Device and method of productive formation selective processing

Abstract

There are proposed a method for selective processing of a productive formation and a device for implementation thereof coupled with a tubing. The device is lowered to the formation’s lowest interval and fixed therein. Working fluid is supplied into the device’s hydraulic fracturing port, the interval is isolated with sealing elements, and hydraulic fracturing is executed. An annular gap is flushed with flush fluid, the lower packer is activated and debris is washed out of the gap through a hydraulic fracturing port. The device is turned to the transport position. The tubing is moved shifting the device’s hollow rod and flushing holes are opened. Flush fluid is then fed into the tubing, the sealing elements are activated and debris is washed out of the gap’s lower area pushing the mixture along the device’s inner cavity into the well. Then the device is moved to the next interval for further processing.

Claims

1. A device for selective processing of a productive formation essentially coupled with a tubing insertable into a well casing associated with the productive formation; said well casing defines an inner sidewall surface thereof and has a diameter; said tubing defines an outer surface thereof; said device defines an outer surface thereof; wherein an annulus space is defined to include: a space between the outer surface of said device and the inner surface of said well casing, and a space between the outer surface of said tubing and the inner surface of said well casing; wherein said device comprises sequentially mounted on the tubing from bottom to top: a mechanical anchor; a collar locator; a lower feedthrough packer equipped with a number of cup seals; said lower feedthrough packer defines a lower packer inner cavity provided therein; said lower feedthrough packer has a hollow rod capable of axial movement at least within the inner cavity of said lower feedthrough packer; said hollow rod is partially passed through the collar locator, and partially passed through and rigidly connected to the mechanical anchor; a hydraulic fracturing port divided by a partition into an upper part including an upper cavity provided with windows and a lower part provided with a recess and flushing holes communicated with the recess; said number of cup seals of the lower feedthrough packer are directed towards the hydraulic fracturing port; an upper feedthrough packer equipped with a number of cup seals directed towards the hydraulic fracturing port; and a centralizer; wherein: an inter-packer annular gap is defined as a portion of the annulus space located between the outer surface of said device and the inner sidewall surface of said well casing, vertically limited by positions of the upper feedthrough packer and the lower feedthrough packer; said flushing holes provide for hydraulic connection of the inter-packer annular gap with said recess in the partition lower part; and wherein: a distance between the lower feedthrough packer and the flushing holes does not exceed said diameter of the well casing multiplied by two.

2. The device according to claim 1 wherein seals placed above and below the flushing holes.

3. The device according to claim 1, wherein said hollow rod defines a rod inner cavity within thereof; said collar locator defines a collar inner cavity within thereof, and wherein the rod inner cavity, the lower packer inner cavity and the collar inner cavity form a single flushing channel.

4. A method for selective processing of the productive formation using the device according to claim 1; wherein the productive formation includes a number of intervals; said method comprising the steps of: lowering the tubing with the device to a lowest interval chosen from said number of intervals; setting up the lowest interval within the inter-packer annular gap; fixing the device to the well casing by the mechanical anchor; supplying working fluid under pressure into the tubing and into the hydraulic fracturing port; isolating the lowest interval by said number of cup seals of the lower feedthrough packer and said number of cup seals of the upper feedthrough packer; providing hydraulic fracturing of the lowest interval by the working fluid; feeding the flush fluid into the inter-packer annular gap; activating the lower feedthrough packer and washing debris out of an upper portion of the inter-packer annular gap through said windows of the hydraulic fracturing port and up the tubing; turning the device into a transport position; axially moving up the tubing thereby shifting the hollow rod and opening the flushing holes; feeding the flush fluid under pressure into the tubing; activating said number of cup seals of the lower feedthrough packer and said number of cup seals of the upper feedthrough packer and washing debris out of a lower portion of the inter-packer annular gap and pushing a mixture of the flush fluid and the debris mixture along said inner cavity of the device into the well casing; moving up the device to a next interval chosen from said number of intervals, and repeating the steps above.

