FLUID INCLUSION STUDIES IMPACT THE ECONOMICS OF PETROLEUM EXPLORATION AND FIELD DEVELOPMENT (Invited Presentation)

Fluid inclusions provide a vehicle to study both past and present-day fluids, which helps explorationists anticipate the subsurface distribution of hydrocarbon accumulations. This impact is facilitated by the development of high-throughput, automated instrumentation that can easily evaluate entire boreholes for trapped fluid content (e.g., fluid inclusions), mineralogy and elemental makeup.

The application of fluid inclusion analysis in conventional reservoirs is performed for the evaluation and derisking of petroleum system elements, including migration, paleo-charge, seals, proximity to undiscovered resources, and petroleum type and quality. For example, the 7219/9-1 well drilled in the Barents Sea in 1988 was abandoned as dry with shows. Fluid inclusion analysis of archived cuttings from this well in 2005 demonstrated that the stratigraphic section previously held a 300-m paleo-column of 34°–36^o API gravity oil and a separate gas column, both of which had leaked laterally and were interpreted from the data to still be accumulated in a reservoir in the area. The oil was sourced from the Upper Jurassic, and the gas from a separate petroleum system in the Triassic. Wax precipitation was anticipated to be problematic. These and other observations were validated by discovery of the Johan Castberg fields in 2011–2012.

The application of fluid inclusion technology in unconventional resource plays typically focuses on identifying the regional distribution, relative volume, and composition of fluids. Unlike conventional reservoirs, which can contain petroleum inclusions from paleo-events, fluid inclusions from tight self-sourced or proximally sourced reservoirs usually more closely reflect volatile phases that will be produced from the current reservoirs. The Permian basin provides a good example. The area is characterized by multiple potential targets for horizontal drilling and has a long history of vertical penetrations, often with comingled production. Fluid inclusions have been used to help identify and rank these prospective benches in terms of fluid volume, API gravity, and GOR, and also aid in identifying zones that are more likely to produce higher water cut, which is a significant development cost in the area.