CN108590595A - A method of it is exploited using F type well groups non-at lithotype gas hydrates - Google Patents

Abstract

The non-method at lithotype gas hydrates is exploited using F type well groups, the step of this method is as follows the present invention relates to a kind of：Step 1：A bite inclined shaft is bored, the A target spots for being drilled into gas hydrates reservoir and underliing in good ground are tilted by the upper surface of unstable stratum, then setting of casing, cementing completion；Step 2：A bite horizontal well is bored, horizontal well has vertical well section, angle buildup interval, upwarps well section and net horizontal section, and vertical well section is located at inclined shaft shaft bottom inclined direction side；Step 3：Fracturing sand control construction is carried out to net horizontal section, it is desirable that pressure-break extends into reservoir, injects chemical sand control agent to crack and reservoir；Step 4：Inclined shaft is closed using well head, horizontal well is opened, using CO₂Displacement or heat injection or decompression or mixing method exploitation of gas hydrate.Invention enhances the stability of pit shaft, smoothness, improve the contact area of pit shaft and reservoir, the transformation of gas hydrates phase is set to be happened inside stable pit shaft, on the one hand can effectively avoid shake out, gas hydrates phase change uncontrollable and pit shaft it is unstable caused by the complicated even disaster of accident, on the other hand can effectively improve gas hydrates well yield and economic benefit.

Description

A method of exploiting non-diagenetic natural gas hydrate by using F-type well group

technical field

The invention relates to a method for exploiting natural gas hydrate by utilizing F-type well groups, belonging to the technical field of drilling and exploitation of natural gas hydrates, in particular to a comprehensive utilization of F-type well groups, which adopts depressurization method, heating method and _CO2 replacement Methods of mining natural gas hydrates using natural gas hydrates or hybrid methods.

Background technique

Non-diagenetic gas hydrates are mostly buried in undiagenetic strata on the seabed, with shallow buried depths, unstable reservoirs, and unstable overlying strata. Natural gas hydrate is solid under low temperature and high pressure conditions. During the drilling and production of natural gas hydrate, its phase state changes due to changes in system temperature and pressure. If the phase transition is uncontrollable, the volume of natural gas hydrate will expand rapidly, coupled with the instability of formation and wellbore, it is easy to cause formation collapse, and even induce geological disasters such as submarine landslides and catastrophic accidents such as tsunamis. Therefore, the catastrophic risk of non-diagenetic gas hydrate exploitation is a major obstacle to commercial/trial production. In addition, low production efficiency is also an important factor affecting the economical production of gas hydrates. Artificially creating stable wellbore conditions, promoting rapid and controllable decomposition of hydrates, and ensuring safe and efficient drilling are the main ideas for developing natural gas hydrates.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a method for exploiting natural gas hydrates by using F-type well groups, which can not only ensure the stability of the wellbore of the entire well group, but also drill longer horizontal well sections, increase the number of wellbore and storage The contact area of different layers ensures the long-term and efficient production of natural gas hydrate.

In order to achieve the above object, the present invention provides a method for utilizing F-type well group to exploit natural gas hydrate, the steps of the method are as follows:

Step 1: Drill a deviated well from above the unstable formation to target point A in the underlying stable formation of the natural gas hydrate reservoir, then run the casing and inject cement to complete the well;

Step 2: Drill a horizontal well. The horizontal well has a vertical well section, a deviated well section, an upturned well section and a horizontal well section. The vertical well section is located on the side of the inclined direction of the bottom of the inclined well. The target point B drilled vertically from above the unstable formation to the stable formation below the gas hydrate reservoir is the vertical well section, and the deflection drilling from the target point B to the target point C in the stable formation is the deflection well section. Drilling from target point C until it connects with the deviated well and then continuing to drill to target point D in the stable formation is the upturned well section, drilling horizontally from target point D to target point E in the stable formation is the horizontal well section, and then Casing and cement injection completion;

Step 3: Carry out fracturing and sand control construction on the horizontal well section, requiring the fracturing fracture to extend into the reservoir, and inject chemical sand control agent into the fracture and the reservoir;

Step 4: Use the wellhead to close the deviated well, open the horizontal well, and use _CO2 replacement or heat injection or depressurization or mixed methods to exploit natural gas hydrate.

Among the above, the inclination angle at the bottom of the inclined well is between 5° and 25°; the distance between the target point of the inclined well A and the reservoir is 20m to 150m.

In the above, the connection between the upturned well section and the inclined well at 10m~130m above the A target point.

Among the above, the linear distance between the horizontal well section and the natural gas hydrate reservoir is between 5m and 130m.

In the present invention, the inclined well is mainly used to store water, sand, drainage, sand flushing, and inject CO ₂ , hot water, etc., so as to ensure long-term and efficient production of natural gas hydrate.

