The lower Tyler Formation of central Montana is oil productive from sinuous, point-bar sands deposited in a Pennsylvanian river channel. These hydrocarbon-bearing bars are hard to locate, and successfully offsetting a discovery is commonly difficult.

Combining the dipmeter with subsurface data and sample cutting studies is a method that will eliminate some dry holes.

Subsurface data indicate the location of the channel, the amount of erosion into underlying beds, and the type of channel fill. Sample cuttings show the type of bar facies found. The dipmeter illustrates the water-sediment transport direction and the deviations of dip within each facies change.

These 3 tools used together will produce a more accurate subsurface picture to determine which offsetting location will produce a field extension.

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