Application of Well Log Tomography to the Dundee and Rogers City Limestones, Michigan Basin, U. S.

Le, Mellisa¹, James R. Wood¹, Albert S. Wylie, Jr.¹, and William. B. Harrison III^2
1 Department of Geological & Mining Engineering and Sciences, Michigan Technological University, Houghton, MI
² Department of Geosciences, Western Michigan University, Kalamazoo, MI

Well log tomography, formerly log-curve amplitude slicing, is a visualization method recently developed at Michigan Technological University to correlate subsurface data by utilizing the high vertical resolution of well log curves. The well log tomography method was first successfully applied to the Middle Devonian Traverse Group using gamma ray log curves. The purpose of this research was to prepare a digital data set for the Middle Devonian Dundee and Rogers City Limestones, apply the well log tomography method to this data and interpret trends in the natural radioactivity. Differences between this study and the Traverse Group study include increased well control and "slicing" of a uniform lithology.

Gamma ray log curves for the Dundee and Rogers City Limestones were obtained from 295 vertical wells distributed over the Lower Peninsula of Michigan, converted to LAS files, and input into the well log tomography program. The "slicing" contour results indicate that during Dundee and Rogers City time, carbonates and evaporites with low natural radioactive signatures on gamma ray logs were deposited. In contrast, siliciclastic deltas cyclically entered the basin during Traverse Group time. A subtle north-south, low natural radioactive trend was discovered that may correlate with previous studies of Dundee facies tracts. Prominent trends associated with the distribution of limestone and dolomite are not observed because the regional range of gamma ray values for these carbonates are equivalent in the Michigan Basin and additional log curves are needed to separate these lithologies.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004