Revolutionary Pre-Set Well Design: Removing an Entire Section, Speeding Up Well Delivery by Six Days

Abstract

Abstract The conventional pre-set well design involves landing the well at high inclination (50 – 60 degree) on top of the reservoir using six (6) casing policy followed by drilling of multi-laterals across the reservoir using under-balance coiled tubing drilling (UBCTD). A novel well design is presented in this paper which eliminates one complete casing string without compromising the well's objectives. The 8-3/8-in. hole section is drilled across a highly charged formation and secured with a 7-in. liner. Consequently, a 5-7/8-in. section is then drilled and landed on top of reservoir. The well is later completed using 4-1/2-in. cemented liner, which is mandatory as per well requirement. In this paper, the critical design criteria are explored while combining these two (2) sections, considering well control requirements, and cementing methodologies to ensure proper separation of highly charged layers from the reservoir. This optimization has resulted in a time saving of six (6) days which enabled the well under study to set a record as the fastest well delivered in this category. This concept has been adopted in consecutive wells and is emerging as a new standard for the specific type of well. By combining the last two (2) sections in a single hole size, the time for running the 7-in. liner, 5-7/8-in. cleanout trip and drilling the short 5-7/8-in. hole is saved which results in a direct time savings for the operation. The paper details how the last section was drilled as an 8-3/8-in. hole and cased off with 7-in. × 4-1/2-in. liner tapered string using fit for purpose centralizers. Furthermore, to ensure the integrity of this solution, a clean-out bottom hole assembly (BHA) combined with inflow test assembly was run in hole and the shoe track was drilled till 20ft above shoe simultaneously. The integrity of cement job and liner top packer was validated by performing inflow test. The well is then completed with upper completions, production tree installed and well is temporary abandoned where the Coil Tubing Drilling (CTD) rig will come later in future to drill the remaining cement in shoe track and reservoir. The optimized well design explores the design criteria for combining of two (2) sections and presents a novel solution to explore such possibilities in other well designs.