RU2395723C1 - Method of operating pump unit in injection of fluid into formation - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: pickups are used to control the following parametres: pump rpm, fluid density, viscosity and temperature, pump head allowing for pressure difference and fluid density, pump flow rate allowing for fluid temperature and viscosity and efficiency allowing for fluid viscosity. All parametres averaged for preset time interval are controlled simultaneously in real time mode. In case one of the parametres falls beyond tolerances during said time interval, pickups controlling said parametres are inspected and/or repaired. Pump unit is inspected and repaired in case measured parametres fall beyond bottlenecks.

EFFECT: higher efficiency due to prompt pinpointing of in valid readings of said pickups.

6 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 a system for maintaining reservoir pressure (RPM).

The modern RPM system is a complex engineering structure, which is characterized by a significant capacity of pumping units (ON), which operate in various modes for pipeline networks with varying parameters (shutdown and connection of wells of different injectivity in various combinations, varying injectivity of wells) with various, including and aggressive, fluid having a variable density, therefore, monitoring the current state of HA is necessary to ensure the efficiency of the RPM system as a whole.

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 measuring and controlling pressure parameters at the pumping station, controlling 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 remove the operating parameters of the pumps, the complexity, the complexity, the large measurement errors of the parameters of the ND due to the long period of time between measurements.

Also known is the "Test Method for Pumping Units and Pumping Units" (AS USSR No. 1634824, F04B 51/00, published on March 15, 1991 Bull. No. 10), which consists in the fact that after the interdiagnostic period, pressure and energy are built On-line characteristics based on measurements of productivity, pressure and power consumption, corresponding to each test mode, repeatedly change the test modes.

The disadvantage of this method is the need to bring the pump out of operation after certain interdiagnostic periods, regardless of its performance, repeated 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 pump operation or redundancy of tests and, as a result, to large non-productive material costs.

The closest in technical essence to the proposed method of operating the pump during the injection of fluid into the reservoir is the "Method of continuous measurement and analysis in real time of the efficiency of the pumps in the pumping and piping complex of the main pipeline" (RU No. 2277186, F04D 15/00, publ. May 27, 2006, Bull. No. 15), which consists in the fact that the current values of the pressures at the inlet and outlet of each ON and the active electric power of their drive electric motors are fed through the telemechanics system to the control room tubing pipeline system. Using pressure sensors, the inlet pressure of each pump is measured. Electric power counters - the value of the consumed active electric power with the number of the operating ON, the outputs from which are fed through the telemechanics system to the dispatching console, where they calculate for each ON the power acting on the pump shaft, the pressures generated by each pump, the consumption coefficient of ON, operating coefficient ND, characterizing the deviation of the actual operating characteristics from the nominal, and the volumetric flow rate of the fluid created by the pump. According to the average value of the flow rate, the daily data obtained are analyzed to determine the continuous stationary operation of the ON by flow rate for at least four hours when the flow rate fluctuates within three percent of the average value and the average base and current values of the pump efficiency and efficiency are calculated from them and compare current values with the baseline. The obtained current values are received for storage in a computer, according to which a continuous analysis of the state of the complex is carried out, for which graphs of the values of flow rate and efficiency are constructed at the current operating mode of the scientific research at all pumping stations for a controlled period of time. The data is compared with the previous values stored in the computer memory, for each ON as well as for adjacent pumping stations, and if these values of any ON working in the nominal mode are lower than the basic values, then a decision is made to switch the operating ON on the other with its further inspection and repair.

The disadvantage of this method is the determination of the flow rate by calculation and the inability to control the reliability of the sensor readings, which leads to instability in determining the technical condition of scientific equipment in conditions of constantly changing operating modes of scientific equipment, the inability to analyze the influence of various factors on the technical state of scientific equipment. In the case of false sensor readings, the error in determining the head, flow rate and efficiency will be significant, which can lead to redundancy of inspections of the scientific equipment, its inefficient operation and large non-productive material costs.

The technical task of the invention is to expand the functional capabilities of the operation of HA by providing constant monitoring of the reliability of the readings of pressure, flow, temperature, density, viscosity of the pumped liquid during operation of the pumping unit, power consumption and determining the current efficiency, including with constantly changing modes work on and, as a result, a timely response to changing conditions and the effective operation of the pump unit.

