J. V. S. S. Narayana Murty
J. V. S. S. Narayana Murty obtained his Ph.D. in physics from IIT, Madras. He joined the Oil and Natural Gas Corporation (ONGC) as a geophysicist and gained knowledge in seismic and G&G software development skills. He was adjudged as Geophysicist of the Year in 1989. For his contributions in induction of new technologies and R&D efforts, he received the National Mineral Award 2001 from the government of India and Corporate Innovation Award from ONGC. He gives a regular course on migration and velocity modeling at ONGC Academy. He was an editorial member and reviewer, Society of Petroleum Geophysicists (SPG), India and gave a continuing-education course on seismic interferometry/passive seismic at SPG 2013. He delivered lectures at Anna University, IIT Madras, and to faculty and research scholars of universities in northeast India. He was an accredited mentor in ONGC and trained many geoscientists on the use of interpretation software on workstations. During his tenure in ONGC, he inducted many technologies such as 3D survey preplanning for recovering offsets, sequence attributes, coherency, time-dip and azimuth cubes (ONGC Copyright 2001), spectral decomposition, RGB color mapping, quantitative approach for QC of seismic data acquisition and processing, removal of acquisition footprints, reorientation and merging of overlapping 3D seismic data (SPE 2000), poststack cross-line statics, and 2D forward modeling using GPUs. He guided development of plug-ins to Landmark, Petrel, Omega and the then WGC and GECO processing software. He is actively engaged in teaching and participating in R&D and G&G software development as a domain expert for ONGC and consultant for Gujarat Energy Research and Management Institute. He conducted a workshop in 2015 along with Dr. DVR Murty on acquisition, processing, and interpretation at the SEG student chapter, IIT Bombay. As visiting faculty for 2016, he taught basic geophysical concepts and applications of seismic data in reservoir description at the petroleum engineering department of Rajiv Gandhi College of Engineering, Chennai.
2017 SEG Honorary Lecturer, South and East Asia
Passive seismic tomography (PST), QC, and application of PST-derived velocity for seismic imaging
Passive seismic tomography (PST) method uses both P-wave and S-wave travel times from naturally occurring low-intensity earthquakes recorded over a period of time. The data of selected good seismic events are collected to derive 3D VP and VP/VS models of the area in addition to finding active fault locations and local tectonic stress distribution.
Due to low cost and relative ease in operation, PST has made inroads into hydrocarbon exploration, especially in difficult terrains, by inferring structural and lithological information from the VP and VP/VS volumes as well as incorporating the velocity models in seismic imaging projects in areas of poor quality seismic data where determining the initial velocity is difficult.
The success of PST depends on the natural seismicity in the area and sufficiency of data recorded for estimating depths of the hypocenters and velocity fields using tomographic inversion. In the process of tomographic inversion, errors get accumulated to those grid cells through which adequate raypaths do not traverse and leads to uncertainty in the estimations. These can be reduced only by recording additional events (more time) and or at additional stations that contribute to the grid cells with less ray coverage. Therefore, the results are to be quality controlled and carefully evaluated.
In this lecture, the concepts of passive seismic tomography will be detailed and a field example will be presented to understand the limitations of PST using natural earthquakes. Various QC measures and conditioning of PST velocity field will be discussed with examples to infer better structural information and use PST velocity as an initial model for reprocessing in seismic imaging.