Horizontal well capable of increasing yield of coal bed gas and preventing outburst of gas

Abstract

The utility model provides a horizontal well capable of increasing yield of coal bed gas and preventing outburst of gas. The deflecting section is arranged on one side of the vertical section, and a horizontal main borehole is formed in one side of the deflecting section; the multiple branch well holes are formed in the two sides of the outer surface of the horizontal main well hole, spiral slotted screen pipes are arranged in the branch well holes, and drillable bridge plugs are arranged in the branch well holes and the horizontal main well hole; the multiple sets of hydraulic jetting tools are arranged on the surfaces of the branch well holes correspondingly. According to the coal bed gas yield increasing and gas outburst preventing horizontal well, the exposed area of a reservoir is enlarged through a pinniform branch structure, the coal bed gas exploitation efficiency and safety are remarkably improved by combining staged fracturing and the negative pressure extraction technology, directional perforation is carried out on all fracturing sections through a hydraulic jet tool, a net-shaped crack system is formed, and the coal bed gas yield increasing and gas outburst preventing horizontal well is formed. The spiral slotted screen pipe improves the deformation resistance of the well body, and the service life of a well hole is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to coal bed gas exploitation technology technical field especially relates to a coal bed gas yield increasing and gas outburst prevention horizontal well. BACKGROUND

[0002] China has 30-50 billion cubic meters of coal bed gas (gas) reserves, but most of them are stored in low-permeability reservoirs. At present, the exploitation of coal bed gas is mainly to make the coal bed gas seep out from the wall of the horizontal well, which is inefficient and not conducive to improving the production efficiency of coal bed gas. In the case of unfavorable geological conditions, in order to ensure safe well completion, a protective layer needs to be set on the well wall. Although the protective layer increases safety, it affects the seepage and production of coal bed gas, affecting the coal bed gas production, and the safety and gas production are contradictory, resulting in the dilemma that most of the drilled wells cannot balance safety and well completion and coal bed gas cannot be efficiently and fully developed, causing resource waste.

[0003] In the existing coal bed gas exploitation technology, the straight well has low exploitation efficiency and small single well control area. Although the traditional horizontal well can increase the exposed area of the reservoir, it has the following problems: the single main borehole extension is easily affected by geological structure, leading to well wall instability; the coal bed gas desorption rate is low, the gas extraction is insufficient, and there is a risk of outburst; the fracturing modification range is limited, and it is difficult to form an effective seepage channel network.

[0004] Therefore, it is necessary to provide a coal bed gas yield increasing and gas outburst prevention horizontal well to solve the above technical problems. SUMMARY

[0005] The utility model provides a coal bed gas yield increasing and gas outburst prevention horizontal well, solved single main borehole extension easily affected by geological structure, leading to well wall instability, coal bed gas desorption rate is low, gas extraction is insufficient, and there is a risk of outburst, fracturing modification range is limited, and it is difficult to form an effective seepage channel network problem.

[0006] To solve the above technical problems, the utility model provides a coal bed gas yield increasing and gas outburst prevention horizontal well, which comprises: a vertical section;

[0007] A build-up section is arranged on one side of the vertical section, and a horizontal main borehole is arranged on one side of the build-up section;

[0008] A branch borehole is arranged on both sides of the outer surface of the horizontal main borehole, a spiral slotted screen pipe is arranged in the branch borehole, and a drillable bridge plug is arranged in the branch borehole and the horizontal main borehole;

[0009] A hydraulic jet tool is arranged on the surface of the branch borehole.

[0010] Preferably, the vertical segment extends from the surface to the target coal seam.

[0011] Preferably, the two ends of the directional drilling section are respectively connected to the vertical section and the horizontal main wellbore.

[0012] Preferably, the multiple branch wellbores are respectively distributed in a feather-like symmetrical pattern on both sides of the outer surface of the horizontal main wellbore.

[0013] Preferably, multiple drillable bridge plugs are provided to divide the branch wellbore into multiple fracturing sections, and each fracturing section is provided with a corresponding hydraulic jetting tool.

[0014] Preferably, the end of the branch well is fixedly connected to a radial borehole, and the inner wall of the radial borehole is coated with a nano-penetrating agent layer.

[0015] Preferably, a negative pressure extraction pump is installed at the bottom of the horizontal main wellbore.

