Increasing Penetration Rate of Drill String by Optimum Positioning of Stabilizers

2010 ◽  
Author(s):  
Reza Kazemi ◽  
Ali Asghar Jafari ◽  
Mohammad Faraji Mahyari
Keyword(s):  
Potential Energy ◽  
Penetration Rate ◽  
Summation Method ◽  
Drill String ◽  
Lateral Vibration ◽  
Nonlinear Stability Analysis ◽  
Nonlinear Method ◽  
Stiffness Constant ◽  
Optimum Arrangement ◽  
Linear And Nonlinear

In this research, optimum arrangements of drill string’s stabilizers are investigated. The optimum arrangement leads to biggest WOB without buckling. So the penetration rate of the drill bit can be increases. To this goal, the potential energy of drill string for axial and lateral vibration is written in an integral equation. In this equation, the effect of geometrical shortening, which causes nonlinear coupling between axial and lateral vibration, is considered. The work done by WOB force and weight of drill string is calculated. The mode summation method is employed to convert the integral potential energy of the continuous system to a discrete one. The effects of stabilizers are modeled by linear springs with large stiffness constant. Dropping and considering third and fourth order tensor of potential energy lead to linear and nonlinear stability analysis, respectively. Taking first and second order derivatives of discrete potential energy, the stability of drill string can be analyzed. Repeating this procedure for different numbers and positions of stabilizers, the optimum arrangement of stabilizers can be found. This method is employed to find the best arrangement of one and two stabilizers, by linear and nonlinear method.

The Effect of Drilling Mud Flow on the Lateral and Axial Vibrations of Drill String

2010 ◽  
Author(s):  
Reza Kazemi ◽  
Ali Asghar Jafari ◽  
Mohammad Faraji Mahyari
Keyword(s):  
Potential Energy ◽  
Lagrange Equation ◽  
Continuous System ◽  
Summation Method ◽  
Drill String ◽  
Hertzian Contact ◽  
Lateral Vibration ◽  
Drilling Mud ◽  
Lateral Vibrations ◽  
Mud Flow

In this research, the effects of drilling mud flow and WOB force on the lateral vibration of drill string are investigated. To this goal, the kinetic and potential energy of drill string for axial and lateral vibrations are written in an integral equation. In potential energy equation, the effect of geometrical shortening, which causes nonlinear coupling between axial and lateral vibration, is considered. Drilling mud forces are modeled by Paidoussis formulations. The works done by WOB force, weight of drill string and drilling mud forces are calculated. The mode summation method is employed to convert the continuous system to a discrete one. Dropping and considering third and fourth order tensor of potential energy lead to linear and nonlinear system, respectively. The effects of stabilizers are modeled by a linear stiff spring. The wall contact is modeled by Hertzian contact force. Lagrange equation is employed for finding the equations of motions. First and second natural frequencies of drill string are found for different WOB and drilling mud flow. Also the effects of drilling mud and nonlinear terms on lateral vibration of drill string are investigated. The effect of drilling mud on the post buckling vibration of drill string is also delivered. This formulation can be used for optimization of drilling mud flow, WOB and the number and positions of stabilizer so that the lateral vibration of drill string is minimized.

New Approach to Linear and Nonlinear Stability Analysis of Drill String

2010 ◽  
Author(s):  
Ali Asghar Jafari ◽  
Reza Kazemi ◽  
Mohammad Faraji Mahyari
Keyword(s):  
Stability Analysis ◽  
Potential Energy ◽  
Nonlinear Stability ◽  
Equilibrium Position ◽  
Continuous System ◽  
Drill String ◽  
Order Derivative ◽  
Nonlinear Stability Analysis ◽  
New Approach ◽  
Linear And Nonlinear

In this research, a new approach for stability analysis of drill string is investigated. To this goal, the potential energy of drill string for axial and lateral vibrations is written in an integral equation. In this equation, the effect of geometrical shortening, which causes nonlinear coupling between axial and lateral vibration, is considered. The work done by WOB force and weight of drill string is calculated. The finite element method is employed to convert the integral potential energy of the continuous system to a discrete one. The effects of stabilizers are modeled by dropping the nodes coincided with them. Dropping and considering third and fourth order tensor of potential energy lead to linear and nonlinear stability analysis, respectively. Taking the first order derivative of discrete potential energy, the equilibrium position of drill string can be found. Taking second order derivative, the stability of the equilibrium position can be analyzed. Illustrated results demonstrate that as the length of hole is increased, the differences between linear and nonlinear cases become larger. This analysis shows the working condition of drill string is stable or not. These results can be used to obtain safe working conditions in drilling progress.

