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顶板裂隙带L型井负压抽采瓦斯技术研究及应用以靖远矿区魏家地煤矿为例

Research and application of negative pressure gas extraction technology using L-shaped wells in roof fracture zones: A case study of Weijiadi coal mine in Jingyuan mining area

  • 摘要: 裂隙带L型井抽采是降低煤矿工作面瓦斯灾害的有效手段,但技术难度较高,选层选位难和水平段稳定性差等关键问题亟待解决。以魏家地煤矿东1100工作面为研究区,在地质工程适用性分析和覆岩结构精细刻画的基础上,运用关键层和“O”型圈理论及高位环形裂隙体模型进行L型井选层定位,并采用Abaqus软件模拟回采条件下不同孔缝组合筛管应力变化,优选筛管规格,进一步开展工程实践与抽采效果评价,结果表明:① 东1100工作面煤层瓦斯含量和压力较高、水平最大主应力方向NE、煤炭开采采用仰斜推进和U型通风方式,适宜裂隙带L型井抽采。② 距煤层顶板70 m处的砂岩层介于裂隙带范围(41~140 m)内,且具有杨氏模量大(37.53 GPa)、泊松比小(0.30)、厚度大(>5 m)和连续性好的特征,可作为其水平段的垂向优选层位,该层位“O”型圈裂隙带距离回风巷28.43~59.73 m,是水平段平面优选位置。③ 十字交叉排列的圆形开孔(直径10 mm,间距250 mm,孔密度20孔/m),筛管最大主应力和主应变数值最小,为L型井实施的优选筛孔设计方案。④ 实钻过程中采用CMD-100型钻机、7LZ172×7.0-XISF型单弯1.5°螺杆钻具和MWD无线随钻三开钻进筛管完井,负压抽采瓦斯纯量在0.4×104、1.1×104 m3/d间高位波动,稳产时间超500 d;期间工作面高位钻孔从20 m/组调整为50 m/组,配风量从1 850 m3/mi降至1 470 m3/min,抽采率从52%提高到75%,实现矿井瓦斯与火的耦合防治。

     

    Abstract: L-shaped well extraction in fracture zones is an effective method to reduce gas disasters in coal mine working faces, but it faces significant technical challenges, such as difficulties in selecting layers and locations, and poor stability of horizontal sections. Take the East 1100 working face of the Weijiadi Coal Mine as the research area, Based on geological engineering applicability analysis and fine characterization of overlying rock structures, the key stratum theory, O-ring theory, and high-level annular fracture zone model were used to determine the optimal layer and location for L-shaped wells. Abaqus software was employed to simulate stress changes in different perforated screen pipes under mining conditions, and the optimal screen pipe specifications were selected. Engineering practices and extraction effect evaluations were further conducted. The results show that: ① The east 1100 working face has high gas content and pressure, with the maximum horizontal principal stress direction in the NE. The coal mining adopts an upward-inclined advance and U-type ventilation, making it suitable for L-shaped well extraction in fracture zones. ② The sandstone layer 70 m above the coal seam, located in the fracture zone (41−140 m), has a large Young's modulus (37.53 GPa), small Poisson's ratio (0.30), significant thickness (>5 m), and good continuity, making it the optimal vertical layer for the horizontal section. The O-ring fracture zone at 70 m above the roof, 28.43−59.73 m from the return airway, is the optimal horizontal plane location. ③ A staggered arrangement of circular perforations (10 mm diameter, 250 mm spacing, 20 holes/m) results in the smallest maximum principal stress and strain values, making it the optimal perforation layout for L-shaped well implementation. ④ During the actual drilling process, CMD-100 drilling rig, 7LZ172×7.0-XISF single-bend 1.5° screw drilling tool and MWD wireless three-opening drilling while drilling were used to complete the screen pipe. The pure volume of negative pressure gas extraction fluctuated at a high level between 0.4 × 104 m3/d and 1.1 × 104 m3/d, with stable production lasting over 500 days. During this period, the spacing of high-level boreholes in the working face was adjusted from 20 m per group to 50 m per group, the ventilation volume was reduced from 1850 m3/min to 1470 m3/min, and the extraction rate increased from 52% to 75%, achieving integrated prevention and control of mine gas and fire hazards.

     

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