Well pattern design and optimal deployment for coalbed methane development

Abstract: Based on the coalbed methane development of III block in the eastern edge of the Ordos Basin, the well pattern was optimized and dynamically adjusted, according to a system engineering including three stages: well pattern pre-development design stage, well site optimization stage and dynamic tracking stage. The geological basis for well deployment of coalbed methane was proposed and the parameters of well pattern design were optimized during the well pattern pre-development design stage. The geological conditions have been explored from several aspects which include coal bed structure, buried depth, coal seam thickness, roof and floor lithology, gas content, permeability and hydrological condition. The favorable production well pattern was the rhombus pattern. The cluster well was chosen as the main well type and then horizontal well. For the local anisotropy coal seam, rhombus long diagonal was in the direction of face cleats and short diagonal was in the direction of butt cleats. The well spacing was 300−350 m in high permeability zones and 350−400 m in low permeability zones. It is necessary to consider those factors, such as surface, subsurface and drilling conditions, to optimize the well locations during the well site optimization stage and to follow the basic requirements of “surface following subsurface, engineering following geology”. After having observed the well interference and interlayer interference phenomenon during the dynamic tracking stage, twenty-four production wells have been relocated and the producing layers for thirty-six production wells have been changed. Then the well pattern design was more reasonable in this block. It is confirmed that the posterior well pattern design and development mode are more reasonable after the optimal deployment in the III block during this five years. Key words: coalbed methane development, well pattern design, well pattern optimal deployment, production dynamic tracking, well relocation, producing layer adjustmen