CN212337257U - T-shaped well group for exploiting non-diagenetic natural gas hydrate - Google Patents
T-shaped well group for exploiting non-diagenetic natural gas hydrate Download PDFInfo
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- CN212337257U CN212337257U CN202020830033.XU CN202020830033U CN212337257U CN 212337257 U CN212337257 U CN 212337257U CN 202020830033 U CN202020830033 U CN 202020830033U CN 212337257 U CN212337257 U CN 212337257U
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Abstract
The utility model provides a T type well group for exploiting non-diagenetic type natural gas hydrate, include: the horizontal well is positioned on one side of the vertical well, and the vertical well and the horizontal well share one well mouth; the vertical well target point is positioned in a stable stratum below the reservoir; the deflecting section, the inclination increasing section, the inclination stabilizing section and the horizontal section of the horizontal well are all positioned in a stable stratum above the reservoir, and the target point of the horizontal well is positioned in the stable stratum above the reservoir or in the reservoir; the vertical well and the horizontal well are both provided with a fracturing sand prevention layer, and the fracturing of the vertical well is a horizontal joint; the horizontal well fractures are vertical fractures, the lower ends of the horizontal well fractures extend into the reservoir, and the number of the horizontal well fractures is not less than 2. The utility model has the advantages as follows: the straight well target point, the horizontal well deflecting section, the deflecting increasing section, the deflecting stabilizing section and the horizontal section in the T-shaped well group are all arranged in the stable stratum under or on the reservoir stratum, so that the stability and the well control safety of the shaft of the whole well group can be improved, and the contact area between the shaft and the reservoir stratum can be increased.
Description
Technical Field
The utility model relates to a natural gas hydrate well drilling exploitation technical field especially indicates a T type well group for exploiting non-diagenetic type natural gas hydrate.
Background
The non-diagenetic natural gas hydrate is mainly buried in a shallow layer of the seabed, and a reservoir layer of the non-diagenetic natural gas hydrate is not hard or is not diagenetic and is in a flowing sand shape, so that the borehole wall instability phenomenon for exploiting the non-diagenetic natural gas hydrate is frequent. If a large amount of quicksand is produced and the reservoir is mined out, the overlying strata can collapse unstably and even induce catastrophic accidents such as seabed collapse or tsunami.
The non-diagenetic natural gas hydrate is in a solid state under the conditions of low temperature and high pressure, and the phase state of the non-diagenetic natural gas hydrate is changed from the solid state to the gaseous state along with the change of the ambient temperature and pressure in the process of mining, and simultaneously water is produced. If the phase state transformation is uncontrollable, the volume of the hydrate can expand rapidly, and in addition, the non-diagenetic natural gas hydrate in the ocean is buried shallowly and well cementation is not firm, so that accidents such as instability of a well wall, out-of-control blowout, casualties and the like are easily caused.
In conclusion, in the non-diagenetic natural gas hydrate exploitation process, the safe and stable well wall conditions are beneficial to effectively solving the problems of production control, environmental risks and the like. At present, a large wellhead vertical well is generally adopted at home and abroad to carry out trial production work of non-lithogenic natural gas hydrate in the sea. Because the pilot production mainly obtains stratum data and related data and the methane yield is low, various runaway and safety accidents possibly caused by borehole wall instability do not need to be considered too much. However, when the non-diagenetic natural gas hydrate is industrially exploited, along with the great decomposition of the hydrate, methane, water and reservoir sand are produced at a high speed, and the process is easy to cause disastrous accidents such as reservoir mining, instability, well wall collapse, out-of-control blowout and the like.
SUMMERY OF THE UTILITY MODEL
The utility model provides a T type well group for exploiting non-diagenetic type natural gas hydrate has solved among the prior art poor stability of the wall of a well, pit shaft unstability, the great problem of exploitation process risk.
The technical scheme of the utility model is realized like this:
a T-well assembly for the production of non-diagenetic natural gas hydrates, comprising: the device comprises a vertical well and a first horizontal well positioned on one side of the vertical well, wherein the vertical well and the first horizontal well share a wellhead; the straight well target point of the straight well is positioned in a second stable stratum below the reservoir, and the distance from the straight well target point to the reservoir is greater than or equal to 1/2 of the distance from the well head to the reservoir; the deflecting section, the inclination increasing section, the inclination stabilizing section and the horizontal section of the first horizontal well are all located in a first stable stratum above the reservoir, and the horizontal well target point of the first horizontal well is located in the first stable stratum or the reservoir; the vertical well and the first horizontal well are both provided with fracturing sand prevention layers, the vertical well fracturing of the vertical well is a horizontal joint, and the half length of the vertical well fracturing is not less than 50 m; the first horizontal well fractures of the first horizontal well are vertical fractures, the lower ends of the first horizontal well fractures extend into the reservoir, and the number of the first horizontal well fractures is not less than 2.
