The Effects of Drilling Mud and Weight Bit on Stability and Vibration of a Drill String

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Ali Asghar Jafari ◽  
Reza Kazemi ◽  
Mohammad Faraji Mahyari
Keyword(s):  
Angular Velocity ◽  
Flow Rate ◽  
Natural Frequencies ◽  
Drill String ◽  
Vibrational Amplitude ◽  
Drilling Process ◽  
Drilling Mud ◽  
Non Linear ◽  
Weight On Bit ◽  
Mud Flow

The main goal of this research is to analyze the effects of drilling mud flow rate, drill string weight, weight on bit and angular velocity on stability and vibration of a drill string. To this end, kinetic and potential energies of a rotating drill string are written while axial and lateral vibrations are considered. The effects of the drill string’s weight, weight on bit and geometrical shortening are considered in the model. Drilling mud’s effects are modeled by the Paidoussis formulations. The finite element method is employed to discrete the formulations. The stabilizers are modeled by dropping the coincided nodes. Linear (Flutter method) and non-linear methods are employed to analyze a drill string’s stability for different weight on a bit, angular velocity, drilling mud flow rate and numbers and arrangements of stabilizers. These results represent the significant effects of non-linear terms. Also, the effects of drilling mud flow rate and weight on bit on the natural frequencies and time responses are illustrated. Increasing drilling mud flow rate causes decreasing of natural frequencies and vibrational amplitude. Furthermore, increasing weight on bit leads to decreasing natural frequencies and increasing vibrational amplitude. These formulations can be used to choose the safest working conditions in the drilling process.

Real-Time Software to Estimate Friction Coefficient and Downhole Weight on Bit During Drilling of Horizontal Wells

2014 ◽  
Author(s):  
Mazeda Tahmeen ◽  
Geir Hareland ◽  
Bernt S. Aadnoy
Keyword(s):  
Friction Coefficient ◽  
Real Time ◽  
Information Transfer ◽  
Horizontal Wells ◽  
Drill String ◽  
Surface Measurement ◽  
Drilling Process ◽  
Drilling Data ◽  
Weight On Bit ◽  
Drag Analysis

The increasing complexity and higher drilling cost of horizontal wells demand extensive research on software development for the analysis of drilling data in real-time. In extended reach drilling, the downhole weight on bit (WOB) differs from the surface seen WOB (obtained from on an off bottom hookload difference reading) due to the friction caused by drill string movement and rotation in the wellbore. The torque and drag analysis module of a user-friendly real-time software, Intelligent Drilling Advisory system (IDAs) can estimate friction coefficient and the effective downhole WOB while drilling. IDAs uses a 3-dimensional wellbore friction model for the analysis. Based on this model the forces applied on a drill string element are buoyed weight, axial tension, friction force and normal force perpendicular to the contact surface of the wellbore. The industry standard protocol, WITSML (Wellsite Information Transfer Standard Markup Language) is used to conduct transfer of drilling data between IDAs and the onsite or remote WITSML drilling data server. IDAs retrieves real-time drilling data such as surface hookload, pump pressure, rotary RPM and surface WOB from the data servers. The survey data measurement for azimuth and inclination versus depth along with the retrieved drilling data, are used to do the analysis in different drilling modes, such as lowering or tripping in and drilling. For extensive analysis the software can investigate the sensitivity of friction coefficient and downhole WOB on user-defined drill string element lengths. The torque and drag analysis module, as well as the real-time software, IDAs has been successfully tested and verified with field data from horizontal wells drilled in Western Canada. In the lowering mode of drilling process, the software estimates the overall friction coefficient when the drill bit is off bottom. The downhole WOB estimated by the software is less than the surface measurement that the drillers used during drilling. The study revealed verification of the software by comparing the estimated downhole WOB with the downhole WOB recorded using a downhole measuring tool.

Field Verification of Model-Derived Natural Frequencies of a Drill String

2002 ◽  
Vol 124 (3) ◽  
pp. 154-162 ◽  
Author(s):  
Pushkar N. Jogi ◽  
John D. Macpherson ◽  
Michael Neubert
Keyword(s):  
Natural Frequencies ◽  
Drill String ◽  
Vibration Measurement ◽  
Premature Failure ◽  
Lateral Vibrations ◽  
Axial Acceleration ◽  
Weight On Bit ◽  
Measurement While Drilling ◽  
Actual Field ◽  
Downhole Measurements

