Improving fracture initiation and potential impact on fracture coverage by implementing optimal well-planning and drilling methods for typical stress conditions in the Cooper Basin, central Australia

2015 ◽  
Vol 55 (2) ◽  
pp. 403 ◽  
Author(s):  
Raymond Johnson ◽  
Hani Abul Khair ◽  
Rob Jeffrey ◽  
Jeremy Meyer ◽  
Carly Stark ◽  
...  
Keyword(s):  
Numerical Models ◽  
Model Development ◽  
High Stress ◽  
Fracture Initiation ◽  
Horizontal Stress ◽  
Complex Stress ◽  
Stress Conditions ◽  
Natural Fractures ◽  
Fracture Conductivity ◽  
Cooper Basin

Drilling conditions involving high mean and deviatory stresses, and natural fractures in the Cooper Basin present challenges in drilling and introduce wellbore rugosities, leaving a damaged wellbore subject to a stress cage effect. Fracture initiations have been problematic in vertical Cooper Basin wells, exhibiting high initiation and treating pressure frac treatments, and with high stress conditions posing greater risks in non-vertical completions. While far-field fracture complexity should be simplified, the near wellbore complexity results in reduced fracture conductivity. The authors believe that present drilling practices and wellbore azimuths may be contributing to sub-optimal hydraulic fracture initiations and complexities. Present analytical modelling methodologies can derive initiation pressures for circular wellbores, but require more complex numerical models to include flaws and ellipticity to represent natural fractures and wellbore rugosities. This study compares initiation pressures and presents graphical results, comparing circular and elliptical wellbore cases with flaws. This extended abstract outlines the criteria used in these models and remarks on areas needing further research and model development. The authors also propose improved drilling techniques to achieve more stable, smoother wellbores, potentially reducing some rugosity and drilling induced fractures. By using data from recent research and other cases with complex stress environments, it is proposed that initiation pressures might be reduced by inclining wells for hydraulic fracturing treatments in a favourable alignment in the maximum horizontal stress direction (σH-Max), and implementing completion techniques that aid better fracture initiation.

Rock Burst Analyse in Qirehataer Diversion Tunnel

2011 ◽  
Vol 138-139 ◽  
pp. 352-355
Author(s):  
Jian Feng Bian ◽  
Jian Jun Zhou ◽  
Guo Bin Zhao
Keyword(s):  
Rock Burst ◽  
High Stress ◽  
Horizontal Stress ◽  
Stress Conditions ◽  
Diversion Tunnel ◽  
Gneissic Granite ◽  
High Stress Concentration ◽  
Tunnel Section ◽  
The Right ◽  
Brittle Rock Mass

Rock burst is a geological hazard which occurs when hard and brittle rock mass is excavated under high in-situ stresses or high stress concentration. The Qirehataer diversion tunnel has 15.66 km long at a maximum depth of 1720 m. About 64.5% of the tunnel is located in gneissic granite. During excavation of the tunnel, light to moderate rock burst occurred in about 300 m length of the tunnel. This paper provides the analysis of the characteristics and stress conditions in the rock burst site using the stress conditions around the excavation, and provides an explanation on the reasons why rock burst occurred from the beginning to middle of the vault on the right side of the tunnel section, and the most serious situation is located at 60° with respect to horizontal. Stress release hole and bolt or bolt and net are used to prevent and manage rock burst which have been shown to be effective in this case.

Self-Injurious Behavior vs. Nonsuicidal Self-Injury

Crisis ◽  
2012 ◽  
Vol 33 (2) ◽  
pp. 106-112 ◽  
Author(s):  
Christopher M. Bloom ◽  
Shareen Holly ◽  
Adam M. P. Miller
Keyword(s):  
Positive Reinforcement ◽  
Empirical Investigation ◽  
High Stress ◽  
Animal Research ◽  
Stress Conditions ◽  
Human Populations ◽  
Pharmacological Interventions ◽  
Self Injury ◽  
Cns Stimulant ◽  
Nonsuicidal Self Injury

Background: Historically, the field of self-injury has distinguished between the behaviors exhibited among individuals with a developmental disability (self-injurious behaviors; SIB) and those present within a normative population (nonsuicidal self-injury; NSSI),which typically result as a response to perceived stress. More recently, however, conclusions about NSSI have been drawn from lines of animal research aimed at examining the neurobiological mechanisms of SIB. Despite some functional similarity between SIB and NSSI, no empirical investigation has provided precedent for the application of SIB-targeted animal research as justification for pharmacological interventions in populations demonstrating NSSI. Aims: The present study examined this question directly, by simulating an animal model of SIB in rodents injected with pemoline and systematically manipulating stress conditions in order to monitor rates of self-injury. Methods: Sham controls and experimental animals injected with pemoline (200 mg/kg) were assigned to either a low stress (discriminated positive reinforcement) or high stress (discriminated avoidance) group and compared on the dependent measures of self-inflicted injury prevalence and severity. Results: The manipulation of stress conditions did not impact the rate of self-injury demonstrated by the rats. The results do not support a model of stress-induced SIB in rodents. Conclusions: Current findings provide evidence for caution in the development of pharmacotherapies of NSSI in human populations based on CNS stimulant models. Theoretical implications are discussed with respect to antecedent factors such as preinjury arousal level and environmental stress.

