Drilling Scenarios Research Articles

Experimental investigation on high voltage electric pulse rock breaking under drilling mud conditions

High voltage electric pulse rock breaking technology is a novel and promising rock breaking technique that is environmentally friendly, efficient, and nearing industrial application. However, the drilling performance of electrode bits under varied drilling muds and the mechanism of high voltage electric pulse rock breaking remain unclear. This study entails real drilling experiments conducted on red sandstone using electrical pulse drilling (EPD) under different initial voltage peaks, electrode bits, and drilling muds to investigate the impact and mechanism of EPD. A laboratory experimental system for high voltage pulse rock breaking is established based on a 0–80 kV EPD pulse generator. Three types of electrode bits are devised, namely, petal-structural, four-point-structural, and circular-ring-structural electrode bits. The EPD experiments on red sandstone are executed under seven different drilling muds at initial peak voltages ranging from 13 to 17 kV. And the efficiency of EPD rock breaking is assessed using five quantitative indexes: rate of penetration, breaking volume, specific energy of rock breaking, and the proportion of electrical fragmentation and hydraulic-electric rock fragmentation. Furthermore, the physical parameters, i.e., density, conductivity, Zeta potential, PH, and apparent viscosity, of the seven drilling muds are measured, shedding light on the rock breaking mechanism of EPD under specific drilling mud conditions. Subsequently, the designed electrode bit is evaluated, and based on experimental phenomenon, structural optimizations of the electrode bit and EPD drilling recommendations under various drilling mud conditions in real drilling scenarios are proposed. This research is poised to offer valuable insights into the design of EPD electrode bits and the selection of drilling mud for enhancing drilling efficiency.

Structuring and Recommendations for Research on the Construction of Intelligent Multi-Industry and Multihazard Emergency Planning Systems

During production and operation, enterprises are faced with occurrences of production accidents. One of the prerequisites for enterprises to achieve sustainable development is building an intelligent emergency command platform. To establish a scientific and advanced emergency management information system and address the challenges related to managing emergency plans to ensure production safety, such as ambiguous roles and responsibilities, inefficient application processes, independent resources, and slow responses by enterprises with multiple types of operations and disasters, an intelligent emergency command platform was built for multiple types of operations and disasters, and this platform was extended to include rescue steps. The structure and digital management of emergency plans under multiple coupled disasters and multipoint cogeneration were determined. Similar emergency plans were automatically recommended by crawler technology and an SVM algorithm based on a public information data lake, and the effectiveness of the plans was evaluated via a fuzzy analytic hierarchy process to promote the preparation of more efficient and scientific emergency plans. Finally, the analysis of pipeline leakage and emergency drill scenarios proved that the system is scientific and reliable. The results are of great significance for improving the deep integration of modern emergency-related information technology and emergency management businesses, promoting institutional and mechanical innovation, to provide a reference for other multibusiness enterprises, wchih can also be integrated into methods for urban safety and rescue.

Evacuation of a Paediatric Hospital Ward in Italy: Lessons Learnt From an Announced Evacuation Drill

The process of evacuating a hospital ward is a complex task that involves several challenges related to emergency protocols, such as the need for assisted evacuation, the staff/patient ratio, and the functional limitations of patients. The purpose of this work is to present a possible sequence of events that can take place during an evacuation drill in a paediatric hospital ward. This is deemed to provide guidance in performing such type of drills and investigate assisted evacuation timelines. The drill was conducted inside a paediatric ward in Italy, at that time closed for maintenance, with the help of figurants emulating paediatric patients. The medical personnel were the ones normally working inside the facility. The activity was video recorded and summarised in a written report. This allowed the analysis of the drill and the reconstruction of typical set of events and timelines that take place in such type of evacuation drill scenarios.

