RU2267005C2 - Method and device for sand plug removal from well bottom and gravel filter aggregation - Google Patents

Abstract

FIELD: oil and gas production, particularly to wash out and remove sand from well bottom and to aggregate gravel filter at well bottom.

SUBSTANCE: method for washing out sand plug at well bottom and carrying thereof to ground surface, arranging sand filter within predetermined interval and aggregating gravel filter in space behind the filter involves lowering sand filter and packer carried by pipe string in the well and flushing sand with flushing liquid under hydraulic pressure. The sand filter is provided with means creating high-pressure jet of flushing liquid having stem of removable packer part, packing gland and check valve with choke diaphragm. Distribution device provided with inner and outer bushes is arranged above the sand filter. After sand plug flushing out and removal and sand carrying out sand filter is installed within the given interval, inner and outer spring-loaded bushes are lowered by dropping a ball into pipes of the string. Gravel filter is aggregated by passing thereof through the pipes under elevated pressure into space located behind the filter between sand filter and filtering zone of the bed along with working fluid injection in hole annuity to prevent gravel level lifting above filter one. After that gravel and liquid supply is stopped and gravel is forced from pipes into the bed. Stem of removable packer part is lifted above packing gland to carry the ball to ground surface by reverse circulation creation and then the packers are set. Device comprises sand filter carried by pipe string and gravel supply unit arranged above the sand filter. To remove sand plug from well bottom device additionally has packer with removable upper part provided with stem, packer gland and check valve having chick diaphragm. The check valve is arranged under packing gland. Gravel supply unit is formed as distribution device with inner and outer spring-loaded bushes. Inner spring-loaded bush has seat for receiving ball to be dropped in the pipe.

EFFECT: increased overhaul time, reduced well repair time and quality due to decreased number of trips.

5 cl, 2 dwg

Description

The present invention relates to technologies for product extraction from oil, water and gas wells, and in particular to methods of erosion and removal of sand from the bottom of the wells, the washing of gravel filters at the bottom and devices for implementing these methods.

There is a method of sand removal during operation of a well filter, including the descent of the filter on the tubing (hereinafter referred to as N / K) pipes at a predetermined interval of the well and the removal of sand suspended by flushing fluid under hydraulic pressure (Bulatov A.I. et al. Handbook for flushing wells. - M .: Nedra, 1984, p. 59-60).

The disadvantage of this method is that the insufficient frequency of washing creates conditions for the formation of sand plugs with overlapping reservoir, which entails a seizure, and consequently, the breakage of N / K pipes when they are raised and additional emergency fishing operations, the overhaul period is reduced.

The closest in technical essence is the method of sand removal during operation of the downhole filter, which includes the descent of the filter on N / K or other pipes and the suspension of suspension with flushing fluid under hydraulic pressure, and on the N / K (or other pipes) a self-sealing cuff is placed, between a circulation valve is placed by a filter and a self-sealing cuff. At the moment of sand suspension removal, the self-sealing cuff is fixed above the reservoir (RF patent No. 2110671, Method for sand removal during operation of the downhole filter, published on 1998.05.10).

The disadvantage of the prototype is that this method still does not exclude the formation of a sand cork and the overlap of the reservoir with all the ensuing negative consequences. The formation of a sand cork (sometimes up to 50 m high) occurs due to the absence of a packer above the well filter, and the self-sealing cuff is an obstacle when the cork is eroded to bring it to the surface.

There is also known a method of constructing a gravel filter, in which, on a pipe string N / K, a filter is lowered into the well with a unit installed above it for feeding gravel. The latter is served in the filter zone in the working agent. The gravel supply unit comprises a housing with side holes and a stop, a pusher, a sleeve movable relative to the housing with a central cylindrical channel. The sleeve has side openings placed against the side openings of the housing (A.S. USSR No. 1184928, class E 21 B 43/08, 1984).

