Date of Award
Open Access Thesis
Earth and Ocean Sciences
College of Arts and Sciences
The lower Permian formation in the central region of Saudi Arabia is a key hydrocarbon siliciclastic reservoir. However, in Majhol field, the reservoir properties vary laterally due to diagenesis and facies changes. Conventional seismic interpretation has failed to map the heterogeneities of the reservoir properties that control the gas production of this field. Therefore, there was an opportunity to employ more advanced quantitative seismic techniques to delineate the productive gas sand facies in the field.
The Majhol field was initially planned to be developed as an unconventional tight reservoir. Well-1 was drilled based on conventional seismic interpretation on the crest of a four-way dip closure structure. Well-1 produced low rate hydrocarbon gas from the Lower Permian formation and it showed a poor reservoir quality due to diagenesis that highly affected the reservoir porosity and permeability. Well-2 was drilled on the flank of the structure to delineate and develop the field as unconventional tight reservoir. However, Well-2 showed an excellent reservoir and it successfully flowed gas and condensate naturally at high rate.
Here, a 3D quantitative seismic study was performed through amplitude vs. offset (AVO) analysis and impedance inversion techniques with constraints from the well data to delineate the properties of the reservoir and detect the productive gas sands. Seismic attributes derived from this study consistently delineated the gas sand facies as class 2 AVO anomaly. Although this study shows that the gas charged sand reservoir was thick enough to be resolved with the conventionally acquired seismic data in the vicinity of Well-2, this layer does not seem to extend laterally all the way to Well-1, therefore the differences in gas production between the two wells.
Alhashel, A.(2016). Delineation Of The Lower Permian Gas Sand Via Calibrated Avo And Pre-Stack Seismic Inversions In Majhol Field, Saudi Arabia. (Master's thesis). Retrieved from http://scholarcommons.sc.edu/etd/3941