RU2833662C1 - Well drilling method - Google Patents

Abstract

FIELD: earth or rock drilling.

SUBSTANCE: invention relates to oil and gas industry, namely to construction of deep wells, and can be used at well deepening for preservation of natural reservoir properties of exposed productive formations. Method of drilling wells consists in lowering into the well on the drill pipe string located below the rock cutting tool and the main packer equipped with the main cross coupling, cross coupling guiding the flow of drilling fluid from the annular space of drill pipes of the well above the main packer into the downhole device installed below the main packer, and outside the downhole device – into the drill pipe string above the main packer, performing back flushing with drilling mud of the well bore above the main packer along the annular space – outside the drill pipes. Prior to lowering, drill pipes are equipped from above below the wellhead with an additional packer with an additional cross coupling, directing the flow of drilling fluid from the drill string above the additional packer in the annular space of the drill string below this packer, and from the drill string below the additional packer – into the annular space of the drill string above the additional packer. Downhole device used is downhole motor for rotation of rock cutting tool.

EFFECT: proposed method of drilling wells allows expanding functional capabilities due to use of downhole motor below packer, which enables to drill deep wells and wells with a complex profile (with inclined and/or horizontal sections) without mudding of the first exposed formations due to back flushing using standard equipment for direct flushing of well equipment.

2 cl, 1 dwg

Description

The invention relates to the oil and gas production industry, namely, to the field of deep well construction and can be used when deepening a well to preserve the natural reservoir properties of the productive strata being opened.

A method is known for creating a depression on a formation during rotary drilling of a well (patent RU No. 2637254, IPC E21B 21/08, E21B 07/00, published 01.12.2017 Bulletin No. 34), including flushing the well with a surface pump through a drill string of pipes, transmitting an axial load and torque to the bit and deepening the well, periodically suspending the deepening of the well, sealing the annular space with a rotating packer installed on a cylindrical body, turning on reverse bottomhole flushing with a pressure drop in the fluid on the packer created by a jet pump installed above the packer at the lower end of the drill string and made in the form of a nozzle, a mixing chamber and a diffuser hydraulically connected to the annular space and resuming deepening with a depression on the formation, and in order to increase the efficiency of the method by reducing formation contamination and ensuring drilling of inclined and horizontal wells with one assembly on depression and on repression without additional lowering and lifting operations of the tool, the transmission of axial load and torque to the bit is carried out directly through a cylindrical body made with the possibility of compaction along the outer surface, which is moved during deepening along its entire length with rotation inside the packer with an acceptable small leakage of liquid between the mating surfaces using a combined seal made in the form of a metal ring installed first along the leakage path and a rubber element installed second along the leakage path of liquid in the area of low pressure and hydraulically connected by its internal cavity to the annular space of high pressure above the packer, wherein the packer is equipped with a mechanical lock, for example, in the form of a spring-loaded ball, and the cylindrical body in the lower part is equipped with a check valve and is made in the form of one drill pipe or several pipes with the diameter of the connections of the latter equal to the diameter of the pipe body with a total length of the cylindrical body not exceeding the length candles used.

The disadvantages of this method are the narrow scope of application due to the impossibility of creating depression on highly productive and/or high formation pressure (over 10 MPa) formations, as well as the complexity of implementation due to the need to strictly adhere to operating modes when implementing the method.