[0016] Compared with related technologies, the horizontal well for increasing coalbed methane production and preventing gas outbursts provided by this utility model has the following beneficial effects:

[0017] This invention provides a horizontal well for coalbed methane production enhancement and gas outburst prevention. By expanding the reservoir exposure area through a feather-shaped branch structure and combining segmented fracturing and negative pressure extraction technologies, it significantly improves the efficiency and safety of coalbed methane extraction. Hydraulic jetting tools are used to perform directional perforation on each fracturing section to form a network fracture system. The spiral slotted screen improves the well body's resistance to deformation and extends the wellbore life. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of a first embodiment of a horizontal well for increasing coalbed methane production and preventing gas outbursts provided by this utility model;

[0019] Figure 2 for Figure 1 The diagram shows a cross-sectional view of a branch wellbore.

[0020] Figure 3 for Figure 2 The enlarged schematic diagram at point A is shown below;

[0021] Figure 4 This is a schematic diagram of the second embodiment of a horizontal well for increasing coalbed methane production and preventing gas outbursts, provided by this utility model.

[0022] The diagram is labeled as follows: 1. Vertical section, 2. Angled section, 3. Horizontal main borehole, 4. Branch borehole, 5. Spiral slotted screen, 6. Drillable bridge plug, 7. Hydraulic jetting tool, 8. Radial borehole. Detailed Implementation

[0023] The utility model is further described below in combination with the drawings and embodiments.

[0024] First embodiment

[0025] Please refer to Figure 1 、 Figure 2 and Figure 3 , wherein, Figure 1 It is a structure schematic diagram of a coalbed gas production and gas outburst prevention horizontal well first embodiment provided by the utility model; Figure 2 It is the enlarged schematic diagram of A shown in Figure 1 ; It is the breeding device structure schematic diagram shown in Figure 3 ; It is the breeding device structure schematic diagram shown in Figure 1 . A coalbed gas production and gas outburst prevention horizontal well, comprising: vertical section 1;

[0026] Build the section 2, the build the section 2 is arranged at one side of the vertical section 1, and the build the section 2 one side is provided with horizontal main borehole 3;

[0027] Branch borehole 4, a plurality of branch boreholes 4 are arranged on both sides of the outer surface of the horizontal main borehole 3, the inside of the branch borehole 4 is provided with spiral slotted screen pipe 5, and the branch borehole 4 and the horizontal main borehole 3 are provided with drillable bridge plug 6;

[0028] Hydraulic jetting tool 7, a plurality of groups of hydraulic jetting tools 7 are arranged on the surface of the branch borehole 4 respectively.

[0029] The vertical section 1 extends from the ground surface to the target coal seam.

[0030] The two ends of the build the section 2 are connected with the vertical section 1 and the horizontal main borehole 3 respectively.

[0031] A plurality of branch boreholes 4 are distributed on both sides of the outer surface of the horizontal main borehole 3 in feathered symmetry respectively.

[0032] The drillable bridge plug 6 is provided with a plurality of groups, and the branch borehole 4 is divided into a plurality of fracturing sections, and each fracturing section is provided with the hydraulic jetting tool 7.

[0033] The working principle of the coalbed gas production and gas outburst prevention horizontal well provided by the utility model is as follows:

[0034] In working, firstly, the traditional straight well only contacts with the coal seam through single wellbore, and a plurality of groups of feathered branch boreholes 4 extend to both sides of the main borehole, form a three-dimensional network structure similar to feather, and 6-12 branches can be arranged in a single well, so that the total contact area of the wellbore and the coal seam is expanded by tens of times, the diffusion distance of the coalbed gas molecules is significantly reduced, the desorption speed is accelerated, and the mining blind area caused by "pressure drop funnel" is avoided.

[0035] A plurality of drillable bridge plugs 6 separate the horizontal main borehole 3 and the branch borehole 4 into a plurality of independent fracturing sections, realize "staged reconstruction", the hydraulic jetting tool 7 precisely penetrates the casing and the coal seam, forms an initial fracture, injects high-pressure fracturing fluid (usually containing proppant), makes the initial fracture expand along the weak plane of the coal seam and branch, and finally forms a complex network fracture system; the network fracture communicates with the natural fracture, the permeability is increased by 10-50 times, a "highway" type seepage channel is formed, and through staged fracturing, different permeability areas can be targetedly reconstructed to improve the reserve producing degree.

[0036] Compared with the related art, the coalbed methane production increasing and gas outburst prevention horizontal well has the following beneficial effects:

[0037] The coalbed methane production increasing and gas outburst prevention horizontal well provided by the utility model expands the reservoir exposure area through the pinnate branch structure, significantly improves the coalbed methane mining efficiency and safety by combining the staged fracturing and negative pressure extraction technology, forms a network fracture system by using the hydraulic jetting tool 7 to implement directional perforation on each fracturing section, and the spiral slotted screen pipe 5 improves the deformation resistance of the well body, and the borehole service life is prolonged.