An Analysis of Drilling Projection Uncertainty and Implications for Collision Avoidance Management Systems

Summary During well planning, specifying the separation that must be maintained from offset wellbores is critical to ensuring safe operations. Recent efforts on API RP 78, an upcoming American Petroleum Institute recommended practice for wellbore placement, have provided guidelines for calculating safe separation distances and engineering considerations for those calculations. A major milestone was the publication of a separation rule (Sawaryn et al. 2019) standardizing a formula for separation factor (SF), which in turn defines the minimum allowable separation distance (MASD) between two wellbores and the allowable deviation from plan (ADP) for a wellbore being drilled. One element of this formula, σpa, describes the accuracy with which a future wellpath can be predicted. Prior guidance provides a suggested value for σpa (1.6 ft or 0.5 m at 1-sigma) based on heuristics. A more rigorous approach for estimating this value is presented, where the design of the drilling program can be considered. A framework is proposed for modeling deviation from a projected path using a planned trajectory, bottomhole assembly (BHA) properties, and survey practices. The method identifies where a deviation is detected through survey measurements and estimates a planned recovery operation. Equations are provided for estimating the distance from plan at deviation detection along with the maximum expected deviation during recovery. Common drilling scenarios are analyzed for sensitivity to operational parameters such as survey course length, sensor offset, tool face control, and BHA performance. The impact of varying σpa is explored across prototypical collision avoidance cases. A discussion of the relationships between the σpa value and the common collision avoidance calculations, such as SF, MASD, and ADP, is included along with considerations for the design of a risk management policy. Survey course length, survey sensor offset, and uncertainty in directional performance are all shown to have a significant impact on the potential maximum deviation from plan. An additional factor considered is the aggressiveness expected when performing recovery operations. An analysis of common drilling scenarios suggests the previously provided guidance of 1.6 ft at 1-sigma appears suitable for cases where the directional behavior of the BHA is well characterized and the combination of course length and survey sensor offset is kept to 150 ft or less. Longer survey course lengths, larger sensor offsets, or uncertainty in directional performance of the BHA can produce larger σpa values, in some scenarios causing a significant impact on the MASD and ADP. Previous work has called attention to the uncertainty in drilling to a projection, but up to now, there has not been a rigorous method for estimating that quantity. With the methods outlined in this paper, well planners and drilling engineers can make more informed decisions on how to ensure safe separation practices in their own operations.

Research on adaptive prediction model of rate of penetration under dynamic formation conditions

Rate of Penetration (ROP) prediction is a crucial for optimizing drilling processes and enhancing drilling efficiency. However, most existing ROP prediction models are static, relying on fixed neighboring well datasets and incapable of adapting to real-time changes in formation conditions during drilling. The dynamic and uncertain nature of geological conditions and formation heterogeneity further limits the extension and application of current ROP prediction models to target wells. To address these challenges, this study introduces an Adaptive Random Forest (ARF) algorithm to establish an ROP adaptive prediction model under dynamic formation conditions during real-time drilling operations. The performance of the ARF model is compared with the Moving-Window Random Forest (MW-RF) ROP dynamic prediction model, using data from the W1 well in the Sichuan basin as an example. Experimental results demonstrate that the ARF model outperforms the MW-RF model, exhibiting smaller overall error and reduced error fluctuation during formation condition changes. The ARF model's dynamic adaptability allows it to respond to the evolving trends of the ROP prediction model, rapidly adjusting to changes in formation conditions based on real-time drilling data flow. In contrast, the MW-RF model exhibits slower adaptability and delays in updating, reacting passively to window movements. The proposed ARF model overcomes limitations associated with static ROP prediction models, making it applicable to practical drilling scenarios and providing a theoretical foundation for real-time drilling parameter optimization and intelligent drilling strategies.

Estimating the anisotropy of the vertical transverse isotropy coal seam by rock physics model–based inversion