A method for constructing wells for exploration and production of industrially useful fluids - oil, gas, steam and water, accumulated in natural fractured reservoirs is also known (patent RU No. 2732161, IPC E21B 07/00, E21B 21/00, E21B 43/02, published 09/14/2020 Bulletin No. 26), including the initial opening of the reservoir with a well using a composite drill string, cleaning the well from drilled rock with an upward flow of drilling mud, lowering the production string and separating the formations in its annular space and stimulating the inflow of formation fluid, wherein the initial opening of the reservoir is carried out with cleaning the well from drilled rock - cuttings with drilling mud during continuous reverse flushing, sampling of the cuttings is carried out to detect characteristic minerals filling of natural fractures and determination of intervals of opening of clusters of natural fractures based on these data, clusters of natural fractures with open and closed - mineralized fractures intersected by the well are identified based on data on absorption of drilling mud or inflow of formation fluids, clusters of fractures with industrial potential that do not require stimulation during well completion and clusters with low potential that require stimulation of inflow during well completion are identified among clusters with open fractures based on data on the intensity of absorption of drilling mud or inflow of formation fluids during drilling, they require stimulation of inflow during well completion, they lower into the well a production string equipped with devices separating clusters of natural fractures in the annular space of the string, they stimulate the inflow in intervals of clusters of mineralized fractures and clusters of open fractures with low industrial potential, they perforate the production string in intervals of clusters of fractures that do not require stimulation, and they develop the well.

The disadvantage of this method is the narrow scope of application due to the impossibility of using downhole motors during reverse flushing, which makes it impossible to drill deep wells and wells with a complex profile (with inclined and/or horizontal sections).

The closest in technical essence is a device for opening a formation (patent RU No. 2025566, IPC E21B 21/08, published 30.12.1994 Bulletin No. 36), containing two pipes placed concentrically relative to each other, the inner of which has a rock-destroying element, and a well wall colmatation unit, and, in order to increase the efficiency of the device, it is equipped with a cross-flow coupling with vertical and horizontal channels installed on the outer pipe, and packer elements placed on the latter, located under the coupling with the possibility of axial movement along the pipe and between themselves, and the well wall colmatation unit is made in the form of an auger placed on the outer surface of the inner pipe and rigidly connected to it.

This device is used to carry out a method of drilling a wellbore for the primary opening of a formation with a rock-breaking tool during reverse flushing of the formation to a packer placed above the rock-breaking tool and equipped with a cross coupling directing the flow of fluid from the annulus of the well's drill pipes above the packer into a colmatation unit with a swirl installed below the packer, and outside the colmatation unit - into the drill pipe column above the packer.

The disadvantage of this method is the narrow scope of application due to its use only for opening up formations, colmatation of the formation being opened, which requires, after secondary opening up of this formation, highly time-consuming and material-consuming measures (opening up under depression, acid treatment, high compression and/or the like) of the formations, while it is impossible to use downhole motors, which makes it impossible to drill deep wells and wells with a complex profile (with inclined and/or horizontal sections).

The technical result of the proposed invention is the creation of a method for drilling wells, which allows for expanding the functional capabilities by using a downhole motor below the packer, which allows for drilling deep wells and wells with a complex profile (with inclined and/or horizontal sections) without colmatation of the primarily opened formations by reverse flushing using standard downhole equipment for direct flushing.

The technical solution is a method of drilling wells, which includes lowering into the well on a drill pipe string a rock-cutting tool located below and a main packer equipped with a main cross coupling, which directs the flow of drilling fluid from the annulus of the drill pipes of the well above the main packer into a well device installed below the main packer, and outside the well device - into the drill pipe string above the main packer, performing reverse flushing of the wellbore with drilling fluid above the main packer along the annulus - outside the drill pipes.

What is new is that before lowering the drill pipes from above below the wellhead, they are equipped with an additional packer with an additional cross coupling that directs the flow of drilling mud from the drill pipe string above the additional packer to the annulus of the drill pipe string below this packer, and from the drill pipe string below the additional packer to the annulus of the drill pipe string above the additional packer, while a downhole motor is used as a downhole device to rotate the rock-cutting tool.

What is also new is that the downhole motor is equipped with a hollow rod on top, hermetically inserted into the main cross coupling with the possibility of limited longitudinal movement.

The drawing shows a diagram of the implementation of the method in longitudinal section.

