Drill Bit Deformations in Rotary Drilling Systems under Large-Amplitude Stick-Slip Vibrations

Abstract

In oil and gas industry, rotary drilling systems are used for energy exploration and productions. These types of systems are composed of two main parts: mechanical and electrical parts. The electrical part is represented by rotating motor called top drive; however, the mechanical part of the system is composed of tool string with many pipes, at the bottom end of these pipes the bit is attached to cut the rock during their contact. Since the bit is in a direct contact with rock characteristic variations, it can be under risk for heavy damage. The latter is principally caused by the fact that the rock–bit interaction term is highly nonlinear and unpredictable. In literature, many mathematical models have been proposed for rock–bit interaction, but they do not reflect the dynamic of the bit under vibrations since torsional and axial vibrations are strongly coupled and synchronized with it. In industrial development, the design of drill bit has faced many improvements in order to overcome these vibrations and mitigate unpredictable phenomena. Even though, the practical use of these drill bits confirmed that there are still many failures and damages for the new designs; moreover, bits’ virtual life become shorter than before. The objective of this study is to analyze the drill bit deformations caused by the stick-slip vibration phenomenon which is characterized by high-frequency high-amplitude in rotary drilling systems. The obtained results were validated through a case study of MWD (measurement while drilling) data of well located in a Southern Algerian oil field.

Design of a New Type of Torsional Impactor and Analysis of Its Impact Performance

“…Installing the torque impactor and the drill bit above and applying periodic, high-frequency and high-torque torsional impact can effectively assist the drill bit to break rock efficiently, improve drilling efficiency, and reduce drilling cost [13][14][15][16][17]. Therefore, the performance of the torque impactor is mainly reflected in the following three parameters, namely impact force, impact torque, and impact frequency [5,9,10].…”

“…Influenced by drilling depth and rock formation characteristics, a problem will eventually arise when the bit torque is insufficient to break the formation, causing the bit to stop rotating instantaneously [2][3][4]. If the ground turntable is rotating normally when this happens, then the applied energy will be temporarily stored in the drill string, resulting in the drill string becoming twisted more and more tightly and the cutting torque being transmitted to the drill bit, causing it to become larger [5,6]. When torque is required for shearing and when the stratum breaks, then the energy of the drill string will be released instantly, causing the drill string and the drill bit to rotate violently; in other words, stick-slip vibration will occur [7][8][9].…”

Experimental Estimation of Design and Drilling Regime Option Influence on Drilling Tool Dynamics

“…Конструктивні особливості бурильної колони, а також специфіка умов її експлуатації та контактна взаємодія зі стінкою свердловини призводять до виникнення динамічних навантажень бурильного інструмента. Загальні проблеми взаємодії бурильних колон із різних металів зі свердловиною розглядалися, зокрема, у роботах [58][59][60], асимптотичні підходи щодо аналізу контакту труб з пружним середовищем представлені в працях [61][62][63]. У публікаціях [64][65][66] пропонуються різні підходи до інженерного моделювання контактних явищ у стрижневих конструкціях, а у працях [67][68][69] розглянута нестаціонарна динаміка пружних стрижнів із непружним зовнішнім опором.…”

Statistical Process Control Charts Applied to Rock Disintegration Quality Improvement

“…A simple scheme of the dynamic indentor-rock system, which is affected by two crucial measurable input variables-pressure force F (N) and revolutions n (rpm), is shown in Figure 2 [33][34][35][36][37].…”