RU2429382C1 - Downhole pump plant - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed plant comprises motor connected via downhole cable line to surface control station with frequency converter, radial-flow pump a with inlet 1 and at least one pump section c. Said section features lower delivery compared with that of pump a at zero head and is arranged in series with radial-flow pump a. Additional section inlet 2 and outlet 3 are communicated with hydraulic channel accommodating at least one check valve b with operating pressure threshold not exceeding preset adjustment accuracy.

EFFECT: higher efficiency in wells with major variations of local water inflows.

2 cl, 5 dwg

Description

FIELD OF THE INVENTION

The invention relates to the oil industry, and in particular to submersible equipment for oil production, in particular to submersible centrifugal pumping units used for wells with large fluctuations in the flow of formation fluid.

State of the art

Currently, to increase the efficiency of oil production, various methods of influencing the oil reservoir, such as hydraulic fracturing, are increasingly being used. The permeability of the formation increases and, as a result, the influx of production wells increases.

At the same time, over time, the transfer of mechanical impurities by the flow of the formation fluid leads to a decrease in the permeability of the formation, and the productivity of the wells decreases. Thus, there is a fluctuation in the inflow of the well, which can be very significant, for example, from 500 m ³ / day to 150 m ³ / day.

Submersible electric pumps - for oil production, with such a wide working area, does not exist. This circumstance is confirmed by the catalog data for submersible pumps of the largest Russian manufacturers, for example, Alnas. The narrowness of the working area of centrifugal pumps leads to a significant number of ORS associated with the replacement of the unit size due to improper selection. According to Schmidt's dissertation work (see Shmidt S. A. Research of unsteady operation of the “reservoir-well-ESP” system. Thesis for the degree of candidate of technical sciences, Samara, 2000), the number of such plant lifts is 15% of the total the amount of ORS. If, at feeds lower than the left boundary of the working zone, the discharge flow characteristic is monotonously decreasing, then when the pump is operating on a single-phase liquid, it is possible to expand the pump working zone to the left side by reducing the requirements for efficiency and resource indicators, which in some cases could would have economic feasibility.

When operating a submersible centrifugal pump in a gas-liquid mixture, which occurs in the vast majority of cases in the fields, this expansion is not always possible. This is due to a decrease in the density of the gas-liquid mixture in the channels of the impeller of the centrifugal pump, caused by the relative movement of the phases. The reason for the relative phase motion is the drift of the gas phase in the direction opposite to the direction of the field of mass forces, i.e. from the periphery to the center of the wheel.

A known installation (see Shengur N.V., Kulikov A.T. Submersible pump installation. RF patent RU 2211379, published on 08.28.2003), which contains kinematically connected pumps. The first of the pumps is made in the form of a centrifugal pump, kinematically connected to the shaft of a common drive motor and connected by a suction pipe to the annulus of the well, and a discharge pipe to the suction pipe of a second single-screw pump. A single screw pump is connected by a discharge pipe to a pressure pipe. The pumps are hydraulically connected in a pipeline. The nominal feed of the centrifugal pump exceeds the nominal feed of the single-screw pump by at least the amount of leakage in the latter. A significant drawback of the analogue is that with a significant difference in the nominal flows of single-screw and centrifugal pumps, a single-screw pump becomes a throttle for a centrifugal pump.

As a prototype, the technical solution described in the scientific and technical journal "Oil of Russia" was selected. - 2006. - No. 1. Pages 62-64 (Kudryashov S.I., Zdolnik S.E., Sakhno N.V., Markelov D.V., Ivanovsky V.N., Ivanov A.A., Ovodkov O.A. submersible high-speed installations with an adjustable electric drive) - a submersible pumping unit for oil production, containing a submersible electric pump, with the possibility of changing the rotational speed, containing an electric motor connected in series on a single transmission, connected via a cable cable to a ground control station with a frequency converter, hydraulic protection, input bottom module and centrifugal pump. Such an installation has an ascending branch of the pressure-flow rate characteristic of a centrifugal pump at feeds lower than the left boundary of the pump working zone, which impedes efficient operation of the pump in wells with large fluctuations in the flow of formation fluid.

