CN111119764A

CN111119764A - Gas invasion preventing device and drilling string comprising same

Info

Publication number: CN111119764A
Application number: CN201811293581.7A
Authority: CN
Inventors: 岳慧
Original assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering
Current assignee: China Petroleum and Chemical Corp; Sinopec Research Institute of Petroleum Engineering
Priority date: 2018-11-01
Filing date: 2018-11-01
Publication date: 2020-05-08
Anticipated expiration: 2038-11-01
Also published as: CN111119764B

Abstract

The invention provides a gas invasion preventing device and a drilling string comprising the same, wherein the gas invasion preventing device comprises an inner cylinder, a first flow passage and a second flow passage arranged on the outer side of the inner cylinder are formed in the inner cavity of the inner cylinder, the second flow passage is selectively communicated with the first flow passage through a first through hole and is communicated with the outside through a second through hole, the second through hole is positioned at the upper end of the first through hole, the gas invasion preventing device can change the flowing direction of gas and liquid, and the purpose of preventing gas invasion and leakage of drilling fluid is achieved by utilizing the gravity differentiation effect.

Description

Gas invasion preventing device and drilling string comprising same

Technical Field

The invention belongs to the technical field of oil and gas drilling and completion, and particularly relates to a gas invasion preventing device and a drilling string comprising the same.

Background

During operation and construction of a natural gas well, such as well drilling, well completion, testing and the like, gas invasion and leakage of drilling fluid are inevitable due to gas-liquid density difference. The natural gas invades into the drilling fluid to move upwards, and the drilling fluid leaks into the stratum downwards, so that well kick and blowout are easily caused, and well control accidents are caused. At the same time, a large amount of drilling fluid leaks into the formation, increasing drilling costs and contaminating the formation. Particularly for a fracture-cavity type high-pressure gas reservoir, the natural gas channeling speed is high, the drilling fluid is seriously leaked, the well control risk is extremely high, and the drilling and completion cost is extremely high.

At present, for gas reservoirs with lower temperature and pressure, the well control safety can be ensured by improving the strength of a well mouth and a sleeve; the shaft can be filled with the drilling fluid through circulating exhaust, and the performance of the drilling fluid is improved to slow down the gas upward-flowing speed and strive for the time of an operation window; and a gas stagnation technology can also be adopted, namely a section of high-viscosity drilling fluid is extruded into the bottom of the well, so that the upward gas channeling speed is slowed down. However, these measures only slow down the gas channeling speed, prolong the operation window time, have limited gas stagnation action time, are easy to lose efficacy particularly at high temperature, and cannot fundamentally solve the problems of gas invasion and leakage of the drilling fluid, particularly for a fracture-cavity carbonate gas reservoir, the gas channeling speed is high, the leakage amount of the drilling fluid is large, and the risk is extremely high.

Disclosure of Invention

In view of some or all of the above problems, the present invention provides a gas invasion preventing apparatus and a drilling string including the same. The gas invasion preventing device can change the flowing direction of gas and liquid, and achieves the purpose of preventing gas invasion and leakage of drilling fluid by utilizing the gravity differentiation effect.

According to an aspect of the present invention, there is provided a gas intrusion prevention device, including:

an inner cylinder, the inner cavity of which forms a first flow passage,

a second flow passage arranged at the outer side of the inner cylinder, the second flow passage is selectively communicated with the first flow passage through a first through hole and is communicated with the outside through a second through hole,

wherein the second through hole is positioned at the upper end of the first through hole.

In one embodiment, a groove is provided on an outer wall of the middle section of the inner cylinder, an outer cylinder abutting against both side walls of the groove is provided in the groove, an annular space between the outer cylinder and the inner cylinder forms a second flow passage, the first through hole is provided on a wall of the inner cylinder, and the second through hole is provided on a wall of the outer cylinder.

In one embodiment, a sliding sleeve for plugging the first through hole is arranged on the inner wall of the inner barrel, and the sliding sleeve and the inner barrel are fixed through a shearing pin.

In one embodiment, the second flow passage comprises a first section, a second section and a third section in sequence in the top-to-bottom direction, wherein the flow area of the first section and the third section is larger than that of the second section.

