Installing 56 Surface Casing Strings in 40 Well Slots Successfully in Bohai Bay, China

Abstract

Abstract ConocoPhillips is developing the Peng Lai field in Bohai Bay offshore China with six wellhead platforms (WHP) in 28 m (92 ft) of water. Phase I entailed one 24 slot WHP and a leased FPSO that has been in production since 2002. Phase II will have five 40 slot WHP's and a permanent FPSO. Phase II production began in 2007. The 24 inner slots of four of the Phase II WHP's will have 20" drive pipe conductors and the 13 3/8" surface casing will be installed by drilling with casing. The 16 outer slots, 8 on the north row and 8 on the south row, will have 36" drive pipe conductors and provide dual bore 13 3/8" surface casing strings in each slot. These holes will be directionally drilled at a slight angle to facilitate subsequent directional drilling. The 56 wells drilled from a 40 slot WHP reduces the size and cost of the platform while providing additional wells to meet the reservoir development plan. A portion of the wells will be "pre-drilled" from a jack-up through the WHP jacket while the topsides are under construction. The 13 3/8" surface casing strings, using both the drill with casing and dual bore methods, are installed during batch setting programs. The jack-up pre-drills wells below surface casing until the topsides installation begins, at which time the jack-up moves to the next platform and repeats the process. After the topsides are installed on the WHP, a self contained platform rig continues the drilling and completion program. The drilling program on the last WHP, to be installed in 2009, will be conducted exclusively from a platform rig, including the 13 3/8" drill with casing program in all 40 slots. This paper will describe the well construction program as part of the field development plan, the installation procedures, results of the surface casing installation programs and the drilling cost savings realized as a result of using drill with casing and dual bore conductor technologies. Introduction The Peng Lai field was discovered in 1999 in Bohai Bay, China. See Figure 1. The Phase I drilling and completion operations began in April 2002 on one 24 slot WHP. Planning for Phase II included extensive studies performed by multi-discipline teams. Combining Phase I lessons learned and the drilling and completion best practices to meet the subsurface development plan resulted in a well construction plan and methodology optimized for Phase II development. The Bohai Bay Peng Lai Phase II development drilling is being conducted on five 40-slot WHP's using the combination of a jackup rig, the Nan Hai 1, and five DCWR's (drilling, completion, and workover rig). The Phase II well count is 228 wells, consisting of 162 producers, 54 water injectors, 7 appraisals, and 5 CRI (cutting re-injection) wells. There will be one CRI well on each WHP.