--> Analysis of Thrust-Related Fold Geometries Utilizing SCAT and Tangent Plots: Implications for Well Prognoses and Reservoir Calculations, by S. E. Boyer and J. D. Morse; #90986 (1994).

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Abstract: Analysis of Thrust-Related Fold Geometries Utilizing SCAT and Tangent Plots: Implications for Well Prognoses and Reservoir Calculations

Steven E. Boyer, James D. Morse

SCAT and tangent plots of real folds and models indicate that fault-propagation folds change shape along strike from cylindrical to conical. The opposed conical terminations of a fault-propagation fold broaden down-plunge in the direction of lateral fault propagation and are joined at their up-plunge apices by a cylindrical culmination. Two opposed kink bands, joined by an undeformed interlimb region, define each lateral termination. Data from either kink band and the adjacent interlimb band plot as a cylindrical fold, but data from both limbs and the interlimb region describe a non circular cone generated by the up-plunge convergence of the two cylindrical fold segments.

Fault-propagation folds also change shape with depth. The opposed kink axial planes intersect at depth, defining a chevron core. In the cylindrical culmination, the line of kink-plane intersection lies in bedding, and the trend and plunge of the structure remain constant with depth. However, in the plunging terminations of the fold, the kink-plane intersection does not lie in bedding and plunges at a higher angle than does the axis of the chevron fold. As a consequence, a broad box-shaped structure in the near surface may plunge at a steeper angle than does the tight, chevron fold at depth.

Interpretation of such complex structures is aided by SCAT and tangent analysis, methods that are especially useful and cost-effective when applied to real-time analysis of exploratory wells, prediction of closure, and estimation of reserves.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994