[0038] Second embodiment

[0039] Please refer to Figure 4 Based on the coalbed methane production increasing and gas outburst prevention horizontal well provided by the first embodiment of the utility model, the second embodiment of the utility model proposes another coalbed methane production increasing and gas outburst prevention horizontal well. The second embodiment is only a preferred mode of the first embodiment, and the implementation of the second embodiment does not affect the separate implementation of the first embodiment.

[0040] Specifically, the difference between the coalbed methane production increasing and gas outburst prevention horizontal well provided by the second embodiment of the utility model lies in that the coalbed methane production increasing and gas outburst prevention horizontal well, the end of the branch borehole 4 is fixedly connected with a radial drilling hole 8, and the inner wall of the radial drilling hole 8 is coated with a nano permeation agent layer.

[0041] The horizontal main borehole 3 is provided with a negative pressure extraction pump at the bottom.

[0042] The negative pressure extraction pump at the bottom generates an extraction amount of 50-100 m3 / min, so that the wellbore pressure is reduced to below the critical desorption pressure of the coal seam (usually <1 MPa), the gas is promoted to be desorbed from the coal matrix, the radial radial drilling hole 8 at the branch end further increases the exposure area of the coal seam, and the negative pressure field and the radial drilling hole form a "point-line-surface" three-dimensional extraction network, breaking the planar limitation of the traditional horizontal well.

[0043] The coalbed methane desorption rate is increased from 60-70% of the conventional horizontal well to more than 85%, which is equivalent to extracting 15-25% more coalbed methane resources, rapidly reducing the coal seam gas content (to below 8 m3 / t), and reducing the outburst risk.

[0044] The nanopermeation agent layer of the inner wall of the radial borehole 8 penetrates into the coal body micropore through intermolecular force, reduces the surface energy (γ) of the coal seam, after the surface energy is reduced, the elastic modulus (E) of the coal body is improved, the Poisson's ratio (v) is reduced, the anti-deformation ability is enhanced, the coal body damage is inhibited, the nanometer material changes the coal surface properties, reduces the gas adsorption amount (Langmuir volume VL is reduced by 10-15%), and reduces the gas internal energy.

[0045] The working principle of the coal bed gas production increasing and gas outburst prevention horizontal well is as follows:

[0046] In working, firstly, the negative pressure extraction pump is combined with the radial borehole 8, so that the coal bed gas desorption rate is increased to more than 85%, the production is obviously increased, the nanometer permeation agent layer reduces the surface energy of the coal seam, and the gas outburst risk is inhibited.

[0047] Compared with the related art, the coal bed gas production increasing and gas outburst prevention horizontal well has the following beneficial effects:

[0048] The coal bed gas production increasing and gas outburst prevention horizontal well is provided, the radial borehole 8 and the nanometer permeation agent layer are synergistically acted, the gas outburst risk is effectively reduced, is suitable for efficient development of various coal bed gas reservoirs, the production yield is higher than that of the traditional horizontal well, the production is obviously increased, the safety of the device is improved, and the service life is prolonged.

[0049] The above is only an embodiment of the utility model, and does not limit the patent range of the utility model, and equivalent structures or equivalent process conversions using the contents of the utility model specification and drawings, or direct or indirect application in other related technical fields are all included in the patent protection range of the utility model.

Claims

1. A coal bed gas stimulation and gas outburst prevention horizontal well, characterized in that, The application relates to a vertical section, a build-up section, a plurality of branch boreholes, a plurality of hydraulic jet tools and a plurality of drillable bridge plugs. The vertical section extends from the ground surface to a target coal seam. Two ends of the build-up section are respectively connected with the vertical section and the horizontal main borehole. The plurality of branch boreholes are respectively distributed in a feathered symmetrical manner on two sides of the outer surface of the horizontal main borehole. The drillable bridge plugs are provided with a plurality of drillable bridge plugs, and the branch boreholes are divided into a plurality of fracturing sections, and each fracturing section is provided with the hydraulic jet tool.

2. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, The end of the branch borehole is fixedly connected with a radial borehole, and the inner wall of the radial borehole is coated with a nano-penetration agent layer.

3. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, The bottom of the horizontal main borehole is provided with a negative pressure extraction pump.

4. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, ​ 5. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, ​ 6. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, ​ 7. The coal-bed gas stimulation and gas outburst prevention horizontal well of claim 1, wherein, ​

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