Rock physics template (RPT) analysis of well logs and seismic data for lithology and fluid classification in Cambay Basin

Abstract

The Cambay Basin is 450-km-long north-southtrending graben with an average width of 50 km, having maximum depth of about 7 km. The origin of the Cambay and other Basins on the western margin of India are related to the break up of the Gondwana super-continent in the LateTriassic to Early-Jurassic (215 ma). The structural disposition of the Pre-Cambrian basement-a complex of igneous and metamorphic rocks exposed in the vicinity of the Cambay Basin-controls its architecture. The principal lineaments in the Basin are aligned towards NE-SE, ENE-WSW and NNW-SSE, respectively. Rock physics templates (RPTs) are charts and graphs generated by using rock physics models, constrained by local geology, that serve as tools for lithology and fluid differentiation. RPT can act as a powerful tool in validating hydrocarbon anomalies in undrilled areas and assist in seismic interpretation and prospect evaluation. However, the success of RPT analysis depends on the availability of the local geological information and the use of the proper model. RPT analysis has been performed on well logs and seismic data of a particular study area in mid Cambay Basin. Rock physics diagnostic approach is adopted in the study area placed at mid Cambay Basin to estimate the volume in the reservoir sands from 6 wells (namely; A, B, C, D, E and F) where oil was already encountered in one well, D.In the study area, hydrocarbon prospective zone has been marked through compressional (P wave) and shear wave (S wave) impedance only. In the RPT analysis, we have plotted different kinds of graphical responses of Lame's parameters, which are the function of P-wave velocity, S-wave velocity and density. The discrete thin sand reservoirs have been delineated through the RPT analysis. The reservoir pay sand thickness map of the study area has also been derived from RPT analysis and fluid characterization. Through this fluid characterization, oil-bearing thin sand layers have been found in well E including well D. The sand distribution results prove that this methodology has able to perform reservoir characterization and seismic data interpretation more quantitatively and efficiently.

Experimental Study on Petrophysical Properties as a Tool to Identify Pore Fluids in Tight-Rock Reservoirs

“…Based on these models, rock-physics templates (RPTs) can be used to estimate porosity and saturation (Liu et al, 2015;Pang et al, 2019Pang et al, , 2020. Studies showed that RPTs, built with acoustic impedance and P-to S-wave velocity ratio, serve as tools for lithology and fluid identification (Chi and Han, 2009;Datta Gupta et al, 2012;Ba et al, 2013). RPTs based on seismic attenuation also describe the effect of partial saturation, porosity, and permeability (Dvorkin and Mavko, 2006;Picotti et al, 2018).…”

Capture the variation of the pore pressure with different geological age from seismic inversion study in the Jaisalmer sub-basin, India

“…The workflow mentioned above (chart diagram) is showing one significant aspect for seismic inversion study. In this workflow, we could observe the presence of LFM and ULFM (Datta Gupta et al 2012).…”

Microcrack Porosity Estimation Based on Rock Physics Templates: A Case Study in Sichuan Basin, China

“…Michel [22] predicted porosity and oil saturation in shales, based on RPTs built with P-wave impedance (I P ) and the ratio between the P-and S-wave velocities (V P /V S ). Gupta et al [23] identified thin sandy layers saturated with oil, and Ba et al [24] estimated porosity and gas saturation. Carcione and Avseth [25] evaluated organic content, hydrocarbon saturation, and in-situ pressure in source rocks, and Liu et al [26] proposed a combination of fluid indicators.…”