Strike Line Methodology As An Optimization To Exploring In Fold And Thrust Belts

Abstract

Exploring in the Argentina-Bolivia sub-Andean Belt, we routinely use a strike line methodology to optimize the seismic acquisition effort and improve subsurface imaging. The main component of this methodology is to divide the exploration effort into two phases. In the first phase, we shoot a regional strike line along the backlimb of a fold (as defined by the surface geology). We have found that seismic data has the best signal to noise ratio in these Tertiary valleys, where the terrain is also least severe. During the second phase we shoot dip lines, and usually a forelimb strike line, over any apparent culmination identified on the backlimb strike line. In this way we avoid unnecessary acquisition in the most expensive and worst data terrain. In defining a prospect, we have developed a circular interpretation process of creating balanced crosssections, forward modeling the seismic response, and choosing those models that best fit the real seismic. This process constrains and validates the structural interpretation but does not produce a unique solution. Interpretations are completed on non-migrated stack data on all lines since this is the only domain in which the strike and dip lines tie. The time structures are mapmigrated which shifts the location of the culmination spatially and collapses their size. The end result is a depth map that honors all geologic and geophysical data. The strike line methodology improves data quality and reduces overall exploration cost. We believe it to be a very efficient method for prospect generation.