2.36 Map view of fracture locations and strikes along approximately 80 ...Figure 2.37 Top left: side view of 117 ft (36 m) of near‐horizontal core from ...Figure 2.38 Using a circular protractor. Left: looking downhole (degrees on th...Figure 2.39 Measuring the relative strike/intersection angle between two fract...Figure 2.40 Measuring intersection angles between fractures that are not expos...Figure 2.41 Left: an example of a plot of 126 pairs of vertical extension frac...Figure 2.42 Two natural fractures (green) strike about 40° clockwise and 45° c...Figure 2.43 Plan view, looking down on the high side of a horizontal core: The...Figure 2.44 If the cored bedding is parallel to the axis of a horizontal core ...Figure 2.45 Bedding and 47 parallel, vertical extension fractures were capture...Figure 2.46 The near‐horizontal bedding captured by this deviated core, viewed...Figure 2.47 Near‐horizontal core cutting down‐section across near‐horizontal b...Figure 2.48 Top: fragmented cores in stacked wooden boxes, even after having l...Figure 2.49 This interval of vertical core, viewed with uphole to the left, sh...Figure 2.50 Left: the scribe groove (red arrow) on this core rotates excessive...Figure 2.51 Data comparing 1) the measured rotation with depth of the Principa...Figure 2.52 A circular protractor placed around the core, looking downhole. If...Figure 2.53 There are various ways of determining fracture strikes relative to...Figure 2.54 Top: orienting a horizontal core and determining the high side. In...Figure 2.55 A syn‐depositional fault in core (A, left) creates a recognizable ...Figure 2.56 A wide, gypsum‐filled fracture in a calcareous mudstone has a brig...Figure 2.57 A much fainter fracture signature in the CT scan (left and middle)...Figure 2.58 Right: the two fractures shown in the CT scan of a continuous piec...Figure 2.59 Fracture data from an image log are easy to manipulate using servi...Figure 2.60 An example of correlative fracture dip‐angle histograms from a ver...Figure 2.61 Another example comparing fracture dip‐angle histograms from a ver...Figure 2.62 Determining fracture distribution by lithology from image logs. St...Figure 2.63 Outcrop data and filtered outcrop data. Bed‐normal extension fract...Figure 2.64 The strikes of 62 vertical extension fractures in oriented core fr...Figure 2.65 Left: a rose plot of fracture strikes measured in an 8 m (26‐ft) d...Figure 2.66 The sandstone bedding surface from which the rose plots of the pre...Figure 2.67 Conceptual diagrams illustrating the physical basis of direct dete...Figure 2.68 NNE‐SSW trending concave‐up structural features (blue) defined on ...Figure 2.69 An outcrop of Cretaceous Dakota sandstone showing a 10 ft (3 m) sc...Figure 2.70 A fracture intensity and orientation map for one stratigraphic lay...Figure 2.71 The Alcova Anticline consists of folded eolian sandstones and dolo...Figure 2.72 Natural‐gas sandstone reservoirs of the Mesaverde Group in Colorad...Figure 2.73 Calcite‐mineralized extension fractures. Top: a 0.05 mm wide, 1.2 ...Figure 2.74 Three views of one of the intermediate‐angle shear fractures in th...Figure 2.75 Pie charts of the fracture population in Case Study 1, showing tha...Figure 2.76 An interval of closely spaced NE‐SW and NW‐SE striking vertical fr...Figure 2.77 View of the side of the Case Study 2 core, showing a bedding plane...Figure 2.78 High‐angle extension fracture strikes relative to north, as measur...Figure 2.79 Two NE‐SW striking vertical fractures (arrows) in horizontal core....Figure 2.80 Left column: high‐angle extension fracture width histograms for al...Figure 2.81 Permeability directionality in the Case Study 2 reservoirs based o...Figure 2.82 A comparison of the predicted fracture‐controlled permeability dir...Figure 2.83 The frequency and distribution high‐angle extension fractures by d...Figure 2.84 Two views of a high‐angle extension fracture marked by plume struc...Figure 2.85 Left: high‐angle extension fracture height histogram (n = 69; min ...Figure 2.86 Histograms showing the distribution of widths (left, n = 69; min 0...Figure 2.87 A cross plot of fracture widths and remnant fracture porosities (n...Figure 2.88 Histogram showing the distribution of measurable spacings between ...Figure 2.89 Rose plot showing the relative strikes of pairs of high‐angle exte...Figure 2.90 Rose plot showing the intersection angles between high‐angle exten...Figure 2.91 Core boxes are full of surprises.Figure 2.A.1 Flowchart of data collection for understanding naturally fracture...Figure 2.C.1 Terminology for a horizontal core, viewed from the side and paral...Figure 2.C.2 Horizontal core in plan view, with the high side of the core towa...Figure 2.C.3 A horizontal core should be slabbed normal to bedding since this ...Figure 2.C.4 A sketch illustrating the consistent bedding inclines that will b...
