Drillstring Torsional Vibrations: Comparison Between Theory and Experiment on a Full-Scale Research Drilling Rig

1986 ◽  
Author(s):  
G.W. Halsey ◽  
A. Kyllingstad ◽  
T.V. Aarrestad ◽  
D. Lysne
Keyword(s):  
Full Scale ◽  
Torsional Vibrations ◽  
Drilling Rig ◽  
Theory And Experiment

Method for Fatigue Testing of Subsea Wellhead Connector Segments

2020 ◽  
Author(s):  
Pedro Barros ◽  
Agnes Marie Horn ◽  
Anders Wormsen ◽  
Per Osen ◽  
Kenneth A. Macdonald
Keyword(s):  
Fatigue Testing ◽  
Primary Objective ◽  
Full Scale ◽  
Test Method ◽  
Image Correlation ◽  
Stress Fields ◽  
Element Analysis ◽  
Test Fixture ◽  
Drilling Rig ◽  
The Coefficient Of Friction

Abstract For subsea well drilling, the drilling rig is connected to the subsea well by a marine riser and subsea BOP equipped with a remotely controlled wellhead connector latched onto the subsea wellhead profile. The level of cyclic loading on subsea wellheads is steadily increasing due to use of increasingly larger drilling rigs with larger BOPs, the drilling of wells in harsher environments characterized by strong high waves. The remotely controlled wellhead connector forces a series of locking dogs into an externally machined profile on the wellhead. This external profile is generally referred to as a wellhead profile. The fatigue resistance of this safety-critical connection is typically estimated by FE analysis. Due to the large size of the equipment, and high cost of testing, very limited fatigue testing, if any, has been carried out. A test method has therefore been developed, where a special test fixture is used to apply realistic boundary conditions and variable tensile loads to a small sector or segment of a wellhead connector. A primary objective is to generate fatigue-critical stress fields in the segments under tensile test load that closely replicates the stress fields in a full-scale connector subject to bending loads. A secondary objective is to support the introduction of the practice of testing several segments cut from a single wellhead connector. The testing of narrow sector segments allows the use of readily available test apparatus. It is thereby envisaged that the total cost of testing (specimens and test laboratory costs) can be substantially reduced in comparison with full-scale connector fatigue testing. This paper describes the text fixture, the connector locking dog, and wellhead segments designed to replicate the stress fields in a full-scale wellhead connector. The test fixture and test specimens are designed to match conditions and fatigue stress of the full-scale connector. The test specimens are instrumented with strain gauges at fatigue hotspots. Digital image correlation (DIC) is used to measure the relative motion between the wellhead segment and the locking dog. The measured strains are compared with corresponding values from finite element analysis of the test. The DIC results are also used for estimating the coefficient of friction between wellhead profile and locking dog. Very good agreement is found between measured hotspot strains and strains from the FE analyses for consistent load conditions. The test fixture is therefore considered suitable for segment fatigue testing, where the test results can be used to estimate the bending fatigue capacity of a full-scale wellhead connector. Results from fatigue testing by this test method are presented in a separate OMAE2020 paper.

Results From Fatigue Testing of Subsea Wellhead Connector Segments

2021 ◽  
Author(s):  
Agnes Marie Horn ◽  
Pedro Barros ◽  
Anders Wormsen ◽  
Per Osen ◽  
Kenneth A. Macdonald
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Fatigue Analysis ◽  
Full Scale ◽  
Test Method ◽  
Stress Fields ◽  
Test Results ◽  
Initiation Point ◽  
Drilling Rig

Abstract For subsea well drilling, the drilling rig is connected to the subsea well by a marine riser and subsea BOP equipped with a remotely controlled wellhead connector latched onto the subsea wellhead profile. The level of cyclic loading on subsea wellheads is steadily increasing due to use of increasingly larger drilling rigs with larger BOPs, the drilling of wells in harsher environments characterized by high waves. The remotely controlled wellhead connector forces a series of locking dogs into an externally machined profile on the wellhead. This external profile is generally referred to as a wellhead profile. The fatigue resistance of this safety-critical connector is typically estimated by finite element analyses (FEA). Due to the large size of the equipment, and high cost of testing, very limited fatigue testing, if any, has been carried out. A test method has therefore been developed, where a special test fixture is used to apply realistic boundary conditions and variable tensile loads to a small sector or segment of the wellhead connector. A primary objective is to generate fatigue-critical stress fields in the segments under tensile test load that closely replicates the stress fields in the full-scale wellhead connector. A secondary objective is to evaluate the possibility of using segment testing to determine the fatigue capacity of the full-scale connector. The testing of narrow sector segments allows the use of readily available test apparatus. It is thereby envisaged that the total cost of testing (specimens and test laboratory costs) can be substantially reduced in comparison with full-scale connector fatigue testing. This paper describes the fatigue testing of wellhead connector segments, and the test results in terms of cycles to failure and the failure modes, i.e. crack initiation point, and final crack geometry. The test scope consists of nine segments tested in-air at ambient temperature (nominal 20 °C), at a frequency of approximately 2 Hz under axial load of R = 0.1. At the time of writing this paper, six out of these nine tests have been performed. These six fatigue tests are presented in this paper. The test results are compared with estimates achieved by FEA of the test assembly and relevant S-N curves for the materials. It will be determined if the test results can be accurately predicted by the fatigue analysis methodology in Section 5.4 of DNVGL-RP-C203 (C203), including use of the new series of S-N curves for high strength materials in Appendix D.2 of C203. This design approach assumes that other failure modes (e.g. fretting or other local effects in the interface between components) do not govern the fatigue life, as this cannot be predicted by the fatigue analysis method applied here. The fatigue test set-up and the finite element analysis of the segment test is presented in the OMAE2020-18652 paper.

