The First Successful Short-Radius Re-Entry Well in Deep Gas Drilling in Saudi Arabia

摘要

This paper discusses the planning and execution of the first successful short-radius sidetrack in deep gas drilling in Saudi Arabia. ANDR-XYZ was sidetracked from vertical at 12,242 ft and built inclination to 90° with maximum dog leg severity recorded as 39°/100 ft. Thereafter, a 2,400 ft lateral was drilled in the Khuff-B reservoir. Total depth was revised because of deteriorating reservoir quality. The operating time was 53 days versus 60 days planned. The short-radius sidetrack was one of three options (option 3, below): 1. Sidetracking in the 9 5/8-in. casing set in the Khuff formation. Apart from cost reasons, this option was discarded because of high Jilh pressure requiring the mud weight to be increased from 102 pcf to 152 pcf, which would create well control and directional drilling difficulties. 2. Milling the 7-in. liner, drilling a new 8 3/8-in. hole, setting a new 7-in. liner, and then drilling a 5 7/8-in. hole across the reservoir. Apart from being time consuming and costly, this option did not reduce technical complexity since it might have exposed the 9 5/8-in. casing across the liner lap. The condition of this section could not be guaranteed because of a previous milling operation while drilling the original wellbore. 3. Re-entering the well by sidetracking in the 7-in. liner below the 9 5/8-in. casing. This required drilling a short- radius curve in the 5 7/8-in. section and continuing drilling and geosteering the well through the reservoir. Such a high buildup rate had never been successfully achieved before at this sidetrack depth in the Khuff reservoirs in Saudi Arabia. Several technical considerations were taken into account including the depth and type of whipstock, the length of rathole, design and analysis of the sidetrack bottomhole assembly (BHA) including torque and drag analysis, as well as overall operations strategy to achieve the well objectives. Several challenges were overcome and lessons were learned, which will be detailed in this paper. The successful delivery of this well resulted in saving of 45 rig days compared to the other options. The well also extended the frontier of drilling and workover options and opened up avenues to reenter several wells in deep gas drilling in Saudi Arabia.