RU2481470C1 - Downhole separator for separating water and gas and oil mixture - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: downhole separator for separating water and gas and oil mixture includes stepped tubing string with electric submersible pump. It includes separating chamber, through channel for oil and inlet holes for water. As separating chamber it contains tubing string of larger diameter. Inside the tubing string of larger diameter there is a short tubing string of smaller diameter. The tubing strings of smaller diameter are located near the mouth at the area of well bore with inclination angle more than 3 degrees. Note that the tubing string of smaller diameter is equipped with a shank plugged from the bottom end with two rows of inlet holes along the whole length for water supply. The shank is connected to it by high pressure sleeve. The shank from the holes side is located at the bottom forming internal surface and at the distance from the bottom end of the tubing string of larger diameter.

EFFECT: separation and extraction of small volumes of oil from large volumes of water due to process performance in inclined area of the well.

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Description

The present invention relates to the oil industry and may find application in a system for maintaining reservoir pressure during cross-hole pumping of water to separate dispersed-droplet oil from produced products of a water well with a slight slope, which has passed from the category of the former oil producing due to flooding of the reservoir.

A well-known installation for separating well fluid, including a separation chamber, in which a static separator is located for separating water from oil, including an outlet for receiving well fluid from an outlet section of a well below a separation chamber, an outlet for an oil-enriched component opening into a section of a well above the separation a chamber and an outlet for a water-enriched component opening in a well outlet section below the separation chamber, and high and the thickness of the separation chamber interlayer dispersion which is formed therein under normal operating conditions (RF Patent №2268999, publ. 20.07.2004).

The known device is designed to separate a high oil content in the produced fluid and has a complex structure.

Closest to the proposed invention in technical essence is a downhole separator comprising a separation chamber, an oil outlet above the separation chamber, and a water outlet under the separation chamber. As the separation chamber, the lower part of the well is used, bounded by a casing string and a separation cuff, which is mounted on a liner attached to a submersible electric motor of an electric centrifugal pump suspended in the well on a tubing string. The shank in the lower part under the separation cuff is equipped with a stopper, and in the upper part above the separation cuff, there is a water outlet. As an outlet for oil, a discharge tube with windows and pipes was used to communicate the space under the separation sleeve and the space above the reception of the electric centrifugal pump (RF Patent No. 2291291, publ. 10.01.2007 - prototype).

The known device is intended for the separation of a high oil content in the produced fluid.

The proposed invention solves the problem of separation and selection of small volumes of oil from large volumes of water due to the process in an inclined section of the well.

The problem is solved in that the downhole separator for separating the water-gas mixture, including a stepped column of tubing with an electric submersible pump, a separation chamber, an oil passage and water inlets, according to the invention, comprises a tubing string of larger diameter as a separation chamber with a short column of tubing of smaller diameter located in it, which are located close to the mouth in the section of the borehole with an antiaircraft angle m more than 3 degrees, while the tubing string of smaller diameter is equipped with a liner plugged from the lower end with two rows of inlet openings along the entire length for water intake connected to it by a high pressure sleeve, and the liner from the side of the holes is located on the lower generatrix of the inner surface and at a distance from the lower end of the tubing string of larger diameter.

Figure 1 presents the claimed downhole separator; figure 2 is a cross section aa in figure 1.

The downhole separator comprises a stepwise suspension of the tubing string 1 with an electric submersible pump connected to the lower part (not shown in FIG.), Lowered into the production string of the deviated well 2. The upper part of the suspension consists of a large diameter tubing string (tubing) 3 and placed in it a short string of tubing of smaller diameter 4, which is located near the wellhead with an zenith angle of more than 3 °.