In the present invention, the horizontal well is mainly used to ensure the stability of the well body of the entire well group, and at the same time, the well is used to increase the contact area between the wellbore and the reservoir.

In the present invention, according to the actual mining situation, when too much formation water or sand is collected at the bottom of the inclined well, drainage or sand washing operations are performed in the inclined well. After the operation, the gas hydrate production will continue.

In the present invention, ordinary fracturing or segmented fracturing is carried out on the horizontal section of the horizontal well, requiring the fracturing fractures to extend into the reservoir, and then inject chemical sand control agents into the fractures and the reservoir after the fracturing fluid is flowed back, so that the sand control agent in the reservoir Form an artificial well wall around the wellbore to prevent sand production and keep the well wall stable.

In the present invention, when the natural gas hydrate is exploited, the inclined well is closed, and the natural gas is exploited by using the horizontal well. Inject CO ₂ and heat into inclined wells, and shut down horizontal wells.

The beneficial effects of the present invention are:

It consists of a deviated well and a horizontal well. The target point, connection point of the deviated well, the deflection section and the upturned section of the horizontal well are all located in the underlying stable formation of the non-diagenetic gas hydrate reservoir, so that the entire The stability of the wellbore of the well group can drill a longer horizontal well section, increase the contact area between the wellbore and the reservoir, and ensure the long-term and efficient production of natural gas hydrate.

Both horizontal wells and deviated wells are in a stable state, which can effectively deal with the wellbore instability caused by natural gas hydrate, and prevent and control complex accidents and disasters.

After horizontal well fracturing and sand control, the contact area between the wellbore and the reservoir is greatly increased and sand production is prevented. Combined with heat injection and decompression, it can effectively improve the production efficiency of natural gas hydrate.

The inclined wells and horizontal wells perform their respective functions. The horizontal wells are used for gas production, and the inclined wells are used for heat injection, drainage and sand washing, which simplifies the construction procedures and is conducive to the long-term and efficient production of natural gas hydrates.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

FIG. 2 is an enlarged view of part L of FIG. 1 .

Detailed ways

The present invention will be clearly described below in conjunction with the embodiments and the accompanying drawings.

Embodiment one

As shown in Fig. 1 and Fig. 2, in this embodiment, non-diagenetic natural gas hydrate is exploited by fracturing in 5 stages of F-type well group + chemical artificial well wall + depressurization method. The F-type well group includes horizontal wells 10 and deviated wells 9, and the entire well group is completed with casing.

Drill a deviated well 9 firstly, and drill obliquely from above the unstable stratum 6 to the target point A in the stable stratum 8 below the natural gas hydrate reservoir 7, then run the casing and inject cement to complete the well; among them, the deviated well 9 well The well inclination angle at the bottom is 10°, and the straight-line distance between the target point A of the deviated well 9 and the gas hydrate reservoir 7 is 50m;

Another horizontal well 10 is drilled, and the horizontal well 10 has a vertical well section 1, a deviated well section 2, an upturned well section 3 and a horizontal well section 4, and the vertical well section 1 is located on one side of the inclined direction of the bottom of the inclined well 1, When drilling a horizontal well 10, vertically drill from the top of the unstable formation 6 to the B target point in the stable formation 8 below the natural gas hydrate reservoir 7 is the vertical well section 1, and drill from the B target point to the stable formation The target point C in 8 is the deflected well section 2, from which point C is drilled up until it connects with the deviated well 9, and then continues to drill to the stable formation. The target point D in 8 is the upturned well section 3. Horizontal drilling until the E target point in the stable formation 8 is the horizontal well section 4, and then the casing is run and cemented to complete the well; among them, the connection between the upturned well section 2 and the deviated well 9 at 130m above the A target point, the horizontal well section The linear distance between section 5 and gas hydrate reservoir 7 is 5m;

Carry out fracturing and sand control construction on the horizontal well section, perforate the horizontal well section and press out 5 fractures, requiring the fracturing fracture to extend into the reservoir, and then inject chemical sand control agent into the fracture and the reservoir to form artificial well wall and sand control layer 5, in order to prevent sand and keep the wellbore stable;

The inclined well 9 is closed by the well head, the horizontal well 10 is opened, and the natural gas hydrate is exploited by the depressurization method.

After a period of production, the deviated well 9 will collect a large amount of formation water and reservoir sand. When formation water and reservoir sand affect the natural gas production, close the horizontal well 10, open the inclined well 9, and adopt foam drainage measures or sand washing operations in the inclined well 9. After draining or sand washing operations, the horizontal well 10 is opened, the inclined well 9 is closed, and the gas recovery operation is continued. Embodiment two

As shown in Fig. 1 and Fig. 2, in this embodiment, non-diagenetic natural gas hydrate is exploited by fracturing and sand control in the 11th stage of the F-type well group + depressurization + _CO2 replacement. The F-type well group includes horizontal wells 10 and deviated wells 9, and the entire well group is completed with casing.

