John C. Lorenz - Applied Concepts in Fractured Reservoirs

Left : histogram of the non‐ideal dip angles o... Figure 1.12 Left : the frequency of extension fractures by lithology from 4,200... Figure 1.13 Left : parallel‐striking extension fractures with irregular heights... Figure 1.14 Left: Withjack et al. (1990) documented the enhanced fracturing th... Figure 1.15 Schematic illustration of the distribution of shear and extension ... Figure 1.16 A calcite‐mineralized, inclined extension fracture in a Paleozoic ... Figure 1.17 Left : histogram showing the height distribution of bed‐normal exte... Figure 1.18 Left : two extension fractures exposed on a shale bedding surface h... Figure 1.19 Distributions of fracture length populations follow log‐normal or ... Figure 1.20 Irregular open fracture apertures. Left : an incompletely mineraliz... Figure 1.21.1 Histograms and a cross plot showing the distributions of fractur... Figure 1.21.2 Histograms and a cross plot showing the distributions of fractur... Figure 1.21.3 Histograms and a cross plot showing the distributions of fractur... Figure 1.22 Histograms of fracture‐normal fracture spacings measured in two ho... Figure 1.23 Top and lower left : outcrops showing the relatively regular spacin... Figure 1.24 Spacing distributions measured from remote imagery for the two mut... Figure 1.25 Left : parallel, bed‐normal, vertical extension fractures in thin b... Figure 1.26 A stereoplot of 360 poles to planes measured for deformation‐band ... Figure 1.27 A vertical, incompletely mineralized extension fracture in sandsto... Figure 1.28 The record of thrust‐related differential stresses, measured from ... Figure 1.29 A simple, ideal stress‐strain curve, showing initial elastic defor... Figure 1.30 This generalized laboratory stress‐strain chart shows the effect o... Figure 1.31 Two views of a coarse‐grained, arkosic fluvial sandstone (the Perm... Figure 1.32 The difference between ductility and strength, illustrated by four...Figure 1.33 The theoretical compressive strengths ( left ) and ductilities ( righ ...Figure 1.34 Stress‐strain curves plotting the strength of sandstones show simi...Figure 1.35 Interbedded heavily fractured dolomite (the gray upper layers) and...Figure 1.36 Even inherently weak mudrock becomes stronger when subjected to in...Figure 1.37 Left : laboratory tests show that the strength of samples from the ...Figure 1.38 Two variables were changed during these tests, one intrinsic to th...Figure 1.39 Left : graph showing the increase in frequency of acoustic emission...Figure 1.40 Thin sections cut from rock deformed in the laboratory have shown ...Figure 1.41 The strain‐accommodation structures that form in a given lithology...Figure 1.42 A cross plot between measured pore pressures and the associated me...Figure 1.43 Left : a depiction of the change in effective stress state due to c...Figure 1.44 The circle diameter defined by the maximum (S 1) and minimum (S 3) s...Figure 1.45 The relationships between changing pore pressure and changing tota...Figure 1.46 The effects of pore pressure on rock strength. Top : “Force‐Deforma...Figure 1.47 Left : a conceptual representation of changes in fracture mode (ext...Figure 1.48 Left : thrust‐oriented, reverse‐dip‐slip deformation‐band shear fra...Figure 1.49 Left : a thin section showing the collapsed porosity and grain‐size...Figure 1.50 Left : a thin section cut across a conjugate deformation‐band shear...Figure 1.51 Two views of a normal dip‐slip fault system in The Chalk, Cretaceo...Figure 1.52 Two views of a strike‐slip fault in limestones of the Niobrara For...Figure 1.53 Thickness‐length correlations for stylolites in limestones, Gubbio...Figure 1.54 Map‐view photo ( left ) and sketch ( right ) of a horizontal bedding p...Figure 1.55 Top : layered strata are prone to bed‐parallel shear during folding...Figure 1.56 Two views of a bed‐parallel shear fracture in the butt section of ...Figure 1.57 Left : the steeply dipping sandstones and limestones of the Pennsyl...Figure 1.58 Left : a bedding‐parallel, beef‐filled, calcite‐mineralized fractur...Figure 1.59 White, laterally extensive layers of beef form resistant ledges in...Figure 1.60 Two views of short, ptygmatically folded vertical extension fractu...Figure 1.61 Left : an early‐formed vertical extension fracture was filled with ...Figure 1.62 Left : a bed‐normal dissolution slot that followed a short, strata‐...Figure 1.63 A rectilinear pattern of dissolution along a fracture system is re...Figure A.1 Convergence of the effective maximum and minimum effective stresses...Figure A.2 Not only do the stress circles on a Mohr diagram decrease in size a...

2 Part 2Figure 2.1 Poorly mineralized fractures that are oblique to the core axis may ...Figure 2.2 The typical tightly packed layout of core boxes on tables leaves no...Figure 2.3 Piecing core together on a layout table exposes all core surfaces a...Figure 2.4 Core‐analysis tools in a traveling desk made of a core‐box lid. Pro...Figure 2.5 Left : a Master Orientation Line (the green “MOL”) marked on a verti...Figure 2.6 Drawing a green Master Orientation Line on a core surface for conti...Figure 2.7 Petal fractures, induced by the weight of the bit on the formation ...Figure 2.8 Top : a system of two intersecting sets of extension fractures break...Figure 2.9 A set of closely spaced fractures with a compound history on a fold...Figure 2.10 Measuring fracture dip angle with a carpenter's protractor, using ...Figure 2.11 Examples of fracture dip‐angle histograms derived from core data. Figure 2.12 Example of variable fracture depth‐distributions by type in one co...Figure 2.13 An example of fracture distribution, plotting fracture frequency b...Figure 2.14 Example of the percentage distribution of three fracture types by ...Figure 2.15 Left : an example of a known vertical fracture termination, where a...Figure 2.16 Left : chart showing the cumulative heights for vertical extension ...Figure 2.17 Example of vertical‐fracture height data from a vertical core, doc...Figure 2.18 Example of a dataset for vertical fracture heights captured by a v...Figure 2.19 Left : histogram showing the truncated, measurable heights for a po...Figure 2.20 If only one face of a mineralized fracture is available for measur...Figure 2.21 A visual reference for estimating remnant fracture porosity (from ...Figure 2.22 Top left : a histogram of the widths of bed‐normal extension fractu...Figure 2.23 Top left : a histogram of the widths of bed‐normal extension fractu...Figure 2.24 Top : a histogram of remnant fracture porosity data in carbonates m...Figure 2.25 Histograms of fracture data from other carbonates can be more regu...Figure 2.26 A dataset from cored shear fractures. Top left : a histogram of the...Figure 2.27 Two views of a shear fracture in four‐inch (10 cm) diameter core. Figure 2.28 The apparent fracture spacings in a core or scan line must be geom...Figure 2.29 Top left : a histogram of true fracture spacings (i.e. spacings nor...Figure 2.30 Left : rose plot showing the orientations of 46 vertical extension ...Figure 2.31 The true spacings of 31 vertical extension fractures measured in h...Figure 2.32 Left : histogram showing spacings measured between 49 pairs of vert...Figure 2.33 An example where 12 near‐vertical, calcite‐mineralized extension f...Figure 2.34 Plots of the probability of intersecting vertical fractures with 4...Figure 2.35 Top : a rose plot of the strikes of 57 vertical, strike‐slip shear ...Figure 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...

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