RU2352822C1 - Method of pump operation in pumping fluid into bench - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to oil and gas production industries, namely, to methods of the bench waterflooding bench pressure maintaining and can be used in operation of centrifugal pumps incorporated with bench pressure maintenance systems. The proposed of operation comprises setting the limit parameters and time between routine diagnostics, carrying out a complete diagnostics proceeding from the control over the pump delivery, efficiency, head and consumed power at preset pump operating conditions and carrying repair in case the above parameters depart from the extreme parameters. The time between routine diagnostics is defined in current operating conditions without cutting off the pump and forced variation of the operating conditions. Note here that the efficiency marginal values are determined with due allowance for efficiency drop defined from the pump performances in actual operating conditions. Given the efficiency marginal values are reached, the pump is subjected to a complete diagnostics.

EFFECT: lower costs of complete diagnostics, pump efficient operation, reduced costs of bench pressure maintenance.

5 dwg

Description

The invention relates to the oil and gas industry, and in particular to methods of waterflooding and maintaining reservoir pressure, and can be used in the operation of hydraulic machines, in particular electric centrifugal pumps of the reservoir pressure maintenance system.

A known method of operating an automated cluster pumping station (SPS) (Isaakovich R.Ya., Popadko V.E. Control and automation of oil and gas production. M.: Nedra. - 1985. - 290-293 p.), Which consists in the measurement and control of pressure parameters at the pumping station, control of the electric drives of the pumping station and protection according to the emergency parameter.

The disadvantage is the need for the presence of maintenance personnel at the pumping station to take down the operating parameters of the pumps, the complexity, the complexity, the large errors and the low reliability in determining the current coefficient of performance (COP) of the pump unit, the inability to determine the overhaul period and timing of a full diagnosis.

The closest in technical essence to the proposed method of operating the pump in the process of pumping fluid into the reservoir is the "Test Method for Pump Units and Pump Units" (see AS USSR No. 1634824, F04B 51/00. Publish. March 15, 1991 Bull. . No. 10), which consists in the fact that after the interdiagnostic period, the pressure and energy characteristics of the pump unit are built on the basis of measurements of productivity, pressure and power consumption corresponding to each test mode, the test modes are changed many times.

The disadvantage of this method is the need to bring the pump out of operation after certain interdiagnostic periods, regardless of its operability, multiple changes in the pump operating modes during the test, the inability to determine the timing of the next pump test, which can lead to inefficient operation of the pump or redundancy of tests.

The technical task of the invention is to provide continuous monitoring of the operating condition of the pump, taking into account changes in efficiency, determining the inter-diagnostic period and, as a result, efficient operation of the pump and reducing the cost of conducting full diagnostics.

The stated technical problem is solved by the proposed method of operating the pump, including setting the limit parameters and determining the interdiagnostic period, conducting full diagnostics based on monitoring performance, density of the pumped liquid, pressure at the inlet and outlet of the pump, power consumption, calculating the head, pump efficiency under given conditions pump operation and repair when these indicators deviate above the limit parameters.

What is new is that the interdiagnostic period is determined at the current operating mode during the operation of the pump without stopping and forcibly changing the pump operating modes, adjusting the efficiency limit values taking into account the efficiency drop rate determined from the pump performance at current operating parameters, when the efficiency limit values are reached the pump is subjected to a complete diagnosis.

Figure 1 shows an example of determining the interdiagnostic period.

Figure 2 shows the discrete values of the head calculated at the first full diagnostics at different capacities with the formula of the approximating polynomial of the third degree (analytical dependence), which converts the discrete head values into the initial pressure characteristic of the central pump 63-1400 installed on the KNS-77 NGDU "Jalilneft" .

Figure 3 shows the discrete values of the pump power consumption measured at the first full diagnostics at various capacities with the formula of an approximating polynomial of the third degree that converts the discrete values of the power consumption into the initial energy characteristic of the central pump 63-1400 installed on the KNS-77 NGDU Jalilneft.

Figure 4 shows the discrete values of the pump efficiency calculated at the first full diagnostics at various capacities with the formula of an approximating polynomial of the third degree that converts the discrete values of the pump efficiency into the initial energy characteristic of the central pump 63-1400 installed on the KNS-77 NGDU Jalilneft.

