January-February 2000
Volume 1 No. 1

Interpreting Neutron Logs in Horizontal Wells: Forward Modeling Tutorial

Darwin V. Ellis and Joseph M. Chiaramonte
 

ABSTRACT
This tutorial illustrates the benefits of modeling compensated neutron logging instrument responses. Recent progress has been made with speeding up model computations using a forward model based on diffusion theory. The commercially available modeling code, PC2, is applied to understanding and explaining the responses of neutron tools in horizontal wells. For examples, the influence and detectability of beds below and adjacent to the horizontal wellbore and the effects of non-axisymmetric invasion profiles are examined.

Estimation of Oil Viscosity with Multiple TE Dual Wait-Time MRIL Logs

Songhua Chen, Daniel T. Georgi, Eric M. Withjack, Carlos Minetto, Oscar Olima, and Hector Gamin
 

ABSTRACT
Samples of reservoir fluids are typically obtained from expensive well tests, drill stem tests, or downhole fluid samplers. There is always the concern that these samples may not be representative of the in situ reservoir fluids, and introducing uncertainty in determining critical parameters for reservoir exploitation and economic evaluation. The ideal solution would be complete downhole analysis of in situ fluids. We present a case study using multiple TE dual wait-time (TW) log acquisitions for quantitative characterization of San Jorge Basin reservoir oil viscosity. The NMR-based estimates were verified with a follow-up PVT test and confirmed with production data. We demonstrate that, with an effective separation of oil and water NMR signals and the appropriate estimation of intrinsic relaxation time, NMR logging tools can satisfactorily provide in situ oil viscosity.