Vibrations generated in a drill string while drilling generally lead to a reduction in drilling efficiency and often cause premature failure of drill string components and bit damage. It is also known that lateral vibrations, in particular, are responsible for most measurement-while-drilling (MWD) tool failures while drilling. One way to increase drilling efficiency and avoid tool damage is to monitor and analyze drilling vibrations so that drilling parameters can be adjusted while drilling to reduce such vibrations. An alternative method is to analyze and determine the natural frequencies of the bottom-hole assembly (BHA) so that resonant conditions caused by various excitation mechanisms in the drill string can be avoided. Even though models have been developed in the past in the drilling industry to determine the natural frequencies of a BHA, few attempts have been made to demonstrate that such models do actually help reduce vibrations or failures. This paper deals with the process of field validation of model-derived frequencies for axial, torsional and lateral vibrations. The results presented in this paper are based on the analysis of drilling data from a field test using downhole vibration measurement sensors. The downhole measurements included X and Y bending moments, axial acceleration, dynamic weight-on-bit, dynamic torque, and X and Y-axis magnetometers mounted in an MWD sub. The data analysis demonstrates that the natural frequencies predicted by the models match well with actual field (measured) values at the locations of interest, particularly for lateral vibrations. This analysis therefore shows that model derived results can be used with a degree of confidence to help avoid resonant conditions in a BHA while drilling and to help reduce failures.

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.

pH-Sensor Under Consideration for Multi-Sensor-Chip in Downhole Drilling Fluid Monitoring

2017 ◽  
Author(s):  
Jonathan Kühne ◽  
Frederic Güth ◽  
Heike Strauß ◽  
Yvonne Joseph ◽  
Pál Árki
Keyword(s):  
Optical Sensors ◽  
Drilling Fluid ◽  
Drill String ◽  
Glass Electrode ◽  
Drilling Fluids ◽  
Drilling Process ◽  
Ph Sensing ◽  
Drilling Mud ◽  
Ph Sensors ◽  
Drilling Muds

Modern drill strings for the exploration of oil and gas are equipped with a variety of sensor carrying devices such as Measurement While Drilling (MWD), Logging While Drilling (LWD), and Formation Testing While Drilling (FTWD). These devices generate a large amount of downhole data, such as the orientation of the well, drilling parameters e.g. weight on bit and torque, and formation properties. Appropriate telemetry systems are included in the drill string to transfer relevant downhole data in real time to the surface. Other data is stored in memories downhole for subsequent evaluation. However, drilling fluid properties are still monitored at the surface and their behavior under borehole conditions is predicted with hydraulic models. Commercial solutions for a direct downhole measurement of various drilling fluid parameters are rare, though they would increase drilling process safety and the knowledge about the behavior of drilling fluids under real bottomhole conditions. The pH has a significant influence on the properties of water-based muds and plays a role in the chemistry of oil-based muds as the water cut in the emulsion increases. Commercial pH-sensing devices, such as the glass electrode, and optical sensors are not appropriate for the pH measurement under bottomhole conditions. Fragility, the insufficient degree of miniaturization, the low temperature and pressure resistance due to the liquid reference electrolyte, and phenomena such as the alkaline error are certain drawbacks of glass electrodes. Often optical sensors often will not capture the whole pH scale and require the medium to be at least slightly transparent for light. The usage of pH-sensors based on EIS (electrolyte-isolator-semiconductor) structures is a possible application of chemical sensors for drilling fluid monitoring under in situ borehole conditions. This paper presents results from a study on the behavior of an EIS structure as a pH sensitive electrode measured vs. a commercial Ag/AgCl reference electrode in comparison with a commercial glass electrode. EIS structures are capacitive pH sensors where the sensing layer is generally a metal oxide on a semiconductor substrate. Measurements in basic drilling muds were conducted under constant temperature and atmospheric pressure while the drilling mud was steadily stirred. The mud was titrated from alkaline to acidic conditions with hydrochloric acid and the pH was measured after potential equilibration at the electrodes. The results show a general feasibility for the usage of the proposed sensor. There are still certain challenges to be overcome in the development of a robust and reliable pH-sensing device for complex fluids, such as drilling muds under high pressure/high temperature (HP/HT) conditions.

Stick-Slip and Bit-Bounce of Deep-Hole Drillstrings

2000 ◽  
Vol 122 (2) ◽  
pp. 78-82 ◽  
Author(s):  
A. Baumgart
Keyword(s):  
Angular Velocity ◽  
Nonlinear Differential Equations ◽  
Equations Of Motion ◽  
Hydraulic Pressure ◽  
Drilling Process ◽  
Initial Value ◽  
Stick Slip ◽  
Bottom Hole ◽  
Weight On Bit ◽  
Torque On Bit

A mathematical model for the drilling process is derived and solved numerically as an initial value problem. The equations of motion are nonlinear differential equations for longitudinal, lateral, and rotational motion of the pipe as well as for the rate of flow and pressure of the mud. The model comprises a mud (Moineau) motor which rotates the bit relative to the lower end of the pipe. The model accounts for buckling of the pipe due to excessive torque and longitudinal forces, as well as for the effect of hydraulic pressure on the deformed pipe. Weight on bit and torque on bit are computed from characteristic curves which are functions of the penetration of the bit into the rock and the angular velocity of the bit. Numerical simulations show self-excited oscillations of the drillstring, including bit take-off from the bottom hole and large amplitudes in the bit’s angular velocity. [S0195-0738(00)00602-6]