The method of drilling wells includes lowering into well 1 on a drill pipe string 2 a rock-cutting tool 3 (a bit, a crown, etc.) located below and a main packer 4 equipped with a main cross coupling 5 directing the flow of drilling fluid from the annulus 6 of drill pipes 2 of well 1 above the main packer 4 along channel 7 (shown conditionally) into a well device made in the form of a downhole motor 8 for rotating the rock-cutting tool 3 and installed below the main packer 4, and outside the downhole motor 8 - into the drill pipe string 2 above the main packer 4. Carrying out reverse flushing with drilling fluid of the wellbore 1 above the main packer 4 along the annulus 6 - outside the drill pipes 1. Before lowering, the drill pipes 1 are equipped from above below the wellhead 1 with an additional packer 9 with an additional cross coupling 10 directing the flow drilling mud from the drill pipe string 2 through the channel 11 (shown conditionally) above the additional packer 9 into the annulus 6 of the drill pipe string 2 below this packer 9, and from the drill pipe string 2 below the additional packer 9 - into the annulus 12 of the drill pipe string 2 above the additional packer 9. In the presence of an inclined (not shown) or horizontal section 13 of the well 1 longer than 150 m, the downhole motor 8 is recommended to be equipped at the top with a hollow rod 14, hermetically inserted into the main cross coupling 5 with the possibility of limited longitudinal movement to ensure sufficient longitudinal load on the rock-cutting tool 3 to affect the bottomhole 15, since the weight of the drill pipe string 2 may not be sufficient to ensure drilling of the bottomhole 15. At a well depth of more than 500 m, the main cross coupling 5 is recommended to be equipped with a check valve 16 to exclude draining the fluid from the drill pipe string 2 during the installation of an additional drill pipe (not shown) to continue drilling, which allows reducing the time for filling it when resuming work. Packers 4 and 9 can be made of any known design, for example, brought into working position by means of the weight of the drill pipe string 2, by turning the drill pipe string 2, etc. - the authors do not claim the design and installation method of packers 4 and 9, since they are widely disclosed in open sources.

Structural elements, process connections, seals, etc. that do not affect the implementation of the method are not shown in the drawing or are shown conditionally.

Example of specific implementation

When drilling a wellbore 1 with a horizontal section 13 (nominal diameter of 216 mm), a drill pipe string 2 (with an outside diameter of 127 mm and a wall thickness of 9.5 mm) is sequentially equipped from below with a rock-cutting tool 3 (a bit with a diameter of 215.9 mm) with a downhole motor and a main packer 4 with a cross coupling 5, a check valve 16 and centralizers 17 (shown conditionally) on both sides, and from above - with an additional packer 9 with an additional cross coupling 10. Moreover, due to the presence of a horizontal section 13, the downhole motor 8 is equipped with a hollow rod 14 hermetically inserted into the main cross coupling 5. The drill pipe string 2 with packers 4 and 9 and cross couplings 5 and 10 on the leading pipe 18 is placed in the well 1 so that the rock-cutting tool 3 rested against the bottomhole 15, and the hollow rod 14 entered the main cross coupling 5. The wellbore 1 is sealed with packers 4 and 9, moving them into the working position. The mouth of the well 1 is sealed around the leading pipe 18, which is connected from above to a hose (not shown) and a pressure pump (not shown). The injection pump pumps through the leading pipe 18 into the drill pipe string 2 a liquid, which through the channel 11 of the additional cross coupling 10, the annulus 6 below the additional packer 9, the channel 7 of the main cross coupling 4 and the hollow rod 14 enters the downhole motor 8. Passing through the downhole motor 8 and exiting through the opening 19, the liquid ensures the rotation of the rock-cutting tool 3. In this case, a pressure difference is created between the channel 7 of the main cross coupling 4 and the space outside the downhole motor 8, providing a longitudinal force on the downhole motor 8 and the rock-cutting tool 3 and, as a consequence, deepening the bottomhole 15 of the well 1 together with the extension of the hollow rod 14 from the main cross coupling 5. The liquid with the rock destroyed by the rock-cutting tool 3 and the sludge from the space outside the downhole motor 8 through the main cross coupling 4, the check valve 16, the drill pipe string 2 and the additional cross coupling 10 enter the annulus 12 of the drill pipe string 2 above the additional packer 9, from where it is withdrawn, for example, through the wellhead branch pipe 20 into the collection tank 21. The liquid is purified from the collection tank 21, the liquid is directed again to the inlet of the injection pump, and the cuttings and rock are utilized. After the hollow rod 14 has fully extended from the main cross coupling 5, the injection of liquid into the drill pipe string 2 is stopped, the wellhead 1 is depressurized, the leading pipe 18 is lowered with the drill pipe string 2 to the inlet of the hollow rod 14 into the main cross coupling 5, which is determined by the decrease in the weight of the drill pipe string 2 on the wellhead weight inductor (WWI - not shown). After which the wellhead 1 is sealed and drilling is continued using the method described above. If the length of the leading pipe 18 is insufficient for lowering it with the upper part of the drill pipe string 2 to the additional packer 9, it is removed from the well 1, the drill pipe string 2 is extended with another drill pipe (not shown), which is attached to the leading pipe 18. After which the drill pipe string 3 on the leading pipe 18 is lowered into the well 1 until the hollow rod 14 enters the main cross coupling 5. The wellhead 1 is sealed around the leading pipe 18, which is connected from above to a hose and a pressure pump, and drilling is continued using the method described above.

