scholarly journals Transport and retention from single to multiple fractures in crystalline rock at Äspö (Sweden): 1. Evaluation of tracer test results and sensitivity analysis

2010 ◽  
Vol 46 (5) ◽  
Author(s):  
V. Cvetkovic ◽  
H. Cheng ◽  
J. Byegård ◽  
A. Winberg ◽  
E.-L. Tullborg ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Crystalline Rock ◽  
Tracer Test ◽  
Test Results ◽  
Multiple Fractures

Core Scale FEM Modeling of Thermochemical Fracturing on Cement Cube Samples

2021 ◽  
Author(s):  
Zeeshan Tariq ◽  
Ayman AlNakhli ◽  
Abdulazeez Abdulraheem ◽  
Mohamed Mahmoud
Keyword(s):  
Sensitivity Analysis ◽  
Global Economy ◽  
Oil And Gas ◽  
Peak Pressure ◽  
Exothermic Reaction ◽  
Cohesive Zone Modeling ◽  
Fem Modeling ◽  
Breakdown Pressure ◽  
Multiple Fractures ◽  
Micro Cracks

Abstract Brownfields and depleting conventional resources of fossil fuel energy are not enough to fulfill the tremendously increasing energy demands around the globe. Unconventional oil and gas resources are creating a huge impact on the enhancement of the global economy. Tight rocks are usually located in deep and high-strength formations. In this study, numerical simulation results on a new thermochemical fracturing approach is presented. The new fracturing approach was implemented to reduce the breakdown pressure of the unconventional tight formations. The hydraulic fracturing experiments presented in this study were carried out on ultra-tight cement block samples. The permeability of the block samples was less than 0.005mD. Thermochemical fracturing was carried out by a thermochemical fluids that caused a rapid exothermic reaction which resulted in the instantaneous generation of heat and pressure. Different salts of nitrogen such as sodium nitrite and ammonium chloride were used as a thermochemical fluid. The instantaneous generation of the heat and pressure caused the creation of micro-cracks. The fracturing results revealed that the novel thermochemical fracturing was able to reduce the breakdown pressure in ultra-tight cement from 1095 psi to 705 psi. The reference breakdown pressure was recorded from the conventional fracturing technique. A finite element (FEM) analysis was conducted using commercial software ABAQUS. In FEM, two approaches were used to model the thermochemical fractures namely, cohesive zone modeling (CZM) and concrete damage plasticity models (CDP). The sensitivity analysis of peak pressure and time to reach the peak pressure is also presented in this study. The sensitivity analysis can help in better designing thermochemical fluids that could lead to the maximum generation of micro-cracks and multiple fractures.

Hydraulic Conductivity and Scale Effects Investigation in Basalt in the Dam Area of Xiluodu Hydroelectric Station, Jinshajiang River, China

2013 ◽  
Vol 405-408 ◽  
pp. 2123-2129
Author(s):  
Yuan Yao Li ◽  
Rong Lin Sun ◽  
Ren Quan Chen
Keyword(s):  
Hydraulic Conductivity ◽  
Scale Effects ◽  
Fractured Rock ◽  
Water Pressure ◽  
Hydroelectric Station ◽  
Tracer Test ◽  
Test Results ◽  
Hydraulic Test ◽  
Water Seepage ◽  
Pressure Tests

Hydraulic conductivity (K) and scale effects in basalt in the dam area of Xiluodu hydroelectric station were investigated by three kinds of field hydraulic tests with different test scale, 2608 water pressure tests in single borehole, 54 water seepage tests in adit and groundwater tracer test. Statistical results show the high heterogeneity of fractured rock and K difference between two neighboring test intervals are often more than two orders of magnitude. However, there is a strong decreasing trend of hydraulic conductivity with the increase of vertical depth. Moreover, these three kinds of hydraulic test results demonstrate that hydraulic conductivity increases with the increase of test scale in heterogeneous basalt and the heterogeneous degree of K decreases with the increase of test scale. K from water seepage test in adit, with the test scale of 1-2 m, is dispersed from 0.00024 m/d to 3.46 m/d. K from water pressure test in single borehole, with the test scale of 4-7 m, is 0.0002-1.04 m/d. K from groundwater tracer test, with the test scale of 70-145 m, is concentrated between 0.46 m/d and 2.1 m/d. High heterogeneity of fractured rock and multi-level of fractures are thought as the major reason resulted in scale effects of hydraulic conductivity.

