RU2513889C1 - Flushing method of well submersible electric centrifugal pump - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: invention is related to oil and gas industry and is focused on increase in efficiency of operation of submersible electric centrifugal pumps which is complicated by formation of asphaltene, resin and paraffin deposits on the pump actuating elements. It is suggested to use hot oil as a reagent dissolving deposits in technology of dynamic impact. To this end chambers having similar volume with an electric heating element and temperature sensors are installed preliminary above and below the submersible pump. After shutdown of the electric centrifugal pump the borehole oil is heated up to the required temperature in the lower chamber and transferred through the pump cavity to the upper heating chamber by the same pump. In order to decrease flow rate of hot oil through the pump cavity pumping capacity is decreased by means of current frequency controller. With the three-position reverse-flow valve installed above the upper heating chamber hot oil is returned back to the lower chamber from the well head by means of portable pump unit of TSA-320 type. When there is no three-position reverse-flow valve installed above the upper heating chamber hot oil is returned back to the lower chamber by gravity flow. The period of hot oil cyclic impact on deposits inside the cavity of the submersible electric centrifugal pump shall be equal to time required for complete dissolving of asphaltene, resin and paraffin deposits. This time is determined preliminary in laboratory conditions with well conditions modelling.EFFECT: periodic use of this method at wells complicated with deposits allows increase in their failure-free operation.3 cl, 1 dwg

Description

The present invention relates to technologies for cleaning a deep well pump from deposits and can be used in the oil industry for wells with a deep electric submersible pump.

Downhole oil production with a high content of asphaltenes, resins and paraffins is complicated by the loss of these components from oil and the formation of deposits from them in the cavity of the deep pump and its working bodies. Due to deposits, the throughput of the deep electric centrifugal pump (ESP) is significantly reduced.

It is a well-known method for cleaning a borehole ESP by pumping from the wellhead into lift pipes the calculated volume of the reagent. Previously, a special three-position check valve is installed above the pump during its descent, for example, KOT-93 manufactured by NP Packer (product catalog No. 10 for 2011, pp. 106-107;). To open such a check valve in the opposite direction, it is necessary to create a certain pressure drop above it, which is done by the oil industry workers during the pump flushing.

The disadvantage of this method is that for washing the ESP cavity and filter, as a rule, no more than 100-300 liters of reagent (solvent) are required, and several cubic meters of expensive solvent are forced to pump from the wellhead. In the absence of solvent in the well, the method cannot be implemented.

A device for cleaning the column of elevator pipes from deposits (RF patent for the invention No. 2452850, publ. 10.06.2012), with which the solvent is heated before it enters the deep pump. In the absence of solvent, this device can be used to heat well oil for subsequent flushing of deposits from the cavity of the downhole pump. Asphalt-resin-paraffin and salt deposits are filled and working turbines with guides of electric centrifugal pumps (ESP). As a rule, high-performance ESPs with a flow rate of 30 or more m ³ / h are widely used in oil fields. The solvent or oil heated in the container according to the invention No. 2452850 will be pumped through the cavity of the electric centrifugal pump for several minutes after it is put into operation. Meanwhile, the effective dissolution of many types of deposits requires from 60 minutes or more. There is a need to increase the time of interaction of the reagent with deposits inside the ESP.

There is also a method of removing deposits from the oil pipeline (RF patent for the invention No. 2460594, publ. 09/10/2012), in which the deposits are dynamically affected by the solvent. According to the method, deposits are removed with a smaller amount of reagent. The technology does not provide for continuous supply of heat to the dissolving agent; therefore, when using well and unheated oil as an AFS solvent, this technology will not bring a positive effect.

The technical task of the claimed invention is to create a dynamic mode of influence on deposits in the cavity of a deep electric centrifugal pump of a well with a reagent or well oil of elevated temperature.

The problem is solved in that in the method of washing a borehole deep electric centrifugal pump, which includes feeding the reagent into the pump cavity, and also containing a reagent heating procedure before being fed to the pump, additional heating of the well oil in the chamber between the ESP and the reverse three-position valve is organized similar to the heating procedure in the chamber below the ESP, and flushing the pump with hot oil is carried out in several cyclic “up and down” movements, up with the help of a deep pump, and down with the help of a catheter schyu pump unit with the wellhead and the tubing string to increase the interaction time with hot oil deposits reduce the pump capacity to the control station via frequency current regulator. In the absence of a check valve above the ESP, the dynamic action of the heated reagent is organized by gravity due to the force of gravity in a vertical well. Such a technology requires preliminary pressure relief and equalization of fluid levels in the annulus of the well and the lift pipe string, as well as taking into account the movement of a known volume of heated reagent from the lower chamber to the upper and vice versa by the time of operation of the downhole pump and tracking the liquid level in the lift pipe string. The internal volumes of both chambers are equal in order to heat the same volume of oil.

Consider the drawing of the arrangement of the wells for cleaning deep ESP from deposits by the proposed method, where:

1 - a column of elevator pipes;

2 - three-position check valve - KOT;

3 - the upper heating medium heating chamber with temperature sensors;

4 - electric centrifugal pump;

5 - lower heating medium heating chamber with temperature sensors;

6 - pumping unit at the wellhead to move the coolant down;

7 - wellhead valve annulus;

8 - control station for ESP and reagent heating chambers;

9 - valve string of lift pipes (KLT);

10 - bit valve KLT.

