EA029770B1 - Oil production method - Google Patents

Abstract

The invention is related to the petroleum industry, in particular, to methods for oil production in oil fields at a late stage of exploitation featuring a large productive formation depth, low formation pressures, low productivity, the absence of a formation pressure maintenance and the absence of aquifer influence. The essence of the invention is as follows: maximum allowable dynamic fluid level is determined which, if exceeded, leads to a collapse of the production casing; after that an assembly including a packer and a submersible pump with a gas separator disposed above or under the packer is lowered into the well; the packer is installed above the production casing perforation interval lower than the depth of the maximum allowable dynamic level, at a maximum depth permitting bottom-hole pressure reduction to the limiting value ensuring maximum oil production volumes and maximum oil recovery factor; the annulus above the packer is filled with liquid so that the liquid column pressure balances the rock pressure at the packer installation depth; the submersible pump is operated to pump out the formation fluid from the oil pool through perforation holes to the under-packer space, after which the fluid is fed through the gas separator to the flow string and then to the well mouth, to the oil-gathering line. The technical result consists in a higher oil recovery factor, and higher total oil production volumes while eliminating the production column collapse.

Description

The invention relates to the oil industry, in particular to methods of oil production in fields at a late stage of development, characterized by a large depth of productive formations, low reservoir pressures, productivity, lack of reservoir pressure maintenance (PPD) and the influence of the border area. The inventive: determine the maximum allowable dynamic fluid level, above which a collapse of the production string occurs, and then a submersible pump with a gas separator located above or below the packer is lowered into the well on the tubing string; at the same time, a packer is installed above the perforation interval of the production string below the depth of the maximum allowable reduction of the dynamic level, at the maximum possible depth allowing the bottomhole pressure to be reduced to the maximum value ensuring the maximum oil production and oil recovery; the annulus of the well above the packer is filled with liquid, the pressure of the column which balances the rock pressure at the depth of the packer; include a submersible pump and carry out pumping of formation fluid from the reservoir through the perforations into the sub-packer space, followed by flow through the gas separator into the tubing string and then to the wellhead to the oil collection line. The technical result consists in increasing the oil recovery ratio and the total volume of oil production with the exception of the collapse of the production casing.

029770

The invention relates to the oil industry, in particular to methods of oil production in fields at a late stage of development, characterized by a large depth of productive formations, low reservoir pressures, productivity, lack of reservoir pressure maintenance (1111D) and the influence of the border area.

There is a method of oil production from layered reservoirs by drilling a horizontal wellbore in the middle of the reservoir with the wiring of horizontal branches below and above the main well [1].

However, in conditions of deep occurrence of the productive formation with low reservoir pressure and the absence of an IND system, this method will not allow to achieve the design oil recovery factor (KIN). As a result, some stocks will not be involved in development.

There is a method of extracting oil from a reservoir with abnormally low reservoir pressure [2], including the extraction of reservoir fluid using a submersible pump from vertical production wells drilled to form a sump, and in each vertical production well a cavity is created in the lower part of the reservoir, which is filled with filler , drill additional directionally producing wells, connecting, with the bottom of each directional well, with a cavity of the corresponding production vertical well, and the mouth of the field At the same time, directional producing wells communicate with the atmosphere, while vertical production wells are drilled with a diameter greater than the diameter of the directional wells.

The disadvantage of this method is. that in conditions of deep occurrence of a productive formation with abnormally low formation pressure, the implementation of this method will be unprofitable. In addition, the presence of low reservoir pressure and the absence of the 11D system will not technically allow to achieve the design CIN, since a decrease in dynamic levels in the wells above the maximum permissible values will lead to the destruction of production strings.

The closest to the technical nature of the claimed invention is a method of operating an oil production well [3], including the descent on the tubing of an electric centrifugal pump and gas separator, while before the descent of the electric centrifugal pump and gas separator in the well with the emphasis on the bottomhole or sump install a packer and a shank from pump-compressor pipes with a perforated lower part, which allows you to create the required rate of upward flow of reservoir fluids for the removal of produced water from the bottom and mechanical impurities, unpacking of the packer is carried out by the weight of the electric centrifugal pump, gas separator and part of the weight of the upstream tubing string.

This method does not allow for oil production in wells operating deep-seated formations without the 11D system with very low reservoir pressures, since the operation of such formations requires a significant reduction of the bottomhole pressure and, accordingly, the dynamic fluid level. A decrease in the dynamic level of the fluid in the well below the maximum allowable will lead to the destruction of the production string. The application of this method will not provide the project oil recovery and the achievement of the project oil recovery factor.

