A Study of Miocene Depositional Sequences in the Northeastern Gulf of Mexico Using Seismic Amplitude Attributes and Well Data

The intent of this study was to evaluate the depositional patterns of terrigenous clastic sediments throughout the Miocene interval of an 1800 square mile study area in the northeastern Gulf of Mexico. Throughout the study, a specific methodology was used to identify the primary depositional features within the Miocene interval and pinpoint major sand deposits within the identified features. A 3D seismic survey, electric wells logs, and available biostratigraphic data were used to conduct the study. The Miocene interval was first divided into four distinct depositional genetic sequences bounded by maximum flooding surfaces. The sequences were interpreted and mapped throughout the 3D seismic volume. Based on their thicknesses, they were then further divided into several stratal sections that were each evaluated using the root mean square (RMS) amplitude attribute, a measure of the intensity of the seismic amplitude within the interval. The resulting RMS interval amplitude attribute maps identified specific depositional features as well as areas of heterogeneous lithologies consistent with the presence of increased sand concentrations. Isochron maps were then created in the areas on the RMS interval amplitude maps with distinct depositional features and superimposed over those interpreted features to identify relative thicknesses of the deposits. Lastly, stratigraphic cross sections using available well logs were generated in strike orientations across the interpreted deposits to determine gross interval thicknesses and net-to-gross sand concentrations. The results of the study revealed that most of the major clastic sediment deposition occurred within the older depositional episodes of the Miocene. These consisted of coarser grained deposits with increased overall net-to-gross sand percentages, which were typically deposited by turbidity currents as channel and levee systems and channel and lobe complexes. The younger depositional episodes were mud-dominated and consisted of both turbidity current and contourite deposits primarily along the base of the paleo-Cretaceous shelf