Abstract: In order to form new injection-production well pattern,narrow injection-production well spacing,complement formation energy,and inhibiting bottom water coning,the potential of remaining oil enrichment region should be fully excavated.And therefore,the casing window side-tracking technology has been carried out in inefficient wells of northwest Yan-2 block of Ben Butu oilfield.Due to insufficient prophase construction experience,multiple coal seam of sidetracking slim hole section,strong grinding formation,long open hole intervals,abnormal formation pressure and etc.,the early construction of 2 wells are of slow well drilling,long periods and low penetration rate.Through optimizing the technical measures and various planned measures,serious construction should be timely adjusted and planned,and then the drilling cycle of follow-up4 wells has been significantly shortened,and the lateral drilling construction technology appropriate for the block has been worked out step by step.