The objective of the invention is to create a method of oil production, allowing to reduce the bottomhole pressure in the well during oil production below the maximum permissible values, while avoiding the destruction of the production string under the action of rock pressure and thereby increase oil recovery factor and total oil production.

The problem is solved due to the fact that in the method of oil production the maximum permissible dynamic fluid level is determined, above which a production string collapses, and then a submersible pump located above or below the packer is lowered into the well on the tubing string. with gas separator; at the same time, the packer is installed above the perforation interval of the production string below the depth of the maximum allowable reduction of the dynamic level, at the maximum possible depth, which allows the bottomhole pressure to be reduced to the maximum value that ensures maximum production volumes and oil recovery factor; the annular space of the well above it is filled with liquid, the pressure of the column of which balances the rock pressure at the depth of the packer; include a submersible pump and carry out pumping of formation fluid from the reservoir through perforations into the sub-packer space, followed by flow through the gas separator into the column of pump-compressor pipes and further to the wellhead to the oil gathering line.

First of all, oil is sampled until the pressure in the reservoir drops to a value below the saturation pressure, at which free gas is released in the sub-packer space, which is removed via a downhole pipeline to the oil collection line.

In addition, when the reservoir pressure in the reservoir and podpaknernom space drops to a value close to zero, the well is transferred to the periodic operation mode, during which the recoverable oil reserves remaining in the reservoir are taken to ensure that fluid from the tubing string is prevented from leaking periodic stops of the submersible pump for accumulation in the sub-pakpernoy zone of the formation fluid.

The method of oil extraction is illustrated by drawings, where in FIG. 1 shows the well with the layout

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for oil production in which the submersible pump is located below the packer; in fig. 2 - well with oil production layout, in which the submersible pump is located above the packer.

A production column 2 with perforation holes 3 in which a packer 4 is installed at a depth H, below which is a submersible pump 5, for example, an electrical centrifugal one equipped with a gas separator 6, is installed in the well that discovered the productive formation in the form of a lenticular reservoir 1. and a check valve 7. The entire assembly is connected to the wellhead (not shown in the drawings) by means of a tubing string (tubing string) 8. In the sub-packer space 9, hydraulically connected through the perforations 3 with a lenticular deposit 1, downhole pipeline 10 is lowered (Fig. 1).

The method of extraction is as follows.

According to the task, the object of development and production of oil is a field characterized by a large depth of productive layers, low reservoir pressures, productivity, lack of a hydraulic injection system and the influence of the boundary area. In such a field, a single well is opened in a well with limited recoverable oil reserves, for example, a lenticular one. The reservoirs are cavern-pore-fractured limestone. Determine the maximum permissible dynamic level of the liquid H1, above which a collapse of the production string 2 occurs. In other words, the production string 2 is pressurized by reducing the level to the maximum possible depth H1. Produce the downhole layout and landing of the packer 4 at a depth H, significantly exceeding the maximum allowable depth of the level H1, allowing to reduce the bottomhole pressure to the maximum possible value, providing maximum oil recovery and oil recovery factor. Nadpaknernoe space 11 between the production column 2 and tubing (tubing) 8 fill with oil or other liquid (hereinafter-liquid) with a given density and volume, providing such a pressure of the liquid column, which would balance the mountain pressure of the packer 4 .

After switching on the submersible electrocentrifugal pump 5, the reservoir fluid from the lenticular reservoir 1 through perforation holes 3 enters the sub-packer space 9, into the submersible electrocentrifugal pump 5 and through the gas separator 6, the check valve 7 enters the lift column 8 and further to the wellhead to the oil recovery line (at the figure is not shown). Thus, an intensive oil extraction from the lenticular reservoir 1 is conducted. Over time, the pressure in it decreases to critical values below the saturation pressure. As a result, intense excretion begins; free associated petroleum gas, which accumulates under the packer and from the under-packer space through the well pipeline 10, is diverted to the wellhead, where it is utilized. Oil production is carried out up to almost the maximum possible, close to zero, reduction of reservoir pressure in the lenticular reservoir 1 and the sub-packer space 9. Subsequently, the well is transferred during periodic operation, during which all remaining recoverable oil reserves in the lenticular reservoir 1 are withdrawn. At the same time, the check valve 7 prevents fluid from the tubing 8 from leaking during periodic stops of the submersible electrocentrifugal pump 5 to accumulate in the sub-packer zone of the formation fluid. In the case of the installation of a submersible pump 5 above the packer 4 (Fig. 2), the shank 12 is pulled down under the packer, and the pump 5 is installed in a sealed casing 13 hydraulically connected through the shank 12 to the sub-packer space 9.