Preferably, a second horizontal well is further arranged on the other side of the vertical well, and the second horizontal well and the vertical well share one wellhead; the horizontal well target point, the deflecting section, the deflection increasing section, the deflection stabilizing section and the horizontal section of the second horizontal well are all positioned in a first stable stratum above the reservoir stratum; the second horizontal well is provided with a fracturing sand prevention layer, the second horizontal well fractures of the second horizontal well are vertical fractures, the lower ends of the second horizontal well fractures extend into the reservoir, and the number of the second horizontal well fractures is not less than 2.
Preferably, the length of the horizontal section is not less than 200 meters.
The well construction method of the T-shaped well group comprises the following steps:
firstly, drilling a straight well, wherein a straight well target point is positioned in a second stable stratum below a reservoir stratum, and after casing completion, performing perforation, fracturing sand control operation and closing the well; and (2) drilling a horizontal well again by utilizing a wellhead of the vertical well, wherein the deflecting section, the steady-deviation section and the horizontal section of the horizontal well are all positioned in a first stable stratum which is covered (not necessarily adjacent to the reservoir) of the non-diagenetic natural gas hydrate reservoir, the target point of the horizontal well can be in the first stable stratum which is covered and can also be in the reservoir, and after casing completion, the horizontal well is perforated towards the reservoir direction and closed after fracturing sand control operation.
The horizontal well in the T-shaped well group is a production well and is mainly used for exploiting methane in a reservoir stratum, and meanwhile, the well is beneficial to improving the stability of the well group and enhancing the well control effect; the vertical well may be used as a process or production well, and in addition to enhancing the stability and well control of the well assembly, may also be used to inject desired agents or substances into the reservoir including, but not limited to, CO2, hot water, etc.
The utility model has the advantages that:
the non-diagenetic natural gas hydrate is industrially exploited by the T-shaped well group through sand control and fracturing, the stability of the marine stratum is facilitated, and the long-term efficient development of the hydrate and the safety of the marine environment are ensured.
The straight well target point, the horizontal well deflecting section, the deflecting increasing section, the deflecting stabilizing section and the horizontal section in the T-shaped well group are all arranged in the stable stratum under or on the reservoir stratum, so that the stability and the well control safety of the shaft of the whole well group can be improved, and the contact area between the shaft and the reservoir stratum can be increased.
The fracturing sand prevention layer after the casing completion slows down the sand production speed to a certain extent, and increases the hydrate decomposition, diffusion and seepage speeds.
By setting the length of the horizontal section to not less than 200 m, the stability of the wellbore can be facilitated and the production yield of natural gas can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a T-shaped well group in embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of the T-shaped well group in embodiment 2 of the present invention.
In the figure:
1. the fracturing method comprises the following steps of 1, a vertical well, 2, a first horizontal well, 3, a vertical well target point, 4, a horizontal well target point, 5, a fracturing sand prevention layer, 6, a vertical well fracturing crack, 7, a first horizontal well fracturing crack, 8, a first stable stratum, 9, a second stable stratum, 10, a reservoir layer, 11, a second horizontal well, 12 and a second horizontal well fracturing crack.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Example 1
As shown in fig. 1, the T-well group comprises a vertical well 1 and a first horizontal well 2, both of which share a wellhead, and are completed with casing. The vertical well target point 3 of the vertical well 1 is positioned in a second stable stratum 9 below the reservoir 10, and the distance from the vertical well target point 3 to the reservoir 10 is 260 meters (the distance from the seabed to the reservoir 10 is 500 meters); a horizontal well target point 4, a deflecting section, an inclination increasing section, an inclination stabilizing section and a horizontal section of the first horizontal well 2 are all positioned in a first stable stratum 8 above a reservoir layer 10, and the length of the horizontal section is 400 meters; the vertical well 1 and the first horizontal well 2 are both provided with fracturing sand prevention layers 5, the vertical well fracturing seam 6 of the vertical well 1 is a horizontal seam, and the half length of the vertical well fracturing seam 6 is 80 meters; the first horizontal well fractures 7 of the first horizontal well 2 are vertical fractures, the lower ends of the first horizontal well fractures 7 extend into the bottom of the reservoir 10, and the number of the first horizontal well fractures 7 is 3.