Drill a deviated well 9 firstly, and drill obliquely from above the unstable stratum 6 to the target point A in the stable stratum 8 below the natural gas hydrate reservoir 7, then run the casing and inject cement to complete the well; among them, the deviated well 9 well The well inclination angle at the bottom is 15°, and the straight-line distance between target point A of the deviated well 9 and the gas hydrate reservoir 7 is 80m;

Another horizontal well 10 is drilled, and the horizontal well 10 has a vertical well section 1, a deviated well section 2, an upturned well section 3 and a horizontal well section 4, and the vertical well section 1 is located on one side of the inclined direction of the bottom of the inclined well 1, When drilling a horizontal well 10, vertically drill from the top of the unstable formation 6 to the B target point in the stable formation 8 below the natural gas hydrate reservoir 7 is the vertical well section 1, and drill from the B target point to the stable formation The target point C in 8 is the deflected well section 2, from which point C is drilled up until it connects with the deviated well 9, and then continues to drill to the stable formation. The target point D in 8 is the upturned well section 3. Horizontal drilling until the E target point in the stable formation 8 is the horizontal well section 4, and then the casing is run and cemented to complete the well; among them, the connection between the upturned well section 2 and the deviated well 9 at 20m above the A target point, the horizontal well section The linear distance between section 5 and gas hydrate reservoir 7 is 10m;

Carry out fracturing and sand control construction on the horizontal well section, perforate the horizontal well section and press out 11 fractures, requiring the fracturing fractures to extend into the reservoir, and then inject chemical sand control agents into the fractures and the reservoir to form artificial well walls and sand control layers 5, in order to prevent sand and keep the wellbore stable;

The inclined well 9 is closed by the well head, the horizontal well 10 is opened, and the natural gas hydrate is exploited by the depressurization method.

After a period of production, the reservoir becomes short, and the decomposition rate of gas hydrate slows down. At this time, the horizontal well 10 is closed, the inclined well 9 is opened, and CO ₂ is injected into the inclined well. After a period of time, close the inclined well 9 again, open the horizontal well 10, and continue to utilize the depressurization method to exploit natural gas. So cycle. Afterwards, the deviated well 9 will collect a large amount of formation water and reservoir sand. When formation water and reservoir sand affect the natural gas production, close the horizontal well 10, open the inclined well 9, and adopt foam drainage measures or sand washing operations in the inclined well 9. After draining or sand washing operations, the horizontal well 10 is opened, the inclined well 9 is closed, and the gas recovery operation is continued.

Claims (4)

1. a kind of exploiting the non-method at lithotype gas hydrates using F type well groups, which is characterized in that the step of this method such as Under：

Step 1：A bite inclined shaft is bored, is tilted by the upper surface of unstable stratum and is drilled into gas hydrates reservoir and underlies in good ground A target spots, then setting of casing, cementing completion；

Step 2：A bite horizontal well is bored, horizontal well has vertical well section, angle buildup interval, upwarps well section and net horizontal section, Vertical Well Section is located at inclined shaft shaft bottom inclined direction side, and when horizontal well drilling, vertically gas hydrates are drilled by the upper surface of unstable stratum The reservoir B target spots in good ground that underlie are vertical well section, and it is deflecting to be drilled into the C target spots in good ground by B target spot deflectings Well section, upwarped by C target spots be drilled into be connected to inclined shaft after to be further continued for being drilled into D target spots in good ground be to upwarp well section, by D target spots It is net horizontal section that level, which is drilled into the E target spots in good ground, then setting of casing, cementing completion；

Step 3：Fracturing sand control construction is carried out to net horizontal section, it is desirable that pressure-break extends into reservoir, is injected to crack and reservoir Chemical sand control agent；

Step 4：Inclined shaft is closed using well head, horizontal well is opened, using CO₂Displacement or heat injection or decompression or mixing method exploitation are natural Gas hydrate.

2. a kind of as described in claim 1 exploit the non-method at lithotype gas hydrates using F type well groups, feature exists In the hole angle in inclined shaft shaft bottom is between 5 °~25 °；Inclined shaft A target spots are away from reservoir air line distance 20m~150m.

3. a kind of as described in claim 1 exploit the non-method at lithotype gas hydrates using F type well groups, feature exists In upwarping well section and connection of the inclined shaft at the above 10m ~ 130m of A target spots.

4. a kind of as claimed in claim 2 exploit the non-method at lithotype gas hydrates using F type well groups, feature exists In net horizontal section and gas hydrates reservoir air line distance are between 5m~130m.