Fracture evolution in a fold-and-thrust belt and the adjacent foreland basin: an example from the Northeastern Brooks Range, Alaska

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Author
Loveland, Andrea M.
Keyword
Orogenic belts
Brooks Range
Geological folds
Geological faults
Geological basins
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URI
http://hdl.handle.net/11122/12741
Abstract
"Fracture networks can enhance permeability in a reservoir, creating pathways for fluid migration. This study uses detailed surface and subsurface mapping, new and existing thermal and geochronologic data as well as observations of fractures in outcrop provide a framework for fracture development in the range front region along a surface to subsurface transect in the western part of the northeastern Brooks Range. Set 1 fractures formed prior to 45 Ma at>6 km depth, ahead of the Brooks Range mountain front in response to elevated pore fluid pressure and low differential stress. Set 2 fractures developed during the early stages of folding at a depth of ~7 km. Both Sets 1 and 2 developed synchronously with hydrocarbon generation and may have been early migration pathways, but were likely destroyed during advancement of the thrust belt. Late fracture Sets 3 and 4 formed at shallow depths in the absence of fluids and are probably related to the onset of uplift at ~25 Ma. These late sets postdate regional generation and migration, but may enhance reservoir permeability"--Leaf iii
Description
Thesis (M.S.) University of Alaska Fairbanks, 2010
Table of Contents
1. Introduction -- 2. Geologic setting -- 2.1. Regional structural geology -- 2.2. Brooks Range cooling events -- 2.3. Regional stratigraphy and structural style of the northeastern Brooks Range -- 2.4. Hydrocarbon systems in the northeastern Brooks Range -- 2.5. Previous fracture studies in the northeastern Brooks Range -- 3. Fault-related folds and fractures -- 3.1. Types of fractures -- 3.2. Fracture initiation -- 3.3. Fractures in flat-lying rocks -- 3.4. Fold-related fractures -- 3.5. Neotectonic joints -- 3.6. Fault-related folds -- 3.7. Mechanical stratigraphy and fractures -- 4. Methodology -- 4.1. Tasks -- 4.2. Fracture analysis techniques -- 4.3. Thermal and geochronologic techniques -- 4.3.1. Vitrinite reflectance -- 4.3.2. Fluid inclusions -- 4.3.3. Conodont alteration index -- 4.3.4. Apatite and zircon fission track thermochronology -- 5. Geology of the field map area -- 5.1. Introduction -- 5.2. Surface observations -- 5.2.1. Lithostratigraphy -- 5.2.2. Mechanical stratigraphy -- 5.2.3. Faults -- 5.2.4. Folds -- 5.2.5. Structural domains -- 5.2.6. Cross sections from surface data -- 5.3. Subsurface observations and interpretations -- 5.3.1. Subsurface stratigraphy -- 5.3.2. Subsurface structure -- 5.4. Discussion -- 6. Fracture characteristics and thermal history of the study area -- 6.1. Fracture characteristics and distribution -- 6.1.1. Set 1: N-S striking filled fractures -- 6.1.2. Set 2: E-W striking filled fractures -- 6.1.3. Set 3: N-S striking unfilled fractures -- 6.1.4. Set 4: E-W striking unfilled fractures -- 6.1.5. Fracture porosity from well logs -- 6.2. Thermal constraints on faulting, folding, and fracturing -- 6.3. Geochronologic constraints on deformation -- 6.4. Discussion -- 6.4.1. Origin of fracture sets -- 6.4.2. Fracture distribution and structural position -- 6.4.3. Fractures and stratigraphic position -- 6.4.4. Thermal and age constraints on faulting, folding, and fractu;ring -- 6.4.5. Petroleum system implications -- 7. Conclusions -- 7.1. Structural, thermal, and geochronologic history -- 7.2. History of fracture set development -- 7.3. Stratigraphic controls on fracture development -- 7.4. Implications for hydrocarbon exploration -- 7.5. Implications for fracture research -- 7.6. Future work -- References.
Date
2010-05
Type
Thesis
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