Design and Qualification of Critical Landing String Assemblies for Deepwater Wells

Abstract

Qualification of landing strings has become a major concern for oil industry operators as longer and heavier casing, tie-back or liner sections are required in deepwater and ultra-deepwater wells. Total buoyed weights are currently approaching two million pounds, making it imperative that every component in the landing string assembly is properly qualified. Any process which qualifies a landing string assembly must be multi-faceted, consisting of both design verification and a subsequent "fit for purpose" inspection. Experience has proven this approach is absolutely necessary to confirm all design assumptions hold true. Over the past six years, a systematic, field-proven, and reliable qualification process has been developed which has allowed operators to successfully land assemblies with buoyed weights up to 1.6 million pounds in water depths from 2,850 feet to almost 9,000 feet on semi-submersible rigs and drillships. This process addresses critical design considerations such as verification of specialty tool ratings, the effect of makeup torque on connection capacity, appropriate usage of existing slip crushing calculation methods, heave-induced dynamic loading, and minimizing the probability of plugs becoming lodged in the assembly. Inspection issues addressed include coverage and scheduling, traceability to ensure accurate material properties are used in all design calculations, full-length ultrasonic testing of the drill string, and proper inspection of components which are routinely inspected incorrectly. This paper details the most relevant aspects of this field-proven process, and reviews the implementation of this process by an operator for use on a broad range of casing and liner landing operations. The paper provides a concise summary of the approach that will allow the reader to confidently design for ever heavier loads while preventing costly (yet avoidable) failures during landing operations. Introduction Qualification of any landing string assembly requires the following steps be taken for each component:The design of the component is verified to have sufficient capacity for the anticipated loads. This can be accomplished either via classical engineering analyses, load testing of design prototypes, or a properly conducted finite element analysis (FEA).Material properties must meet the specified minimums used in all design calculations. Of primary concern for a landing string component is yield strength, but ductility and impact toughness are also critical for components with stress concentrators.The component must be properly inspected to ensure that prior service has not rendered it unfit for use in the given landing operation, and that all critical dimensions match those used when the component's capacity was verified.When deployed, the tool must be properly assembled within the landing string assembly.

Drilling Deep in Deep Water: What It Takes to Drill Past 30,000 ft

“…Extensive qualifications are often undertaken to ensure the integrity of each component of the landing string before use in a deepwater landing string. Processes for this qualification have been outlined at length in other papers (Cantrell and Beiriger, 2008). A thorough review of that process is beyond the scope of this paper, but several key issues that one should be aware of are:…”

Nonlinear Dynamic Characteristic Analysis of a Landing String in Deepwater Riserless Drilling

“…An approach to the design of deepwater riserless landing strings was proposed by Adams [23], which focuses on the selection of pipe joints and tool joints. e design, manufacture, testing, and operation of landing strings have also been discussed by Breihan et al [24], Jellison et al [25], and Cantrell et al [26]. However, in these studies, dynamic analysis did not get enough attention.…”