RU2422620C1 - Procedure for protection of centrifugal pump from deposit of salts - Google Patents

Abstract

FIELD: oil and gas production. ^ SUBSTANCE: procedure consists in pumping water-free oil through pump unit due to its connection to pipeline of commodity oil through specially made bypass for time required for generation of bitumen-resin-paraffin film of as thick, as 50 mcm on working surfaces. Further, the pump is disconnected from the pipeline of commodity oil and oil is replaced from a cavity of the pump with water. Duration of hydrophobisation is determined beforehand under laboratory conditions by the method of "a cold rod". ^ EFFECT: raised efficiency and reduced expenditures. ^ 1 dwg

Description

The invention relates to the oil industry, namely the operation of electric centrifugal pumps for lifting liquids from wells.

One of the problems encountered in the production of flooded oil using electric centrifugal pumps (ESPs) is the inorganic salt deposition on the working bodies of pumping equipment.

Salt deposits, in particular, are the cause of the increase in the accident rate, primarily “flights”. Available operational data suggest that they are mainly associated with vibration. One of the main causes of vibration is an imbalance due to uneven deposition of salts on the impellers. The general point of view is that the “flight” occurs as a result of increased vibration and pressure pulsation of a worn pump, which lead to the destruction of fasteners and other weak points in the pump installation. The operating experience established the relationship between the distribution of vibration levels and the MTBF of submersible units. ESP vibration can be drastically reduced if scaling is eliminated on its working bodies.

It is known "Device for dosed supply and mixing of a reagent in a well" (RF patent No. 2260110 - 2005. - No. 25), which provides for the placement of a container with a reagent and a deep dosing device in the well below the pump. The device can be used to supply scale inhibitors. The disadvantage of this design is its applicability only in low-yield wells equipped with sucker rod pumps.

A known chemical method for preventing complications caused by salt deposition, providing for the deposition of scale inhibitors from the wellhead through a capillary pipe passing along the outer surface of the tubing (RF patent No. 2260677. A method for chemical protection of downhole equipment from corrosion, paraffin deposits, scale deposits and sulfate-reducing bacteria) .

The disadvantage of this method is the need for complex and expensive equipment and reagents, the complexity of the work on underground repair of wells.

Closest to the proposed invention is the "Method of corrosion protection of sewage pipelines of oil production" (AS No. 266982 of January 13, 1970), which consists in the fact that a layer of oil is applied to the inner surface of the pipeline and oxidized by blowing it with air. For this, according to the invention, the pipeline is filled with oil and held for 5-10 hours, while a layer of asphalt-resin-paraffin deposits (AFS) is formed on the metal surface. Then the pipeline is purged with air for 4-12 hours. Naturally, the inner surface of the pipeline becomes water-repellent (hydrophobic), therefore, corrosive agents and salts contained in water cannot be deposited on such a surface.

The mentioned method is well applicable for hydrophobization of pipelines in which the ratio of the area of the inner surface of the pipeline to its volume is relatively small. However, this method cannot be used for processing ESPs, since the ratio of the area of the inner surface of the pump and its working bodies (impellers and guide vanes) to its volume is large. Therefore, an attempt to hydrophobize by filling the pump cavity with oil and then holding it cannot give a positive result, since in a small volume of oil there are not enough heavy hydrocarbons to precipitate on a large area of the inner surface of the pump and its working bodies.

The purpose of the invention is to simplify and reduce the cost of protecting ESP from salt deposition during oil production from waterlogged wells.

The goal is achieved by preliminary hydrophobization with oil of its working bodies. In this case, hydrophobization is carried out by pumping anhydrous oil through the pump, for which the ESP is connected via a specially mounted bypass to the marketable oil pipeline for the period of formation of at least 50 μm thick asphalt-resin-paraffin deposits on the working surfaces. Upon completion of the treatment, oil is displaced from the ESP cavity by water.

The processing time is determined in advance in the laboratory, for example, by the method of "cold rod".

The implementation scheme of the proposed method is shown in the drawing.

The commodity oil pipeline is equipped with a bypass with shut-off valves 1 and 4 and three-way valves 2 and 3. ESPs (new or after repair) are connected via the bypass to the commodity oil pipeline. The hydraulic resistance of the ESP is much higher than that of the pipeline, so the main oil flow passes through the pipeline, and a smaller part flows through the pump. At the same time, fresh portions of heavy hydrocarbons (AFS), which form a hydrophobic film on the working surfaces of the pump, enter its cavity with oil. In practice, the ESP can be installed for hydrophobization in the daytime and the next day removed and delivered to the well.

The process is carried out in the following sequence: disconnect the ESP from the pipeline by closing the shutoff valves 1 and 4, release the pump cavity from the oil, for which they open the valve 2 and release the pressure in the drainage tank, then open the valve 3 to communicate with the water source (water supply) and displace the oil into the drainage tank until water appears at the outlet of the faucet 2. After that, close the faucet 3, drain the water and disconnect the ESP from the bypass.

Thus, the proposed method is characterized by a sequence of new technological operations:

- instead of protecting the ESP from salt deposition by dosing the reagents into the well, oil hydrophobization of its working bodies is applied by pumping anhydrous oil through the pump, for which the ESP is connected through a specially mounted bypass to the commercial oil pipeline;

- after a hydrophobic asphalt-resin-paraffin film is formed on the working surfaces, the pump is disconnected from the commercial oil pipeline, oil is displaced from the ESP cavity by water and delivered to the field for launching into the well;

- the duration of hydrophobization is determined in advance in the laboratory, for example, by the method of "cold rod".

The method is characterized by the following advantages: during hydrophobization of the pump working bodies by pumping oil, there is no need for complex and expensive dosing equipment and reagents, underground well repair work is simplified, and high profitability is achieved.

Organization of pumping through an oil pump by connecting an ESP through a specially mounted bypass to a commercial oil pipeline simplifies processing, as additional pumping equipment, instrumentation are not required and the process is carried out automatically without the presence of maintenance personnel.

The displacement of oil from the ESP cavity instead of purging it with water after disconnecting from the pipeline increases the safety of production, reduces the likelihood of harmful emissions into the atmosphere.

Early determination of the duration of hydrophobization in the laboratory allows optimizing the processing time of the ESP.

Thus, the proposed method for protecting ESP from salt deposition has the following advantages:

- complete sealing of the process;

- the minimum amount of equipment used;

- high technical and environmental safety;

- ease of implementation of the process;

- economic efficiency.

Claims (1)

A method of protecting an electric centrifugal pump from salt deposition by preliminary hydrophobization of oil by its working bodies, characterized in that hydrophobization is carried out by pumping anhydrous oil through the pump by connecting the electric centrifugal pump through a specially mounted bypass to the commercial oil pipeline for the time necessary to form asphalt on the working surfaces resin-paraffin film with a thickness of at least 50 microns, disconnect the pump from the pipeline for salable oil, displace oil from the pump cavity with water moreover, the duration of hydrophobization is determined in advance in the laboratory by the "cold rod" method.