BAYU NUCLEAR MAGNETIC RESONANCE STUDY: COMMERCIAL APPLICATION OF APPLIED RESEARCH AND FIELD TECHNIQUES IN A GAS-CONDENSATE FIELD

Abstract

Nuclear Magnetic Resonance (NMR) technology was applied to assist reservoir characterisation of the gas-bearing sandstones in the Bayu-Undan Field, Zone of Cooperation, Area A Blocks 91–12 and 91–13. NMR logs were run in several wells and laboratory NMR measurements on water-saturated core plugs were used to determine the sandstone pore structure and characterise effective porosity and permeability in the gas-bearing sands.

These sandstones exhibit a range of pore size behaviour, ranging from those sandstones with no clay-bound water to those with a significant proportion of their porosity associated with micropores. Mean relaxation times tend to be slower than expected for the observed pore sizes in these sands by comparison with global analogs. Surface relaxivity is lower than the world-wide average for sandstones, and reflects a network of unusually clean pore- walls.

Comparison between core permeability values and the log-estimated permeabilities over a four-order of magnitude range produces a correlation coefficient of greater than 0.7 in a single well.

Integration of field- and laboratory-based NMR data proved that permeability and pore-size distribution models could be integrated with conventional core analysis results. These datasets are continuous over the reservoir interval and once calibrated are easily integrated into reservoir simulation models.