RU2519238C1 - Method of well operation with help of electrically driven borehole pump plant - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed method comprises reiteration of fluid evacuation from the well alternating with fluid accumulation of fluid therein at off borehole pump and adjustment of relationship between evacuation and accumulation duration depending upon well fluid dynamic level. In compliance with this invention, duration of all cycles is set equal to 40-80 minutes. Rated efficiency of borehole pump is set 3 to 5 times higher than the well producing ability. Duration of fluid evacuation at different cycles is periodically adjusted by changing of previous magnitude by 10-20% unless preset fluid level is reached.

EFFECT: high-efficiency, reliable operation.

3 cl

Description

The invention relates to the extraction of fluid from wells by a mechanized method using a submersible electric centrifugal pumping unit (ESP) and can be used in the operation of producing oil wells, mainly low-flow and medium-flow.

The closest in technical essence and the achieved effect to the claimed is a method of developing a well and / or bringing it to the optimal mode after repair (RF patent 2315860, IPC ЕВВ 43/25, publ. January 27, 2008), including the use of ESP, in which pumping fluid from the well alternate with the accumulation of fluid in the well when the ESP is off. The duration of fluid pumping from the well and the duration of fluid accumulation in the well are controlled by changing their ratio so that the ESP operates in a periodic short-term mode (PCW). In this mode, the well is equipped with large-sized ESPs with the best technical and operational characteristics in the short-term mode. The operation of low-debit wells in the oil and gas wells avoids the complications arising from the use of small standard sizes of ESPs in a constant mode, namely, increased wear of working bodies and low ESPs efficiency during operation in the left pressure-flow characteristic zone; clogging of the working parts of the ESP with mechanical impurities due to the small size of the passage channels; intensive deposition of salts on the working bodies of the ESP due to insufficient cooling with a low influx of formation fluid.

The disadvantage of this method is the need to control the speed of rotation of the ESP shaft, which leads to jamming and rapid wear of the equipment. In addition, according to the known method, the operating time of the ESP, the accumulation time of the liquid and, accordingly, the duration of each period of work depend on the time to reach the thermal equilibrium of the ESP elements with the environment. This leads to equipment downtime and reduced productivity. The duration of the equipment in the known method is less than the duration of the pause.

The objective of the invention is to ensure productive and reliable uptime of the equipment.

The solution to this problem is achieved by the fact that in the method of operating the well using the ESP, including repeating the cycles of pumping fluid from the well, alternating with the accumulation of fluid in the well when the ESP is turned off, adjusting the ratio of the duration of pumping and accumulation depending on the dynamic level of the fluid in the well, the duration of all cycles are set equal, and the duration of each cycle is set in the range from 40 minutes to 80 minutes, while the duration of pumping fluid in different cycles ah periodically controlled by modifying the previous value by 10-20% until it reaches a predetermined liquid level. The operating time of the ESP in the cycle is determined by the formula:

$$T_R=\frac{P}{E}\times \mathrm{Ts}\times {\mathrm{TO}}_{\mathrm{about}b}$$

where: T _p - the operation time of the ESP in the cycle, min;

P - well productivity (indicator of the potential of the well for the estimated bottomhole pressure in surface conditions), m ³ / day;

E - passport nominal productivity of ESP, m ³ / day;

C is the cycle time, min;

To _about - the correlation coefficient of nominal performance.

Coefficient K _about establishes a connection with the flow rate of the well in surface conditions, is a function depending on thermobaric conditions, volumetric coefficient of fluid, saturation pressure, gas factor, and other PVT properties and can take a value from 1.0 to 2.0. The coefficient K _{about is} calculated for each object of development.

It is advisable to operate the well with ESPs with a productivity of 45 m ³ / day to 80 m ³ / day.

The essence of the method is to select the duration of the operation of the ESP, during which the operating point of the ESP is in the zone of maximum efficiency, and the duration of the inactivity of the well, sufficient for the accumulation of fluid in the well for the next pumping.

In the PCV mode, the well is equipped with large-size ESPs (45≤Q≤125 m ³ / day), which have the best technical and operational characteristics in the short-term mode, in which the volume of pumped fluid corresponds to the nominal flow rate. The equipment size and the pumping and accumulation mode are selected taking into account the influence of oil degassing on the stability of the ESP and the maximum depression on the formation. Calculation of the depth of descent, the size of tubing, pressure and power of the ESP are carried out in programs for calculating a constant mode of operation, while the inflow value is set 3-5 times more than the actual productivity of the well.

In accordance with the claimed method, the duration of each cycle is set equal to from 40 minutes to 80 minutes, while the duration of pumping fluid in the cycle, if necessary, is periodically changed by 10-20% from the previous value until the desired fluid level in the well is reached. This mode of operation of the ESP ensures maximum depression on the formation during its operation and allows the efficient use of equipment. In addition, the operation of the well in the claimed mode allows you to automate the process. It is advisable to operate the well with an ESP with a productivity of 45 m ³ / day to 80 m ³ / day, which ensures maximum energy efficiency. The nominal productivity of the ESP is chosen 3-5 times more than the actual productivity of the well. When using more productive ESPs and, as a result, more powerful electric motors, there are risks of breakdown of the ESPs shaft.