In one embodiment, the ratio of the flow area of the second section to the flow area of the first section is between 0.1 and 0.6.

In one embodiment, axially extending webs are provided between the inner and outer barrels.

In one embodiment, the rib plate is abutted against both the inner cylinder and the outer cylinder, and the rib plate is provided with a communication hole.

In one embodiment, the inner cylinder comprises an upper joint section and a lower joint section fixedly connected with the upper joint section, and the connecting contact surface of the upper joint section and the lower joint section is an inclined surface.

In one embodiment, the height of the second flow path is 10-30 meters.

According to another aspect of the present invention there is provided a drilling string comprising the gas intrusion prevention device described above.

Compared with the prior art, the invention has the advantages that: the gas-invaded prevention device is disposed on a drill pipe and is lowered into the wellbore as part of a drill string. When the gas layer is not drilled, the second flow passage is not communicated with the first flow passage, so that the normal circulation function can be realized. When drilling the air layer, the second flow channel is communicated with the first flow channel, the direction of the flow channel is changed from straight up to straight down to be turned back through the second flow channel. After the drilling fluid is poured into the first flow channel, the drilling fluid returns back from the first flow channel through the first through hole and enters the second flow channel. When gas exists outside the gas invasion preventing device, the gas enters the gas invasion preventing device in advance, the drilling fluid needs to be pushed downwards from the second flow passage to go downwards, and liquid needs to enter the outside of the gas invasion preventing device and needs to go upwards in the second flow passage. Since the gas density is less than the density of the drilling fluid, always gas up and liquid down, no relative movement of gas down and liquid up is possible. Therefore, when the pressure is balanced, the gas-liquid interface can keep a balanced state, and the gas invasion and the gas leakage of the drilling fluid can not occur.

Drawings

The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the accompanying drawings. Wherein:

FIG. 1 schematically illustrates a gas intrusion prevention device according to one embodiment of the present invention;

FIG. 2 is section A-A from FIG. 1;

in the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.

Detailed Description

The invention will be further explained with reference to the drawings.

Fig. 1 shows a gas intrusion prevention device 100 according to the present invention. As shown in fig. 1, the gas intrusion prevention device 100 includes an inner cylinder 1 and an outer cylinder 2. Wherein, the inner cavity of the inner cylinder 1 forms a first flow channel 3. The outer cylinder 2 is sleeved on the outer wall of the inner cylinder 1 and forms a second flow passage 4 extending axially with the inner cylinder 1. Wherein a first through hole 11 is provided on the wall of the inner tube 1 so that the second flow path 4 can selectively communicate with the first flow path 3 through the first through hole 11. A second through hole 21 is provided on the wall of the outer cylinder 2 so that the second flow passage 4 communicates with the outside through the second through hole 21. And the second through-hole 21 is located at the upper end of the first through-hole 11.

The gas intrusion prevention device 100 according to the present invention is provided on a drill pipe and is lowered into a wellbore as part of a drill string. When the gas layer is not drilled, the second flow passage 4 is not communicated with the first flow passage 3, and the normal circulation function can be realized. When drilling the air layer, the second flow passage 4 is communicated with the first flow passage 3, and the direction of the flow passage is changed from straight up to straight down to be turned back through the second flow passage 4. After the drilling fluid is poured into the first flow channel 3, the drilling fluid is turned back from the first flow channel 3 into the second flow channel 4 through the first through hole 11. When gas is present outside the gas intrusion prevention device 100, the gas is pre-introduced into the gas intrusion prevention device 100 and needs to push the drilling fluid downward from the second flow passage 4, while the fluid needs to be upward in the second flow passage 4 to enter the outside of the gas intrusion prevention device 100. Since the gas density is less than the density of the drilling fluid, always gas up and liquid down, no relative movement of gas down and liquid up is possible. Therefore, when the pressure is balanced, the gas-liquid interface can keep a balanced state, and the gas invasion and the gas leakage of the drilling fluid can not occur.