A new ensemble-based statistical methodology to verify changes in weather and climate models

2021 ◽  
Author(s):  
Christian Zeman ◽  
Christoph Schär
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Numerical Models ◽  
Hypothesis Test ◽  
Model Development ◽  
Atmospheric Model ◽  
Statistical Hypothesis ◽  
Model Parameters ◽  
Rounding Errors ◽  
Weather And Climate

<p>Since their first operational application in the 1950s, atmospheric numerical models have become essential tools in weather and climate prediction. As such, they are a constant subject to changes, thanks to advances in computer systems, numerical methods, and the ever increasing knowledge about the atmosphere of Earth. Many of the changes in today's models relate to seemingly unsuspicious modifications, associated with minor code rearrangements, changes in hardware infrastructure, or software upgrades. Such changes are meant to preserve the model formulation, yet the verification of such changes is challenged by the chaotic nature of our atmosphere - any small change, even rounding errors, can have a big impact on individual simulations. Overall this represents a serious challenge to a consistent model development and maintenance framework.</p><p>Here we propose a new methodology for quantifying and verifying the impacts of minor atmospheric model changes, or its underlying hardware/software system, by using ensemble simulations in combination with a statistical hypothesis test. The methodology can assess effects of model changes on almost any output variable over time, and can also be used with different hypothesis tests.</p><p>We present first applications of the methodology with the regional weather and climate model COSMO. The changes considered include a major system upgrade of the supercomputer used, the change from double to single precision floating-point representation, changes in the update frequency of the lateral boundary conditions, and tiny changes to selected model parameters. While providing very robust results, the methodology also shows a large sensitivity to more significant model changes, making it a good candidate for an automated tool to guarantee model consistency in the development cycle.</p>

High Stress Contrast between Different Lithologies and its Implications for Drilling and Stimulation in the Northern Cooper Basin

2016 ◽  
Author(s):  
Feng Gui ◽  
Khalil Rahman ◽  
Duncan Lockhart ◽  
Diogo Cunha ◽  
Dylan Meadows
Keyword(s):  
High Stress ◽  
Stress Contrast ◽  
Cooper Basin

Predicting the azimuth of natural fractures and in-situ horizontal stress: A case study from Sichuan Basin, China

Geophysics ◽  
2021 ◽  
pp. 1-97
Author(s):  
kai lin ◽  
Bo Zhang ◽  
Jianjun Zhang ◽  
Huijing Fang ◽  
Kefeng Xi ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
Sichuan Basin ◽  
Horizontal Stress ◽  
Seismic Attributes ◽  
Seismic Events ◽  
Natural Fractures ◽  
Microseismic Data ◽  
Maximum Horizontal Stress

The azimuth of fractures and in-situ horizontal stress are important factors in planning horizontal wells and hydraulic fracturing for unconventional resources plays. The azimuth of natural fractures can be directly obtained by analyzing image logs. The azimuth of the maximum horizontal stress σH can be predicted by analyzing the induced fractures on image logs. The clustering of micro-seismic events can also be used to predict the azimuth of in-situ maximum horizontal stress. However, the azimuth of natural fractures and the in-situ maximum horizontal stress obtained from both image logs and micro-seismic events are limited to the wellbore locations. Wide azimuth seismic data provides an alternative way to predict the azimuth of natural fractures and maximum in-situ horizontal stress if the seismic attributes are properly calibrated with interpretations from well logs and microseismic data. To predict the azimuth of natural fractures and in-situ maximum horizontal stress, we focus our analysis on correlating the seismic attributes computed from pre-stack and post-stack seismic data with the interpreted azimuth obtained from image logs and microseismic data. The application indicates that the strike of the most positive principal curvature k1 can be used as an indicator for the azimuth of natural fractures within our study area. The azimuthal anisotropy of the dominant frequency component if offset vector title (OVT) seismic data can be used to predict the azimuth of maximum in-situ horizontal stress within our study area that is located the southern region of the Sichuan Basin, China. The predicted azimuths provide important information for the following well planning and hydraulic fracturing.

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