Drill string instability reduction by optimum positioning of stabilizers

2009 ◽  
Vol 224 (3) ◽  
pp. 647-653 ◽  
Author(s):  
M F Mahyari ◽  
M Behzad ◽  
G R Rashed
Keyword(s):  
Potential Energy ◽  
Equilibrium Position ◽  
Continuous System ◽  
Summation Method ◽  
Drill String ◽  
Degree Of Freedom ◽  
Second Derivative ◽  
First Derivative ◽  
Weight On Bit ◽  
Mode Summation Method

The main aim of this article is to find the optimum positions of the stabilizers that reduces the vibration and leads to the largest weight on bit (WOB) in drill strings. In this work, the potential energy of drill strings has been derived by considering the drill string weight and WOB. The potential energy of this continuous system is considered as a multi-degree-of-freedom system by the mode summation method. The equilibrium position of the system and its stability is determined by finding the roots of the first derivative and the sign of the second derivative of the potential energy, respectively. Using this formulation, the best positions of stabilizers that lead to the largest WOB can be found for different numbers of stabilizers. The best arrangement of the stabilizer's position on a drill string with one, two, and three stabilizers is investigated.

The Effect of Drilling Mud on Nonlinear Instability Threshold of Drill String

2010 ◽  
Author(s):  
Ali Asghar Jafari ◽  
Reza Kazemi ◽  
Mohammad Faraji Mahyari
Keyword(s):  
Potential Energy ◽  
Integral Form ◽  
Drill String ◽  
Instability Threshold ◽  
Drilling Process ◽  
Lateral Vibration ◽  
Drilling Mud ◽  
The Finite Element Method ◽  
Flutter Instability ◽  
External Forces

The main goal of this research is to analyze the effect of drilling mud and WOB on instability threshold of drill string. To this end, the kinetic and potential energy of an element of drill string for axial and lateral vibration is written in an integral form. The effect of geometrical shortening is considered in potential energy. The effect of drilling mud is modeled by the Paidoussis model. The works done by external forces are calculated. The finite element method is employed to discretize the system. The effects of stabilizers are modeled by dropping the nodes coincided with them. Flutter instability analysis is employed to analyze drill string’s instability threshold. By this procedure, the instability threshold of drill string is obtained for different WOB and drilling mud flow. Also, the effects of stabilizers numbers and arrangements are also illustrated. These results may be used for choosing the safe domain of drilling process.

scholarly journals Linear and nonlinear stability analysis of binary viscoelastic fluid convection

2013 ◽  
Vol 37 (16-17) ◽  
pp. 8162-8178 ◽  
Author(s):  
Mahesha Narayana ◽  
Precious Sibanda ◽  
Pradeep G. Siddheshwar ◽  
G. Jayalatha
Keyword(s):  
Stability Analysis ◽  
Viscoelastic Fluid ◽  
Nonlinear Stability ◽  
Nonlinear Stability Analysis ◽  
Fluid Convection ◽  
Linear And Nonlinear

scholarly journals Analysis on the lateral vibration of drill string by mass effect of drilling fluid

2019 ◽  
Vol 10 (2) ◽  
pp. 363-371 ◽  
Author(s):  
Chunxu Yang ◽  
Ruihe Wang ◽  
Laiju Han ◽  
Qilong Xue
Keyword(s):  
Drilling Fluid ◽  
Dynamic Pressure ◽  
Mass Effect ◽  
Drill String ◽  
Natural Vibration Frequency ◽  
Lateral Vibration ◽  
Test Results ◽  
Additional Mass ◽  
Mass Coefficient ◽  
Fluid Environment

Abstract. It is well known that the influence of the internal and external drilling fluid on the lateral vibration characteristics of drillstring cannot be ignored. In this paper, experiment apparatus for simulating drillstring vibration was established. Hammering method is used to measure drillstring lateral natural vibration frequency when the internal and external drilling fluid is considered. The test results show that the drilling fluid can decrease the natural frequency of the drillstring. Based on the simulation model, considering the influence of the internal and external drilling fluid, an external drilling fluid additional mass coefficient is derived considering the dynamic pressure effect caused by external drilling fluid. Additional mass coefficient can get the result with high precision, which can meet the needs of the project. the simulation results are in good agreement with the test results, and the error is within 2 %. This work provides a useful attempt and lays the foundation for the dynamics of the drill string in the drilling fluid environment.

Drill String Vibrations Due to Intermittent Contact of Bit Teeth

1963 ◽  
Vol 85 (2) ◽  
pp. 187-194 ◽  
Author(s):  
P. R. Paslay ◽  
D. B. Bogy
Keyword(s):  
Experimental Data ◽  
Penetration Rate ◽  
Drill String ◽  
String Vibrations ◽  
Order Of Magnitude ◽  
Intermittent Contact ◽  
Maximum Penetration ◽  
Sufficient Magnitude ◽  
Force Excitation ◽  
Practical Measurement

An analysis of the longitudinal forces and the resulting longitudinal motions of an idealized drill string is presented. The only external force excitation considered occurs at the bit and is due to the intermittent contact of the teeth with the bottom of the hole. Attention has been restricted to the following two salient possibilities: 1 - Excitation at the bit may develop oscillating forces at the bit with amplitudes of the same order of magnitude as those of the bit load. 2 - Appreciable bit load variation may be detected by instruments which measure the motion of the drill string near its top. The first possibility is important if maximum penetration rate is to be achieved, and the second possibility is important in implementing practical measurement of the phenomenon. From the results of the specific example considered in this report, it is concluded that possibilities 1 and 2 may occur in sufficient magnitude to be influential, but experimental data on the actual bit motion and the damping will be required to evaluate the effect. The analysis is presented in such form that the influence of the various parts of the system can easily be evaluated.

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