In the use process, if the specific gravity of the drilling fluid is too high, the pressure of a drilling fluid column is higher than the gas pressure, the drilling fluid can leak into the stratum from the second through hole 21, the height of the fluid column in the first flow channel 3 can be reduced along with the drilling fluid column, when the pressure of the fluid column is equal to the gas pressure, gas and liquid are automatically balanced, and the gas invasion problem cannot occur in the process. If the specific gravity of the drilling fluid is low, the pressure of a drilling fluid column is lower than the gas pressure, the well can be closed in time, the pressure of a well head can be increased along with the pressure of the well head, and the pressure of the well head plus the pressure of the fluid column can be automatically balanced with the gas pressure. If the well is not closed timely, part of gas enters the second flow passage 4 downwards, but drilling fluid does not leak into the stratum from bottom to top at the position, so that the pressure of the drilling fluid can balance most of the gas pressure, the pressure of the wellhead is not too high, and the gas entering the second flow passage 4 can be removed through circulating exhaust. When gas and liquid are balanced, drilling fluid should be supplemented at any time when the upper part is used for lifting the tubular column, and when the tubular column is used for lowering the tubular column, part of the drilling fluid can be released to maintain the gas and liquid balance, if the drilling fluid is not supplemented in time, part of gas enters the gas invasion preventing device 100, but the entering gas can be removed through circulating exhaust because the drilling fluid is not leaked. And the well can be safely shut down at any time, and the well control safety can be ensured because the drilling fluid is always used for balancing the formation pressure. If too much drilling fluid is replenished or if it is inconvenient to place drilling fluid when running a pipe string, the drilling fluid will leak into the formation, but the total amount is limited. In a word, the second flow passage 4 and the first flow passage 3 which are turned back can ensure that the leakage and the gas invasion of the drilling fluid can not occur simultaneously, thereby ensuring the safety of well control.

A groove 12 is provided on the outer wall of the middle section of the inner cylinder 1. The outer cylinder 2 is disposed in the groove 12, and both end surfaces of the outer cylinder 2 abut against both side walls of the groove 12 to form the second flow path 4 between the outer cylinder 2 and the inner cylinder 1. For convenient installation, the inner cylinder 1 is of a split structure and comprises an upper joint section 13 and a lower joint section 14, and the upper joint section 13 is fixedly connected with the lower joint section 14. The upper coupling section 13 is used for connecting drill rods, while the lower coupling section 14 is also used for connecting drill rods. The upper coupling segment 13 is provided with a first step surface 15, while the lower coupling segment 14 is provided with a second step surface 16, a groove 12 being formed between the two step surfaces 15, 16. The structure is simple and convenient to assemble.

Preferably, the upper joint section 13 and the lower joint section 14 are in a socket joint type connection, and the assembly contact surface is a bevel surface. This connection is relatively stable and avoids stress concentrations. For example. The upper and

lower coupling sections

13, 14 may be threaded with anti-rotation pins (not shown) disposed therebetween. When the gas intrusion prevention device 100 is installed on a drill string, the upper joint section 13 and the lower joint section 14 are arranged to transmit torque well, thereby ensuring normal drilling.

To achieve selective communication of the second flow passage 4 with the first flow passage 3. The inner wall of the inner cylinder 1 is provided with a sliding sleeve 5. The sliding sleeve 5 is arranged on the inner cylinder 1 by means of a shear pin 6. A ball seat (not shown) or a rubber plug seat (not shown) may be provided on the inner wall of the sliding sleeve 5. When the air layer is not drilled, the first through hole 11 is plugged by the sliding sleeve 5, and normal circulation is realized. When the drill meets the air layer, a ball is thrown from the wellhead to be matched with the ball seat or a rubber plug is thrown to be matched with the rubber plug seat, then the ground is pressed, the shearing pin 6 is sheared, and the second flow passage 4 is communicated with the first flow passage 3. The arrangement mode is simple and easy to realize.

