scholarly journals The Impact of Frictional Healing on Stick-Slip Recurrence Interval and Stress Drop: Implications for Earthquake Scaling

2017 ◽  
Vol 122 (12) ◽  
pp. 10,102-10,117 ◽  
Author(s):  
Kyungjae Im ◽  
Derek Elsworth ◽  
Chris Marone ◽  
John Leeman
Keyword(s):  
Stress Drop ◽  
Recurrence Interval ◽  
Stick Slip ◽  
Earthquake Scaling ◽  
The Impact

scholarly journals Kinematics and dynamics analysis of new rotary-percussive PDM drilling tool

2021 ◽  
pp. 146134842198915
Author(s):  
Jialin Tian ◽  
Xuehua Hu ◽  
Liming Dai ◽  
Lin Yang ◽  
Yi Yang ◽  
...  
Keyword(s):  
Drill String ◽  
Structure Design ◽  
Drilling Process ◽  
Analysis Model ◽  
Drilling Tool ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
Bottom Hole ◽  
Bottom Hole Assembly ◽  
The Impact

This paper presents a new drilling tool with multidirectional and controllable vibrations for enhancing the drilling rate of penetration and reducing the wellbore friction in complex well structure. Based on the structure design, the working mechanism is analyzed in downhole conditions. Then, combined with the impact theory and the drilling process, the theoretical models including the various impact forces are established. Also, to study the downhole performance, the bottom hole assembly dynamics characteristics in new condition are discussed. Moreover, to study the influence of key parameters on the impact force, the parabolic effect of the tool and the rebound of the drill string were considered, and the kinematics and mechanical properties of the new tool under working conditions were calculated. For the importance of the roller as a vibration generator, the displacement trajectory of the roller under different rotating speed and weight on bit was compared and analyzed. The reliable and accuracy of the theoretical model were verified by comparing the calculation results and experimental test results. The results show that the new design can produce a continuous and stable periodic impact. By adjusting the design parameter matching to the working condition, the bottom hole assembly with the new tool can improve the rate of penetration and reduce the wellbore friction or drilling stick-slip with benign vibration. The analysis model can also be used for a similar method or design just by changing the relative parameters. The research and results can provide references for enhancing drilling efficiency and safe production.

Stress Drop Derived from Spectral Analysis Considering the Hypocentral Depth in the Attenuation Model: Application to the Ridgecrest Region, California

2021 ◽  
Author(s):  
Dino Bindi ◽  
Hoby N. T. Razafindrakoto ◽  
Matteo Picozzi ◽  
Adrien Oth
Keyword(s):  
Stress Drop ◽  
Spectral Decomposition ◽  
Epicentral Distance ◽  
Source Parameters ◽  
S Wave ◽  
Qualitative Comparison ◽  
Ground Shaking ◽  
Attenuation Model ◽  
Hypocentral Distance ◽  
The Impact

ABSTRACT We investigate the impact of considering a depth-dependent attenuation model on source parameters assessed through a spectral decomposition. In particular, we evaluate the effect of considering the hypocentral depth as an additional variable for the attenuation model, using as the target the tendency of the average stress drop to increase with depth, as observed in recent studies. We analyze the Fourier spectra of S-wave windows for about 1900 earthquakes with a magnitude above 2.5 recorded in the Ridgecrest region, southern California. Two different parameterizations of the attenuation term are implemented in the spectral decomposition, either as a function of the hypocentral distance alone or as a function of both epicentral distance and depth. The comparison of the spectral attenuation curves shows that, although the hypocentral model describes, on average, the range of values spanned by the attenuation curve for different depths, systematic differences with distance, depth, and frequency are observed. These differences are transferred to the source spectra and, in turn, to the source parameters extracted from the best-fitting ω−2 models. In particular, stress drops for events deeper than 7 km are, on average, almost double even when depth is introduced explicitly in the attenuation model. The increase of stress drop with depth is confirmed also after accounting for the increase of the shear velocity with depth, which absorbs about 30%–40% of the total increase. Moreover, a qualitative comparison with a model for the gradient of the effective normal stress confirms the reliability of the observed trend. Finally, the coherent spatial patterns shown by a simplified 2D tomographic representation of the spectral residuals highlights the impact on ground-shaking variability of the lateral variability of the crustal attenuation properties in the region.