Disclosure of invention

The main technical result of the invention consists in the development of pumping units for wells with large fluctuations in the flow of formation fluid by eliminating the ascending branch of the discharge flow characteristic of the centrifugal pump at feeds lower than the left boundary of the pump working zone, and regardless of the physical reasons giving rise to the indicated branch (" hump ”) on the discharge flow characteristic of the pump.

To achieve the technical result, a submersible installation with an adjustable electric drive has been developed, containing an electric motor connected through a cable line to a ground control station with a frequency converter, a centrifugal pump, different from the known one, that it contains at least one additional pump section with a smaller than that of a centrifugal pump, with a capacity at zero head and located in series with a centrifugal pump, the input and output additionally sections associated hydraulic channel, in which is set, at least one check valve with a threshold of pressure that does not exceed a predetermined control accuracy. The installation of a submersible electric pump may contain two or more additional pump sections, the input and output of each of which is connected by a corresponding hydraulic channel in which at least one non-return valve is installed, and each subsequent additional section has a lower productivity than the previous additional section at zero pressure.

Brief Description of the Drawings

Fig 1 illustrates the effect of the appearance of a "hump" on the HPX (pressure-flow characteristic), known in pump submersible equipment, using the example of a serial pump 2 VNNP5-50.

Figure 2 is a diagram of a submersible installation according to the claimed invention.

Figure 3 - considered the discharge characteristics of the centrifugal pump of the additional pump section and the total.

Figure 4 illustrates the features of maintaining a critical dynamic level during the operation of the well.

Figure 5 shows how the pressure threshold of the check valve determines the accuracy of pressure control.

The implementation of the invention

The influence of the relative phase movement on the “negative” deformation of the pressure-discharge characteristic of the pump at feeds lower than the left boundary of the pump working zone is well illustrated, for example, by the results of an experimental study conducted in the dissertation work of L. Igrevsky (see Igrevsky L.V. Improving the operational efficiency of submersible pump-ejector systems for oil production. The dissertation for the degree of candidate of technical sciences, Moscow, Russian State University of Oil and Gas named after IM Gubkin, 2002). Figure 1. The experiments were carried out at various gas contents at the intake of a 22-stage pump 2VNNP5-50.

Figure 1 shows that when the centrifugal pump operates on a gas-liquid mixture in the left zone of the pressure-flow characteristic, an “ascending” branch is formed even for the pump, which does not have a “hump” on the characteristic when working on a single-phase fluid.

Tables 1 and 2 show data from the catalog of the largest Russian manufacturer of submersible pumps - the ALNAS plant, which show that modern submersible electric pumps are oil pumps for efficient operation in a well with fluctuations in well inflows, which can be very significant, for example from 500 m ³ / day to 150 m ³ / day.

Table 1 Pump Submission to the slave. zone, m ³ / day Head max., M Max. Cons. power, kWt Efficiency% ETSNA (C) 5-18 12-30 2600 20.7 26 225 (226) ETsNAK5-25 15-45 3400 34.68 28 225 (226) ETSNAKI 5-25 15-45 3350 34,20 28 ETSNA (C) 5-30 20-40 2500 23.9 35 ETSNA (C) 5-45 12-70 2600 35,4 39.7 225 (226) ETsNAK5-45 15-70 2500 35.08 37 225 (226) ETSNAKI 5-45 15-70 2400 33.39 37 ETSNA (C) 5-60 35-80 2550 39.7 44 225 (226) ETsNAK5-60 35-80 2350 35,2 46 225 (226) ETSNAKI 5-60 35-80 2000 29.6 46 ETSNA (C) 5-80 60-115 2600 45.7 51.5 225 (226) ETsNAK5-80 60-115 2500 46.5 50,0 225 (226) ETSNAKI 5-80 60-115 2200 39.78 50,0 ETSNA (C) 5-125 102-165 2400 57.6 58.5 225 (226) ETsNAK5-125 102-165 2300 60.1 53 225 (226) ETSNAKI 5-125 102-165 1950 51.87 53 ETSNA (K) 5-200 150-265 1750 79.3 fifty 225 (226) ETsNAK5-200 150-265 1750 78.59 fifty 225 (226) ETSNAKI 5-200 150-265 1700 107.09 fifty 225 (226) ETsNAK5A-25 10-50 3300 34.12 27.5 225 (226) ETsNAKI 5A-25 10-50 3250 33.77 27.5 ETSNA (K) 5A-50 25-80 2450 35.52 39.5 225 (226) ETsNAK5A-50 25-80 2950 44.38 36

