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Collaborating Authors
Results
Well-log Analysis of Pore Pressure Mechanisms Near a Minibasin-bounding Growth Fault At South Eugene Island Field, Offshore Louisiana
Haney, Matthew M. (Center for Wave Phenomena, Department of Geophysics, Colorado School of Mines) | Hofmann, Ronny (Center for Rock Abuse, Department of Geophysics, Colorado School of Mines) | Snieder, Roel (Center for Wave Phenomena, Department of Geophysics, Colorado School of Mines)
ABSTRACT Using well log data from the South Eugene Island field, offshore Louisiana, we derive empirical relationships between elastic parameters (e.g., -wave velocity, density) and effective stress along both normal compaction and unloading paths. These empirical relationships provide a physical basis for numerical modeling and allow us to investigate the effect of fluid pressure. The presence of more than one stress path complicates the prediction of fluid pressure from seismically derived interval velocities since the relationship between seismic velocity and pore pressure is multi-valued.
- North America > United States > Gulf of Mexico > Central GOM (0.91)
- North America > United States > Louisiana (0.62)
- North America > United States > Utah (0.62)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.48)
- Geology > Structural Geology > Fault > Dip-Slip Fault > Normal Fault > Growth Fault (0.41)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)
- Geophysics > Borehole Geophysics (1.00)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > South Eugene Island Basin > Eugene Island South (0.99)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Eugene Island > Block 330 > Eugene Island Block 330 Field (0.99)
- Africa > Nigeria > Gulf of Guinea > Niger Delta > Niger Delta Basin > North Formation (0.99)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Differential vs. effective pressure Rock properties are controlled by a combination of Brandt (1955) was one of the first to observe a differences confining and pore pressure as defined by the effective between differential and effective pressure Later, Fatt 1958 stress law. The existence of effective pressure coefficients and Todd and Simmons, 1972, Christensen and Wang, is very well known but rarely accounted for. A rock under 1985, and Hornby 1996, showed results for different rock confining pressure and with a fluid inside will respond to types. The investigations showed a direct relation between changes of the pressure / stress conditions depending on the porosity, high differential pressure and the effective frame structure of the rock, porosity, and compressibility of pressure coefficient.
ABSTRACT Intrinsic dispersion and attenuation of shales is investigated by means of multiscale and multifrequency measurements acquired on a West African shale. Results show that shales may exhibit dispersion and attenuation peaks in spite of the very low permeability. The observed frequency dependent behavior of the elastic parameters of shales has a primary impact in the sonic to ultrasonic band, while it is roughly constant for seismic frequencies. The multiscale and multifrequency nature of the inverstigation, which measures variable volumes of shales, indicates that shales are homogeneous albeit dispersive materials.
ABSTRACT Seismic attenuation and dispersion can be caused by numerous distinct mechanisms. Observed or proposed mechanisms include mineral surface-fluid interaction, microscopic squirt between pores, macroscopic fluid motion between heterogeneous regions, and bulk loss within the fluid phase itself. The lack of an understanding of these various processes renders interpretation of attenuation-related attributes problematic at best. Direct measurement of seismic attenuation (1/Q) and velocity dispersion in the laboratory help discriminate among these mechanisms and ascertain which dominate for particular lithologies or saturation conditions. Fluid motion is a primary mechanism in porous, permeable clastics. In shales, however, bulk fluid motion is inhibited and clay particle interaction with bound water may dominate. Heavy, viscous fluids themselves show bulk losses independent of a rock matrix. All these loss mechanisms are frequency dependent, so observations of 1/Q made at seismic frequencies usually will not agree with sonic log measurements, which, in turn, will not agree with ultrasonic data.
Values of Mineral Modulus of Clay
Prasad, Manika (Colorado School of Mines) | Hofmann, Ronny (Colorado School of Mines) | Batzle, Michael (Colorado School of Mines) | Kopycinska-Müller, M. (Fraunhofer Institute for Nondestructive Testing, IZFP, Saarbrücken) | Rabe, U. (Fraunhofer Institute for Nondestructive Testing, IZFP, Saarbrücken) | Arnold, W. (Fraunhofer Institute for Nondestructive Testing, IZFP, Saarbrücken)
ABSTRACT Seismic wave propagation in geological formations is altered by the presence of clay minerals. Knowledge about the elastic properties of clay is therefore essential for the interpretation and modeling of the seismic response of claybearing formations. However, due to the layered structure of clay, it is very difficult to investigate its elastic properties. We measured elastic properties of clay using atomic force acoustic microscopy (AFAM).The forces applied during the experiments were not higher than 50 nN. The adhesion forces were measured from the pull-off forces and included into our calculations by means of the Derjaguin-Mueller-Toporov model for contact mechanics. The obtained values of the elastic modulus for clay varied from 10 to 17 GPa depending on various parameters that describe the dynamics of a vibrating beam.
- Geology > Mineral > Silicate > Phyllosilicate (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)