AbstractCoal seams exhibiting nearly horizontal bedding, and fractures can be characterized as transversely isotropic media with a vertical axis of symmetry, known as vertical transverse isotropy coal seams. The resulting anisotropy cannot be overlooked in high‐precision seismic velocity analysis, migration imaging and pre‐stack inversion. Therefore, we estimate the anisotropy of the vertical transverse isotropy coal seam (using the anisotropic Thomsen's parameters ε, γ and δ) by inverting the horizontal P‐ and SH‐wave velocities and fracture density based on a rock physics model. The Mori–Tanaka model and Brown–Korringa formula were first used to quantify the anisotropy of the vertical transverse isotropy coal seams impacted by dry and fluid‐saturated fractures. Subsequently, we formulated an equation for the inversion of horizontal P‐ and SH‐wave velocities, considering the measured vertical P‐ and SH‐wave velocities as constrained parameters. This approach is generally applied in vertical drilling scenarios. We tested the inversion method using the ultrasonic test results of coal samples collected from the southern margin of the Qinshui Basin, China and then used it on the full waveform logging data from a vertical coalbed methane well. Both the inversion results of horizontal P‐ and SH‐wave velocities and the estimated anisotropic parameters (ε and γ) were in good agreement with the ultrasonic test results of coal samples, although the accuracy of δ was slightly lower. Therefore, we believe that the proposed method can be extended to estimate the anisotropy of vertical transverse isotropy medium (assuming suitable rock physics models) for the ultrasonic testing of rock samples and full waveform logging along the vertical direction in near‐horizontal formations.

Impact of Pressure and Temperature on Foam Behavior for Enhanced Underbalanced Drilling Operations.

Foam, a versatile underbalanced drilling fluid, shows potential for improving the drilling efficiency and reducing formation damage. However, the existing literature lacks insight into foam behavior under high-pH drilling conditions. This study introduces a novel approach using synthesized seawater, replacing the conventional use of freshwater on-site for the foaming system's liquid base. This approach is in line with sustainability objectives and offers novel perspectives on foam stability under high-pH conditions. Experiments, conducted with a high-pressure, high-temperature (HPHT) foam analyzer, investigate how pressure and temperature affect foam properties. The biodegradable foaming agent ammonium alcohol ether sulfate (AAES) is employed. Results demonstrate that the pressure significantly impacts foam stability. Increasing pressure enhances stability, reducing decay rates and promoting uniform bubble sizes, especially at lower temperatures. This highlights foam's capacity to withstand high-pressure conditions. Conversely, the temperature plays a substantial role in foam decay, particularly at elevated temperatures (75 and 90 °C). Decreased liquid viscosity accelerates the liquid drainage and foam decay. While pressure mainly influences the AAES foam stability at temperatures up to 50 °C, temperature becomes the dominant factor at higher temperatures. Temperature's impact on foamability is minimal under constant pressure, maintaining consistent gas volume for maximum foam height. However, foam stability is sensitive to temperature variations, with increasing temperature leading to a more significant bubble size increase gradient. These findings stress the importance of considering temperature effects in foam drilling, particularly in deep and high-temperature environments. AAES foam exhibits stability at lower temperatures, making it suitable for surface and intermediate drilling. Understanding temperature-induced changes in foam structure and bubble size is essential for optimizing performance in high-temperature and deep drilling scenarios.

An efficient drilling conditions classification method utilizing encoder and improved Graph Attention Networks

Identification of drilling conditions is paramount for ensuring safety and efficiency in drilling operations. Traditional methods, often based on manual analysis of drilling parameters and patterns by experts using empirical formulas, typically lack speed and precision in modern drilling procedures. To address this shortcoming, we have developed a sophisticated classification methodology that combines Encoder layers with improved Graph Attention Networks (GAT), aiming to precisely discern seven prevalent drilling conditions. Using an advanced expert empirical decision tree, we achieved superior accuracy in our dataset annotations. The model’s architecture integrates the K-nearest neighbors (KNN) algorithm for seamless integration between the Encoder layer and GAT networks. Sensitivity analyses pinpoint optimal feature parameters, leading to significant enhancements in model accuracy. Experimental outcomes show our annotation approach surpasses traditional techniques by 15.24%, achieving an accuracy of 96.73%. Additionally, our model boasts a recall rate of 94.22%, indicating high reliability in correctly identifying true positive drilling conditions, which is crucial for operational safety and decision-making in drilling scenarios. Characterized by its real-time capabilities, precision, and scalability, our model demonstrates promising potential for applications in practical drilling scenarios.