Resolving the Unique Invariant Slip-Direction in Rigid Three-Dimensional Multi-Point Impacts at Stick-Slip Transitions

2018 ◽  
Author(s):  
Abhishek Chatterjee ◽  
Alan Bowling
Keyword(s):  
Single Point ◽  
Three Dimensional ◽  
Impact Behavior ◽  
Slip Direction ◽  
Stick Slip ◽  
Impact Forces ◽  
Post Impact ◽  
Impact Problems ◽  
Slip Transition ◽  
The Impact

This work presents a new approach for resolving the unique invariant slip direction at Stick-Slip Transition during impact. The solution method presented in this work is applicable to both single-point and multi-point impact problems. The proposed method utilizes rigid body constraints to resolve the impact forces at all collision points in terms of a single independent impact forces parameter. This work also uses an energetic coefficient of restitution to terminate impact events, thereby yielding energetically consistent post-impact behavior.

scholarly journals Experimental Study on Axial Impact Mitigating Stick-Slip Vibration with a PDC Bit

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Yong Wang ◽  
Hongjian Ni ◽  
Yiliu (Paul) Tu ◽  
Ruihe Wang ◽  
Xueying Wang ◽  
...  
Keyword(s):  
Impact Force ◽  
Impact Load ◽  
Similarity Theory ◽  
Impact Frequency ◽  
Stick Slip ◽  
Axial Impact ◽  
Pdc Bit ◽  
Fluctuation Amplitude ◽  
Rotary Speed ◽  
The Impact

Stick-slip vibration reduces the drilling rate of penetration, causes early wear of bits, and threatens the safety of downhole tools. Therefore, it is necessary to study suppression methods of stick-slip vibration to achieve efficient and safe drilling. Field tests show that the use of downhole axial impactors is helpful to mitigate stick-slip vibration and improve rock-breaking efficiency. However, there are many deficiencies in the study of how axial impact load affects stick-slip vibration of a PDC bit. In this paper, based on the two-degrees-of-freedom spring-mass-damper model and similarity theory, a laboratory experiment device for suppressing stick-slip vibration of a PDC bit under axial impact load has been developed, and systematic experimental research has been carried out. The results show that the axial impact force can suppress the stick-slip vibration by reducing the amplitude of weight on bit and torque fluctuations and by increasing the main frequency of torque. The amplitude of impact force affects the choice of the optimal back-rake angle. The impact frequency is negatively correlated with the fluctuation amplitude of the rotary speed. When the impact frequency is greater than 100 Hz, the fluctuation amplitude of the rotary speed will not decrease.

Characteristics of earthquake sequences: comparison from 0D to 3D

2021 ◽  
Author(s):  
Meng Li ◽  
Casper Pranger ◽  
Ylona van Dinther
Keyword(s):  
Stress Drop ◽  
Dynamic Models ◽  
Numerical Models ◽  
Recurrence Interval ◽  
Staggered Grid ◽  
Earthquake Parameters ◽  
Higher Dimensional ◽  
Dimensional Models ◽  
As Stress ◽  
Earthquake Sequences