Figure 5 shows an example of the application of the method of operation of the pump in the process of pumping fluid into the reservoir for the central nervous system pump 63-1400 installed on KNS-77 NGDU "Jalilneft".

The method of operation of the pump unit is as follows.

The value of the maximum efficiency of the pump (η _crit. ) _Is entered into the standard computer at the control room (Fig. 1). The value of the maximum efficiency of the pump is determined by standard technical and economic calculation and is calculated as a percentage of the initial efficiency.

At the first start-up of the pump or when it is put into operation after major repairs, a complete diagnosis of the pump is carried out, the pressure and energy characteristics are built, the obtained characteristics are approximated into the analytical dependences of the initial state of the pump H ₀ = f (Q) (Figure 2), N ₀ = f (Q) (Figure 3), η ₀ = f (Q) (Figure 4) using a polynomial of the third degree:

where y _i is the value of one of the functions: head (N), power (N), pump efficiency (η _n );

Q _i - performance;

and ₀ , a ₁ , and ₂ are approximation coefficients, the numerical value of which depends on the pump.

Simultaneously with the complete pump diagnostics using instruments installed on the pumping station, the current pressure at the pump inlet and outlet, the current density of the injected liquid, the current productivity, and the current power consumed by the pump are measured (the current values are averaged over a period of time (for example, 5 minutes) instantaneous values of the measured parameters) and transmit using a telemechanics system to the control room in a standard computer that processes the received data, builds pressure and energy skie pump performance approximates the characteristics according to the initial analytical H ₀ = f (Q) (Figure 2), N ₀ = f (Q) (3), η ₀ = f (Q) (4) when help polynomial of the third degree according to the formula (1). The approximating formulas obtained as a result of a complete diagnosis and processing of the values transmitted by the telemechanics system are compared with each other and, if necessary, a correction factor is introduced to coordinate the readings of the instruments used in the full diagnostics and the instruments installed on the SPS. Obtaining the initial pressure and energy characteristics is carried out only at the first start-up of the pump or at its start-up after major repairs.

Next, the pump is put into operation in accordance with the work task for pumping. According to the telemechanics system, the current values of power consumption (N _t ), productivity (Q _t ), density of the pumped liquid (ρ _t ), inlet pressure (P _tvh ) and output (P _tv ) of the pump are transferred to a standard computer, where the current head value (N _t ), the current value of the net power (N _tp ) and the current value of the pump efficiency (η _tn ) are calculated. The total operating time (hours) of the pump (t _p ) is also taken into account.

The current head developed by the pump is calculated from the measured pressures at the inlet and outlet of the pump:

where N _T is the current head developed by the pump, m;

P _tv , P _tvh - readings of liquid pressure measuring instruments, respectively, at the outlet and inlet of the pump, Pa;

ρ _t - current density of the pumped liquid, kg / m ³ ;

g - acceleration of gravity, m / s ² .

The current useful power of the pump (the total mechanical energy obtained by the fluid flow per unit time) is calculated by the formula:

where N _tp - net power developed by the pump, kW;

ρ _t - current density of the pumped liquid, kg / m ³ ;

g is the acceleration of gravity, m / s ² ;

N _t - the current pressure developed by the pump, obtained by the formula (2), m;

Q _t - current pump capacity, m ³ / s;

1000 is a conversion factor.

The current value of the pump efficiency is determined by the formula:

where η _t is the current value of the efficiency of the pump;

N _tp - current net power developed by the pump, kW, obtained by the formula (3);

N _t - current power consumed by the electric motor, kW;

η _e - the efficiency of the electric motor.

The calculated values of the current pump efficiency (η _ti ) for the current capacity (Q _ti ) are compared with the values of the initial analytical dependence of the pump efficiency for the current performance value (η ₀ = f (Q _ti )) (Figure 1). During the operation of the pump at predetermined (optionally equal) time intervals Δt (for example, hour, day, week - determined based on the pump’s operating coefficient and the volume of pumped liquid) at times t ₁ , t ₂ , t ₃ , ... t _{i the} difference is calculated between η ₀ (Q _ti ) and η _ti (Q _ti ) for the current value of Q _ti (Figure 1). The resulting difference is divided by the time elapsed since the pump unit was put into operation (operating hours), and the efficiency drop rate is obtained:

where υ is the rate of decline in efficiency;

η ₀ (Q _ti ) - the initial value of the pump efficiency for the current capacity;

η _t (Q _ti ) - the current value of the efficiency of the pump;

t _i is the period of time from the moment the pump unit was put into operation (operating hours).