Coupled drillstring dynamics modeling using 3D field-consistent corotational beam elements

Drilling is essential to extract subsurface hydrocarbons and geothermal energy, or store waste fluids/gases underground. Drilling efficiency directly affects the economics of well construction, and is to a large extent determined by the non-productive time (NPT) associated with downhole tool failure, bit wear/damage, unexpected drillstring vibrations, and insufficient surface-to-bottom energy transfer. Various models have been developed since the 1960s to understand and mitigate undesired drilling system oscillations to ensure efficient drilling operations and help optimize the well design. Significant recent advancements in drilling engineering technology, sensor development, and data science make it possible to develop and apply a faster and more comprehensive drilling system dynamic model that can be used for real-time drilling optimization and automation.In this study, a novel control-oriented physic-based drillstring dynamic modeling framework is developed using 3D field-consistent corotational beam elements with an updated Lagrangian formulation. The structure and element kinematics are firstly derived in global and local coordinate systems respectively, based on which the system dynamics are formulated by integrating the element stiffness, damping, and mass matrices. Different drilling boundary conditions and forms of external loads, including bit-rock interaction, wellbore-drillstring contact, stabilizers, bottom hole assembly (BHA) eccentricities, and gravity/buoyancy are defined within the modeling framework. The numerical accuracy of the model with linear/quintic beam elements is discussed and verified in four different static/dynamic loading cases, which are typically used for beam analysis. Simulations of different drilling scenarios, including dynamics during the pipe connection process, bit on/off bottom process, and pipe rocking during slide drilling, are conducted for an actual L-shape well configuration with comparison to field data. The simulated drillstring tri-axial vibrations exhibit diverse characteristics and patterns in terms of oscillation amplitudes, frequencies, and modes at varying depths, generating valuable understanding of potential drilling dysfunctions and insights for real-time drilling optimization and automation.

Model complexity reduction and controller design for managed pressure drilling automation

Automation of Managed Pressure Drilling (MPD) allows for fast and accurate pressure control in drilling operations. The achievable performance in automated MPD with model-based controllers is determined by the controller and, indirectly, also by the hydraulics model used for controller synthesis. On the one hand, such a hydraulics model should accurately capture essential flow dynamics of the system such as, e.g., wave propagation effects, for which typically complex models are needed. On the other hand, a suitable model should be simple enough to facilitate high-performance controller design as well as to support fast simulation studies supporting well scenario analysis. This paper shows that low-order models in terms of delay differential equations can effectively meet these requirements. Moreover, we propose a data-based model reduction technique to construct these low-order delay models. Next, based on this reduced-complexity model, a novel controller is designed to regulate the downhole pressure. Simulation results confirm that this controller outperforms existing pressure controllers in realistic drilling scenarios related to the mitigation of liquid kicks and mud losses encountered when drilling into high- or low-pressure zones.

Modeling demonstrates minimal ecological risks of cuttings discharges associated to oil and gas drilling with deep water wells

To assess the impacts of drill cutting discharges in the Gulf of Mexico, a particle dispersion modeling study was conducted on hypothetical drilling scenarios. The goal was to assess cumulative seabed deposition, and potential hydrocarbon loading from non-aqueous drilling fluids (NADF). Cuttings drilled with NADF showed to have minimal impact on local fauna at the deep-water well simulated. A hypothetical drill site was modeled under 3 different seasonally representative met-ocean conditions. The site is located approximately 260 km from the coast in water roughly 3500 meters (m) deep. Cumulative deposition was assessed for all materials released, whereas hydrocarbon loading was assessed based on the potential for NADF fluids to be retained on cuttings. Smothering effects on the benthic community are not anticipated. Hydrocarbon deposition was also very limited, ≤165 ppm of TPH. Overall, the cuttings drilled with NADF are predicted to have minimal impact on local fauna.

