Reservoirs in the R oilfield in Kazakhstan are characterized as layered carbonate reservoirs with condensate gas caps and edge-bottom water. Influenced by water injection, edge-bottom water intrusion, and gas cap development, the reservoir pressure maintenance level is low, and the distribution of the remaining oil is complex. After multiple times of measures such as adding perforation, acidification, and fracturing in production wells, the incremental oil production has decreased, and the effectiveness of measures has diminished. Based on core analysis and logging interpretation, the reservoirs are classified into four types. By conducting numerical simulation studies of the entire oilfield, nine types of remaining oil were identified based on reservoir types. Three main controlling factors affecting the productivity of sidetrack wells were determined using orthogonal experimental designs, and sidetrack well selection criteria were established. Considering the wellbore structure and remaining oil distribution characteristics, eight sidetrack modes for existing wells were established, determining effective methods for tapping remaining oil in carbonate reservoirs with gas caps and edge-bottom water. From the year of 2014 to the year of 2023, a total of 32 sidetrack wells were drilled, initially producing 17 tons of oil per day, three times the initial production of the surrounding wells, resulting in an incremental oil production of 471,000 tons. This study offers valuable insights for guiding sidetrack drilling in similar reservoirs.