Since the volume of the pumped liquid remains constant and depends on the capacity (Q) of the wellhead injection pump, the flow velocity (v) depends on the cross-section (S):

, (1)

where v is the flow velocity, m/s;

Q - capacity of the wellhead injection pump, ^m3 /h;

S – cross-sectional area, ^m2 .

Cross-sectional area of annulus 6 of well 1:

, (2)

where S ₃ is the cross-sectional area of the annulus 6 of well 1, ^m2 ;

D _скв - internal diameter of well 1, m;

d _n - outer diameter of the drill pipe column, m.

Internal cross-sectional area of drill pipe column 2:

, (3)

where S _k is the area of the internal cross-section of the drill pipe column 2, m ² ;

d _in - internal diameter of the drill pipe column, m.

The ratio of the flow velocity inside (v _int ) and outside (v _n ) of the drill pipe column 2, based on formulas (1), (2) and (3):

, (4)

That is, the speed inside the drill pipe string is at least 2.5 times higher than the speed in the annulus 6, ensuring excellent removal of broken rock and cuttings from the bottomhole zone of well 1 without colmatation of the primarily opened formations. The presence of a downhole motor 8, an additional packer 9 with an additional cross coupling 10 allows drilling deep wells and wells with a complex profile (with inclined and/or horizontal sections) using standard equipment for direct flushing of well equipment (lifts, UINs, injection pumps, wellhead sealers of well 1, etc.). All this together allows for significant savings in time and material costs for drilling wells.

The proposed method of drilling wells allows for expansion of functional capabilities by using a downhole motor below the packer, which allows for drilling deep wells and wells with complex profiles (with inclined and/or horizontal sections) without colmatation of the primarily opened formations by reverse flushing using standard downhole equipment for direct flushing.

Claims (2)

1. A method of drilling wells, which includes lowering into the well on a drill pipe string a rock-cutting tool located below and a main packer equipped with a main cross coupling directing the flow of drilling fluid from the annulus of the drill pipes of the well above the main packer into a downhole device installed below the main packer, and outside the downhole device - into the drill pipe string above the main packer, performing reverse flushing of the wellbore with drilling fluid above the main packer along the annulus - outside the drill pipes, characterized in that before lowering, the drill pipes are equipped from above below the wellhead with an additional packer with an additional cross coupling directing the flow of drilling fluid from the drill pipe string above the additional packer into the annulus of the drill pipe string below this packer, and from the drill pipe string below the additional packer - into the annulus of the drill pipe string above the additional packer, wherein a downhole motor is used as a downhole device for rotating the rock-cutting tool. 2. A method for drilling wells according to paragraph 1, characterized in that the downhole motor is equipped at the top with a hollow rod, hermetically inserted into the main cross coupling with the possibility of limited longitudinal movement.