RU2809415C1 - Method for combating asphalt, resin, and paraffin deposits in oil field equipment during well operation - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention can be used to prevent formation and removal of asphalt, resin and paraffin deposits (ARPD) during oil production. A submersible pump is lowered into the well to the calculated depth on the main lift pipes, in which, at the depth of the beginning of crystallization of ARPD, an additional lift string is coaxially installed, fixed at the wellhead fittings, and fluids are pumped to the surface through the annular space of the lift pipes. During the pumping process, pressure at the pump intake and flow rate of the well are monitored, and when the pressure at the pump intake increases with a simultaneous decrease in flow rate, they switch to the mode of periodic pumping of products with an increase in the rotation speed of the pump shaft. After stabilizing the pressure at the pump intake and increasing the well's flow rate, the well is transferred to constant pumping mode.

EFFECT: improved reliability of determining the increase in ARPD deposits in tubing above the permissible value, formation of deposits in downhole equipment is prevented, and the pumping mode of well production is optimized.

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Description

The invention relates to the oil industry and can be used to prevent the formation and removal of asphalt, resin and paraffin deposits (ARPD) during oil production.

There is a known method for preventing the deposition of asphalt-resinous and paraffin oil components in tubing pipes in a well, which consists in the fact that the gas-liquid flow of well production moving in the cavity of the tubing pipes, starting from the depth of the beginning of paraffin crystallization to the wellhead, is accelerated to the quadratic flow by switching to transportation through small-diameter pump-compressor pipes, forming a turbulent mode of movement in their cavity, which, due to the turbulence of the flow, continuously renews the wall oil film, washing out paraffin crystals from the inner surface of the pipe, while at the open end of the pump-compressor pipes of small diameter, a remover of asphalt-resinous and paraffin deposits (RU2661951, 07/23/2018) is dosed through the annular space.

The disadvantage of this method is the small area of the inner wall and the bore diameter of the tubing string and, accordingly, a slight increase in the speed of gas-liquid flow in the tubing string, which does not exclude the deposition of asphalt-resinous and paraffin deposits (ARS) on the walls and leads to rapid overlap of the inner diameter of the tubing.

Of the known technical solutions, the closest to the proposed one in terms of technical essence and achieved result is a method of combating asphalt, resin and paraffin deposits in oilfield equipment, including operating a well using a submersible pump (UESP), increasing the rate of removal of paraffin crystals released from the gas-liquid mixture, followed by coagulation and washing the walls of the lift pipes for removal to the surface, and the ascending gas-liquid flow of the well product, starting from the depth of the beginning of paraffin crystallization to the wellhead, is accelerated by placing an additional lift pipe inside the main lift pipe, forming a turbulent movement mode in the cavity of the lift pipes, which due to turbulence flow continuously renews the wall oil film, washing out paraffin crystals from the surface of the pipes as much as possible, a remover of asphalt-resinous and paraffin deposits is dosed into the elevator columns, while the ascending gas-liquid flow is directed through the interpipe space of the main and additional columns of the elevator pipes, after the accumulation of asphalt-resinous and paraffin deposits on the pipe walls exceeding the permissible limit for deposit thickness, the pump is stopped and an asphalt-resinous and paraffin deposit remover is pumped into the additional pipe with circulation through the interpipe space of the main and additional lift pipe columns to the surface to dissolve the deposited sediment (RU 2779242, 09/05/2022 ).

The disadvantages of this known method include the following: high consumption of remover of asphalt-resinous and paraffin deposits, a significant reduction in the overhaul period of the ESP due to frequent switching on and off of the pump, a sharp increase in friction between the impellers and, as a consequence, an increase in the temperature of the pump, which entails overheating and wedge of the rotating components, an increase in resistance and an increase in engine temperature, which is fraught with failure of the hydraulic protection, as well as increased energy consumption.

Also, the known method does not take into account the peculiarities of deposit formation in downhole equipment during oil production, especially in conditions of high well productivity.

In addition, using as an informative parameter for recording the increase in paraffin deposits and the narrowing of the flow area in the annular space of a concentric string of elevator pipes, the value of the thickness of paraffin deposits, determined empirically, for example, by taking samples, analyzing the energy expended on lifting a unit of liquid from the well and/or etc., reduces the reliability of recording the occurrence of the above event.

The consequence of the above may be an unreasonable stop of the pump and injection of the remover.

The technical problem to be solved by the present invention is to reduce the cost of implementing a method for cleaning the UEPN tubing lift from paraffin, increasing the reliability of determining the increase in paraffin deposits in the tubing above the permissible value, and optimizing the well production pumping regime.

