ABSTRACT

The study of patterns of closely spaced dip computations throughout the length of continuous dipmeter surveys is producing greatly increased geological information in Mississippi wells. Structural dip (or regional dip if no structure is present) is the basic dip shown by the dipmeter. Superimposed on the basic dip are the dips resulting from faults, unconformities and local depositional features. These are generally greater than structural dips and in random directions.

Faults are most often shown by the increasing dip in the drag zone as the borehole approaches the fault plane from the downthrown side. Complex faulting over shallow ridges or domes may be distinguished by the change in dips between faulted blocks. Buried bars are detected in wells drilled on the steep slopes by the decreasing dips exhibited by the successive younger beds deposited above them. Other changes in dip enable the location of unconformities, most of these being reasonably easy to recognize, since they appear at the same general position in the geological column Cross bedding shows up as erratic dips within sands.

It is emphasized that detailed geological interpretations of the dipmeter survey require numerous closely spaced computations studied in relation to the well log.