CN114562237A - Deep sea natural gas hydrate stripe zonal mining method - Google Patents

Abstract

The invention discloses a deep-sea natural gas hydrate strip zone mining method, which adopts a combined arrangement of horizontal wells and vertical wells to establish a strip mining area with the main well as the center; Alternate mining, the mining blocks on the same side can also choose simultaneous mining or interval alternate mining according to the production capacity requirements; and this method has a clear design idea, and the construction method is simple and easy to operate, which can effectively improve the mining efficiency of deep-sea natural gas hydrate and ensure the gas production efficiency of a single well. .

Description

A deep-sea natural gas hydrate strip zone mining method

technical field

The invention relates to a deep sea hydrate exploitation method, in particular to a deep sea natural gas hydrate strip zone exploitation method.

Background technique

Natural gas hydrate is an ice-like cage-like crystalline compound formed by natural gas and water at low temperature and high pressure. It is widely distributed in high-latitude polar permafrost formations and deep water formations such as ocean lakes. It has the characteristics of large reserves and high energy density. , considered as a potential energy source. Among them, the energy density of methane (the volume of methane per unit volume of rock under standard conditions) is very large, 10 times that of coal and black shale, and 2.5 times that of natural gas.

Natural gas hydrates are widely distributed in continents, slopes of islands, uplifts of active and passive continental margins, polar continental shelves, and deep-water environments in oceans and some inland lakes. The formation conditions of natural gas hydrate: low temperature, the temperature is generally lower than 10 ℃; high pressure, the pressure is generally higher than 10MPa; sufficient natural gas (hydrocarbons, mainly methane) gas source; favorable hydrate occurrence space.

Since natural gas hydrates are mainly distributed in the weakly cemented undiagenetic pores of the seabed with small permeability coefficients, it can be concluded from the existing trial mining reports that the existing mining methods are too inefficient to achieve commercialization. The production conditions of mining and the improvement of mining efficiency need to change the layout of the existing mining wells. At the same time, it is necessary to reduce the cost of well pattern layout as much as possible; The wellbore layout is optimized to minimize the impact on the overlying strata due to the decomposition of gas hydrate in the pores. Therefore, there is an urgent need for an effective industrial exploitation method that can improve the exploitation efficiency of deep-sea natural gas hydrate and can effectively control the deformation of the seabed formation caused by the exploitation of natural gas hydrate.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a deep-sea natural gas hydrate strip zone mining method, in order to solve the problems of low efficiency of natural gas hydrate mining in sea areas and reduce the deformation of seabed strata caused by natural gas hydrate mining, and improve deep-sea natural gas hydrate mining. efficiency.

For achieving the above object, the present invention provides following scheme:

A deep-sea natural gas hydrate strip zone mining method, comprising the following steps:

S1: Determine the area where the natural gas hydrate is located, and analyze the natural gas hydrate formation permeability coefficient, formation temperature and particle gradation geological parameters in the area;

S2: Determine the drilling position in the area, and set up an offshore exploitation platform; the offshore exploitation platform penetrates the overburden through the main vertical well and extends into the area;

S3: Determine the mining advancement method and the length of the mining block, with the main shaft as the center, and a strip mining area is symmetrically opened in the area;

S4: Complete the mining vertical shaft drilling construction process and install the mining device, sand control device and pipeline in the strip mining area;

S5: Determine the recovery method of the strip mining area, and select the mining method;

S6: When the gas production in the previously mined area in the strip mining area decreases, switch the strip mining area to perform the mining work in the unmined block area.

In step 2, the overburden layer is below the seawater layer; the main vertical well penetrates the overburden layer and is placed at the design horizon.

The design horizon is the upper and lower boundary positions of the natural gas hydrate reservoir.

The strip mining area includes an upper recovery horizontal well, a lower energy supply horizontal well and a production vertical well; the upper recovery horizontal well and the lower energy supply horizontal well are respectively placed on the upper and lower boundaries of the natural gas hydrate reservoir.

The mining method described in step 5 is pressure reduction mining or heat injection mining.

The depressurization exploitation is specifically to depressurize the surrounding of the exploitation vertical well through the lower energy supply horizontal well, and the natural gas generated by decomposition is transported to the offshore exploitation platform through the upper recovery horizontal well and the main vertical well.

The heat injection mining method is specifically to inject high-temperature fluid into the mining vertical well through the lower energy supply horizontal well, so as to fill the well; the natural gas generated by decomposition is transported to the offshore mining through the upper recovery horizontal well and the main vertical well. platform.