This problem is solved by the described method, which consists in the fact that a submersible pump is lowered into the well to the calculated depth on the main lift pipes, in which, at the depth of the beginning of crystallization of asphalt-resinous and paraffin deposits, an additional lift string is coaxially installed, fixed on the wellhead fittings, and pumping gas-liquid products to the surface through the intertubular space of lift pipes, while during the pumping process the pressure at the pump intake and the flow rate of the well are controlled and when the pressure at the pump intake increases with a simultaneous decrease in flow rate, they switch to the mode of periodic pumping of products with an increase in the rotation speed of the pump shaft, and after stabilizing the pressure at the pump intake and increasing the well's flow rate, the well is transferred to constant pumping mode.

The achieved technical result is to ensure a shift in the crystallization point of asphalt, resin and paraffin deposits from the downhole equipment to the onshore pipeline by increasing the speed and temperature of the flow of gas-liquid products.

The proposed method of combating asphalt, resin and paraffin deposits during oil production is carried out as follows.

A submersible pump is lowered into the well to the calculated depth on the main lift pipes, in which, at the depth of the beginning of crystallization of asphalt-resinous and paraffin deposits, an additional lift string is coaxially installed, fixed to the wellhead fittings.

Gas-liquid products are pumped to the surface along the main lift column and further along the interpipe space of the lift pipes, ensuring the formation of a turbulent movement mode in the cavity of the lift pipes and acceleration of the upward flow.

During the pumping process, the pressure at the pump intake and the flow rate of the well are simultaneously monitored, since the pressure at the pump intake can change for geological reasons, and the liquid flow rate may remain the same or change extremely slightly.

If a gradual increase in pressure at the pump intake is detected with a simultaneous decrease in flow rate and a slight increase in loads on the electric motor, the well is switched to periodic pumping mode with a significant increase in the rotation speed of the pump shaft.

When the described regime is implemented in the flow of gas-liquid products rising from the installation of a submersible electric centrifugal pump (ESP) along the main lift string and further along the annulus, the Reynolds number (Re) increases.

More intense turbulization and an increase in flow velocity, as well as a significantly increased temperature of the produced fluid, lead to a more efficient washout of the near-wall oil film along with paraffin crystals and sharply reduce their accumulation due to the displacement of the crystallization point of asphalt, resin, and paraffin deposits from the well equipment to the surface pipeline.

In emergency situations, in the event of a sharp reduction in flow rate and a significant increase in pressure at the pump intake, the UEPN elevator is treated with an paraffin remover by pumping the remover into a small intermediate column.

Below is an example of a specific implementation of the proposed method.

In one of the wells of the Romashkinskoye field, complicated by ARPO, the UETSN5A-45-1300 pump with a concentric suspension (outer tubing 89 mm and internal tubing 60 mm with bored couplings) operates in constant mode at a frequency of 50 Hz, with a dynamic level of 1000 m (Рр= 2MPa) and flow rate 30 m3/day.

Over the course of a week, there is a smooth increase in the dynamic level up to 900 m (Ppr=30MPa). The flow rate gradually decreases to 24-26 m3/day. The presence of these two factors simultaneously indicates the formation of paraffin in the annulus of a concentric column. The pump is transferred for a day to periodic operation according to the program: 15 minutes of operation at a frequency of 59 Hz with a 5-minute stop for inflow and cooling of the motor.

After stabilizing the pressure at the pump intake to 2 MPa and normalizing the flow rate to 30 m3/day, the well is transferred to constant pumping mode.

The proposed method of combating paraffin is a preventive method to prevent the crystallization of paraffin on the walls of the tubing, allows you to minimize the inter-cleaning period of well operation until the accumulation of asphalt-resinous and paraffin deposits on the pipe walls exceeds the permissible value for deposit thickness compared to the closest analogue due to periodic increasing the pump flow and, accordingly, increasing the speed and temperature of the flow when lifting the extracted product to the surface and increasing the rate of washing out crystals of asphalt-resinous and paraffin deposits from the surface of the pipes.

Claims (1)

A method of combating asphalt, resin and paraffin deposits in oil field equipment during the operation of a well, which consists in lowering a submersible pump into the well to the calculated depth on the main lift pipes, in which an additional lift column is coaxially installed at the depth of the beginning of crystallization of asphalt, resin and paraffin deposits, fixed on the wellhead fittings, and pump gas-liquid products to the surface through the intertubular space of the lift pipes, while during the pumping process they control the pressure at the pump intake and the flow rate of the well, and when the pressure at the pump intake increases with a simultaneous decrease in flow rate, they switch to the mode of periodic pumping of products with an increase rotation speed of the pump shaft, and after stabilizing the pressure at the pump intake and increasing the well flow rate, transfer the well to the constant pumping mode.