A Coal Seam Gas Field, operated by Origin Energy as upstream operator of the APLNG project in Queensland, Australia has been on commercial production since 2005. From inception to 2012 the development concept used vertical cavitated wells or vertical fracture stimulated wells. Four pilot surface to in-seam well pairs were successfully drilled and commissioned in 2012 and 2013. Based on the performance of these pilots, further development of the coal seam gas field converted from stimulated vertical wells to horizontal wells from 2015 onwards. Surface-in-seam (SIS), high-angle-sump-horizontals (HASH), and multi-laterals wells drilled with coil tubing technologies were implemented in the field. The paper describes horizontal wells drilling, completion and geo-steering technology. The optimal operational strategies of horizontal wells are also described and the production performance of horizontal wells are compared to the vertical well performance. The key factors contributing to the success of horizontal drilling in the field are presented.