Fracture analysis

	Exploring for Oil and Gas Traps
Series	Treatise in Petroleum Geology
Part	Predicting the occurrence of oil and gas traps
Chapter	Exploring for structural traps
Author	R.A. Nelson, T.L. Patton, S. Serra
Link	Web page
Store	AAPG Store

Information provided

Five types of fracture analysis provide the following types of information:

Outcrop studies

Regional-scale to prospect-scale fracture orientation, distribution, width, and spacing
Fracture size and morphology

Curvature analysis

Strain distribution prediction based on geometry from structural mapping (fold shape and location on fold)
Natural fracture intensity prediction and, to a limited extent, fracture porosity, given assumptions regarding rock behavior and strain partitioning

Core analysis

Downhole fracture distribution, orientation, size, width, spacing, and morphology
Relationship between petrophysical properties of fractures and matrix

Log analysis

Detection of fractures in a nonquantitative manner
Orientation of a selected fracture population
In some cases, determination of the fluid or mineral filling in fractures

Mathematical models

Prediction of compactive vs. dilatant rock behavior
Maps of fracture zones and variations in fracture intensity
Prediction of fracture porosity, given assumptions regarding relationships between stress and strain and the fracture response of the rock

How to use it

Fracture analysis can help us define structural axes and trends or fracture-related reservoir properties. It can be applied in a variety of structural terranes and rock types, but it is especially important in brittle rock packages. To determine reservoir-property requires integrating geology, petrophysics, and reservoir engineering, and it is most often done by experienced specialists.

Examples of use

Narr, W., 1996, Estimating average fracture spacing in subsurface rock: AAPG Bulletin, vol. 80, p. 1565–1586.
Laubach, S. E., 1997, A method to detect natural fracture strike in sandstones: AAPG Bulletin, vol. 81, p. 604–623.
Laubach, S. E., 1989, Fracture Analysis of the Travis Peak Formation, Western Flank of the Sabine Arch, East Texas: University of Texas at Austin Bureau of Economic Geology Report of Investigations 185, 55 p.
Kulander, B. R., S. L. Dean, and B. J. Ward, Jr., 1990, Fractured Core Analysis: Interpretation, Logging, and Use of Natural and Induced Fractures in Core: AAPG Methods in Exploration 8, 88 p.
Jamison, W. R., 1997, Quantitative evaluation of fractures on Monkshood anticline, a detachment fold in the foothills of western Canada: AAPG Bulletin, vol. 81, 1110–1132.
Aguilera, R., 1980, Naturally Fractured Reservoirs: Tulsa, PennWell, 703 p.
Coward, M. P., T. S. Daltaban, and H. Johnson, eds., Structural Geology in Reservoir Characterization: Geological Society of London Special Publication 127, 266 p.
Nelson, R. A., and S. Serra, 1995, Vertical and lateral variations in fracture spacing in folded carbonate sections and its relation to locating horizontal wells: Journal of Canadian Petroleum Technology, vol. 34, p. 51–56, DOI: 10.2118/95-06-05.
Nelson, R. A., 1985, Geologic Analysis of Naturally Fractured Reservoirs: Houston, Gulf Publishing Co., 320 p.
U.S. National Committee for Rock Mechanics, 1996, Rock Fractures and Fluid Flow: Washington, D., C., National Academy Press, 551 p.
Wiltschko, D. V., K. P. Corbett, M. Friedman, and J.-H. Hung, 1991, Predicting fracture connectivity and intensity within the Austin Chalk from outcrop fracture maps and scanline data: Transactions of the Gulf Coast Association of Geological Societies, vol. 41, p. 702–718.

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Fracture analysis