Developing a fundamental understanding of how oil impacts diagenesis and the effect in transport properties by investigating rock samples from close to the oil-water contact, Ben Nevis formation, Hebron field.

Mujica, Francis (2019) Developing a fundamental understanding of how oil impacts diagenesis and the effect in transport properties by investigating rock samples from close to the oil-water contact, Ben Nevis formation, Hebron field. Masters thesis, Memorial University of Newfoundland.

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Abstract

There is ongoing debate as to whether or not oil emplacement in a reservoir rock impedes or stops diagenetic process. The Ben Nevis reservoir in the Hebron Field, offshore Newfoundland has a short transition zone and a clearly identified oil-water contact (OWC). Rock samples from above and below the OWC were used to analyse the role of oil emplacement in the diagenetic processes, with the main focus on quartz overgrowth and its impact on transport properties. The main contributions of this work is that we challenge the debate on whether or not oil emplacement impacts diagenesis for the Hebron Field, a relatively shallow, low temperature reservoir (< 2 km depth, 50-70 °C) using pore size distribution instead of a singular porosity value, and digital rock analysis for the transport properties. Core analysis includes scanning electron microscopy, mineral liberation analysis, cathode-luminescence, mercury injection capillary pressure (MICP), microcomputed tomography scans, and digital rock analysis and simulations. Our results suggest that quartz cement tends to be more abundant towards the water leg. This observation is in agreement with the “oil emplacement retards diagenesis” theory discussed in the literature. Despite differences in quartz overgrowth, the pore size distributions (MICP results) and digital rock images do not reveal any significant differences in the pore structures above and below the OWC. This could indicate that the differences in quartz overgrowth is not substantial enough to cause a significant reduction of the pore size, and thereby impact transport properties.

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