The stated technical problem is solved by the proposed method of operating the pumping unit, which includes monitoring by the sensors the parameters: flow rate of the pumped liquid, pressure difference at the inlet and outlet of the pump, power consumption of the pumping unit; determination of the efficiency of the pumping unit, based on controlled parameters, regulation of the operating mode of the pumping unit within the permissible working area; inspection and repair of the pumping unit while reducing the efficiency below a predetermined critical value.

What is new is that the sensors additionally control the parameters: frequency of rotation of the pump shaft, density, viscosity and temperature of the fluid pumped through the pump unit, determine the pressure created by the pump unit based on the pressure drop and fluid density, the flow rate of the pump unit based on temperature and viscosity liquid, and the coefficient of performance - taking into account the viscosity of the liquid, while all parameters averaged over a specified time interval are monitored simultaneously in real time If the values of one of the parameters, during this period, do not coincide with other parameters and exceed the limits of certain allowable values calculated taking into account the pressure drop and the efficiency of the pump unit during operation, the sensor measuring this parameter is inspected and / or repaired and inspection and repair of the pumping unit is carried out with a coordinated exit of the measured parameters beyond the critical values.

Figure 1 shows the pressure characteristic for the example of the central nervous system 63-1400 pump (pressure dependence on flow) obtained during the first diagnosis of the pumping unit after installing it on the pumping station.

Figure 2 shows the energy characteristic (the dependence of the power consumed from the network on the flow rate) using the example of the central pump 63-1400, obtained during the first diagnosis of the pump unit after installing it on the pump.

Figure 3 shows the dependence of efficiency on flow rate by the example of the central nervous system pump 63-1400, obtained during the first diagnosis of the pumping unit after installing it on the pumping station.

Figure 4 shows the dependence of the pressure and flow rate on the power consumption by the example of the central pump 63-1400, obtained during the first diagnosis of the pump unit after installing it on the pump.

Figure 5 shows a graph of the change in efficiency over time for the General case of central nervous system pumps.

Figure 6 shows the dependence of the current, initial and critical values of efficiency on flow rate using the example of the central nervous system pump 63-1400.

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

The control panel (PU) (for example, a standard computer, digital station, etc.) of the control room records the permissible deviations of the current flow rate, pressure, power consumption and critical values of pressure, flow rate and efficiency. The permissible deviations of the current values are determined from the specific operating conditions of the ON, pressure pulsation, uneven supply of liquid to the input of the ON, voltage surges in the network, etc. The critical values of the parameters are determined from the technical documentation of the scientific equipment, the requirements of GOST, safety rules, etc. taking into account the economic efficiency of operating NA.

During the first start-up of the pump or during its commissioning after major repairs, a complete diagnosis of the pumping unit is carried out, the current flow rate, pressure at the pump inlet and outlet and the current power consumed by the pumping unit at various flows, current density, temperature and viscosity of the injected fluid (as the current values are taken as averaged over a certain period of time (for example, 5-10 minutes) the instantaneous values of the measured parameters), the received data is transmitted using a telemechanics system PU control station, which processes the received data, builds the pressure and the pump power characteristics approximates the characteristics according to the initial analytical H ₀ = f (Q) (1), N ₀ = f (Q) (Figure 2), η ₀ = f (Q) (Figure 3) using polynomials of the third degree:

where i = 0, 1, 2, ... are the moments of time at which the constructions are performed;

Q _i - current flow rate (flow rate in the pump operating interval at time i);

H _i - pressure values depending on the flow rate Q _i ;

N _i - power values depending on the flow rate Q _i ;

η _i - the efficiency of the pump depending on the flow rate Q _i ;

a ₀ , a ₁ , a ₂ , a ₃ , b ₀ , b ₁ , b ₂ , b ₃ , c ₀ , c ₁ , c ₂ , c ₃ - approximation coefficients, the numerical values of which depend on the pump unit and the pipeline network, they are determined experimentally during a complete pump diagnosis.