A disadvantage of the known methods and devices is that they can only work if the wellbore and bottomhole are clean (i.e. there is no sand plug in the bottom) and the descent of the downhole sand filter (hereinafter PPF) to the perforation interval is ensured. In the case of lowering the PPF in the presence of a sand plug at the bottom, the supply of a flushing agent inside the PPF leads to circulation, in which the flow from the filter does not go to the bottom, but leaves the side surfaces of the PPF, which makes it impossible to wash the sand plug. Therefore, the wellbore before lowering to the bottom of the PPF requires retraining and often repeated, which lengthens the repair time of the well and requires several trips. Only after erosion and the absence of a sand plug in the face, is the operation of installing a filter and washing (construction) of a gravel filter.

The objective of the invention is to increase the period of the overhaul period and reduce the period of repair of the well by reducing the number of tripping operations and the implementation of one tripping operation:

- erosion of sand plugs at the bottom and removal of sand to the surface;

- installation of PPF in a given interval;

- washing the gravel filter into the filter space (i.e., into the space between the PPF and the filter zone of the reservoir).

The problem is achieved in that in the method of removing sand plugs from the bottom, including the descent of the sand filter (PPF) and the packer on the pipe string into the well and the suspension of sand by washing liquid under hydraulic pressure to the surface, the PPF is equipped with a device for creating a high-pressure jet of washing liquid, including a shank of the removable part of the packer, an packing box and a check valve with a nozzle diaphragm, while a switchgear with internal and external springs is placed above the PPF After washing and removing sand plugs, as well as sand suspension, the PPF is installed in a predetermined interval, the inner and outer spring-loaded bushings are lowered by throwing the ball into the pipes and the gravel filter is washed through the pipes into the filter space between the PPF and the filter zone of the formation with injection into the annulus of the working fluid to prevent the gravel from rising above the filter, after which the supply of fluid with gravel is stopped and gravel is forced into the reservoir from the pipes, the shank of the removable part of the packer is wrinkled above the stuffing box and by creating reverse circulation the ball is washed to the surface, then the packer is packaged.

The task is also achieved by the fact that the device for washing the gravel filter containing a sand filter installed on the pipe string (PPF) and a unit for feeding gravel located above it, to enable sand plugs to be removed from the bottom, additionally contains a packer with an upper removable part equipped with a shank , packing box and check valve equipped with a fitting diaphragm, while the check valve is located under the packing box, and the gravel supply unit is a distributor an integral device with internal and external spring-loaded bushings, wherein the internal spring-loaded bush has a seat for a ball being thrown in.

The shank of the removable part of the packer is concentrically located in the PPF and is an elevator pipe with a diameter of 33-48 mm and a length selected so that the distance between its bottom and the check valve allows the packer to be packaged.

The switchgear with internal and external spring-loaded bushings includes a housing, a system of internal and external windows, upper and lower sub, and its internal and external spring-loaded bushings have seals that ensure tightness between the housing and the sleeve in the upper position.

The gland box is located directly under the PPF and overlap the annular space between the elevator pipe and the PPF. The check valve is placed under the PPF and the stuffing box and is equipped with a fitting diaphragm located in the shoe of the check valve and having an opening of 12-15 mm.

The device for creating a high-pressure jet, including the shank of the removable part of the packer (lift pipe), the stuffing box and the check valve with a nozzle diaphragm, allows you to create a high-pressure jet of flushing liquid under the shoe of the check valve, which allows you to erode the sand plug on the bottom of the well, i.e. perform direct circulation and exclude reverse circulation and sand entering the filter through the check valve during well operation.

The gland box isolates the annular space between the elevator pipe and PPF from the jet of liquid exiting the elevator pipe and allows directing the entire flow of flushing fluid directly through the check valve and shoe equipped with a fitting diaphragm to the bottom.

The nozzle diaphragm is used to create a high speed jet of flushing fluid emerging from the elevator pipe.