Uncertainty and sensitivity analysis of the LOFT L2-5 test: Results of the BEMUSE programme

2008 ◽  
Vol 238 (12) ◽  
pp. 3561-3578 ◽  
Author(s):  
A. de Crécy ◽  
P. Bazin ◽  
H. Glaeser ◽  
T. Skorek ◽  
J. Joucla ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Test Results ◽  
Uncertainty And Sensitivity Analysis

scholarly journals Groundwater circulation and earthquake-related changes in hydrogeological karst environments: a case study of the Sibillini Mountains (central Italy) involving artificial tracers

2020 ◽  
Vol 28 (7) ◽  
pp. 2409-2428 ◽  
Author(s):  
T. Nanni ◽  
P. M. Vivalda ◽  
S. Palpacelli ◽  
M. Marcellini ◽  
A. Tazioli
Keyword(s):  
Central Italy ◽  
Tracer Tests ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Water Circulation ◽  
Test Results ◽  
Flow Rates ◽  
Aquifer System ◽  
Structural Framework ◽  
Groundwater Circulation

Abstract Using artificial tracer tests, this study confirms the presence of a single basal aquifer feeding the springs in the wide and complex hydrogeological boundary of the Sibillini Mountains of central Italy. The tracer was introduced into the sinkhole of the Castelluccio di Norcia plain. The tracer test results, observed at the studied springs, highlight the changes induced by the 2016/2017 earthquake in the water circulation of the aquifer system. In particular, the seismic events increased the hydraulic conductivity of the basal aquifer, with a consequent increase in the springs’ flow rates at the western hydrogeological boundary and a decrease in the flow rates at the eastern Adriatic hydrogeological boundary. This phenomenon is in accordance with the hydro-structural framework of the area. The study also investigated the relation between groundwater circulation and tracer behaviour in the springs during the pre- and post-earthquake periods. The tracer test results led to the formulation of hypotheses about water circulation of the area. The trend of the tracer breakthrough curves demonstrates that the upper portion of the basal aquifer is characterised by fast water circulation similar to that in the epiphreatic area of karst aquifers, while a slow circulation due to fissures with interconnected drains occurs in the deepest portion of the aquifers. The obtained results highlight how tectonics and karst can affect the hydrogeological setting of the Apennine carbonate chain; in particular, the seismicity of central Italy may alter groundwater circulation for a long period of time when great magnitude earthquakes occur.

A Lifting-Line Equivalent Profile Method for Propeller Calculations

1985 ◽  
Vol 29 (04) ◽  
pp. 241-250
Author(s):  
G. K. Politis
Keyword(s):  
Sensitivity Analysis ◽  
Iteration Scheme ◽  
Test Results ◽  
Equivalent Radius ◽  
Profile Method ◽  
Constant Pitch ◽  
Power Loading ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory

The theoretical shortcomings of Lerbs' equivalent profile method are discussed and a novel equivalent profile method, using lifting-line theory, is presented. Details of the iteration scheme necessary for the solution of the resulting nonlinear problem are given. The problem of the equivalent radius is rationally formulated and uncertainties are shown to exist concerning the choice of the equivalent radius and the approximate relations for the efficiency and the power loading coefficient. The test results of five model propellers, with different geometric characteristics, are used in an extensive sensitivity-analysis procedure to demonstrate the good behavior of the proposed lifting-line equivalent profile method. A corresponding sensitivity analysis of Lerbs' equivalent profile method shows poor behavior with respect to changes in the equivalent radius, especially for non-constant-pitch propellers. The new method can easily be applied to wake-adapted propellers.

Bacterial Transport in Fractured Rock – A Field-Scale Tracer Test at the Chalk River Nuclear Laboratories

1988 ◽  
Vol 20 (11-12) ◽  
pp. 81-87 ◽  
Author(s):  
D. R. Champ ◽  
J. Schroeter
Keyword(s):  
Water Movement ◽  
Fractured Rock ◽  
Tracer Tests ◽  
Crystalline Rock ◽  
Tracer Test ◽  
Breakthrough Curves ◽  
Water Recovery ◽  
Field Scale ◽  
Particulate Contaminants ◽  
Conservative Tracers

The potential for transport of bacteria by groundwater in fractured crystalline rock was assessed in a series of field-scale tracer tests. The breakthrough curves for injected Escherichla coll and “non-reactive” particle tracers were compared with those for conservative inorganic and radioactive tracers. Rapid transport, relative to the conservative tracers, of both bacteria and non-reactive particles was observed. The first appearance of both was with, or slightly before, the conservative tracers for water movement. Removal of the bacteria and particles by filtration processes occurred and was quantified through the calculation of filter factors. The filtration process in this fracture system is similar to that found in a gravel aquifer. From the results we can conclude that particulate contaminants can be very rapidly transported in fracture systems and that continuing sources of contamination could lead to relatively high local concentrations of particulate contaminants compared with the average at any given distance from the source. It was also concluded that the use of traditional conservative tracers, for water movement, to assess the potential for movement of particulate contaminants could lead to significant underestimates of exposure to particulate contaminants due to consumption of water from water recovery wells located in fractured media.

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