The recovery sequence described in step 5 is that the mining areas on both sides of the strip mining area take the main well as the center to advance mining simultaneously, the mining blocks on both sides are simultaneously retreated and mining, the mining blocks on both sides are simultaneously advanced and mining at intervals, The mining blocks on both sides can be mined at the same time and back at intervals, alternately and sequentially advanced on one side, alternately backed off on one side, alternately backed on one side, or alternately backed off on one side.

The forward mining refers to mining in sequence from the vertical mining shaft to the direction away from the main vertical shaft; the backward mining refers to mining in sequence from the vertical mining shaft to the direction close to the main vertical shaft.

The mining length of the strip mining area is not less than 20m.

The present invention has the following technical effects: the present invention adopts the combined arrangement of horizontal wells and vertical wells to arrange strip mining blocks symmetrically around the main vertical well, and the strip mining blocks are powered by horizontal wells, mining vertical wells, The upper recovery horizontal well and the main vertical well are composed of horizontal wells and main vertical wells. According to the production capacity requirements, the mining blocks on both sides can be mined at the same time or alternately on one side. The mining blocks on the same side can also be mined simultaneously or alternately mined at intervals according to the production capacity requirements. Even by force. The deep-sea natural gas hydrate strip zone mining method has clear design ideas and simple and easy-to-operate construction methods, which can effectively improve the deep-sea natural gas hydrate mining efficiency, ensure the gas production efficiency of a single well, and can realize the commercial development of deep-sea natural gas hydrate in my country at an early date. Provide useful technical reference and guidance, and have extensive promotion and application value in this technical field.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

Fig. 1 is the construction schematic diagram of the mining method of the present invention;

Fig. 2 is the schematic diagram of mining blocks on both sides of the present invention while backing and mining at intervals;

Fig. 3 is the schematic diagram of mining blocks on both sides of the present invention simultaneously advancing mining at intervals;

Fig. 4 is the schematic diagram of mining blocks on both sides of the present invention simultaneously retreating and mining in sequence;

Fig. 5 is the schematic diagram of mining blocks on both sides of the present invention advancing in sequence at the same time;

Fig. 6 is a schematic diagram of one-side alternate sequential retreat mining according to the present invention;

Figure 7 is a schematic diagram of one-side alternately advancing mining in sequence according to the present invention;

Fig. 8 is the schematic diagram of the present invention's single side alternate interval advance mining;

Fig. 9 is a schematic diagram of one-side alternately spaced backward mining according to the present invention;

In the figure, 1-offshore exploitation platform; 2-seawater layer; 3-main vertical well; 4-overburden; 5-upper recovery horizontal well; 6-production vertical well; 7-lower energy supply horizontal well; 8-natural gas hydrate storage layer; 9 - lower formation; 10 - mining decomposition area.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

A deep-sea natural gas hydrate strip zone mining method, comprising the following steps:

S1: Determine the area where the natural gas hydrate is located, and analyze the natural gas hydrate formation permeability coefficient, formation temperature and particle gradation geological parameters in the area;

S2: determine the drilling position in the area, and set up the offshore exploitation platform 1; the offshore exploitation platform 1 penetrates the cover layer 4 through the main vertical well 3 and extends into the area;

S3: Determine the mining advancement method and the length of the mining block, and take the main vertical well 3 as the center, and a strip mining area is symmetrically opened in the area;

S4: Complete the mining vertical shaft drilling construction process and install the mining device, sand control device and pipeline in the strip mining area;

S5: Determine the recovery method of the strip mining area, and select the mining method;

S6: When the gas production in the previously mined area in the strip mining area decreases, switch the strip mining area to perform the mining work in the unmined block area.

In step 2, the cover layer 4 is located under the seawater layer 2; the main vertical well 3 penetrates the cover layer 4 and is placed at the design layer.

The design horizon is the upper and lower boundary positions of the natural gas hydrate reservoir 8 .

The strip mining area includes an upper recovery horizontal well 5, a lower energy supply horizontal well 7 and a production vertical well 6; the upper recovery horizontal well 5 and the lower energy supply horizontal well 7 are respectively placed up and down the natural gas hydrate reservoir 8 boundary.

The mining method described in step 5 is pressure reduction mining or heat injection mining.

The depressurization exploitation is specifically to depressurize the surrounding of the exploitation vertical well 6 through the lower energy supply horizontal well 5, and the natural gas generated by decomposition is transported to the offshore exploitation platform through the upper recovery horizontal well 7 and the main vertical well 3. .