The second flow path 4 includes, in order from the top to the bottom, a first section 41, a second section 42, and a third section 43. Wherein the flow area of the first section 41 and the third section 43 are both larger than the flow area of the second section 42. Preferably, the ratio of the flow area of the second section 42 to the flow area of the first section 41 is between 0.1 and 0.6. For example, 0.3. Similarly, the ratio of the flow area of the second section 42 to the flow area of the third section 43 may also be 0.1-0.6, e.g., 0.3. The change in flow area can be achieved by the depth of the groove 12. That is, the groove 12 is deeper at a position corresponding to the first section 41 of the second through hole 21. The groove 12 is also deeper at a position corresponding to the third section 43 of the first through hole 11. And between which, at a second section 42, the groove 12 is shallower. In addition, the second section 42 is connected with the first section 41 and the third section 43 by adopting a bevel type smooth transition. The gas intrusion prevention effect can be increased by this arrangement.

As shown in fig. 2, a rib 7 extending in the axial direction is provided between the inner cylinder 1 and the outer cylinder 2. The rib plate 7 is fixedly arranged on the outer wall of the inner cylinder 1 and is connected with the outer cylinder 2 through threads. The rib 7 serves to increase the strength. Meanwhile, the rib plate 7 connects the inner cylinder 1 and the outer cylinder 2 together, so that the strength is further increased, and particularly after the gas invasion preventing device 100 is arranged on a drill rod, the arrangement can ensure the good transmission of torque, so that the normal drilling is ensured. Communication holes 71 are provided in the rib 7 for constructing spaces on both sides of the rib 7. A plurality of communication holes 71 are provided at intervals in each rib 7 in the axial direction. The communication hole 71 functions to increase the flow area.

In one embodiment the height of the second flow path is 10-30 meters, for example 20 meters. The gas invasion preventing effect is remarkable due to the arrangement, the structure is optimized, the assembly is easy, and the strength stability is high.

In the circumferential direction, a plurality of second through holes 21 are provided at intervals. And each of the second through holes 21 is configured as a long hole distributed along the axial direction. Similarly, in the circumferential direction, a plurality of first through holes 11 are provided at intervals, and each first through hole 11 is configured as an elongated hole distributed along the axial direction. The arrangement is simple and easy to process. At the same time, this arrangement can ensure the strength of the gas intrusion prevention device 100 itself, contributing to better torque transmission.

In the present application, the orientation terms "upper" and "lower" are used with reference to the actual operating orientation of the gasinvasion prevention device 100.

While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A gas intrusion prevention device, comprising:

an inner cylinder, the inner cavity of which forms a first flow passage,

wherein the second through hole is located at an upper end of the first through hole.

2. The gasinvasion preventing device according to claim 1 wherein a groove is provided on an outer wall of a middle section of said inner tube, an outer tube is provided in said groove in abutment with both side walls of said groove, an annulus between said outer tube and said inner tube forms said second flow passage, said first through hole is provided on a wall of said inner tube, and said second through hole is provided on a wall of said outer tube.

3. The gas intrusion prevention device according to claim 1 or 2, wherein a sliding sleeve for plugging the first through hole is provided on an inner wall of the inner cylinder, and the sliding sleeve and the inner cylinder are fixed by a shear pin.

4. A gas migration prevention device according to any of claims 1 to 3, wherein said second flow path comprises, in order in the top-to-bottom direction, a first section, a second section and a third section, wherein the flow area of each of said first section and said third section is larger than the flow area of said second section.

5. The gasproof apparatus of claim 4, wherein a ratio of a flow area of the second section to a flow area of the first section is 0.1-0.6.

6. A gas migration prevention apparatus according to claim 2 wherein axially extending webs are provided between the inner and outer barrels.

7. The gas intrusion prevention device according to claim 6, wherein the rib plate is abutted against both the inner cylinder and the outer cylinder, and communication holes are formed in the rib plate.

8. The gas intrusion prevention device of any one of claims 1 to 6, wherein the inner barrel includes an upper joint section and a lower joint section fixedly connected to the upper joint section, and a connection contact surface of the upper joint section and the lower joint section is a slope.

9. The gasinvasion preventing device of any one of claims 1 to 8, wherein the height of said second flow path is 10-30 meters.

10. A drilling string comprising a gas intrusion prevention device according to any one of claims 1 to 9.