Construction method for horizontal well along coal seam

Abstract

The invention discloses a construction method of a horizontal well along a coal seam, which relates to the field of coal mine ground drilling and comprises the following steps: constructing a first well opening section, constructing a second well opening section and constructing a third well opening section; before drilling of the third-opening well section, geological software is adopted to model and predict a coal seam section and a third-opening well section design track according to peripheral drilling and coal seam stoping conditions; in the drilling process of the third well section, a wireless mud pulse orientation instrument and an orientation gamma instrument are adopted to monitor coal seam changes and actual drilling tracks while drilling, the drilling tracks are adjusted in real time according to monitoring data, and a drill bit is kept to drill in the range of 0-2 m from the coal seam to a roof layer. The method has the advantages that it is ensured that the horizontal well drilling track control range and the coal seam drilling rate meet the design requirements, and the method plays a positive promoting role in guaranteeing safe, efficient and green mining of a coal mine.

Description

Technical Field

[0001] The invention relates to the field of coal mine surface drilling, and in particular to a method for constructing a horizontal well along a coal seam. Background Art

[0002] At present, the gas control mode is mainly based on the mining of protective layers and pre-extraction of underground drilling holes, supplemented by wells in the surface mining area. In areas where the gas pressure reaches more than 3MPa, it is not allowed to take measures underground. It is urgent to study new gas control modes to fundamentally solve the gas control problem. At present, some mining areas use horizontal wells to pre-extract gas. For example, the patent document with publication number CN115749923A discloses a method for pre-extraction of gas by staged fracturing of horizontal wells through tunnels in a joint well-ground excavation strip. When the existing horizontal well drilling method is applied to soft and low-permeability coal seams, it is difficult to control the wellbore trajectory and coal seam drilling rate during drilling, and the safety and efficiency are low; the stability of the formation is poor, and coal seam collapse and block falling are prone to occur; the sand return of the vibrating screen is poor, and there is precipitation or rock debris accumulation bed when drilling; the friction resistance of the well wall is large, and it is difficult to smoothly lower the casing. Summary of the invention

[0003] The technical problem to be solved by the present invention is to effectively control the wellbore trajectory and the coal seam drilling rate during the drilling process for horizontal well construction in soft and low-permeability coal seams.

[0004] The present invention solves the above technical problems by the following technical means: a method for constructing a horizontal well along a coal seam, comprising the following steps:

[0005] Step 1, constructing a well opening section, wherein the well opening section is a vertical well section;

[0006] Step 2, constructing a second well section, wherein the second well section includes a vertical well section and an arc well section;

[0007] Step 3, constructing three well sections, wherein the three well sections are horizontal well sections;

[0008] Before drilling the three-opening section, geological software modeling is used to estimate the coal seam profile and the designed trajectory of the three-opening section according to the surrounding drilling conditions and coal seam recovery conditions; during the drilling of the three-opening section, wireless mud pulse directional instruments and azimuth gamma instruments are used to monitor coal seam changes and actual drilling trajectories while drilling, and the drilling trajectory is adjusted in real time according to the monitoring data to keep the drill bit drilling within the coal seam 0 to 2 m away from the roof layer.

[0009] As an optimized technical solution, the mud used in the three well sections includes the following components by mass fraction: 0.1% to 0.2% caustic soda + 0.1% to 0.2% soda ash + 3% to 5% bentonite + 0.5% to 1% salt-resistant and high-temperature-resistant fluid loss reducer + 0.5% to 1% modified starch + 0.5% to 1% polyanionic cellulose + 0.5% to 1% salt-resistant copolymer + 2% to 3% cationic emulsified asphalt + 0.5% to 1% sulfonated asphalt + 11.5% to 12.5% ​​potassium chloride + 11.5% to 12.5% ​​sodium chloride + 0.3% to 0.5% shale inhibitor + 1% to 1.5% complex aluminum inhibitor + 0.1% to 0.5% film-forming agent + barite powder, and the balance is saturated brine.

[0010] As an optimized technical solution, the pumping volume for drilling the three-well section is 20 to 30 L / s.

[0011] As an optimized technical solution, the top drive speed for drilling the three-well section is 30-35r / min.

[0012] As an optimized technical solution, the drilling speed of the three-hole drilling section is 0.2-0.3 m / min.

[0013] As an optimized technical solution, the reaming method for the three-opening well section drilling is: after the single-root directional drilling is completed, the pump volume is reduced to 10-12L / s, the top drive rotation is stopped, and the reaming is performed after the drill is lifted 2-3m, and the reaming speed is less than 2m / min.

[0014] As an optimized technical solution, during the drilling process of the three-well section, a short start is performed every 190 to 210 meters of drilling.

[0015] As an optimized technical solution, during the drilling process of the three-opening section, if the torque or pump pressure changes by more than 2KN·m / Mpa, or the coal volume changes abnormally, the drill bit will be immediately lifted off the bottom of the hole, and drilling will continue after the circulation returns to normal.

