Decoupling of deformation in the Upper Rhine Graben sediments. Seismic reflection and diffraction on 3-component Vertical Seismic Profiling (Soultz-sous-Forêts area)

Abstract A contribution to the definition of the structural pattern of the Soultz-sous-Forets EGS (Enhanced Geothermal System) is presented here. After reprocessing, the PHN84J seismic reflection profile highlights the tilted blocks of the Merkwiller-Pechelbronn oilfield. In the Soultz-sous-Forets horst, complex fault patterns are observed: the Hermerswiller normal fault flattens at depth and is rooted in decollements occurring in Triassic salt or clay series, while other steep normal faults affect underlying sedimentary formations and basement. Some methods for the exploitation of a seismic diffraction recorded by multi-component Vertical Seismic Profiling (VSP) are also illustrated to locate the diffractor without specific data processing. Polarisation and travel time analysis of a diffraction event recorded in the GPK1 borehole are analysed, and its exploitation combined with seismic reflection helps defining a tilted block geometry.

[1]  Philippe Renard,et al.  Three-dimensional geometric modeling of a faulted domain: the Soultz Horst example (Alsace, France) , 1994 .

[2]  Teruo Yamashita,et al.  Scattering of elastic waves by a fracture zone containing randomly distributed cracks , 1992 .

[3]  F. A. Angona.  TWO‐DIMENSIONAL MODELING AND ITS APPLICATION TO SEISMIC PROBLEMS , 1960 .

[4]  J. Hudson,et al.  Diffraction of seismic waves by cracks with application to hydraulic fracturing , 1997 .

[5]  Chrystel Dezayes,et al.  3D model of fracture zones at Soultz-sous-Forêts based on geological data, image logs, induced microseismicity and vertical seismic profiles , 2010 .

[6]  R. Schnaebele.  Monographie géologique du champ pétrolifère de Pechelbronn , 1948 .

[7]  Ru-Shan Wu,et al.  Scattering characteristics of elastic waves by an elastic heterogeneity , 1985 .

[8]  Q. Zhang,et al.  Acoustic pulse diffraction by step discontinuities on a plane , 1990 .

[9]  D. Martí,et al.  Characterization of a fractured granitic pluton: P- and S-waves' seismic tomography and uncertainty analysis , 2006 .

[10]  A. Beauce,et al.  Seismic studies on the HDR site of Soultz-sous-Forêts (Alsace, France) , 1991 .

[11]  J. Virieux.  P-SV wave propagation in heterogeneous media: Velocity‐stress finite‐difference method , 1986 .

[12]  M. Schumacher,et al.  Upper Rhine Graben: Role of preexisting structures during rift evolution , 2002 .

[13]  T. Tan.  Scattering of plane, elastic waves by a plane crack of finite width , 1977 .

[14]  F. Neerhoff,et al.  Scattering and P/SV-Conversion of Elastic Waves by a Plane Crack of Finite Width , 1983 .

[15]  L. Harris,et al.  The effect of cover composition on extensional faulting above re-activated basement faults: results from analogue modelling , 1997 .

[16]  A. W. Trorey.  Diffractions for arbitrary source-receiver locations , 1977 .

[17]  Fault throw determination using 4 component VSP: Aigion fault (Greece) case study , 2007 .

[18]  Fred Hilterman,et al.  AMPLITUDES OF SEISMIC WAVES—A QUICK LOOK , 1975 .

[19]  C. Castaing,et al.  Comparative analysis of direct (core) and indirect (borehole imaging tools) collection of fracture data in the Hot Dry Rock Soultz reservoir (France) , 1997 .

[20]  A. Levander.  Fourth-order finite-difference P-SV seismograms , 1988 .

[21]  S. Kaufman,et al.  A three-dimensional study of seismic diffraction patterns from deep basement sources , 1981 .

[22]  K. Schulmann,et al.  The Variscan tectonic inheritance of the Upper Rhine Graben: evidence of reactivations in the Lias, Late Eocene–Oligocene up to the recent , 2007 .

[23]  Frank Rieber,et al.  Complex reflection patterns and their geologic sources , 1937 .

[24]  O. Coutant.  Numerical study of the diffraction of elastic waves by fluid‐filled cracks , 1989 .

[25]  Albert Genter,et al.  Permeability creation and damage due to massive fluid injections into granite at 3.5 km at Soultz: 1. Borehole observations , 2005 .

[26]  M. Withjack,et al.  Active Normal Faulting Beneath a Salt Layer: An Experimental Study of Deformation Patterns in the Cover Sequence , 2000 .

[27]  John R. Berryhill,et al.  DIFFRACTION RESPONSE FOR NONZERO SEPARATION OF SOURCE AND RECEIVER , 1977 .

[28]  Stéphane Roussé.  Architecture et dynamique des séries marines et continentales de l'oligocène moyen et supérieur du sud du fossé rhénan : Evolution des milieux de dépôt en contexte de rift en marge de l'avant-pays alpin , 2006 .

[29]  B. Vendeville.  Champs de failles et tectonique en extension : Modélisation expérimentale , 1987 .

[30]  D. R. Harper.  Observed reflection and diffraction wavelet complexes in two-dimensional seismic model studies of simple faults , 1965 .