High efficient gas extraction method of long drill hole directional segmental fracturing in soft and low permeability coal seam

• Main Authors: LI YUCHENG, LI LONGLONG, LI JUNQIAO, ZHANG HUAN, REN JIANYE, ZHAO TAO, ZHANG ZHITAO, YANG XUELIN
• Format: Patent
• Language: Chinese; English
• Published: 03.04.2020
• Subjects: EARTH DRILLING; EARTH DRILLING, e.g. DEEP DRILLING; FIXED CONSTRUCTIONS; MINING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR ASLURRY OF MINERALS FROM WELLS; SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, ORDRAINING IN OR OF MINES OR TUNNELS

The invention discloses a high efficient gas extraction method of long drill hole directional segmental fracturing in a soft and low permeability coal seam. The method comprises the following steps that firstly, a kilometer drilling rig passes through the coal seam from a coal seam floor rock tunnel to a roof rock seam to drill a horizontal fracturing hole, the horizontal fracturing hole is controlled to be in a rock stratum with a distance of 0.5 to 1 meter from the top boundary of the coal seam; then, the sectional downward directional perforating is carried out in the horizontal fracturinghole section to communicate with the lower target coal seam, and the target coal seam is subjected to step-by-step fracturing by adopting a hydraulic jet sectional fracturing technology; after fracturing of the horizontal fracturing hole is completed, a drainage gas production hole is drilled in the target coal seam again in the liquid discharging process, a full-sleeve pipe protection hole technology is adopted, and a sl