Oil & Natural Gas Projects
Exploration and Production Technologies
Seismic and Rock-Physics Diagnostics of Multiscale Reservoir Textures
The main objective of this project was to quantify rock microstructures and
their effects in terms of elastic impedances in order to quantify the seismic
signatures of microstructures. One special focus was to understand how sub-resolution
heterogeneities affect observable seismic signatures.
Acoustic microscopy and ultrasonic measurements were used to quantify microstructures
and their effects on elastic impedances in sands and shales.
The main benefit of this project was the development of key technologies for
quantitatively interpreting seismic images and the linkage of seismic data with
geologic models to estimate reservoir properties. For the public, ultimately,
better technologies for reservoir characterization translates to better reservoir
development, reduced risks, and hence reduced energy costs.
Attempts to relate microstructural properties and reservoir properties controlled
by microstructure to seismic data have been problematic. One problem is that
microstructure is difficult to quantify geometrically and elastically. This
problem is addressed in this project by measuring, analyzing, and quantifying
the impedance microstructure of sands and shales at pore-scale resolution and
analyzing their relations to corresponding measurements of seismic properties.
Over 250 scanning acoustic microscope images of impedance microstructures in
shales were analyzed quantitatively. Relations were obtained between textural
heterogeneity and anisotropy, and shale maturation and kerogen content. Consistent
measurements of elastic moduli of clay minerals using ultrasonic methods and
acoustic force microscopy were obtained. It was found that theoretical models
give better predictions when the new measured values of clay were used. Empirical
velocity-pressure and porosity-pressure trends were developed from P- and S-wave
ultrasonic measurements on unconsolidated sands. Trends such as these are critical
for better understanding and predicting the hazards posed to offshore drilling
by unknown overpressures at shallow depths.
Project accomplishments include:
- Studies on the effects of sorting, compaction, and stratification in sediments
on the Vp and Vs seismic signatures.
- Quantitative acoustic microscopy study of textures for reservoir rocks.
- Nanometer-scale measurements of elastic properties of clay.
Current Status (June 2006)
The project has been completed..
Scanning acoustic microscope image of elastic impedance textures in shales
(top) and corresponding 2-D autocorrelation function (right). The shape of
the autocorrelation function can be used to quantify textures in rocks.
Project Start: September 17, 2001
Project End: June 30, 2005
Anticipated DOE Contribution: $ 450,000
Performer Contribution: $115,000 (20% of total)
NETL - Chandra Nautiyal (firstname.lastname@example.org or 918-699-2021)
Stanford U. - Gary Marko (email@example.com or 650-723-9438)
Vega, S., 2003, Intrinsic and stress-induced velocity anisotropy in unconsolidated
sands, Ph.D. thesis, Stanford University (http://srb.stanford.edu/Theses/theses04.html)
Zimmer, M., 2003, Controls on the seismic velocities of unconsolidated sands:
Measurements of pressure, porosity and compaction effects, Ph.D. thesis, Stanford
Prasad, M., and Mukerji, T., Analysis of microstructural textures and wave
propagation characteristics in shales, SEG Exp. Abstr., 73rd Ann. Intl. Mtg.,
Vega, S., Mukerji, T., Mavko, G., and Prasad, M., Stratification in loose
sediments and its seismic signature, SEG Exp. Abstr., 73rd Ann. Intl. Mtg.,
Vega, S., Prasad, M., and Mavko, G., Comparative study of velocities under
hydrostatic and nonhydrostatic stress in sands, SEG Exp. Abstr., 73rd Ann.
Intl. Mtg., 2003.
Vanorio, T., Prasad. M., and Nur, A., Elastic properties of dry clay mineral
aggregates, suspensions, and sandstones, Geophys. J. Int., 155, 2003, pp.
Prasad, M., Reinstaedtler, M., Nur, A., and Walter, A., Quantitative Acoustic
Microscopy: Application to petrophysical study of reservoir rocks, Acoustical
Imaging, 26, 2002, pp. 493-502.
Prasad, M., Kopycinska, M., Rabe, U., and Arnold, W., Measurement of Young's
modulus of clay minerals using atomic force acoustic microscopy, Geophys.
Res. Lett., 29, 2002, p. 1238.
Zimmer, M., Prasad, M., and Mavko, G., Empirical velocity-pressure and porosity-pressure
trends in unconsolidated sands, SEG Exp. Abstr., 72rd Ann. Intl. Mtg., 2002.
Zimmer, M., Prasad, M., and Mavko, G., Pressure and porosity influences on
Vp-Vs ratio in unconsolidated sands, The Leading Edge, V. 21, No. 2, 2002,