RU2265716C1 - Injection well operation optimization method - Google Patents

Abstract

FIELD: enhanced recovery methods for obtaining hydrocarbons.

SUBSTANCE: method involves flooding production bed through injection wells with the use of pump units. In the case of terrigenous porous productive bed flooding acoustical sound resonators with resonance frequency setting are installed in injection line. This eliminates amplitude of alternating low-frequency liquid pulsation sound generated by pump units. Method also involves providing constant compression mode in productive beds and frontal oil drive from productive bed.

EFFECT: increased operational reliability.

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Description

The invention relates to the oil industry, in particular to the field of field development.

A known method of developing injection wells [1]. The essence of this method of developing and increasing the productivity of wells is that a fluid is pumped into the well with a high flow rate and under high pressure, which does not reduce the permeability of the formation. Due to this, cracks open in the bottom-hole zone, pores expand and the plugging material is carried away by the fluid deep into the formation.

In addition, when selling under high pressure due to residual deformation of the formation and some destruction of the surface of the cracks after relieving the pressure, the cracks in some cases are not fully disclosed. Due to this, the permeability of the zone increases against that which was before processing.

The disadvantage of this method is that when the injection pressure is exceeded at the wellhead above the formation, hydraulic fracturing occurs, and the further process of water injection becomes uncontrollable.

A known method of developing injection wells [2] by creating high alternating oscillations at the bottom of the well.

The essence of the method lies in the fact that liquid is periodically pumped into the bottom-hole zone of the formation through tubing pipes using cementing aggregates for a short time until acceptable discharge pressures are reached, which are then quickly discharged through the annulus (“discharge”).

When pumping fluid in the bottom-hole zone of the reservoir, existing ones are discovered or new cracks are formed, and when pressure is released, fluid flows to the bottom at a high speed.

The variable pressure method gives a good effect in conditions of high-strength rocks and relatively high reservoir pressures. When alternating pressures are created, fatigue phenomena occur in the formation rocks and the possibility of formation and development of cracks appears, which leads to an increase in permeability of the bottom-hole zone.

The disadvantage of this method is the risk of damage to the casing string when pressures are exceeded. For this reason, there were frequent cases of failure of wells.

In addition, when creating high values of alternating pressure in the near-wellbore zone of the formation, a network of cracks is formed, which leads to a decrease in the efficiency of the waterflooding process.

The objective of the invention is to increase the efficiency of injection wells, on which:

- no measures were taken to align the injectivity profiles of the reservoirs;

- measures were taken to align the injectivity profiles of the strata.

The problem is achieved by reducing the amplitude of the pulsations of the turbulent fluid flow generated by a centrifugal pump, and smoothly pumping it into productive formations by placing an acoustic resonator in the discharge line.

Comparative analysis with the prototype shows that in the proposed method, the amplitude of the pulsations of the turbulent flow in the liquid is reduced, thereby equalizing the injectivity profiles of the layers.

Thus, the invention meets the criterion of "novelty."

Comparison of the proposed solution with other technical solutions shows that the creation of high alternating oscillations at the bottom of the well is known [2]. However, it is not known that using a resonator it is possible to reduce the sound level, thereby changing the mode of pumping fluid into the formation and align the injectivity profile of the formation.

Thus, the invention meets the criterion of "inventive step".

The proposed solution can be repeatedly used on any injection wells.

Thus, the invention meets the criterion of "industrial applicability".

Physical processes in solving the problem

As a result of suppressing the amplitude of the sound of low frequencies (low-frequency pulsations in the liquid) created by the pumping units, the turbulent flow of the liquid goes into a close to laminar mode. Increases the efficiency of the pumps by reducing the vibration of the pipe body and, accordingly, equalizing the pressure of water injection into the reservoir.

In the first case, the near-wellbore zones of the reservoirs in injection wells, by reducing the pulsations generated by the pump and lowering the injection pressure, maintain a uniform structure.