Vibratory Power Delivery to Rock During Rotary-Vibratory Drilling

1978 ◽  
Vol 100 (2) ◽  
pp. 179-187
Author(s):  
D. C. Ohanehi ◽  
L. D. Mitchell
Keyword(s):  
Complete System ◽  
Closed Form Solution ◽  
String Model ◽  
Element Model ◽  
Power Input ◽  
Drill String ◽  
Form Solution ◽  
Drilling Process ◽  
Drilling Mud ◽  
Mechanical Element

This paper outlines the theoretical description of the vibratory portion of the rotary-vibratory drilling process. A multiple mechanical element model is used to describe the drill string and rock-rock bit assembly. The drill string model has continuously distributed properties of mass, stiffness, and external drilling-mud damping. A closed form solution is developed using boundary condition matching at the end of each mechanical element. The solution is used to compute the power input to the system by a vibratory unit, the power delivered to the rock, and the power lost to the drilling mud through vibratory losses. From these data, efficiencies are computed. The analytical solution has been checked in parallel with a transfer matrix computer solution. The results are identical within computer precision. The analytical model is then applied to the study of the Drilling Research Incorporated (DRI) prototype drilling system and its test drilling parameters for the 1957 test drilling. Explanations of the limits of the increase in drilling rates to 2:1 are explored. The results are explored relative to the potential for increasing the drill penetration rates by system redesign. Conclusions are drawn concerning the most productive routes to be taken for rotary-vibratory drilling systems and for the vibratory driver. It has become clear that successful future downhole rotary-vibratory drilling rigs will require a complete system understanding, a complete system design, and a new concept in vibratory driver.

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 Non-Linear Dynamic Analysis of Drill String System with Fluid-Structure Interaction

2021 ◽  
Vol 11 (19) ◽  
pp. 9047
Author(s):  
Rongpeng Wang ◽  
Xiaoqin Liu ◽  
Guiqiu Song ◽  
Shihua Zhou
Keyword(s):  
Dynamic Characteristics ◽  
Chaotic Motion ◽  
Period Doubling ◽  
Drill String ◽  
Jump Discontinuity ◽  
Drilling Process ◽  
Prevention Measures ◽  
Fluid Structure ◽  
Non Linear ◽  
Effect Of Support

In this research, the non-linear dynamics of the drill string system model, considering the influence of fluid—structure coupling and the effect of support stiffness, are investigated. Using Galerkin’s method, the equation of motion is discretized into a second-order differential equation. On the basis of an improved mathematical model, numerical simulation is carried out using the Runge—Kutta integration method. The effects of parameters, such as forcing frequency, perturbation amplitude, mass ratio and flow velocity, on the dynamic characteristics of the drill string system are studied under different support stiffness coefficients, in which bifurcation diagrams, waveforms, phase diagrams and Poincaré maps of the system are provided. The results indicate that there are various dynamic model behaviors for different parameter excitations, such as periodic, quasi-periodic, chaotic motion and jump discontinuity. The system changes from chaotic motion to periodic motion through inverse period-doubling bifurcation, and the support stiffness has a significant influence on the dynamic response of the drill string system. Through in-depth study of this problem, the dynamic characteristics of the drill string can be better understood theoretically, so as to provide a necessary theoretical reference for prevention measures and a reduction in the number of drilling accidents, while facilitating the optimization of the drilling process, and provide basis for understanding the rich and complex nonlinear dynamic characteristics of the deep-hole drill string system. The study can provide further understanding of the vibration characteristics of the drill string system.

Observer-Based Boundary Control Design for the Suppression of Stick–Slip Oscillations in Drilling Systems With Only Surface Measurements

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Halil Ibrahim Basturk
Keyword(s):  
Differential Equation ◽  
Angular Velocity ◽  
Linear Time ◽  
Control Design ◽  
Drill String ◽  
Friction Torque ◽  
Distributed Model ◽  
Drilling Process ◽  
Stick Slip ◽  
Surface Measurements

We develop an observer-based boundary controller for the rotary table to suppress stick–slip oscillations and to maintain the angular velocity of the drill string at a desired value during a drilling process despite unknown friction torque and by using only surface measurements. The control design is based on a distributed model of the drill string. The obtained infinite dimensional model is converted to an ordinary differential equation–partial differential equation (ODE–PDE) coupled system. The observer-based controller is designed by reformulating the problem as the stabilization of an linear time-invariant (LTI) system which is affected by a constant unknown disturbance and has simultaneous actuator and sensor delays. The main contribution of the controller is that it requires only surface measurements. We prove that the equilibrium of the closed-loop system is exponentially stable, and that the angular velocity regulation is achieved with the estimations of unknown friction torque and drill bit velocity. The effectiveness of the controller is demonstrated using numerical simulations.

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