The well construction method of the T-shaped well group comprises the following steps:
firstly, drilling a vertical well 1, performing perforation, fracturing and sand prevention operation after casing completion, and then closing the well; and (2) drilling the first horizontal well 2 by using the wellhead of the vertical well 1, so that the deflecting section, the inclination increasing section, the inclination stabilizing section and the horizontal section of the first horizontal well 2 are all positioned in a first stable stratum 8 which is coated on the non-diagenetic natural gas hydrate reservoir 10 (not necessarily adjacent to the reservoir), the horizontal well target point 4 can be in the stable stratum or in the reservoir, and after casing completion, the well is closed after perforation and fracturing sand control operation in the direction of the reservoir 10.
The method for exploiting the non-diagenetic natural gas hydrate by utilizing the T-shaped well group comprises the following steps:
(1) opening the vertical well 1, and injecting chemical reagents and hot water into the vertical well 1 to decompose the natural gas hydrate in the reservoir 10;
(2) when the natural gas hydrate in the reservoir 10 reaches a certain decomposition speed, the methane gas is separated under the action of gravity, namely the methane gas is positioned above a water layer and a hydrate layer to form a gas cap, and when the gas cap is detected to exist in the reservoir 10, the vertical well 1 is closed;
(3) and opening the first horizontal well 2, injecting chemical reagents according to the requirement, then reducing the pressure, controlling the production speed according to the actual situation, and producing the methane gas in the gas cap of the reservoir 10 so as to ensure that most water and sand are continuously remained in the reservoir 10.
Such chemicals include, but are not limited to, carbon dioxide and hot water.
Example 2
As shown in fig. 2, the T-well group comprises a vertical well 1, a first horizontal well 2 and a second horizontal well 11, all of which share a wellhead, and are completed by casing. The vertical well target point 3 of the vertical well 1 is positioned in a second stable stratum 9 below the reservoir 10, and the distance from the vertical well target point 3 to the reservoir 10 is 480 meters (the distance from the seabed to the reservoir 10 is 800 meters); a horizontal well target point 4, a deflecting section, an inclination increasing section, an inclination stabilizing section and a horizontal section of the first horizontal well 2 are all positioned in a first stable stratum 8 above a reservoir layer 10, and the length of the horizontal section is 1000 meters; a horizontal well target point, a deflecting section, an inclination increasing section, an inclination stabilizing section and a horizontal section of the second horizontal well 11 are all positioned in the first stable stratum 8 above the reservoir 10, and the length of the horizontal section is 800 meters; the vertical well 1 and the first horizontal well 2 are both provided with fracturing sand prevention layers 5, the vertical well fracturing seam 6 of the vertical well 1 is a horizontal seam, and the half length of the vertical well fracturing seam 6 is 100 meters; the first horizontal well fractures 7 of the first horizontal well 2 are vertical fractures, the lower ends of the first horizontal well fractures 7 extend into the bottom of the reservoir 10, and the number of the first horizontal well fractures 7 is 5; the second horizontal well fractures 12 of the second horizontal well 11 are vertical fractures, the lower ends of the second horizontal well fractures 12 extend into the top of the reservoir 10, and the number of the second horizontal well fractures 12 is 3.
The well construction method of the T-shaped well group comprises the following steps:
firstly, drilling a vertical well 1, performing fracturing sand prevention operation after casing completion, perforating and then closing the well; and (2) drilling a first horizontal well 2 and a second horizontal well 11 by utilizing a wellhead of the vertical well 1, so that a deflecting section, an inclination increasing section, an inclination stabilizing section and a horizontal section of the first horizontal well 2 and the second horizontal well 11 are all positioned in a first stable stratum 8 which is coated on the non-diagenetic natural gas hydrate reservoir layer 10 (not necessarily adjacent to the reservoir layer), a horizontal well target point 4 can be in the stable stratum and also can be in the reservoir layer, and after casing completion, the well is perforated towards the direction of the reservoir layer 10 and closed after fracturing sand control operation.
