Study on Coal Rock Stress Sensitivity of Different Cleat Directions in Ordos Basin

Coal stress- sensitivity has serious impacts on the value of permeability during coalbed methane development, meanwhile, the permeability change woul d directly determine the success or failure of commercial exploitation of coalbed methane resources. The experimental studies have done for permeability change with d ifferent effective stress in different directions of coal in the Laokengkou mine of southeastern margin of Ordos Basin, such as parallel face cleats, vertical face cleats an d vertical bedding. The comparative analysis of coal permeability loss value accompanying direction changes during the pressurization and step- down process was don e. The results showed that the phases of stress sensitivity were varied in different coal cleat orientation, Where the strong stress sensitivity phase for parallel to the face cleats focuses on the effective stress was less than 8 MPa range, vertical cleats and vertical bedding planes concentrated in less than 6MPa, 4 MPa respectively. Consi dering the impacts of stress sensitivity during drainage for coalbed methane wells in nearly 200 m deep coal seam should carefully extraction, reducing amplitude of per meability reduction and time schedule, were proposed. Based on the permeability advantage of face cleats, the well network layout is the long axis of well network paral leling to the face cleats.