R. Strickland, R. Chemali, S.M. Su, and S. Gianzero
Halliburton Logging Services, Austin
J. Klein and S. Sakurai
ARCO Oil and Gas Company
M. Walker
Halliburton Logging Services, Anchorage
ABSTRACT
A new deconvolution algorithm has been developed for High Resolution Induction logs to further improve their response under nearly all logging conditions. While logs run in recent years have confirmed the overall capability of HRI to produce a deep, sharp and well resolved induction measurement, the original deconvolution algorithm is sometimes inadequate in the presence of caved boreholes or magnetic formations.
A detailed analysis of the HRI logs under those adverse conditions was conducted using the elementary in-phase and quadrature components of the signal (also called R and X-signals respectively). Conductive caves showed characteristic responses on the R-signal, while magnetic muds or formations affected primarily the X-signal. All observations were confirmed and quantified by mathematical modeling. The analysis lead to the development of a new adaptive deconvolution algorithm, including an optional cave correction, that deals successfully with all the above situations.
A demonstration of the new deconvolution is given on simulated logs as well as actual field logs. The overall performance of the tool is preserved for normal conditions and vastly improved in the adverse situations cited above. Only a small degradation of the vertical resolution is observed in conductive borehole wash-outs. With the new deconvolution, magnetic minerals such as hematite or siderite do not affect appreciably the HRI conductivity log. Furthermore, the primary X-signal delineates thin siderite intervals with vertical resolution similar to the conventional spectral (litho)-density log.