scholarly journals Experimental disturbance rejection on a full-scale drilling rig

2010 ◽  
Vol 43 (14) ◽  
pp. 1338-1343 ◽  
Author(s):  
Alexey Pavlov ◽  
Glenn-Ole Kaasa ◽  
Lars Imsland
Keyword(s):  
Disturbance Rejection ◽  
Full Scale ◽  
Drilling Rig ◽  
Experimental Disturbance

A Study of Rock-Bit Interaction and Wellbore Deviation

1986 ◽  
Vol 108 (3) ◽  
pp. 228-233 ◽  
Author(s):  
D. Ma ◽  
J. J. Azar
Keyword(s):  
Theoretical Study ◽  
Full Scale ◽  
Cutting Mechanism ◽  
Interaction Forces ◽  
Drilling Rig ◽  
Rock Bit

An overall analysis of wellbore deviation is presented. A theoretical study in side-cutting mechanism and side-cutting ability of roller cone bits is described. A full-scale drilling rig and a specifically designed cradle system for measuring rock-bit interaction forces are used to perform the experimental portion of this paper.

Electromagnetically excited torsional vibration to rock drilling support

2020 ◽  
pp. 1-14
Author(s):  
Tomasz Trawiński ◽  
Marcin Szczygieł ◽  
Arkadiusz Tomas
Keyword(s):  
Mathematical Models ◽  
Torsional Vibration ◽  
Drilling Process ◽  
Torsional Vibrations ◽  
Research Fund ◽  
Incident Response ◽  
European Research ◽  
Rescue Operation ◽  
Drilling Rig ◽  
Drilling System

During a serious underground incident the most important things are the lives of miners and the time necessary for the rescue team to find victims of the accident. The paper presents the concept of a new drilling system that uses torsional vibrations in the drilling process. In the article formulating mathematical models of a drilling rig is one of the tasks of the INDIRES (INformation Driven Incident RESponse) project implemented as a part of the European Research Fund for Coal and Steel. The INDIRES project is dedicated to the task of conducting a rescue operation after accidents in mines.

Electrostatic optics and aberration correction in the 1940s and today

1992 ◽  
Vol 50 (1) ◽  
pp. 6-7
Author(s):  
Gertrude F. Rempfer
Keyword(s):  
Electron Microscope ◽  
Focal Point ◽  
Focal Length ◽  
High Vacuum ◽  
Electron Optics ◽  
Applied Physics ◽  
Electrostatic Lenses ◽  
Commercial Instrument ◽  
The University ◽  
Theory And Experiment

I became involved in electron optics in early 1945, when my husband Robert and I were hired by the Farrand Optical Company. My husband had a mathematics Ph.D.; my degree was in physics. My main responsibilities were connected with the development of an electrostatic electron microscope. Fortunately, my thesis research on thermionic and field emission, in the late 1930s under the direction of Professor Joseph E. Henderson at the University of Washington, provided a foundation for dealing with electron beams, high vacuum, and high voltage.At the Farrand Company my co-workers and I used an electron-optical bench to carry out an extensive series of tests on three-electrode electrostatic lenses, as a function of geometrical and voltage parameters. Our studies enabled us to select optimum designs for the lenses in the electron microscope. We early on discovered that, in general, electron lenses are not “thin” lenses, and that aberrations of focal point and aberrations of focal length are not the same. I found electron optics to be an intriguing blend of theory and experiment. A laboratory version of the electron microscope was built and tested, and a report was given at the December 1947 EMSA meeting. The micrograph in fig. 1 is one of several which were presented at the meeting. This micrograph also appeared on the cover of the January 1949 issue of Journal of Applied Physics. These were exciting times in electron microscopy; it seemed that almost everything that happened was new. Our opportunities to publish were limited to patents because Mr. Farrand envisaged a commercial instrument. Regrettably, a commercial version of our laboratory microscope was not produced.

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