Designing and Qualifying Equipment for a Potential World-Record Deepwater Casing Landing Operation

As the design of deepwater wells continues to evolve for unlocking new reserves from deeper and challenging reservoir conditions, longer and heavier casing strings are required to achieve various well objectives and operational efficiency. The mechanical requirements resulting from the landing and cementing of these heavy casing strings pushes the limits on current equipment. Landing and cementing such heavy casing designs presents numerous challenges to conduct the operation safely and efficiently, requiring the implementation of non-conventional alternatives to manage the loads for enabling the existing rigs to step-out of the normal drilling envelopes. For drilling the first deepwater 20,000 psi development well in Gulf of Mexico, the Operator required the large diameter nested liner strings to be deployed deeper than any offset well, for ensuring pressure containment while drilling and sufficient diameter for the larger production casing / completion equipment. As a result, the load of landing the 16″ nested liner string was expected to exceed 2.5 million lbf, which was outside of the operational capability of any existing equipment, including drilling rig, landing string and cementing head. The planning team assessed alternatives for running the liner with an existing drillship and the landing equipment available including pipe, cementing head and handling equipment. Rigorous measures had to be put in place in order to determine the technical requirements to qualify the equipment for the operation and better understand and mitigate the risks involved. These challenges were overcome by considerable planning in landing string design, handling equipment implementation, assessing rig load path and shearing capability for the heavy landing string, equipment design review and testing, and equipment inspections and qualifications. Specific areas of focus included: the use of heavy-duty, high yield, thick wall landing string through the BOP stack, upgrading the shearing and sealing capability of the rig's BOP stack, use of buoyed landing string above the BOP stack and the associated handling equipment, an increased load rating of cementing equipment by re-evaluating design and material, customized inspection criteria for all equipment to be used, and a thorough evaluation of landing string accessories to validate structural integrity. All parties involved provided significant effort to ensure that the equipment used in this string was fit for purpose. The stringent planning, ratings re-evaluation, and equipment qualifications helped ensure the successful landing of a potential world-record 2.49 million lbf hookload 16 in. liner string under challenging weather conditions. The successful landing of this string paves the way for future wells where similar design challenges will be faced.