Risk-Controlled Wellbore Stability Criterion Based on a Machine-Learning-Assisted Finite-Element Model

Summary In certain drilling scenarios, the mud weight required to completely prevent wellbore enlargement can be impractically high. In such cases, what is known as risk-controlled wellbore stability criterion is introduced. This criterion allows for a certain and manageable level of wellbore enlargements to take place. Conventionally, the allowable level of wellbore enlargements in this type of model has always been based on the magnitude of the breakout angle. However, wellbore enlargements, as seen in caliper and image logs, can be highly irregular in terms of their distribution around the wellbore. This means that risk controlling wellbore stability through the breakout angle parameter can be insufficient. Instead, the total volume of cavings is introduced as the risk-control parameter. Unlike the breakout angle, the total volume of cavings can be coupled with a suitable hydraulics model to determine the threshold of manageable enlargement. The volume of cavings is determined using a machine-learning (ML)-assisted 3D elastoplastic finite-element model (FEM). The model implementation is first validated through experimental data. Next, a full data set from offset wells is used to populate and train the model. The trained model is then used to produce estimations of risk-controlled stability mud weights for different drilling scenarios. The model results are compared against those produced by conventional methods. Finally, both the FEM-ML model and the conventional method's results are compared against the drilling experience of the offset wells. The results illustrate how this methodology provides a more comprehensive and new solution to risk controlling wellbore stability.

Drilling Force Characterization during Inconel 718 Drilling: A Comparative Study between Numerical and Analytical Approaches.

In drilling operations, cutting forces are one of the major machinability indicators that contribute significantly towards the deviations in workpiece form and surface tolerances. The ability to predict and model forces in such operations is also essential as the cutting forces play a key role in the induced vibrations and wear on the cutting tool. More specifically, Inconel 718—a nickel-based super alloy that is primarily used in the construction of jet engine turbines, nuclear reactors, submarines and steam power plants—is the workpiece material used in the work presented here. In this study, both mechanistic and finite element models were developed. The finite element model uses the power law that has the ability to incorporate strain hardening, strain rate sensitivity as well as thermal softening phenomena in the workpiece materials. The model was validated by comparing it against an analytical mechanistic model that considers the three drilling stages associated with the drilling operation on a workpiece containing a pilot hole. Both analytical and FE models were compared and the results were found to be in good agreement at different cutting speeds and feed rates. Comparing the average forces of stage II and stage III of the two approaches revealed a discrepancy of 11% and 7% at most. This study can be utilized in various virtual drilling scenarios to investigate the influence of different process and geometric parameters.

Application of the electric resistance tomographic technique to investigate its efficacy in cuttings transport in horizontal drilling scenarios

The present study is focused on the experimental evaluation of the non-intrusive electric resistance tomographic (ERT) technique in the presence of different types of water-based drilling fluids, i.e., Newtonian (water) and non-Newtonian (0.05 wt% and 0.1 wt% polymers). The experiments were conducted in a 6.16-m long horizontal flow loop with an inner and outer diameter of 2.5 and 4.5 inches. The tests covered a variety of hydrodynamic and operational parameters, such as the density (997–1001 kg/m3) and apparent viscosity (0.889–2.54 cP) of the fluids as well as different eccentric conditions (0–0.6), mass flow rates (170–365 kg/min), and drill pipe rotations (0–120 RPM) with horizontal drilling conditions. In this investigation, we analyzed the ERT-obtained average volume fraction (AVF), maximum volume fraction (MVF), and cuttings residence time. The results highlighted that the ERT technique is useful in situ tool for detecting solid particles in various cuttings transport scenarios (different drilling fluids, mass flow rates, and eccentricities). The findings also revealed that an increase in the liquid flow rate influenced cuttings transport. Non-Newtonian fluids performed relatively better than Newtonian (water) fluid at higher flow rates (for equivalent pump output and equivalent Reynold number conditions) as it provides higher AVF and MVF quantities due to their rheological properties hold cuttings in a suspended form. Inner pipe rotations also significantly enhanced the cuttings transport by adding induced helical motion and vorticities in the annulus. On the other hand, eccentricity in the annulus caused hindrance in the cuttings transport movement due to reduced active solid transportation or effective area, resulting in a more extended horizontal bed formation.

