Advance Technologies for Efficient Utilization of Well Slots in Offshore Platforms

Abstract

Well slots are the most essential resource in offshore oilfield development, and how to efficiently utilize limited well slots in offshore platform instead of building new offshore platform is the key to improve the economic benefits of oil fields. Firstly, well slot expansion technology of old offshore platform including hanging well slots inside and outside the offshore platform considering structure strength of old platform. Secondly, sidetracking new wells from old wells with low production is proposed to develop remaining oil near the old platform and sidetracking point is optimized towards deep to reduce footage. Thirdly, combined with reservoir, multilateral branch wells are drilled to improve oil drainage area and enhance oil recovery, moreover, branch bore open hole anchor and external packer are developed to hang sand control screen pipe and maintain wellbore stability instead of leaving branch hole without any sand control methods. Well slot expansion technology has been used in old platforms, and 35% wells slots have been added to drill new wells to develop remaining oil around old platform. In old well sidetracking, advanced sidetracking tool with high build up rate reaching 120 deg/100 ft is developed and applied in many wells including T shaped well, the sidetracking points have been moved down and the overall footage have been reduced compared with conventional build up tools, and single well construction period have been reduced by 2 days. Multilateral branch wells with 1268 meters long main bore and 2 branch bores have been successfully completed with open hole anchor and external packer to hanger sand control screen pipe, and the production rate is twice as that of the original branch bore without any sand control method. This technology has been applied in Bohai Oilfield and new platforms have been saved every year as re-utilization of well slots, which can also provide reference for other offshore oil fields.