3 Part 3Figure 3.1 Three possible conditions for fracture apertures and faces, dependi...Figure 3.2 Viscous oil seeping from fractures in tilted strata of the Eocene P...Figure 3.3 The face of a cored extension fracture (parallel to the plane of th...Figure 3.4 Left: irregular, intersecting, high‐angle, strike‐slip shear fractu...Figure 3.5 One‐inch plugs, containing natural, calcite‐mineralized vertical‐ex...Figure 3.6 Cross plot of matrix permeability vs. deformation‐band permeability...Figure 3.7 Left: a stylolite with associated short extension fractures in a li...Figure 3.8 A cross plot of porosity vs. permeability, distinguishing microfrac...Figure 3.9 Fractures can significantly enhance system permeability in conventi...Figure 3.10 An anisotropic fracture‐permeability system in the Midale carbonat...Figure 3.11 Top: a map showing the map‐view locations (red dots) of the three ...Figure 3.12 A single set of well‐developed extension fractures creates a defin...Figure 3.13 Top: map views of fractures captured by near‐horizontal cores cut ...Figure 3.14 Left: the pattern of tracer breakthrough between injection and obs...Figure 3.15 Dynamically compatible fracture sets, consisting of parallel, unif...Figure 3.16 Plan view of a sandstone bedding surface in the Cretaceous Frontie...Figure 3.17 Map views showing conceptual drainage ellipses around vertical wel...Figure 3.18 Left: chart showing the relationship over several orders of magnit...Figure 3.19 Top: production curves show interference between wells A (blue) an...Figure 3.20 Laboratory tests show that mineralized natural fractures in differ...Figure 3.21 Examples of laboratory tests comparing the susceptibility of fract...Figure 3.22 Left: The conductivity of fractured plugs cut from cores of the Ca...Figure 3.23 Stress‐sensitive, elastic fracture systems. Top: well tests in the...Figure 3.24 Two views of an inclined, dip‐slip shear fracture with an irregula...Figure 3.25 Left: Olsson (1992) and Olsson and Brown (1993) measured the chang...Figure 3.26 Gutierrez et al. (2000) used a laboratory setup similar to that sh...Figure 3.27 Calcium carbonate scale buildup reduces the diameter of oilfield t...Figure 3.28 A fractured 1 m3 block of rock that contains either a one‐centimet...Figure 3.29 Subsurface data from 115 ft (35 m) of horizontal core that was cut...Figure 3.30 Upper left: routine plugging of a core often captures natural frac...Figure 3.31 Calculating fracture surface area per volume of rock. Fracture fac...Figure 3.32 The two fracture faces of a 1 m x 3 m fracture provide significant...Figure 3.33 Observed complexity of blue‐dyed grout injections pumped into weld...Figure 3.34 Map‐view conceptual models of the interaction between natural and ...Figure 3.35 Cored multi‐stranded vertical hydraulic fractures captured by devi...Figure 3.36 Left: dike‐parallel vertical extension fractures in sandstone are ...Figure 3.37 Site of the first U.S. nuclear stimulation experiment, named “Proj...