The time of the full diagnosis is determined from the formula:

where T _di is the time point of the full diagnosis (Figure 1);

υ is the rate of decline in efficiency;

η ₀ (Q _ti ) - the initial value of the pump efficiency for the current capacity;

η _crit (Q _ti ) - the limit value of the pump efficiency for the current performance.

In general, the rate of decrease in efficiency depends on many factors (type of pumped liquid, amount of suspended solids in the pumped liquid, pump manufacturing quality, pump operating mode, pump operating time, etc.) and changes during pump operation, therefore full diagnostics (interdiagnostic period) is adjusted in accordance with a change in the current value of the pump efficiency. The limiting value of the efficiency, determined by standard technical and economic calculation and depending on such factors as the price of electricity, the cost of major repairs of the pump, and the rate of decrease in the efficiency of the pump, can also be adjusted.

Consider a general example of determining the interdiagnostic period (Figure 1). Here the points T _p1 , T _p2 , T _p3 are the moments of time for the planned full diagnosis. In operation, the pump capacity is changed, and takes the values Q _T1, Q _T2, Q ... Q _{m3 Ti.} After given (optionally equal) time intervals (at time t ₁ , t ₂ , ... t _i ), the current pump efficiency η _ti (Q _ti ) for the current productivity Q _{ti is} calculated by formula (4). The initial pump efficiency η ₀ (Q _ti ) for the current capacity Q _ti will be calculated by the formula (1). At time t ₁ with a capacity equal to Q _t1 , the initial pump efficiency calculated by formula (1) is η ₀ (Q _t1 ); the limit value of the efficiency determined by the technical and economic calculation as a percentage of the initial efficiency is η _crit (Q _t1 ); calculated on the basis of controlled parameters without changing the pump operating modes according to formula (4), the value of the current pump efficiency is η _t1 (Q _t1 ); the time of complete diagnostics will be determined by the formula (6), this is the value of the point T _d1 (the intersection of line 1 with the line drawn from the point η _crit (Q _t1 )) (Figure 1). At time t ₂ calculated by the formula (4), the value of the current pump efficiency is η _t2 (Q _t2 ). The productivity is equal to Q _t2 and in the general case may not be equal to Q _t1, respectively, the initial efficiency of the pump is determined by formula (1) for the capacity Q _t2 and is equal to η ₀ (Q _t2 ), the limit value of the efficiency will be η _crit (Q _t2 ), and the time of complete diagnostics will be determined by the formula (6), and this is the value of the point T _d2 (the intersection of line 2 with the line drawn from the point η _crit (Q _t2 )) (Figure 1). At point t _{3, the} current efficiency is equal to η _t3 (Q _t3 ), productivity Q _t3 = Q _t1 , therefore, the values of the initial and maximum efficiency are taken equal to η ₀ (Q _t1 ) and η _crit (Q _t1 ), respectively, the time of complete diagnosis is determined by formula (6), and this is the value of the point T _d3 (the intersection of line 3 with the line drawn from the point η _crit (Q _t1 )) (Figure 1). Similar calculations are carried out for any moment in time t _i with the current productivity Q _ti and the moment in time of the full diagnosis T _{di is determined} (Figure 1).

The proposed method of operating the pump in the process of pumping fluid into the formation allows not to carry out full scheduled diagnostics at time points T _p1 and T _p2 , thereby saving material resources, to determine the time of a complete pump diagnosis, eliminating the ineffective operation of the pump with reduced efficiency, since the time predicted full diagnostics (T _di ) according to the proposed method of operating the pump in the process of pumping fluid into the reservoir occurs earlier than the scheduled full oh diagnosis T _p3 (Figure 1).

Let us consider the application of the method of operating the pump in the process of pumping fluid into the reservoir using the example of the central pump 63-1400 installed on KNS-77 of NGDU Jalilneft.