The heat injection mining method is specifically to inject high-temperature fluid into the mining vertical well 6 through the lower energy supply horizontal well 5, and perform a boring well; the natural gas generated by decomposition is transported to the upper recovery horizontal well 7 and the main vertical well 3 to the offshore mining platform.

The recovery sequence described in step 5 is that the mining areas on both sides of the strip mining area take the main well as the center to advance mining simultaneously, the mining blocks on both sides are simultaneously retreated and mining, the mining blocks on both sides are simultaneously advanced and mining at intervals, The mining blocks on both sides can be mined at the same time and back at intervals, alternately and sequentially advanced on one side, alternately backed off on one side, alternately backed on one side, or alternately backed off on one side.

The forward mining refers to mining in sequence from the mining vertical well 6 to the direction away from the main vertical well 3 ;

The mining length of the strip mining area is not less than 20m.

In an embodiment of the present invention, the area where the natural gas hydrate is located generally exists in the subsurface of the marine area, and between the seawater layer 2 and the natural gas hydrate reservoir 8 is a covering layer 4 mixed with seawater and particle pores, and the natural gas hydrate is mixed. The bottom of the material reservoir 8 is a deeper lower stratum 9;

Further, the difference between the present invention and the prior art is that the strip mining area in the present invention is actually two mining areas symmetrical about the main vertical well 3; Connect with the upper recovery horizontal well 5 and the lower energy supply horizontal well 7 at the bottom respectively; the functions of the upper recovery horizontal well 5 and the lower energy supply horizontal well 7 are respectively used for recovery and energy supply; only one horizontal well is opened in the prior art Different ways, through functional division, the extraction efficiency is higher, and the gas production efficiency is guaranteed.

Further, sand control devices are also installed at 5 of the upper recovery horizontal wells; to slow down the deformation and settlement of the submarine strata caused by the exploitation of natural gas hydrates, it can effectively improve the stability of the submarine strata during the exploitation of deep-sea natural gas hydrates, and reduce the wellbore outflow caused by the exploitation of water production. Sand accident happened.

In the embodiment of the present invention, the mining boundary areas 10 are respectively selected areas for actual mining.

Further, the present invention first determines the recovery sequence and then selects blocks for mining. The specific mining sequence is described in the following embodiments respectively.

Example 1:

Analyze the formation permeability coefficient, formation temperature and particle gradation geological parameters in the area where the natural gas hydrate is located, determine the height of the seawater layer, the position suitable for building the main vertical well 3, the thickness of the overburden layer 4, and the symmetrical length range of the strip mining area with respect to the main vertical well 3 ; The specific data are that the seawater depth is 800m, the overburden thickness is 200m, the formation permeability coefficient is 1.5×10 ^-4 cm/s, the formation pressure is 12MPa, and the average particle size of the formation particle is 500μm;

Build the offshore production platform 1 and the main shaft 3 according to the above parameters; build the main shaft 3 through the overburden layer 4 to the height where the overburden layer 4 connects with the natural gas hydrate reservoir 8, and extend downward to the natural gas hydrate reservoir 8 ; According to the above parameters, the seawater depth is 800m, the overburden thickness is 200m, the formation permeability coefficient is 1.5×10 ^-4 cm/s, the formation pressure is 12MPa, and the average particle size of the formation is 500μm; the diameter of the main vertical well 3 is 2m, the upper recovery horizontal well 5 and the lower The diameter of the horizontal well for energy supply is 0.5m, and the length of the strip mining area on each side is 20m. With the main vertical shaft 3 as the center, a mining vertical shaft is opened every 5m to delineate each mining strip;

Further, as shown in Figure 2, the strip mining area is mined through the mining vertical well 6; the mining direction is determined as simultaneous interval retreat mining; the combination of vertical wells and horizontal wells is adopted, and the mining area is mined through the mining vertical well 6; its specific mining steps In order to take the main vertical well 3 as the center and to decompose the natural gas hydrate in the recovery area close to the main vertical well 3 side through the mining vertical wells 6 on both sides according to the direction from near the edge of the mining area to the direction close to the main vertical well 3 in a left-right symmetrical order;

