Drilling-with-casing (DwC) is a field-proven technology that has seen its application showcased as an innovative solution to mitigate wellbore stability issues and reduce well-construction costs. This technology has been around for several years, but was first deployed by Total Exploration & Production Nigeria (TEPNG) in November, 2006 on the well AKAMBA-2. AKAMBA-2 is a vertical exploration well drilled on the north-east sector of Total's Oil Mining Lease (OML) 102 offshore field (55 m water depth) in Nigeria. It was drilled as a stand-alone well using drilling-with- casing technology comprising 9 5/8-in.casing with PDC casing bit drilling shoe to drill the 12 1/4-in. section. By eliminating bit trips and other unplanned events related to conventional drillpipe drilling, this application resulted in significant time and cost saving and the attainment of a world record depth of 1,036 m for this size of casing drilling. This paper will describe this first application of the drilling-with-casing technology in the Niger Delta, its challenges and the cost saving benefits achieved with its application. Introduction With this first trial in Nigeria, TEPNG intended to save rig operations time by focusing on the following objectives:Eliminate hole stability issues typical with the surface hole in this field.Minimize the risk and complications of fluid losses.Eliminate the need for a 17 1/2-in. hole section and save a casing string.Successfully set the 9 5/8-in. surface/technical casing in order to have a sufficient shoe strength to drill through the reservoirReduce the drilling flat-time spot.Deploy a maturing technology for the first time in Nigeria with its cost saving benefits Akamba-2 vertical well was selected as the best candidate for trial because of extensive knowledge of the OML 102 field (Fig.1). TEPNG has been operating on this block for the last twenty years. A classic "rotate the casing" DwC system was considered for it's reliability and the number of records (at the time more than 500 jobs performed for casing size from 4–1/2 to 20 in.).
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