5. The method according to claim 4 wherein said well casing defines a top entrance thereof and a ground surface surrounding the top entrance, and wherein the flush fluid is supplied by a pumping unit positioned on the ground surface.

6. The method according to claim 4 wherein the step of turning the device into the transport position is provided by deactivation of the mechanical anchor.

7. The method according to claim 4 wherein said well casing defines a top entrance thereof and a ground surface surrounding the top entrance; and wherein the debris froman upper portionof the inter-packer annular gap is pushed up along the tubing and being disposed of on the ground surface.

8-9. (canceled)

Description

DRAWINGS OF THE INVENTION

[0057] FIG. 1 - general view of the device;

[0058] FIG. 2 - enlarged view of the hydraulic fracturing port;

[0059] FIG. 3 - longitudinal section of the device in the transport position;

[0060] FIG. 4 - longitudinal section of the device with an activated mechanical anchor;

[0061] FIG. 5 - enlarged view of the hydraulic fracturing port in the position of the device shown in FIG. 3;

[0062] FIG. 6 - longitudinal section of the device during hydraulic fracturing;

[0063] FIG. 7 - working fluid flow diagram with an activated anchor; and

[0064] FIG. 8 - working fluid flow diagram with a deactivated mechanical anchor.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENT THE INVENTION

[0065] The present invention is designed for selective processing of a productive formation in the oil mining industry. Generally, a borehole associated with the productive formation is provided and a well casing 23 is mounted within the borehole. A tubing 22 is typically inserted into the well casing 23. The inventive device essentially coupled with the tubing 22 comprises: a mechanical anchor 1, a collar locator 2, a lower feedthrough packer 3, a hydraulic fracturing port 4, an upper feedthrough packer 5 and a centralizer 6 sequentially installed from bottom to top on the tubing 22 (FIG. 1, FIG. 2). The mechanical anchor 1 and the collar locator 2 each defines an inner cavity located therein. An annulus space is herein defined as a space between an outer surface of the inventive device / tubing 22 and, on the other hand, an inner surface of the well casing 23.

[0066] Pipes 7 are connected to the centralizer 6, the installation of which is determined by the need and conditions for processing intervals of the productive formation of variable length.

[0067] The lower feedthrough packer 3 includes cup sealing elements 8 directed towards the hydraulic fracturing port 4. The upper feedthrough packer 5 includes cup sealing elements 9 also directed towards the hydraulic fracturing port 4.

[0068] The following well-known devices can be used as functional parts: [0069] mechanical collar locator, which can be similar to the collar locator A 1025-2, e.g. presented in the catalog “Tools for current and major repairs of wells”, p. 31 <https://www.slb.ru/upload/iblock/d8e/katalog-instrumentov-dla-tekushego-i-kapitalnogo-remonta-skvaiin.pdf>); [0070] centralizer e.g. presented in <http://www.coilsolutions.com/products/downhole-tools/drill-and-milling-tools/fluted-centralizers/> or <http://petrolibrary.ru/preduprezhdenie-iskrivleniya-vertikalnyix-skvazhi-skvazhin.html>; [0071] mechanically operated axial anchor (YAMO-3, YAMO-2), e.g. presented in <https://npf-paker.ru/catalog/type/yakorya/mekhanicheskie/yamo3-yamo2-yam3-yam2>.

[0072] A casing of the hydraulic fracturing port 4 includes windows 10 (FIG. 2). The hydraulic fracturing port 4 contains a partition 11 located inside the casing of the hydraulic fracturing port with a recess 12 in its lower part, and a divider 13 in the upper part (FIG. 3). In addition, radial flushing holes 14 are made in the lower part of the hydraulic fracturing port 4, connecting the recess 12 with the annulus space.

[0073] The lower feedthrough packer 3 defines an inner cavity 19 within thereof (FIG. 7). A hollow rod 15 is at least partially located in the inner cavity 19 of the lower feedthrough packer 3, with the possibility of axial movement, rigidly connected to the mechanical anchor 1 with a cone 16. The hollow rod 15 defines its own inner cavity within thereof.