The pump pumps waste water with a density of 1078 kg / m ³ . Before putting the pump into operation, the initial complete diagnostics was carried out, approximating formulas and initial dependences H ₀ = f (Q) (Figure 2), N ₀ = f (Q) (Figure 3), η ₀ = f (Q) were obtained (Figure 4). The limit value of the efficiency was determined by the technical and economic calculation of 94% of the initial efficiency.

Further, the pump was put into operation with the following operating parameters: pump inlet pressure 1.0 MPa, pump outlet pressure 16.0 MPa, pump capacity 50 m ³ / h. According to the passport requirements for the pump pumping wastewater, technical repairs must be carried out after 2160 hours of operation of the pump, and overhaul after 6480 hours, a complete diagnosis is carried out before technical repairs after 2150 hours of operation of the pump.

Figure 5 presents a graph for determining the interdiagnostic period. The time interval for comparing the calculated current efficiency with the initial pump efficiency for the current capacity was determined at 100 hours of pump operation. The initial value of the pump efficiency for a capacity of 50 m ³ / h is 50% (Figure 3), the limit value of the pump efficiency is 47% (94% of the initial value of the efficiency).

During operation of the pump (in the interval from 2000 hours to 4000 hours from the start of operation), the pump performance was increased to 60 m ³ / h, and then (after 4000 hours from the start of operation) was reduced to 50 m ³ / h (Figure 5) . Accordingly, the initial value of the pump efficiency for a productivity of 60 m ³ / h was 55% (Figure 3), the limiting value of the pump efficiency η _crit (Q = 60 m ³ / h) was 51.7% (94% of the initial value of the efficiency at productivity 60 m ³ / h) (Figure 5). The determination of the moment of complete diagnosis for a productivity of 60 m ³ / h is represented by line 2, the predicted time of the full diagnosis T _prog2 (Figure 5). The rate of decline in pump efficiency is variable and varies from 0.015% in 100 hours to 0.05% in 100 hours, however, a complete diagnosis is made after 2150, 4300, 6450 and 8600 hours (at points T _PD1 , T _PD2 , T _PD3 , T _PD4 ) it is impractical, the overhaul (time point T _cr ) after 6480 hours was also considered impractical and was replaced by technical repair, which allowed to reduce the rate of decrease in efficiency (time point T _tr3 ) (Figure 5). A complete diagnosis and the decision to bring the pump to overhaul is planned after 10,000 hours of operation of the pump with a pump capacity of 50 m ³ / h (time point T _prog1 ) (Figure 5).

Thus, the proposed method of operation for the pump under consideration eliminates the need for three complete diagnostics and replaces premature overhaul with the technical one, which saves material resources for three complete diagnostics, reduces the cost of repairing the pump and operates the pump as efficiently as possible without changing the operating conditions.

The technical and economic efficiency of the proposed method of operating the pump during the injection of fluid into the formation is achieved due to the absence of changes in the operating mode of the pump, reduction by 2-3 times of the number of complete diagnostics of the pump, timely determination of the time for complete diagnostics, timely withdrawal of the pump for overhaul.

The use of this proposal allows, at low additional costs, with the help of the existing reservoir pressure maintenance system, to significantly reduce (2-3 times) the cost of conducting complete pump diagnostics, increase the pump operation efficiency (approximately 1.5 times) due to the absence of changes in the pump operating conditions constant monitoring of the technical condition of the pump, determining the interdiagnostic period of the pump, timely output of the pump to overhaul and, as a result, save The cost of maintaining reservoir pressure.

Claims (1)

A method of operating the pump in the process of pumping fluid into the formation, including setting the limit parameters and the interdiagnostic period, conducting a complete diagnosis based on monitoring performance, pressure, power consumption, calculating the pump efficiency (COP) for given pump operation modes and repairing when these indicators above the limit parameters, characterized in that the interdiagnostic period is determined at the current operating mode during operation of the pump without stopping and p inuditelnogo change operating modes by adjusting the limit values considering efficiency rate drop efficiency, determined from the performance of the pump when the current operating parameters, when the limit values of pump efficiency is subjected to complete the diagnosis.

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