Interpretation and pitfalls of A/B analysis applied to shallow gas exploration in Plio/Peistocene foreland basin, southwestern Taiwan

The biogenic gas potential of the submarine canyon systems of Plio-Peistocene foreland Basin, southwestern Taiwan

“…These minimum inverted impedance anomalies also posses the same character of a NE-SW linear distribution (Fuh et al, 2004b). The same linear geometry can be observed on the seismic amplitude anomaly with A/B > 5, which was interpreted as an unresolved incised valley head on the seismic section (Fuh et al, 2006). Trends of these seismic attribute anomalies are the same as those of the Kanhsiaoliao submarine canyons.…”

“…Yet those without channels can be as high as 30 Hz. The tuning effect caused by the frequency absorption of near surface channels was concluded to be a false A/B signal for hydrocarbon potential (Fuh et al, 2006).…”

“…The TOC values of samples from canyon fill are in general above 0.5% excluding those from the NW-SE trending Eurchungchi submarine canyons distributed near the Chiali paleo-high. To further enhance the resolution of the depositional sequence, high-resolution sequence stratigraphic interpretation of 5th order was applied to the logs of the Hsinying (Fuh et al, 2006) and the Kuantian gas fields (Figs. 8 and 9).…”

“…A is the amplitude of target horizon and B is the RMS amplitude from a time window representing the background strata. The A/B amplitude analysis was applied to 21 2D seismic lines in the study area, reprocessed for amplitude preservation (Fuh et al, 2006). A background time windows, of which the center is 100 ms Fig.…”

“…A/B is the ratio between the target horizon amplitude and the RMS amplitude from the background strata. Resulted seismic attributes extracted along the target horizons together with well based high-resolution sequence stratigraphy analysis were integrated to identify the biogas entrapment style of the Hsinying gas field (Fuh et al, 2004b(Fuh et al, , 2006. Learning from the comprehensive interpretation of the hydrocarbon entrapment style of the Hsinying gas field, the same entrapment style was recognized for the Kuantian gas fields.…”