[0074] Sealing capacity of the radial flushing holes 14 is ensured by seals 18 installed on an inner surface of the partition 11 above the holes 14 and on an inner surface of the lower feedthrough packer 3 below the holes 14.

[0075] On a side of an outer surface of the hollow rod 15, it is equipped with limiting protrusions 17 that perform axial movement along the cavity 19 on the inner surface of the lower packer 3, the longitudinal size of which determines a size S of a stroke of the hollow rod 15 (FIG. 3 and FIG. 4).

[0076] The inner cavity of the rod 15, the inner cavity of the lower feedthrough packer 3, the inner cavity of the collar locator 2 and the inner cavity of the mechanical anchor respectively communicate with each other and form a single flushing channel 20 (FIG. 3).

[0077] When the device is set in a transport position, the hollow rod 15 is in a lower position, where the protrusions 17 rest against a lower horizontal wall of the cavity 18. The radial flushing holes 14 provide communication of the recess 12 with the annular inter-packer space (FIG. 2 and FIG. 3).

[0078] The cup seals 8 of the lower feedthrough packer 3 are located at a distance H1 (FIG. 3) from the flushing holes 14 of the hydraulic fracturing port 4; the distance H1 depends on a diameter of the well casing 23 and does not exceed two diameters of the well casing 23.

[0079] The device for implementing the described method works as follows:

[0080] Before lowering into the well casing 23, the device is assembled at the wellhead and installed on the tubing 22.

[0081] When descending, the mechanical anchor 1, the lower 3 and upper 5 feedthrough packers are in the transport position, the hollow rod 15 is in the lower position and is fixed by the limiting protrusions 17 to prevent its axial downward movement.

[0082] Before processing the productive formation, the device is placed in a blank section of the well casing 23 and the feedthrough packers are pressed.

[0083] Next, the device is installed in such a way that the interval to be processed is located in the inter-packer space and the mechanical anchor 1 is activated, ensuring that the device is fixed to the well with anchor elements 21 (FIG. 4). Then part of the tubing 22 weight is unloaded onto the mechanical anchor 1, while the hollow rod 15 enters the recess 12, hermetically closing the flushing holes 14 with the help of seals 18 (FIG. 5).

[0084] Next, hydraulic fracturing fluid is supplied to the tubing 22 under pressure and, due to the counterflow from the hydraulic fracturing port 4, the cup sealing elements 8 and 9 of the feedthrough packers 3 and 5 open and hermetically align to the inner wall of the well casing 23, reliably isolating the inter-packer space. Then, hydraulic fracturing is performed (FIG. 6).

[0085] Upon hydraulic fracturing, the tubing 22, the inventive device and the annulus space between the device and the well casing 23 are flushed to remove proppant and other debris, ensuring a smooth and safe movement of the device to the next interval of the productive formation or during its removal from the well casing 23.

[0086] Flushing of the annular space of the well casing 23 and the cavities of the device is carried out in two cycles as follows.

[0087] During the first cycle, the pumping unit located on the surface feeds the flush fluid under pressure into the annular space, while the cup sealing elements 8 of the lower feedthrough packer 3 are in the active position. The flush fluid enters the inner cavity of the hydraulic fracturing port 4 through the windows 10 and then flows through the upper feedthrough packer 5 and up the tubing 22 to the surface, carrying the proppant and other solids from the upper area of the inter-packer space (FIG. 7). When the flushing technological period ends, the supply of the flush fluid is stopped.

[0088] At the beginning of the second flushing cycle, the device is turned to the transport position. To do this, the mechanical anchor 1 is deactivated by longitudinal movement of the device. The hollow rod 15 moves down until the limiting protrusions 17 rest against the wall of the cavity 19 and opens the flushing holes 14.

[0089] Then, the flush fluid is again fed under pressure into the tubing 22 (FIG. 8). The flush fluid enters the internal cavities of the upper feedthrough packer 5 and the hydraulic fracturing port 4. Then, it exits through the windows 10 into the inter-packer space, activating the upper 5 and lower feedthrough packers 3, thoroughly washing the proppant and other solids out of the lower area of the inter-packer space. Next, the mixture enters the flushing holes 14 and the inner cavity of the rod 15. It then flows through a single flushing channel 20 outside the device into the well casing 23.