The control station for the operation of the ESP includes a controller for receiving and processing information from temperature sensors of chambers 3 and 5, as well as a frequency regulator of the current strength of the submersible electric motor (PEM) of the installation. Using a frequency controller, the performance of the ESP during the processing time is reduced to the necessary level so that the total processing time corresponds to the optimal value.

We will consider the implementation of the method by the example of an oil well equipped with an ESP, inside of which intensive deposits of asphaltenes, resins and paraffins are constantly formed with a certain time interval. The following procedures are performed:

The first option - above the upper chamber 3 there is a CAT.

1. The electric centrifugal pump 4 from the control station 8 is stopped.

2. At the same time, both well oil heating chambers are put into operation.

3. Borehole oil of known volume V in the lower chamber 5 is heated to the required temperature T, for example, 10-20 ° C higher than the temperature of precipitation of paraffin oil - T _P. Note that T cannot exceed the critical temperature T _cr for safe operation ESP, in particular a submersible electric motor, that is, the condition is satisfied: T _P <T <T _cr .

4. The deep oil pump 4 moves the hot oil from the lower chamber 5 to the upper heating chamber 3. In this case, the actual, that is, reduced ESP performance is taken into account due to the decrease in the frequency of the PED supply current from the control station 8.

5. The oil transferred to the upper chamber is heated to a temperature T and it is moved by the wellhead pump 6 through pump 4 to the lower chamber 5. For this, pump 6 raises the pressure in the lift pipe string 1, valve 2 (KOT) opens, after which the oil from the lift pipe pipes displaces hot oil down.

Depending on the actual performance of the electric centrifugal pump 4 and the pumping unit at the mouth 6, several vertical displacements of volume V hot oil are performed through the deep ESP so that the total time of the dynamic action of hot oil on the deposits is at least the necessary time previously determined according to the results of laboratory simulation of the process dissolution of paraffin.

The second option - above the upper chamber 3 there is no CAT.

1. The electric centrifugal pump 4 from the control station 8 is stopped.

2. The valve 9 is closed, the valve 7 and the discharge valve 10 are opened so that the fluid levels in the lift pipes and in the annulus are stabilized and leveled.

3. At the same time, both borehole oil heating chambers are put into operation.

4. Borehole oil of known volume V in the lower chamber 5 is heated to the required temperature - T, for example, 10-20 ° C higher than the temperature of the precipitation of paraffin oil - T _P. Also the condition T _P <T <T _cr .

5. With the deep pump 4, taking into account its actual performance, hot oil is moved from the lower chamber 5 to the upper heating chamber 3. Due to this, the oil level in the lift pipe string rises to a height corresponding to the volume of hot oil raised - V. It should be noted that during vertical movement of hot oil in the lower and upper chambers is a constant heating of oil to the required temperature T.

6. After stopping the ESP 4 due to a higher liquid level in the column of elevator pipes than in the annulus, hot oil from the upper chamber 3 will begin to flow by gravity through the ESP cavity 4 into the lower chamber 5.

7. The position of the liquid level in the KLT during the washing of the ESP is monitored continuously or periodically by an acoustic level gauge through valve 7 or 10, thereby making a timely decision about the start of the second processing cycle.

A significant difference of the proposed method from previously known inventions and technologies, in our opinion, lies in the following positions:

1. According to the invention No. 2460594, the use of oil in the oil pipeline as a solvent, even in dynamic mode, will not lead to a positive result, because ordinary oil is not an AFS solvent, and this technology does not provide for oil heating. We have proposed in dynamic action with a reagent to use oil, which already has the property of a solvent due to its high temperature.

2. According to the invention No. 2452850, a solvent delivered to the container from the wellhead is used as a heat carrier. And the use of borehole oil for heating under the ESP will not lead to the desired effect due to the rapid cooling of oil after passing through the cavity of an electric centrifugal pump. Only in a controlled movement of practically equal and high temperature hot oil portions back and forth through deposits in a deep pump can a new and positive technical result be expected - an effective dissolution of paraffin in the cavity of an electric centrifugal pump without the use of a special reagent, namely, an organic paraffin solvent.

Thanks to the proposed technology, deposits from the internal organs of the ESP will be removed promptly and effectively without the use of a solvent.

Claims (3)

1. A method of washing a borehole deep electric centrifugal pump (ESP), which includes feeding the reagent into the pump cavity, and also containing a procedure for heating the reagent before feeding it to the pump, characterized in that additional heating of the borehole oil in the chamber between the ESP and KOT is organized similar to heating in the chamber below ESP, and flushing the pump with hot oil is carried out in several cyclic up-and-down movements, namely: up with the help of a deep pump, and down through the CT with the help of a pumping unit from the wellhead and the string iftovyh tubes, and for increasing the reaction time of hot oil with reduced deposition performance of the ESP with the installation control station via frequency current regulator. 2. The method according to claim 1, characterized in that in the absence of a check valve above the ESP, the reverse movement of hot oil from the upper chamber to the lower is organized by gravity due to the force of gravity in a vertical well by preliminary discharge of pressure and equalization of fluid levels in the annulus of the well and the lift string pipes, and the known volume of the heated reagent is moved from the lower chamber to the upper one and vice versa according to the time of operation of the deep pump and tracking the liquid level in the column of elevator pipes or in the annulus. 3. The method according to claim 1, characterized in that the borehole oil heating chambers located below and above the electric centrifugal pump have equal internal volumes.

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