Characterization of thin bed reservoirs of Linch area, Cambay Basin using complex trace transform method to enhance temporal resolution of seismic data
In the last few decades, the interest in thin hydrocarbon reservoirs has grown progressively justifying the great effort spent on developing techniques for quantitative interpretation of thin bed seismic response. The detection and resolution of reflections from thin layers are major problems in reflection seismic. Many a times it is difficult to precisely estimate the vertical and lateral extensions of a significant portion of discovered hydrocarbon reservoirs due to the thin layer effect. In Linch area of Cambay basin, the sands which are dispersed especially within Older Cambay Shale (OCS) are thin and discrete in nature and are not properly discernible on seismic, in particular at deeper levels; some of these sands hold commercial oil and gas. Even within shallower Kalol formation most of the sands are quite thin to be delineated by conventional seismic interpretation. A small part of Linch area comprising of six wells, namely, LN-A, LN-B, LN-C, LN-D, LN-E, LN-F has been taken up for this study (Figure 1). Log characteristics and corresponding seismic response for well LN-A shows that the sands which are dispersed especially within Older Cambay Shale (OCS) are thin and discrete in nature and are not properly discernible on seismic surveys, in particularly at deeper levels. Sands being thin, the seismic response is of composite nature arising out of several sand-shale alterations (Figure 2). Rock physics analysis based on well logs indicates the porous sands to be having impedance within the range of shale impedance, mostly towards higher order (Figure 3). Inversion using conventional approach turns out to be of no practical use. In this study authors have investigated the approach for thin reservoir evaluation through complex trace transform (CTT) method.