Optimization of NMR Data Utilization on Valhall - a Brown Chalk Oilfield
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The Valhall field started production in 1982 and has been producing since. A vast amount of data has been gathered and interpreted since then. Because of its complexity, there are still many questions left unanswered. Some are questions related to the water flooding system; in-fill wells are drilled, and logging data detects unexpected water. Where does the water come from and why? Others are related to the confidence in estimated target parameters such as water saturation, porosity and permeability. Can this data contribute to increase the confidence in them? Valhall is a brown chalk field. It is a complex, mature field and consists of tight, fractured chalk. Successful reservoir management requires good understanding of the reservoir and the data. The Nuclear Magnetic Resonance is a fairly old technology and is well understood. It has a great potential of providing useful information along the wellbore. Data have been acquired from the reservoir but the applications in the Valhall reservoir management has not been exploited to its full potential. It has been used as a secondary source of porosity and saturation and used if no other source of such information has been available.The objective of the present study is to optimize the utilization of NMR data on Valhall through investigation of the current applications and possible additional applications. Investigations are done on the data quality, porosity, fluid saturations, permeability and the possibility of improving the understanding of water flooding. Moreover parameters are optimized to better fit conventional logs. Its applicability for well placement and Geosteering are discussed. The results lead to the conclusion that data is useful, trustworthy, and recommended for use in future operations. The extra information NMR provides regarding bound and movable water is added value and very useful in waterflood surveillance. NMR data provides important information about key reservoir properties.