[0090] The method is implemented as follows.

[0091] The inventive device assembled at the wellhead is lowered into the well casing 23, which is oppressed by a pressure of 15 MPa. The total length of the wellbore is 3250 m, including the sidetrack of 450 m. The device is lowered at a velocity of no more than 0.25 m/s when moving along the well casing 23 with a diameter of 168 mm, a length of 2800 m, and at a velocity of 0.1 m/s when moving along a sidetrack with a diameter of 114 mm (strength group N80 API 5CT).

[0092] First, the device is placed in a blank area of the sidetrack and the feedthrough cup packers 5 and 3 are put under 12 MPa pressure.

[0093] The sequence of productive formation interval processing is set in such a way that the lowest interval at the level of 3200 - 3215 m is processed first.

[0094] The inventive device is installed in the well casing 23 in such a way that the interval to be processed is located between the cup packers 5 and 3. The inventive device is then fixed to the well casing 23 with anchor elements 21 when the mechanical anchor 1 is activated (FIG. 4).

[0095] Next, the hydraulic fracturing fluid is pumped through the tubing 22 and packers 5 and 3 with cup seals 8 and 9 are activated, ensuring a tight fit to the inner wall of the well casing 23 and reliably isolating the annular gap between the well casing 23 and the inventive device in the inter-packer space. Then hydraulic fracturing is carried out at 46 MPa. (FIG. 6).

[0096] At the end of hydraulic fracturing, the hydraulic fracturing fluid supply is stopped. Meanwhile, debris, including proppant, accumulates in the inter-packer annular gap and in the cup seals, which can lead to the inventive device jamming when moving to the next formation interval to be processed.

[0097] To prevent an emergency, the inter-packer annular gap is flushed to remove debris (mechanical particles, proppant) after hydraulic fracturing.

[0098] The first cycle begins with supplying the flush fluid at 100 atmospheres by a pumping unit located on a ground surface surrounding a top entrance (top mouth) of the well casing 23. Ensuring the flow rate of the flush fluid of 6 1/s, the cup seals 8 of the lower feedthrough packer 3 are activated. The debris is washed out of the upper area of the inter-packer annular gap through the windows 10 of the hydraulic fracturing port 4, being pushed along the tubing to the surface for disposal (FIG. 7).

[0099] After removing debris from the upper area of the inter-packer annulus, the flush fluid supply is stopped.

[0100] During the second washing cycle, the mechanical anchor 1 is deactivated by longitudinal movement of the device, and the device is turned to the transport position. Next, the tubing 22 is axially moved to shift the hollow rod 15 of the device until the limiting protrusions 17 rest against the wall of the cavity 19 opening the flushing holes 14. Then, the flush fluid is supplied at a pressure of 12 MPa and at a flow rate of 1.5 1/s, activating the lower 3 and upper 5 packers.

[0101] Moving through the opened flushing holes 14 through a single flushing channel 20, the flush fluid cleans the lower area of the inter-packer annulus. It washes out small debris from the cup seals 8 of the lower packer 3 and all the internal cavities of the device below the hydraulic fracturing port, while all the debris is pushed down outside the device into the well casing 23. The cleanup period of the second cycle is determined by the presence or absence of resistance to the movement of the device in the well casing 23.

[0102] After it is flushed, the device is lifted to process the second interval of the productive formation at the level of 3035 - 3050 m observing the sequence of actions for hydraulic fracturing and flushing of the annular inter-packer space and the elements of the device.

[0103] After the third interval (2870 - 2885 m) is processed and flushed, the inventive device is removed from the well casing 23.

[0104] Thus, the claimed invention makes it possible to provide high-quality, technological cleanup of the inter-packer annulus space, trouble-free movement of the downhole tool for processing several intervals of the productive formation within one tripping, using a simple and reliable device.