Cumulative dip plot method

Abstract

It is usual for a well to encounter faults, unconformities and sequence boundaries along its depth. Identification of these features based on the scatter of the 'tadpoles' from the diplog data alone may be difficult. To assist this identification, a cumulative dip plot, a crossplot of bedding plane orientation against depth was used. This method involves plotting the cumulative bedding plane dip with their appropriate dip directions against depth. The dip directions were colour coded into four compass quadrants: north-east (0-90°), east-south (90-180°), south-west (180-270°) and west-north (270-360°). A simple layer cake bedding will produce a straight line and a single colour cumulative plot. It is usual for bedding dips magnitude and directions or both to change when passing through a fault or unconformity, and thus will be represented by points of inflection (discontinuity and perhaps change of colours). In this study, diplog data from two wells <Well A and B) in the Baram Delta Field was used in plotting two cumulative dip plots. Results were compared with the previously interpreted faults, unconformities and horizons (sedimentary cycle boundaries) based on other wireline log data (sonic, resistivity and gamma) and seismic data. Results of the two cumulative dip plots seem to be in agreement with the previous results. This method proves to be a useful supplement study especially in structurally complex areas.