Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks

2012 ◽  
Vol 370 (1) ◽  
pp. 187-206 ◽  
Author(s):  
J. N. Hooker ◽  
L. A. Gomez ◽  
S. E. Laubach ◽  
J. F. W. Gale ◽  
R. Marrett
Keyword(s):  
Carbonate Rocks ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Size Scaling ◽  
Fracture Opening

High-resolution stratigraphic characterization of natural fracture attributes in the Woodford Shale, Arbuckle Wilderness and US-77D Outcrops, Murray County, Oklahoma

2018 ◽  
Vol 6 (1) ◽  
pp. SC29-SC41 ◽  
Author(s):  
Sayantan Ghosh ◽  
John N. Hooker ◽  
Caleb P. Bontempi ◽  
Roger M. Slatt
Keyword(s):  
Natural Fracture ◽  
Fracture Aperture ◽  
Aperture Size ◽  
Fracture Density ◽  
Area Formula ◽  
Woodford Shale ◽  
Fracture Spacing ◽  
Spacing Ratio ◽  
Fracture Intensity ◽  
Bed Thickness

Natural fracture aperture-size, spacing, and stratigraphic variation in fracture density are factors determining the fluid-flow capacity of low-permeability formations. In this study, several facies were identified in a Woodford Shale complete section. The section was divided into four broad stratigraphic zones based on interbedding of similar facies. Average thicknesses and percentages of brittle and ductile beds in each stratigraphic foot were recorded. Also, five fracture sets were identified. These sets were split into two groups based on their trace exposures. Fracture linear intensity (number of fractures normalized to the scanline length [[Formula: see text]]) values were quantified for brittle and ductile beds. Individual fracture intensity-bed thickness linear equations were derived. These equations, along with the average bed thickness and percentage of brittle and ductile lithologies in each stratigraphic foot, were used to construct a fracture areal density (number of fracture traces normalized to the trace exposure area [[Formula: see text]]) profile. Finally, the fracture opening-displacement size variations, clustering tendencies, and fracture saturation were quantified. Fracture intensity-bed thickness equations predict approximately 1.5–3 times more fractures in the brittle beds compared with ductile beds at any given bed thickness. Parts of zone 2 and almost entire zone 3, located in the upper and middle Woodford, respectively, have high fracture densities and are situated within relatively organic-rich (high-GR) intervals. These intervals may be suitable horizontal well landing targets. All observed fracture cement exhibit a lack of crack-seal texture. Characteristic aperture-size distributions exist, with most apertures in the 0.05–1 mm (0.00016–0.0032 ft) range. In the chert beds, fracture cement is primarily bitumen or silica or both. Fractures in dolomite beds primarily have calcite cement. The average fracture spacing indices (i.e., bed thickness-fracture spacing ratio) in brittle and ductile beds were determined to be 2 and 1.2, respectively. Uniform fracture spacing was observed along all scanlines in the studied beds.

Karst generation in three-dimensional jointed layered rocks

2021 ◽  
Author(s):  
Chuanyin Jiang ◽  
Xiaoguang Wang
Keyword(s):  
Carbonate Rocks ◽  
Numerical Models ◽  
Three Dimensional ◽  
Dissolution Kinetics ◽  
Bedding Plane ◽  
Fracture Aperture ◽  
Fracture Networks ◽  
Aperture Ratio ◽  
Bedding Planes ◽  
Fractured Carbonate

<p>We use numerical models to investigate the generation of incipient karst in layered geological systems, and specifically to investigate the effects of the structural and hydraulic properties of both joints and bedding planes on the distribution of the developed karst cavities. We develop a numerical model which couples the processes of fluid flow, mass transport and dissolution kinetics that govern the growth of fracture aperture, based on three-dimensional discrete fracture networks. The synthetic fracture networks made up of two jointed layers separated by a horizontal bedding plane are generated to represent the typical layered fracture systems often formed in carbonate rocks. We assume a relatively uniform aperture field with a small variance for each joint set and for the bedding plane, but different joint sets and the bedding plane can have non-identical mean apertures. Results show that the aperture ratio of the joint sets to the bedding plane is found to dominate the flow heterogeneity on the bedding plane, leading to various behaviors of karst development. We further suggest that the distinct flow regimes, i.e., joint-dominated, transitional and bedding plane-dominated, controlled by the magnitude of the aperture ratio, are responsible for the different types of incipient karst morphologies. Our investigations have an important application on the understanding of clustering behaviors of karst cavities in layered fractured carbonate rocks.</p><div> </div>

Aperture-size scaling variations in a low-strain opening-mode fracture set, Cozzette Sandstone, Colorado

2009 ◽  
Vol 31 (7) ◽  
pp. 707-718 ◽  
Author(s):  
J.N. Hooker ◽  
J.F.W. Gale ◽  
L.A. Gomez ◽  
S.E. Laubach ◽  
R. Marrett ◽  
...  
Keyword(s):  
Aperture Size ◽  
Mode Fracture ◽  
Size Scaling ◽  
Opening Mode

Resolution Attainable With the Present Day STEM

1973 ◽  
Vol 31 ◽  
pp. 230-231 ◽  
Author(s):  
J. S. Wall ◽  
J. P. Langmore ◽  
H. Isaacson ◽  
A. V. Crewe
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Aperture Size ◽  
Magnetic Lens ◽  
Peak Intensity ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Half Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

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