table 2 Pump Submission to the slave. zone, m ³ / day Head max., M Max. Cons. power, kWt Efficiency% 225 (226) ETsNAKI 5A-50 25-80 2900 46.05 36 ETSNA (K) 5A-80 35-110 2250 43.15 48 225 (226) ETsNAK5A-80 35-110 2750 59,4 42 225 (226) ETsNAKI 5A-80 35-110 2700 58.40 42 ETSNA (K) 5A-125 75-190 2050 57.73 54 ETSNA (K) 5A-160 125-205 2500 74.16 61 225 (226) ETsNAK5A-160 125-205 2650 79.72 61.0 225 (226) ETsNAKI 5A-160 125-205 2600 77.76 61.0 ETSNA (K) 5A-200 112-262 2250 94.89 54 ETSNA (K) 5A-250 195-340 2350 107.95 61.5 225 (226) ETsNAK5A-250 195-340 2050 94.63 61.5 225 (226) ETsNAKI5A-250 195-340 2300 105.42 61.5 ETSNA (K) 5A-400 300-440 1550 119.12 59.5 225 (226) ETsNAK5A-400 300-440 1450 109.59 59.5 225 (226) ETsNAKI5A-400 300-440 1550 117.63 59.5 ETSNA (K) 5A-500 430-570 1500 155.65 54.5 225 (226) ETsNAK5A-500 430-570 2050 214.42 54.5 225 (226) ETsNAKI 5A-500 430-570 2000 208.80 54.5 ETSNA (C) 6-800 550-925 1100 167.02 60 225 (226) ETsNAK6-800 550-925 950 163.2 56 225 (226) ETSNAKI 6-800 550-925 950 163.2 56 206ETSNAK6-1000 840-1200 1850 352.1 60 206ETSNAK6-1250 1100-1540 1400 361.2 56 205 (206) ETsNAK8-2000 1500-2500 1500 579 60

The essence of the invention consists in eliminating the ascending branch of the discharge flow characteristic of a centrifugal pump at feeds lower than the left boundary of the pump working zone, and regardless of the physical reasons giving rise to a “hump” in the discharge flow characteristic of the pump. At the outlet of the centrifugal pump, an additional pump section is installed with a lower capacity than that of a centrifugal pump with a zero head and a steeply falling pressure-flow characteristic for feeds smaller than the left boundary of the centrifugal pump working zone. The inlet and outlet of the additional pump section are connected by a hydraulic channel in which a check valve is installed.

The above is illustrated in FIGS. 2 and 3. In FIG. 2:

 a - centrifugal pump;

b - non-return valve with a pressure threshold that does not exceed a predetermined control accuracy;

c - an additional pump section with a lower capacity than a centrifugal pump at zero pressure.

The numbers indicate the characteristic points of the flow of formation fluid:

1 - input of a centrifugal pump;

2 - the output of the centrifugal pump and the input of the additional pump section and the entrance to the hydraulic channel, in which a check valve is installed with a pressure threshold that does not exceed the specified control accuracy;

3 - output of the additional pump section and exit to the hydraulic channel.

Figure 3 shows the discharge characteristics of the centrifugal pump (line A), the additional pump section (line B) and the total characteristic (line C).