In the second case, after carrying out work to level the injectivity profiles as a result of pumping all kinds of compositions, the borehole zones of the injection well layers again acquire a homogeneous structure. But with the resumption of water flooding, the injected working solutions are washed out of the clogged cracks and the bottomhole formation zone again acquires an inhomogeneous structure. And the rhythmic pulsation of the pumping units contributes to a large extent to the process of washing out the pumped-in compositions and to the reconstruction of the two-layer model of the PZP. Repeated return to the previous state occurs not only in a qualitative respect, but also in a quantitative one. The fact is that cracks begin to “breathe” and increase in size. In addition, in the process of water injection due to the created alternating low-frequency oscillations, the reservoir is in a stressed state. All this dramatically reduces the effectiveness of geological and technical measures. The latter, as a result, leads to a decrease in the final oil recovery.

The proposed work technology completely eliminates these shortcomings. The cracks remain sealed, which leads to a more complete (piston) displacement of oil from the first reservoir and an increase in the final oil recovery.

In the proposed technology, the reservoir will be in a constant compression mode, which will undoubtedly contribute to an increase in injection volumes with the same injection parameters.

Work technology

Initial conditions - injection objects are represented by terrigenous, feather collectors.

On injection wells:

- no measures were taken to align the injectivity profiles of the reservoirs;

- measures were taken to align the injectivity profiles of the strata.

In the first case, the near-wellbore and remote zones of formations in injection wells represent a single homogeneous geological body. Figure 1 presents the results of the interpretation of the study of injection wells. On figa a homogeneous reservoir, and figb - heterogeneous reservoir.

In the second case, near-wellbore zones of reservoirs (PZP) in injection wells are a heterogeneous geological environment with double permeability - a low-permeability burrow matrix and highly conductive cracks (Fig.1b, where straight line 1 characterizes the state of the near-well zone of the formation, and straight line 2 - the remote zone of the formation).

To implement the method in the first and second cases (pressure lines) of pumping units of the reservoir pressure maintenance system, resonators are used.

The system diagram for implementing the proposed method is presented in figure 2, where 1 is the production casing; 2 - tubing; 3 - resonator, for example a quarter-wave.

Quarter wave resonator

In the practice of noise control in industry, quarter-wave resonators are used. Structurally, it is a pipe closed acoustically rigidly from one end and acoustically softly closed from the other end.

If the pipe is open at one end (x = l) and acoustically rigidly closed at the other end (x = l), then [3]

and the condition for the second end (x = l) gives

Natural frequencies are determined by the expression

where f is the frequency

These resonators have several resonant frequencies.

Calculation Example

It is known that the operation of centrifugal pumps is accompanied by oscillations in the sound frequency range 16 Hz - 20 kHz.

We choose a standard six-meter tubing (tubing). Divide it by 2 m and 4 m, i.e. we get two resonators.

Then, for a four-meter pipe (first resonator) at a speed of sound in a liquid medium of C≈1500 m / s, frequencies (according to formula (4)) are obtained that are absorbed from the spectrum of turbulent noise: the fundamental frequency f = 100 Hz and its harmonics: f≈300 Hz, f≈500 Hz, etc.

For a two-meter pipe (second resonator) at a speed of sound in a liquid medium С≈1500 m / s, frequencies (according to formula (4)) are obtained that are absorbed from the spectrum of turbulent noise: the fundamental frequency f ~ 200 Hz and its harmonics: f≈600 Hz , f≈1000 Hz, etc.

To expand the range of absorbed frequencies in turbulent noise, a set of resonators with appropriate frequencies can be added.

SOURCES OF INFORMATION

1. V.A. Eronin, A.A. Litvinov and others. Operation of the waterflooding system. - M .: "Nedra", 1967. - P.231.

2. F.S. Abdullin. Improving well productivity. - M .: Nedra, 1975.S. 177. [PROTOTYPE].

3. Bored E. Fundamentals of acoustics (translation from German). - M .: Publishing house of foreign literature, 1958.

Claims (1)

A method for optimizing the operation of injection wells, including water flooding through these wells of productive formations using pumping units, characterized in that when watering terrigenous porous productive formations, acoustic sound resonators with a set of resonant frequencies are installed in the injection line to suppress the sound amplitude of alternating low-frequency pulsations of the fluid created pumping units, finding reservoirs in constant compression mode and creating conditions for re ima piston displacement of oil from the reservoir.

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