The method for exploiting the non-diagenetic natural gas hydrate by utilizing the T-shaped well group comprises the following steps:
(1) opening the vertical well 1, and injecting chemical reagents and hot water into the vertical well 1 to decompose the natural gas hydrate in the reservoir 10;
(2) when the natural gas hydrate in the reservoir 10 reaches a certain decomposition speed, the methane gas is separated under the action of gravity, namely the methane gas is positioned above a water layer and a hydrate layer to form a gas cap, and when the gas cap is detected to exist in the reservoir 10, the vertical well 1 is closed;
(3) and opening the first horizontal well 2 or the second horizontal well 11 or both simultaneously, injecting chemical reagents according to the requirements, then reducing the pressure, controlling the production speed according to the actual situation, and producing the methane gas in the gas cap of the reservoir 10 so as to ensure that most water and sand are continuously remained in the reservoir 10.
Such chemicals include, but are not limited to, carbon dioxide and hot water.
To sum up, the utility model discloses utilize T type well to adopt the sand control fracturing to aggravate non-diagenetic type natural gas hydrate of power differentiation method industrial exploitation, be favorable to the marine stratum to be stable, guarantee long-term high-efficient development of hydrate and marine environment safety.
The straight well target point, the horizontal well deflecting section, the deflecting increasing section, the deflecting stabilizing section and the horizontal section in the T-shaped well group are all arranged in the stable stratum under or on the reservoir stratum, so that the stability and the well control safety of the shaft of the whole well group can be improved, and the contact area between the shaft and the reservoir stratum can be increased.
The fracturing sand prevention layer after the casing completion slows down the sand production speed to a certain extent, and increases the hydrate decomposition, diffusion and seepage speeds.
When the gas cap exists in the reservoir, only methane in the gas cap is exploited, and most of water and sand are still left in the reservoir, so that on one hand, catastrophic accidents caused by sand production, reservoir mining collapse, uncontrollable natural gas hydrate phase state transition and unstable mineshafts can be effectively avoided, and on the other hand, the single-well yield and the economic benefit of the methane can be effectively improved.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. A T-well string for the production of non-diagenetic natural gas hydrates, comprising: the device comprises a vertical well (1) and a first horizontal well (2) positioned on one side of the vertical well (1), wherein the vertical well (1) and the first horizontal well (2) share one wellhead; the vertical well target point (3) of the vertical well (1) is positioned in a second stable stratum (9) below a reservoir (10), and the distance from the vertical well target point (3) to the reservoir (10) is greater than or equal to 1/2 of the distance from a well head to the reservoir (10); the deflecting section, the inclination increasing section, the inclination stabilizing section and the horizontal section of the first horizontal well (2) are all located in a first stable stratum (8) above the reservoir (10), and a horizontal well target point (4) of the first horizontal well (2) is located in the first stable stratum (8) or the reservoir (10); the vertical well (1) and the first horizontal well (2) are both provided with fracturing sand-prevention layers (5), the vertical well fracturing seam (6) of the vertical well (1) is a horizontal seam, and the half length of the vertical well fracturing seam (6) is not less than 50 m; the first horizontal well fracturing fractures (7) of the first horizontal well (2) are vertical fractures, the lower ends of the first horizontal well fracturing fractures (7) extend into the reservoir (10), and the number of the first horizontal well fracturing fractures (7) is not less than 2.
2. The T-shaped well group for exploiting non-diagenetic natural gas hydrates according to claim 1, characterized in that a second horizontal well (11) is further arranged on the other side of the vertical well (1), and the second horizontal well (11) and the vertical well (1) share a well head; the horizontal well target point, the deflecting section, the inclination increasing section, the inclination stabilizing section and the horizontal section of the second horizontal well (11) are all positioned in the first stable stratum (8) above the reservoir (10); the fracturing sand prevention layer is arranged on the second horizontal well (11), the second horizontal well fracturing fractures (12) of the second horizontal well (11) are vertical fractures, the lower ends of the second horizontal well fracturing fractures (12) extend into the reservoir (10), and the number of the second horizontal well fracturing fractures (12) is not less than 2.
3. A T-well group for the recovery of non-diagenetic natural gas hydrates according to any of the claims 1 to 2, characterized in that the length of the horizontal section is not less than 200 meters.
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Granted publication date: 20210112 Termination date: 20210514 |