A simple method of determining sand/shale ratios from seismic analysis of growth faults; an example from upper Oligocene to lower Miocene Niger Delta deposits

A plot of fault throw vs. depth is a simple geometric tool that graphically represents strata thickness variations in growth-fault and growth-fold settings and has previously been used to infer fault kinematics. In this paper, we use it as a prediction tool for lithological change employing only seismic data. If growth faulting is a continuous process, intervals of shale deposition are recorded by unthickened units, while intervals of sand fill in topographic lows. The throw vs. depth plot easily allows depiction of unthickened and thickened sedimentary intervals from even rough seismic records and can therefore be used to predict sand/shale ratios. The method is here applied to a growth fault in the Niger Delta that affects Oligocene to lower Miocene deltaic deposits. Most shale intervals are identified, and the sand/shale ratios are predicted. We suggest that the method can be a valuable tool in oil exploration.