At a constant speed and an increase (decrease) in viscosity, the H (Q) curve decreases (grows), therefore, in the case of a change in viscosity, it must be taken into account that:

where Q _v - flow rate with an increase (decrease) in viscosity;

Q _CV - flow rate with the viscosity of pure water;

N _CHV - pressure with the viscosity of pure water;

H _v - pressure with an increase (decrease) in viscosity, which is found as:

where k is the coefficient of proportionality, k = f (Re) (Re is the Reynolds number).

Additionally build the dependence of the pressure and flow from the power consumption: H = f (N) and Q = f (N), which combine on the same graph (Figure 4).

Obtaining the initial pressure and energy characteristics is carried out at the first start-up of the pump unit or when it is put into operation after a major overhaul. The initial characteristics are necessary to determine the critical values of the parameters of the pumping unit, upon reaching which the further operation of the scientific equipment becomes economically unfeasible.

Next, the pump is put into operation in accordance with the working task for pumping and measure the current values of density, temperature, viscosity of the pumped liquid, power consumption, pressure at the input and output of ON. On the basis of the measured values create a database of operating parameters. Further, with the help of a database, it is possible to analyze the influence of various factors and operating modes of the operating equipment on the technical condition of the operating equipment in order to minimize the influence of negative factors on the operating state of the operating equipment, and to optimize the operating conditions of the scientific equipment.

One of the features of the operation of pumping units in the RPM system is that some of the sensors for monitoring the parameters of the pumping unit (pressure sensors, mortise flow meters, temperature, density sensors) are continuously exposed to factors unfavorable for the stable operation of these sensors: aggressive corrosive pumped medium and the presence of solid suspended particles in it, pressure surges, volley discharges from treatment facilities that change the density and viscosity of the pumped liquid, the work of various GOVERNMENTAL modes on pipelines with varying network parameters (connection and disconnection of different wells in various combinations pickup varying injectivity of wells). The combination of these factors can lead to malfunctions (clogging) of the sensors and false readings. Moreover, all the monitored parameters of the pump are interconnected and the inaccuracy of one parameter can lead to significant errors in determining the general state of the ON. Thus, from the set of monitored parameters of ND, it is necessary to choose a parameter whose measurement has good accuracy, is least affected by adverse factors, and the parameter itself is interconnected with parameters exposed to such factors. In the case of operation of an ACS system, the PDP as a control parameter, we take the power consumed from the network, since the electricity meters are not affected by adverse factors, have good measurement accuracy, and have a significant working resource. At the same time, the measured power consumed from the network has a relationship with the measured flow rate and the calculated pressure, which are the main parameters in determining the efficiency of an atomic converter. In addition, electric motors of NA have stable characteristics, a large working resource and high efficiency, and the efficiency varies slightly over time, therefore, the contribution of the decrease in the efficiency of the electric motor to the drop in the efficiency of the NA for the period of operation of the NA before overhaul can be neglected.

According to the telemechanics system, the current values of power consumption (N _i ), flow rate (Q _i ), density of the pumped liquid (ρ _i ), viscosity (ν _i ), temperature (T _i ), inlet pressure (P _i.in ) and output ( P _i.output ) the pumps are transferred to the control room control room where the current head value (H _i ) is calculated.

The current head developed by the pump is calculated from the measured pressures at the inlet and outlet of the pump, taking into account the current density:

where H _i is the current head developed by the pump, m;

P _i.out , P _i.in. — readings of liquid pressure measuring instruments at the outlet and inlet of the pump, Pa;

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

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

u _o , u _in - the fluid velocity at the outlet and inlet of the pump, m / s;

(z _out -z _in ) - the difference between the geodesic heights of the outlet and inlet of the pump, m

For pumps of the PPD system u _out ≈u _in , z _out = z _in .

The calculated current head and the measured current flow rate are correlated with the current power consumption for the current temperature, density and viscosity of the liquid (Figure 4). If one or more of these parameters changes, a corresponding analytical adjustment of the interconnected parameters is carried out, and a corresponding adjustment of the operating mode of the AT to carry out the download task is carried out from the control room control room.

