RU2258133C1 - Method for obtaining hard to recover oil reserves - Google Patents

Abstract

FIELD: oil production industry, particularly to obtain hard to recover oil reserves, mainly for carbonate reservoirs of nonuniformly saturated laminated stratums.

SUBSTANCE: method involves installing mast for swabbing on landing flange with the use of bolt connection with choosing height thereof of 3-4 m before downhole work initiation; successive grouping swabbed wells in dependence of obtained results after downhole work completion; operating wells in which output was increased or recovered in prior mode, namely in mechanized one, with bore-hole pump usage. Wells in which high output is obtained due to swabbing are operated under swabbing conditions. Wells in which output did not increase are operated with the swab usage by alternating product accumulation cycle with cycle of product pumping from well.

EFFECT: increased efficiency due acting on stratum by swabbing thereof with taking under consideration well conditions.

2 cl, 2 dwg

Description

The invention relates to the field of oil and gas industry and will find application in the extraction of hard-to-recover oil reserves, mainly for carbonate reservoirs of heterogeneously saturated layered formations.

The well-known "Method of periodic operation of a low-yield well with a deep-well pumping unit" [1], which consists in alternating the cycles of accumulation of fluid and its pumping, equipped with a sump. In this case, the minimum permissible bottomhole pressure and the corresponding annular pressure are first determined taking into account the magnitude of the depression on the formation, corresponding to the maximum allowable productivity of the well and the condition of the formation's safety. In the processes of accumulation and pumping fluid from the well, the magnitude of the annular pressure is controlled. With an increase in its value during the accumulation process and a decrease in the pumping process, gas is vented from the annulus or gas is injected into this space to maintain annular pressure at a certain point and to restore in both cases the value of the selected working depression on the formation.

The method for certain wells with low viscosity oil can play a positive role and get an increase in flow rate.

However, its use is limited in that it does not take into account the viscosity of the reservoir oil. As you know, oil fields with hard-to-recover oil reserves are characterized by a high content of asphalt-resinous substances, as well as paraffin. They not only clog the well filter, but also the downhole pump, which necessitates frequent treatments with thermochemical methods, which is associated with additional tripping operations to remove the pump.

In addition, for the implementation of the method, it is necessary to lay a gas pipeline, which is also economically disadvantageous - it increases the cost of oil production.

A device for oil production [2] is known, the patent description of which describes a method of oil production by exposing the reservoir to swab using an installation that includes a drive with a cable drum, through which a pump pipe (tubing) string into the cavity a piston (swab) is mounted with the possibility of letting the borehole fluid through it and lifting it to the surface, and withdrawing it to the collection point during its reciprocating movement.

The method provides for the use of a reciprocating piston pump of the swab type instead of traditional deep-well pumps running on rods or on a geophysical cable of a centrifugal pump.

The known method in technical essence is closer to the proposed one and can be adopted as a prototype.

The disadvantage of this method is that the transfer of all numerous wells to oil production by swabbing is not economically feasible without taking into account the geological and technical condition of the well and its hard-to-recover oil reserves. This is due to the fact that the dismantling of ground equipment, the lifting of underground equipment from the well, as well as the installation of a swab installation - all these operations take a lot of time and labor. In addition, long downtime of the well reduces the rate of oil production, worsens the production capabilities of the well due to irreversible processes that occur in the bottom-hole zone of the formation in terms of deteriorating reservoir properties of the formation, and its restoration is also associated with large expenditures of time, material resources and labor, attraction of technical means.

The objective of the present invention is to remedy the above disadvantages of the prototype.

The problem is solved by the described method, including the impact on the reservoir by swabbing in order to increase oil production or restore the flow rate of low-yield wells.

What is new is that before starting work in each well, the mast of the swab installation is mounted on the column flange of the well using a bolt connection, choosing a height of at least 3-4 meters, and after completion of work in each well from the number planned for swab, depending on the results obtained, they are sequentially grouped: into wells in which an increase in flow rate or its recovery is obtained - they are operated in the previous mode, i.e. mechanized method using a deep pump and to wells in which a high flow rate was obtained only during swab compared with the mechanized production method, they continue to be operated in swab mode, and in those wells in which there are no positive results in changing the flow rate upwards, they are exploited using swab by alternating the cycles of accumulation of products of its pumping from the well.

Another difference is that before the descent into the well, the swabs are equipped with check valves that work to close from the wellhead.

The presented drawings explain the essence of the invention, where Fig.1 shows a General view of the installation for the extraction of hard-to-recover oil reserves of the proposed method in operation, in partial section; figure 2 is a section along aa of figure 1.

