Vibration analysis of drillstrings with self-excited stick–slip oscillations

A review of drillstring vibration modeling and suppression methods

Unveiling complexity of drill–string vibrations: Experiments and modelling

A method and apparatus associated with the production of hydrocarbons is disclosed The method, which relates to modeling and operation of drilling equipment, includes constructing one or more surrogates for at least a portion of a bottom hole assembly (BHA) and calculating performance results from each of the one or more surrogates The calculated results of the modeling may include one or more vibration performance indices that characterize the BHA vibration performance of the surrogates for operating parameters and boundary conditions, which may be substantially the same as conditions to be used, being used, or previously used in drilling operations The selected BHA surrogate may then be utilized in a well construction operation and thus associated with the production of hydrocarbons

Methods and systems for modeling, designing, and conducting drilling operations that consider vibrations

This article is devoted to the study of the local contact between the drillstring and the well during drilling operations. The study focuses on the Bottom-Hole-Assembly (BHA), which is subjected to compression. The work is motivated by the need to understand the complex behavior of such a system, in order to improve control over their constructive and destructive potentials. The contact zone is first determined using a global finite-element model obtained from a specific computer program. Contact, which is assumed to be located somewhere on the drill-collar or on stabilizers, is prejudicial and leads to premature abrasive wear of the drillstring, reduction of the Rate Of Penetration (ROP) of the tool into the rock and reduction of the Mean Time Between Failure (MTBF). The proposed mathematical model is expressed in terms of four independent degrees of freedom which are radial displacement, rotation of the section considered, bending along the tangential direction and torsion of the string. They include the effects of bending and torsion, the whirling motion of the drillstring as well as friction phenomena occurring between the drillstring and the well. The tangential effect is modeled by using Coulomb's law of friction. The nonlinear equations of movement are derived using Lagrange equations and are solved numerically to obtain the response. Specific attention is paid to the study of friction and a consistent contact model capable of taking into account the rolling of the drillstring, both with and without slip, is included in the model. This paper also presents a parametric study on the influence of the initial position of the string and the friction coefficient of the contact on the dynamic behavior of the structure. The model is validated by an experimental set-up equipped with two opto-electronic devices.

A Nonlinear Well-Drillstring Interaction Model

This paper presents a mathematical method for the computation of torsional resonance frequencies in a drillstring. The torsional resonance frequencies in a drillstring are readily calculated from the nominal drillstring dimensions. A high degree of accuracy is achieved when a correction factor to the torsional propagation velocity in drillpipe due to the offsets at the drillpipe joints is incorporated into the calculations. The theory and computer program were tested against data recorded in a 1000m deep, nearly vertical well. Torsional spectra were recorded with the bit off bottom at 450m, 550m, and 1000m and while drilling. Well defined torsional resonances were observed for frequencies up to 40 HZ. The calculated resonance frequencies are in very good agreement with all experimental data.

T.V. Aarrestad

Papers

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