The method is implemented as follows.

Before starting the ESP in the PCV mode, the well productivity is calculated taking into account the rate of recovery of the inflow.

The operating time of the ESP in the cycle is determined by the formula:

$$T_R=\frac{P}{E}\times \mathrm{Ts}\times {\mathrm{TO}}_{\mathrm{about}b}$$

where: T _p - the operation time of the ESP in the cycle, min;

P - well productivity, m ³ / day;

E - passport productivity of ESP, m ³ / day;

C is the cycle time, min;

To _about - the correlation coefficient of productivity.

Then, the control station is programmed in the PCV mode, the protection response parameters are set, the ESP is launched and the mode is output. The claimed operating mode includes repeating cycles of pumping fluid from the well, alternating with the accumulation of fluid in the well when the ESP is turned off. The duration of all cycles is set equal to one hour. The ratio of the duration of fluid pumping and the duration of fluid accumulation in the cycle is periodically adjusted according to the control results by changing the previous value by 10-20%.

Monitoring of ESP parameters (readings of the controller of the control station, measuring dynamic, wellhead, and buffer pressures) and analyzing the operation of the ESP for compliance with the target indicators are carried out periodically, for example, every 12 hours. Parameters are monitored at a given frequency until the value of the minimum pressure at the ESP unit during the day corresponds to the calculated (target) indicators. Further control is carried out similarly to the control of the ESP under constant mode. Based on the measurement results, conclusions are drawn about changes in the dynamic level. An increase in the dynamic level during the operation of the ESP in the PCV mode indicates insufficient pumping of fluid from the well. With an increase in the dynamic level, the ESP operation time in the cycle is periodically increased step by step (in increments of 10-20% of the operation time). In this case, the accumulation time in the cycle is correspondingly reduced. Periodic changes are made until the required level is established. Similarly, a decrease in the dynamic level during the operation of the ESP in the PCV mode indicates an excess of pumping fluid from the well. In this case, the ESP operation time in the cycle is reduced step by step (in increments of 10-20% of the operation time). In this case, the accumulation time in the cycle increases accordingly.

Subject to the relationship between the ratio of the nominal productivity of the ESP and the productivity of the well (3-5 times to achieve energy efficiency), the cycle time (T _p ) varies from 40 to 80 minutes and usually is 60 minutes. The cycle time is selected taking into account the requirements of ensuring maximum production and reliable uptime of the equipment. Regulation of the PCV mode is carried out only by a phased change in the operating time of the ESP, which greatly simplifies the task of the technologist when choosing the optimal selection of the PCV mode and regulation during operation. The accumulation time is determined by the remaining cycle time of 60 minutes with the exception of the operating time.

The claimed method of operating a well using an ESP provides a maximum approximation of the average value between the upper and lower pressure limits when starting and stopping at the target (calculated) pressure at the reception. This indicator directly affects oil production. It was experimentally found that with an increase in the cycle time of more than 80 minutes, a significant decrease in oil production occurs in comparison with the constant mode of operation.

In addition, the operation of the ESP in the claimed mode eliminates the likelihood of freezing of non-return valves in the winter at the wellhead fittings. It was experimentally established that during the accumulation period with the ESP turned off, up to 60 minutes (the cycle is not more than 80 minutes), the risks of freezing the check valves are minimal.

The choice of the lower limit of the cycle duration of 40 min ensures the reduction of the risks of premature failures. The number of starts of the ESP has an exponential dependence on the cycle time. Thus, an increase in the frequency of starts, including smooth ones, according to the theory of reliability by exponential dependence increases the risks of premature failures.

Claims (3)

1. A method of operating a well using a submersible electric centrifugal pump installation, including repeating cycles of pumping fluid from the well, alternating with the accumulation of fluid in the well when the submersible electric centrifugal pump installation is turned off, adjusting the ratio of the duration of pumping and accumulation depending on the dynamic level of the fluid in the well, that the duration of all cycles is set equal in the range from 40 minutes to 80 minutes, the nominal performance is submersible lektrotsentrobezhnoy pump device is selected in 3-5 times more actual productivity of the well and the duration of pumping liquid in different cycles periodically controlled by modifying the previous value by 10-20% until it reaches a predetermined liquid level. 2. The method according to claim 1, characterized in that the operating time of a submersible electric centrifugal pump installation in a cycle is determined by the formula:
$$T_R=\frac{P}{E}\times \mathrm{Ts}\times {\mathrm{TO}}_{\mathrm{about}b}$$

where T _p - the operating time of the submersible electric centrifugal pump unit in the cycle, min;
P - well productivity, m ³ / day;
E - passport performance of a submersible electric centrifugal pump installation, m ³ / day;
C is the cycle time, min;
To _about - the correlation coefficient of productivity. 3. The method according to claim 1, characterized in that the well is operated by a submersible electric centrifugal pump unit with a capacity of 45 m ³ / day to 80 m ³ / day.