Understanding the Deformation of the Naga Thrust Triangle Zone, NE India, using Structural Modeling of 2-D Seismic Data

Michael, Brandy B.; Shukla, Khemraj; Burberry, Caroline M.; Jaiswal, Priyank

Seismic interpretation of structures associated with complex zones can be tested for viability using multiple methods. Combined methods of multiscale waveform inversion and prestack depth migration provide a two-step process to describe large wavelength and small wavelength features in the same image. This provides a detailed base image for balanced reconstruction of a cross section. The processed seismic line created in this study was interpreted and restored to provide a mechanically feasible model for the Naga Thrust Triangle Zone (NTTZ).

2-D seismic data was acquired in the central part of the Naga Thrust and Fold Belt (NTFB) in NE India. The study area is approximately 20 kilometers southwest of the Digboi oil field. The initial 2-D seismic data was imaged with a combination of traveltime inversion and prestack depth migration (PSDM). An improved image was acquired from a combination of multiscale waveform inversion and PSDM. The seismic line was interpreted using images from all stages of the processing and was restored using line length and key bed balancing techniques.

The cross-section created indicates minor deformation above the Naga thrust, via a series of back-thrusts, with a shortening of around 5% in this hanging-wall block. Beneath the Naga Thrust, within the triangle zone, several thrust blocks are interpreted, creating an antiformal stack similar to classic triangle zone structures in the Alberta Foothills, Canada. Overall shortening across this region is around 40%.

Structural interpretation in this study area provides insight into the geologic history, continued structural deformation and future hydrocarbon exploration of this region. Further study of migration and maturation may prove the potential of petroleum systems in sub-thrust features of the NTTZ. Large sub-thrust traps beneath the Naga Thrust are possible as shown in this restored cross section. This study provides insight into the use of traditional and non-traditional geological processing methods in combination with traditional structural methods. This inter-disciplinary approach can provide transformative insight for interpretation of previously constructed models.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013