It should be noted here that after the start-up of the ON operation, the pressure and flow rate of the pump gradually decrease. The reduction rate depends on many factors (operating modes of the ON, pumped medium, timely maintenance, etc.), which in turn leads to a decrease in the overall efficiency of the ON. A general view of a linear reduction in efficiency is shown in FIG. 5. Decrease in efficiency can occur according to more complex laws.

Further, in the process of operating ON, the calculated value of the current head and the measured value of the current flow rate are correlated with the measured current power consumed from the network (Figure 4) for the current temperature, density and viscosity of the pumped liquid. Here, the current values of the measured parameters (pressure, flow, power, etc.) mean instantaneous values averaged over a certain period of time (for example, 5-10 minutes). Since the observation time interval is small, a decrease in the current head (H _i ) and current efficiency (η _i ) for this period of time within the permissible change in the parameter values can be neglected, i.e. dH _i / dt → 0 and dη _i / dt → 0. If the correlated current flow and pressure values correspond to the current power consumption at the current temperature, viscosity and fluid density within the permissible range of possible parameter changes (for example, 1-2%, determined from the operating conditions of the ON) (pressure pulsation, density, flow non-uniformity, fluctuations temperature, viscosity, power surges, etc.), then, therefore, the parameter measurement sensors are in good condition (Figure 4). In case of mismatch of the correlated values of the head and / or flow rate of the current power consumption at the current temperature, viscosity, density (the values fall outside the permissible range), or in the case of a rapid change in the current head (in this case, the readings of the pressure sensors at the pump inlet and outlet are separately controlled and compared with previous readings of these sensors to localize the reasons for the rapid change in the current pressure) and / or flow rate relative to the values of previous measurements (for example, more than 5% per obs give interval averaging, the threshold value is determined from the operating conditions) at constant temperature, viscosity, density of the fluid and power consumption, or inconsistent changes one of the parameters with respect to changes in other interconnected with it controllable parameters, is carried out by the measuring system.

After checking the correspondence of the flow-pressure head of the current power consumption, the current value of the net power (N _i.п ) and the current value of the pump efficiency (η _i.н ) are _calculated . Also take into account the total operating time (hours) of the pump (t _p ).

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 _i.p is the net power developed by the pump, kW;

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

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

H _i - the current head developed by the pump, obtained by the formula (2), m;

Q _i - the current flow rate of the pump, m ³ / s;

1000 is a conversion factor.

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

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

N _i.p - current net power developed by the pump, kW, obtained by the formula (7);

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

η _e - the efficiency of the electric motor.

All measured and calculated parameters of the AT are entered into the computer memory and form the database of the operating state of the AT. The calculated values of the current pump efficiency (η _i ) for the current flow rate (Q _i ) at the current density, temperature and viscosity of the pumped liquid are compared with the values of the initial analytical dependence of the pump efficiency for the current flow rate (η ₀ = f (Q)) (Figure 6 ) Upon reaching the value of the current calculated efficiency of the specified critical value η _crit = (Q) (Fig.6), the pump is subjected to a complete diagnosis and a decision is made to bring the overhaul to overhaul. In the course of operation of the scientific equipment, at certain time intervals Δt (for example, 200-300 hours, it is determined based on the operating modes of the pump: pump operating ratio, pumped fluid volumes, necessary pressure, pumped fluid quality, allowable range of parameters, etc.) on On the basis of the database located in the computer’s memory, new analytical pressure and energy dependencies are formed for the pressure, flow rate, and efficiency that have changed during operation, and the pressure-flow dependence on consumption is adjusted emoy power, if necessary with the control point PU adjusted operating conditions, and continue analysis of the markets on the basis of new dependencies based on current density, temperature and viscosity of the pumped liquid.

Consider the method of operating the pump unit in the process of pumping fluid into the reservoir using the example of monitoring the state of the central nervous system 63-1400 installed on the central control station 109 of NGDU Jalilneft.

