Traditionally, rigs are positioned over a well from the moment the surface casing is drilled till the installation of the wellhead Christmas Tree. This resulted in the loss of precious rig time as the rig is idling during online cementing. However, in Field A, offshore of Terengganu, Malaysia, a new approach has managed to eliminate such inefficiency drastically. This paper discusses the employment of offline cementing techniques made possible with distinctive wellhead technology, that enabled a fast, efficient, and safe drilling and completion.
In this offshore drilling program, five wells were successfully batched drilled and cemented offline by ingenious planning and skidding of the rig. As the first well has reached its depth, offline adapters with pressure compatible cementing heads and accessories are installed on the wellhead. This allowed the rig to skid to the adjacent wells to continue drilling while the previous well was being cemented with the use of full bore offline cementing adapters. Full bore offline cementing adapters helped maintained familiarity by allowing the use of simple conventional wiper plugs. These offline adapters are compatible with both mandrel and slip hangers and have pressure bleed off and monitoring capabilities. These steps were then repeated in all of the wells, from the surface casing till the tubing of these mono bore completions. Besides that, production and casing hangers come with barrier plug profiles allowing plugs to be pre-made up and tested. This reduced installation time on the rig floor and ensure that there was a positively tested barrier, before nippling down the riser. Hangers with seals also allowed for a single trip installation, further reducing rig time.
The five wells were drilled and completed in record-breaking time at an average of 7 days per well and below budget, resulting in a time saving of 31 hours and 18.5% of cumulative savings. In conclusion, this wellhead technology introduced a new approach to drilling and completion allowing vast improvement to the field economics and profitability to the development of marginal fields.