A distribution device for washing the gravel filter is installed between the packer and the filter (PPF) and the pipes are used to wash the gravel filter under pressure into the filter space between the PPF and the filter zone of the formation with injection of working fluid into the annulus to prevent gravel from rising above the filter. The packing density of the sand of a gravel filter washed with a switchgear is higher than the packing density of sand made during a quiet outflow (i.e. washed in a known manner), because under pressure, the distribution of gravel (sand) particles takes on a hexagonal sphere. In addition, the washing of the gravel filter through the switchgear is carried out at an installed in the specified interval PPF without additional verification of the cleanliness of the wellbore and the bottom, thereby saving one tripping operation.

The combination of the application of the above technological operations and structural elements allows to increase the period of the overhaul period, to improve the quality and reduce the time of well repair by reducing the number of tripping operations and performing the assembly in one operation:

- erosion of sand plugs at the bottom and removal of sand to the surface;

- PPF settings in a given interval;

- washing the gravel filter into the filter space (i.e., into the space between the PPF and the filter zone of the reservoir).

All this ensures the implementation of the task.

Figure 1 presents the layout of the equipment for implementing the proposed method; figure 2 - switchgear for washing gravel filter.

The layout scheme includes a packer 1 having a removable upper part 2, a switchgear for washing a gravel filter 3, a sand filter (PPF) 4, an oil seal box 5, a check valve 6 with a nozzle diaphragm 7 in the valve shoe. The removable upper part of the packer 2 is equipped with a shank representing an elevator pipe 8 located concentrically in the PPF having a diameter of 33-48 mm. Its length is selected so that the distance between the bottom of the pipe and the check valve 6 allows the packer to be packaged. The gland box 5 and the check valve 6 with a fitting diaphragm 7 are made of known elements in the form of a device mounted below the PPF.

The distribution device 3 includes a housing 9, an inner 10 and an outer 11 spring-loaded bushings with seals that ensure tightness between the housing and the sleeve in the upper position, a window system (inner 12 and outer 13), upper 14 and lower 15 sub.

The method is carried out and the device operates as follows.

The filter (PPF) 4 is lowered onto the pipe N / K string with an oil seal box 5 installed under it, a check valve 6 with a nozzle diaphragm 7 and a switchgear 3 located above it and a packer 1 with an upper removable part 2 equipped with an elevator shank pipe 8 passing inside the filter and stuffing box. The erosion of the sand plug formed at the bottom of the well begins. Through the elevator pipe 8, lowered below the filter, a stream of washing liquid is circulated. In this case, the jet passing through the N / K pipes and the lift pipe 8, isolated from the internal cavity of the filter 4 by the packing box 5 (packing box 5 prevents the washing liquid from penetrating the filter, isolating the annular space between the filter and the lift pipe), passes through non-return valve 6, shoe and nozzle diaphragm 7 on the erosion of sand plugs.

The speed of the jet exiting after the nozzle diaphragm is so high that it can wash away even dense plugs. After washing the plugs, the washing of the well is continued until it is completely cleaned of solids. After erosion and removal of the sand plug and removal of the sand suspension, PPF 4 is installed at a predetermined interval, the inner 10 and outer 11 spring-loaded bushings are lowered by throwing the ball into the N / K pipes (for landing in the saddle of the inner sleeve 10).

After the ball is planted under the influence of the fluid flow pressure from the N / K pipes, the spring-loaded inner sleeve 10 is lowered down to open the inner window 12, and then the spring-loaded outer sleeve 11 is successively lowered under pressure, and the outer window 13 is opened, through which the fluid flow with gravel is directed to the filter the space (i.e., the space between the PPF 4 and the filter zone of the reservoir) and the formation, i.e. start reclamation of the gravel filter. To prevent gravel from rising above the filter, the working fluid is pumped into the annulus at a low speed. The increase in pressure in the annulus determines the moment of formation saturation with gravel. The supply of liquid with gravel is stopped and gravel is forced into the reservoir from N / K pipes.