[0016] As an optimized technical solution, during the drilling of the three-well section, the mud density is controlled at 1.18 g / cm 3 above.

[0017] As an optimized technical solution, after drilling is completed, the casing is lowered into the three-opening well section by rotating the casing.

[0018] The advantages of the present invention are:

[0019] 1. For the horizontal well construction in soft and low-permeability coal seams, measurement while drilling instruments are used for while drilling monitoring, and the drilling trajectory is adjusted in real time to ensure that the control range of the horizontal well drilling trajectory and the coal seam drilling rate meet the design requirements, which plays a positive role in ensuring safe, efficient and green mining of coal mines.

[0020] 2. Optimize the drilling fluid material, determine the material ratio through indoor experiments, optimize the amount of related materials according to the actual performance on site, and form a mud system suitable for drilling in soft and easily collapsed coal seams. This mud system: 1) has a strong anti-collapse ability and can effectively prevent the collapse and falling of coal seams. The film-forming agent can form a film around the well wall to prevent free water from entering the formation; asphalt materials can form a seal and bond to the cracks in the formation, further improving the stability of the formation. 2) It has good carrying capacity, the vibrating screen returns sand well, and there is no precipitation or rock debris accumulation bed when drilling. 3) It has good lubrication properties and effectively reduces friction resistance. No special lubricant is added to this system. The emulsified asphalt in the system has certain lubrication properties. The torque is stable during directional drilling, the friction resistance is small, and the casing is smooth in the later stage.

[0021] 3. Explore the drilling parameters such as pump volume, top drive speed, drilling speed, etc. when drilling along the coal seam, and use methods such as eye reaming, short start, and abnormal processing to form a complete set of horizontal well drilling technology for soft and easily collapsed coal seams.

[0022] 4. Use the rotating casing method to achieve smooth casing installation in soft and easily collapsed coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the wellbore structure of an embodiment of the present invention.

[0024] Figure 2 It is a schematic diagram of the estimated coal seam profile and the designed trajectory of the three well sections according to an embodiment of the present invention.

[0025] Figure 3 This is a comparison diagram of the designed trajectory and the actual drilling trajectory of the well opening section in Example 3 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0027] like Figure 1 As shown, the embodiment of the present invention discloses a method for constructing a horizontal well along a coal seam, comprising the following steps:

[0028] Step 1: construct a well section 1, which is a vertical well section.

[0029] Step 2: construct the second well section 2, which includes a vertical well section and an arc well section.

[0030] Step three, construct the third well section 3, which is a horizontal well section.

[0031] In order to match the existing drilling tools and adapt to high inclination rate drilling, the first opening section 1 and the second opening section 2 are expanded to reach the designed hole diameter. The drilling tool combination is shown in Table 1.

[0032]

[0033]

[0034] According to the coal seam characteristics, wellbore structure design, drilling process requirements, etc., the construction technical difficulties were fully evaluated, and it was decided to use a strong inhibition of brine film-forming mud system in the third well section 3. The mud performance requirements are shown in Table 2.

[0035]

[0036] The mud used in the third well section 3 includes the following components by mass fraction: 0.1%~0.2% caustic soda + 0.1%~0.2% soda ash + 3%~5% bentonite + 0.5%~1% salt-resistant and high-temperature-resistant fluid loss reducer + 0.5%~1% modified starch + 0.5%~1% polyanionic cellulose (PAC-LV) + 0.5%~1% salt-resistant copolymer + 2%~3% cationic emulsified asphalt + 0.5%~1% sulfonated asphalt + 11.5%~12.5% ​​potassium chloride + 11.5%~12.5% ​​sodium chloride + 0.3%~0.5% shale inhibitor + 1%~1.5% complex aluminum inhibitor + 0.1%~0.5% film-forming agent + barite powder, the remainder is saturated brine, and the specific amount of barite powder is determined according to the specific gravity required on site.

[0037] The mud system was used in the drilling process of the third well section 3 to achieve relatively ideal results. The specific performance is as follows:

[0038] 1) The mud system has a strong anti-collapse ability and can effectively prevent the collapse and block falling of coal seams. The film-forming agent can form a film around the well wall to prevent free water from entering the formation; the asphalt material can seal and bond the cracks in the formation, further improving the stability of the formation.

[0039] 2) The mud system has good carrying capacity. During the construction of the third well section 3, the mud viscosity was maintained between 50 and 60 seconds, the vibrating screen returned sand well, and there was no precipitation or cuttings accumulation during drilling.

[0040] 3) The mud system has good lubrication performance and effectively reduces friction resistance. The system does not add special lubricants, and the emulsified asphalt in the system has certain lubrication performance. During directional drilling, the torque is stable, the friction resistance is small, and the casing is smoothly lowered in the later stage.