When the depressurization mining method is selected, the fluid pressure in the mining vertical well 6 is reduced, and the natural gas generated by decomposition is collected into the main vertical well 3 through the upper recovery horizontal well 5 and transported to the mining platform 1; when the heat injection mining method is selected, the lower energy supply horizontal well 7 is used. High-temperature fluid is injected into the mining vertical well 6 and the well is filled, and the natural gas generated by the decomposition is collected into the main vertical well 3 through the upper recovery horizontal well 5 and transported to the mining platform 1;

Further, due to the backward mining, first use the above-mentioned mining vertical well 6 to mine two mining strips on both sides of the main vertical well 3 that are close to the edge position of the strip mining area, and lower the mining strips away from the main vertical well 3 side by lowering the energy supply horizontal well 7. The internal fluid pressure of the mining vertical well 6 is increased, and the natural gas generated by the decomposition is transported to the offshore mining platform 1 through the upper recovery horizontal well 5 and the main vertical well 3.

Further, when the productivity of the above-mentioned two mining strips near the edge of the mining area is significantly reduced and cannot meet the requirements of commercial mining, the mining operation is carried out from the edge of the strip mining area to the direction of the main shaft 3 at intervals of one mining strip to the next operating mining strip. , such an interval mining can effectively reduce the subsidence of the mining to the seabed strata, and has a good preventive effect on the mining area that is prone to seabed geological disasters.

Embodiment 2:

The only difference between this embodiment and the first embodiment is that, as shown in FIG. 3 , the mining method is a schematic diagram of spaced forward mining. First, the above-mentioned mining vertical shaft 6 is used to mine two mining strips on both sides of the main vertical shaft 3. 7. Reduce the fluid pressure inside the mining vertical well 6 on the side of the mining strip away from the main vertical well 3, and the natural gas generated by decomposition is transported to the offshore mining platform 1 through the upper recovery horizontal well 5 and the main vertical well 3.

Further, when the productivity of the two mining strips on both sides of the main vertical shaft 3 is significantly reduced and cannot meet the commercial production requirements, the next operating mining strip is mined from the main vertical shaft 3 to the edge direction of the strip mining area at an interval of one mining strip. Operation, such interval mining can realize gas production as soon as possible and effectively reduce the subsidence of the mining to the seabed strata, which has a good preventive effect on the mining area that is prone to seabed geological disasters.

The difference between the effect of this embodiment and the first embodiment is that the sequence of producing the strips is reversed, and the structural arrangement is relatively less complicated than that of the first embodiment, and the gas production time period is shortened; and the present embodiment can realize gas production faster than the first embodiment. economic benefits.

Embodiment three:

The only difference between this embodiment and the first embodiment is that, as shown in Fig. 4 , the two sides are simultaneously withdrawn for mining; when the production capacity of the two mining strips close to the edge of the mining area is significantly reduced and cannot meet commercial mining The mining strips are successively mined in the direction of 1, until the vertical shaft 3.

The difference between the effect of this embodiment and the first embodiment is that when the geological conditions of the mining area are good and the seabed stratum is relatively stable, the method of this example is used for mining. Relatively large, the economic benefits are obvious.

Embodiment four:

The only difference between this embodiment and the first embodiment is that, as shown in FIG. 5 , the two sides are simultaneously advanced for mining. When the production capacity of the two mining strips adjacent to both sides of the main shaft 3 is significantly reduced and cannot meet the commercial mining requirements, the two mining strips on both sides of the main shaft 3 are significantly reduced in production capacity. The mining strip is successively mined in the direction of the shaft 3 until the boundary of the strip mining area.

The difference between the effect of this embodiment and the second embodiment is that when the geological conditions of the mining area are good and the seabed stratum is relatively stable, the method of this example is used for mining. , the gas production is relatively large, and the economic benefits are obvious.

Examples five and six:

The only difference between this embodiment and the first embodiment is that, as shown in Figures 6 and 7 , the one-side alternate sequential retreat mining and the one-side alternate sequential advance mining are respectively, and the mining vertical well is only built along one side of the vertical well 3, and several mining vertical wells are opened. Mining shafts that are close to each other; choose back and forward mining respectively.

The difference between the effect of sequential mining on one side and simultaneous mining on both sides is that when the mining area is not suitable for arranging mining strips on both sides at the same time or when the mining conditions are very good, and the mining on one side can meet the commercial mining goals, choose the mining strip on one side. Compared with arranging mining strips on both sides at the same time, the production system is greatly simplified.

Embodiments seven and eight:

The only difference between this embodiment and the first embodiment is that, as shown in Figures 8 and 9 , the single-side alternately spaced forward mining and the single-side alternately spaced backward mining are respectively, and the production vertical well is only built along one side of the vertical well 3, and there are several mutually spaced mining. mining vertical wells; choose backward mining and forward mining respectively.

