T The well FN-04 is located in Salam Field which is managed by PT. PertaminaEP is located on the Borneo island, located approximately 50 km east of SamarindaCity. Based on drilling operations at previous wells which always had very harmfullost circulation problems, the FN-04 well was decided to conduct drillingoperations with the casing drilling method on a trajectory 17-1/2 inch. Theselection of the casing drilling method is because the blind dilling method and LCMare not effective in dealing with lost circulation problems that occur so as to havean impact on increasing non-productive time. It is expected that with this casingdrilling method the problem of lost circulation in this field can be overcome andalso reduce non-productive time (NPT) especially when drilling the well FN-04.The well FN-04 was drilled vertically to a depth of 1078 mTVD, but 17-1/2 inchusing the casing drilling method only to a depth of 401 mTVD.The casing drilling method applied to this well FN-04 is a level 2 (nonretrievable BHA). Drilling is carried out from a depth of 36 meters to 401 metersTVD. Casing drilling operations are only used on intermediate casing. The casingused in this drilling is a conventional casing that has a diameter of 13-3/8 inch witha grade of K-55 and pounder 54.5 ppf. The coupling has a BTC type because it hasan API standard. The bit used is bitshoe with XCD3 type which is drillable bit. Theinitial planning of using some operating parameter estimations included a muddensity of 8.7 ppg, a rate of penetration of 100 ft/h, a string RPM of 40 rpm, afriction of 0.40 and a weight on bit of 10,000 lb. In the well FN-04 uses an MLTring which aims to increase the torsional casing to 63,630 lb-ft.As with conventional drilling, casing drilling operations in the well FN-04need to be evaluated and analyzed. Drilling mechanical parameters such as torque,drag, buckling analysis and hookload must be calculated because this method usesthe casing as drillstring so that the loads will increase compared to conventionaldrilling. The expense may not exceed the limit owned by the casing and rig. Basedon the evaluation of casing drilling operations the FN-04 well runs smoothly. Thelargest torque load in the field is 5,887 lb-ft smaller than the torsional casing withMLT ring and torsional casing drive system so that no problems arise due toexcessive torque loads. Maximum thrust load in the field of 16,970 lb is also smallerthan the thrust obtained from the weight of the drill string so that no stuck pipe willoccur due to drag load.In the casing drilling operation, the FN-04 well has no buckling problem orthe pipe is bent because the critical buckling casing of the K-55 is much larger than the weight on bit in the field as a compression load. The maximum hookload thatoccurs in the field is 70,390 lb smaller than the body yield and joint strength of thecasing K-55 so that the top casing is still able to bear the casing circuit load below.Hookload is also smaller than the hookload rig capacity of 600 klb so that the rigis capable of carrying out casing drilling operations. However, after optimizationof casing drilling operation does not require an MLT ring because the torsionalcasing is still able to withstand torque loads up to a depth of 401 meters.