Load-Carrying Capacity Analysis on Derrick of Offshore Module Drilling Rig

Abstract

Offshore module drilling rig has become an important equipment of offshore oil and gas development, especially, the significantly future application in the field of deep water. Due to the long time working and complex working conditions of in-service derrick of offshore module drilling rig, analysis of its load-carrying capacity assessment is of great significance. Field test shows that in common the derrick of offshore module drilling has an intrinsic defect of stress concentration in addition to external damages including initial bending and load eccentricity. In this paper, the finite element method is combined with field test method, two assessment methods are put forward, respectively. Stress concentration detection on derrick main rod is carried out by using metal magnetic memory detector, and the detection results show that larger degree of stress concentration phenomenon exists on eleven rods of derrick, and stress concentration degree of individual rod is serious. Loading stress test and finite element analysis are carried out on the derrick of offshore module drilling rig. According to comprehensive comparison, it is concluded that hoisting capacity for the derrick cannot reach 4500 kN. Two kinds of structure reinforcement scheme are proposed, and comparison results show that the reinforcement scheme with four legs can improve the actual load-carrying capacity of the derrick. Reinforced derrick can achieve the new design value of derrick carrying capacity. In this study, the evaluation method is correct, which can analyze the derrick carrying capacity of offshore module drilling rig more objective and accurate, and we also provide a new train of thought and reference for the steel structure carrying capacity assessment.

A Review and Prospect for Dynamic Load and Stability Check Method for Dual Derrick

“…Gusella [6] compared the dynamic characteristics of VegaA platform under wave loads and wind load in theoretical and experimental aspects, analyzed power amplification factor of wave load, provide a direction for further study. After calculating by modal analysis of derrick role by storms pitch, roll and heave phenomenon, Xiaojing Guan [7] obtained that if the ratio of each step frequency near 1 or integer, the inner system of derrick produced resonance. Jog frequency of engine as well as other external devices and vibration frequency of wave load coincided or closed to derrick's natural frequency, and then derrick system formed violent vibration.…”

Dynamic Characteristic Analysis and Structural Optimization Design of the Large Mining Headframe

“…Feng Guan conducted experiments on the large headframe of a drilling platform. Then, the bearing capacity of the large headframe was analyzed, and a reinforcement scheme was proposed [30]. Generally, the first and second eigenfrequencies of a large headframe are very closely spaced, and this could be an issue for the actual system identification from experimental recordings, especially in situ and under ambient vibrations.…”

Unconstrained Dynamic Simulation on Offshore Dual Derrick

“…Simulation methods used to obtain characteristics such as natural frequencies and mode shapes, design assessment and safety, and vibration response are becoming more popular and useful for performing studies on the derrick [1][2][3][4][5][6]. Due to the complex conditions of marine environments [7][8][9], extensive research is needed to understand the nature of loads acting on structures operating in the marine environment [10,11].…”