Technology of accurately constructing collapse column water plugging plug in laminated multi branch horizontal wells

Karst collapsed pillar is a major flood disaster in coal mines. The treatment of collapsed pillar is usually carried out after the mine is flooded. How to realize the transformation from passive treatment to active prevention and control is one of the major problems in water prevention and control; In this paper, based on the preliminary screening findings of the three-dimensional seismic profile of the large vertical water guiding collapses pillar in Huainan mine, and the near-circular anomaly distribution on the seismic attribute slice, the core drilling of 7 boreholes on the ground and the group-hole pumping test were carried out, including the in-phase axis dislocation (pull-down) and the nearly circular abnormal distribution on the seismic attribute slice, the exploration and verification of 7 boreholes on the ground, such as coring drilling, group hole pumping test, well logging temperature measurement, pseudo current field leak detection, and comprehensive data comparison and research; It was further found out that the plane shape of the collapse column is approximately elliptical (the long axis of the collapsed pillar fracture zone is 95 m and the short axis is 74 m on the 1st coal seam floor), the vertebral body shape of “small at the top and large at the bottom” on the profile, the water-conducting fissure zone has developed Camelbottle sandstone with a top boundary height of 4 coal floor, and the basement is in the Cambrian limestone and the middle collapse column shape characteristics and hydrogeological conditions; It is proposed that in the fracture area of coal seam 1 floor of the collapse column, the design of multi branch horizontal wells (the spacing between adjacent horizontal wells is 40 m and the diffusion radius is 20 m) along the section of C3 Ⅱ group 9 ash and C3 Ⅰ group 3 ash of Taiyuan group respectively; The 320 m×290 m collapsed pillar plane treatment range is designed within 100 m beyond the water-conducting fissure zone; The results show that through the precise control of the multi-lateral horizontal well drilling trajectory, the implementation of the repeated filling + fracturing grouting process, and the targeted inspection of the grouting quality effect, it can be seen that the effective diffusion radius of the slurry in the fracture area of coal seam 1 exceeds 80 m, the thickness of the rock column in the aquifer of 1st coal floor is more than 81.8m, which is greater than the requirements of the water inrush coefficient of the Ordovician limestone high-pressure aquifer, and the “water stopper” of the collapsed pillar is accurately constructed in three dimensions on the plane and profile. The advanced treatment of north China karst collapsed pillar has been realized.