<p>Numerical models are well-suited to overcome limited spatial-temporal observations to understand earthquake sequences, which is fundamental to ultimately better assess seismic hazard. However, high-resolution numerical models in 3D are computationally time and memory consuming. This is not optimal if the aspects of lateral or depth variations within the results are not needed to answer a particular objective. In this study we quantify and summarize the limitations and advantages for simulating earthquake sequences in all spatial dimensions.</p><p> </p><p>We simulate earthquake sequences on a strike-slip fault with rate-and-state friction from 0D to 3D using both quasi-dynamic and fully dynamic approaches. This cross-dimensional comparison is facilitated by our newly developed, flexible code library <em>Garnet</em>, which adopts a finite difference method with a fully staggered grid. We have validated our models using problems BP1-QD & FD and BP4-QD & FD of the SEAS (Sequences of Earthquakes and Aseismic Slip) benchmarks from the Southern California Earthquake Center.</p><p> </p><p>Our results demonstrate that lower-dimensional/quasi-dynamic models are qualitatively similar in terms of earthquake cycle characteristics to their higher-dimensional/fully-dynamic counterparts, while they could be hundreds to millions times faster at the same time. Quantitatively, we observe that certain earthquake parameters, such as stress drop and fracture energy release, can be accurately reproduced in each of these simpler models as well. However, higher dimensional models generally produce lower maximum slip velocities and hence longer coseismic durations. This is mainly due to lower rupture speeds, which result from increased energy consumption along added rupture front directions. In the long term, higher dimensional models produce shorter recurrence interval and hence smaller total slip, which is mainly caused by the higher interseismic stress loading rate inside the nucleation zone. The same trend is also observed when comparing quasi-dynamic models to fully dynamic ones. We extend a theoretical calculation that to first order approximates the aforementioned physical observables in 3D to all other dimensions. These theoretical considerations confirm the same trend as what is observed for stress drop, recurrence interval and total slip across dimensions. These findings on similarities and differences of different dimensional models and a corresponding quantification of computational efficiency can guide model design and facilitate result interpretation in future studies.</p>

scholarly journals Advanced Rainfall Trend Analysis of 117 Years over West Coast Plain and Hill Agro-Climatic Region of India

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1225
Author(s):  
Atul Saini ◽  
Netrananda Sahu ◽  
Pankaj Kumar ◽  
Sridhara Nayak ◽  
Weili Duan ◽  
...  
Keyword(s):  
Trend Analysis ◽  
West Coast ◽  
Winter Season ◽  
Recurrence Interval ◽  
Annual Rainfall ◽  
Rainfall Trend ◽  
Climatic Region ◽  
Monotonic Trend ◽  
Slope Test ◽  
The Impact

In this paper, the rainfall trend of the West Coast Plain and Hill Agro-Climatic Region is analyzed for 117 years (1901–2017). This region is a globally recognized biodiversity hotspot and known for one of the highest rainfall receiving regions in India. Rainfall grid dataset is used for the analysis of rainfall trends on monthly, seasonal, and decadal time scales. Modified Mann–Kendall’s test, Linear Regression, Innovative Trend Analysis, Sen’s Slope test, Weibull’s Recurrence Interval, Pearson’s Coefficient of Skewness, Consecutive Disparity Index, Kurtosis, and some other important statistical techniques are employed for trend analysis. Results indicate that the rainfall trend is significant in January, July, August, September as well as the Winter season. Among all the significant trends, January and July showed a decreasing rainfall trend. July has the highest contribution (30%) among all the obtained monotonic trend to annual rainfall and coincidentally has the highest trend magnitude. August and September months with a combined contribution of 30% to annual rainfall, show an increasing monotonic trend with high magnitude whereas Winter season shows a monotonic decreasing rainfall trend with comparatively low magnitudes. Decadal analysis along with the study of recurrence interval of excess and deficit years helps to understand the decadal rhythm of trend and the magnitude of extreme monthly and seasonal events. Skewness reveals that rainfall dataset of all the periodic results is right-skewed and the recurrence interval also supports the skewness results. Sharply decreasing rainfall in July and rising rainfall in August and September is predictive of the impact on agriculture, biodiversity and indicates the rainfall regime shift in the region.

scholarly journals Drillstring Failure: Analytical and Experimental Approach

2019 ◽  
Vol 300 ◽  
pp. 04004
Author(s):  
Edris Hassan ◽  
Jamil Abdo ◽  
Jan Kwak ◽  
Abdullah Al Shabibi
Keyword(s):  
Torsional Vibration ◽  
Oil And Gas ◽  
Drill Pipe ◽  
Oil And Gas Industry ◽  
Drill String ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Torsional Vibrations ◽  
Stick Slip ◽  
The Impact

