RU2481471C1 - Method for downhole separation of water and gas and oil mixture - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for downhole separation of water and gas and oil mixture includes separation of mixture and separate extraction of mixture components at inclined area of the well with water extraction. Water extraction is done near tubing string wall opposite to the wall, along which the separated flow of oil and gas goes up. In the course of water and gas and oil mixture separation at the inclined area of the well there performed is the deceleration of mixture flow speed by flow passing into the tubing string of larger diameter. Water extraction is done through the shank located near the said opposite wall. The shank is equipped with the holes located along the shank and directed towards the said opposite wall.

EFFECT: maintaining injection capacity of injection wells by cleaning of pumped water from oil products and extraction of extra volume of oil from water supply wells.

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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-drop oil from produced products of a water well with a slight slope, which has moved from the category of the former oil producing due to flooding of the reservoir.

There is a method of oil production from an underground reservoir through a well, which includes the separation of the well fluid, separate selection of oil and water and regulation of the rate of oil and water extraction (RF Patent No. 2268999, publ. 20.07.2004).

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

Closest to the proposed invention in technical essence is a method of downhole separation of a water-gas-oil mixture, including separation of the mixture and separate selection of the components of the mixture on an inclined section of the well with the selection of water near the wall of the column, opposite the wall along which the separated flow of oil and gas rises (UK Patent No. 2326895 , publ. 01/06/1999 - prototype).

The disadvantage of this method is the incomplete separation of small volumes of oil from large volumes of water.

The proposed invention solves the problem of separation and selection of small volumes of oil from large volumes of water.

The problem is solved in that in a method of downhole separation of a gas-oil mixture, including separation of the mixture and separate selection of the components of the mixture on an inclined section of the well with the selection of water near the wall of the column, opposite the wall along which the separated stream of oil and gas rises, according to the invention, in the process of separation of water-gas-oil mixtures on an inclined section of the well organize a slowdown in the flow rate of the mixture by transferring the flow to a pipe string of larger diameter, water withdrawal near the column wall, the false wall, along which the separated flow of oil and gas rises, is carried out through a shank located near the specified opposite wall, provided with holes along the shank facing the specified opposite wall.

SUMMARY OF THE INVENTION

Intra-well separation of a water-gas-oil emulsion with a low oil content presents certain difficulties because of the difficulty of separating and capturing small volumes of oil. 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 as follows.

Figure 1 presents the inclined section of the well; 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 (not shown) connected to the bottom, lowered into the production string of the deviated well 2. The upper part of the suspension consists of a tubing string (tubing) of large diameter 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 rows of inlet openings 6 along the entire length for the production 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 some 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 the operation of the electric centrifugal pump (not shown in the figure), 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, oil droplets float in the upward flow and when these droplets merge, a thin stream of oil forms along the upper forming surface of the tubing string of larger diameter 3. At the same time, 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 evenly distributed. Moreover, the velocity of the upward flow along the shank 5 after passing through each plane of the holes 6 decreases due to the partial selection of water, and inside the shank 5 increases 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 a high pressure hose 7 rises along a tubing string of a smaller diameter 4 to the wellhead, and oil - through a tubing string of a larger diameter 4.

Thus, the mixture is separated and the components of the mixture are selected separately, according to the invention, after the mixture is separated, water is taken on an inclined section of the well near the column wall opposite the wall along which the separated oil and gas flow rises.

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 the overwhelming amount from the stock of this category of wells.

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)

A method of downhole separation of a water-gas-oil mixture, comprising separating the mixture and separate selection of the components of the mixture on an inclined section of the well with water extraction close to the column wall opposite the wall along which the separated flow of oil and gas rises, characterized in that during the separation of the water-gas-oil mixture on the inclined section of the well they organize the slowing down of the flow rate of the mixture by transferring the flow into a pipe string of larger diameter, water withdrawal near the wall of the column, opposite the wall along which lying separated stream of oil and gas, is performed through the shank, disposed near said opposite wall, provided with openings along the shank facing the said opposite wall.

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