Rock Physics Study of Lacustrine Shales and Applications in Geophysical Prediction of Sweet Spot

Rock physics analysis is crucial in bridging seismic data with reservoir properties. Although shale oil reservoirs are considered to be significant hydrocarbon resources, their exploration and extraction still pose challenges, especially in lacustrine shale environments. I conducted a comprehensive rock physics study and predicted sweet spots in the lacustrine shale reservoir in the Songliao Basin. First, I characterized the porosity, maturation, pore structure, and pore fluid phases of the samples for reservoir evaluation using helium porosimetry, X-ray diffraction (XRD), Rock-Eval pyrolysis, vitrinite reflectance analysis, scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) on the collected shale samples. Secondly, I conducted systematic laboratory measurements for acoustic properties, including seismic (2-200 Hz) and ultrasonic frequency (10^6 Hz) measurements under different saturation and effective pressure conditions. I found that velocities at the seismic frequency and the ultrasonic frequency of reservoir samples possess significant transverse-isotropy type anisotropy and velocity dispersion and attenuation. Furthermore, I synthesized the geological and discussed physical mechanisms to explain my measured data and observation. The anisotropy of the lacustrine shale is primarily caused by oriented clay minerals, fractures resulting from hydrocarbon generation, and lamination structures. The velocity dispersion and attenuation are also orientation-dependent, interpreted to the viscoelastic behavior of the clay and clay-bound water composite in the lacustrine shale. Using the experiment data, I built a rock physics model to explain the velocity anisotropy, velocity dispersion, and attenuation of shale. In my studied area, I discovered that the shale oil sweet spot is characterized by high values of clay content, Total Organic Carbon (TOC), pore pressure, gas-to-oil ratio, and API gravity. These factors correlate with high anisotropy, high dispersion, and attenuation, as well as low P-wave and S-wave impedance. Through analysis of field well and seismic data, I observed that the anisotropy and dispersion measured at the core scale are also present at the seismic scale. I concluded that the P-wave anisotropy parameter epsilon could be a robust indicator for shale oil sweet spots. My findings were subsequently validated by drilling activities based on seismic inversion for epsilon in the study field.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Geophysics

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Long, Teng

Advisor dc:contributor.advisor

• Zheng, Yingcai

Committee members dc:contributor.committeemember

• Han, Dehua
• Li, Aibing
• Zhang, Zhao

• Rock physics
• Shale
• Attenuation
• Anisotropy

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/17764

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/17764