Date of Graduation
Eberly College of Arts and Sciences
Geology and Geography
Hydrocarbon exploration in unconventional reservoirs is highly risky due to the nature of the reservoirs and the variability in fractures and reservoir geomechanical properties in the subsurface. The reservoir needs to be fully characterized to avoid any complication such as frac hit, wellbore failure, blowout, or even a dry hole. The Clearfield reservoir produces an exceptionally low amount of gas, compared to the neighboring region in the proximity, which has been poorly understood. This raises the question as to what causes the reservoir to have low productivity.
This study focuses on the natural fracture characterization using high-quality 3D seismic signal attributes. The structural discontinuities of this unconventional reservoir are characterized using multiple 3D seismic attributes such as maximum curvature, ant-tracking, and sweetness. Maximum curvature attributes allow us to visualize the intensity of the faults and fractures. This study finds that the Marcellus Shale horizon has the most intense faults with no preferred orientation. Ant-tracking is another useful attribute in determining the potential path for hydrocarbon migration. It detects and traces the connecting fractures known as fracture swamps. It is proven that this reservoir is dominated by high angle faults and fracture swarms, which may have contributed to its low productivity.
Well log data is incorporated in order to calibrate with the seismic data. Young’s Modulus (YME) and Poisson’s Ratio (PR) values are measured based on the sonic logs. The ratio of YME and PR are then calculated from one of the horizontal wells to obtain the brittleness value of the Marcellus Shale. This study finds that within the Marcellus Shale horizon, the geomechanical properties and brittleness values vary due to the abundance of faults and fractures. The Marcellus Shale in this reservoir is in fact anisotropy. In addition to that, the complex fracture networks in the Clearfield gas field could be detrimental to the reservoir integrity, thus lowering the gas productivity.
Zulkapeli, Iman F., "Application of 3D Seismic Signal and Geomechanical Attributes for Subsurface Fracture Characterization: A Case Study in Clearfield County, Central Pennsylvania" (2021). Graduate Theses, Dissertations, and Problem Reports. 8042.