After completing the push, the lap top of the packer 2 in the left thread of the packer is folded.

By creating a load from the weight of the N / K pipes on the fixed part of the packer, packing is performed. Raise the suspension of N / K pipes with the removable part of the packer 2 and the shank (lift pipe 8) to the required height (lift pipe 8 remains in the filter above the stuffing box), create a reverse circulation and wash the ball to the surface.

The washing of gravel under pressure determines the formation of the structure of the washed filter having a hexagonal sphere, which sharply reduces the cross section between grains of gravel (sand) and allows you to create a reliable filter - a barrier to the breakthrough of sand into the well.

After dismantling the anti-aircraft defense (blowout control equipment) and installing the fountain fittings, the well is ready for operation.

The proposed method of removing sand plugs from the bottom and reclaiming a gravel filter and a device for its implementation were tested in the wells of the Anastasievsko-Troitsk field, because these wells are characterized in that during tripping operations, even during repression, they add a sand plug to the bottom of the well. The magnitude of this cork can vary widely (0.5-10 m). Field tests for performance were performed on the surface at well No. 1651 Troitskaya with a positive result and a recommendation for industrial use in other wells.

The present invention increases the overhaul period, the quality of repairs and provides more reliable operation of the well. In addition, the well repair time is reduced by 2.5 days due to:

- launching PPF to the bottom of the well with a sand plug without retraining the wellbore - 1.5 days;

- simultaneous washing of sand at the end of the launch of the PPF, which does not require separate preparation of the well - 1 day. Considering that up to 5 operations are performed per month, the annual savings will be: 2.5 × 5 × 12 = 150 days. If we take the cost of 1 team hour equal to 918 rubles / hour, the approximate annual economic effect will be: 918 × 150 × 24 = 3304.8 thousand rubles.

Claims (5)

1. The method of removing sand plugs from the bottom, including the descent of the sand filter (PPF) and the packer on the pipe string into the well and the removal of sand suspension by washing fluid under hydraulic pressure to the surface, characterized in that the PPF is equipped with a device for creating a high-pressure jet of washing fluid, including the shank of the removable part of the packer, the stuffing box and the check valve with a nozzle diaphragm, while a switchgear with internal and external spring-loaded bushings is placed above the PPF e washing out and removing sand plugs, as well as carrying out a suspension of sand, install PPF in a predetermined interval, lower the inner and outer spring-loaded bushings by throwing the ball into the pipes and wash the gravel filter under pressure into the filter space between the PPF and the filter zone of the formation with injection into the annulus the space of the working fluid to prevent the gravel from rising above the filter, after which the supply of fluid with gravel is stopped and gravel is forced into the reservoir from the pipes, the liner is removed second portion of the packer and above the stuffing box creation reverse circulation eluted ball on the surface, then produce packer packer. 2. A device for washing a gravel filter, comprising a sand filter (PPF) installed on the pipe string and a gravel supply unit located above it, characterized in that it additionally comprises a packer with a removable top equipped with a shank to remove sand plugs from the bottom; , packing box and check valve equipped with a fitting diaphragm, while the check valve is located under the packing box, and the gravel supply unit is a distribution device with internal and external spring-loaded bushings, and the internal spring-loaded sleeve has a seat under the ball to be thrown. 3. The device according to claim 2, characterized in that the shank is an elevator pipe with a diameter of 33-48 mm and a length selected in such a way that the distance between its bottom and the check valve allows you to pack the packer. 4. The device according to claim 2 or 3, characterized in that the switchgear with internal and external spring-loaded bushings includes a housing, a system of internal and external windows, upper and lower sub, and its internal and external spring-loaded bushings have seals that ensure tightness between the housing and the sleeve in the upper position. 5. The device according to one of claims 2 to 4, characterized in that the nozzle diaphragm is located in the shoe of the check valve and has an opening of 12-15 mm.

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