The tubing string of a smaller diameter 4 is equipped with a liner 5 blanked from the lower end with two rows of inlet openings 6 along the entire length for the flow of produced water, connected to it by a high pressure hose (reinforced rubber hose) 7. The shank 5 from the side of the openings 6 is located on the lower generatrix of the inner surface 8 and at a certain distance from the lower end of the tubing string of larger diameter 3, in which the gravitational separation of oil and water occurs. The separated oil moves along the upper forming surface 9 of the tubing string of a larger diameter 3.

The downhole separator operates as follows.

In order for the holes 6 of the liner 5 to be located on the lower generatrix of the inner surface 8 of the tubing string of a larger diameter 3, azimuthally oriented descent is observed when assembling the equipment by marking each pipe of the tubing string of a smaller diameter 3 and liner 5 in accordance with the azimuth of the borehole curvature. The connection of the shank 5 with the tubing string of a smaller diameter 4 using a high pressure sleeve allows the shank to always be laid on the lower forming surface of the tubing string of a larger diameter 3.

The length of the shank 5 is selected based on the performance of the pump so that the number and diameter of the holes 6 would ensure the distribution of the partial flow rate of the water flow in each horizontal plane of the location of the holes 6 without trapping dispersed oil droplets.

During operation of the electric centrifugal pump (not shown in FIG.), An upward flow of water with oil drops moves along the tubing string 1. The flow entering the tubing string of a larger diameter 3 located in the borehole curvature reduces the speed. When the dispersed structure of the oil-water mixture moves to the liner 5 due to gravity, the oil droplets float upstream and when these droplets merge, a thin stream of oil forms along the upper forming surface of the tubing string of larger diameter 3. In this case, the water flow moves along the lower forming surface of the tubing string of large diameter 3 and, passing along the shank 5 on each horizontal plane of the hole 6, is partially distributed evenly. Moreover, the speed of the upward flow along the shank 5 after passing through each plane of the holes 6 is reduced due to the partial selection of water, and inside the shank 5 is increased due to the newly incoming portion of water. Due to the location of the holes 6 of the shank 5 on the lower forming surface of the tubing of large diameter 3, the partial selection of a small amount of water from the flow in each transverse plane does not violate the integrity of the jet and the change in the direction of movement of the oil droplets. Water through the high pressure hose 7 rises along the tubing string of a smaller diameter 4 to the wellhead, and oil - through the tubing string of a larger diameter 3.

During operation, the produced water from the donor well (water intake) is pumped into the injection wells through the flow and water lines. At the same time, a limited amount of oil is produced through a larger diameter tubing string by regulating the selection of fluid by a fitting at the wellhead and sent to the pipeline. According to preliminary studies of the oil content in the produced fluid of the donor well, the necessary daily oil production is determined by the pipeline selection line. At the same time, it is optimal to increase the amount of daily fluid withdrawal by the pipeline by 30-50% than is required by the results of determining the oil content in the produced water. This makes it possible to exclude oil from entering the water supply system and to extract oil with an acceptable water content from the products of the donor well.

The simple design of the downhole equipment of the proposed separator allows it to be used to separate the dispersed structure of drip oil and gas from produced water in the donor well bore with an zenith angle of more than 3 degrees, which is a sufficient amount from the stock of this category of wells in the fields of Tatarstan.

The implementation of downhole separation of oil and water with the selection of oil and, in particular, gas from produced water from donor wells using the proposed downhole separator allows preserving the injectivity of injection wells by purifying injected water from oil products and extracting additional oil from water wells.

Claims (1)

An downhole separator for separating a water-gas mixture, including a stepped column of tubing with an electric submersible pump, a separation chamber, an oil feed passage and water inlets, characterized in that it comprises a tubing string of a larger diameter with a her short string of tubing of smaller diameter, which are located near the mouth in the section of the wellbore with an zenith angle of more than 3 °, while on tubing of smaller diameter is equipped with a liner plugged from the lower end with two rows of inlet openings along the entire length for water intake, connected to it by a high pressure sleeve, and the liner from the openings is located on the lower generatrix of the inner surface and at a distance from the lower end of the column tubing of larger diameter.

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