Research
Dr. James J. Willis is an award winning researcher and has been the PI or Co-PI on several million dollars in grants from federal, state, and industry sources. Active research topics highlighted below include comparative structural geology, welding and suturing, shale distribution, and prestack seismic interpretation.
For more information, including possible collaborations, please contact info@applied-geoscience.com.
Comparative Structural Geology
A long-term research interest of Dr. Willis is on comparative structural geology, especially regarding basin and dome development and rock suturing. For example, the left image shows a bathymetric map of offshore Louisiana showing salt-cored ridges and adjacent salt-withdrawal basins (courtesy of Fugro) and the right image shows similar appearing magma-withdrawal basins, Valkarie Fossae, Venus (radar data courtesy of NASA; image flipped horizontally).
Structural deformation often exhibits a fractal (scale-independent) nature. In the example, three domes are shown each of different origins are scales but exhibiting remarkable similarity. At upper right is a Wilcox subsurface contour map associated with a salt dome, at lower left is a ft-scale laboratory model of doming, and at left is an inch-scale example in a laminated floor at a training facility in Seoul, Korea. Analytical modeling predicts disorganized normal faults at dome crest due to little variability between radial and hoop stresses but outwards transitions to radial normal faulting (hoop stress becomes the minimum stress), following by a circumferential syncline (or synclinal hinge). In a rather unusual circumstance, Dr. Willis was teaching a training course in South Korea on data integration and showed an earlier version of this slide as the final slide before the 1st break. In the breakroom he spied the small-scale dome (Korean won coin for scale) in the laminate floor (presumably a small piece of debris was present when the flooring was laid which subsequently caused the domal upward and deformation). He quickly inserted a picture and when resuming the course showed this revised slide illustrating further the often fractal nature of deformation.
Pressure dissolution is typically associated with bedding-plane stylolites in carbonates but can be manifested in other rock types and scales. The adjacent image shows a typical hand-specimen example of stylolites (top) and seismic-scale stylolites due to the dissolution of the Blaine Anhydrite, Las Animas Arch, Colorado (seismic data courtesy of TGS).
Shale Distribution Petrophysics
Dr. Willis and colleagues expanded shaly sand petrophysics to determine better shale distribution. Earlier models such as Thomas-Stieber and Juhasz considered only two-shale distribution models, namely laminar-dispersed and laminar-structural. Our analysis developed a three-shale distribution model which with standard triple-combination log data yielded two important end-member models (representing the range of possible effective porosity) and variations in between. With additional data such as image logs or 3D resistivity, actual three-shale distribution can be determined pinning down key parameters such as effective porosity and effective water saturation. Our group has won two awards related to this research—2018 GCAGS Best Student Published Paper (based on Greg Ferguson’s thesis on shale distribution controls pm effective porosity) and 2019 AAPG A. I. Levorsen Memorial Award for outstanding contribution to the oil and gas industry.
Welding and Suturing
Weld Types and Classification
Dr. Willis has been studying welds for over two decades, advancing the classification from previously-described salt welds to include other flow regimes (e.g., shale, tar, sand, igneous, and metamorphic) as well as dissolution regimes (e.g., evaporites, carbonates, and stylolites) with additional developmental factors, including faults, shear zones, and boudinage.
Grain-to-Grain Contact Deformation
Grain-to-grain contact deformation results from stresses generated by overburden, tectonic, or crystal-growth pressures, with resultant strain manifesting as internal grain fracturing, often initiating at the grain-to-grain point contact and propagating into and through the grain interior, or as suturing via pressure dissolution at the grain-to-grain contact. Key implications include loss of porosity and permeability but also anisotropy–for example, greater vertical stress in an overburden environment creates a faster vertical velocity (due to enhanced vertical porosity loss) versus the horizontal dimension (less porosity loss due to lower pressures). Dr. Willis and co-author Glenn Bixler was awarded the 2017 GCAGS Grover E. Murray Best Published Paper Award (2nd Place) for their work on this topic using the Collings Ranch Conglomerate of the Oklahoma Arbuckle Mountains as a key mesoscopic example of grain-to-grain suturing, which was featured on the cover of the GCAGS Transactions. Notice how certain clasts have interpenetrated into more-soluble clasts.
Weld Residuum
During the weld process, residuum may be left behind during flow or dissolution processes. For example, stylolite residuum, commonly clay minerals or quartz, is well known. During flow processes, frictional processes near flow boundaries reduce flow velocities and can leave behind some material forming an incomplete weld. The adjacent image is an example of log-scale residuum due to dissolution of an anhydrite layer (Blaine Anhydrite, Las Animas Arch, Colorado).Note in the highlighted region (2nd log from left) that the upper Blaine and lower Blaine evaporites have been removed by dissolution. Both evaporite layers contain a shale fraction which has been left behind as a residuum following the dissolution process. Consequently due to the similarity of the Blaine shale fraction to the underlying Flower Pot Shale, the residuum from the lower Blaine causes an apparent thickness increase in the Flower Pot Shale.
Prestack Seismic Interpretation and Attribute Analysis
The prestack seismic domain is most often associated with processing stages and AVO analysis and interpretation. However, there are additional interpretational aspects that can be applied. For example, the adjacent image shows residual velocity and clearly residual effects exist along faults thus allowing greater understanding of the three-dimensionality of faults and how they become “smeared” during the stacking process. Additionally, standard poststack interpretational attributes can be applied in the prestack domain; for example, instantaneous phase can enhance weak reflections to provide more control in a semblance velocity analysis.