The difference between the effect of single-side interval mining and single-side sequential mining is that the mining operation is performed on the mining strip at intervals. The difference between the effect of single-side interval mining and two-side interval mining is that when the mining area is not suitable for simultaneous mining strips on both sides, or when mining The conditions are very good, and when one-sided mining can meet the commercial mining goals, the mining strips on one side are selected. Compared with the mining strips on both sides at the same time, the production system is greatly simplified.

In the description of the present invention, it should be understood that the terms "portrait", "horizontal", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal well", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention, rather than indicating Or imply that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention.

The above-mentioned embodiments are only to describe the preferred modes of the present invention, but not to limit the scope of the present invention. Without departing from the design spirit of the present invention, those of ordinary skill in the art can make various modifications to the technical solutions of the present invention. Variations and improvements should fall within the protection scope determined by the claims of the present invention.

Claims (10)

1. a deep-sea natural gas hydrate strip zone mining method, is characterized in that, comprises the following steps: S1: Determine the area where the natural gas hydrate is located, and analyze the natural gas hydrate formation permeability coefficient, formation temperature and particle gradation geological parameters in the area; S2: Determine the drilling position in the area, and set up an offshore exploitation platform; the offshore exploitation platform penetrates the overburden through the main vertical well and extends into the area; S3: Determine the mining advancement method and the length of the mining block, with the main shaft as the center, and a strip mining area is symmetrically opened in the area; S4: Complete the mining vertical shaft drilling construction process and install the mining device, sand control device and pipeline in the strip mining area; S5: Determine the recovery method of the strip mining area, and select the mining method; S6: When the gas production in the previously mined area in the strip mining area decreases, switch the strip mining area to perform the mining work in the unmined block area. 2 . The method for sub-regional exploitation of deep-sea natural gas hydrate strips according to claim 1, characterized in that: in step 2, the overburden layer is below the seawater layer; the main shaft penetrates the overburden layer and is placed in the Describe the design level. 3 . The deep-sea natural gas hydrate strip zone mining method according to claim 2 , wherein the designed horizon is the upper and lower boundary positions of the natural gas hydrate reservoir. 4 . 4. A deep-sea natural gas hydrate strip mining method according to claim 1, characterized in that: the strip mining area comprises an upper recovery horizontal well, a lower energy supply horizontal well and a mining vertical well; the upper recovery horizontal well; The horizontal well and the lower power supply horizontal well are respectively placed on the upper and lower boundaries of the natural gas hydrate reservoir. 5. A deep-sea natural gas hydrate strip zone mining method according to claim 4, characterized in that: the mining method described in step 5 is depressurization mining or heat injection mining. 6. A deep-sea natural gas hydrate strip zone exploitation method according to claim 5, characterized in that: the depressurization exploitation is specifically depressurizing around the exploitation vertical well through the lower energy supply horizontal well, The natural gas produced by the decomposition is transported to the offshore production platform through the upper recovery horizontal well and the main vertical well. 7 . The deep-sea natural gas hydrate strip zone exploitation method according to claim 5 , wherein the heat injection exploitation mode is specifically injecting high temperature fluid into the exploitation vertical well through the lower energy supply horizontal well. 8 . , carry out boring well; the natural gas produced by decomposition is transported to the offshore exploitation platform through the upper recovery horizontal well and the main vertical well. 8 . The method for strip zone mining of deep-sea natural gas hydrate according to claim 4 , wherein the recovery sequence in step 5 is that the strip mining area takes the main well as the center on both sides of the mining area. 9 . Simultaneously advance mining in sequence, mining blocks on both sides simultaneously retreat in sequence, mining blocks on both sides simultaneously advance mining at intervals, mining blocks on both sides simultaneously retreat mining at intervals, one-side alternate sequential advance mining, one-side alternate sequential retreat mining , One-side alternately spaced forward mining or one-side alternately spaced backward mining. 9 . The deep-sea natural gas hydrate strip zone mining method according to claim 8 , wherein the progressive mining is progressive mining from the mining vertical well to the direction away from the main vertical well; the Backward mining is mining in sequence from the production vertical shaft to the direction close to the main vertical shaft. 10 . The deep-sea natural gas hydrate strip mining method according to claim 1 , wherein the mining length of the strip mining area is not less than 20m. 11 .

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