Lierong Zhu

Date of Graduation

2013

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Timothy R Carr

Abstract

The organic-rich Marcellus Shale unit of Middle Devonian section in Appalachian basin currently is one of the most successful unconventional shale-gas reservoirs in the world because of the modern technology development including; advanced seismic imaging, hydraulic fracturing and horizontal drilling. This study extracts the geologic structure and discontinuity systems from seismic data in Taylor County, West Virginia to better understand the regional and local geologic setting with special emphasis on the orientation of structural features (e.g., folds, faults and joints) that can guide horizontal well drilling and fracture stimulation design.;A southwest-northeast synclinal fold was mapped in the northern part of seismic survey area and a parallel partial anticline in the southern part of seismic survey area. There is a crossstrike structural discontinuity (CSD's) crosses the northeast part of study area, which is orientating northwest-southeast and cuts from Cambrian-Knox Group to Upper Devonian-Elk Group. The thickness of Marcellus Shale interval across the study area is almost uniform (30 meters). There is only one seismically-visible reverse fault across the Marcellus Shale. But a large thrust fault crosses the Trenton Limestone, Reedsville Group and Juniata Group. Some detachment appears within the Rome Shale, and Beekmantown, Reedsville, Juniata and Elk groups. Detachment was not observed in the Salina Group. Discontinuity attributes were used to extract the discontinuity system from seismic data. Attributes used includes variance, chaos, dip deviation, 3D curvature and Ant tracking. The 3D curvature attribute images the discontinuity feature within the Hamilton Group, which matches the geologic structure contour lines of Hamilton Group. The Ant tracking attribute shows the orientation and distribution of discontinuities across the study area, which almost match the geologic structure contour lines of Hamilton Group. Furthermore, the Ant tracking of Marcellus Shale displays a fabric, which strongly indicates two regional joint sets, earlier J1 crosscut by later J2 sets. As measured from Ant tracking, the J1 set is orientated approximately N52E, and the J2 set is trending around N45W. There is a low angle between the J1 set and the maximum compressive normal stress of the contemporary tectonic stress field (S Hmax).;Similar to other parts of the Appalachian basin, horizontal drilling should be N38W and perpendicular to the J1 set to cross and utilize the joints to guide fracture stimulation. There are areas of crosscutting N45W discontinuities that are interpreted as fracture swarms, which is related to cross-strike structural discontinuity structures. These areas may form reservoir barriers or areas where hydraulic fracturing could be ineffective due to energy largely loss along faults and open fractures.

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