Drilling is one of the costliest activities in oil and gas industry due to the complexity of interactions with downhole rock formation. Under such conditions, the uncertainty of drillstring behaviour increase and hence it becomes difficult to predict the causes, occurrences, and types of failures. Lateral and torsional vibrations often cause failure of Bottom Hole Assembly (BHA), drillstring failure, drill bit and wall borehole damages. In this work, a model is presented to determine the impact of lateral and torsional vibrations on a drillstring during the drilling operation. The model aims to mimic real drillstring behaviour inside a wellbore with regards to its dynamic movements due to multiple real situations such as eccentricity of collars, drill pipe sections, and stick-slip phenomena occurring due to the interaction of the bit and the drillstring with the well formation. The work aims to develop a basis for determining critical operating speeds and design parameters to provide safe drilling procedures and reduce drill string fatigue failure. Lagrangian approach is used in this study to attain drillstring lateral and torsional vibration coupling equations. The nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole lateral and torsional vibration modes. Parameters from the experimental investigations are incorporated for validation of the mathematical models and for prediction of the drillstring fatigue life. Such investigations are essential for oil and gas industries as they provide solutions and recommendations about operational speed, lateral and torsional amplitudes measurements and corrections, and the conditions for avoiding occurrence of natural frequencies of the system.

Modelling the source of glacial earthquakes for a better understanding of the impact of iceberg capsize on glacier stability

2020 ◽  
Author(s):  
Pauline Bonnet ◽  
Vladislav Yastrebov ◽  
Alban Leroyer ◽  
Patrick Queutey ◽  
Anne Mangeney ◽  
...  
Keyword(s):  
Mass Loss ◽  
Fluid Structure Interaction ◽  
Greenland Ice Sheet ◽  
Stick Slip ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Dynamic Mass ◽  
Glacier Terminus ◽  
Glacier Dynamics ◽  
The Impact

<p>One current concern in climate science is the estimations of the amount of ice loss by glaciers each year and the corresponding rate of sea level rise. Greenland ice sheet contribution is significant with about 30% to the global ice mass losses. Ice loss in Greenland is distributed approximately equally between loss in land by surface melting and loss at the front of marine-terminating glaciers that is modulated by dynamic processes. Dynamic mass loss includes both submarine melting and iceberg calving. The processes that control ablation at tidewater glacier termini, glacier retreat and calving are complex, setting the limits to the estimation of dynamic mass loss and the relation to glacier dynamics. It involves interactions between bedrock – glaciers – icebergs – ice-mélange – water – atmosphere. Moreover, the capsize of cubic kilometer scale icebergs close to a glacier front can destabilize the glacier, generate tsunami waves, and induce mixing of the water column which can impact both the local fauna and flora.</p><p>We aim to improve the understanding of iceberg capsize using a mechanical modeling of iceberg rotation against the glacier terminus, constrained by the generated seismic waves that are recorded at teleseismic distances. To achieve this objective, we develop a fluid-structure interaction model for the capsizing iceberg. Full scale fluid-structure interaction models enable accurate simulation of complex fluid flows in presence of rigid or deformable solids and in presence of free surfaces. However, such models are computationally very expensive. Therefore, our strategy is to construct a simple solid dynamics model involving contact and friction, whose simplified interaction with water is governed by parametrized forces and moments. We fine tune these parametrized effects on an iceberg capsizing in contact with a glacier with the help of reference direct numerical simulations of fluid-structure interactions involving full resolution of Navier-Stokes equations. We assess the sensitivity of the glacier dynamics to the glacier-bedrock friction law and the conditions for triggering a stick-slip motion of the glacier due to iceberg capsize. The seismogenic sources of the capsizing iceberg in contact with a glacier simulated with our model are then compared to the recorded seismic signals for well documented events.</p>

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