SEISMIC FACIES ANALYSIS OF A PART OF A PETROLIFEROUS BASIN

Abstract

Twenty four seismic reflection sections of a sedimentary basin in India have been studied with a view to interpret sedimentat.ional environment. Based mainly on the seismic sequence analysis three sequences have been identified, namely sequence I, II and III. The present investigations are restricted to sequence II and III mainly, out of which sequence III (youngest one) was studied in detail. In these sequences different facies have been marked and interpreted. Sequence III was further divided into three units vertically.` In all these units based on the conspicuous presence of sigmoidal reflection configuration, study of seismic facies maps,. electrolog information, a deltaic environment has been predicted. Based on the reflection configuration, amplitude, continuity of seismic reflection traces, five seismic facie in all the three units of sequence III were observed. namely (i) the parallel/sub-parallel high-amplitude high-continuity fades. (ii) the parallel/sub-parallel high-amplitude low-continuity facies. (iii) the parallel/sub-parallel low-amplitude low-continuity facies. (iv) .hummocky clinoform facies. (v) progradational facies. v. In the sequence II three seismic facies namely (i) the parallel/sub-parallel variable-amplitude low-continuity facies. (ii) the parallel/sub-parallel low-amplitude low-continuity facies. (iii) the parallel/sub-parallel high-amplitude high-continuity facies have been identified. In these 'facies delta-front, prodelta and deep ueritic sub-environments were recognised. From the sand-shale ratio, sand percentage and isochronopach maps it is inferred that the sediments were supplied mainly from NE to SW. The strand line was to the southern part of the area of study. With the help of seismic fades maps, lithology, map showing area of antiformal folds, electrolog informations and geochemical study N and NE portions of the area were predicted to be the most prospective,. so far as hydrocarbon prospect is concerned.