Time-Depth Modeling in High Pore-Pressure Environment, Offshore East Coast of India

Abstract

Time-depth conversion becomes challenging in a complex geological environment. This study investigates plausible models between depth and interval velocity in a high-pressure depositional environment. The VSP data of six wells from three basins in the offshore East Coast of India have been analysed to estimate the high-pressure boundaries, depositional breaks and lithological boundaries. The time-depth modelling to understand the high-pressure environment has been tested on four models: a) the linear interval velocity model in depth, b) the linear interval velocity model in time (TWT), c) the average velocity model in time (OWT) and d) the exponential interval velocity model in time (OWT). A decrease in interval velocity evident on well data is utilized for identification of high-pressure boundaries on seismic data accurately only if, it provides a consistent fit to both time-depth and velocity-depth data. The results indicates that the average velocity model in time (OWT) is the most suitable model among the four models tested in this work for time-depth conversion for high pore pressure environments in the offshore East Coast of India. It is recommended to use this analytical velocity model for derivation of normal compaction trend in this area for optimal time to depth conversion. From the analysis of additional data of different basins, it was observed that the velocity drop might not be always due to the presence of high pore pressure. It could also be due to the change in lithology or the presence of erosional boundaries.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016