SUB-BASALT CHALLENGES AND PROCESSING OF LONG OFFSET SEISMIC DATA

Abstract

Long offset seismic data acquired with source receiver offset greater than the depth of curiosity, lighten the subsurface differently from conventional short offset data and therefore contain extra information about the earth. In western off shore of India, Mesozoic sediments are roofed by basaltic flows of Deccan trap. It is expected that below these basaltic flow, Mesozoic sediment containing hydrocarbons may be present. Inhomogeneous basalt bases very serious scattering and constrains seismic energy to enter through it. Its high velocity gap with overlying younger sediments limits the seismic wave energy penetration at small offsets whereas wide angle reflections . record brings surplus challenges for processing and imaging. Stretching is a challenging problem in such type of long offset recorded data because after stretching, applying mute will be only option due to which useful information will be lost. For removing the multiples the tools like surface related multiple elimination (SRME) and parabolic radon transform has been used. SRME has worked well at nearer offset while at longer offset parabolic radon has shown outstanding result. The stack section of processed data in such a way shows greater potential for interpretation of sub surface structure and lithology.