ABSTRACT Shallow deltaic thin-bedded (mostly 2–5 m) sandstones of the Upper Miocene Minghuazhen Formation in the Bohai Offshore Basin are among the most significant offshore hydrocarbon reservoirs in China. The prediction of sandstone is essential for breakthroughs in oil and gas exploration. We introduce an enhanced seismic lithology workflow, along with refined seismic methods to unravel the sedimentology. Specifically, within parasequence sets, we establish a quantitative relationship between sand content and seismic amplitude through lithofacies, sedimentary microfacies analysis, and forward modeling. Furthermore, we use common seismic attributes to interpret the thin-bedded lithology and to map the sedimentology. Taking the BZ29 block as an example, we subdivided the lower member of the Minghuazhen Formation into 10 parasequence sets and 6 lithofacies. Based on the selection of 50 samples from representative parasequence sets, we established, through the calculation of sand content, one-dimensional forward modeling and normalization of the amplitude, a strong exponential relationship (coefficient of determination = 0.85) between sand content and amplitude. The interpretations of thin-bedded lithology indicate that shallow deltas are dominated by distributary channel sands, which are potentially good reservoirs, and that the consistency of the sandstone predictions is high. The objectives of our seismic lithology workflow are to establish an intrinsic relationship between sand content and amplitude if the sandstone thickness is less than the tuning thickness, and to use poststack seismic attributes for thin-bedded lithology prediction and sedimentological mapping. Despite certain limitations, this method has promising advantages for the prediction of thin-bedded reservoirs in different depositional environments.
Liu et al. (Wed,) studied this question.