Flexible 3.5 in. O.D. MWD System Enhances Short Radius, Horizontal Drilling Applications in Shengli Oilfield, China

A 3.5in. O.D. MWD system has been developed which is capable of providing Directional and Gamma Ray services in short radius wells at build rates up to 3.3°/meter, a build rate that had not previously been available through conventional MWD technology. Specially selected materials, innovative tool joint design and an integral MWD Transmitter/Drilling sub-assembly have been utilised in older to withstand the stresses associated with high build rates while maintaining full functionality in small diameter drill collars. Innovative testing methods were required to qualify the system for short radius applications, resulting in the implementation of significant design improvements. Utilising the new MWD system with short radius drilling technology has opened up the possibility of horizontal re-entry of existing wells completed with small diameter casing. Three case histories in the Shengli Oil field are presented. The three re-entry wells, Y-CP1, X-CP1 and L-CP1 and originally been completed in 139.7mm casing. Two of the re-entry wells were kicked off through 2.1meter casing windows using oriented whipstocks with 118mm and 121 mm bits at 3235 and 2109 meters respectively. Well L-CP1 section milled 18 meters of casing then side-tracked and built angle, reaching a TD of 2906 meters measured depth. Build rates for the wells averaged 2.0°/meter with a maximum of 3.3°/meter. Maximum horizontal reach was 151 meters from landing point. Performance of the drilling and MWD systems was excellent during the drilling phase of the wells. Using the knowledge and experience gained it will be possible to utilise the equipment to re-complete and extend the life of the numerous wells that have been completed in small diameter tubing in the Shengli area. Well designs can be planned that could not have been considered using conventional technology. Significant production gains will be made as a result.