Installation for implementing the proposed method contains a mast made of welded tubular structures, to the posts 1 of which the bases 2 and 3 are rigidly fixed, the upper and lower, respectively, made in the form of a disk with a central hole for the cable 4. On the upper base 2 with the help of eyes 5 is installed upper guide roller 6. The lower base 3 with the lower guide roller 7 is fixed to the column flange 8 by means of a bolt connection. The lower roller by the cheeks 9 is connected by a bolt 10 to the bracket 11 of the lower base with the possibility of rotation in the vertical direction. The bracket using a bolt 12 is connected to the plate 13, which is bolted 14 and 15 and spacer sleeves 16 connected to the lower base 3 of the mast with the possibility of horizontal rotation. Thus, the lower roller is mounted with the possibility of orientation relative to the drum with the winch rope 4, which also includes a gearbox and an electric motor (winch not shown). Reliable mast stability is ensured by tie-rods 17.

The method is carried out in the following sequence.

First, the number of wells in a given oil field to be swabbed is determined. There may be dozens, hundreds or more of such wells awaiting stimulation, including those that have been released, depending on the large or small given oil field.

Before starting work in the well, the mast with a height of at least 3-4 m described above, the swab installation is mounted using a bolt connection on the column flange of the well (see figure 1), and the bottom of the swab is equipped with a check valve that works to close from the side of the well . The winch of the installation is equipped with a control unit with a two-cycle program and tuning to the optimal operating mode (the control unit is not shown). Then the rope 4 is passed through the lower and upper guide rollers 6 and 7 and its end is fixed to the swab with the load (swab not shown). Then the drum is released from the brake and it begins to rotate, unwinding the rope, and thereby lowering the swab into the tubing string 18 under its own weight. If necessary, to speed up the descent, the swab is supplied with cargo. When the swab reaches the static level of the well fluid, its valve opens, and the fluid begins to flow into the cavity of the tubing string. As the swab moves to the required depth according to a given program, the fluid available in the well fills the cavity of the tubing string. Further, according to the program of the control unit, the winch motor is turned on, the winch gear starts to rotate the drum in the opposite direction - the swab rises. When the swab moves up, the valve closes under the weight of the liquid and the liquid above the swab enters through the discharge pipe 19 of the wellhead fittings into the line or tank transporting the liquid. After the swab reaches the upper lifting point, the control unit program turns off the electric motor. Swab, under its weight and load, again begins to move down, and the cycle repeats by stimulating the wellbore, the duration of which sometimes lasts up to a month or more.

As work is completed in one well, swabbing operations can be carried out in parallel and in several wells, depending on the results obtained, they are successively grouped: into wells in which an increase in flow rate is obtained or its recovery is transferred to operation in the previous mode, i.e. mechanized method with the help of deep pumps, and for wells in which high flow rates were obtained only during swab compared with the mechanized method of production - they continue to be operated in swab mode, and in those wells in which positive results were not obtained in changing the flow rate upwards , they are exploited using a swab by alternating the cycles of product accumulation and pumping from the well.

At the end of work in all planned wells of this oil field, they then switch to other, or similar work is carried out in parallel.

The technical and economic advantage of the invention is as follows.

The use of the invention in oil fields provides optimization of the development of oil reservoirs, reducing the cost of time and materials due to other expensive types of treatment of reservoirs to stimulate them, as well as reducing labor costs.

Sources of information

1. Pat. RF №2193648, 7 Е 21 В 43/00, BI №33, 2002

2. Pat. RF №2172391, 7 Е 21 В 43/00, BI №23, 2001 (prototype).

Claims (2)

1. The method of extraction of hard-to-recover oil reserves by swabbing the reservoir to increase oil production or to restore the flow rate of low-production wells, characterized in that before starting work in each well, the mast of the swabbing installation is mounted on the column flange of the well using a bolted connection, selecting it a height of at least 3-4 m, and after completion of work in each well from among those planned for swabbing, depending on the results obtained, they are successively grouped: wells in which an increase in flow rate or its recovery is obtained, they are operated in the previous mode, i.e. mechanized way, using a deep pump, and to wells in which a high flow rate was obtained only during swab compared with the mechanized production method, they continue to be operated in swab mode, and wells in which there are no positive results in changing the flow rate upwards, operate using swab by alternating the cycles of accumulation of products of its pumping from the well. 2. The method according to claim 1, characterized in that before the descent of the swabs into the well, they are equipped with check valves working to close from the side of the wellhead.

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