노인과 장애인 거주시설의 화재안전 계획 및 피난 훈련 연구

Assistive hospital facilities and residential facilities for the elderly and the disabled, it is important to develop fire safety requirements and assure safety and health of their residents. It is necessary to develop fire or emergency drill scenarios which describe various types of emergency events implying architectural layout, escape routes, preventive equipment, behavioral considerations of users and staffs for fire safety plan. The purpose of this study is to investigate fire preventive actions in elderly assistive hospital facilities and the residential facilities for the disabled, to identify barriers and difficulties in planning and implement fire/emergency drills in those facilities, and to suggest improvement for faire safety planning. For this study, questionnaires were distributed and collected through online and offline. A total of 260 questionnaires were collected and analyzed using SPSS 25. Employees in residential facilities for the disabled addressed difficulties in assisting the disabled residents to escape because of communication problems, their lack of awareness of emergent situation, and facility conditions. Although employees appeal more staff for emergent events, it is not feasible to have affluent staff members for emergency preparedness especially for night time. For the vulnerable people to fire or other type of disasters, facilities should have appropriate and adjacent escape areas for each floor, fire preventive materials and finish, and other fire detective and suppressive system devices. It is suggested that fire drill scenarios need to include various conditions such as architectural settings, user characteristics instead of an identical manual and to have educational and training materials for employees to understand their physical environment setting for escape route and risk management.

Physics-Based Rate of the Penetration Prediction Model for Fixed Cutter Drill Bits

Abstract The drilling process is one of the most important and expensive aspects of the oil and gas industry. Its economic feasibility is a direct relation to good planning that has high dependence on an accurate prediction of the rate of penetration (ROP). Knowledge of drilling performance through ROP prediction models is a vital tool in the development of a consistent drilling plan and allows industry players to anticipate issues that may occur during a drilling operation. Additionally, as some drilling parameters (such as rotary speed, weight on bit (WOB), and drilling fluid flowrate), an accurate prediction of the ROP is crucial to the optimization of drilling performance and contributes to reducing drilling costs. Several approaches to predict the drilling performance have been tried with varying degrees of success, complexity, and accuracy. In this paper, a review of the history of drilling performance prediction is conducted with emphasis on rotary drilling with fixed cutter drill bits. The approaches are grouped into two categories: physics-based and data-driven models. The paper’s main objective is to present an accurate model to predict the drilling performance of fixed cutter drill bits including the founder point location. This model was based on a physics-based approach due to its low complexity and good accuracy. This development is based on a quantitative analysis of drilling performance data produced by laboratory experiments. Additionally, the validation and applicability tests for the proposed model are discussed based on drill-off tests (DOTs) and field trials in several different drilling scenarios. The proposed model presented high accuracy to predict the fixed cutter drill bit drilling performance in the 27 different drilling scenarios which were analyzed in this paper.

Insights into Enhanced Repeatability of Femtosecond Laser-Induced Plasmas.

Repeatability is of utmost importance as it is directly linked to measurement accuracy and precision of a technique and affects its cost, utility, and commercialization. The present paper contributes to explain enhanced repeatability of the femtosecond laser-induced breakdown spectroscopy (fs-LIBS) technique, remarkably significant for its industrial applications and instrumental size reduction. A fs-laser with 7 mJ pulse energy was focused to create a transient titanium plasma, and a high-resolution spectrometer was used to study time-resolved spectra and single-shot drilling sampling repeatability. Time-resolved spectroscopy study at a delay time interval of 0–1600 ns showed 200–400 ns as the optimum delay time zone for data acquisition with 2–4% line intensity RSDs. Plasma temperature RSDs were <1.8% for the investigated delay interval and reached 0.5% at 200 ns where the temperature recorded a maximum value of 22,000 K. Electron density reached 5.7 × 1017 cm–3 at 200 ns, and RSDs were <3% with the least fluctuation of 0.7%. Shot-to-shot RSDs were 3.5–5% at 15–30 drilling shot intervals for line intensities, <2% for plasma temperature, and <6.5% for electron density. Using an uncertainty propagation formula, total number density RSDs were calculated to be 1.9–5.3% for 50 single-shot drilling scenarios. Considering physics behind results, fs-plasmas are “stable ablation sources” due to their electrostatic formation mechanisms and confined hydrodynamic evolution. The fs-laser opens up new directions for LIBS applications where accuracy is significantly enhanced.