Consider the case where the feed at the intake of the centrifugal pump (point 1) is less than the feed of the additional section at zero pressure. 3, such a feed is designated as Q1. Since the additional section creates a pressure, the pressure at point 3 will be higher than the pressure at point 2 and, therefore, the check valve in the hydraulic channel will be closed. In other words, at a given feed, a centrifugal pump receives a serial connection between the centrifugal pump and the additional section. With this connection scheme, the pressures developed by the centrifugal pump and the additional section are added.

An increase in the supply at the centrifugal pump intake before the additional section is supplied at zero pressure (Q2) leads to equal pressure at points 2 and 3. The check valve in the hydraulic channel opens. After opening the check valve between points 2 and 3, there is a parallel connection of the additional section and the check valve, in which the flow through each element is inversely proportional to the hydraulic resistance of the elements.

Therefore, in the case when the resistance of the hydraulic channel is much less than the resistance of the additional section, a further increase in the feed rate at the intake of the centrifugal pump (point Q3 in FIG. 3) leads to the fact that the pressure-flow characteristic of the “centrifugal pump - additional section” assembly coincides with pressure-flow characteristic of a centrifugal pump. (N is the pressure of the pump assembly).

Any centrifugal pump has a restriction on the volumetric flow rate of gas at the intake, which is proportional to the pressure at the intake of the pump, i.e. an increase in pressure leads to a decrease in gas content. On the other hand, increasing the pressure at the pump inlet increases the bottomhole pressure and, naturally, reduces the flow rate of the well. Thus, the maximum flow rate of the well is achieved with a certain pressure at the pump inlet, which corresponds to a certain dynamic level - a critical dynamic level (NCR). As noted above, during the operation of the well, its parameters can vary quite significantly, which leads to a deviation of the dynamic level from the initially critical level. Figure 4 illustrates such deviations, for example, when reducing well productivity.

Let the submersible pump operate at frequency n2 in the optimal mode with the well productivity coefficient, which corresponds to the indicator line K2 (point 1). An increase in well productivity to the value corresponding to the indicator line K3 leads to the fact that the pump operating mode shifts to point 2 and the dynamic level becomes less than critical. In this case, the flow rate Q of the well increases from Q2 to Q3, but does not reach the maximum possible value of Q4. You can switch to the operating mode with the optimal dynamic level and, accordingly, with the maximum possible well production by changing the frequency mode from n2 to n3.

The decrease in well productivity from the initial to the value corresponding to the indicator line K1 leads to the fact that the pump operation mode is shifted to point 4 and the dynamic level becomes large critical and the pump feed is interrupted. You can avoid this negative situation by changing the frequency mode from n2 to n1.

Thus, it follows from the above that maintaining a critical dynamic level (or, which is the same thing, pressure at the pump intake) during the operation of the well is an extremely important task. This circumstance imposes stringent requirements on the accuracy of pressure regulation, the increase of which to the required level can be limited by the threshold of the check valve. In this regard, the conditions imposed in the claims on the sensitivity threshold of the check valve are very significant.

Previously, the operation procedure of the inventive device with an “ideal” check valve was described, i.e. not having a pressure threshold. Figure 5 illustrates how the pressure threshold of the check valve determines the accuracy of pressure control.

When performing this submersible installation, a rotary vortex pump can be used as an additional pump section, and a ball check valve as a non-return valve.

Claims (2)

1. Installation submersible with an adjustable electric drive, comprising an electric motor connected through a cable line to a ground control station with a frequency converter, a centrifugal pump, characterized in that it contains at least one additional pump section with a smaller than that of a centrifugal pump, capacity at zero pressure and located in series with a centrifugal pump, and the input and output of the additional section is connected by a hydraulic channel in which at least e, one non-return valve with a pressure threshold that does not exceed a predetermined control accuracy. 2. Installation of a submersible electric pump according to claim 1, characterized in that it contains two or more additional pump sections, the input and output of each of which is connected by a corresponding hydraulic channel in which at least one of the specified non-return valves is installed, with each subsequent additional the section has less productivity than the previous additional section at zero head.

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