ball onto the next washer, the structure of the clay suspension in the well has completely recovered (the minimum required time is 10 minutes).

To push the ball through the hole in the washer, the appropriate washer material is selected and the pair is pre-calibrated so that the pressure jump over the ball at the time of pushing does not exceed 3-4 MPa.

The rationale for the implementation of the proposed method.

The effect underlying this method is associated with non-acoustic reflection of shock waves from a rigid wall in a clay suspension medium with a thixotropic-coagulation structure, which has been experimentally proven.

In the bench conditions of the experiments, the following results were obtained:

1. At a mass content of bentonite in water of 6%, the amplification of the incident (direct) shock wave (pressure peak at the wave front) is five times the value of the initial initiating pulse, which was 3.5 MPa.

2. At a mass content of bentonite in water of 10% and 15% according to the records of oscillograms from piezoelectric sensors, amplification of shock waves reflected from a rigid wall was observed. The gain (pressure peak at the wave front) was 8 times for a 10% suspension, 12 times for a 15% suspension of 3 MPa of the initial initiating pulse.

3. When a bentonite suspension was saturated with a gas phase with a characteristic bubble size of ⌀≤1 mm, the amplification effect of the incident and reflected shock waves increased.

4. The experiments also showed a linear dependence of the amplification coefficient of shock waves on the degree of restoration of the thixotropic-coagulation structure of the bentonite suspension. With a completely destroyed structure, the amplification effect disappears, but appears and increases as it is restored.

5. In the experiments, a direct dependence of the shock wave gain on the concentration of the solid phase in the bentonite suspension was found. The effect inherent in this invention is that, ceteris paribus, the nonlinear behavior of the medium is expressed in the amplification of the amplitude of the reflected shock wave relative to the incident one with a coefficient of 1.3-3.

A good example proving the capabilities of the proposed method can be the fact that, after the initiation of the shock wave in the experimental pipe and its repetition, after opening the internal cavity, it was discovered that the sealant, which is extremely strong in adhesion, was detected from the surface of the mounted pressure sensors, as well as rust and scale deposits.

The implementation of the proposed method in downhole technologies

I. Impact on productive objects in the context of the well.

A clay suspension is pumped into the well so that the height of its column overlaps the perforation interval (a system of holes in the casing string of pipes for the formation to communicate with the well), then after holding the suspension at rest, shock waves are initiated at a frequency sufficient to completely restore the coagulation structure (not less than 10 min).

Initiation of shock waves can be carried out, for example, using a garland of small explosive charges released on a geophysical logging cable, or using special devices launched on pipes and exciting shock waves due to a sharp change in pressure drop. In this case, a direct shock wave passes through the perforation holes into the formation and causes a violation of the continuity of the rock, and also reveals the cracks present in it. A shock wave with enhanced amplitude reflected from the pipe walls creates a reverse impulse for particles to move into the well, as a result of which the fluid-conducting channels are cleaned of clogging. After a series of impacts on the formation, the sediment in the well is washed out by conventional washing of the face.

II Pipe cleaning in wells.

To clean the pipe columns from contaminants and deposits on the inner surface, a clay suspension is also pumped into the well and operate according to the above sequence of operations.

The main advantages of the proposed method in comparison with analogues.

1. The analogues do not use the effect of amplification of reflected shock waves and its ability to clean wells.

2. Ease of use of the proposed method.

3. Low cost and high performance.

4. Environmental and technical safety.

Information sources

1. USSR Copyright Certificate No. 973805, cl. E 21 B 43 / 26.1982.

2. Copyright certificate of the USSR No. 636378, cl. E 21B 43 / 26.1978 (prototype).

Claims (3)

1. A method of influencing productive formations and walls in wells, including filling a well or part of it with liquid and initiating shock waves in it, characterized in that a clay aqueous suspension is pumped into the interval of opening of the productive formation or in a pipe string, with a solid mass content in it phase 10 ÷ 15%, then leave it alone until the gel coagulation structure is fully set, after which multiple pressure jumps are initiated in it - shock waves with a periodicity sufficient for complete recovery oagulyatsionnoy structure between pressure surges. 2. The method according to claim 1, characterized in that for the preparation of a clay aqueous suspension using high colloidal clay or clay powders such as bentonites. 3. The method according to claim 1, characterized in that in order to enhance the effect of compressibility of the medium, a dispersed gas phase is introduced into the clay aqueous suspension before injection into the well.