Summary Log of Fracture and Tectonic Features—An Example
1990. "Summary Log of Fracture and Tectonic Features—An Example", Fractured Core Analysis: Interpretation, Logging, and Use of Natural and Induced Fractures in Core, B. R. Kulander, S. L. Dean, B. J. Ward, Jr.
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An orderly depiction of structural information, including fractures, obtained from oriented and unoriented core, facilitates the comparison and evaluation of diverse data sets. This is important because a thorough evaluation of core may produce information that influences decisions during production and exploration planning. The hypothetical fracture-tectonic log shown in Figure 58 is one example of how to display diverse fracture and structural information in core. The log shows several distributional and geometrical relationships that may exist in one set of similar features. In addition, relationships also are made apparent between diverse data sets such as lithology, induced and natural fractures, faults, and other tectonic indicators including slickenlines and stylolites. When core contains adequate information, selected features can be used to infer both paleo and in-situ stresses as well as the relative chronology of development of fracture sets and other structural features.
The sample log is more complex than those commonly derived from actual examination. This is so because data are tightly grouped, especially in the pictorial log, to show a maximum number of examples. All of the logged features have been observed in core. However, the sample log contains more diverse information than commonly would be observed in a single core.
The log does not contain columns for all information that may be obtained from any core or group of cores. In this respect, a final fracture-tectonic log often is best designed after core examination is completed. Such flexibility permits emphasis of pertinent information obtained in that particular investigation. The
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The characterization of naturally fractured reservoirs should include core analyses that encompass interpretation of natural and induced fractures. Unfortunately, to date, the differentiation of induced fractures from natural ones in core has been somewhat speculative and often is based on improper techniques. Consequently, bad interpretations have been made and useful information contained in both natural and induced fractures is overlooked. This book addresses the problem of distinguishing natural fractures from induced fractures in both oriented and unoriented core. Natural fractures include any cored fracture that existed in a volume of rock prior to initiation of drilling or coring-related stresses. Induced fractures in core are those that develop during drilling, coring, and subsequent handling. Many of the procedures for distinguishing between the two are based primarily on recognition of fracture surface structures and fracture traces that differ between natural fractures and induced fractures.