Consider the implementation of the method on the following example.

At the N field at a depth of 2724-2765 m in the Boritshevsky deposits of the Lebedyansky horizon, one well 2 opened a lenticular reservoir 1 with 50,000 tons of recoverable oil reserves. The reservoirs are limestone cavern-pore-fractured. The production column is pressurized by reducing the level to the maximum possible depth H1 = 1,400 m. In the initial period of well operation and oil production from the reservoir, until the dynamic level reaches H1 = 1,400 m, the cumulative production reached 28050 tons. 0.287. Reservoir pressure decreased from 28.6 to 16.5 MPa. Further operation of the well with a reduction in bottomhole pressure to values at which the dynamic level decreases below H1 = 1400 m can result in the integrity (collapse) of the production string being disrupted, since the opened lenticular formation 1 lies in the fluid plastic salts. Therefore, for further oil production, increasing the oil recovery factor and increasing oil recovery into the production string (well) 2 on pump-compressor pipes (tubing string) 8, a bottom-up layout was lowered: electric centrifugal pump 5 with gas separator 6, check valve 7 and packer 4 ( see fig. 1). Since the electric centrifugal pump is located under the packer, the layout was equipped with a well pipeline 10 to remove free gas from the sub-packer space to the oil gathering line. at a depth of 2720.5 m. To balance the pressure of rocks on the production string, the annulus 11 above the packer to the mouth was filled with oil, with a density of 860 kg / m ³ . By applying electricity to the cable

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electric motor of centrifugal pump 5, the well was put into operation. The reservoir fluid from the reservoir 1 through the perforation interval 3 (Fig. 1) by the electric centrifugal pump 5 through the gas separator 6 and the check valve 7 through the tubing string 8 is fed to the oil collection line (not shown). After reducing the bottomhole pressure in the subpacker zone below 12 MPa, which corresponds to the oil saturation pressure of gas, in the subpacker zone by the gas separator 6, the associated gas began to rapidly separate. Separated gas separator 6 gas rises up to the packer and the well pipeline is diverted to the mouth of the oil collection line. Continuous well operation continued until the reservoir pressure decreased to 7.3 MPa. Further, due to a decrease in well production below the values at which stable operation of an electric centrifugal pump is possible (operation without supply disruptions), the well was put into periodic operation with a sampling period of 2.5 hours and an accumulation period of 7.5 hours. valve 7 prevented it from flowing from the internal cavity of the tubing 8 into the sub-packer space 9. In batch mode, the well was operated until the formation pressure decreased to 3.5 MPa, at which further oil production became unprofitable. In this reservoir pressure well was transferred to conservation. During the period of oil production by the present method, 30136 tons of oil were additionally extracted from the reservoir. At the same time, the oil recovery rate reached 0.334 and exceeded the design value by 0.047, i.e., by 4.7%.

Thus, the organization of oil production by the proposed method allows to reduce the bottomhole pressure in the well to almost the limit, close to zero value, without the threat of crushing of the production string and in the last periods of the reservoir, when the reservoir pressure is also minimal, by periodic operation to select all recoverable reserves reaching the maximum CIN.

Information sources:

1. CI 2431038, IPC E21V43 / 16, publ. 10.10.2011.

2. CI 2501940, IPC E21V43 / 12, publ. 12/20/2013

3. Ki 2225938, IPC E21V43 / 00, publ. 03/20/2004

Claims (1)

CLAIM The method of oil production, which determines the maximum allowable dynamic liquid level, with a decrease below which collapse of the production string occurs, after which a submersible pump with a gas separator located above or below the packer is placed into the well on the tubing string providing the hydraulic connection of the subpacker space with the wellhead; at the same time set the packer over the perforation interval of the production string below the depth of the maximum allowable reduction of the dynamic level; the annulus of the well above the packer is filled with liquid, the pressure of the column which balances the rock pressure at the depth of the packer; include submersible pump and carry out the selection in a constant mode of formation fluid from the reservoir through the perforations into the sub-packer space with the subsequent flow through the gas separator into the tubing string and then at the wellhead to the oil gathering line; however, the selection in the continuous mode is carried out until the bottomhole pressure drops below the saturation pressure, at which free gas is released in the sub-packer space, which is removed via a downhole pipeline to the oil collection line; when the bottomhole pressure drops to a value close to zero, the well is transferred to the periodic operation mode, during which the recoverable oil reserves remaining in the reservoir are taken to prevent the leakage of fluid from the tubing string during periodic stops of the submersible pump for accumulation in the underpacking formation fluid zone. - 3 029770