A discussion on the decoupling assumption of axial and torsional dynamics in bit-rock models

A common strategy for analyzing the stability of coupled axial and torsional dynamics in drilling is by using a two-degree-of-freedom mass-spring-damper model derived as a second-order ordinary differential equation. This implies using a single point mass to represent the inertia of the bottom-hole assembly and thus the characteristics of an otherwise distributed system. For the bit-rock model developed in Richard et al. (2007), the stability characteristics of the drilling system are in many previous works derived by assuming that the axial dynamics can be decoupled from the slower torsional dynamics. Using this bit-rock model, the friction forces and torques in the system are dependent on a time-delay term, dictating the stability of the system. Consequently, a set of critical drilling parameters, i.e., rotation speed, drill string stiffness, and fluid damping, can be investigated to identify the properties of the equilibrium for the nominal solution.In this paper, we have generalized the drill string dynamics by modeling the drill string as a series of alternating springs and point masses. By making the same assumptions as in previous works, the dynamics are derived as a lumped-multi-element second-order model including a time-delay dependent on the system states. The model is then defined as a state-dependent delay differential equation. The stability analysis of the decoupled generalized system indicates that the stable region for the chosen drilling parameters reduces and is trending towards zero when the number of model elements increases. The implication of this is that the nonlinearity of the coupled axial and torsional dynamics is required for a thorough understanding of the stability of the drilling system. Furthermore, we have performed a numerical analysis of the coupled dynamics by simulating relevant drilling scenarios.

Numerical Modeling of Unfavorable CFA Pile Drilling Conditions

Drilling and installation of deep foundations typically alter and affect surrounding soils and subsequently affect the adjacent structures. Possible effects on the adjacent structures due to the installation of driven piles have been thoroughly investigated in the literature. However, little attention has been given to other pile installation techniques such as continuous flight auger (CFA). In this paper, unfavorable CFA drilling conditions are discussed and investigated using three-dimensional (3D) finite element analyses. The induced settlements around the piles are calculated to assess the possible adverse effects on surrounding structures. The numerical models are validated using laboratory physical modeling of unfavorable soil drilling conditions reported in the literature. The analyses showed that unfavorable drilling conditions might have a major effect on adjacent structures up to two times the pile length. Parametric numerical modeling has also been conducted to study the influence of different parameters such as soil shear strength parameters, pile length, pile diameter, and soil permeability on the deformation adjacent to CFA pile during construction. The results revealed that soil relative density and permeability have a significant influence on the calculated surface settlement. Finally, several pile group drilling scenarios were investigated to gain insight into the optimum scenario for pile drilling. The analyses show that alternating between drilling piles near the structure and those far from it, may significantly reduce the surface settlement during pile construction.

Mitigation of Torsional Vibrations in Drilling Systems using Adaptive Nonlinear Control System

The reason for this work is to plan a robust yield feedback control way to deal with dispense with torque stick-slip vibrations in boring frameworks. Current industry controllers generally neglect to dispose of stick-slip vibrations, particularly when different torque flex modes assume a job in maniacal assault. In terms of build controller production, a real training-string system performs a multi-level model work such as torque mechanics. The proposed controller design is artfully distorted at optimizing the stability with respect to the uncertainty of the nonlinear bit-rock interaction. Based on heroes and intentions. Besides, a closed loop strength examination of the nonlinear preparing string model is displayed. This controller structure system offers a few points of interest contrasted with existing controllers. To begin with, just surface estimations are utilized, barring the requirement for entire estimations underneath it. Second, multi-level training-string dynamics are effectively handled in ways to access state-training controllers. Third, stability is explicitly provided with respect to bit-rock contact uncertainty and closed-loop performance specifications include controller design. The results of the study report confirm that stick-slip vibrations are actually eliminated in realistic drilling scenarios using a controller designed to achieve this state-of-control control.