Practical Application of NMR Logging in Carbonate Reservoirs

Abstract

This paper (SPE 51329) was revised for publication from paper SPE 38740, first presented at the 1997 SPE Annual Technical Conference & Exhibition, San Antonio, Texas, 5-8 October. Original manuscript received for review 7 October 1997. Revised manuscript received 1 June 1998. Paper peer approved 15 June 1998. Summary Nuclear magnetic resonance (NMR) data acquisition and interpretation in carbonate reservoirs is much more challenging than in sandstones, where it is a well-established technology. Heterogeneous porosity distribution, a broad range of pore sizes, a wide variety of complex textures, and low surface relaxivity combine to complicate the picture considerably. The successful practical application of NMR in these reservoirs requires the development of acquisition and interpretation techniques specifically suited to the task. In carbonate reservoirs dominated by intercrystalline or intergranular porosity, NMR can deliver accurate estimates of porosity, permeability, bound fluid volume, and residual oil saturation (ROS). In heterogeneous carbonate reservoirs more complex interpretation models are required, normally based on the integration of whole core and log data. NMR answer products, based on these new techniques, are presented and validated with core data and by comparison with other logging measurements. P. 438