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

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 139855, ’The First Successful Short-Radius Re-Entry Well in Deep-Gas Drilling in Saudi Arabia,’ by Shaker Al-Khamees, SPE, and Hope Okwa, SPE, Saudi Aramco, and Jaywant Verma, SPE, and Sukesh Ganda, SPE, Schlumberger, prepared for the 2011 SPE/IADC Drilling Conference and Exhibition, Amsterdam, 1-3 March. The paper has not been peer reviewed. Successful short-radius sidetracking in a deep gas area in Saudi Arabia is presented. Well ANDR-XYZ was sidetracked from vertical at 12,242 ft and built inclination to 90°, with maximum dogleg severity (DLS) recorded as 39°/100 ft. Thereafter, a 2,400-ft-long lateral was drilled in the Khuff-B reservoir. The sidetracking and lateral were drilled because of deteriorating production. The time required for this work was 53 days vs. the planned 60 days. The short-radius sidetrack was one of three options studied and resulted in saving 45 rig days compared with the other options. The well also extended the frontier of drilling and workover options and enabled opportunities to re-enter several other wells in deep gas areas in Saudi Arabia. Introduction Most deep gas wells in Saudi Arabia are drilled in the southern Ghawar field. The Late Permian Khuff-B and Khuff-C stacked carbonate reservoirs are the main gas-producing zones at depths of 11,500- to 12,500-ft true vertical depth. Two types of casing designs are used in these deep gas wells: “K1” and “K2.” In the conventional K2 profile, 133/8-in. casing is set from the surface to 30 ft into the base of Jilh dolomite formation. A 12-in. section is drilled into the Khuff-C carbonate, and 95/8-in. casing is set. Thereafter, 83/8-in. hole is drilled across Khuff or pre-Khuff reservoir. In a typical K1 design, in place of the 133/8-in. casing, 95/8-in. casing is set 30 ft into the base of the Jilh dolomite formation. An 83/8-in. section is drilled into the Khuff-C carbonate, and a 7-in. liner is run. After setting the 7-in. liner, 57/8-in. hole is drilled to the target formation. Occasionally while drilling these wells, higher pressures are encountered in the base of the Jilh formation. Therefore, the K2 design is preferred over the K1 design because it provides the opportunity to set an additional casing string. At planning stages, off-set wells are studied to finalize casing design. Because drilling a slimmer hole is faster and less costly, the K1 design is preferred when there is no history of high pressure in offset wells. While planning workover operations on Well ANDR-XYZ, various options were studied from the perspectives of cost, time, and technical feasibility. The short-radius-sidetrack technically was the only economically acceptable approach. The full-length paper details the conventional long-radius drilling approach, drilling options, and planning and execution of the first successful short-radius well in deep-gas drilling in Saudi Arabia. The objective of the Well ANDR-XYZ L1 re-entry was to sidetrack from the original vertical well in the Khuff-B formation and drill a 57/8-in. lateral targeting the Khuff-B reservoir.