The initial pressure characteristic of this HA (at the initial time i = 0) is shown in FIG. 1, the energy characteristic is shown in FIG. 2, and the efficiency is shown in FIG. 3. The following initial analytical dependencies were also obtained using formulas (1) - (3):

where H ₀ is the initial pressure characteristic;

Q is the flow rate in the working interval of the pump;

N ₀ - initial power consumed from the network;

η ₀ is the initial pump efficiency.

For the current flow rate, the critical value of the pressure H _crit ≈0.9H ₀ (Figure 1), the critical value of the efficiency η _crit ≈0.92η ₀ (Figure 6). The dependence of the head-flow from the current power consumption, as well as the range of permissible changes in operating parameters are presented in Figure 4. Then the pump was put into operation. The table shows the monitoring of operating parameters of the central nervous system 63-1400 during operation.

The temperature, density and viscosity of the pumped liquid varied within the limits of the measurement errors and were not taken into account in the calculations.

Each line shows the pump operating mode for 240 hours. Head, power consumption and efficiency were taken at the end of the time period. As can be seen from the table, in lines 1-2, the pump worked within the allowable ranges of parameter changes. In the second line, the pump flow was increased, and, accordingly, the permissible ranges of parameter changes and critical values for pressure and efficiency were changed. In this case, the average value of the drop in efficiency was 0.01% per day, for 3 lines, new dependences of the flow-pressure on the power consumption were determined and the permissible ranges of parameter values were recounted to take into account the decrease in pressure and efficiency. In the fourth row, 130 hours after the end of the previous observation, the pump head decreased significantly. The current pressure and efficiency values have approached their critical values, which implies a decision to bring the pump into overhaul taking into account the technical and economic calculation. However, at the same time, the values of the consumed power and flow rate of the pump, as well as the density, temperature and viscosity of the pumped liquid remained within the acceptable ranges corresponding to a pressure of 1508 meters. Thus, a change in the pressure value occurred that was inconsistent with other parameters (power consumption, flow rate, density, viscosity, temperature). The clogged outlet pressure sensor was checked and cleaned and the readings returned to the set range.

Thus, the proposed method of operating the pumping unit in the process of pumping fluid into the formation for the pump in question allows us to timely determine inaccurate sensor readings, respond quickly to changing operating conditions of the pumping unit, and reduce the cost of its full diagnosis.

The technical and economic efficiency of the proposed method of operating the pumping unit in the process of pumping fluid into the formation is achieved by expanding the functional capabilities of the operation of the scientific equipment by providing constant monitoring of the accuracy of the readings of pressure, flow, temperature, viscosity density of the pumped liquid during operation of the pumping unit, power consumption and determining the current efficiency, including with constantly changing operating modes of the ON, the possibility of analysis of the influence of various factors on the technical characteristics of the ON and minimizing the impact of adverse factors on the work of the ON.

The use of this proposal allows, at low additional costs, using the existing reservoir pressure maintenance system, to reduce the cost of inefficient injection, increase the efficiency of the pump due to the timely determination of inaccurate values of the sensor readings and, as a result, save material costs of maintaining the reservoir pressure.

Claims (1)

A method of operating a pumping unit in the process of pumping fluid into the formation, including monitoring the parameters of the sensors: flow rate of the pumped liquid, pressure drop at the inlet and outlet of the pump, power consumption of the pumping unit; determination of the efficiency of the pumping unit, based on controlled parameters, regulation of the operating mode of the pumping unit within the permissible working area of the pumping unit; inspection and repair of the pump unit with a decrease in the efficiency below a predetermined critical value, characterized in that the sensors additionally control the parameters: frequency of rotation of the pump shaft, density, viscosity and temperature of the fluid pumped through the pump unit, determine the pressure created by the pump unit based on differential pressure and fluid density, flow rate of the pump unit - taking into account the temperature and viscosity of the liquid, and the efficiency - taking into account the viscosity of the fluid bones, while all parameters averaged over a period of a given time interval are simultaneously monitored in real time, if the values of one of the parameters that are not consistent with other parameters go beyond certain acceptable values during this period, calculated taking into account the pressure drop and the pump unit efficiency during operation, for a given parameter, inspect and / or repair the sensor measuring this parameter, and inspect and repair the pump unit when A significant exit of the values of the measured parameters beyond the critical limits.

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