[0041] The parameters and related requirements for drilling in Section 3 are as follows:

[0042] 1) The pump volume is 20-30L / s.

[0043] 2) The top drive speed is 30~35r / min.

[0044] 3) The drilling speed is 0.2~0.3m / min, and the drilling pressure should be adjusted reasonably.

[0045] 4) The reaming method is as follows: after the single-thread orientation is completed, the pump volume is reduced to 10-12L / s, the top drive rotation is stopped, and the drill is lifted 2-3m before reaming. The reaming speed is less than 2m / min.

[0046] 5) During the drilling process, short lift is performed every 190 to 210 meters.

[0047] 6) During drilling, if the torque or pump pressure changes by more than 2KN·m / Mpa, or the coal volume changes abnormally, immediately lift the drill bit off the bottom of the hole and continue drilling after the circulation returns to normal.

[0048] 7) During drilling, the mud density is controlled at 1.18g / cm 3 above.

[0049] like Figure 2 As shown, before drilling the third well section 3, geological software modeling was used to estimate the coal seam profile and the designed trajectory of the third well section according to the surrounding drilling and coal seam recovery conditions, including the designed coal seam boundary 4, the designed landing point 5 of the second well section, the designed trajectory 6 of the third well section and the designed top exploration area 7.

[0050] like Figure 3 As shown, during the drilling of the third well section 3, wireless mud pulse directional instruments and azimuth gamma instruments are used to monitor coal seam changes and actual drilling trajectory 8 while drilling. The monitoring points of the actual drilling trajectory 8 include the starting point 81 of the first coal seam sighting in the third well section, the end point 82 (top exploration) of the first coal seam sighting in the third well section, the starting point 83 of the second coal seam sighting in the third well section, and the end point 84 of the second coal seam sighting in the third well section. The drilling trajectory is adjusted in real time according to the monitoring data to keep the drill bit drilling in the coal seam within 0 to 2 m from the roof layer to ensure that the drilling trajectory control range and the coal seam encounter rate meet the design requirements.

[0051] After drilling is completed, the casing is lowered into the third well section 3 by means of a rotary casing lowering method. The rotary casing lowering device may adopt an existing rotary guide shoe, a rotary centralizer, and the like.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a horizontal well along a coal seam, characterized in that: The following steps are involved: Step 1, constructing a well opening section, wherein the well opening section is a vertical well section; Step 2, constructing a second well section, wherein the second well section includes a vertical well section and an arc well section; Step 3, constructing three well sections, wherein the three well sections are horizontal well sections; Before drilling the three-opening section, geological software modeling is used to estimate the coal seam profile and the designed trajectory of the three-opening section according to the surrounding drilling conditions and coal seam recovery conditions; during the drilling of the three-opening section, wireless mud pulse directional instruments and azimuth gamma instruments are used to monitor coal seam changes and actual drilling trajectories while drilling, and the drilling trajectory is adjusted in real time according to the monitoring data to keep the drill bit drilling within the coal seam 0 to 2 m away from the roof layer.

2. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: The mud used in the three well sections includes the following components by mass fraction: 0.1% to 0.2% caustic soda + 0.1% to 0.2% soda ash + 3% to 5% bentonite + 0.5% to 1% salt-resistant and high-temperature-resistant fluid loss reducer + 0.5% to 1% modified starch + 0.5% to 1% polyanionic cellulose + 0.5% to 1% salt-resistant copolymer + 2% to 3% cationic emulsified asphalt + 0.5% to 1% sulfonated asphalt + 11.5% to 12.5% ​​potassium chloride + 11.5% to 12.5% ​​sodium chloride + 0.3% to 0.5% shale inhibitor + 1% to 1.5% complex aluminum inhibitor + 0.1% to 0.5% film-forming agent + barite powder, and the balance is saturated brine.

3. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: The pumping capacity of the three-well section drilling is 20-30 L / s.

4. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: The top drive speed during the three-well section drilling is 30-35 r / min.

5. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: The drilling speed of the three-well section drilling is 0.2-0.3 m / min.

6. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: The reaming method for drilling the three-well section is as follows: after the single-thread orientation is completed, the pump volume is reduced to 10-12 L / s, the top drive rotation is stopped, and the reaming is performed after the drill is lifted for 2-3 m, and the reaming speed is less than 2 m / min.

7. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: During the drilling process of the three-well section, a short start is performed every 190 to 210 meters of drilling.

8. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: During the drilling process of the three-opening section, if the torque or pump pressure changes by more than 2KN·m / Mpa, or the coal volume changes abnormally, the drill bit is immediately lifted off the bottom of the hole, and drilling is continued after the circulation is normal.

9. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: During the drilling process of the three-well section, the mud density is controlled to be above 1.18g / cm3.

10. The method for constructing a horizontal well along a coal seam according to claim 1, characterized in that: After drilling is completed, the casing is lowered into the three-opening well section by rotating the casing.

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